JP3899589B2 - Vehicle control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicle control device in which vehicle running stability can be further improved by utilizing gripping force that can be generated by wheels to the utmost. SOLUTION: In a vehicle control device to control longitudinal force and lateral force generated by each wheel on a road surface to achieve a target running condition of a vehicle, a basic value of a friction circle radius (FR-RL friction circle basic value) expressing the maximum value of resultant force that can be generated is set in accordance with wheel load and tire grip performance (S900-S945), and the basic value is corrected by a road surface friction coefficient (estimated μ) and a wheel ground camber angle to determine the friction circle radius finally estimated value of each wheel (FR-RL friction circle estimated value (S950-S975). The lateral force and the longitudinal force of each wheel are adjusted in the range where the resultant force of the real lateral force and longitudinal force of each wheel is within the estimated value. The force that can be generated by the wheel can be thus utilized to the utmost to set the limit of the vehicle high.

Description

【００７９】
そして、続くＳ５４０にて、上記Ｓ５３５で算出したフロントグリップ力と、４輪荷重演算処理（図３）のＳ１５０，Ｓ１６０で算出したＦＲ輪荷重及びＦＬ輪荷重とから、下記の式１３に基づき、当該車両が現在走行している路面の摩擦係数の推定値である推定μを算出する。
【００８０】
【数１３】
推定μ＝フロントグリップ力／（ＦＲ輪荷重＋ＦＬ輪荷重） …式１３
つまり、Ｓ５４０では、両前輪２FR，２FLのタイヤが発生しているグリップ力（フロントグリップ力）を、両前輪２FR，２FLに加わっている荷重（ＦＲ輪荷重＋ＦＬ輪荷重）で割ることにより、路面の摩擦係数（推定μ）を算出する。
【００８１】
そして、このようにＳ５４０で推定μを算出するか、或いは、上記Ｓ５３０にて前輪限界フラグが「１」ではないと判定した場合には、次にＳ５４５へ進む。このＳ５４５では、後輪限界フラグが「１」であるか否かを判定し、後輪限界フラグが「１」であれば、次のＳ５５０に進んで、前後力演算処理（図５）のＳ３４０で算出したリア前後力と、横力演算処理（図４）のＳ２５０で算出したリア横力とから、下記の式１４に基づき、両後輪２RR，２RLのタイヤの合計のグリップ力であるリアグリップ力を算出する。つまり、リアグリップ力も、フロントグリップ力と同様に、リア前後力とリア横力との合力として算出する。
【００８２】
【数１４】

【００８３】
そして、続くＳ５５５にて、上記Ｓ５５０で算出したリアグリップ力と、４輪荷重演算処理（図３）のＳ１７０，Ｓ１８０で算出したＲＲ輪荷重及びＲＬ輪荷重とから、下記の式１５に基づき、推定μを算出する。
【００８４】
【数１５】
推定μ＝リアグリップ力／（ＲＲ輪荷重＋ＲＬ輪荷重） …式１５
つまり、Ｓ５５５では、前述したＳ５４０及び式１３の場合と同様に、両後輪２RR，２RLのタイヤが発生しているグリップ力（リアグリップ力）を、両後輪２RR，２RLに加わっている荷重（ＲＲ輪荷重＋ＲＬ輪荷重）で割ることにより、路面の摩擦係数（推定μ）を算出する。そして、その後、当該路面μ推定演算処理を終了する。
【００８５】
一方、上記Ｓ５４５にて後輪限界フラグが「１」ではないと判定した場合には、推定μを算出するためのＳ５５０，Ｓ５５５の処理を行うことなく、そのまま当該路面μ推定演算処理を終了する。
このように路面μ推定演算処理では、タイヤのグリップ力が限界であると判定した車輪について、そのタイヤのグリップ力を、そのタイヤに加わっている荷重で割ることにより、路面の摩擦係数（推定μ）を算出するようにしている（Ｓ５３０〜Ｓ５５５）。即ち、タイヤが限界に達している時に発生しているグリップ力を、路面との間の動摩擦力とみなし、その時のグリップ力と荷重との比から、走行路面の摩擦係数を算出している。
【００８６】
そして、ＥＣＵ２０は、この路面μ推定演算処理を終了すると、次に図２のＳ３０へ進み、このＳ３０にて、各車輪２FR，２FL，２RR，２RLのスリップ角（横滑り角度）を算出するための図９に示す４輪横滑り角度演算処理を実行する。
図９に示すように、ＥＣＵ２０が４輪横滑り角度演算処理の実行を開始すると、まずＳ６００，Ｓ６１０にて、車両のヨーレートと横Ｇを入力する。そして、続くＳ６２０にて、車輪速センサ４FR，４FL，４RR，４RLからの信号に基づき検出された車速を入力し、更に続くＳ６３０にて、ステアリング角度センサ１２からの信号に基づき検出されたステアリング角度を入力する。
【００８７】
そして、続くＳ６４０にて、下記の式１６に基づき、車体横滑り角速度を算出する。
【００８８】
【数１６】
車体横滑り角速度＝−横Ｇ／車速＋ヨーレート …式１６
このようにして車体横滑り角速度を算出すると、次のＳ６５０にて、上記算出した車体横滑り角速度を積分することにより、車体の向きと車体の進行方向とのなす角度である車体横滑り角度を算出する。
【００８９】
そして、続くＳ６６０にて、下記の式１７〜式２０に基づき、右前輪２FRのスリップ角であるＦＲ横滑り角度と、左前輪２FLのスリップ角であるＦＬ横滑り角度と、右後輪２RRのスリップ角であるＲＲ横滑り角度と、左後輪２RLのスリップ角であるＲＬ横滑り角度とを、夫々算出する。
【００９０】
尚、式１７〜式２０における「ＦＲトー可変角」，「ＦＬトー可変角」，「ＲＲトー可変角」，「ＲＬトー可変角」は、夫々、トーコントロールアクチュエータ２２FR，２２FL，２２RR，２２RLにより調節された各車輪２FR，２FL，２RR，２RLのトー角である。
【００９１】
【数１７】
ＦＲ横滑り角度＝車体横滑り角度−ヨーレート×重心フロントタイヤ間距離／車速＋ステアリング角度／ギア比＋ＦＲトー可変角 …式１７
【００９２】
【数１８】
ＦＬ横滑り角度＝車体横滑り角度−ヨーレート×重心フロントタイヤ間距離／車速＋ステアリング角度／ギア比＋ＦＬトー可変角 …式１８
【００９３】
【数１９】
ＲＲ横滑り角度＝車体横滑り角度＋ヨーレート×重心リアタイヤ間距離／車速＋ＲＲトー可変角 …式１９
【００９４】
【数２０】
ＲＬ横滑り角度＝車体横滑り角度＋ヨーレート×重心リアタイヤ間距離／車速＋ＲＬトー可変角 …式２０
そして、ＥＣＵ２０は、上記Ｓ６６０で各車輪２FR，２FL，２RR，２RLのスリップ角（横滑り角度）を算出すると、当該４輪横滑り角度演算処理を終了して、次に図２のＳ３５へ進み、このＳ３５にて、タイヤのグリップ性能レベルを判定するための図１０に示すタイヤ種類判定演算処理を実行する。
【００９５】
図１０に示すように、ＥＣＵ２０がタイヤ種類判定演算処理の実行を開始すると、まずＳ７００にて、４輪横滑り角度演算処理（図９）のＳ６６０で算出した各車輪２FR，２FL，２RR，２RLのスリップ角から、下記の式２１，式２２に基づき、前輪２FR，２FLの平均のスリップ角であるフロント横滑り角度と、後輪２RR，２RLの平均のスリップ角であるリア横滑り角度とを算出する。
【００９６】
【数２１】
フロント横滑り角度＝（ＦＲ横滑り角度＋ＦＬ横滑り角度）／２ …式２１
【００９７】
【数２２】
リア横滑り角度＝（ＲＲ横滑り角度＋ＲＬ横滑り角度）／２ …式２２
そして、続くＳ７１０にて、横力演算処理（図４）のＳ２５０で算出したフロント横力と、上記Ｓ７００で算出したフロント横滑り角度とから、下記の式２３に基づき、各前輪２FR，２FLのコーナリングパワーであるフロントコーナリングパワーを算出する。
【００９８】
【数２３】
フロントコーナリングパワー＝フロント横力／２／フロント横滑り角度 …式２３
また同様に、Ｓ７２０にて、横力演算処理（図４）のＳ２５０で算出したリア横力と、上記Ｓ７００で算出したリア横滑り角度とから、下記の式２４に基づき、各後輪２RR，２RLのコーナリングパワーであるリアコーナリングパワーを算出する。
【００９９】
【数２４】
リアコーナリングパワー＝リア横力／２／リア横滑り角度 …式２４
尚、本実施形態では、式２３，式２４からも分かるように、フロント横力とリア横力を夫々「２」で割ることにより、各前輪２FR，２FLの横力と各後輪２RR，２RLの横力を求め、その各横力をコーナリングフォースと近似してコーナリングパワーを求めている。
【０１００】
そして、続くＳ７３０にて、上記Ｓ７００で算出したフロント横滑り角度が所定値Ｓ１よりも小さいか否かを判定し、所定値Ｓ１よりも小さいと判定した場合には、Ｓ７４０に進む。そして、このＳ７４０にて、上記Ｓ７１０で算出したフロントコーナリングパワーが予め設定された設定値ＣＰ１よりも小さいか否かを判定し、フロントコーナリングパワーが設定値ＣＰ１よりも小さいと判定した場合には、Ｓ７５０に進んで、前輪２FR，２FLに装着されたタイヤが低グリップタイヤであるか否かを示すフロント低グリップタイヤフラグに、低グリップタイヤ（つまり、グリップ性能が低いタイヤ）であることを示す「１」をセットする。また逆に、上記Ｓ７４０にて、フロントコーナリングパワーが設定値ＣＰ１よりも小さくないと判定した場合には、Ｓ７６０に移行して、フロント低グリップタイヤフラグに、低グリップタイヤではないこと（換言すれば、グリップ性能が高い高グリップタイヤであること）を示す「０」をセットする。
【０１０１】
尚、Ｓ７３０の判定で用いる所定値Ｓ１は、当該車両に装着される標準的なタイヤにおいてコーナリングフォースとスリップ角とがほぼ比例する領域（タイヤのグリップ力が限界でない領域）内の、所定のスリップ角の値に設定されており、このことは、後述するＳ７７０の判定で用いる所定値Ｓ２についても同様である。
【０１０２】
そして、上記Ｓ７５０及びＳ７６０のうちの何れかを実行して、フロント低グリップタイヤフラグに値をセットすると、Ｓ７７０に進む。また、上記Ｓ７３０にて、フロント横滑り角度が所定値Ｓ１よりも小さくないと判定した場合には、Ｓ７４０〜Ｓ７６０の処理を実行することなくＳ７７０に移行する。
【０１０３】
次にＳ７７０では、今度は、上記Ｓ７００で算出したリア横滑り角度が所定値Ｓ２よりも小さいか否かを判定し、所定値Ｓ２よりも小さいと判定した場合には、Ｓ７８０に進む。そして、このＳ７８０にて、上記Ｓ７２０で算出したリアコーナリングパワーが予め設定された設定値ＣＰ２よりも小さいか否かを判定し、リアコーナリングパワーが設定値ＣＰ２よりも小さいと判定した場合には、Ｓ７９０に進んで、後輪２RR，２RLに装着されたタイヤが低グリップタイヤであるか否かを示すリア低グリップタイヤフラグに、低グリップタイヤであることを示す「１」をセットする。また逆に、上記Ｓ７８０にて、リアコーナリングパワーが設定値ＣＰ２よりも小さくないと判定した場合には、Ｓ７９５に移行して、リア低グリップタイヤフラグに、低グリップタイヤではないこと（換言すれば、高グリップタイヤであること）を示す「０」をセットする。そして、上記Ｓ７９０及びＳ７９５のうちの何れかを実行して、リア低グリップタイヤフラグに値をセットすると、当該タイヤ種類判定演算処理を終了する。
【０１０４】
また、上記Ｓ７７０にて、リア横滑り角度が所定値Ｓ２よりも小さくないと判定した場合には、Ｓ７８０〜Ｓ７９５の処理を実行することなく、そのまま当該タイヤ種類判定演算処理を終了する。
つまり、このタイヤ種類判定演算処理では、タイヤのコーナリングパワーは路面の摩擦係数に関係なくタイヤ自体のグリップ性能に応じた値になるという点に着目し、上記Ｓ７１０，Ｓ７２０で算出したフロントコーナリングパワー及びリアコーナリングパワーの値に応じて、タイヤのグリップ性能の高低を判定するようにしている。
【０１０５】
尚、各前輪２FR，２FLのスリップ角であるフロント横滑り角度が所定値Ｓ１より小さい場合にのみ、前輪タイヤについてのＳ７４０の判定を行い、また、各後輪２RR，２RLのスリップ角であるリア横滑り角度が所定値Ｓ２より小さい場合にのみ、後輪タイヤについてのＳ７８０の判定を行うようにしているのは、フロント・リア横滑り角度が所定値Ｓ１，Ｓ２よりも小さい場合に算出される正確なコーナリングパワーに基づき、タイヤのグリップ性能を判定できるようにするためである。
【０１０６】
次に、ＥＣＵ２０は、このタイヤ種類判定演算処理を終了すると、図２のＳ４０へ進む。そして、このＳ４０にて、各車輪２FR，２FL，２RR，２RLの対地キャンバ角（即ち、車両前方からみてタイヤ中心と地面に垂直な線とのなす角度）を算出するための図１１に示す対地キャンバ角演算処理を実行する。
【０１０７】
図１１に示すように、ＥＣＵ２０が対地キャンバ角演算処理の実行を開始すると、まずＳ８００にて、各ハイトセンサ５FR，５FL，５RR，５RLからの信号に基づき夫々検出された各車輪２FR，２FL，２RR，２RLのハイト（ＦＲハイト，ＦＬハイト，ＲＲハイト，ＲＬハイト）を入力する。
【０１０８】
そして、続くＳ８１０とＳ８２０の各々にて、下記の式２５，式２６に基づき、車体の前輪部におけるロール角であるフロントロール角と、車体の後輪部におけるロール角であるリアロール角とを夫々算出する。尚、式２５における「フロントトレッド」は、左右前輪２FR，２FLの路面との接触面の中心間の車両幅方向の距離であり、式２６における「リアトレッド」は、左右後輪２RR，２RLの路面との接触面の中心間の車両幅方向の距離である。
【０１０９】
【数２５】
フロントロール角＝ｔａｎ^-1（（ＦＲハイト−ＦＬハイト）／フロントトレッド） …式２５
【０１１０】
【数２６】
リアロール角＝ｔａｎ^-1（（ＲＲハイト−ＲＬハイト）／リアトレッド） …式２６
次にＳ８３０にて、ＲＯＭから「ハイト対キャンバ角変化量マップ」を読み込む。この「ハイト対キャンバ角変化量マップ」は、図１２に示すように、ハイトセンサ５FR，５FL，５RR，５RLにより検出されるハイトに対する車輪のキャンバ角の変化量（キャンバ角変化量）を記憶したデータマップであり、各車輪２FR，２FL，２RR，２RL毎に用意されている。
【０１１１】
そして、続くＳ８４０にて、上記Ｓ８００で入力した各車輪２FR，２FL，２RR，２RLのハイトに対応する、各車輪２FR，２FL，２RR，２RLのキャンバ角変化量（ＦＲキャンバ角変化量，ＦＬキャンバ角変化量，ＲＲキャンバ角変化量，ＲＬキャンバ角変化量）を、上記Ｓ８３０で読み込んだ「ハイト対キャンバ角変化量マップ」に基づき、補間演算などにより算出する。
【０１１２】
そして更に、続くＳ８５０〜Ｓ８８０の各々にて、下記の式２７〜式３０に基づき、各車輪２FR，２FL，２RR，２RLの実際の対地キャンバ角（ＦＲ対地キャンバ角，ＦＬ対地キャンバ角，ＲＲ対地キャンバ角，ＲＬ対地キャンバ角）を算出し、その後、当該対地キャンバ角演算処理を終了する。
【０１１３】
尚、式２７〜式３０における「ＦＲキャンバ角制御量」，「ＦＬキャンバ角制御量」，「ＲＲキャンバ角制御量」，及び「ＲＬキャンバ角制御量」は、夫々、キャンバコントロールアクチュエータ２４FR，２４FL，２４RR，２４RLにより調節された各車輪２FR，２FL，２RR，２RLのキャンバ角の変化分である。
【０１１４】
【数２７】
ＦＲ対地キャンバ角＝ＦＲキャンバ角変化量＋フロントロール角＋ＦＲキャンバ角制御量 …式２７
【０１１５】
【数２８】
ＦＬ対地キャンバ角＝ＦＬキャンバ角変化量−フロントロール角＋ＦＬキャンバ角制御量 …式２８
【０１１６】
【数２９】
ＲＲ対地キャンバ角＝ＲＲキャンバ角変化量＋リアロール角＋ＲＲキャンバ角制御量 …式２９
【０１１７】
【数３０】
ＲＬ対地キャンバ角＝ＲＬキャンバ角変化量−リアロール角＋ＲＬキャンバ角制御量 …式３０
つまり、Ｓ８５０〜Ｓ８８０では、サスペンションのストローク変化に起因するキャンバ角の変化分（ＦＲ〜ＲＬキャンバ角変化量）と、車体のローリングに起因するキャンバ角の変化分（フロントロール角，リアロール角）と、キャンバコントロールアクチュエータ２４FR，２４FL，２４RR，２４RLにより調節されているキャンバ角の変化分（ＦＲ〜ＲＬキャンバ角制御量）とから、各車輪２FR，２FL，２RR，２RLの実際の対地キャンバ角（ＦＲ〜ＲＬ対地キャンバ角）を算出している。
【０１１８】
そして、ＥＣＵ２０は、この対地キャンバ角演算処理を終了すると、次に図２のＳ４５へ進み、このＳ４５にて、図１３に示す４輪摩擦円推定演算処理を実行する。
この４輪摩擦円推定演算処理は、各車輪２FR，２FL，２RR，２RLが路面との間で夫々発生することのできる力の合力の最大値を、摩擦円の半径として設定するための処理である。
【０１１９】
図１３に示すように、ＥＣＵ２０が４輪摩擦円推定演算処理の実行を開始すると、まずＳ９００にて、図１０のタイヤ種類判定演算処理で値がセットされたフロント低グリップタイヤフラグが「１」であるか否かを判定する。そして、フロント低グリップタイヤフラグが「１」であると判定した場合には、Ｓ９０５に進んで、ＲＯＭから「低グリップタイヤ用の荷重対摩擦円マップ」を読み込む。また、上記Ｓ９００にてフロント低グリップタイヤフラグが「１」ではないと判定した場合には、Ｓ９１０に移行して、ＲＯＭから「高グリップタイヤ用の荷重対摩擦円マップ」を読み込む。
【０１２０】
ここで、Ｓ９１０で読み込む「高グリップタイヤ用の荷重対摩擦円マップ」は、図１４の実線で示すように、当該車両に装着される標準的なタイヤについて、荷重に対する摩擦円の半径の大きさ（即ち、発生可能な最大グリップ力の大きさ）を記憶したデータマップであり、荷重が大きくなるほど、摩擦円半径も大きくなるように設定されている。また同様に、Ｓ９０５で読み込む「低グリップタイヤ用の荷重対摩擦円マップ」は、図１４の一点鎖線で示すように、標準的なタイヤよりもグリップ性能が低いタイヤ（例えば、冬季用のスタッドレスタイヤ）について、荷重に対する摩擦円の半径の大きさを記憶したデータマップである。
【０１２１】
そして、図１４から分かるように、「高グリップタイヤ用の荷重対摩擦円マップ」と「低グリップタイヤ用の荷重対摩擦円マップ」とで、同じ値の荷重に対応する摩擦円半径の値は、「低グリップタイヤ用の荷重対摩擦円マップ」の方が小さく設定されている。
【０１２２】
次に、上記Ｓ９０５，Ｓ９１０のうちの何れかを実行した後、Ｓ９１５に移行して、図３の４輪荷重演算処理で算出したＦＲ輪荷重（右前輪２FRの荷重）とＦＬ輪荷重（左前輪２FLの荷重）を読み込む。
そして、続くＳ９２０にて、上記読み込んだＦＲ輪荷重とＦＬ輪荷重とに夫々対応する摩擦円半径を、Ｓ９０５，Ｓ９１０の何れかで読み込んだデータマップ（「低グリップタイヤ用の荷重対摩擦円マップ」或いは「高グリップタイヤ用の荷重対摩擦円マップ」）に基づき、補間演算などにより算出し、その算出した右前輪２FRに対応する摩擦円半径と左前輪２FLに対応する摩擦円半径とを、夫々、ＦＲ摩擦円基本値とＦＬ摩擦円基本値として設定する。
【０１２３】
次にＳ９２５へ進み、今度は、図１０のタイヤ種類判定演算処理で値がセットされたリア低グリップタイヤフラグが「１」であるか否かを判定する。そして、リア低グリップタイヤフラグが「１」であると判定した場合には、Ｓ９３０に進んで、前述したＳ９０５の場合と同様に、ＲＯＭから「低グリップタイヤ用の荷重対摩擦円マップ」を読み込む。また、上記Ｓ９２５にてリア低グリップタイヤフラグが「１」ではないと判定した場合には、Ｓ９３５に移行して、前述したＳ９１０の場合と同様に、ＲＯＭから「高グリップタイヤ用の荷重対摩擦円マップ」を読み込む。
【０１２４】
そして、上記Ｓ９３０，Ｓ９３５のうちの何れかを実行した後、Ｓ９４０に移行して、図３の４輪荷重演算処理で算出したＲＲ輪荷重（右後輪２RRの荷重）とＲＬ輪荷重（左後輪２RLの荷重）を読み込み、続くＳ９４５にて、上記読み込んだＲＲ輪荷重とＲＬ輪荷重とに夫々対応する摩擦円半径を、Ｓ９３０，Ｓ９３５の何れかで読み込んだデータマップに基づき、補間演算などにより算出する。そして、その算出した右後輪２RRに対応する摩擦円半径と左後輪２RLに対応する摩擦円半径とを、夫々、ＲＲ摩擦円基本値とＲＬ摩擦円基本値として設定する。
【０１２５】
このようにして各車輪２FR，２FL，２RR，２RLの摩擦円基本値（ＦＲ〜ＲＬ摩擦円基本値）を求めると、次にＳ９５０へ進み、図７及び図８の路面μ推定演算処理で算出した最新の推定μ（路面の摩擦係数の推定値）を読み込む。
そして、続くＳ９５５にて、下記の式３１〜式３４に基づき、各摩擦円基本値の推定μによる補正値である、ＦＲ摩擦円μ補正値と、ＦＬ摩擦円μ補正値と、ＲＲ摩擦円μ補正値と、ＲＬ摩擦円μ補正値とを夫々算出する。
【０１２６】
【数３１】
ＦＲ摩擦円μ補正値＝ＦＲ摩擦円基本値×推定μ …式３１
【０１２７】
【数３２】
ＦＬ摩擦円μ補正値＝ＦＬ摩擦円基本値×推定μ …式３２
【０１２８】
【数３３】
ＲＲ摩擦円μ補正値＝ＲＲ摩擦円基本値×推定μ …式３３
【０１２９】
【数３４】
ＲＬ摩擦円μ補正値＝ＲＬ摩擦円基本値×推定μ …式３４
次に、続くＳ９６０にて、ＲＯＭから「対地キャンバ角対摩擦円減少係数マップ」を読み込む。この「対地キャンバ角対摩擦円減少係数マップ」は、図１５に示すように、車輪の対地キャンバ角と、摩擦円の半径を減少補正するための係数である摩擦円減少係数との関係を記憶したデータマップである。そして、対地キャンバ角が０度の場合（つまり、タイヤが路面に対して垂直である場合）に、摩擦円減少係数が最大の「１」となり、対地キャンバ角が０度から離れるほど（つまり、タイヤが路面に対して傾くほど）、摩擦円減少係数が小さくなるように設定されている。
【０１３０】
そして、続くＳ９６５にて、図１１の対地キャンバ角演算処理で算出した各車輪２FR，２FL，２RR，２RLの対地キャンバ角（ＦＲ対地キャンバ角，ＦＬ対地キャンバ角，ＲＲ対地キャンバ角，ＲＬ対地キャンバ角）を読み込み、続くＳ９７０にて、各車輪２FR，２FL，２RR，２RLの対地キャンバ角に夫々対応する摩擦円減少係数（ＦＲ摩擦円減少係数，ＦＬ摩擦円減少係数，ＲＲ摩擦円減少係数，ＲＬ摩擦円減少係数）を、上記Ｓ９６０で読み込んだ「対地キャンバ角対摩擦円減少係数マップ」に基づき、補間演算などにより算出する。
【０１３１】
そして更に、続くＳ９７５にて、下記の式３５〜式３８に基づき、各車輪２FR，２FL，２RR，２RLの実際の摩擦円半径の推定値である、ＦＲ摩擦円推定値と、ＦＬ摩擦円推定値と、ＲＲ摩擦円推定値と、ＲＬ摩擦円推定値とを夫々算出し、その後、当該４輪摩擦円推定演算処理を終了する。
【０１３２】
【数３５】
ＦＲ摩擦円推定値＝ＦＲ摩擦円μ補正値×ＦＲ摩擦円減少係数 …式３５
【０１３３】
【数３６】
ＦＬ摩擦円推定値＝ＦＬ摩擦円μ補正値×ＦＬ摩擦円減少係数 …式３６
【０１３４】
【数３７】
ＲＲ摩擦円推定値＝ＲＲ摩擦円μ補正値×ＲＲ摩擦円減少係数 …式３７
【０１３５】
【数３８】
ＲＬ摩擦円推定値＝ＲＬ摩擦円μ補正値×ＲＬ摩擦円減少係数 …式３８
つまり、この４輪摩擦円推定演算処理では、各車輪２FR，２FL，２RR，２RLについて、荷重から考えられる基本の摩擦円半径である摩擦円基本値に、路面摩擦係数の推定値である推定μと、対地キャンバ角に応じた補正係数である摩擦円減少係数とを乗じることにより、摩擦円半径の最終的な推定値である摩擦円推定値（ＦＲ〜ＲＬ摩擦円推定値）を算出している。そして、各車輪２FR，２FL，２RR，２RLの摩擦円推定値は、車輪の荷重が大きいほど、車輪の対地キャンバ角が０度に近いほど、推定μが大きいほど、タイヤのグリップ性能レベルが高いほど、大きい値に設定される。
【０１３６】
次に、ＥＣＵ２０は、４輪摩擦円推定演算処理を終了すると、図２のＳ５０へ進み、このＳ５０にて、図１６に示す目標走行状態設定処理を実行する。
この目標走行状態設定処理は、運転者の操作に応じて車体に発生すべき目標の運動物理量である目標ヨーレート，目標横Ｇ，及び目標前後Ｇを算出すると共に、それらによって得られる目標の走行状態を実現するために必要な、車体横力の目標値である目標車体横力と、フロント横力の目標値であるフロント目標横力と、リア横力の目標値であるリア目標横力と、車体前後力の目標値である目標車体前後力とを算出するための処理である。
【０１３７】
そして、図１６に示すように、ＥＣＵ２０が目標走行状態設定処理の実行を開始すると、まずＳ１０００にて、図１７の目標横力演算処理を実行する。
即ち、目標横力演算処理では、図１７に示すように、まずＳ１００５にて、ステアリング角度センサ１２からの信号に基づき検出されたステアリング角度を入力し、続くＳ１０１０にて、車輪速センサ４FR，４FL，４RR，４RLからの信号に基づき検出された車速を入力する。そして、続くＳ１０１５にて、前輪２FR，２FLに対する仮想的なトー角の補正量を示す変数であるＦトー角補正量に、初期値としての「０」をセットする。
【０１３８】
次にＳ１０２０にて、下記の式３９に基づき、ステアリング角度補正量を算出する。尚、式３９における「−Ｆトー角補正量」の項は、前輪２FR，２FLのトー角をＦトー角補正量の分だけ中心位置へ戻す方向（以下、この方向を切り戻し方向といい、また、それと反対の方向を切り増し方向という）に補正することを示している。つまり、ステアリング角度補正量とは、ステアリングの操作によって生じる前輪２FR，２FLの実際のトー角（＝ステアリング角度／ギア比）を、Ｆトー角補正量だけ切り戻し方向に補正した値である。
【０１３９】
【数３９】
ステアリング角度補正量＝ステアリング角度／ギア比−Ｆトー角補正量 …式３９
そして、続くＳ１０２５にて、下記の式４０に基づき、上記算出したステアリング角度補正量を用いて目標ヨーレートを算出し、更に続くＳ１０３０にて、上記Ｓ１０２５で算出した目標ヨーレートに車速を乗じることにより、目標横Ｇ（＝目標ヨーレート×車速）を算出する。
【０１４０】
【数４０】
目標ヨーレート＝（ステアリング角度補正量×車速／ホイルベース）／（１＋目標スタビリティファクタ×車速×車速） …式４０
このようにして目標ヨーレートと目標横Ｇを算出すると、次にＳ１０３５にて、上記Ｓ１０２５で算出した目標ヨーレートを微分することにより、車体の目標ヨー角加速度を算出し、更に続くＳ１０４０にて、上記算出した目標ヨー角加速度にモーメント定数を乗じることにより、車体の目標ヨーモーメント（＝目標ヨー角加速度×モーメント定数）を算出する。また続くＳ１０４５にて、上記Ｓ１０３０で算出した目標横Ｇに車重を乗じることにより、目標車体横力（＝目標横Ｇ×車重）を算出する。
【０１４１】
そして、続くＳ１０５０にて、下記の式４１，式４２に基づき、Ｓ１０２５とＳ１０３０で算出した目標ヨーレート及び目標横Ｇを実現するために必要なフロント目標横力とリア目標横力とを算出する。
【０１４２】
【数４１】
フロント目標横力＝（目標車体横力×重心リアタイヤ間距離＋目標ヨーモーメント）／ホイルベース …式４１
【０１４３】
【数４２】
リア目標横力＝（目標車体横力×重心フロントタイヤ間距離−目標ヨーモーメント）／ホイルベース …式４２
このようにしてフロント目標横力とリア目標横力を算出すると、次にＳ１０５５へ進み、図１３の４輪摩擦円推定演算処理で算出した各車輪２FR，２FL，２RR，２RLの摩擦円推定値（ＦＲ〜ＲＬ摩擦円推定値）を読み出す。そして、下記の式４３，式４４に基づき、両前輪２FR，２FLが発生可能な合計の最大グリップ力を表すフロント摩擦円限界値と、両後輪２RR，２RLが発生可能な合計の最大グリップ力を表すリア摩擦円限界値とを算出する。
【０１４４】
【数４３】
フロント摩擦円限界値＝ＦＲ摩擦円推定値＋ＦＬ摩擦円推定値 …式４３
【０１４５】
【数４４】
リア摩擦円限界値＝ＲＲ摩擦円推定値＋ＲＬ摩擦円推定値 …式４４
そして、続くＳ１０６０にて、上記算出したフロント摩擦円限界値がＳ１０５０で算出したフロント目標横力よりも大きいか否かを判定し、フロント摩擦円限界値の方が大きければ、両前輪２FR，２FLがフロント目標横力を発生可能であると判断して、次のＳ１０６５へ進む。Ｓ１０６５では、今度は、上記Ｓ１０５５で算出したリア摩擦円限界値がＳ１０５０で算出したリア目標横力よりも大きいか否かを判定し、リア摩擦円限界値の方が大きければ、両後輪２RR，２RLがリア目標横力を発生可能であると判断して、当該目標横力演算処理を終了する。
【０１４６】
一方、上記Ｓ１０６０にて、フロント摩擦円限界値がフロント目標横力よりも大きくないと判定した場合、或いは、上記Ｓ１０６５にて、リア摩擦円限界値がリア目標横力よりも大きくないと判定した場合には、フロント目標横力或いはリア目標横力を発生させることが不能であり、上記Ｓ１０２５とＳ１０３０で算出した目標ヨーレート及び目標横Ｇが大き過ぎると判断して、Ｓ１０７０に移行する。そして、このＳ１０７０にて、現在のＦトー角補正量に所定値Ｋ８を加えた値を、新たなＦトー角補正量として設定し、その後、Ｓ１０２０以降の処理を繰り返す。
【０１４７】
このため、当該目標横力演算処理では、Ｓ１０６０或いはＳ１０６５で否定判定される度に、ステアリング角度補正量が切り戻し方向に補正されて、目標ヨーレート及び目標横Ｇが絶対値の小さい値に修正される。そして、フロント摩擦円限界値とリア摩擦円限界値とにより達成可能なフロント目標横力とリア目標横力とが設定されることとなる。
【０１４８】
尚、Ｓ１０２０以降の処理が最初に実行されたとき（即ち、Ｆトー角補正量が「０」のとき）に、Ｓ１０６０及びＳ１０６５で肯定判定された場合には、Ｓ１０２５とＳ１０３０で算出される目標ヨーレート及び目標横Ｇは、図７の路面μ推定演算処理で算出された目標ヨーレート及び目標横Ｇと同じ値となり、その目標ヨーレート及び目標横Ｇを実現するのに必要なフロント横力とリア横力とが、夫々、フロント目標横力とリア目標横力として設定されることとなる。
【０１４９】
こうして図１７の目標横力演算処理が終了すると、図１６に示すように、目標走行状態設定処理では、次にＳ１１００へ進んで、図１８の目標前後力演算処理を実行する。
即ち、目標前後力演算処理では、図１８に示すように、まずＳ１１１０にて、アクセル開度センサ１８からの信号に基づき検出されたアクセル開度を入力し、続くＳ１１２０にて、上記入力したアクセル開度を微分するすることにより、アクセル開度の変化速度であるアクセル速度を算出する。
【０１５０】
そして、続くＳ１１３０にて、ＲＯＭから「アクセル状態対目標前後Ｇマップ」を読み込む。尚、この「アクセル状態対目標前後Ｇマップ」は、図１９に示すように、アクセル開度とアクセル速度と車体の目標前後Ｇとの関係を記憶した３次元のデータマップである。そして更に、続くＳ１１４０にて、上記Ｓ１１１０で入力した実際のアクセル開度とＳ１１２０で算出したアクセル速度とに対応する車体の目標前後Ｇを、「アクセル状態対目標前後Ｇマップ」に基づき算出し、その算出した目標前後Ｇを、第１の目標前後Ｇ１として記憶する。
【０１５１】
次にＳ１１５０にて、ブレーキ踏力センサ１６からの信号に基づき検出されたブレーキ踏力を入力し、続くＳ１１６０にて、ＲＯＭから「ブレーキ踏力対目標前後Ｇマップ」を読み込む。尚、この「ブレーキ踏力対目標前後Ｇマップ」は、図２０に示すように、ブレーキ踏力と車体の目標前後Ｇとの関係を記憶したデータマップである。そして更に、続くＳ１１７０にて、上記Ｓ１１５０で入力した実際のブレーキ踏力に対応する車体の目標前後Ｇを、「ブレーキ踏力対目標前後Ｇマップ」に基づき算出し、その算出した目標前後Ｇを、第２の目標前後Ｇ２として記憶する。
【０１５２】
そして、続くＳ１１８０にて、アクセル開度及びアクセル速度に基づく第１の目標前後Ｇ１と、ブレーキ踏力に基づく第２の目標前後Ｇ２とを加算して、最終的な車体の目標前後Ｇ（＝目標前後Ｇ１＋目標前後Ｇ２）を算出し、次のＳ１１９０にて、上記Ｓ１１８０で算出した最終的な目標前後Ｇに車重を乗じることにより、その目標前後Ｇを実現するために必要な目標車体前後力（＝目標前後Ｇ×車重）を算出する。
【０１５３】
このように目標車体前後力を算出した後、当該目標前後力演算処理を終了し、これにより図１６の目標走行状態設定処理も終了する。
そして、ＥＣＵ２０は、目標走行状態設定処理を終了すると、次に図２のＳ５５へ進み、このＳ５５にて、図２１に示す追加力演算処理を実行する。
【０１５４】
この追加力演算処理は、図１６の目標走行状態設定処理で算出した目標ヨーレート，目標横Ｇ，及び目標前後Ｇを実現するために車輪が発生しなければならない力の追加分（正の追加分或いは負の追加分）を算出するための処理である。
図２１に示すように、ＥＣＵ２０が追加力演算処理の実行を開始すると、まずＳ１２００にて、図１６の目標走行状態設定処理（詳しくは、図１７の目標横力演算処理）で算出したフロント目標横力を入力し、続くＳ１２１０にて、図４の横力演算処理で算出した実際のフロント横力を入力する。
【０１５５】
次にＳ１２２０にて、図１６の目標走行状態設定処理（詳しくは、図１７の目標横力演算処理）で算出したリア目標横力を入力し、続くＳ１２３０にて、図４の横力演算処理で算出した実際のリア横力を入力する。
そして、続くＳ１２４０にて、下記の式４５に示す如く、フロント目標横力から実際のフロント横力を引くことにより、目標ヨーレート及び目標横Ｇを実現するために両前輪２FR，２FLが追加して発生しなければならない合計の横力であるフロント追加横力を算出する。
【０１５６】
そして更に、下記の式４６に示す如く、リア目標横力から実際のリア横力を引くことにより、目標ヨーレート及び目標横Ｇを実現するために両後輪２RR，２RLが追加して発生しなければならない合計の横力であるリア追加横力を算出する。
【０１５７】
【数４５】
フロント追加横力＝フロント目標横力−フロント横力 …式４５
【０１５８】
【数４６】
リア追加横力＝リア目標横力−リア横力 …式４６
次にＳ１２５０にて、図１６の目標走行状態設定処理（詳しくは、図１８の目標前後力演算処理）で算出した目標車体前後力を入力し、続くＳ１２６０にて、図５の前後力演算処理で算出した実際の車体前後力を入力する。
【０１５９】
そして、続くＳ１２７０にて、下記の式４７に示す如く、目標車体前後力から実際の車体前後力を引くことにより、目標前後Ｇを実現するために４輪２FR，２FL，２RR，２RLが追加して発生しなければならない合計の前後力である追加車体前後力を算出し、その後、当該追加力演算処理を終了する。
【０１６０】
【数４７】
追加車体前後力＝目標車体前後力−車体前後力 …式４７
そして、ＥＣＵ２０は、追加力演算処理を終了すると、次に図２のＳ６０へ進み、このＳ６０にて、図２２及び図２３に示す摩擦円余裕演算処理を実行する。尚、図２２は摩擦円余裕演算処理の前半部を表しており、図２３はその後半部を表している。
【０１６１】
この摩擦円余裕演算処理は、図１３の４輪摩擦円推定演算処理で算出したＦＲ〜ＲＬ摩擦円推定値に基づき、各車輪２FR，２FL，２RR，２RLが追加して発生可能な横力の余裕度（余裕分の力）を算出するための処理である。
図２２に示すように、ＥＣＵ２０が摩擦円余裕演算処理の実行を開始すると、まずＳ１３００にて、図１３の４輪摩擦円推定演算処理で算出したＦＲ摩擦円推定値と、図５の前後力演算処理で算出した実際のフロント前後力と、図４の横力演算処理で算出した実際のフロント横力とを読み出す。
【０１６２】
そして、下記の式４８に基づき、右前輪２FRが現在発生している横力と同方向に追加して発生可能な右前輪２FRの横力の余裕度であるＦＲ横力正追加限界値１を算出し、更に、下記の式４９に基づき、右前輪２FRが現在発生している横力と逆方向に追加して発生可能な右前輪２FRの横力の余裕度であるＦＲ横力負追加限界値を算出する。
【０１６３】
【数４８】

【０１６４】
【数４９】

【０１６５】
つまり、Ｓ１３００では、実際のフロント前後力とフロント横力を夫々２で割った値を、右前輪２FRの実際の前後力（＝フロント前後力／２）及び実際の横力（＝フロント横力／２）と見なし、その実際の前後力との合力が右前輪２FRの摩擦円半径であるＦＲ摩擦円推定値と等しくなる横力の値（＝式４８及び式４９の前項）から実際の横力を引くことにより、実際の横力と同方向に追加して発生可能な横力の余裕度であるＦＲ横力正追加限界値１を求め、また、実際の前後力との合力がＦＲ摩擦円推定値と等しくなる横力の値に実際の横力を加算することにより、実際の横力と逆方向に追加して発生可能な横力の余裕度であるＦＲ横力負追加限界値を求めている。
【０１６６】
次に、続くＳ１３０５にて、図１３の４輪摩擦円推定演算処理で算出したＦＬ摩擦円推定値と、図５の前後力演算処理で算出した実際のフロント前後力と、図４の横力演算処理で算出した実際のフロント横力とを読み出す。
そして、上記Ｓ１３００の場合と全く同様に、下記の式５０に基づき、左前輪２FLが現在発生している横力と同方向に追加して発生可能な左前輪２FLの横力の余裕度であるＦＬ横力正追加限界値１を算出し、更に、下記の式５１に基づき、左前輪２FLが現在発生している横力と逆方向に追加して発生可能な左前輪２FLの横力の余裕度であるＦＬ横力負追加限界値を算出する。
【０１６７】
【数５０】

【０１６８】
【数５１】

【０１６９】
そして、続くＳ１３１０にて、上記Ｓ１３０５で算出したＦＬ横力正追加限界値１が「０」よりも小さいか否かを判定し、「０」よりも小さくない場合には、Ｓ１３１５に進んで、上記Ｓ１３００で算出したＦＲ横力正追加限界値１を、右前輪２FRが現在発生している横力と同方向に追加して発生可能な右前輪２FRの横力の真の余裕度であるＦＲ横力正追加限界値として記憶する。
【０１７０】
これに対し、上記Ｓ１３１０にて、ＦＬ横力正追加限界値１が「０」よりも小さいと判定した場合（即ち、ＦＬ横力正追加限界値１が負の場合）には、Ｓ１３２０に移行して、上記Ｓ１３００で算出したＦＲ横力正追加限界値１に負の値であるＦＬ横力正追加限界値１を加算した値を、ＦＲ横力正追加限界値として記憶する。
【０１７１】
つまり、ＦＬ横力正追加限界値１が負であるということは、左前輪２FLの計算上の実際の前後力（＝フロント前後力／２）と横力（＝フロント横力／２）との合力が、ＦＬ横力正追加限界値１の絶対値の分だけＦＬ摩擦円推定値を越えてしまっていることを示しているが、実際には、両前輪２FR，２FLが同じ量の横力を発生しているのではなく、左前輪２FLよりも右前輪２FRの方が、ＦＬ横力正追加限界値１の絶対値の分だけ横力を多く発生していると見なされる。そこで、Ｓ１３２０にて、右前輪２FRの横力の余裕度を、ＦＬ横力正追加限界値１の絶対値の分だけ減らしているのである。
【０１７２】
そして、上記Ｓ１３１５或いはＳ１３２０でＦＲ横力正追加限界値を記憶した後、Ｓ１３２５に移行して、その記憶したＦＲ横力正追加限界値が「０」よりも小さいか否かを判定する。そして、ＦＲ横力正追加限界値が「０」よりも小さくなければ、そのままＳ１３３５へ進むが、ＦＲ横力正追加限界値が「０」よりも小さければ、右前輪２FRにはもはや横力を追加して発生することができないと判断し、Ｓ１３３０にて、ＦＲ横力正追加限界値を「０」に設定した後、Ｓ１３３５へ進む。
【０１７３】
そして、次にＳ１３３５〜Ｓ１３５５にて、左前輪２FLに関し、前述したＳ１３１０〜Ｓ１３３０と全く同様の処理を行う。
即ち、まずＳ１３３５にて、上記Ｓ１３００で算出したＦＲ横力正追加限界値１が「０」よりも小さいか否かを判定し、「０」よりも小さくない場合には、Ｓ１３４０に進んで、上記Ｓ１３０５で算出したＦＬ横力正追加限界値１を、左前輪２FLが現在発生している横力と同方向に追加して発生可能な左前輪２FLの横力の真の余裕度であるＦＬ横力正追加限界値として記憶する。
【０１７４】
これに対し、上記Ｓ１３３５にて、ＦＲ横力正追加限界値１が「０」よりも小さいと判定した場合には、Ｓ１３４５に移行して、上記Ｓ１３０５で算出したＦＬ横力正追加限界値１に負の値であるＦＲ横力正追加限界値１を加算した値を、ＦＬ横力正追加限界値として記憶する。つまり、この場合には、前述したＳ１３２０の場合とは逆に、右前輪２FRよりも左前輪２FLの方が、ＦＲ横力正追加限界値１の絶対値の分だけ横力を多く発生していると見なし、左前輪２FLの横力の余裕度を、ＦＲ横力正追加限界値１の絶対値の分だけ減らしている。
【０１７５】
そして、上記Ｓ１３４０或いはＳ１３４５でＦＬ横力正追加限界値を記憶した後、Ｓ１３５０に移行して、その記憶したＦＬ横力正追加限界値が「０」よりも小さいか否かを判定する。そして、ＦＬ横力正追加限界値が「０」よりも小さくなければ、そのまま図２３のＳ１３６０へ進むが、ＦＬ横力正追加限界値が「０」よりも小さければ、左前輪２FLにはもはや横力を追加して発生することができないと判断し、Ｓ１３５５にて、ＦＬ横力正追加限界値を「０」に設定した後、図２３のＳ１３６０へ進む。
【０１７６】
次に、図２３に示すＳ１３６０〜Ｓ１４１５の処理では、右後輪２RRと左後輪２RLとの各々に関して、前述した図２２のＳ１３００〜Ｓ１３５５と全く同様の処理を行う。
即ち、まずＳ１３６０にて、図１３の４輪摩擦円推定演算処理で算出したＲＲ摩擦円推定値と、図５の前後力演算処理で算出した実際のリア前後力と、図４の横力演算処理で算出した実際のリア横力とを読み出す。そして、下記の式５２に基づき、右後輪２RRが現在発生している横力と同方向に追加して発生可能な右後輪２RRの横力の余裕度であるＲＲ横力正追加限界値１を算出し、更に、下記の式５３に基づき、右後輪２RRが現在発生している横力と逆方向に追加して発生可能な右後輪２RRの横力の余裕度であるＲＲ横力負追加限界値を算出する。
【０１７７】
【数５２】

【０１７８】
【数５３】

【０１７９】
次に、続くＳ１３６５にて、図１３の４輪摩擦円推定演算処理で算出したＲＬ摩擦円推定値と、図５の前後力演算処理で算出した実際のリア前後力と、図４の横力演算処理で算出した実際のリア横力とを読み出す。そして、下記の式５４に基づき、左後輪２RLが現在発生している横力と同方向に追加して発生可能な左後輪２RLの横力の余裕度であるＲＬ横力正追加限界値１を算出し、更に、下記の式５５に基づき、左後輪２RLが現在発生している横力と逆方向に追加して発生可能な左後輪２RLの横力の余裕度であるＲＬ横力負追加限界値を算出する。
【０１８０】
【数５４】

【０１８１】
【数５５】

【０１８２】
つまり、Ｓ１３６０及びＳ１３６５では、実際のリア前後力とリア横力を夫々２で割った値を、後輪２RR，２RLの各々が実際に発生している前後力（＝リア前後力／２）及び横力（＝リア横力／２）と見なして、図２２のＳ１３００及びＳ１３０５と同様の手順により、ＲＲ横力正追加限界値１，ＲＲ横力負追加限界値，ＲＬ横力正追加限界値１，及びＲＬ横力負追加限界値を求めている。
【０１８３】
そして、続くＳ１３７０にて、上記Ｓ１３６５で算出したＲＬ横力正追加限界値１が「０」よりも小さいか否かを判定し、「０」よりも小さくない場合には、Ｓ１３７５に進んで、上記Ｓ１３６０で算出したＲＲ横力正追加限界値１を、右後輪２RRが現在発生している横力と同方向に追加して発生可能な右後輪２RRの横力の真の余裕度であるＲＲ横力正追加限界値として記憶する。
【０１８４】
これに対し、上記Ｓ１３７０にて、ＲＬ横力正追加限界値１が「０」よりも小さいと判定した場合には、Ｓ１３８０に移行して、上記Ｓ１３６０で算出したＲＲ横力正追加限界値１に負の値であるＲＬ横力正追加限界値１を加算した値を、ＲＲ横力正追加限界値として記憶する。
【０１８５】
そして、上記Ｓ１３７５或いはＳ１３８０でＲＲ横力正追加限界値を記憶した後、Ｓ１３８５に移行して、その記憶したＲＲ横力正追加限界値が「０」よりも小さいか否かを判定する。そして、ＲＲ横力正追加限界値が「０」よりも小さくなければ、そのままＳ１３９５へ進むが、ＲＲ横力正追加限界値が「０」よりも小さければ、右後輪２RRにはもはや横力を追加して発生することができないと判断し、Ｓ１３９０にて、ＲＲ横力正追加限界値を「０」に設定した後、Ｓ１３９５へ進む。
【０１８６】
次にＳ１３９５では、上記Ｓ１３６０で算出したＲＲ横力正追加限界値１が「０」よりも小さいか否かを判定し、「０」よりも小さくない場合には、Ｓ１４００に進んで、上記Ｓ１３６５で算出したＲＬ横力正追加限界値１を、左後輪２RLが現在発生している横力と同方向に追加して発生可能な左後輪２RLの横力の真の余裕度であるＲＬ横力正追加限界値として記憶する。
【０１８７】
これに対し、上記Ｓ１３９５にて、ＲＲ横力正追加限界値１が「０」よりも小さいと判定した場合には、Ｓ１４０５に移行して、上記Ｓ１３６５で算出したＲＬ横力正追加限界値１に負の値であるＲＲ横力正追加限界値１を加算した値を、ＲＬ横力正追加限界値として記憶する。
【０１８８】
そして、上記Ｓ１４００或いはＳ１４０５でＲＬ横力正追加限界値を記憶した後、Ｓ１４１０に移行して、その記憶したＲＬ横力正追加限界値が「０」よりも小さいか否かを判定する。そして、ＲＬ横力正追加限界値が「０」よりも小さくなければ、そのまま当該摩擦円余裕演算処理を終了するが、ＲＬ横力正追加限界値が「０」よりも小さければ、左後輪２RLにはもはや横力を追加して発生することができないと判断し、Ｓ１４１５にて、ＲＬ横力正追加限界値を「０」に設定した後、当該摩擦円余裕演算処理を終了する。
【０１８９】
こうして摩擦円余裕演算処理の実行を終了すると、次に図２のＳ６５へ進み、このＳ６５にて、図２４に示す追加力配分処理を実行する。
この追加力配分処理は、図２１の追加力演算処理で算出したフロント追加横力，リア追加横力，及び追加車体前後力を、４輪のタイヤのグリップ力が限界を越えないように各車輪２FR，２FL，２RR，２RLへ配分するための処理である。
【０１９０】
そして、図２４に示すように、ＥＣＵ２０が追加力配分処理の実行を開始すると、まずＳ１５００にて、図２５の追加横力配分演算処理を実行する。
即ち、追加横力配分演算処理では、図２５に示すように、まずＳ１５０５にて、図２１の追加力演算処理で算出したフロント追加横力が「０」よりも大きいか否かを判定する。そして、フロント追加横力が「０」よりも大きい場合には、前輪２FR，２FLのトー角を切り増し方向に補正して前輪２FR，２FLの横力を現在の発生方向と同方向に追加しなければならないと判断し、続くＳ１５１０にて、図２２及び図２３の摩擦円余裕演算処理で算出したＦＲ横力正追加限界値を、右前輪２FRが追加して発生可能な横力の余裕度であるＦＲ横力限界値として設定すると共に、同じく摩擦円余裕演算処理で算出したＦＬ横力正追加限界値を、左前輪２FLが追加して発生可能な横力の余裕度であるＦＬ横力限界値として設定する。
【０１９１】
また逆に、上記Ｓ１５０５にて、フロント追加横力が「０」よりも大きくないと判定した場合には、前輪２FR，２FLのトー角を切り戻し方向に補正して前輪２FR，２FLの横力を現在の発生方向と逆方向に追加しなければならないと判断し、Ｓ１５１５に移行して、摩擦円余裕演算処理で算出したＦＲ横力負追加限界値をＦＲ横力限界値として設定すると共に、同じく摩擦円余裕演算処理で算出したＦＬ横力負追加限界値をＦＬ横力限界値として設定する。
【０１９２】
そして、上記Ｓ１５１０或いはＳ１５１５の処理を行った後、Ｓ１５２０に進んで、今度は、図２１の追加力演算処理で算出したリア追加横力が「０」よりも大きいか否かを判定する。そして、リア追加横力が「０」よりも大きい場合には、後輪２RR，２RLのトー角を切り増し方向に補正して後輪２RR，２RLの横力を現在の発生方向と同方向に追加しなければならないと判断し、続くＳ１５２５にて、摩擦円余裕演算処理で算出したＲＲ横力正追加限界値を、右後輪２RRが追加して発生可能な横力の余裕度であるＲＲ横力限界値として設定すると共に、同じく摩擦円余裕演算処理で算出したＲＬ横力正追加限界値を、左後輪２RLが追加して発生可能な横力の余裕度であるＲＬ横力限界値として設定する。
【０１９３】
また逆に、上記Ｓ１５２０にて、リア追加横力が「０」よりも大きくないと判定した場合には、後輪２RR，２RLのトー角を切り戻し方向に補正して後輪２RR，２RLの横力を現在の発生方向と逆方向に追加しなければならないと判断し、Ｓ１５３０に移行して、摩擦円余裕演算処理で算出したＲＲ横力負追加限界値をＲＲ横力限界値として設定すると共に、同じく摩擦円余裕演算処理で算出したＲＬ横力負追加限界値をＲＬ横力限界値として設定する。
【０１９４】
そして、上記Ｓ１５２５或いはＳ１５３０の処理を行った後、Ｓ１５３５に進んで、下記の式５６，式５７に基づき、ＦＲ横力限界値割合とＦＬ横力限界値割合とを算出する。
【０１９５】
【数５６】
ＦＲ横力限界値割合＝ＦＲ横力限界値／（ＦＲ横力限界値＋ＦＬ横力限界値）…式５６
【０１９６】
【数５７】
ＦＬ横力限界値割合＝１−ＦＲ横力限界値割合 …式５７
そして更に、続くＳ１５４０にて、下記の式５８，式５９に基づき、ＲＲ横力限界値割合とＲＬ横力限界値割合とを算出する。
【０１９７】
【数５８】
ＲＲ横力限界値割合＝ＲＲ横力限界値／（ＲＲ横力限界値＋ＲＬ横力限界値）…式５８
【０１９８】
【数５９】
ＲＬ横力限界値割合＝１−ＲＲ横力限界値割合 …式５９
次に、Ｓ１５４５にて、下記の式６０，式６１に基づき、フロント追加横力の何割を実際に追加できるかを示すフロント横力追加可能割合と、リア追加横力の何割を実際に追加できるかを示すリア横力追加可能割合とを算出する。
【０１９９】
【数６０】
フロント横力追加可能割合＝（ＦＲ横力限界値＋ＦＬ横力限界値）／フロント追加横力 …式６０
【０２００】
【数６１】
リア横力追加可能割合＝（ＲＲ横力限界値＋ＲＬ横力限界値）／リア追加横力…式６１
そして、続くＳ１５５０にて、上記算出したフロント横力追加可能割合がリア横力追加可能割合よりも大きいか否かを判定し、フロント横力追加可能割合がリア横力追加可能割合よりも大きければ、Ｓ１５５５に進んで、小さい方のリア横力追加可能割合を、横力追加可能割合として設定する。また逆に、上記Ｓ１５５０にて、フロント横力追加可能割合がリア横力追加可能割合よりも大きくないと判定した場合には、Ｓ１５６０に移行して、小さい方のフロント横力追加可能割合を、横力追加可能割合として設定する。
【０２０１】
このようにＳ１５５５或いはＳ１５６０の処理を行った後、Ｓ１５６５へ移行して、上記設定した横力追加可能割合が「１」よりも大きいか否かを判定し、「１」よりも大きければ、次のＳ１５７０で横力追加可能割合を「１」に設定した後、Ｓ１５７５へ進む。また、Ｓ１５６５にて、横力追加可能割合が「１」よりも大きくないと判定した場合には、そのままＳ１５７５へ進む。
【０２０２】
そして、Ｓ１５７５にて、下記の式６２〜式６５に基づき、右前輪２FRに追加すべき横力であるＦＲ横力追加量と、左前輪２FLに追加すべき横力であるＦＬ横力追加量と、右後輪２RRに追加すべき横力であるＲＲ横力追加量と、左後輪２RLに追加すべき横力であるＲＬ横力追加量とを夫々算出し、その後、当該追加横力配分演算処理を終了する。
【０２０３】
【数６２】
ＦＲ横力追加量＝フロント追加横力×横力追加可能割合×ＦＲ横力限界値割合…式６２
【０２０４】
【数６３】
ＦＬ横力追加量＝フロント追加横力×横力追加可能割合×ＦＬ横力限界値割合…式６３
【０２０５】
【数６４】
ＲＲ横力追加量＝リア追加横力×横力追加可能割合×ＲＲ横力限界値割合 …式６４
【０２０６】
【数６５】
ＲＬ横力追加量＝リア追加横力×横力追加可能割合×ＲＬ横力限界値割合 …式６５
つまり、この追加横力配分演算処理では、図２１の追加力演算処理で算出したフロント追加横力とリア追加横力とを４輪のタイヤのグリップ力が限界を越えないように各車輪２FR，２FL，２RR，２RLへ配分可能な、各車輪の横力追加量（ＦＲ〜ＲＬ横力追加量）を算出している。
【０２０７】
そして、この追加横力配分演算処理が終了すると、図２４に示すように、追加力配分処理では、次にＳ１６００へ進んで、図２６の前後力余裕演算処理を実行する。
即ち、前後力余裕演算処理では、図２６に示すように、まずＳ１６１０にて、図１３の４輪摩擦円推定演算処理で算出したＦＲ摩擦円推定値と、図４の横力演算処理で算出した実際のフロント横力と、図５の前後力演算処理で算出した実際のフロント前後力と、図２５の追加横力配分演算処理で算出したＦＲ横力追加量とを読み出す。
【０２０８】
そして、下記の式６６に基づき、右前輪２FRが現在発生している前後力と同方向に追加して発生可能な右前輪２FRの前後力の余裕度であるＦＲ前後力正追加限界値を算出し、更に、下記の式６７に基づき、右前輪２FRが現在発生している前後力と逆方向に追加して発生可能な右前輪２FRの前後力の余裕度であるＦＲ前後力負追加限界値を算出する。
【０２０９】
【数６６】

【０２１０】
【数６７】

【０２１１】
つまり、Ｓ１６１０では、実際のフロント前後力とフロント横力を夫々２で割った値を、右前輪２FRの実際の前後力（＝フロント前後力／２）及び実際の横力（＝フロント横力／２）と見なし、その実際の横力に加えてＦＲ横力追加量を発生した場合の横力との合力がＦＲ摩擦円推定値と等しくなる前後力の値（＝式６６及び式６７の前項）から、実際の前後力を引くことにより、実際の前後力と同方向に追加して発生可能な前後力の余裕度であるＦＲ前後力正追加限界値を求めている。また、実際の横力に加えてＦＲ横力追加量を発生した場合の横力との合力がＦＲ摩擦円推定値と等しくなる前後力の値に、実際の前後力を加算することにより、実際の前後力と逆方向に追加して発生可能な前後力の余裕度であるＦＲ前後力負追加限界値を求めている。
【０２１２】
そして、続くＳ１６２０にて、図２１の追加力演算処理で算出した追加車体前後力が「０」よりも大きいか否かを判定する。そして、追加車体前後力が「０」よりも大きい場合には、右前輪２FRの前後力を現在の発生方向と同方向に追加しなければならないと判断し、続くＳ１６３０にて、上記Ｓ１６１０で算出したＦＲ前後力正追加限界値を、右前輪２FRが追加して発生可能な前後力の余裕度であるＦＲ前後力限界値として設定する。
【０２１３】
また逆に、上記Ｓ１６２０にて、追加車体前後力が「０」よりも大きくないと判定した場合には、右前輪２FRの前後力を現在の発生方向と逆方向に追加しなければならないと判断し、Ｓ１６４０に移行して、上記Ｓ１６１０で算出したＦＲ前後力負追加限界値をＦＲ前後力限界値として設定する。
【０２１４】
そして、上記Ｓ１６３０或いはＳ１６４０の処理を行った後、次のＳ１６５０〜Ｓ１６７０の各々にて、前述したＳ１６１０〜Ｓ１６４０と同様の手順により、左前輪２FLが追加して発生可能な前後力の余裕度であるＦＬ前後力限界値と、右後輪２RRが追加して発生可能な前後力の余裕度であるＲＲ前後力限界値と、左後輪２RLが追加して発生可能な前後力の余裕度であるＲＬ前後力限界値とを、夫々設定する。
【０２１５】
尚、Ｓ１６５０でＦＬ前後力限界値を設定する場合には、上記式６６，式６７の各々に対し、ＦＲ摩擦円推定値とＦＲ横力追加量に代えて、夫々、ＦＬ摩擦円推定値とＦＬ横力追加量を用いることにより、ＦＬ前後力正追加限界値とＦＬ前後力負追加限界値とを算出する。そして、追加車体前後力が「０」よりも大きい場合には、ＦＬ前後力正追加限界値をＦＬ前後力限界値として設定し、逆に、追加車体前後力が「０」よりも大きくない場合には、ＦＬ前後力負追加限界値をＦＬ前後力限界値として設定する。
【０２１６】
また、Ｓ１６６０でＲＲ前後力限界値を設定する場合には、上記式６６，式６７の各々に対し、ＦＲ摩擦円推定値とＦＲ横力追加量に代えて、夫々、ＲＲ摩擦円推定値とＲＲ横力追加量を用いると共に、フロント横力とフロント前後力に代えて、夫々、実際のリア横力とリア前後力を用いることにより、ＲＲ前後力正追加限界値とＲＲ前後力負追加限界値とを算出する。そして、追加車体前後力が「０」よりも大きい場合には、ＲＲ前後力正追加限界値をＲＲ前後力限界値として設定し、逆に、追加車体前後力が「０」よりも大きくない場合には、ＲＲ前後力負追加限界値をＲＲ前後力限界値として設定する。
【０２１７】
また更に、Ｓ１６７０でＲＬ前後力限界値を設定する場合には、上記式６６，式６７の各々に対し、ＦＲ摩擦円推定値とＦＲ横力追加量に代えて、夫々、ＲＬ摩擦円推定値とＲＬ横力追加量を用いると共に、フロント横力とフロント前後力に代えて、夫々、実際のリア横力とリア前後力を用いることにより、ＲＬ前後力正追加限界値とＲＬ前後力負追加限界値とを算出する。そして、追加車体前後力が「０」よりも大きい場合には、ＲＬ前後力正追加限界値をＲＬ前後力限界値として設定し、逆に、追加車体前後力が「０」よりも大きくない場合には、ＲＬ前後力負追加限界値をＲＬ前後力限界値として設定する。
【０２１８】
このように前後力余裕演算処理では、各車輪２FR，２FL，２RR，２RLが現在の横力に加えてＦＲ〜ＲＬ横力追加量を発生した場合に、各車輪２FR，２FL，２RR，２RLが追加して発生可能な前後力の余裕度であるＦＲ〜ＲＬ前後力限界値を、ＦＲ〜ＲＬ摩擦円推定値に基づき求めている。
【０２１９】
こうして図２６の前後力余裕演算処理が終了すると、図２４に示すように、追加力配分処理では、次にＳ１７００へ進んで、図２７の追加前後力配分演算処理を実行する。
即ち、追加前後力配分演算処理では、図２７に示すように、まずＳ１７０５にて、図２６の前後力余裕演算処理で算出したＦＲ前後力限界値がＦＬ前後力限界値よりも大きいか否かを判定する。そして、ＦＲ前後力限界値がＦＬ前後力限界値よりも大きければ、Ｓ１７１０に進んで、小さい方のＦＬ前後力限界値を２倍した値（＝ＦＬ前後力限界値×２）を、両前輪２FR，２FLが追加して発生可能な前後力の余裕度の合計値であるフロント前後力限界値として設定する。
【０２２０】
また逆に、上記Ｓ１７０５にて、ＦＲ前後力限界値がＦＬ前後力限界値よりも大きくないと判定した場合には、Ｓ１７１５に移行して、小さい方のＦＲ前後力限界値を２倍した値（＝ＦＲ前後力限界値×２）を、フロント前後力限界値として設定する。
【０２２１】
このようにＳ１７１０或いはＳ１７１５の処理を行った後、次にＳ１７２０へ移行して、今度は、図２６の前後力余裕演算処理で算出したＲＲ前後力限界値がＲＬ前後力限界値よりも大きいか否かを判定する。そして、ＲＲ前後力限界値がＲＬ前後力限界値よりも大きければ、Ｓ１７２５に進んで、小さい方のＲＬ前後力限界値を２倍した値（＝ＲＬ前後力限界値×２）を、両後輪２RR，２RLが追加して発生可能な前後力の余裕度の合計値であるリア前後力限界値として設定する。
【０２２２】
また逆に、上記Ｓ１７２０にて、ＲＲ前後力限界値がＲＬ前後力限界値よりも大きくないと判定した場合には、Ｓ１７３０に移行して、小さい方のＲＲ前後力限界値を２倍した値（＝ＲＲ前後力限界値×２）を、リア前後力限界値として設定する。
【０２２３】
そして、Ｓ１７２５或いはＳ１７３０の処理を行った後、Ｓ１７３５へ進んで、下記の式６８，式６９に基づき、フロント限界値割合とリア限界値割合とを算出する。
【０２２４】
【数６８】
フロント限界値割合＝フロント前後力限界値／（フロント前後力限界値＋リア前後力限界値） …式６８
【０２２５】
【数６９】
リア限界値割合＝１−フロント限界値割合 …式６９
そして更に、続くＳ１７４０にて、下記の式７０に基づき、追加車体前後力の何割を実際に追加できるかを示す前後力追加可能割合を算出する。
【０２２６】
【数７０】
前後力追加可能割合＝（フロント前後力限界値＋リア前後力限界値）／追加車体前後力 …式７０
次にＳ１７４５にて、上記算出した前後力追加可能割合が「１」よりも大きいか否かを判定し、「１」よりも大きければ、次のＳ１７５０で前後力追加可能割合を「１」に設定した後、Ｓ１７５５へ進む。また、上記Ｓ１７４５にて、前後力追加可能割合が「１」よりも大きくないと判定した場合には、そのままＳ１７５５へ進む。
【０２２７】
そして、Ｓ１７５５にて、下記の式７１〜式７４に基づき、右前輪２FRに追加すべき前後力であるＦＲ前後力追加量と、左前輪２FLに追加すべき前後力であるＦＬ前後力追加量と、右後輪２RRに追加すべき前後力であるＲＲ前後力追加量と、左後輪２RLに追加すべき前後力であるＲＬ前後力追加量とを夫々算出し、その後、当該追加前後力配分演算処理を終了する。
【０２２８】
【数７１】
ＦＲ前後力追加量＝追加車体前後力×前後力追加可能割合×フロント限界値割合／２ …式７１
【０２２９】
【数７２】
ＦＬ前後力追加量＝追加車体前後力×前後力追加可能割合×フロント限界値割合／２ …式７２
【０２３０】
【数７３】
ＲＲ前後力追加量＝追加車体前後力×前後力追加可能割合×リア限界値割合／２ …式７３
【０２３１】
【数７４】
ＲＬ前後力追加量＝追加車体前後力×前後力追加可能割合×リア限界値割合／２ …式７４
つまり、この追加前後力配分演算処理では、図２１の追加力演算処理で算出した追加車体前後力を４輪のタイヤのグリップ力が限界を越えないように各車輪２FR，２FL，２RR，２RLへ配分可能な、各車輪の前後力追加量（ＦＲ〜ＲＬ前後力追加量）を算出している。
【０２３２】
そして、この追加前後力配分演算処理の実行を終了すると、図２４の追加力配分処理も終了する。そして更に、ＥＣＵ２０は、追加力配分処理を終了すると、次に図２のＳ７０へ進み、このＳ７０にて、図２８の可変量演算処理を実行する。
【０２３３】
この可変量演算処理は、図２４の追加力配分処理（詳しくは、図２５の追加横力配分演算処理と図２７の追加前後力配分演算処理）で算出したＦＲ〜ＲＬ横力追加量とＦＲ〜ＲＬ前後力追加量とを、実際に各車輪２FR，２FL，２RR，２RLに発生させるための、アクチュエータの制御量を算出するための処理である。
【０２３４】
尚、図２８において、「＊＊」は、「ＦＲ」，「ＦＬ」，「ＲＲ」，及び「ＲＬ」の各々を択一的に示すものである。そして、「＊＊」が記された処理は、各車輪２FR，２FL，２RR，２RLの各々について行われるが、ここでは「＊＊」が「ＦＲ」である場合（つまり、右前輪２FRについての場合）を中心に説明する。
【０２３５】
図２８に示すように、ＥＣＵ２０が可変量演算処理の実行を開始すると、まずＳ１８００にて、図２５の追加横力配分演算処理で算出したＦＲ横力追加量を読み込む。
次にＳ１８０５にて、ＲＯＭから「横力追加量対追加トー可変角マップ」を読み込む。この「横力追加量対追加トー可変角マップ」は、図２９に示すように、横力追加量と、その横力追加量を得るために必要な車輪のトー角の変化角度である追加トー可変角とを対応させて記憶したデータマップであり、各車輪２FR，２FL，２RR，２RL毎に用意されている。そして、横力追加量が正に大きいほど追加トー可変角が切り増し方向に増加し、逆に、横力追加量が負に大きいほど追加トー可変角が切り戻し方向に増加するように設定されている。
【０２３６】
そして、続くＳ１８１０にて、上記Ｓ１８００で読み込んだＦＲ横力追加量に対応する右前輪２FRの追加トー可変角（ＦＲ追加トー可変角）を、上記Ｓ１８０５で読み込んだ「横力追加量対追加トー可変角マップ」に基づき算出する。
次にＳ１８１５にて、図９の４輪横滑り角度演算処理で算出したＦＲ横滑り角度を入力し、続くＳ１８２０にて、ＦＲ横滑り角度と上記Ｓ１８１０で算出したＦＲ追加トー可変角との和（＝ＦＲ横滑り角度＋ＦＲ追加トー可変角）が、所定値Ｋ９よりも大きいか否かを判定する。そして、上記和の値が所定値Ｋ９よりも大きくなければ、そのままＳ１８３０以降の処理へ進むが、所定値Ｋ９よりも大きい場合には、Ｓ１８２５にて、所定値Ｋ９からＦＲ横滑り角度を引いた値（＝Ｋ９−ＦＲ横滑り角度）をＦＲ追加トー可変角として設定し直した後、Ｓ１８３０以降の処理へ進む。
【０２３７】
尚、上記所定値Ｋ９は、タイヤが限界に達すると見なされる横滑り角度の値に設定されており、上記Ｓ１８２０及びＳ１８２５の処理では、現在のＦＲ横滑り角度とこれから制御しようとしているＦＲ追加トー可変角との和が、その所定値Ｋ９を越えないようにガードをかけている。一方、上記Ｓ１８００〜Ｓ１８２５については、右前輪２FRについてのみ説明したが、他の車輪２FL，２RR，２RLについても全く同様に実行されて、ＦＬ〜ＲＬ横力追加量を夫々得るために必要なトー角の変化角度であるＦＬ追加トー可変角，ＲＲ追加トー可変角，及びＲＬ追加トー可変角が夫々算出される。
【０２３８】
そして、このようにしてＦＲ〜ＲＬ追加トー可変角を算出すると、次にＳ１８３０〜Ｓ１８４５にて、下記の式７５〜式７８に基づき、トーコントロールアクチュエータ２２FRにより調節すべき右前輪２FRのトー角であるＦＲトー可変角と、トーコントロールアクチュエータ２２FLにより調節すべき左前輪２FLのトー角であるＦＬトー可変角と、トーコントロールアクチュエータ２２RRにより調節すべき右後輪２RRのトー角であるＲＲトー可変角と、トーコントロールアクチュエータ２２RLにより調節すべき左後輪２RLのトー角であるＲＬトー可変角とを、夫々算出する。
【０２３９】
【数７５】
ＦＲトー可変角＝ＦＲトー可変角の前回値＋ＦＲ追加トー可変角−Ｆトー角補正量 …式７５
【０２４０】
【数７６】
ＦＬトー可変角＝ＦＬトー可変角の前回値＋ＦＬ追加トー可変角−Ｆトー角補正量 …式７６
【０２４１】
【数７７】
ＲＲトー可変角＝ＲＲトー可変角の前回値＋ＲＲ追加トー可変角 …式７７
【０２４２】
【数７８】
ＲＬトー可変角＝ＲＬトー可変角の前回値＋ＲＬ追加トー可変角 …式７８
尚、式７５，式７６における「Ｆトー角補正量」は、図１７の目標横力演算処理で、フロント目標横力とリア目標横力を算出する際に用いた前輪２FR，２FLに対する仮想的なトー角の補正量である。そして、上記式７５，式７６で「Ｆトー角補正量」を減じているのは、図１７の目標横力演算処理で算出したフロント目標横力とリア目標横力が、前輪２FR，２FLのトー角を「Ｆトー角補正量」の分だけ小さくすることを前提として、フロント摩擦円限界値及びリア摩擦円限界値により実現可能な値となっているからである。
【０２４３】
このようにしてＦＲ〜ＲＬトー可変角を算出すると、次にＳ１８５０へ進む。そして、このＳ１８５０にて、図２７の追加前後力配分演算処理で算出したＦＲ前後力追加量を読み込み、続くＳ１８５５にて、ＲＯＭから「前後力追加量対ブレーキ油圧可変量マップ」を読み込む。
【０２４４】
この「前後力追加量対ブレーキ油圧可変量マップ」は、図３０に示すように、前後力追加量と、その前後力追加量を得るために車輪のブレーキ装置へ追加して加えるべきブレーキ油圧であるブレーキ油圧可変量とを、対応させて記憶したデータマップであり、各車輪２FR，２FL，２RR，２RL毎に用意されている。そして、前後力追加量が負（加速方向）である場合には、ブレーキ油圧可変量が「０」となり、前後力追加量が正（減速方向）である場合には、その値が大きいほど、ブレーキ油圧可変量がブレーキ装置による制動力を増加させる方向（増圧方向）に大きくなるように設定されている。
【０２４５】
次に、続くＳ１８６０にて、上記Ｓ１８５０で読み込んだＦＲ前後力追加量に対応するブレーキ油圧可変量（ＦＲブレーキ油圧可変量）を、上記Ｓ１８５５で読み込んだ「前後力追加量対ブレーキ油圧可変量マップ」に基づき算出する。
ここで、上記Ｓ１８５０〜Ｓ１８６０については、右前輪２FRについてのみ説明したが、他の３つの車輪２FL，２RR，２RLについても全く同様に実行される。そして、ＦＬ〜ＲＬ前後力追加量の各々を得るために各ブレーキ装置２６FL，２６RR，２６RLへ追加して加えるべきブレーキ油圧である、ＦＬブレーキ油圧可変量，ＲＲブレーキ油圧可変量，及びＲＬブレーキ油圧可変量が夫々算出される。
【０２４６】
このようにして各車輪２FR，２FL，２RR，２RLのブレーキ油圧可変量を算出すると、次にＳ１８６５へ進んで、下記の式７９に示す如く、図２７の追加前後力配分演算処理で算出したＦＲ〜ＲＬ前後力追加量の総和である前後力追加量を算出する。
【０２４７】
【数７９】
前後力追加量＝ＦＲ前後力追加量＋ＦＬ前後力追加量＋ＲＲ前後力追加量＋ＲＬ前後力追加量 …式７９
そして、続くＳ１８７０にて、ＲＯＭから「前後力追加量対アクセル開度可変量マップ」を読み込む。
【０２４８】
尚、この「前後力追加量対アクセル開度可変量マップ」は、図３１に示すように、上記Ｓ１８６５で算出される前後力追加量と、その前後力追加量を得るために必要なアクセル開度（スロットル弁の開度）の変化量であるアクセル開度可変量とを、対応させて記憶したデータマップである。そして、前後力追加量が正（減速方向）である場合には、アクセル開度可変量が「０」となり、前後力追加量が負（加速方向）である場合には、その絶対値が大きいほど、アクセル開度可変量がエンジンの出力を増加させる方向（開方向）に大きくなるように設定されている。
【０２４９】
次に、続くＳ１８７５にて、上記Ｓ１８６５で算出した前後力追加量に対応するアクセル開度可変量を、上記Ｓ１８７０で読み込んだ「前後力追加量対アクセル開度可変量マップ」に基づき算出する。
そして、続くＳ１８８０にて、図２７の追加前後力配分演算処理で算出したフロント限界値割合を、センタ・ディファレンシャルギアが前輪２FR，２FLと後輪２RR，２RLとに配分すべきトルクの割合である、センタデフ前後力配分割合として設定する。
【０２５０】
そして更に、続くＳ１８８５及びＳ１８９０の各々にて、下記の式８０，式８１に基づき、フロント・ディファレンシャルギアが前輪２FR，２FLの各々に配分すべきトルクの割合であるフロントデフ前後力配分割合と、リア・ディファレンシャルギアが後輪２RR，２RLの各々に配分すべきトルクの割合であるリアデフ前後力配分割合とを算出し、その後、当該可変量演算処理を終了する。
【０２５１】
【数８０】
フロントデフ前後力配分割合＝ＦＲ前後力追加量／（ＦＲ前後力追加量＋ＦＬ前後力追加量） …式８０
【０２５２】
【数８１】
リアデフ前後力配分割合＝ＲＲ前後力追加量／（ＲＲ前後力追加量＋ＲＬ前後力追加量） …式８１
ここで、ＥＣＵ２０は、図２の処理と並行して、図示しない駆動処理を定期的に実行しており、この駆動処理の実行により、上記可変量演算処理での算出結果に基づき、トーコントロールアクチュエータ２２FR，２２FL，２２RR，２２RL、ブレーキコントロールアクチュエータ２８、アクセルコントロールアクチュエータ３０、センタデフコントロールアクチュエータ３２Ｃ、フロントデフコントロールアクチュエータ３２Ｆ、及びリアデフコントロールアクチュエータ３２Ｒの各々を制御している。
【０２５３】
具体的に説明すると、まずＥＣＵ２０は、可変量演算処理のＳ１８３０〜Ｓ１８４５で算出したＦＲ〜ＲＬトー可変角に応じてトーコントロールアクチュエータ２２FR，２２FL，２２RR，２２RLを作動させることにより、各車輪２FR，２FL，２RR，２RLのトー角を、夫々、上記ＦＲ〜ＲＬトー可変角の分だけ変化させる。そして、これにより、各車輪２FR，２FL，２RR，２RLが、ＦＲ〜ＲＬ横力追加量を追加して発生することとなる。
【０２５４】
また、ＥＣＵ２０は、可変量演算処理のＳ１８６０で算出したＦＲ〜ＲＬブレーキ油圧可変量に応じてブレーキコントロールアクチュエータ２８を作動させることにより、各車輪２FR，２FL，２RR，２RLのブレーキ装置２６FR，２６FL，２６RR，２６RLに与えるブレーキ油圧を、夫々、上記ＦＲ〜ＲＬブレーキ油圧可変量の分だけ増加させる。そして、これにより、ＦＲ〜ＲＬ前後力追加量が正（減速方向）である場合には、制動力が増加して、各車輪２FR，２FL，２RR，２RLが、そのＦＲ〜ＲＬ前後力追加量を追加して発生することとなる。
【０２５５】
一方、ＥＣＵ２０は、可変量演算処理のＳ１８７５で算出したアクセル開度可変量に応じてアクセルコントロールアクチュエータ３０を作動させることにより、アクセル開度（スロットル弁の開度）を上記アクセル開度可変量の分だけ変化させる。更に、ＥＣＵ２０は、可変量演算処理のＳ１８８０で設定したセンタデフ前後力配分割合に応じてセンタデフコントロールアクチュエータ３２Ｃを作動させることにより、センタ・ディファレンシャルギアによる前後輪へのトルク配分割合を、上記センタデフ前後力配分割合に制御し、また、可変量演算処理のＳ１８８５，Ｓ１８９０で算出したフロントデフ前後力配分割合とリアデフ前後力配分割合とに応じて、フロントデフコントロールアクチュエータ３２Ｆとリアデフコントロールアクチュエータ３２Ｒとを夫々作動させることにより、フロント・ディファレンシャルギアによる各前輪２FR，２FLへのトルク配分割合を、上記センタデフ前後力配分割合に制御すると共に、リア・ディファレンシャルギアによる各後輪２RR，２RLへのトルク配分割合を、上記リアデフ前後力配分割合に制御する。
【０２５６】
そして、上記各アクチュエータ３０，３２Ｃ，３２Ｆ，３２Ｒに対する制御により、エンジンの出力が、可変量演算処理のＳ１８６５で算出した前後力追加量の分だけ増加されると共に、そのエンジン出力の増加分が、ＦＲ〜ＲＬ前後力追加量の相互割合に応じて各車輪２FR，２FL，２RR，２RLへ駆動力として配分され、この結果、ＦＲ〜ＲＬ前後力追加量が負（加速方向）である場合には、各車輪２FR，２FL，２RR，２RLが、そのＦＲ〜ＲＬ前後力追加量を追加して発生することとなる。
【０２５７】
次に、ＥＣＵ２０は、図２８の可変量演算処理を終了すると、図２のＳ７５へ進む。そして、このＳ７５にて、図３２に示す摩擦円拡大処理を実行する。
この摩擦円拡大処理は、車輪のグリップ力に余裕が無く、トー角を変化させることではもはや横力を追加することができない場合に、その車輪のキャンバ角を調節して、該車輪の摩擦円半径（即ち、その車輪が発生可能な最大のグリップ力）を拡大するための処理である。
【０２５８】
図３２に示すように、ＥＣＵ２０が摩擦円拡大処理の実行を開始すると、まずＳ１９００にて、図９の４輪横滑り角度演算処理で算出したＦＲ横滑り角度が所定値Ｋ１０よりも大きいか否かを判定する。尚、所定値Ｋ１０は、タイヤが限界に達すると見なされる横滑り角度の値に設定されている。
【０２５９】
そして、ＦＲ横滑り角度が所定値Ｋ１０よりも大きい場合には、次のＳ１９０５にて、図２５の追加横力配分演算処理で設定したＦＲ横力限界値（即ち、右前輪２FRが追加して発生可能な横力の余裕度）が「０」であるか否かを判定し、ＦＲ横力限界値が「０」であれば、続くＳ１９１０にて、図２１の追加力演算処理で算出したフロント追加横力を入力する。
【０２６０】
一方、上記Ｓ１９００にて、ＦＲ横滑り角度が所定値Ｋ１０よりも大きくないと判定した場合、或いは、上記Ｓ１９０５にて、ＦＲ横力限界値が「０」ではないと判定した場合（つまり、右前輪２FRが横力を追加して発生可能な場合）には、Ｓ１９１５に移行して、フロント追加横力を「０」に設定する。
【０２６１】
そして、上記Ｓ１９１０或いはＳ１９１５のうちの何れかを実行した後、Ｓ１９２０へ進み、ＲＯＭから「追加横力対キャンバ可変角マップ」を読み込む。
尚、この「追加横力対キャンバ可変角マップ」は、図３３に示すように、追加横力（フロント追加横力或いはリア追加横力）と、キャンバコントロールアクチュエータ２４FR，２４FL，２４RR，２４RLにより車輪のキャンバ角を何度変化させるべきかを表すキャンバ可変角との関係を記憶したデータマップであり、追加横力が「０」の場合にキャンバ可変角が「０」となり、また、追加横力の絶対値が大きくなるほど、キャンバ可変角が大きくなるように設定されている。
【０２６２】
そして、続くＳ１９２５にて、現在のフロント追加横力（即ち、Ｓ１９１０を実行した場合には図２１の追加力演算処理で算出した値であり、Ｓ１９１５を実行した場合には「０」である。）に対応する右前輪２FRのキャンバ可変角（ＦＲキャンバ可変角）を、上記Ｓ１９２０で読み込んだ「追加横力対キャンバ可変角マップ」に基づき算出し、次にＳ１９３０にて、図１１の対地キャンバ角演算処理で算出したＦＲ対地キャンバ角（右前輪２FRの実際の対地キャンバ角）を入力する。
【０２６３】
次に、続くＳ１９３５にて、上記Ｓ１９２５で算出したＦＲキャンバ可変角が、ＦＲ対地キャンバ角の絶対値よりも大きいか否かを判定し、ＦＲキャンバ可変角の方が大きくなければ、そのままＳ１９４５へ進むが、ＦＲキャンバ可変角の方が大きければ、Ｓ１９４０にて、ＦＲキャンバ可変角の値を、ＦＲ対地キャンバ角の絶対値と等しい値に設定し直した後、Ｓ１９４５へ進む。
【０２６４】
そして、Ｓ１９４５にて、ＦＲ対地キャンバ角が「０」よりも大きいか否かを判定し、ＦＲ対地キャンバ角が「０」よりも大きければ、Ｓ１９５０に進んで、ＦＲキャンバ可変角に「−１」を乗じた値を、キャンバコントロールアクチュエータ２４FRにより調節すべき右前輪２FRのキャンバ角の変化分であるＦＲキャンバ角制御量として設定する。また逆に、ＦＲ対地キャンバ角が「０」よりも大きくなければ、Ｓ１９５５へ移行して、ＦＲキャンバ可変角を、そのままＦＲキャンバ角制御量として設定する。
【０２６５】
つまり、Ｓ１９００〜Ｓ１９５５では、ＦＲ横滑り角度が所定値Ｋ１０よりも大きく、且つ、ＦＲ横力限界値が「０」である場合に、トー角を変化させることではもはや右前輪２FRの横力を追加することができないと判断して、右前輪２FRの対地キャンバ角が０度に近づくように（即ち、右前輪２FRが地面に対して垂直となるように）、ＦＲキャンバ角制御量を設定している。尚、Ｓ１９３５及びＳ１９４０は、ＦＲキャンバ角制御量が過大にならないようにするための処理である。また逆に、ＦＲ横滑り角度が所定値Ｋ１０よりも大きくないか、或いは、ＦＲ横力限界値が「０」でない場合には、ＦＲキャンバ角制御量を「０」に設定して、キャンバコントロールアクチュエータ２４FRによる右前輪２FRのキャンバ角制御を止めるようにしている。
【０２６６】
そして、このようにＦＲキャンバ角制御量を設定した後、次のＳ１９６０〜Ｓ１９７０の各々にて、前述したＳ１９００〜Ｓ１９５５と同様の手順により、キャンバコントロールアクチュエータ２４FLにより調節すべき左前輪２FLのキャンバ角の変化分であるＦＬキャンバ角制御量と、キャンバコントロールアクチュエータ２４RRにより調節すべき右後輪２RRのキャンバ角の変化分であるＲＲキャンバ角制御量と、キャンバコントロールアクチュエータ２４RLにより調節すべき左後輪２RLのキャンバ角の変化分であるＲＬキャンバ角制御量とを、夫々設定する。
【０２６７】
尚、Ｓ１９６０でＦＬキャンバ角制御量を設定する場合には、図３２のＳ１９００〜Ｓ１９５５で用いられている「ＦＲ」なるアルファベットを、「ＦＬ」なるアルファベットに置き換えた処理が行われる。
また、Ｓ１９６５及びＳ１９７０の各々で、ＲＲキャンバ角制御量とＲＬキャンバ角制御量を設定する場合にも、図３２のＳ１９００〜Ｓ１９５５で用いられている「ＦＲ」なるアルファベットを、「ＲＲ」或いは「ＲＬ」なるアルファベットに置き換えた処理が行われるが、特にこの場合には、前述したＳ１９１０にて、図２１の追加力演算処理で算出したリア追加横力を入力し、またＳ１９１５では、リア追加横力を「０」に設定する。そして、Ｓ１９２５にて、リア追加横力に対応するキャンバ可変角（ＲＲキャンバ可変角，ＲＬキャンバ可変角）を「追加横力対キャンバ可変角マップ」に基づき算出する。
【０２６８】
こうして、Ｓ１９６０〜Ｓ１９７０の処理によりＦＬ〜ＲＬキャンバ角制御量を設定すると、当該摩擦円拡大処理を終了する。そして、その後、次の処理周期が到来すると、図２のＳ１０へ戻って４輪荷重演算処理の実行を開始し、再び、図２に示されている各処理が順次実行される。
【０２６９】
尚、ＥＣＵ２０は、図２の処理と並行して実行される前述の駆動処理にて、摩擦円拡大処理で設定したＦＲ〜ＲＬキャンバ角制御量を読み出し、そのＦＲ〜ＲＬキャンバ角制御量に応じてキャンバコントロールアクチュエータ２４FR，２４FL，２４RR，２４RLを作動させることにより、各車輪２FR，２FL，２RR，２RLのキャンバ角を、夫々、上記ＦＲ〜ＲＬキャンバ角制御量の分だけ変化させる。
【０２７０】
これにより、グリップ力に余裕が無くて、トー角を変化させることではもはや横力を追加することができない車輪について、その車輪の対地キャンバ角が０度に近づけられ、その車輪の発生可能な最大のグリップ力が増大する。そして、ＥＣＵ２０が次に図１３の４輪摩擦円推定演算処理を実行した際には、その車輪の対地キャンバ角が０度に近づけられているため、図１５の「対地キャンバ角対摩擦円減少係数マップ」に基づき算出される摩擦円減少係数がより「１」に近い値となり、この結果、その車輪の摩擦円推定値も大きな値として算出される。よって、その車輪の実際の摩擦円半径と、制御で用いる摩擦円推定値とが拡大されることとなり、車輪に装着されたタイヤの性能を最大限に生かすことができるようになる。
【０２７１】
以上詳述したように、本実施形態では、摩擦円設定手段としての図１３の４輪摩擦円推定演算処理により、各車輪２FR，２FL，２RR，２RLが路面との間で発生可能な力の合力の最大値を、摩擦円の半径であるＦＲ〜ＲＬ摩擦円推定値として設定している。
【０２７２】
そして、走行状態検出手段としての横Ｇセンサ６、ヨーレートセンサ８、前後Ｇセンサ１０、及び図示しない検出処理により、車体の実際の運動物理量であるヨーレート、横Ｇ、及び前後Ｇを検出し、発生力算出手段としての図４の横力演算処理及び図５の前後力演算処理により、上記検出した実際のヨーレート、横Ｇ、及び前後Ｇから、各車輪２FR，２FL，２RR，２RLが横方向と前後方向とに実際に発生している横力と前後力とを算出している。
【０２７３】
尚、図４の横力演算処理で算出したフロント横力を２で割った値を、各前輪２FR，２FLの実際の横力として用い、同じく横力演算処理で算出したリア横力を２で割った値を、各後輪２RR，２RLの実際の横力として用いている。また同様に、図５の前後力演算処理で算出したフロント前後力を２で割った値を、各前輪２FR，２FLの実際の前後力として用い、同じく前後力演算処理で算出したリア前後力２で割った値を、各後輪２RR，２RLの実際の前後力として用いている。
【０２７４】
そして更に、余裕度算出手段としての図２２，図２３の摩擦円余裕演算処理及び図２６の前後力余裕演算処理により、各車輪２FR，２FL，２RR，２RLが実際に発生している横力及び前後力と、ＦＲ〜ＲＬ摩擦円推定値とに基づき、各車輪２FR，２FL，２RR，２RLが横方向に追加して発生可能な力の余裕度であるＦＲ〜ＲＬ横力正追加限界値及びＦＲ〜ＲＬ横力負追加限界値と、各車輪２FR，２FL，２RR，２RLが前後方向に追加して発生可能な力の余裕度であるＦＲ〜ＲＬ前後力正追加限界値及びＦＲ〜ＲＬ前後力負追加限界値とを算出している。
【０２７５】
また、図１７の目標横力演算処理におけるＳ１００５〜Ｓ１０３０、及び図１８の目標前後力演算処理におけるＳ１１１０〜Ｓ１１８０からなる目標設定手段としての処理により、運転者の操作に応じた車体の目標ヨーレート、目標横Ｇ、及び目標前後Ｇを設定し、更に、図１７の目標横力演算処理におけるＳ１０３５〜Ｓ１０５０、図１８の目標前後力演算処理におけるＳ１１９０、図２１の追加力演算処理、図２５の追加横力配分演算処理、及び図２７の追加前後力配分演算処理からなる追加力設定手段としての処理により、目標ヨーレート、目標横Ｇ、及び目標前後Ｇを実現するために各車輪が横方向と前後方向とに夫々追加して発生すべき力の大きさであるＦＲ〜ＲＬ横力追加量及びＦＲ〜ＲＬ前後力追加量を、ＦＲ〜ＲＬ横力正追加限界値及びＦＲ〜ＲＬ横力負追加限界値とＦＲ〜ＲＬ前後力正追加限界値及びＦＲ〜ＲＬ前後力負追加限界値とに応じて、それら追加限界値以内に収まるように設定している。
【０２７６】
そして、駆動制御手段としての図２８の可変量演算処理及び図示しない駆動処理により、各車輪がＦＲ〜ＲＬ横力追加量とＦＲ〜ＲＬ前後力追加量とを追加して発生するように、発生力調節手段としてのトーコントロールアクチュエータ２２FR，２２FL，２２RR，２２RL、ブレーキコントロールアクチュエータ２８、アクセルコントロールアクチュエータ３０、センタデフコントロールアクチュエータ３２Ｃ、フロントデフコントロールアクチュエータ３２Ｆ、及びリアデフコントロールアクチュエータ３２Ｒを作動させている。
【０２７７】
つまり、本実施形態では、各車輪が実際に発生している横力と前後力との大きさを求め、その求めた力の大きさと、各車輪について推定した摩擦円半径であるＦＲ〜ＲＬ摩擦円推定値とから、各車輪の横力と前後力との余裕度を求めている。そして、その余裕度の範囲内で、各車輪の横方向と前後方向との発生力を追加（正の追加或いは負の追加）することにより、車体の実際のヨーレート，横Ｇ，及び前後Ｇが目標ヨーレート，目標横Ｇ，及び目標前後Ｇとなるようにしており、これによって、各車輪が路面との間で発生する力の合力がＦＲ〜ＲＬ摩擦円推定値を越えないように、各車輪の発生力の大きさと方向を制御している。
【０２７８】
このため、本実施形態によれば、各車輪が発生可能なグリップ力を最大限に生かしつつ、各車輪のグリップ力の限界を越えない範囲内で車両の走行状態を目標の走行状態とすることができ、車両全体の限界を非常に高くすることができる。よって、車両の走行安定性を極めて高いものとすることができる。
また、本実施形態では、図１７の目標横力演算処理におけるＳ１０５５〜Ｓ１０７０からなる目標補正手段としての処理により、設定した目標ヨーレート及び目標横Ｇが各車輪のＦＲ〜ＲＬ摩擦円推定値で表される力によって実現可能であるか否かを判定し、実現不能と判定した場合に（Ｓ１０６０：ＮＯ，Ｓ１０６５：ＮＯ）、目標ヨーレート及び目標横Ｇを、ＦＲ〜ＲＬ摩擦円推定値で表される力によって実現可能な値に補正するようにしている。
【０２７９】
よって、例えば運転者が高速走行中にステアリングを急激且つ大きく操作して、目標ヨーレート及び目標横Ｇが極端に大きく設定されたとしても、その値が、各車輪が発生可能な力で実現できる値に補正されるため、車両が急に限界を越えてしまうことが確実に防止されて、車両の走行安定性を確実に保つことができる。
【０２８０】
一方更に、本実施形態では、荷重検出手段としての図３の４輪荷重演算処理により、各車輪の荷重を検出し、キャンバ角検出手段としての図１１の対地キャンバ角演算処理により、各車輪の対地キャンバ角を検出し、摩擦係数検出手段としての図７及び図８の路面μ推定演算処理により、走行路面の摩擦係数を検出し、タイヤ判定手段としての図１０のタイヤ種類判定演算処理により、車輪に装着されたタイヤのグリップ性能レベルを検出している。
【０２８１】
そして、図１３の４輪摩擦円推定演算処理では、車輪の荷重が大きいほど、車輪の対地キャンバ角が０度に近いほど、走行路面の摩擦係数が大きいほど、タイヤのグリップ性能レベルが高いほど、各車輪の摩擦円推定値（ＦＲ〜ＲＬ摩擦円推定値）を大きい値に設定するようにしている。
【０２８２】
このため、ＦＲ〜ＲＬ摩擦円推定値の設定精度が高くなり、各車輪が発生可能な力の余裕度をより正確に算出できるため、車輪が発生可能なグリップ力をより確実に生かすことができる。
また、本実施形態では、キャンバコントロールアクチュエータ２４FR，２４FL，２４RR，２４RL、図３２の摩擦円拡大処理、及び図示しない駆動処理からなるキャンバ角制御手段により、横力を追加して発生する余裕度が無い車輪を特定し、その特定した車輪の対地キャンバ角を０度へ近づけるように調整するようにしている。
【０２８３】
このため、追加して力を発生することができなくなった車輪でも、その車輪が発生可能なグリップ力が増大されると共に、対地キャンバ角が０度へ近づけられることにより、その車輪に対して設定される制御上の摩擦円推定値も大きくなるため、車輪に装着されたタイヤの性能を最大限に生かすことができる。
【０２８４】
ところで、上記実施形態のＥＣＵ２０は、車両運転者によるステアリングやアクセルペダルなどの操作状況から、目標ヨーレート，目標横Ｇ，及び目標前後Ｇを設定しているが、人が車両を運転するのではなく、外部からの指令によって車両を自動操縦するような場合には、ＥＣＵ２２が、目標ヨーレート，目標横Ｇ，及び目標前後Ｇを外部から入力し、その入力した値を図１７及び図１８の処理で用いるようにすれば良い。尚、この場合、図１７のＳ１０６０或いはＳ１０６５で否定判定した際には、Ｓ１０７０にて目標ヨーレートの値自体を小さい値に補正し、その後、Ｓ１０３０以降の処理を繰り返すようにすれば良い。
【図面の簡単な説明】
【図１】 実施形態の車両の制御系全体の構成を表わす概略構成図である。
【図２】 図１のＥＣＵで実行される処理全体を表すフローチャートである。
【図３】 図２内の４輪荷重演算処理を表すフローチャートである。
【図４】 図２内の横力演算処理を表すフローチャートである。
【図５】 図２内の前後力演算処理を表すフローチャートである。
【図６】 図５の前後力演算処理で参照される前後Ｇ対前後力マップを説明する説明図である。
【図７】 図２内の路面μ推定演算処理の前半部を表すフローチャートである。
【図８】 図２内の路面μ推定演算処理の後半部を表すフローチャートである。
【図９】 図２内の４輪横滑り角度演算処理を表すフローチャートである。
【図１０】 図２内のタイヤ種類判定演算処理を表すフローチャートである。
【図１１】 図２内の対地キャンバ角演算処理を表すフローチャートである。
【図１２】 図１１の対地キャンバ角演算処理で参照されるハイト対キャンバ角変化量マップを説明する説明図である。
【図１３】 図２内の４輪摩擦円推定演算処理を表すフローチャートである。
【図１４】 図１３の４輪摩擦円推定演算処理で参照される荷重対摩擦円マップを説明する説明図である。
【図１５】 図１３の４輪摩擦円推定演算処理で参照される対地キャンバ角対摩擦円減少係数マップを説明する説明図である。
【図１６】 図２内の目標走行状態設定処理を表すフローチャートである。
【図１７】 図１６の目標走行状態設定処理で実行される目標横力演算処理を表すフローチャートである。
【図１８】 図１６の目標走行状態設定処理で実行される目標前後力演算処理を表すフローチャートである。
【図１９】 図１８の目標前後力演算処理で参照されるアクセル状態対目標前後Ｇマップを説明する説明図である。
【図２０】 図１８の目標前後力演算処理で参照されるブレーキ踏力対目標前後Ｇマップを説明する説明図である。
【図２１】 図２内の追加力演算処理を表すフローチャートである。
【図２２】 図２内の摩擦円余裕演算処理の前半部を表すフローチャートである。
【図２３】 図２内の摩擦円余裕演算処理の後半部を表すフローチャートである。
【図２４】 図２内の追加力配分処理を表すフローチャートである。
【図２５】 図２４の追加力配分処理で実行される追加横力配分演算処理を表すフローチャートである。
【図２６】 図２４の追加力配分処理で実行される前後力余裕演算処理を表すフローチャートである。
【図２７】 図２４の追加力配分処理で実行される追加前後力配分演算処理を表すフローチャートである。
【図２８】 図２内の可変量演算処理を表すフローチャートである。
【図２９】 図２８の可変量演算処理で参照される横力追加量対追加トー可変角マップを説明する説明図である。
【図３０】 図２８の可変量演算処理で参照される前後力追加量対ブレーキ油圧可変量マップを説明する説明図である。
【図３１】 図２８の可変量演算処理で参照される前後力追加量対アクセル開度可変量マップを説明する説明図である。
【図３２】 図２内の摩擦円拡大処理を表すフローチャートである。
【図３３】 図３２の摩擦円拡大処理で参照される追加横力対キャンバ可変角マップを説明する説明図である。
【符号の説明】
２FR，２FL，２RR，２RL…車輪 ４FR，４FL，４RR，４RL…車輪速センサ
５FR，５FL，５RR，５RL…ハイトセンサ ６…横Ｇセンサ
８…ヨーレートセンサ １０…前後Ｇセンサ
１２…ステアリング角度センサ １３…ブレーキスイッチ
１６…ブレーキ踏力センサ １８…アクセル開度センサ
２０…電子制御装置（ＥＣＵ）
２２FR，２２FL，２２RR，２２RL…トーコントロールアクチュエータ
２４FR，２４FL，２４RR，２４RL…キャンバコントロールアクチュエータ
２６FR，２６FL，２６RR，２６RL…ブレーキ装置
２８…ブレーキコントロールアクチュエータ
３０…アクセルコントロールアクチュエータ
３２Ｃ…センタデフコントロールアクチュエータ
３２Ｆ…フロントデフコントロールアクチュエータ
３２Ｒ…リアデフコントロールアクチュエータ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicle control device for ensuring running stability of a vehicle.
[0002]
[Prior art]
Conventionally, an antilock brake system (commonly known as ABS) and a traction control system (commonly known as TRC) have been put to practical use as this type of device. In the ABS and TRC, the speed of the vehicle body (vehicle speed) is estimated based on a signal from a wheel speed sensor that detects the rotational speed (wheel speed) of each wheel of the vehicle, and the estimated vehicle speed and the rotation of each wheel are estimated. The slip ratio of each wheel is calculated from the difference from the speed, and if the slip ratio exceeds a predetermined value, it is determined that the grip force of the wheel (specifically, the tire attached to the wheel) has reached its limit, and the grip force is The longitudinal force of the wheel is controlled so as to return to the limit region. The wheel front-rear force is a force generated by the wheel in the front-rear direction, and is controlled by a braking force or a driving force applied to the wheel.
[0003]
Further, in recent years, as in the so-called turning trace control system, in addition to the vehicle speed estimated based on the signal from the wheel speed sensor, further based on the signals from the yaw rate (yaw angular velocity) sensor and the lateral acceleration sensor attached to the vehicle body. The vehicle body slip angle (side slip angle) is obtained, and when the slip angle exceeds a predetermined value, it is determined that the lateral limit of the entire vehicle has been reached, and the turning state of the vehicle returns to the target stable state. In addition, a device for controlling the longitudinal force of the wheel has been put into practical use.
[0004]
[Problems to be solved by the invention]
However, the conventional device cannot be controlled until the wheel grip force exceeds the limit.For example, after a failure such as a vehicle spin or a tire full lock occurs, the vehicle returns to the target stable running state. Therefore, it is impossible to prevent the occurrence of a state of anxiety for the vehicle driver.
[0005]
This is because the conventional apparatus is not aware of the margin including the direction of the grip force that can be generated by each wheel.
The present invention has been made in view of these problems, and an object of the present invention is to provide a vehicle control device that can further improve the running stability of the vehicle by making the most of the gripping force that can be generated by the wheels. It is said.
[0006]
[Means for solving the problems and effects of the invention]
  First, a vehicle control device of a reference example before reaching the present invention will be described. This reference exampleThe vehicle control apparatus sets the maximum value of the resultant force that can be generated between each wheel of the vehicle and the road surface as the radius of the friction circle, and the resultant force that occurs between each wheel and the road surface The magnitude and direction of the generated force of each wheel is controlled so as not to exceed the force represented by the radius of the set friction circle.
[0007]
Note that the friction circle is a tire rolling with a certain slip angle when the maximum value of the resultant force of the longitudinal force Fx and the lateral force Fy generated on the contact surface is equal to a constant value F. , “(Fx squared) + (Fy squared) = (F squared)”, and the constant value F is the radius of the friction circle.
[0008]
  That meansReference exampleIn the vehicle control apparatus, since the determination reference value for determining that the grip force of the wheel is the limit is set as the radius of the two-dimensional friction circle, the force generated by the wheel in a specific direction is set. If Fa is detected, the maximum value Fbmax of force that can be generated in another direction different from that can be calculated as a value at which the resultant force of Fa and Fbmax becomes equal to the radius of the friction circle.
[0009]
For example, if the longitudinal force actually generated by the wheel is obtained based on a physical motion quantity such as the longitudinal acceleration of the vehicle body, the maximum value of the lateral force that can be generated orthogonal to the longitudinal force can be calculated. Conversely, if the lateral force actually generated by the wheel is determined based on the physical physical quantity such as the lateral acceleration and yaw rate of the vehicle body, the maximum value of the longitudinal force that can be generated orthogonally to the lateral force is calculated. Can do.
[0010]
  And since the magnitude | size of the force which a wheel can generate | occur | produce in a predetermined direction can be understood in this way, it becomes possible to adjust the actual generated force of a wheel within the range of the magnitude of the force. is there.
  For this reason,Reference exampleAccording to the vehicle control device of the present invention, the wheel grip is not performed after the wheel grip force exceeds the limit as in the conventional device, but the wheel grip force is maximized while the wheel grip force is generated. It is possible to control the vehicle running state as a target running state within a range not exceeding the force limit, and the limit of the entire vehicle can be made very high. Therefore, the running stability of the vehicle can be further improved.
[0011]
  Therefore, in the vehicle control device according to claim 1,Front, back, left and right fourEach wheel occurs between the road surfaceFront / rear force (front / rear force) and lateral force (lateral force)Generating force adjusting means for changing the size of each wheel, and the friction circle setting means determines the maximum value of the resultant force of each wheel that can be generated between each wheel and the road surface, for each wheel. Set the radius of the friction circle.
[0012]
  Then, the traveling state detection means detects the physical movement quantity of the vehicle body generated as the vehicle travels, and the generated force calculation means determines each wheel from the physical movement quantity detected by the traveling state detection means.DepartAliveLongitudinal force and lateral forceThe size of is calculated.
  Further, the margin calculation means is calculated for each wheel by the friction circle radius set by the friction circle setting means and the generated force calculation means.Longitudinal force and lateral forceBased on the size of each wheelAddedCan be generatedLongitudinal force and lateral forceCalculate the margin of.
[0013]
  Further, the target setting means sets a target value of the physical exercise quantity. Then, the additional force setting means causes the exercise physical quantity detected by the traveling state detection means to be the target value set by the target setting means.The front additional lateral force that is the total lateral force that must be generated by the addition of both front wheels, the rear additional lateral force that is the total lateral force that must be generated by the addition of both rear wheels, and four wheels In addition to calculating the additional vehicle longitudinal force, which is the total longitudinal force that must be generated in addition, additional force calculation processing is performed.Calculated forceEachDistribute to wheelsFor the distribution process.
Furthermore, as the distribution process,
Ratio of margin of lateral force between the left front wheel and right front wheel (hereinafter referred to as “first ratio”) and ratio of margin of lateral force between the left rear wheel and right rear wheel (hereinafter referred to as “second ratio”). And a marginal force addition ratio indicating that 10% of the front additional lateral force and the rear additional lateral force calculated in the additional force calculation process can be actually added is represented by 100% by the margin calculation means. A first process for calculating from the calculated margin of lateral force of each wheel;
If the lateral force addition possibility ratio is 1 or less, each value obtained by multiplying each of the front additional lateral force and rear additional lateral force calculated by the additional force calculation process by the lateral force addition possibility ratio is added to the distribution target front. If the lateral force and the rear additional lateral force are greater than 1, then the front additional lateral force and the rear additional lateral force calculated by the additional force calculation process are directly used as the front additional lateral to be distributed. A second process for force and rear additional lateral force;
The front additional lateral force to be distributed is distributed between the left front wheel and the right front wheel at the first ratio, and the rear additional lateral force to be distributed is distributed between the left rear wheel and the right rear wheel at the second ratio. A third process of allocating to
The ratio of the margin of front / rear force between the front wheels and the rear wheels (hereinafter referred to as the third ratio) and the percentage of the additional vehicle front / rear force calculated by the additional force calculation process can be actually increased by 10%. A fourth process of calculating a longitudinal force addition possible ratio shown as 1 from the margin of the longitudinal force of each wheel calculated by the margin calculating means;
If the longitudinal force addition possibility ratio is 1 or less, a value obtained by multiplying the additional vehicle longitudinal force calculated by the additional force calculation process by the longitudinal force addition possibility ratio is set as an additional vehicle longitudinal force to be distributed, and the longitudinal force addition is performed. If the possible ratio is greater than 1, a fifth process in which the additional vehicle longitudinal force calculated in the additional force calculation process is directly used as an additional vehicle longitudinal force to be distributed;
Half of the additional vehicle longitudinal force to be distributed is distributed to the left front wheel and the left rear wheel at the third ratio, and the other half of the additional vehicle longitudinal force to be allocated is to the right at the third ratio. And a sixth process of allocating to the front wheel and the right rear wheel.
[0014]
  And each wheel is added by the additional force setting means.DistributionThe drive control means operates the generated force adjusting means so that the generated force is additionally generated. The addition includes not only positive addition but also negative addition.
  That is, in the vehicle control device according to claim 1, a plurality of directions in which the magnitude of the generated force of each wheel can be changed by the generated force adjusting means.(Front-back direction and horizontal direction)For each wheel, the magnitude of the force actually generated by each wheel is obtained, and from the magnitude of the obtained force and the radius of the friction circle set by the friction circle setting means, each wheelAddedCan be generatedLongitudinal force and lateral forceSeeking a margin of And within the margin, each wheelLongitudinal force and lateral forceBy adding (positive addition or negative addition), the physical physical quantity of the vehicle body is set to the target value, and the resultant force generated by each wheel with the road surface is set to the friction circle setting. The magnitude and direction of the generated force of each wheel is controlled so as not to exceed the force represented by the radius of the friction circle set by the means.
[0015]
For this reason, as described above, it is possible to control the vehicle traveling state to the target traveling state by making the most of the gripping force that can be generated by the wheels, thereby further improving the traveling stability of the vehicle. .
The target setting means obtains the target yaw rate and lateral acceleration to be generated in the vehicle body from the steering operation angle and vehicle speed by the vehicle driver, and also determines the vehicle body from the operation amount of the accelerator pedal and brake pedal by the driver. The longitudinal acceleration of the target to be generated in the vehicle is obtained, and the obtained yaw rate, lateral acceleration, and longitudinal acceleration are set as the target values of the physical physical quantities of the vehicle body.
[0016]
In addition, when a person does not drive the vehicle but automatically steers the vehicle according to an external command, the target setting means includes the target yaw rate, lateral acceleration, and longitudinal acceleration that should be generated in the vehicle body. Information may be input from the outside, and the input information may be set as a target value of the physical exercise quantity.
[0017]
  on the other hand, DepartureThe vitality adjusting means is claimed in claim2By adjusting the braking force and driving force applied to each wheel and the steering angle of each wheel, the front-rear force (front-rear force) and the lateral force (lateral force) of each wheel are adjusted. It can be configured to change. And if it does in this way, an apparatus structure can be simplified.
[0018]
  Next, the claim3The vehicle control device according to claim 1 is the above-described claim 1., 2In addition to the apparatus described in (1), target correction means is additionally provided. Whether the target correction means can be realized by the force represented by the radius of the friction circle of each wheel set by the friction circle setting means, in which the target value of the physical movement quantity of the vehicle body set by the target setting means is set. Whether or not the total of forces in a specific direction that should be generated by a plurality of specific wheels to generate a physical physical quantity of the target value in the vehicle body (hereinafter referred to as a necessary value), and a friction circle setting means for the specific wheels Judgment is made by comparing the total force (hereinafter referred to as the limit value) represented by the radius of the friction circle set in accordance with the above, and the target value is realized because the limit value is not greater than the required value. When it is determined that the target value is not possible, the target value is corrected to a value at which the limit value is larger than the necessary value and determined to be realizable by the determination.
[0019]
According to this vehicle control device, when the target value of the physical movement quantity of the vehicle body set by the target setting means is extremely large, the target value is corrected to a value that can be realized by the force that can be generated by each wheel. Therefore, it is possible to reliably prevent the vehicle from suddenly exceeding the limit.
[0020]
In particular, when the target setting means is configured to set the target value based on the steering operation angle or the vehicle speed by the vehicle driver, even if the driver operates the steering wheel suddenly and greatly during high speed traveling. The target value used for the control is corrected, so that the running stability of the vehicle can be reliably maintained.
[0021]
  Where the claim4As described in claim 1 to claim 13In the vehicle control apparatus, a load detection means for detecting a load (vertical load) applied to each wheel is provided, and the friction circle setting means increases the radius of the friction circle as the load detected by the load detection means increases. If it is configured to set the value to a large value, a greater effect can be obtained.
[0022]
In other words, the grip force that can be generated by the tire (the maximum value of the resultant force that can be generated) increases according to the load. Therefore, when the load applied to the wheel is detected and the detected value is larger, the friction becomes larger. If the radius of the circle is set to a large value, the margin of force that can be generated by each wheel can be calculated more accurately, and the grip force that can be generated by the wheel can be utilized more reliably.
[0023]
  Claims5As described in claim 1 to claim 14In the vehicle control apparatus, a camber angle detecting means for detecting a ground camber angle of each wheel (that is, an angle formed between a tire center and a line perpendicular to the ground when viewed from the front of the vehicle) is provided, and the friction circle setting means has a camber angle. You may comprise so that the radius of the said friction circle may be set to a large value, so that the ground camber angle detected by the detection means is near 0 degree.
[0024]
That is, the grip force that can be generated by the tire is the maximum when the ground camber angle is 0 degree, and becomes smaller as the ground camber angle is away from 0 degree, so the actual ground camber angle of each wheel is detected, Even if the friction circle radius is set to a larger value as the value is closer to 0 degrees, the margin of force that can be generated by each wheel can be calculated more accurately, and the wheel can be generated. Grip power can be utilized more reliably.
[0025]
  Furthermore, when the radius of the friction circle is set according to the ground camber angle of the wheel,6The camber angle control means is additionally provided as described in the above, and the camber angle control means specifies a wheel having no margin calculated by the margin calculation means, and sets the ground camber angle of the identified wheel to 0. A greater effect can be obtained if the adjustment is made to approach the degree.
[0026]
That is, by adjusting the ground camber angle of a wheel that is considered to be no longer able to generate additional force, the grip force that can be generated by that wheel actually increases and is set for that wheel. Therefore, the radius of friction circle for control is also increased, so that the performance of the tire mounted on the wheel can be utilized to the maximum.
[0027]
  On the other hand, the friction circle setting means includes not only the wheel load and ground camber angle, but also claims7And claims8As described above, the radius of the friction circle can be set according to the friction coefficient of the road surface and the grip performance level of the tire mounted on the wheel.
[0028]
  That is, the claim7In the vehicle control device according to claim 1, the above claims 1 to 3.6The apparatus includes a friction coefficient detecting means for detecting a friction coefficient of the road surface of the vehicle, and the friction circle setting means increases the radius of the friction circle as the friction coefficient detected by the friction coefficient detecting means increases. Set to a larger value. Claims8In the vehicle control device according to claim 1, the above claims 1 to 3.7The apparatus includes tire determination means for detecting a grip performance level of a tire mounted on each wheel, and the friction circle setting means is more likely to have a higher tire grip performance level by the tire determination means. The radius of the friction circle is set to a large value.
[0029]
And even if it is configured to set the radius of the friction circle according to the friction coefficient of the road surface and the grip performance level of the tire in this way, the margin of force that can be generated by each wheel can be calculated more accurately. And the grip force that the wheel can generate can be utilized more reliably.
[0030]
  Of course, the radius of the friction circle is detected by detecting all or two or more of the load applied to each wheel, the ground camber angle of each wheel, the friction coefficient of the road surface, and the grip performance level of the tire. If this is configured, the frictional circle radius of each wheel can be set more accurately, and the control accuracy can be further improved..
On the other hand, for example, the running state detection unit can be configured to detect the yaw rate as an exercise physical quantity, and the target setting unit can set the target value of the yaw rate. Further, for example, the traveling state detection unit can be configured to detect lateral acceleration as an exercise physical quantity, and the target setting unit can set a target value of the lateral acceleration.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. Needless to say, the embodiments of the present invention are not limited to the following, and can take various forms as long as they belong to the technical scope of the present invention. In the following description, the force generated by a wheel, such as the longitudinal force of the wheel (front / rear direction force) and lateral force (lateral force), refers to the force generated by the tire attached to the wheel. pointing.
[0032]
First, FIG. 1 is a schematic configuration diagram showing the overall configuration of a vehicle control system according to an embodiment to which the present invention is applied. (A) shows a system of sensors, and (B) shows a system of actuators. ing.
As shown in FIG. 1 (A), for each wheel of the vehicle (right front wheel 2FR, left front wheel 2FL, right rear wheel 2RR, left rear wheel 2RL), the rotational speed of the wheel (hereinafter referred to as wheel speed) is detected. Wheel speed sensors 4FR, 4FL, 4RR, 4RL and height sensors 5FR, 5FL, 5RR, 5RL for detecting the vertical distance (hereinafter referred to as height) from the wheel center to the vehicle body that fluctuates with changes in the suspension stroke. Are provided.
[0033]
In the description of the present embodiment, the alphabets “FR”, “FL”, “RR”, and “RL” correspond to the right front wheel 2FR, the left front wheel 2FL, the right rear wheel 2RR, and the left rear wheel 2RL, respectively. It is a thing.
Further, the vehicle includes a lateral G sensor 6 for detecting a lateral acceleration (hereinafter referred to as lateral G) of the vehicle body, a yaw rate sensor 8 for detecting the yaw rate of the vehicle body, and a longitudinal acceleration (hereinafter referred to as longitudinal force) of the vehicle body. G) 10 for detecting G), a steering angle sensor 12 for detecting a steering operation angle (hereinafter referred to as a steering angle) operated by the driver, and a foot brake is depressed by the driver. The brake switch 13 which is turned on when the vehicle is depressed, the brake pedal force sensor 16 for detecting the foot brake pedal force (hereinafter referred to as the brake pedal force) by the driver, and the engine according to the accelerator pedal stepping amount by the driver. For detecting the opening of the throttle valve (hereinafter referred to as the accelerator opening) that adjusts the amount of intake air And opening sensor 18 is provided.
[0034]
Signals from the sensors and switches are input to an electronic control unit (hereinafter referred to as ECU) 20.
On the other hand, as shown in FIG. 1 (B), each wheel 2FR, 2FL, 2RR, 2RL has a toe control actuator 22FR, 22FL, 22RR, 22RL for adjusting the toe angle of the wheel and a camber angle of the wheel. Camber control actuators 24FR, 24FL, 24RR, and 24RL for adjustment are provided, respectively.
[0035]
The vehicle further includes a brake control actuator 28 for adjusting the brake hydraulic pressure applied to the brake devices 26FR, 26FL, 26RR, 26RL of the wheels 2FR, 2FL, 2RR, 2RL, an accelerator opening (a throttle valve opening). ) And an accelerator control actuator 30 for increasing / decreasing the engine output.
[0036]
Further, the vehicle of this embodiment is a four-wheel drive vehicle in which all wheels 2FR, 2FL, 2RR, 2RL are drive wheels, and although not particularly shown, torque output from the engine via a transmission. Is distributed to the drive shaft for the front wheels and the drive shaft for the rear wheels by the center differential gear, and the torque of the drive shaft for the front wheels is distributed to each of the front wheels 2FR and 2FL by the front differential gear. The torque of the drive shaft for the rear wheels is distributed to each of the rear wheels 2RR and 2RL by the rear differential gear.
[0037]
As shown in FIG. 1B, the vehicle has a center differential for adjusting the ratio of torque distributed between the front wheel drive shaft and the rear wheel drive shaft by the center differential gear. A control actuator 32C, a front differential control actuator 32F for adjusting the ratio of torque distributed to each of the front wheels 2FR and 2FL by the front differential gear, and each of the rear wheels 2RR and 2RL by the rear differential gear. A rear differential control actuator 32R for adjusting the proportion of torque to be distributed is provided.
[0038]
In such a vehicle according to the present embodiment, the ECU 20 sequentially executes each process shown in FIG. 2 periodically (for example, every 8 ms), and based on signals from the respective sensors and switches, In addition to detecting the driving state, an ideal target driving state is determined, and each of the wheels 2FR, 2FL, 2RR, 2RL is controlled with the road surface by controlling the actuators so that the actual driving state becomes the target driving state. The force generated between them is changed.
[0039]
In particular, the ECU 20 determines the maximum value of the resultant force that can be generated by each wheel 2FR, 2FL, 2RR, 2RL as the radius of the friction circle (the circle having the maximum value of the resultant force of the tire longitudinal force and lateral force as a radius). In order to achieve the target running state within the range where the grip force of each wheel does not exceed the limit, the direction and amount of the addition / decrease of the generated force of each wheel 2FR, 2FL, 2RR, 2RL are optimally distributed. ing.
[0040]
Therefore, the process executed by the ECU 20 will be specifically described below with reference to the drawings.
First, FIG. 2 is a flowchart showing the entire process executed by the ECU 20. Note that “constants K1 to K3”, “FR static load, FL static load, RR static load, RL static load”, “vehicle weight (vehicle weight)”, “moment constant”, “ "Center-of-gravity rear tire distance", "Center-of-gravity front tire distance", "Wheel base", "Front tread", "Rear tread", and "Gear ratio" are constants based on the specifications of the vehicle, and these are constants in the ECU 20. Are stored in advance in a ROM (not shown) as data.
[0041]
On the other hand, the ECU 20 periodically performs a detection process (not shown) to thereby obtain a signal from the lateral G sensor 6, the yaw rate sensor 8, the front / rear G sensor 10, the steering angle sensor 12, the brake pedal force sensor 16, and the accelerator opening sensor 18. Based on each signal, the lateral G, yaw rate, front / rear G, steering angle, brake force, and accelerator opening of the vehicle body are detected, and each wheel 2FR is detected based on the signals from the height sensors 5FR, 5FL, 5RR, 5RL. , 2FL, 2RR, 2RL, the height (vertical distance from the center of each wheel to the vehicle body) is detected. Further, the ECU 20 detects the vehicle speed by executing the detection process, for example, by averaging the wheel speeds detected based on the signals from the wheel speed sensors 4FR, 4FL, 4RR, 4RL. The lateral G and yaw rate detected by this detection process are used in each process of FIG.
[0042]
Further, in the processing described below, for the longitudinal G of the vehicle body and the longitudinal force of the wheel, the deceleration direction is positive and the acceleration direction is negative, and for the lateral G of the vehicle body and the yaw rate and the lateral force of the wheel, the right direction is Positive, left direction is negative. The steering angle has a positive right angle from the center position and a negative left angle from the center position.
[0043]
As shown in FIG. 2, the ECU 20 first calculates four loads for each wheel 2FR, 2FL, 2RR, 2RL at the first step (hereinafter simply referred to as “S”) 10. Execute load calculation processing.
Then, as shown in FIG. 3, when the ECU 20 starts executing the four-wheel load calculation process, first, in S100, the front and rear G of the vehicle body detected based on the signal from the front and rear G sensor 10 is input, and then in S110. Then, by multiplying the inputted front and rear G by a constant K1, a load fluctuation amount 1 (= front and rear G × constant K1) which is a fluctuation amount of the load between the front and rear wheels is calculated.
[0044]
Next, in S120, the lateral G of the vehicle body detected based on the signal from the lateral G sensor 6 is input, and in the subsequent S130, the input lateral G is multiplied by a constant K2 to thereby calculate the load between the left and right front wheels. A load fluctuation amount 2F (= lateral G × constant K2), which is a fluctuation amount, is calculated, and further in S140, the input lateral G is multiplied by the constant K3 to obtain the fluctuation amount of the load between the left and right rear wheels. A load fluctuation amount 2R (= lateral G × constant K3) is calculated.
[0045]
The constants K1 to K3 represent load fluctuation amounts per unit acceleration, and are set according to the spring rate of the suspension and the vehicle weight.
Then, in each of S150 to S180, based on the following formulas 1 to 4, the FR wheel load that is the load of the right front wheel 2FR, the FL wheel load that is the load of the left front wheel 2FL, and the right rear wheel 2RR The RR wheel load that is the load of RL and the RL wheel load that is the load of the left rear wheel 2RL are respectively calculated. It should be noted that “FR static load”, “FL static load”, “RR static load”, and “RL static load” in Formulas 1 to 4 represent the wheels 2FR, 2FL, 2RR, It is a load applied to 2RL, and is set according to the weight balance of the vehicle.
[0046]
[Expression 1]
FR wheel load = FR static load + load fluctuation 1 + load fluctuation 2F Equation 1
[0047]
[Expression 2]
FL wheel load = FL static load + load fluctuation 1-load fluctuation 2F Equation 2
[0048]
[Equation 3]
RR wheel load = RR static load−load fluctuation 1 + load fluctuation 2R Equation 3
[0049]
[Expression 4]
RL wheel load = RL static load−load variation 1−load variation 2R Equation 4
And ECU20 will complete | finish the said 4 wheel load calculation process, if FR wheel load-RL wheel load (namely, load currently applied to each wheel 2FR, 2FL, 2RR, 2RL) is calculated by said S150-S180. Then, the process proceeds to S15 in FIG. 2, and the lateral force calculation process shown in FIG. 4 is executed in S15.
[0050]
This lateral force calculation processing is performed in the vehicle lateral force that is the total lateral force of the entire vehicle, the front lateral force that is the total lateral force of both front wheels 2FR and 2FL, and the rear lateral force that is the total lateral force of both rear wheels 2RR and 2RL. This is a process for calculating force.
As shown in FIG. 4, when the ECU 20 starts executing the lateral force calculation process, first, in S200, the lateral G of the vehicle body is input, and in the subsequent S210, the input lateral G is multiplied by the vehicle weight. The vehicle body lateral force (= lateral G × vehicle weight) is calculated.
[0051]
In the subsequent S220, the yaw rate of the vehicle body detected based on the signal from the yaw rate sensor 8 is input, and in the next S230, the yaw angular acceleration of the vehicle body is calculated by differentiating the input yaw rate. Further, in subsequent S240, the yaw moment of the vehicle body (= yaw angular acceleration × moment constant) is calculated by multiplying the yaw angular acceleration calculated in S230 by the moment constant stored in advance.
[0052]
When the vehicle body lateral force and yaw moment are calculated in this way, in the following S250, the front lateral force, which is the total lateral force of both front wheels 2FR, 2FL, and both rear wheels 2RR, The rear lateral force that is the total lateral force of 2RL is calculated.
In the following formula, “/” indicates division. The "center of gravity front tire distance" is the horizontal distance between the center of gravity of the vehicle and the axle center of the front wheels 2FR and 2FL, and the "center of gravity rear tire distance" is the center of gravity of the vehicle and the axle center of the rear wheels 2RR and 2RL. Is the horizontal distance.
[0053]
[Equation 5]
Front lateral force = (body lateral force x center of gravity rear tire distance + yaw moment) / wheel base… Formula 5
[0054]
[Formula 6]
Rear lateral force = (vehicle lateral force x center of gravity front-to-tire distance-yaw moment) / wheel base… Formula 6
When the ECU 20 calculates the front lateral force and the rear lateral force in S250, the ECU 20 ends the lateral force calculation process, and then proceeds to S20 in FIG. 2, where the longitudinal force calculation shown in FIG. Execute the process.
[0055]
This longitudinal force calculation process is the vehicle body longitudinal force that is the total longitudinal force of the entire vehicle, the front longitudinal force that is the total longitudinal force of both front wheels 2FR and 2FL, and the total longitudinal force of both rear wheels 2RR and 2RL. This is a process for calculating the rear longitudinal force.
As shown in FIG. 5, when the ECU 20 starts executing the longitudinal force calculation process, it is first determined in S300 whether or not the brake switch 13 is currently on. If it is determined that the brake switch 13 is on, the process proceeds to S310, and the “front-rear G vs. front-rear force map during foot brake” is read from the ROM. If it is determined in S300 that the brake switch 13 is not turned on, the process proceeds to S320, and the “front-rear G vs. front-rear force map during non-foot brake” is read from the ROM.
[0056]
Here, the “front / rear G vs. front / rear force map during foot brake” read in S310 is the front front / rear force against the front / rear G when the foot brake is stepped on by the driver (the total front / rear force of both front wheels 2FR, 2FL). ) And the rear longitudinal force (the total longitudinal force of both rear wheels 2RR and 2RL) with respect to the longitudinal G, respectively. The front longitudinal force with respect to the longitudinal G is stored as shown in the upper left column of FIG. 6, and the rear longitudinal force with respect to the longitudinal G is stored as shown in the lower left column of FIG.
[0057]
As shown in the upper left column and the lower left column in FIG. 6, in the “front / rear G vs. front / rear force map during foot brake”, when the front / rear G is positive (deceleration direction), the front front / rear force is greater than the rear front / rear force. The force is set to be larger. This is because the characteristics of the proportional valve provided in the brake system are such that the braking force of the front wheels 2FR and 2FL is greater than the braking force of the rear wheels 2RR and 2RL when the foot brake is stepped on with the same force ( For example, it is set to 7: 3). Further, since the vehicle according to the present embodiment is a four-wheel drive vehicle, when the front-rear G is negative (acceleration direction), both the front front-rear force and the rear front-rear force are set negative (acceleration direction). ing. The ratio between the front longitudinal force and the rear longitudinal force corresponding to the same longitudinal G is set according to the current torque distribution of the center differential gear adjusted by the center differential control actuator 32C.
[0058]
On the other hand, the “front-rear G vs. front-rear force map during non-footbrake” read in S320 shows the front front-rear force against the front-rear G and the rear front-rear force against the front-rear G when the driver does not step on the footbrake. These are data maps stored respectively. The front longitudinal force with respect to the longitudinal G is stored as shown in the upper right column of FIG. 6, and the rear longitudinal force with respect to the longitudinal G is stored as shown in the lower right column of FIG.
[0059]
Since the vehicle of this embodiment is a four-wheel drive vehicle, engine brakes are applied to both the front wheels 2FR, 2FL and the rear wheels 2RR, 2RL. Therefore, as shown in the upper right column and lower right column in FIG. 6, the front / rear G vs. front / rear force map during non-footbrake is independent of the front / rear G (deceleration / acceleration) regardless of whether the front / rear G is positive or negative. Both the force and the force are set to change according to the front and rear G. The ratio between the front longitudinal force and the rear longitudinal force corresponding to the same longitudinal G is set according to the current torque distribution of the center differential gear.
[0060]
Next, after executing one of S310 and S320, the process proceeds to S330, and the current front and rear G of the vehicle body is input. Then, in subsequent S340, the front front / rear force and the rear front / rear force corresponding to the input front / rear G are read in any one of S310 and S320 ("front / rear G vs. front / rear force map during foot brake" or " Based on the front / rear G vs. front / rear force map during non-footbrake "), it is calculated by interpolation. Further, in subsequent S350, the vehicle longitudinal force (= front / rear G × vehicle weight), which is the total longitudinal force of the entire vehicle, is calculated by multiplying the current longitudinal G input in S330 by the vehicle weight.
[0061]
When the ECU 20 calculates the vehicle body longitudinal force in S350, the ECU 20 ends the longitudinal force calculation process, and then proceeds to S25 in FIG. 2, where the road surface μ estimation calculation shown in FIGS. 7 and 8 is performed. Execute the process. FIG. 7 shows the first half of the road surface μ estimation calculation process, and FIG. 8 shows the second half thereof.
[0062]
This road surface μ estimation calculation process is a process for estimating the friction coefficient of the road surface on which the vehicle is currently traveling.
As shown in FIG. 7, when the ECU 20 starts executing the road surface μ estimation calculation process, first, in S400, the steering angle detected based on the signal from the steering angle sensor 12 is input, and in S405, the wheel speed is detected. A vehicle speed detected based on signals from the sensors 4FR, 4FL, 4RR, 4RL is input.
[0063]
In subsequent S410, the target yaw rate is calculated based on the following equation 7, and in subsequent S415, the target lateral G (= target yaw rate × vehicle speed) is obtained by multiplying the target yaw rate by the vehicle speed input in S405. calculate.
The target yaw rate and the target lateral G are the ideal yaw rate and lateral G of the vehicle body that can be considered from the actual steering angle and vehicle speed, respectively. Further, in the following formula including the following formula 7, the “gear ratio” is the gear ratio of the steering box of the vehicle. Therefore, the “steering angle / gear ratio” is the front wheel 2FR generated by the steering operation. , 2FL rudder angle (toe angle) is shown. Furthermore, the “target stability factor” is a constant set so that the calculated target yaw rate becomes a value that does not make the driver feel uncomfortable as the behavior of the vehicle.
[0064]
[Expression 7]
Target yaw rate = (steering angle / gear ratio × vehicle speed / wheel base) / (1 + target stability factor × vehicle speed × vehicle speed)
When the target yaw rate and the target lateral G are calculated in this way, the actual yaw rate is input in the subsequent S420, and in the subsequent S425, the yaw rate that is the difference between the input actual yaw rate and the calculated target yaw rate. Calculate the error.
[0065]
When the target yaw rate is positive (clockwise), the yaw rate error is calculated by subtracting the target yaw rate from the actual yaw rate as shown in the following equation 8 as shown in FIG. When the yaw rate is negative (counterclockwise), the value obtained by subtracting the target yaw rate from the actual yaw rate is further multiplied by “−1” as shown in Equation 9 below. That is, regardless of the turning direction of the vehicle, the yaw rate error is positive if the actual yaw rate is too large relative to the target yaw rate, and conversely if the value is negative, the actual yaw rate is the target yaw rate. Indicates too small for yaw rate.
[0066]
[Equation 8]
Yaw rate error = yaw rate-target yaw rate (8)
[0067]
[Equation 9]
Yaw rate error = − (yaw rate−target yaw rate) Equation 9
When the yaw rate error is calculated in this way, the process proceeds to S430, and it is determined whether or not the calculated yaw rate error is larger than a predetermined value K4 (> 0) set to a positive value. When the yaw rate error is larger than the predetermined value K4, the process proceeds to S435, and “1” indicating that the yaw rate is excessive is set in the yaw rate excessive flag indicating whether or not the actual yaw rate is excessive. Conversely, if the yaw rate error is not greater than the predetermined value K4, the process proceeds to S440, and the yaw rate excessive flag is set to “0”.
[0068]
Then, when “1” or “0” is set to the yaw rate excessive flag in S435 or S440, the process proceeds to S445, and this time, the yaw rate error is set to be less than a predetermined value K5 (<0) set to a negative value. It is determined whether or not it is small. If the yaw rate error is smaller than the predetermined value K5, the process proceeds to S450, and “1” indicating that the yaw rate is too low is set in the yaw rate under flag indicating whether or not the actual yaw rate is too low. Conversely, if the yaw rate error is not smaller than the predetermined value K5, the process proceeds to S455, and the yaw rate under flag is set to “0”.
[0069]
As described above, when “1” or “0” is set to the under yaw rate flag in S450 or S455, the process proceeds to S460. Then, the lateral G of the vehicle body is input, and a lateral G error which is a difference between the input actual lateral G and the target lateral G calculated in S415 is calculated.
[0070]
This lateral G error is calculated by subtracting the target lateral G from the actual lateral G as shown in the following equation 10 as shown in FIG. 7 when the target lateral G is positive (rightward). However, when the target lateral G is negative (leftward), the value obtained by subtracting the target lateral G from the actual lateral G is further multiplied by “−1” as shown in the following formula 11. The That is, the lateral G error is the same as the yaw rate error, if the value is positive regardless of the turning direction of the vehicle, the actual lateral G is too large with respect to the target lateral G, and conversely, the value is negative. If so, it indicates that the actual lateral G is too small with respect to the target lateral G.
[0071]
[Expression 10]
Lateral G error = Lateral G-Target lateral G ... Formula 10
[0072]
## EQU11 ##
Horizontal G error = − (Horizontal G−Target horizontal G) Equation 11
When the lateral G error is calculated in this way, the process proceeds to S465, and it is determined whether or not the calculated lateral G error is larger than a predetermined value K6 (> 0) set to a positive value. If the lateral G error is larger than the predetermined value K6, the process proceeds to S470, and the lateral G excessive flag indicating whether the actual lateral G is excessive is set to “1” indicating that it is excessive. set. Conversely, if the lateral G error is not greater than the predetermined value K6, the process proceeds to S475, and the lateral G excessive flag is set to “0”.
[0073]
Then, when “1” or “0” is set to the lateral G excess flag in S470 or S475, the process proceeds to S480, and this time, the predetermined value K7 (<0) in which the lateral G error is set to a negative value. Or less. If the lateral G error is smaller than the predetermined value K7, the process proceeds to S485, and the lateral G under flag indicating whether or not the actual lateral G is excessive is set to “1” indicating that it is excessive. set. Conversely, if the lateral G error is not smaller than the predetermined value K7, the process proceeds to S490, and the lateral G under flag is set to “0”.
[0074]
When the lateral G under flag is set to “1” or “0” in S485 or S490 as described above, the process proceeds to S495 shown in FIG. 8 to determine whether or not the yaw rate under flag is “1”. If it is “1”, it is determined in subsequent S500 whether or not the lateral G excessive flag is “1”. If the lateral G excessive flag is not “1”, that is, if the yaw rate excessive flag is “1” and the lateral G excessive flag is “0”, the vehicle is in an understeer state, and the front wheels 2FR, 2FL It is determined that the grip force of the tire is the limit, and the process proceeds to S505, where “1” indicating that the grip force of the tire of the front wheels 2FR and 2FL is the limit is set in the front wheel limit determination flag.
[0075]
On the other hand, if it is determined in S495 that the yaw rate under flag is not “1”, or if it is determined in S500 that the lateral G over flag is “1”, the process proceeds to S510 to determine the front wheel limit. Set “0” to the flag.
Then, when “1” or “0” is set to the front wheel limit flag in S505 or S510, the process proceeds to S515, and it is determined whether the excessive yaw rate flag is “1”. If the excessive yaw rate flag is “1”, it is determined that the vehicle is in an oversteer state and the grip force of the tires of the rear wheels 2RR and 2RL is the limit, and the process proceeds to S520, where the rear wheel limit determination flag is set. Then, “1” indicating that the grip force of the tires of the rear wheels 2RR and 2RL is the limit is set.
[0076]
On the other hand, if it is determined in S515 that the excessive yaw rate flag is not “1”, the process proceeds to S525, and “0” is set to the rear wheel limit determination flag.
As described above, when “1” or “0” is set to the rear wheel limit flag in S520 or S525, the process proceeds to S530, and it is determined whether or not the front wheel limit flag is “1”.
[0077]
If the front wheel limit flag is “1”, the process proceeds to S535, and the front longitudinal force calculated in S340 of the longitudinal force calculation process (FIG. 5) and the front lateral force calculated in S250 of the lateral force calculation process (FIG. 4). From the force, the front grip force, which is the total grip force of the tires of both front wheels 2FR and 2FL, is calculated based on the following equation (12). That is, the front grip force is calculated as the resultant force of the front longitudinal force and the front lateral force.
[0078]
[Expression 12]

[0079]
In the subsequent S540, from the front grip force calculated in S535 and the FR wheel load and the FL wheel load calculated in S150 and S160 of the four-wheel load calculation process (FIG. 3), Estimated μ, which is an estimated value of the friction coefficient of the road surface on which the vehicle is currently traveling, is calculated.
[0080]
[Formula 13]
Estimated μ = Front grip force / (FR wheel load + FL wheel load) Equation 13
That is, in S540, the road surface is obtained by dividing the grip force (front grip force) generated by the tires of both front wheels 2FR, 2FL by the load applied to both front wheels 2FR, 2FL (FR wheel load + FL wheel load). The coefficient of friction (estimated μ) is calculated.
[0081]
Then, the estimated μ is calculated in S540 as described above, or if it is determined in S530 that the front wheel limit flag is not “1”, the process proceeds to S545. In S545, it is determined whether or not the rear wheel limit flag is “1”. If the rear wheel limit flag is “1”, the process proceeds to the next S550, and S340 of the longitudinal force calculation process (FIG. 5). From the rear longitudinal force calculated in step 4 and the rear lateral force calculated in step S250 of the lateral force calculation process (FIG. 4), the rear is the total grip force of the tires of the two rear wheels 2RR and 2RL based on the following equation 14. Calculate the grip force. That is, the rear grip force is also calculated as a resultant force of the rear longitudinal force and the rear lateral force, similarly to the front grip force.
[0082]
[Expression 14]

[0083]
Then, in subsequent S555, from the rear grip force calculated in S550 and the RR wheel load and RL wheel load calculated in S170 and S180 of the four-wheel load calculation process (FIG. 3), Calculate the estimated μ.
[0084]
[Expression 15]
Estimated μ = Rear grip force / (RR wheel load + RL wheel load) Equation 15
That is, in S555, as in the case of S540 and Equation 13 described above, the grip force (rear grip force) generated by the tires of both rear wheels 2RR and 2RL is applied to the load applied to both rear wheels 2RR and 2RL. The friction coefficient (estimated μ) of the road surface is calculated by dividing by (RR wheel load + RL wheel load). Then, the road surface μ estimation calculation process ends.
[0085]
On the other hand, if it is determined in S545 that the rear wheel limit flag is not “1”, the road surface μ estimation calculation process is terminated without performing the processes of S550 and S555 for calculating the estimated μ. .
In this way, in the road surface μ estimation calculation process, the friction coefficient of the road surface (estimated μ) is calculated by dividing the tire grip force by the load applied to the tire for the wheel determined to have the limit of the tire grip force. ) Is calculated (S530 to S555). That is, the grip force generated when the tire reaches the limit is regarded as a dynamic friction force with the road surface, and the friction coefficient of the running road surface is calculated from the ratio of the grip force and the load at that time.
[0086]
Then, after completing the road surface μ estimation calculation process, the ECU 20 proceeds to S30 in FIG. 2, and calculates the slip angle (side slip angle) of each wheel 2FR, 2FL, 2RR, 2RL in S30. The four-wheel skid angle calculation process shown in FIG. 9 is executed.
As shown in FIG. 9, when the ECU 20 starts executing the four-wheel skid angle calculation process, first, the yaw rate and the lateral G of the vehicle are input in S600 and S610. In S620, the vehicle speed detected based on the signals from the wheel speed sensors 4FR, 4FL, 4RR, 4RL is input, and in S630, the steering angle detected based on the signal from the steering angle sensor 12 is input. Enter.
[0087]
In subsequent S640, the vehicle body side slip angular velocity is calculated based on the following Expression 16.
[0088]
[Expression 16]
Vehicle side slip angular velocity = −lateral G / vehicle speed + yaw rate Equation 16
When the vehicle side slip angular velocity is calculated in this way, in the next step S650, the calculated vehicle side slip angular velocity is integrated to calculate a vehicle side slip angle which is an angle formed by the direction of the vehicle body and the traveling direction of the vehicle body.
[0089]
In S660, based on the following equations 17 to 20, the FR skid angle that is the slip angle of the right front wheel 2FR, the FL skid angle that is the slip angle of the left front wheel 2FL, and the slip angle of the right rear wheel 2RR are calculated. And the RL skid angle, which is the slip angle of the left rear wheel 2RL, are calculated.
[0090]
The “FR toe variable angle”, “FL toe variable angle”, “RR toe variable angle”, and “RL toe variable angle” in Expressions 17 to 20 are respectively determined by the toe control actuators 22FR, 22FL, 22RR, and 22RL. The toe angle of each adjusted wheel 2FR, 2FL, 2RR, 2RL.
[0091]
[Expression 17]
FR skid angle = car body skid angle−yaw rate × center of gravity front tire distance / vehicle speed + steering angle / gear ratio + FR toe variable angle 17
[0092]
[Expression 18]
FL skid angle = car body skid angle-yaw rate x center of gravity distance between front tires / vehicle speed + steering angle / gear ratio + FL toe variable angle ... Formula 18
[0093]
[Equation 19]
RR skid angle = car body skid angle + yaw rate x center of gravity rear tire distance / vehicle speed + RR toe variable angle ...
[0094]
[Expression 20]
RL side slip angle = vehicle body side slip angle + yaw rate × center of gravity rear tire distance / vehicle speed + RL toe variable angle Equation 20
When the ECU 20 calculates the slip angle (side slip angle) of each wheel 2FR, 2FL, 2RR, 2RL in S660, the ECU 20 ends the four-wheel side slip angle calculation process, and then proceeds to S35 in FIG. In S35, the tire type determination calculation process shown in FIG. 10 for determining the grip performance level of the tire is executed.
[0095]
As shown in FIG. 10, when the ECU 20 starts executing the tire type determination calculation process, first, in S700, each wheel 2FR, 2FL, 2RR, 2RL calculated in S660 of the four-wheel skid angle calculation process (FIG. 9) is calculated. From the slip angle, a front side slip angle that is an average slip angle of the front wheels 2FR and 2FL and a rear side slip angle that is an average slip angle of the rear wheels 2RR and 2RL are calculated based on the following formulas 21 and 22.
[0096]
[Expression 21]
Front skid angle = (FR skid angle + FL skid angle) / 2 Equation 21
[0097]
[Expression 22]
Rear skid angle = (RR skid angle + RL skid angle) / 2
In subsequent S710, cornering of each front wheel 2FR, 2FL is based on the following equation 23 from the front lateral force calculated in S250 of the lateral force calculation process (FIG. 4) and the front skid angle calculated in S700. Calculate the front cornering power, which is the power.
[0098]
[Expression 23]
Front cornering power = Front lateral force / 2 / Front skid angle ... Formula 23
Similarly, in S720, each rear wheel 2RR, 2RL is calculated from the rear lateral force calculated in S250 of the lateral force calculation process (FIG. 4) and the rear side slip angle calculated in S700 based on the following equation 24. The rear cornering power that is the cornering power is calculated.
[0099]
[Expression 24]
Rear cornering power = rear side force / 2 / rear side slip angle ... Formula 24
In the present embodiment, as can be seen from Expressions 23 and 24, the front lateral force and the rear lateral force are divided by “2” to obtain the lateral force of each front wheel 2FR, 2FL and each rear wheel 2RR, 2RL. The cornering power is obtained by approximating each side force to the cornering force.
[0100]
In subsequent S730, it is determined whether or not the front skid angle calculated in S700 is smaller than a predetermined value S1, and if it is determined that the front skid angle is smaller than the predetermined value S1, the process proceeds to S740. In S740, it is determined whether or not the front cornering power calculated in S710 is smaller than a preset setting value CP1, and if it is determined that the front cornering power is smaller than the set value CP1, Proceeding to S750, the front low grip tire flag indicating whether or not the tire mounted on the front wheels 2FR and 2FL is a low grip tire indicates that the tire is a low grip tire (that is, a tire having low grip performance). 1 ”is set. Conversely, if it is determined in S740 that the front cornering power is not smaller than the set value CP1, the process proceeds to S760 and the front low grip tire flag is not a low grip tire (in other words, "0" indicating that the grip performance is a high grip tire.
[0101]
The predetermined value S1 used in the determination of S730 is a predetermined slip in a region where the cornering force and the slip angle are approximately proportional to each other (a region where the grip force of the tire is not a limit) in a standard tire mounted on the vehicle. The angle value is set, and this is the same for the predetermined value S2 used in the determination of S770 described later.
[0102]
Then, when one of S750 and S760 is executed and a value is set in the front low grip tire flag, the process proceeds to S770. If it is determined in S730 that the front skid angle is not smaller than the predetermined value S1, the process proceeds to S770 without executing the processes of S740 to S760.
[0103]
Next, in S770, it is determined whether or not the rear skid angle calculated in S700 is smaller than a predetermined value S2, and if it is determined that the rear skid angle is smaller than the predetermined value S2, the process proceeds to S780. Then, in S780, it is determined whether or not the rear cornering power calculated in S720 is smaller than the preset setting value CP2, and if it is determined that the rear cornering power is smaller than the set value CP2, Proceeding to S790, "1" indicating that the tire is a low grip tire is set in a rear low grip tire flag indicating whether or not the tire mounted on the rear wheels 2RR and 2RL is a low grip tire. Conversely, if it is determined in S780 that the rear cornering power is not smaller than the set value CP2, the process proceeds to S795, and the rear low grip tire flag is not a low grip tire (in other words, “0” indicating that the tire is a high grip tire). Then, when one of S790 and S795 is executed and a value is set in the rear low grip tire flag, the tire type determination calculation process is terminated.
[0104]
If it is determined in S770 that the rear skid angle is not smaller than the predetermined value S2, the tire type determination calculation process is terminated without executing the processes of S780 to S795.
That is, in this tire type determination calculation process, focusing on the fact that the cornering power of the tire becomes a value according to the grip performance of the tire itself regardless of the friction coefficient of the road surface, the front cornering power calculated in S710 and S720 and The level of the grip performance of the tire is determined according to the value of the rear cornering power.
[0105]
Only when the front skid angle, which is the slip angle of each front wheel 2FR, 2FL, is smaller than the predetermined value S1, the determination of S740 for the front tire is performed, and the rear skid, which is the slip angle of each rear wheel 2RR, 2RL, is made. Only when the angle is smaller than the predetermined value S2, the determination of S780 for the rear wheel tire is performed because the accurate cornering calculated when the front / rear skid angle is smaller than the predetermined values S1 and S2. This is because the grip performance of the tire can be determined based on the power.
[0106]
Next, when the tire type determination calculation process is completed, the ECU 20 proceeds to S40 of FIG. Then, in S40, the ground camber angle of each wheel 2FR, 2FL, 2RR, 2RL (that is, the angle between the tire center and a line perpendicular to the ground when viewed from the front of the vehicle) is shown in FIG. The camber angle calculation process is executed.
[0107]
As shown in FIG. 11, when the ECU 20 starts execution of the ground camber angle calculation process, first, in S800, the wheels 2FR, 2FL, respectively detected based on the signals from the height sensors 5FR, 5FL, 5RR, 5RL. 2RR, 2RL height (FR height, FL height, RR height, RL height) is input.
[0108]
In each of subsequent S810 and S820, a front roll angle that is a roll angle at the front wheel portion of the vehicle body and a rear roll angle that is a roll angle at the rear wheel portion of the vehicle body are respectively calculated based on the following equations 25 and 26. calculate. Note that “front tread” in Expression 25 is the distance in the vehicle width direction between the centers of contact surfaces with the road surfaces of the left and right front wheels 2FR and 2FL, and “rear tread” in Expression 26 is the distance between the left and right rear wheels 2RR and 2RL. It is the distance in the vehicle width direction between the centers of contact surfaces with the road surface.
[0109]
[Expression 25]
Front roll angle = tan^-1((FR height-FL height) / front tread)
[0110]
[Equation 26]
Rear roll angle = tan^-1((RR height-RL height) / rear tread)
In step S830, the “height vs. camber angle change map” is read from the ROM. As shown in FIG. 12, this “height vs. camber angle change map” stores the change in camber angle of the wheel (camber angle change) with respect to the height detected by the height sensors 5FR, 5FL, 5RR and 5RL. A data map is prepared for each wheel 2FR, 2FL, 2RR, 2RL.
[0111]
In subsequent S840, the camber angle change amount (FR camber angle change amount, FL camber) of each wheel 2FR, 2FL, 2RR, 2RL corresponding to the height of each wheel 2FR, 2FL, 2RR, 2RL input in S800 above. (Angle change amount, RR camber angle change amount, RL camber angle change amount) are calculated by interpolation or the like based on the “height vs. camber angle change amount map” read in S830.
[0112]
Further, in each of subsequent S850 to S880, the actual ground camber angle (FR ground camber angle, FL ground camber angle, RR ground) of each wheel 2FR, 2FL, 2RR, 2RL based on the following formulas 27-30 Camber angle, RL ground camber angle) is calculated, and then the ground camber angle calculation process is terminated.
[0113]
Note that “FR camber angle control amount”, “FL camber angle control amount”, “RR camber angle control amount”, and “RL camber angle control amount” in Expressions 27 to 30 are camber control actuators 24FR and 24FL, respectively. , 24RR, 24RL, the change in camber angle of each wheel 2FR, 2FL, 2RR, 2RL.
[0114]
[Expression 27]
FR ground camber angle = FR camber angle change amount + front roll angle + FR camber angle control amount Equation 27
[0115]
[Expression 28]
FL ground camber angle = FL camber angle change amount-front roll angle + FL camber angle control amount ... Equation 28
[0116]
[Expression 29]
RR ground camber angle = RR camber angle change amount + rear roll angle + RR camber angle control amount Equation 29
[0117]
[30]
RL ground camber angle = RL camber angle change amount−rear roll angle + RL camber angle control amount Equation 30
That is, in S850 to S880, a change in camber angle due to suspension stroke change (FR to RL camber angle change amount) and a change in camber angle due to rolling of the vehicle body (front roll angle and rear roll angle) The actual ground camber angle (FR) of each wheel 2FR, 2FL, 2RR, 2RL from the change in camber angle (FR to RL camber angle control amount) adjusted by the camber control actuators 24FR, 24FL, 24RR, 24RL. To RL ground camber angle).
[0118]
Then, when the ground camber angle calculation process is completed, the ECU 20 proceeds to S45 in FIG. 2 and executes the four-wheel friction circle estimation calculation process shown in FIG. 13 in S45.
This four-wheel friction circle estimation calculation process is a process for setting the maximum value of the resultant force that can be generated between the wheels 2FR, 2FL, 2RR, and 2RL with the road surface as the radius of the friction circle. is there.
[0119]
As shown in FIG. 13, when the ECU 20 starts executing the four-wheel friction circle estimation calculation process, first, in S900, the front low grip tire flag whose value is set in the tire type determination calculation process of FIG. 10 is “1”. It is determined whether or not. If it is determined that the front low grip tire flag is “1”, the process proceeds to S905, and the “load / friction circle map for low grip tires” is read from the ROM. If it is determined in S900 that the front low grip tire flag is not “1”, the process proceeds to S910, and the “load vs. friction circle map for high grip tire” is read from the ROM.
[0120]
Here, the “load / friction circle map for high grip tires” read in S910 is the size of the radius of the friction circle with respect to the load for a standard tire mounted on the vehicle, as shown by the solid line in FIG. This is a data map that stores (that is, the magnitude of the maximum grip force that can be generated), and is set such that the friction circle radius increases as the load increases. Similarly, the “load vs. friction circle map for low grip tires” read in S905 is a tire having a grip performance lower than that of a standard tire (for example, a studless tire for winter seasons), as indicated by a dashed line in FIG. Is a data map storing the size of the radius of the friction circle with respect to the load.
[0121]
As can be seen from FIG. 14, the value of the friction circle radius corresponding to the load of the same value in the “load vs. friction circle map for high grip tires” and the “load vs. friction circle map for low grip tires” is The “load vs. friction circle map for low grip tires” is set smaller.
[0122]
Next, after executing any one of the above S905 and S910, the process proceeds to S915, and the FR wheel load (the load of the right front wheel 2FR) and the FL wheel load (the left wheel) calculated by the four-wheel load calculation process of FIG. Load the load on the front wheel 2FL).
In the subsequent S920, the data of the friction circle radius corresponding to the read FR wheel load and FL wheel load is read in any one of S905 and S910 ("Load vs. friction circle map for low grip tires"). ”Or“ Load vs. friction circle map for high-grip tires ”), calculated by interpolation, etc., and the calculated friction circle radius corresponding to the right front wheel 2FR and the friction circle radius corresponding to the left front wheel 2FL, They are set as the FR friction circle basic value and the FL friction circle basic value, respectively.
[0123]
Next, the process proceeds to S925, and this time, it is determined whether or not the rear low grip tire flag whose value is set in the tire type determination calculation processing of FIG. 10 is “1”. If it is determined that the rear low-grip tire flag is “1”, the process proceeds to S930, and “load-friction circle map for low-grip tire” is read from the ROM as in the case of S905 described above. . Further, when it is determined in S925 that the rear low grip tire flag is not “1”, the process proceeds to S935 and, as in the case of S910 described above, the “load / friction for high grip tires” is read from the ROM. Read "Circle Map".
[0124]
Then, after either S930 or S935 is executed, the process proceeds to S940, and the RR wheel load (the load of the right rear wheel 2RR) and the RL wheel load (left) calculated in the four-wheel load calculation process of FIG. The load of the rear wheel 2RL) is read, and in S945, the friction circle radius corresponding to the read RR wheel load and the RL wheel load is interpolated based on the data map read in either S930 or S935. Calculate by Then, the calculated friction circle radius corresponding to the right rear wheel 2RR and the friction circle radius corresponding to the left rear wheel 2RL are set as the RR friction circle basic value and the RL friction circle basic value, respectively.
[0125]
When the frictional circle basic values (FR to RL frictional circle basic values) of the respective wheels 2FR, 2FL, 2RR, and 2RL are obtained in this way, the process proceeds to S950, and is calculated by the road surface μ estimation calculation process of FIGS. The latest estimated μ (the estimated value of the friction coefficient of the road surface) is read.
In subsequent S955, based on the following equations 31 to 34, the FR friction circle μ correction value, the FL friction circle μ correction value, and the RR friction circle, which are correction values based on the estimated μ of each friction circle basic value. The μ correction value and the RL friction circle μ correction value are calculated.
[0126]
[31]
FR friction circle μ correction value = FR friction circle basic value × estimated μ Equation 31
[0127]
[Expression 32]
FL friction circle μ correction value = FL friction circle basic value × estimated μ Equation 32
[0128]
[Expression 33]
RR friction circle μ correction value = RR friction circle basic value × estimated μ Equation 33
[0129]
[Expression 34]
RL friction circle μ correction value = RL friction circle basic value × estimated μ Equation 34
Next, in subsequent S960, the “ground camber angle vs. friction circle reduction coefficient map” is read from the ROM. As shown in FIG. 15, this “ground camber angle vs. friction circle reduction coefficient map” stores the relationship between the ground camber angle of the wheel and the friction circle reduction coefficient which is a coefficient for reducing and correcting the radius of the friction circle. This is a data map. When the ground camber angle is 0 degree (that is, when the tire is perpendicular to the road surface), the friction circle reduction coefficient becomes “1” which is the maximum, and the ground camber angle is further away from 0 degree (that is, The friction circle reduction coefficient is set to be smaller as the tire is inclined with respect to the road surface).
[0130]
Then, in subsequent S965, the ground camber angles (FR ground camber angle, FL ground camber angle, RR ground camber angle, RL ground camber angle) of each wheel 2FR, 2FL, 2RR, 2RL calculated by the ground camber angle calculation processing of FIG. Angle), and in subsequent S970, friction circle reduction coefficients (FR friction circle reduction coefficient, FL friction circle reduction coefficient, RR friction circle reduction coefficient) corresponding to the ground camber angles of the respective wheels 2FR, 2FL, 2RR, 2RL, (RL friction circle reduction coefficient) is calculated by interpolation or the like based on the “ground camber angle vs. friction circle reduction coefficient map” read in S960.
[0131]
Further, in the subsequent S975, an FR friction circle estimated value, which is an estimated value of the actual friction circle radius of each wheel 2FR, 2FL, 2RR, 2RL, and an FL friction circle estimate based on the following formulas 35 to 38: Value, RR friction circle estimated value, and RL friction circle estimated value are respectively calculated, and then the four-wheel friction circle estimation calculation process is terminated.
[0132]
[Expression 35]
FR friction circle estimated value = FR friction circle μ correction value × FR friction circle reduction coefficient Equation 35
[0133]
[Expression 36]
FL friction circle estimated value = FL friction circle μ correction value × FL friction circle reduction coefficient Equation 36
[0134]
[Expression 37]
RR friction circle estimated value = RR friction circle μ correction value × RR friction circle reduction coefficient Equation 37
[0135]
[Formula 38]
RL friction circle estimated value = RL friction circle μ correction value × RL friction circle reduction coefficient Equation 38
In other words, in this four-wheel friction circle estimation calculation processing, for each wheel 2FR, 2FL, 2RR, 2RL, an estimated μ that is an estimated value of the road surface friction coefficient is added to a friction circle basic value that is a basic friction circle radius that can be considered from a load. And the friction circle reduction coefficient, which is a correction coefficient corresponding to the ground camber angle, to calculate a friction circle estimated value (FR to RL friction circle estimated value) that is a final estimated value of the friction circle radius. Yes. The estimated friction circle values of the wheels 2FR, 2FL, 2RR, and 2RL indicate that the higher the wheel load, the closer the camber angle to the wheel is to 0 degrees, and the larger the estimated μ, the higher the grip performance level of the tire. The larger the value is set.
[0136]
Next, when the four-wheel friction circle estimation calculation process is completed, the ECU 20 proceeds to S50 of FIG. 2, and executes the target traveling state setting process shown in FIG.
The target travel state setting process calculates a target yaw rate, a target lateral G, and a target longitudinal G that are target physical physical quantities to be generated in the vehicle body in accordance with a driver's operation, and a target travel state obtained by them. The target body lateral force that is the target value of the vehicle body lateral force, the front target lateral force that is the target value of the front lateral force, the rear target lateral force that is the target value of the rear lateral force, and This is a process for calculating a target vehicle longitudinal force that is a target value of the vehicle longitudinal force.
[0137]
As shown in FIG. 16, when the ECU 20 starts executing the target travel state setting process, first, in S1000, the target lateral force calculation process of FIG. 17 is executed.
That is, in the target lateral force calculation process, as shown in FIG. 17, first, in S1005, the steering angle detected based on the signal from the steering angle sensor 12 is input, and in S1010, the wheel speed sensors 4FR, 4FL are input. , 4RR, 4RL, the detected vehicle speed is input. In subsequent S1015, an initial value of “0” is set to the F toe angle correction amount that is a variable indicating the virtual toe angle correction amount for the front wheels 2FR and 2FL.
[0138]
Next, in S1020, a steering angle correction amount is calculated based on the following Expression 39. Note that the term “−F toe angle correction amount” in Equation 39 is a direction in which the toe angles of the front wheels 2FR and 2FL are returned to the center position by the F toe angle correction amount (hereinafter, this direction is referred to as a switch back direction. In addition, it is shown that the opposite direction is referred to as a direction of increase. In other words, the steering angle correction amount is a value obtained by correcting the actual toe angles (= steering angle / gear ratio) of the front wheels 2FR and 2FL generated by the steering operation in the switchback direction by the F toe angle correction amount.
[0139]
[39]
Steering angle correction amount = steering angle / gear ratio−F toe angle correction amount Equation 39
In subsequent S1025, based on the following equation 40, the target yaw rate is calculated using the calculated steering angle correction amount, and in subsequent S1030, the target yaw rate calculated in S1025 is multiplied by the vehicle speed. A target lateral G (= target yaw rate × vehicle speed) is calculated.
[0140]
[Formula 40]
Target yaw rate = (steering angle correction amount × vehicle speed / wheel base) / (1 + target stability factor × vehicle speed × vehicle speed)
After calculating the target yaw rate and the target lateral G in this way, in step S1035, the target yaw rate acceleration of the vehicle body is calculated by differentiating the target yaw rate calculated in step S1025. In step S1040, the target yaw angular acceleration is calculated. The target yaw moment (= target yaw angular acceleration × moment constant) of the vehicle body is calculated by multiplying the calculated target yaw angular acceleration by the moment constant. In subsequent S1045, a target vehicle lateral force (= target lateral G × vehicle weight) is calculated by multiplying the target lateral G calculated in S1030 by the vehicle weight.
[0141]
In the subsequent S1050, the front target lateral force and the rear target lateral force necessary for realizing the target yaw rate and the target lateral G calculated in S1025 and S1030 are calculated based on the following formulas 41 and 42.
[0142]
[Expression 41]
Front target lateral force = (target vehicle lateral force x center of gravity rear tire distance + target yaw moment) / wheel base ... Formula 41
[0143]
[Expression 42]
Rear target lateral force = (target vehicle lateral force x center of gravity front tire distance-target yaw moment) / wheel base ... Formula 42
When the front target lateral force and the rear target lateral force are calculated in this way, the process proceeds to S1055, and the estimated friction circle values of the respective wheels 2FR, 2FL, 2RR, 2RL calculated in the four-wheel friction circle estimation calculation processing of FIG. (FR to RL friction circle estimated value) is read out. Based on the following formulas 43 and 44, the front friction circle limit value indicating the total maximum grip force that can be generated by both front wheels 2FR and 2FL, and the total maximum grip force that can be generated by both rear wheels 2RR and 2RL. The rear friction circle limit value representing
[0144]
[Expression 43]
Front friction circle limit value = FR friction circle estimation value + FL friction circle estimation value Equation 43
[0145]
(44)
Rear friction circle limit value = RR friction circle estimated value + RL friction circle estimated value Equation 44
In subsequent S1060, it is determined whether or not the calculated front friction circle limit value is larger than the front target lateral force calculated in S1050. If the front friction circle limit value is larger, both front wheels 2FR and 2FL are determined. Determines that the front target lateral force can be generated, and proceeds to the next S1065. In S1065, it is determined whether or not the rear friction circle limit value calculated in S1055 is larger than the rear target lateral force calculated in S1050. If the rear friction circle limit value is larger, both rear wheels 2RR are determined. , 2RL can determine that the rear target lateral force can be generated, and the target lateral force calculation process is terminated.
[0146]
On the other hand, when it is determined in S1060 that the front friction circle limit value is not larger than the front target lateral force, or in S1065, it is determined that the rear friction circle limit value is not larger than the rear target lateral force. In this case, it is impossible to generate the front target lateral force or the rear target lateral force, and it is determined that the target yaw rate and the target lateral G calculated in S1025 and S1030 are too large, and the process proceeds to S1070. In S1070, a value obtained by adding the predetermined value K8 to the current F toe angle correction amount is set as a new F toe angle correction amount, and thereafter, the processes in and after S1020 are repeated.
[0147]
For this reason, in the target lateral force calculation process, every time a negative determination is made in S1060 or S1065, the steering angle correction amount is corrected in the return direction, and the target yaw rate and the target lateral G are corrected to values having small absolute values. The Then, the front target lateral force and the rear target lateral force that can be achieved by the front friction circle limit value and the rear friction circle limit value are set.
[0148]
When the processing after S1020 is executed for the first time (that is, when the F toe angle correction amount is “0”), if an affirmative determination is made in S1060 and S1065, the target calculated in S1025 and S1030 The yaw rate and the target lateral G have the same values as the target yaw rate and the target lateral G calculated by the road surface μ estimation calculation process in FIG. 7, and the front lateral force and the rear lateral force necessary to realize the target yaw rate and the target lateral G are shown. The force is set as the front target lateral force and the rear target lateral force, respectively.
[0149]
When the target lateral force calculation process in FIG. 17 is completed in this way, as shown in FIG. 16, in the target travel state setting process, the process proceeds to S1100 and the target longitudinal force calculation process in FIG. 18 is executed.
That is, in the target longitudinal force calculation process, as shown in FIG. 18, first, in S1110, the accelerator opening detected based on the signal from the accelerator opening sensor 18 is input, and in the subsequent S1120, the input accelerator is input. By differentiating the opening, an accelerator speed, which is a change speed of the accelerator opening, is calculated.
[0150]
In subsequent S1130, the “accelerator state vs. target front / rear G map” is read from the ROM. The “accelerator state vs. target longitudinal G map” is a three-dimensional data map that stores the relationship between the accelerator opening, the accelerator speed, and the vehicle body target longitudinal G as shown in FIG. Further, in subsequent S1140, the target longitudinal G of the vehicle body corresponding to the actual accelerator opening input in S1110 and the accelerator speed calculated in S1120 is calculated based on the “accelerator state versus target longitudinal G map”. The calculated target front and rear G is stored as the first target front and rear G1.
[0151]
Next, in S1150, the brake pedal force detected based on the signal from the brake pedal force sensor 16 is input, and in S1160, the “brake pedal force versus target front-rear G map” is read from the ROM. This “brake pedal force vs. target longitudinal G map” is a data map storing the relationship between the brake pedal force and the target longitudinal G of the vehicle body, as shown in FIG. Further, in subsequent S1170, the target longitudinal G of the vehicle body corresponding to the actual brake pedal force input in S1150 is calculated based on the “brake pedal force vs. target longitudinal G map”, and the calculated target longitudinal G is 2 is stored as a target G2 before and after G2.
[0152]
In the subsequent S1180, the first target longitudinal G1 based on the accelerator opening and the accelerator speed and the second target longitudinal G2 based on the brake pedal force are added to obtain the final vehicle target longitudinal G (= target). (Front / rear G1 + target front / rear G2) is calculated, and in the next S1190, the final target front / rear G calculated in S1180 is multiplied by the vehicle weight to obtain the target vehicle front / rear force required to realize the target front / rear G. (= Target longitudinal G × vehicle weight) is calculated.
[0153]
After calculating the target vehicle longitudinal force in this way, the target longitudinal force calculation process is terminated, and the target traveling state setting process of FIG. 16 is also terminated.
When the ECU 20 finishes the target travel state setting process, the ECU 20 then proceeds to S55 in FIG. 2 and executes the additional force calculation process shown in FIG. 21 in S55.
[0154]
In this additional force calculation process, an additional amount of force that the wheel must generate to achieve the target yaw rate, the target lateral G, and the target longitudinal G calculated in the target travel state setting process of FIG. (Or negative addition).
As shown in FIG. 21, when the ECU 20 starts executing the additional force calculation process, first, in S1200, the front target calculated in the target travel state setting process of FIG. 16 (specifically, the target lateral force calculation process of FIG. 17). Lateral force is input, and in the subsequent S1210, the actual front lateral force calculated by the lateral force calculation processing of FIG. 4 is input.
[0155]
Next, in S1220, the rear target lateral force calculated in the target travel state setting process of FIG. 16 (specifically, the target lateral force calculation process of FIG. 17) is input, and in S1230, the lateral force calculation process of FIG. Enter the actual rear lateral force calculated in step.
In subsequent S1240, both front wheels 2FR and 2FL are added to realize the target yaw rate and the target lateral G by subtracting the actual front lateral force from the front target lateral force as shown in the following equation 45. The front additional lateral force, which is the total lateral force that must be generated, is calculated.
[0156]
Furthermore, both rear wheels 2RR and 2RL must be generated in order to realize the target yaw rate and the target lateral G by subtracting the actual rear lateral force from the rear target lateral force, as shown in Equation 46 below. Calculate the rear additional lateral force, which is the total lateral force that must be achieved.
[0157]
[Equation 45]
Front additional lateral force = Front target lateral force-Front lateral force ... Formula 45
[0158]
[Equation 46]
Rear additional lateral force = rear target lateral force-rear lateral force ... Formula 46
Next, in S1250, the target vehicle body longitudinal force calculated in the target travel state setting process of FIG. 16 (specifically, the target longitudinal force calculation process of FIG. 18) is input, and in subsequent S1260, the longitudinal force calculation process of FIG. Enter the actual vehicle longitudinal force calculated in step.
[0159]
Then, in S1270, four wheels 2FR, 2FL, 2RR, and 2RL are added to realize the target longitudinal G by subtracting the actual vehicle longitudinal force from the target vehicle longitudinal force as shown in Equation 47 below. The additional vehicle longitudinal force, which is the total longitudinal force that must be generated in this manner, is calculated, and then the additional force calculation process is terminated.
[0160]
[Equation 47]
Additional vehicle longitudinal force = target vehicle longitudinal force-vehicle longitudinal force ... Formula 47
Then, after completing the additional force calculation process, the ECU 20 proceeds to S60 of FIG. 2, and executes the frictional circle margin calculation process shown in FIGS. 22 and 23 at S60. FIG. 22 shows the first half of the friction circle margin calculation process, and FIG. 23 shows the second half thereof.
[0161]
This friction circle margin calculation process is based on the FR to RL friction circle estimation values calculated in the four-wheel friction circle estimation calculation process of FIG. 13, and the lateral force that can be generated by the addition of each wheel 2FR, 2FL, 2RR, 2RL. This is a process for calculating the margin (power for margin).
As shown in FIG. 22, when the ECU 20 starts executing the friction circle margin calculation process, first, in S1300, the FR friction circle estimated value calculated by the four-wheel friction circle estimation calculation process of FIG. 13 and the longitudinal force of FIG. The actual front longitudinal force calculated by the calculation process and the actual front lateral force calculated by the lateral force calculation process of FIG. 4 are read.
[0162]
Then, based on the following equation 48, an FR lateral force positive additional limit value 1 that is a margin of lateral force of the right front wheel 2FR that can be generated by adding the right front wheel 2FR in the same direction as the lateral force that is currently generated is Based on the following formula 49, the FR side force negative additional limit that is the margin of the lateral force of the right front wheel 2FR that can be generated by adding the right front wheel 2FR in the opposite direction to the lateral force that is currently generated Calculate the value.
[0163]
[Formula 48]

[0164]
[Equation 49]

[0165]
That is, in S1300, the values obtained by dividing the actual front longitudinal force and the front lateral force by 2, respectively, are the actual front / rear force (= front longitudinal force / 2) and the actual lateral force (= front lateral force / 2) and the actual lateral force is calculated from the lateral force value (= previous terms of Equation 48 and Equation 49) in which the resultant force with the actual longitudinal force is equal to the FR friction circle estimated value that is the friction circle radius of the right front wheel 2FR. To obtain the FR lateral force positive additional limit value 1, which is the margin of lateral force that can be generated in the same direction as the actual lateral force, and the resultant force with the actual longitudinal force is the FR friction circle. By adding the actual lateral force to the lateral force value equal to the estimated value, the FR lateral force negative additional limit value, which is a margin of lateral force that can be generated by adding in the opposite direction to the actual lateral force, is obtained. ing.
[0166]
Next, in subsequent S1305, the estimated FL friction circle value calculated in the four-wheel friction circle estimation calculation process in FIG. 13, the actual front longitudinal force calculated in the longitudinal force calculation process in FIG. 5, and the lateral force in FIG. Reads the actual front lateral force calculated by the calculation process.
Just as in the case of S1300, based on the following equation 50, the margin of the lateral force of the left front wheel 2FL that can be generated in the same direction as the lateral force generated by the left front wheel 2FL is added. FL lateral force positive additional limit value 1 is calculated, and based on the following equation 51, the margin of lateral force of the left front wheel 2FL that can be generated by adding the left front wheel 2FL in the opposite direction to the lateral force currently generated The FL lateral force negative additional limit value, which is the degree, is calculated.
[0167]
[Equation 50]

[0168]
[Equation 51]

[0169]
Then, in subsequent S1310, it is determined whether or not the FL lateral force positive additional limit value 1 calculated in S1305 is smaller than “0”. If not smaller than “0”, the process proceeds to S1315. FR which is the true margin of lateral force of the right front wheel 2FR that can be generated by adding the FR lateral force positive additional limit value 1 calculated in S1300 in the same direction as the lateral force currently generated by the right front wheel 2FR. It is memorized as a lateral force positive additional limit value.
[0170]
On the other hand, if it is determined in S1310 that the FL lateral force positive additional limit value 1 is smaller than “0” (that is, the FL lateral force positive additional limit value 1 is negative), the process proceeds to S1320. Then, the value obtained by adding the FL lateral force positive additional limit value 1 which is a negative value to the FR lateral force positive additional limit value 1 calculated in S1300 is stored as the FR lateral force positive additional limit value.
[0171]
That is, the fact that the FL lateral force positive additional limit value 1 is negative means that the actual longitudinal force (= front longitudinal force / 2) and lateral force (= front lateral force / 2) in the calculation of the left front wheel 2FL. This shows that the resultant force exceeds the estimated FL friction circle by the absolute value of the FL lateral force positive additional limit value 1, but in reality, both front wheels 2FR and 2FL have the same amount of lateral force. The right front wheel 2FR is considered to generate more lateral force by the absolute value of the FL lateral force positive additional limit value 1 than the left front wheel 2FL. Therefore, in S1320, the margin of lateral force of the right front wheel 2FR is reduced by the absolute value of the FL lateral force positive additional limit value 1.
[0172]
Then, after the FR lateral force positive additional limit value is stored in S1315 or S1320, the process proceeds to S1325 to determine whether or not the stored FR lateral force positive additional limit value is smaller than “0”. If the FR lateral force positive additional limit value is not smaller than “0”, the process proceeds to S1335. If the FR lateral force positive additional limit value is smaller than “0”, the lateral force is no longer applied to the right front wheel 2FR. In step S1330, the FR lateral force positive additional limit value is set to “0”, and the process proceeds to step S1335.
[0173]
Then, in S1335-S1355, the same processing as S1310-S1330 described above is performed for the left front wheel 2FL.
That is, first in S1335, it is determined whether or not the FR lateral force positive additional limit value 1 calculated in S1300 is smaller than “0”. If it is not smaller than “0”, the process proceeds to S1340. FL, which is the true margin of lateral force of the left front wheel 2FL that can be generated by adding the FL lateral force positive additional limit value 1 calculated in S1305 in the same direction as the lateral force currently generated by the left front wheel 2FL. It is memorized as a lateral force positive additional limit value.
[0174]
On the other hand, when it is determined in S1335 that the FR lateral force positive additional limit value 1 is smaller than “0”, the process proceeds to S1345 and the FL lateral force positive additional limit value 1 calculated in S1305 is obtained. The value obtained by adding the FR lateral force positive additional limit value 1 which is a negative value is stored as the FL lateral force positive additional limit value. That is, in this case, contrary to the case of S1320 described above, the left front wheel 2FL generates more lateral force by the absolute value of the FR lateral force positive additional limit value 1 than the right front wheel 2FR. The margin of the lateral force of the left front wheel 2FL is reduced by the absolute value of the FR lateral force positive additional limit value 1.
[0175]
Then, after storing the FL lateral force positive additional limit value in S1340 or S1345, the process proceeds to S1350, and it is determined whether or not the stored FL lateral force positive additional limit value is smaller than “0”. If the FL lateral force positive additional limit value is not smaller than “0”, the process proceeds to S1360 in FIG. 23, but if the FL lateral force positive additional limit value is smaller than “0”, the left front wheel 2FL is no longer present. It is determined that a lateral force cannot be generated and the FL lateral force positive additional limit value is set to “0” in S1355, and then the process proceeds to S1360 in FIG.
[0176]
Next, in the processing of S1360 to S1415 shown in FIG. 23, the same processing as S1300 to S1355 of FIG. 22 described above is performed for each of the right rear wheel 2RR and the left rear wheel 2RL.
That is, first in S1360, the estimated RR friction circle calculated in the four-wheel friction circle estimation calculation process in FIG. 13, the actual rear longitudinal force calculated in the longitudinal force calculation process in FIG. 5, and the lateral force calculation in FIG. Read the actual rear lateral force calculated in the process. Then, based on the following equation 52, the RR lateral force positive additional limit value that is a margin of lateral force of the right rear wheel 2RR that can be generated by adding the right rear wheel 2RR in the same direction as the lateral force currently generated. 1 and further, based on the following equation 53, the RR lateral which is the margin of the lateral force of the right rear wheel 2RR that can be generated by adding the right rear wheel 2RR in the opposite direction to the lateral force currently generated Calculate the force negative additional limit value.
[0177]
[Formula 52]

[0178]
[Equation 53]

[0179]
Next, in subsequent S1365, the estimated RL friction circle calculated in the four-wheel friction circle estimation calculation process of FIG. 13, the actual rear longitudinal force calculated in the longitudinal force calculation process of FIG. 5, and the lateral force of FIG. Reads the actual rear lateral force calculated by the calculation process. Then, based on the following formula 54, the RL lateral force positive additional limit value which is a margin of the lateral force of the left rear wheel 2RL that can be generated in the same direction as the lateral force generated by the left rear wheel 2RL. 1 and further, based on the following formula 55, the RL lateral which is the margin of lateral force of the left rear wheel 2RL that can be generated by adding in the opposite direction to the lateral force currently generated by the left rear wheel 2RL. Calculate the force negative additional limit value.
[0180]
[Formula 54]

[0181]
[Expression 55]

[0182]
That is, in S1360 and S1365, the values obtained by dividing the actual rear longitudinal force and the rear lateral force by 2, respectively, are the longitudinal forces actually generated by the rear wheels 2RR and 2RL (= rear longitudinal force / 2) and RR lateral force positive additional limit value 1, RR lateral force negative additional limit value, RL lateral force positive additional limit value in the same manner as S1300 and S1305 in FIG. 22 assuming that the lateral force (= rear lateral force / 2). 1, and RL lateral force negative additional limit value is obtained.
[0183]
Subsequently, in S1370, it is determined whether or not the RL lateral force positive additional limit value 1 calculated in S1365 is smaller than “0”. If not smaller than “0”, the process proceeds to S1375. RR lateral force positive additional limit value 1 calculated in S1360 above is the true margin of lateral force of the right rear wheel 2RR that can be generated by adding the right lateral wheel 2RR in the same direction as the lateral force currently generated by the right rear wheel 2RR. Store as a certain RR lateral force positive additional limit value.
[0184]
On the other hand, when it is determined in S1370 that the RL lateral force positive additional limit value 1 is smaller than “0”, the process proceeds to S1380 and the RR lateral force positive additional limit value 1 calculated in S1360 is obtained. The value obtained by adding the negative RL lateral force positive additional limit value 1 to the RR lateral force positive additional limit value is stored.
[0185]
Then, after storing the RR lateral force positive additional limit value in S1375 or S1380, the process proceeds to S1385, and it is determined whether or not the stored RR lateral force positive additional limit value is smaller than “0”. If the RR lateral force positive additional limit value is not smaller than “0”, the process proceeds to S1395, but if the RR lateral force positive additional limit value is smaller than “0”, the lateral force is no longer applied to the right rear wheel 2RR. In step S1390, the RR lateral force positive additional limit value is set to “0”, and the process advances to step S1395.
[0186]
Next, in S1395, it is determined whether or not the RR lateral force positive additional limit value 1 calculated in S1360 is smaller than “0”. If it is not smaller than “0”, the process proceeds to S1400, and S1365 is performed. RL is the true margin of lateral force of the left rear wheel 2RL that can be generated by adding the RL lateral force positive additional limit value 1 calculated in step 1 in the same direction as the lateral force currently generated by the left rear wheel 2RL. It is memorized as a lateral force positive additional limit value.
[0187]
On the other hand, if it is determined in S1395 that the RR lateral force positive additional limit value 1 is smaller than “0”, the process proceeds to S1405 and the RL lateral force positive additional limit value 1 calculated in S1365 is obtained. A value obtained by adding RR lateral force positive additional limit value 1 which is a negative value is stored as an RL lateral force positive additional limit value.
[0188]
Then, after storing the RL lateral force positive additional limit value in S1400 or S1405, the process proceeds to S1410 to determine whether or not the stored RL lateral force positive additional limit value is smaller than “0”. If the RL lateral force positive additional limit value is not smaller than “0”, the frictional circle margin calculation process is terminated as it is. If the RL lateral force positive additional limit value is smaller than “0”, the left rear wheel It is determined that a lateral force can no longer be added to 2RL, and after the RL lateral force positive additional limit value is set to “0” in S1415, the frictional circle margin calculating process is terminated.
[0189]
When the execution of the frictional circle margin calculation process is thus completed, the process proceeds to S65 in FIG. 2, and the additional force distribution process shown in FIG. 24 is executed in S65.
In this additional force distribution processing, the front additional lateral force, rear additional lateral force, and additional vehicle longitudinal force calculated in the additional force calculation processing of FIG. 21 are used for each wheel so that the grip force of the four tires does not exceed the limit. This is a process for allocating to 2FR, 2FL, 2RR, 2RL.
[0190]
Then, as shown in FIG. 24, when the ECU 20 starts executing the additional force distribution process, first, in S1500, the additional lateral force distribution calculation process of FIG. 25 is executed.
That is, in the additional lateral force distribution calculation process, as shown in FIG. 25, first, in S1505, it is determined whether or not the front additional lateral force calculated in the additional force calculation process of FIG. 21 is greater than “0”. If the front additional lateral force is greater than “0”, the toe angle of the front wheels 2FR and 2FL is corrected to the increased direction, and the lateral force of the front wheels 2FR and 2FL is added in the same direction as the current generation direction. In the subsequent S1510, the margin of lateral force that can be generated by the right front wheel 2FR being added to the FR lateral force positive additional limit value calculated by the friction circle margin calculation processing of FIGS. 22 and 23. The FL lateral force is the margin of the lateral force that can be generated by the left front wheel 2FL being added to the FL lateral force positive additional limit value calculated by the friction circle margin calculation process. Set as a limit value.
[0191]
Conversely, if it is determined in S1505 that the front additional lateral force is not greater than “0”, the lateral force of the front wheels 2FR and 2FL is corrected by correcting the toe angle of the front wheels 2FR and 2FL in the reverse direction. Is added in the direction opposite to the current generation direction, the process proceeds to S1515, and the FR lateral force negative additional limit value calculated by the friction circle margin calculation process is set as the FR lateral force limit value. Similarly, the FL lateral force negative additional limit value calculated by the friction circle margin calculation process is set as the FL lateral force limit value.
[0192]
Then, after performing the process of S1510 or S1515, the process proceeds to S1520, where it is determined whether or not the rear additional lateral force calculated by the additional force calculation process of FIG. 21 is greater than “0”. If the rear additional lateral force is greater than “0”, the toe angles of the rear wheels 2RR and 2RL are corrected to increase and the lateral forces of the rear wheels 2RR and 2RL are made the same direction as the current generation direction. RR which is the margin of lateral force that can be generated by adding the right rear wheel 2RR to the RR lateral force positive additional limit value calculated in the friction circle margin calculation processing in step S1525. The RL lateral force limit value, which is the margin of lateral force that can be generated by the left rear wheel 2RL being added to the RL lateral force positive additional limit value calculated by the friction circle margin calculation process as well as the lateral force limit value. Set as.
[0193]
Conversely, if it is determined in S1520 that the rear additional lateral force is not greater than “0”, the toe angles of the rear wheels 2RR and 2RL are corrected in the return direction, and the rear wheels 2RR and 2RL It is determined that the lateral force should be added in the direction opposite to the current generation direction, the process proceeds to S1530, and the RR lateral force negative additional limit value calculated in the friction circle margin calculation process is set as the RR lateral force limit value. At the same time, the RL side force negative additional limit value calculated in the friction circle margin calculation process is set as the RL side force limit value.
[0194]
Then, after performing the processing of S1525 or S1530, the process proceeds to S1535, and the FR lateral force limit value ratio and the FL lateral force limit value ratio are calculated based on the following formulas 56 and 57.
[0195]
[Expression 56]
FR lateral force limit value ratio = FR lateral force limit value / (FR lateral force limit value + FL lateral force limit value) Equation 56
[0196]
[Equation 57]
FL lateral force limit value ratio = 1-FR lateral force limit value ratio Expression 57
In S1540, the RR lateral force limit value ratio and the RL lateral force limit value ratio are calculated based on the following formulas 58 and 59.
[0197]
[Formula 58]
RR lateral force limit value ratio = RR lateral force limit value / (RR lateral force limit value + RL lateral force limit value) ... Formula 58
[0198]
[Formula 59]
RL lateral force limit value ratio = 1-RR lateral force limit value ratio (Formula 59)
Next, in S1545, based on the following formulas 60 and 61, the front lateral force addition possible ratio indicating what percentage of the front additional lateral force can actually be added and the rear additional lateral force percentage actually The rear lateral force addition ratio indicating whether it can be added is calculated.
[0199]
[Expression 60]
Front lateral force additional possible ratio = (FR lateral force limit value + FL lateral force limit value) / Front additional lateral force ... Formula 60
[0200]
[Equation 61]
Rear lateral force addition possible ratio = (RR lateral force limit value + RL lateral force limit value) / rear additional lateral force ... Formula 61
In subsequent S1550, it is determined whether or not the calculated front lateral force addition possibility ratio is greater than the rear lateral force addition possibility ratio. If the front lateral force addition possibility ratio is greater than the rear lateral force addition possibility ratio. , The process proceeds to S1555, and the smaller rear lateral force addition possibility ratio is set as the lateral force addition possibility ratio. Conversely, if it is determined in S1550 that the front lateral force addition possibility ratio is not larger than the rear lateral force addition possibility ratio, the process proceeds to S1560, and the smaller front lateral force addition possibility ratio is determined. Set as the ratio of possible lateral force addition.
[0201]
After performing the processing of S1555 or S1560 in this way, the process proceeds to S1565, where it is determined whether or not the set lateral force addition possible ratio is larger than “1”. In step S1570, the lateral force addition possibility ratio is set to “1”, and then the process proceeds to step S1575. If it is determined in S1565 that the lateral force addition possibility ratio is not greater than “1”, the process proceeds to S1575 as it is.
[0202]
In S1575, based on the following formulas 62 to 65, the FR lateral force addition amount that is the lateral force to be added to the right front wheel 2FR and the FL lateral force addition amount that is the lateral force to be added to the left front wheel 2FL And an RR lateral force addition amount that is a lateral force to be added to the right rear wheel 2RR and an RL lateral force addition amount that is a lateral force to be added to the left rear wheel 2RL, respectively, and then the additional lateral force The distribution calculation process ends.
[0203]
[62]
FR lateral force addition amount = Front additional lateral force x Lateral force addition ratio x FR lateral force limit value ratio ... Formula 62
[0204]
[Equation 63]
FL lateral force addition amount = Front additional lateral force x Lateral force addition ratio x FL lateral force limit value ratio ... Formula 63
[0205]
[Expression 64]
RR lateral force additional amount = rear additional lateral force x side force additional possible ratio x RR lateral force limit value ratio ... Formula 64
[0206]
[Equation 65]
RL side force additional amount = rear additional side force x side force additional possible ratio x RL side force limit value ratio ... Formula 65
In other words, in this additional lateral force distribution calculation process, the front additional lateral force and the rear additional lateral force calculated in the additional force calculation process of FIG. 21 are used for each wheel 2FR so that the grip force of the four tires does not exceed the limit. The lateral force addition amount (FR to RL lateral force addition amount) that can be distributed to 2FL, 2RR, and 2RL is calculated.
[0207]
Then, when this additional lateral force distribution calculation process is completed, as shown in FIG. 24, in the additional force distribution process, the process proceeds to S1600, and the longitudinal force margin calculation process of FIG. 26 is executed.
That is, in the longitudinal force margin calculation process, as shown in FIG. 26, first, in S1610, the FR friction circle estimated value calculated in the four-wheel friction circle estimation calculation process in FIG. 13 and the lateral force calculation process in FIG. The actual front lateral force, the actual front longitudinal force calculated by the longitudinal force calculation process of FIG. 5, and the FR lateral force addition amount calculated by the additional lateral force distribution calculation process of FIG. 25 are read.
[0208]
Based on the following formula 66, the FR front / rear force positive additional limit value, which is a margin of the front / rear force of the right front wheel 2FR that can be generated in the same direction as the front / rear force generated by the right front wheel 2FR, is calculated. Furthermore, based on the following formula 67, the FR front / rear force negative additional limit value that is the margin of the front / rear force of the right front wheel 2FR that can be generated in the opposite direction to the front / rear force generated by the right front wheel 2FR. Is calculated.
[0209]
[Equation 66]

[0210]
[Expression 67]

[0211]
That is, in S1610, the values obtained by dividing the actual front longitudinal force and the front lateral force by 2, respectively, are the actual longitudinal force (= front longitudinal force / 2) of the right front wheel 2FR and the actual lateral force (= front lateral force / 2), the longitudinal force value at which the resultant force with the lateral force in addition to the actual lateral force in addition to the actual lateral force is equal to the estimated FR friction circle value (= previous terms of Equations 66 and 67) ), The FR front / rear force positive additional limit value, which is a margin of the front / rear force that can be generated in the same direction as the actual front / rear force, is obtained by subtracting the actual front / rear force. Also, by adding the actual longitudinal force to the longitudinal force value at which the resultant force with the lateral force in addition to the actual lateral force is equal to the estimated FR friction circle, The front / rear force negative additional limit value, which is a margin of the front / rear force that can be generated in the direction opposite to the front / rear force, is obtained.
[0212]
Then, in subsequent S1620, it is determined whether or not the additional vehicle longitudinal force calculated by the additional force calculation process of FIG. 21 is greater than “0”. If the additional vehicle longitudinal force is greater than “0”, it is determined that the longitudinal force of the right front wheel 2FR must be added in the same direction as the current generation direction, and in S1630, the calculation is performed in S1610. The added FR front / rear force positive limit value is set as the FR front / rear force limit value, which is a margin of the front / rear force that can be generated by the addition of the right front wheel 2FR.
[0213]
Conversely, if it is determined in S1620 that the additional vehicle longitudinal force is not greater than “0”, it is determined that the longitudinal force of the right front wheel 2FR must be added in the direction opposite to the current generation direction. Then, the process proceeds to S1640, and the FR longitudinal force negative addition limit value calculated in S1610 is set as the FR longitudinal force limit value.
[0214]
Then, after performing the processing of S1630 or S1640, in each of the next S1650 to S1670, the front and rear force margins that can be generated by adding the left front wheel 2FL by the same procedure as S1610 to S1640 described above. A certain FL longitudinal force limit value, an RR longitudinal force limit value that can be generated by adding the right rear wheel 2RR, and a margin of longitudinal force that can be generated by adding the left rear wheel 2RL A certain RL longitudinal force limit value is set.
[0215]
When setting the FL longitudinal force limit value in S1650, instead of the FR friction circle estimated value and the FR lateral force additional amount for each of the above formulas 66 and 67, the FL friction circle estimated value and By using the FL lateral force addition amount, the FL longitudinal force positive additional limit value and the FL longitudinal force negative additional limit value are calculated. When the additional vehicle longitudinal force is greater than “0”, the FL longitudinal force positive additional limit value is set as the FL longitudinal force limit value. Conversely, when the additional vehicle longitudinal force is not greater than “0”. Is set as the FL longitudinal force limit value.
[0216]
When setting the RR longitudinal force limit value in S1660, instead of the FR friction circle estimated value and the FR lateral force additional amount for each of the above formulas 66 and 67, respectively, By using the RR lateral force addition amount and using the actual rear lateral force and rear longitudinal force instead of the front lateral force and front longitudinal force, respectively, the RR longitudinal force positive additional limit value and the RR longitudinal force negative additional limit are used. Value. When the additional vehicle longitudinal force is greater than “0”, the RR longitudinal force positive additional limit value is set as the RR longitudinal force limit value. Conversely, when the additional vehicle longitudinal force is not greater than “0”. The RR longitudinal force negative additional limit value is set as the RR longitudinal force limit value.
[0217]
Furthermore, when the RL longitudinal force limit value is set in S1670, instead of the FR friction circle estimated value and the FR lateral force additional amount for each of the above formulas 66 and 67, the RL friction circle estimated value, respectively. And the RL lateral force addition amount, and instead of the front lateral force and the front longitudinal force, the actual rear lateral force and the rear longitudinal force are used, respectively. The limit value is calculated. When the additional vehicle longitudinal force is greater than “0”, the RL longitudinal force positive additional limit value is set as the RL longitudinal force limit value. Conversely, when the additional vehicle longitudinal force is not greater than “0”. The RL longitudinal force negative additional limit value is set as the RL longitudinal force limit value.
[0218]
Thus, in the longitudinal force margin calculation process, when each wheel 2FR, 2FL, 2RR, 2RL generates an additional amount of FR to RL lateral force in addition to the current lateral force, each wheel 2FR, 2FL, 2RR, 2RL is The FR to RL longitudinal force limit value, which is a margin of the longitudinal force that can be additionally generated, is obtained based on the estimated FR to RL friction circle.
[0219]
When the longitudinal force margin calculation process of FIG. 26 is completed in this way, as shown in FIG. 24, in the additional force distribution process, the process proceeds to S1700, and the additional longitudinal force distribution calculation process of FIG. 27 is executed.
That is, in the additional longitudinal force distribution calculation process, as shown in FIG. 27, first, in S1705, whether or not the FR longitudinal force limit value calculated by the longitudinal force margin calculation process of FIG. 26 is larger than the FL longitudinal force limit value. Determine. If the FR longitudinal force limit value is larger than the FL longitudinal force limit value, the process proceeds to S1710, and the value obtained by doubling the smaller FL longitudinal force limit value (= FL longitudinal force limit value × 2) is set to both front wheels. It is set as the front longitudinal force limit value which is the total value of the margin of longitudinal force that can be generated by adding 2FR and 2FL.
[0220]
Conversely, if it is determined in S1705 that the FR longitudinal force limit value is not greater than the FL longitudinal force limit value, the process proceeds to S1715, in which the smaller FR longitudinal force limit value is doubled. (= FR longitudinal force limit value × 2) is set as the front longitudinal force limit value.
[0221]
After performing the processing of S1710 or S1715 in this way, the process proceeds to S1720, and is the RR longitudinal force limit value calculated in the longitudinal force margin calculation process of FIG. 26 now larger than the RL longitudinal force limit value? Determine whether or not. If the RR longitudinal force limit value is larger than the RL longitudinal force limit value, the process proceeds to S1725, and a value obtained by doubling the smaller RL longitudinal force limit value (= RL longitudinal force limit value × 2) is The rear longitudinal force limit value, which is the total value of the margins of longitudinal force that can be generated by the addition of the wheels 2RR and 2RL, is set.
[0222]
Conversely, if it is determined in S1720 that the RR longitudinal force limit value is not larger than the RL longitudinal force limit value, the process proceeds to S1730, and the smaller RR longitudinal force limit value is doubled. (= RR longitudinal force limit value × 2) is set as the rear longitudinal force limit value.
[0223]
Then, after performing the processing of S1725 or S1730, the process proceeds to S1735, and the front limit value ratio and the rear limit value ratio are calculated based on the following formulas 68 and 69.
[0224]
[Equation 68]
Front limit value ratio = front longitudinal force limit value / (front longitudinal force limit value + rear longitudinal force limit value)
[0225]
[Equation 69]
Rear limit value ratio = 1-front limit value ratio (Formula 69)
Further, in subsequent S1740, based on the following equation 70, a longitudinal force addition possible ratio indicating how much of the additional vehicle body longitudinal force can be actually added is calculated.
[0226]
[Equation 70]
Ratio of possible addition of longitudinal force = (front longitudinal force limit value + rear longitudinal force limit value) / additional vehicle longitudinal force ... Formula 70
Next, in S1745, it is determined whether or not the calculated longitudinal force addition possibility ratio is greater than “1”. If it is greater than “1”, the longitudinal force addition possibility ratio is set to “1” in the next S1750. After setting, the process proceeds to S1755. On the other hand, if it is determined in S1745 that the ratio of possible longitudinal force addition is not greater than “1”, the process proceeds to S1755 as it is.
[0227]
Then, in S1755, based on the following formulas 71 to 74, the FR longitudinal force additional amount that is the longitudinal force to be added to the right front wheel 2FR and the FL longitudinal force additional amount that is the longitudinal force to be added to the left front wheel 2FL RR longitudinal force addition amount, which is the longitudinal force to be added to the right rear wheel 2RR, and RL longitudinal force addition amount, which is the longitudinal force to be added to the left rear wheel 2RL, respectively, and then the additional longitudinal force The distribution calculation process ends.
[0228]
[Equation 71]
FR front / rear force addition amount = additional vehicle front / rear force × ratio for adding front / rear force × front limit value ratio / 2
[0229]
[Equation 72]
FL front / rear force addition amount = additional vehicle longitudinal force x longitudinal force addition ratio x front limit value ratio / 2 ... Formula 72
[0230]
[Equation 73]
RR longitudinal force additional amount = additional vehicle longitudinal force × ratio for adding longitudinal force × rear limit value ratio / 2 (Formula 73)
[0231]
[Equation 74]
RL longitudinal force addition amount = additional vehicle longitudinal force × ratio of adding longitudinal force × rear limit value ratio / 2 Equation 74
That is, in this additional longitudinal force distribution calculation process, the additional vehicle longitudinal force calculated in the additional force calculation process of FIG. 21 is applied to each wheel 2FR, 2FL, 2RR, 2RL so that the grip force of the four-wheel tire does not exceed the limit. The amount of front / rear force addition (FR to RL front / rear force addition) of each wheel that can be distributed is calculated.
[0232]
Then, when the execution of this additional longitudinal force distribution calculation process is completed, the additional force distribution process of FIG. 24 is also terminated. Further, after completing the additional force distribution process, the ECU 20 proceeds to S70 of FIG. 2, and executes the variable amount calculation process of FIG. 28 in S70.
[0233]
This variable amount calculation processing is performed by the additional force distribution processing shown in FIG. 24 (specifically, the additional lateral force distribution calculation processing shown in FIG. 25 and the additional longitudinal force distribution calculation processing shown in FIG. 27). This is a process for calculating the control amount of the actuator for causing the wheels 2FR, 2FL, 2RR, 2RL to actually generate the RL longitudinal force addition amount.
[0234]
In FIG. 28, “**” alternatively represents each of “FR”, “FL”, “RR”, and “RL”. The process marked with “**” is performed for each of the wheels 2FR, 2FL, 2RR, 2RL. Here, when “**” is “FR” (that is, for the right front wheel 2FR). Case).
[0235]
As shown in FIG. 28, when the ECU 20 starts executing the variable amount calculation process, first, in step S1800, the FR lateral force addition amount calculated in the additional lateral force distribution calculation process of FIG. 25 is read.
In step S1805, the “lateral force additional amount versus additional toe variable angle map” is read from the ROM. As shown in FIG. 29, this “additional lateral force amount vs. additional toe variable angle map” is an additional toe that is the change amount of the lateral force addition amount and the toe angle of the wheel necessary to obtain the lateral force addition amount. This is a data map that stores variable angles in association with each other, and is prepared for each wheel 2FR, 2FL, 2RR, 2RL. The additional toe variable angle is set to increase in the direction to increase as the lateral force addition amount increases positively. Conversely, the additional toe variable angle increases in the return direction as the lateral force addition amount increases in negative direction. ing.
[0236]
In the subsequent S1810, the additional toe variable angle (FR additional toe variable angle) of the right front wheel 2FR corresponding to the FR lateral force additional amount read in S1800 is read in “Side force additional amount vs. additional toe” read in S1805. It is calculated based on the “variable angle map”.
Next, in S1815, the FR skid angle calculated in the four-wheel skid angle calculation process of FIG. 9 is input, and in subsequent S1820, the sum of the FR skid angle and the FR additional toe variable angle calculated in S1810 (= FR It is determined whether or not (side slip angle + FR additional toe variable angle) is larger than a predetermined value K9. If the sum is not larger than the predetermined value K9, the process proceeds to S1830 and the subsequent steps. If it is larger than the predetermined value K9, the value obtained by subtracting the FR skid angle from the predetermined value K9 in S1825. After resetting (= K9-FR skid angle) as the FR additional toe variable angle, the process proceeds to S1830 and subsequent steps.
[0237]
The predetermined value K9 is set to the value of the side slip angle at which the tire is considered to reach the limit. In the processing of S1820 and S1825, the current FR side slip angle and the FR additional toe variable angle to be controlled from now on. Is guarded so as not to exceed the predetermined value K9. On the other hand, for S1800 to S1825, only the right front wheel 2FR has been described, but the other wheels 2FL, 2RR, and 2RL are also executed in exactly the same manner, and the toe required for obtaining the additional amount of FL to RL lateral force respectively. The FL additional toe variable angle, the RR additional toe variable angle, and the RL additional toe variable angle, which are the angle change angles, are respectively calculated.
[0238]
Then, when the FR to RL additional toe variable angle is calculated in this way, in S1830 to S1845, the toe angle of the right front wheel 2FR to be adjusted by the toe control actuator 22FR is calculated based on the following formulas 75 to 78. A certain FR toe variable angle, a FL toe variable angle that is a toe angle of the left front wheel 2FL to be adjusted by the toe control actuator 22FL, and an RR toe variable angle that is a toe angle of the right rear wheel 2RR to be adjusted by the toe control actuator 22RR And an RL toe variable angle that is a toe angle of the left rear wheel 2RL to be adjusted by the toe control actuator 22RL, respectively.
[0239]
[Expression 75]
FR toe variable angle = previous value of FR toe variable angle + FR additional toe variable angle-F toe angle correction amount (Formula 75)
[0240]
[76]
FL toe variable angle = previous value of FL toe variable angle + FL additional toe variable angle-F toe angle correction amount ... Formula 76
[0241]
[77]
RR toe variable angle = previous value of RR toe variable angle + RR additional toe variable angle ... Formula 77
[0242]
[Formula 78]
RL toe variable angle = previous value of RL toe variable angle + RL additional toe variable angle (Formula 78)
Note that the “F toe angle correction amount” in Expressions 75 and 76 is a virtual value for the front wheels 2FR and 2FL used when calculating the front target lateral force and the rear target lateral force in the target lateral force calculation process of FIG. This is a correct amount of toe angle correction. The “F toe angle correction amount” is reduced in the above formulas 75 and 76 because the front target lateral force and the rear target lateral force calculated by the target lateral force calculation process of FIG. 17 are the same for the front wheels 2FR and 2FL. This is because the toe angle is a value that can be realized by the front friction circle limit value and the rear friction circle limit value on the premise that the toe angle is reduced by the “F toe angle correction amount”.
[0243]
When the FR to RL toe variable angles are calculated in this way, the process proceeds to S1850. In S1850, the FR front / rear force addition amount calculated in the additional front / rear force distribution calculation process of FIG. 27 is read. In subsequent S1855, the “front / rear force additional amount vs. brake hydraulic pressure variable amount map” is read from the ROM.
[0244]
This “longitudinal force additional amount vs. brake hydraulic pressure variable amount map”, as shown in FIG. 30, shows the longitudinal force additional amount and the brake hydraulic pressure that should be added to the wheel braking device to obtain the longitudinal force additional amount. This is a data map in which a certain amount of brake hydraulic pressure is stored in correspondence with each other, and is prepared for each wheel 2FR, 2FL, 2RR, 2RL. When the longitudinal force addition amount is negative (acceleration direction), the brake hydraulic pressure variable amount is “0”. When the longitudinal force addition amount is positive (deceleration direction), the larger the value, The variable amount of brake hydraulic pressure is set so as to increase in the direction of increasing the braking force by the brake device (pressure increasing direction).
[0245]
Next, in subsequent S1860, the brake hydraulic pressure variable amount (FR brake hydraulic pressure variable amount) corresponding to the FR front / rear force additional amount read in S1850 is read in the “front / rear force additional amount vs. brake hydraulic variable amount map” read in S1855. ”Based on
Here, S1850 to S1860 have been described only for the right front wheel 2FR, but the other three wheels 2FL, 2RR, and 2RL are executed in exactly the same manner. Then, the FL brake hydraulic pressure variable amount, the RR brake hydraulic pressure variable amount, and the RL brake hydraulic pressure, which are brake hydraulic pressures to be added to the brake devices 26FL, 26RR, and 26RL in order to obtain the FL to RL longitudinal force additional amounts, respectively. Variable amounts are calculated respectively.
[0246]
When the brake hydraulic pressure variable amount for each wheel 2FR, 2FL, 2RR, 2RL is calculated in this way, the process proceeds to S1865, and the FR calculated by the additional longitudinal force distribution calculation process of FIG. The RL longitudinal force addition amount that is the sum of the RL longitudinal force addition amounts is calculated.
[0247]
[79]
Front / rear force additional amount = FR front / rear force additional amount + FL front / rear force additional amount + RR front / rear force additional amount + RL front / rear force additional amount
In subsequent S1870, the “additional longitudinal force amount vs. accelerator opening variable amount map” is read from the ROM.
[0248]
This “longitudinal force addition amount vs. accelerator opening variable amount map” is, as shown in FIG. 31, the longitudinal force addition amount calculated in S1865 and the accelerator opening necessary to obtain the longitudinal force addition amount. 4 is a data map in which accelerator opening variable amounts, which are changes in degrees (throttle valve opening), are stored in association with each other. When the additional amount of longitudinal force is positive (deceleration direction), the variable amount of accelerator opening is “0”, and when the additional amount of longitudinal force is negative (acceleration direction), the absolute value is large. The accelerator opening variable amount is set so as to increase in the direction of increasing the engine output (opening direction).
[0249]
Next, in the subsequent S1875, the accelerator opening variable amount corresponding to the front / rear force additional amount calculated in S1865 is calculated based on the “front / rear force additional amount vs. accelerator opening variable amount map” read in S1870.
In the subsequent S1880, the front limit value ratio calculated by the additional longitudinal force distribution calculation process of FIG. 27 is the ratio of the torque that the center differential gear should distribute to the front wheels 2FR, 2FL and the rear wheels 2RR, 2RL. The center differential longitudinal force distribution ratio is set.
[0250]
Further, in each of subsequent S1885 and S1890, based on the following formulas 80 and 81, the front differential front / rear force distribution ratio, which is the ratio of the torque that the front differential gear should distribute to each of the front wheels 2FR and 2FL, The rear differential gear calculates a rear differential longitudinal force distribution ratio, which is a ratio of torque to be distributed to each of the rear wheels 2RR and 2RL, and then ends the variable amount calculation process.
[0251]
[80]
Front differential longitudinal force distribution ratio = FR longitudinal force additional amount / (FR longitudinal force additional amount + FL longitudinal force additional amount)
[0252]
[Formula 81]
Rear differential longitudinal force distribution ratio = RR longitudinal force additional amount / (RR longitudinal force additional amount + RL longitudinal force additional amount) ... Formula 81
Here, the ECU 20 periodically executes a drive process (not shown) in parallel with the process of FIG. 2, and the toe control actuator is executed based on the calculation result in the variable amount calculation process by executing this drive process. Each of 22FR, 22FL, 22RR, 22RL, brake control actuator 28, accelerator control actuator 30, center differential control actuator 32C, front differential control actuator 32F, and rear differential control actuator 32R is controlled.
[0253]
Specifically, the ECU 20 first operates the toe control actuators 22FR, 22FL, 22RR, and 22RL in accordance with the FR to RL toe variable angles calculated in S1830 to S1845 of the variable amount calculation process, thereby causing each wheel 2FR, The toe angles of 2FL, 2RR, and 2RL are changed by the above-described FR to RL toe variable angles, respectively. And thereby, each wheel 2FR, 2FL, 2RR, 2RL will generate | occur | produce adding FR-RL lateral force additional amount.
[0254]
Further, the ECU 20 operates the brake control actuator 28 in accordance with the FR to RL brake hydraulic pressure variable amount calculated in S1860 of the variable amount calculation process, whereby the brake devices 26FR, 26FL, 26FR of the wheels 2FR, 2FL, 2RR, 2RL, The brake hydraulic pressure applied to 26RR and 26RL is increased by the above-described FR to RL brake hydraulic pressure variable amount. As a result, when the FR to RL longitudinal force addition amount is positive (deceleration direction), the braking force increases, and each wheel 2FR, 2FL, 2RR, 2RL has its FR to RL longitudinal force addition amount. Will be generated.
[0255]
On the other hand, the ECU 20 operates the accelerator control actuator 30 in accordance with the accelerator opening variable amount calculated in S1875 of the variable amount calculation process, thereby reducing the accelerator opening (throttle valve opening) to the accelerator opening variable amount. Change by minutes. Further, the ECU 20 operates the center differential control actuator 32C in accordance with the center differential longitudinal force distribution ratio set in S1880 of the variable amount calculation process, thereby obtaining the torque distribution ratio to the front and rear wheels by the center differential gear. The front differential control actuator 32F and the rear differential control actuator 32R are respectively controlled in accordance with the front differential front / rear force distribution ratio and the rear differential front / rear force distribution ratio calculated in S1885 and S1890 of the variable amount calculation processing. By operating, the torque distribution ratio to each front wheel 2FR, 2FL by the front differential gear is controlled to the above-mentioned center differential longitudinal force distribution ratio, and the torque to each rear wheel 2RR, 2RL by the rear differential gear is controlled. The distribution ratio is controlled to the rear differential longitudinal force distribution ratio.
[0256]
Then, by controlling the actuators 30, 32C, 32F, and 32R, the output of the engine is increased by the amount of additional front / rear force calculated in S1865 of the variable amount calculation process, and the increase in the engine output is When the driving force is distributed to each wheel 2FR, 2FL, 2RR, 2RL according to the mutual ratio of the FR to RL longitudinal force addition amount, as a result, the FR to RL longitudinal force addition amount is negative (acceleration direction). Each wheel 2FR, 2FL, 2RR, 2RL is generated by adding an additional amount of FR-RL longitudinal force.
[0257]
Next, when the ECU 20 finishes the variable amount calculation process of FIG. 28, the ECU 20 proceeds to S75 of FIG. In S75, the friction circle enlargement process shown in FIG. 32 is executed.
This friction circle enlarging process adjusts the camber angle of the wheel when there is no margin in the grip force of the wheel and lateral force can no longer be added by changing the toe angle. This is a process for enlarging the radius (that is, the maximum grip force that the wheel can generate).
[0258]
As shown in FIG. 32, when the ECU 20 starts executing the friction circle enlarging process, first, in S1900, it is determined whether or not the FR skid angle calculated in the four-wheel skid angle calculating process of FIG. 9 is larger than a predetermined value K10. judge. The predetermined value K10 is set to the value of the side slip angle at which the tire is considered to reach the limit.
[0259]
If the FR skid angle is larger than the predetermined value K10, the FR lateral force limit value set in the additional lateral force distribution calculation process of FIG. 25 (that is, the right front wheel 2FR is additionally generated) in the next S1905. It is determined whether or not the margin of possible lateral force is “0”. If the FR lateral force limit value is “0”, the front calculated in the additional force calculation process of FIG. Enter additional lateral force.
[0260]
On the other hand, if it is determined in S1900 that the FR skid angle is not greater than the predetermined value K10, or if it is determined in S1905 that the FR lateral force limit value is not “0” (that is, the right front wheel If 2FR can be generated by adding lateral force), the process proceeds to S1915, and the front additional lateral force is set to “0”.
[0261]
Then, after executing either S1910 or S1915, the process proceeds to S1920, and the “additional lateral force versus camber variable angle map” is read from the ROM.
As shown in FIG. 33, this “additional lateral force vs. camber variable angle map” is obtained by adding additional lateral force (front additional lateral force or rear additional lateral force) and camber control actuators 24FR, 24FL, 24RR, 24RL. Is a data map that stores the relationship with the camber variable angle indicating how many camber angles should be changed. When the additional lateral force is "0", the camber variable angle is "0" and the additional lateral force The camber variable angle is set to increase as the absolute value of increases.
[0262]
Then, in the subsequent S1925, the current front additional lateral force (that is, the value calculated by the additional force calculation processing of FIG. 21 when S1910 is executed, and “0” when S1915 is executed). ) Corresponding to the camber variable angle (FR camber variable angle) of the right front wheel 2FR is calculated based on the “additional lateral force vs. camber variable angle map” read in S1920, and then in S1930, the ground camber of FIG. The FR ground camber angle (actual ground camber angle of the right front wheel 2FR) calculated by the angle calculation process is input.
[0263]
Next, in S1935, it is determined whether or not the FR camber variable angle calculated in S1925 is larger than the absolute value of the FR ground camber angle. If the FR camber variable angle is not larger, the process proceeds to S1945. If the FR camber variable angle is larger, the value of the FR camber variable angle is reset to a value equal to the absolute value of the FR ground camber angle in S1940, and then the process proceeds to S1945.
[0264]
Then, in S1945, it is determined whether or not the FR ground camber angle is larger than “0”. If the FR ground camber angle is larger than “0”, the process proceeds to S1950 and the FR camber variable angle is set to “−1”. Is set as an FR camber angle control amount that is a change in the camber angle of the right front wheel 2FR to be adjusted by the camber control actuator 24FR. Conversely, if the FR ground camber angle is not larger than “0”, the process proceeds to S1955, and the FR camber variable angle is set as it is as the FR camber angle control amount.
[0265]
That is, in S1900 to S1955, when the FR skid angle is larger than the predetermined value K10 and the FR lateral force limit value is “0”, the lateral force of the right front wheel 2FR is no longer added by changing the toe angle. The FR camber angle control amount is set so that the ground camber angle of the right front wheel 2FR approaches 0 degrees (that is, the right front wheel 2FR is perpendicular to the ground). Yes. S1935 and S1940 are processes for preventing the FR camber angle control amount from becoming excessive. Conversely, if the FR skid angle is not larger than the predetermined value K10 or the FR lateral force limit value is not “0”, the FR camber angle control amount is set to “0” and the camber control actuator The camber angle control of the right front wheel 2FR by 24FR is stopped.
[0266]
After setting the FR camber angle control amount in this way, in each of the next S1960 to S1970, the camber angle of the left front wheel 2FL to be adjusted by the camber control actuator 24FL by the same procedure as S1900 to S1955 described above. FL camber angle control amount that is a change amount of RR, RR camber angle control amount that is a change amount of the camber angle of the right rear wheel 2RR to be adjusted by the camber control actuator 24RR, and left rear wheel that is to be adjusted by the camber control actuator 24RL The RL camber angle control amount, which is the change in the 2RL camber angle, is set.
[0267]
When the FL camber angle control amount is set in S1960, processing is performed in which the alphabet “FR” used in S1900 to S1955 in FIG. 32 is replaced with the alphabet “FL”.
Further, when setting the RR camber angle control amount and the RL camber angle control amount in each of S1965 and S1970, the alphabet “FR” used in S1900 to S1955 in FIG. In this case, in step S1910, the rear additional lateral force calculated by the additional force calculation processing of FIG. 21 is input. In S1915, the rear additional lateral force is input. Set the force to “0”. In S1925, the camber variable angle (RR camber variable angle, RL camber variable angle) corresponding to the rear additional lateral force is calculated based on the “additional lateral force vs. camber variable angle map”.
[0268]
Thus, when the FL to RL camber angle control amount is set by the processing of S1960 to S1970, the friction circle enlarging processing is terminated. After that, when the next processing cycle arrives, the process returns to S10 in FIG. 2 to start execution of the four-wheel load calculation process, and each process shown in FIG. 2 is sequentially executed again.
[0269]
Note that the ECU 20 reads the FR to RL camber angle control amount set in the friction circle enlarging process in the above-described driving process executed in parallel with the process of FIG. 2, and according to the FR to RL camber angle control amount. Then, by operating the camber control actuators 24FR, 24FL, 24RR, and 24RL, the camber angles of the wheels 2FR, 2FL, 2RR, and 2RL are changed by the above-described FR to RL camber angle control amounts.
[0270]
As a result, with respect to a wheel that has no margin in grip force and can no longer add lateral force by changing the toe angle, the ground camber angle of the wheel is brought close to 0 degrees, and the maximum possible generation of the wheel is achieved. The grip power of increases. Then, when the ECU 20 next executes the four-wheel friction circle estimation calculation process of FIG. 13, the ground camber angle of the wheel is close to 0 degrees. The friction circle reduction coefficient calculated based on the “coefficient map” becomes a value closer to “1”. As a result, the estimated friction circle value of the wheel is also calculated as a large value. Therefore, the actual friction circle radius of the wheel and the estimated friction circle used in the control are expanded, and the performance of the tire mounted on the wheel can be utilized to the maximum.
[0271]
As described in detail above, in the present embodiment, the forces that can be generated between the wheels 2FR, 2FL, 2RR, and 2RL with the road surface by the four-wheel friction circle estimation calculation process of FIG. 13 as the friction circle setting means. The maximum value of the resultant force is set as an estimated value of FR to RL friction circle that is the radius of the friction circle.
[0272]
Then, the lateral G sensor 6, the yaw rate sensor 8, the front / rear G sensor 10 as the running state detection means, and the detection process (not shown) detect the yaw rate, the lateral G, and the front / rear G, which are actual physical physical quantities of the vehicle body, and are generated. From the detected actual yaw rate, lateral G, and longitudinal G, the wheels 2FR, 2FL, 2RR, 2RL are determined to be in the lateral direction by the lateral force computation process of FIG. 4 and the longitudinal force computation process of FIG. The lateral force and longitudinal force actually generated in the longitudinal direction are calculated.
[0273]
The value obtained by dividing the front lateral force calculated in the lateral force calculation process of FIG. 4 by 2 is used as the actual lateral force of each of the front wheels 2FR and 2FL, and the rear lateral force calculated in the same lateral force calculation process is 2. The divided value is used as the actual lateral force of each rear wheel 2RR, 2RL. Similarly, a value obtained by dividing the front longitudinal force calculated by the longitudinal force calculation processing of FIG. 5 by 2 is used as the actual longitudinal force of each front wheel 2FR, 2FL, and the rear longitudinal force 2 similarly calculated by the longitudinal force calculation processing is also used. The value divided by is used as the actual longitudinal force of each rear wheel 2RR, 2RL.
[0274]
Further, by the friction circle margin calculation process of FIGS. 22 and 23 and the longitudinal force margin calculation process of FIG. 26 as the margin calculation means, the lateral force and the actual force generated by each wheel 2FR, 2FL, 2RR, 2RL and Based on the longitudinal force and the estimated FR to RL friction circle value, the FR to RL lateral force positive additional limit value, which is a margin of force that can be generated by adding each wheel 2FR, 2FL, 2RR, 2RL in the lateral direction, and FR to RL lateral force negative additional limit value, FR to RL front and rear force positive additional limit value and FR to RL before and after that is the margin of force that can be generated by adding each wheel 2FR, 2FL, 2RR, 2RL in the front-rear direction The force negative additional limit value is calculated.
[0275]
  Further, the target yaw rate of the vehicle body according to the operation of the driver by the processing as the target setting means consisting of S1005 to S1030 in the target lateral force calculation processing of FIG. 17 and S1110 to S1180 in the target longitudinal force calculation processing of FIG. The target lateral G and the target longitudinal G are set, and further, S1035 to S1050 in the target lateral force calculation process of FIG. 17, S1190 in the target longitudinal force calculation process of FIG. 18, the additional force calculation process of FIG. 21, and the addition of FIG. By the processing as the additional force setting means including the lateral force distribution calculation processing and the additional front / rear force distribution calculation processing of FIG. 27, each wheel is moved in the lateral direction and the front / rear to realize the target yaw rate, the target lateral G, and the target front / rear G. FR to RL lateral force addition amount and FR to RL longitudinal force addition amount, which are the magnitudes of the force that should be generated by adding to each direction, FR to RL lateral force positive tracking Depending on the limit values and FR~RL lateral force negative additional limit value and FR~RL longitudinal force positive additional limit values and FR~RL longitudinal force negative additional limit value, within which additional limit valueYieldIt is set to be full.
[0276]
Then, by the variable amount calculation process of FIG. 28 as the drive control means and the drive process (not shown), each wheel is generated by adding the FR to RL lateral force addition amount and the FR to RL longitudinal force addition amount. The toe control actuators 22FR, 22FL, 22RR, 22RL as force adjusting means, the brake control actuator 28, the accelerator control actuator 30, the center differential control actuator 32C, the front differential control actuator 32F, and the rear differential control actuator 32R are operated.
[0277]
In other words, in the present embodiment, the magnitude of the lateral force and the longitudinal force actually generated by each wheel is obtained, and the magnitude of the obtained force and the FR to RL friction that is the frictional circle radius estimated for each wheel. The margin between the lateral force and the longitudinal force of each wheel is obtained from the estimated circle value. Then, within the range of the margin, the actual yaw rate, lateral G, and longitudinal G of the vehicle body can be obtained by adding the generated force in the lateral direction and the longitudinal direction of each wheel (positive addition or negative addition). The target yaw rate, the target lateral G, and the target longitudinal G are set so that the resultant force of the force generated between each wheel and the road surface does not exceed the estimated FR-RL friction circle. Controls the magnitude and direction of the generated force.
[0278]
For this reason, according to this embodiment, while making the best use of the gripping force that can be generated by each wheel, the driving state of the vehicle is set to the target driving state within a range that does not exceed the limit of the gripping force of each wheel. And the limit of the entire vehicle can be made very high. Therefore, the running stability of the vehicle can be made extremely high.
Further, in the present embodiment, the set target yaw rate and the target lateral G are expressed as FR to RL friction circle estimated values of the respective wheels by the processing as the target correcting means including S1055 to S1070 in the target lateral force calculation processing of FIG. It is determined whether or not it can be realized by the applied force, and when it is determined that it cannot be realized (S1060: NO, S1065: NO), the target yaw rate and the target lateral G are represented by FR to RL friction circle estimated values. The value is corrected to a realizable value by the force.
[0279]
Therefore, for example, even if the driver operates the steering wheel suddenly and greatly during high speed driving and the target yaw rate and the target lateral G are set to be extremely large, the values can be realized with the force that each wheel can generate. Therefore, the vehicle is surely prevented from exceeding the limit, and the running stability of the vehicle can be reliably maintained.
[0280]
On the other hand, in this embodiment, the load of each wheel is detected by the four-wheel load calculation process of FIG. 3 as the load detection means, and the ground camber angle calculation process of FIG. 11 as the camber angle detection means is detected. The ground camber angle is detected, the friction coefficient of the traveling road surface is detected by the road surface μ estimation calculation process of FIGS. 7 and 8 as the friction coefficient detection means, and the tire type determination calculation process of FIG. The grip performance level of the tire mounted on the wheel is detected.
[0281]
In the four-wheel friction circle estimation calculation process of FIG. 13, the larger the wheel load, the closer the wheel camber angle to 0 degrees, the greater the friction coefficient of the road surface, and the higher the tire grip performance level. The friction circle estimated value (FR to RL friction circle estimated value) of each wheel is set to a large value.
[0282]
For this reason, since the setting accuracy of the FR to RL friction circle estimated value is increased and the margin of force that can be generated by each wheel can be calculated more accurately, the grip force that can be generated by the wheel can be more reliably utilized. .
In this embodiment, the camber control actuators 24FR, 24FL, 24RR, and 24RL, the camber angle control means including the friction circle expanding process of FIG. A wheel that does not exist is specified, and the ground camber angle of the specified wheel is adjusted to approach 0 degrees.
[0283]
For this reason, even if a wheel cannot generate a force additionally, the grip force that the wheel can generate is increased, and the ground camber angle is brought close to 0 degrees, so that the wheel is set for the wheel. Since the estimated friction circle for control is also increased, the performance of the tire mounted on the wheel can be maximized.
[0284]
By the way, the ECU 20 of the above embodiment sets the target yaw rate, the target lateral G, and the target longitudinal G based on the operation state of the steering and the accelerator pedal by the vehicle driver. However, a person does not drive the vehicle. When the vehicle is automatically steered by a command from the outside, the ECU 22 inputs the target yaw rate, the target lateral G, and the target longitudinal G from the outside, and the input values are processed in the processing of FIGS. 17 and 18. It should be used. In this case, when a negative determination is made in S1060 or S1065 of FIG. 17, the value of the target yaw rate itself is corrected to a small value in S1070, and thereafter, the processing after S1030 may be repeated.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram illustrating a configuration of an entire vehicle control system according to an embodiment.
FIG. 2 is a flowchart showing an entire process executed by the ECU of FIG.
FIG. 3 is a flowchart showing a four-wheel load calculation process in FIG. 2;
4 is a flowchart showing a lateral force calculation process in FIG. 2. FIG.
FIG. 5 is a flowchart showing a longitudinal force calculation process in FIG. 2;
6 is an explanatory diagram for explaining a longitudinal G vs. longitudinal force map referred to in the longitudinal force calculation process of FIG. 5. FIG.
FIG. 7 is a flowchart showing the first half of the road surface μ estimation calculation process in FIG. 2;
FIG. 8 is a flowchart showing the second half of the road surface μ estimation calculation process in FIG. 2;
FIG. 9 is a flowchart showing a four-wheel skid angle calculation process in FIG.
FIG. 10 is a flowchart showing a tire type determination calculation process in FIG.
FIG. 11 is a flowchart showing ground camber angle calculation processing in FIG. 2;
12 is an explanatory diagram for explaining a height vs. camber angle change amount map referred to in the ground camber angle calculation processing of FIG.
13 is a flowchart showing a four-wheel friction circle estimation calculation process in FIG. 2. FIG.
14 is an explanatory diagram for explaining a load-to-friction circle map referred to in the four-wheel friction circle estimation calculation process of FIG. 13; FIG.
FIG. 15 is an explanatory diagram illustrating a ground camber angle versus friction circle reduction coefficient map referred to in the four-wheel friction circle estimation calculation process of FIG. 13;
FIG. 16 is a flowchart showing a target traveling state setting process in FIG.
FIG. 17 is a flowchart showing a target lateral force calculation process executed in the target travel state setting process of FIG.
18 is a flowchart showing a target longitudinal force calculation process executed in the target travel state setting process of FIG.
FIG. 19 is an explanatory diagram illustrating an accelerator state vs. target front / rear G map referred to in the target front / rear force calculation processing of FIG. 18;
FIG. 20 is an explanatory diagram illustrating a brake pedal force vs. target front / rear G map referred to in the target front / rear force calculation process of FIG. 18;
FIG. 21 is a flowchart showing additional force calculation processing in FIG. 2;
FIG. 22 is a flowchart showing the first half of the friction circle margin calculation process in FIG. 2;
FIG. 23 is a flowchart showing the latter half of the friction circle margin calculation process in FIG. 2;
FIG. 24 is a flowchart showing an additional force distribution process in FIG.
25 is a flowchart showing an additional lateral force distribution calculation process executed in the additional force distribution process of FIG. 24. FIG.
FIG. 26 is a flowchart showing a longitudinal force margin calculation process executed in the additional force distribution process of FIG.
FIG. 27 is a flowchart showing an additional longitudinal force distribution calculation process executed in the additional force distribution process of FIG.
FIG. 28 is a flowchart showing variable amount calculation processing in FIG. 2;
29 is an explanatory diagram for explaining a lateral force addition amount vs. additional toe variable angle map referred to in the variable amount calculation processing of FIG. 28;
30 is an explanatory diagram for explaining a front / rear force addition amount vs. brake hydraulic pressure variable amount map referred to in the variable amount calculation processing of FIG. 28;
FIG. 31 is an explanatory diagram for explaining a front / rear force addition amount vs. accelerator opening variable amount map referred to in the variable amount calculation processing of FIG. 28;
32 is a flowchart showing a friction circle enlarging process in FIG. 2. FIG.
33 is an explanatory diagram illustrating an additional lateral force vs. camber variable angle map referred to in the friction circle enlarging process of FIG. 32. FIG.
[Explanation of symbols]
2FR, 2FL, 2RR, 2RL ... Wheel 4FR, 4FL, 4RR, 4RL ... Wheel speed sensor
5FR, 5FL, 5RR, 5RL ... Height sensor 6 ... Horizontal G sensor
8 ... Yaw rate sensor 10 ... Front / back G sensor
12 ... Steering angle sensor 13 ... Brake switch
16 ... Brake pedal force sensor 18 ... Accelerator opening sensor
20 ... Electronic control unit (ECU)
22FR, 22FL, 22RR, 22RL ... Toe control actuator
24FR, 24FL, 24RR, 24RL ... Camber control actuator
26FR, 26FL, 26RR, 26RL ... Brake device
28 ... Brake control actuator
30 ... Accelerator control actuator
32C ... Center differential control actuator
32F ... Front differential control actuator
32R ... Rear differential control actuator

Claims (10)

Friction circle setting means for setting the maximum value of the resultant force for each wheel of the four front and rear, left and right wheels of the vehicle that can be generated with the road surface as the radius of the friction circle for each wheel;
Generated force adjusting means for changing the magnitude of the longitudinal force (hereinafter referred to as longitudinal force) and the lateral force (hereinafter referred to as lateral force) generated between each wheel and the road surface;
A driving state detecting means for detecting a physical quantity of movement of the vehicle body that occurs as the vehicle travels;
From motion physical value detected by the running condition detecting means, and generating force calculating means for calculating the magnitude of the longitudinal force and lateral force each wheel is occurred,
Wherein for each wheel, wherein the radius of the friction circle set by friction circle setting means, based on the magnitude of the longitudinal force and the lateral force calculated by the generating force calculating means, can be generated wherein each wheel is to add Margin calculating means for calculating the margin of longitudinal force and lateral force ,
Target setting means for setting a target value of the exercise physical quantity;
Front additional lateral force, which is the total lateral force that must be additionally generated by both front wheels, in order for the physical movement quantity detected by the running state detection means to be the target value set by the target setting means , Added to calculate the rear additional lateral force that is the total lateral force that must be generated by the addition of both rear wheels and the additional vehicle longitudinal force that is the total longitudinal force that must be generated by the addition of the four wheels. performs power calculation process, an additional force setting means for performing distribution processing for distributing the force calculated in the additional force calculation process Previous Symbol each wheel,
Drive control means for operating the generated force adjusting means so that each wheel additionally generates the force distributed by the additional force setting means ,
The additional force setting means, as the distribution process,
Ratio of margin of lateral force between the left front wheel and right front wheel (hereinafter referred to as “first ratio”) and ratio of margin of lateral force between the left rear wheel and right rear wheel (hereinafter referred to as “second ratio”). And a marginal force addition ratio indicating that 10% of the front additional lateral force and the rear additional lateral force calculated in the additional force calculation process can be actually added is represented by 100% by the margin calculation means. A first process for calculating from the calculated margin of lateral force of each wheel;
If the lateral force addition possibility ratio is 1 or less, each value obtained by multiplying each of the front additional lateral force and rear additional lateral force calculated by the additional force calculation process by the lateral force addition possibility ratio is added to the distribution target front. If the lateral force and the rear additional lateral force are greater than 1, then the front additional lateral force and the rear additional lateral force calculated by the additional force calculation process are directly used as the front additional lateral to be distributed. A second process for force and rear additional lateral force;
The front additional lateral force to be distributed is distributed between the left front wheel and the right front wheel at the first ratio, and the rear additional lateral force to be distributed is distributed between the left rear wheel and the right rear wheel at the second ratio. A third process of allocating to
The ratio of the margin of front / rear force between the front wheels and the rear wheels (hereinafter referred to as the third ratio) and the percentage of the additional vehicle front / rear force calculated by the additional force calculation process can be actually increased by 10%. A fourth process of calculating a longitudinal force addition possible ratio shown as 1 from the margin of the longitudinal force of each wheel calculated by the margin calculating means;
If the longitudinal force addition possibility ratio is 1 or less, a value obtained by multiplying the additional vehicle longitudinal force calculated by the additional force calculation process by the longitudinal force addition possibility ratio is set as an additional vehicle longitudinal force to be distributed, and the longitudinal force addition is performed. If the possible ratio is greater than 1, a fifth process in which the additional vehicle longitudinal force calculated in the additional force calculation process is directly used as an additional vehicle longitudinal force to be distributed;
Half of the additional vehicle longitudinal force to be distributed is distributed to the left front wheel and the left rear wheel at the third ratio, and the other half of the additional vehicle longitudinal force to be allocated is to the right at the third ratio. Performing a sixth process of allocating to the front wheel and the right rear wheel;
Vehicle control device according to claim. The vehicle control device according to claim 1 ,
The generated force adjusting means includes
It is configured to change the longitudinal force and lateral force of each wheel by adjusting the braking force and driving force applied to each wheel and the steering angle of each wheel,
A vehicle control device. In the vehicle control device according to claim 1 or 2 ,
Whether or not the target value set by the target setting means can be realized by the force represented by the radius of the friction circle of each wheel set by the friction circle setting means is determined by the physical physical quantity of the target value. The sum of the forces in a specific direction to be generated by a plurality of specific wheels (hereinafter referred to as a necessary value) to generate the vehicle on the vehicle body, and the radius of the friction circle set by the friction circle setting means for each of the specific wheels When the target value is determined to be unrealizable because the limit value is not larger than the required value, the target value is determined to be unrealizable. A target correction unit that corrects the value to a value that is determined to be realizable by the determination, in which the limit value is larger than the necessary value;
A vehicle control device. The vehicle control device according to any one of claims 1 to 3 ,
A load detecting means for detecting a load applied to each wheel;
The friction circle setting means includes
The larger the load detected by the load detection means, the larger the radius of the friction circle is set to a value,
A vehicle control device. The vehicle control device according to any one of claims 1 to 4 ,
A camber angle detecting means for detecting a ground camber angle of each wheel;
The friction circle setting means includes
The ground camber angle detected by the camber angle detection means is configured to set the radius of the friction circle to a larger value as the ground camber angle is closer to 0 degrees.
A vehicle control device. The vehicle control device according to claim 5 , wherein
A camber angle control unit that identifies a wheel having no margin calculated by the margin calculation unit and adjusts the ground camber angle of the identified wheel to approach 0 degree;
A vehicle control device. The vehicle control device according to any one of claims 1 to 6 ,
Friction coefficient detection means for detecting the friction coefficient of the road surface of the vehicle,
The friction circle setting means includes
It is configured to set the radius of the friction circle to a larger value as the friction coefficient detected by the friction coefficient detection means is larger.
A vehicle control device. The vehicle control device according to any one of claims 1 to 7 ,
Tire determining means for detecting the grip performance level of the tire mounted on each wheel,
The friction circle setting means includes
The tire determining means is configured to set the radius of the friction circle to a larger value as it is determined that the tire grip performance level is higher.
A vehicle control device. The vehicle control device according to any one of claims 1 to 8 ,
The running state detecting means detects a yaw rate as the physical exercise quantity,
The target setting means sets a target value of the yaw rate;
A vehicle control device. The vehicle control device according to any one of claims 1 to 8 ,
The running state detecting means detects lateral acceleration as the exercise physical quantity,
The target setting means sets a target value of lateral acceleration;
A vehicle control device.

Images