JP2004025996A - Motion control device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve more favorable motion control of a vehicle by computing a target value for the lateral force of a front wheel and a target value for the lateral force of a rear wheel instead of a target value for the lateral force of the vehicle. <P>SOLUTION: Target longitudinal force Fxa, front wheel lateral force Fyfa, rear wheel lateral force Fyra and moment Ma as the sums of the longitudinal force, front wheel lateral force, rear wheel lateral force and moment of a vehicle and target longitudinal force Fxt and target moment Mt with the slip ratio Si of each wheel being zero are computed (S250), micro-coefficients showing changes dFx, dFyf, dFyr, dM in the longitudinal force, front wheel lateral force, rear wheel lateral force and moment with a micro-change dSi in the slip ratio are computed, correction amounts δFx, δFyf, δFyr, δM of the longitudinal force, front wheel lateral force, rear wheel lateral force and moment are computed in accordance with differences between each of target values and each of actual values and the micro-coefficients by convergence computation where the weighting of the rear wheel lateral force is greater than that of the front wheel lateral force (S200-350), and correction amount δSi of the slip ratio is computed to achieve the correction amount. The braking force of each wheel is controlled by using a target slip ratio obtained by correcting the former target slip ratio with δSi (S400-550). <P>COPYRIGHT: (C)2004,JPO

Description

【００１５】
尚係数Ｋｂ　は図１４に示されている如く、スリップ率Ｓｉ　が０であるときのタイヤのスリップ角βｉ　に対する横力Ｆｔｙｉ　のグラフの原点に於ける傾きであり、係数Ｋｓ　は図１５に示されている如く、スリップ角βｉ　が０であるときのタイヤのスリップ率Ｓｉ　に対する前後力Ｆｔｘｉ　のグラフの原点に於ける傾きである。また　ｃｏｓθ、　ｓｉｎθ、λ、ξはそれぞれ下記の式５〜８にて表される。
【００１６】
【数２】

【００１７】
上記式１〜４をスリップ率Ｓｉ　にて偏微分することにより、微小なスリップ率の変化に対する前後力変化及び横力変化（タイヤ座標系）を演算する（下記の式９及び１０）。
【００１８】
【数３】

【００１９】
次に下記の式１１〜１８に従って右前輪（ｆｒ）、左前輪（ｆｌ）、右後輪（ｒｒ）、左後輪（ｒｌ）の各タイヤの前後力及び横力（タイヤ座標系）を車輌座標系に変換して車輌の重心に作用する前後力Ｆｘｉ及び横力Ｆｙｉを演算すると共に、モーメントＭｉ　を演算する。尚下記の各式に於いて、φｆ　及びφｒ　はそれぞれ前輪及び後輪の舵角であり、Ｔｒ　は車輌のトレッド幅であり、Ｌｆ　及びＬｒ　はそれぞれ車輌の重心から前輪車軸及び後輪車軸までの距離であり、Ｔ（φｆ　）及びＴ（φｒ　）はそれぞれ下記の式１９及び２０にて表される値である。
【００２０】
【数４】

【００２１】
【数５】

【００２２】
【数６】

【００２３】
【数７】

【００２４】
【数８】

【００２５】
同様に、下記の式２１〜２８に従って右前輪（ｆｒ）、左前輪（ｆｌ）、右後輪（ｒｒ）、左後輪（ｒｌ）の各タイヤの前後力及び横力の偏微分値（タイヤ座標系）を車輌座標系に変換して車輌に作用する前後力及び横力の偏微分値（微係数）を演算すると共に、モーメントの偏微分値（微係数）を演算する。
【００２６】
【数９】

【００２７】
【数１０】

【００２８】
【数１１】

【００２９】
【数１２】

【００３０】
次に各輪のスリップ率が目標スリップ率Ｓｉ　であるときに発生する車輌の前後力Ｆｘ　、前輪横力Ｆｙｆ、後輪横力Ｆｙｒ、モーメントＭをそれぞれ各輪による前後力Ｆｘｉ、前輪横力Ｆｙｆｒ及びＦｙｆｌ、後輪横力Ｆｙｒｒ　及びＦｙｒｌ　、モーメントＭｉ　の和として下記の式２９に従って推定演算する。
【００３１】
【数１３】

【００３２】
次に下記の（Ａ）及び（Ｂ）の考え方に基づき、下記の式３０及び３１に従って目標前後力Ｆｘａ、目標前輪横力Ｆｙｆａ　、目標後輪横力Ｆｙｒａ　、目標モーメントＭａ　を演算する。尚下記の式３０の右辺はスリップ率が０であるときに各輪により発生される前後力、横力、モーメントを表している。
【００３３】
（Ａ）車輌の運動制御により車輌の挙動を安定化させるための目標前後力Ｆｘｔ及び目標モーメントＭｔ　は運動制御していないとき（スリップ率Ｓｉ　が０であるとき）に発生する前後力Ｆｘｓｏ　及びモーメントＭｓｏに対する上乗せ量であると見なす。
【００３４】
（Ｂ）運動制御していないときの前輪横力Ｆｙｆｓｏ　及び後輪横力Ｆｙｒｓｏをそれぞれ目標前輪横力Ｆｙｆａ　及び目標後輪横力Ｆｙｒａ　とすることにより、運動制御時の横力の低下を極力減らす。
【００３５】
【数１４】

【００３６】
被制御４輪のスリップ率の微小な変化ｄＳｉ　による車体に作用する前後力の変化ｄＦｘ　、前輪横力の変化ｄＦｙｆ、後輪横力の変化ｄＦｙｒ、モーメントの変化ｄＭは下記の式３２により表される。尚下記の式３２に於いて、ｄＳｆｒ、ｄＳｆｌ、ｄＳｒｒ、ｄＳｒｌはそれぞれ右前輪、左前輪、右後輪、左後輪のスリップ率の微小変化量であり、Ｊはヤコビ行列である。
【００３７】
【数１５】

【００３８】
次に目標前後力Ｆｘａ、目標前輪横力Ｆｙｆａ　、目標後輪横力Ｆｙｒａ　、目標モーメントＭａ　を実現するスリップ率Ｓｉ　を演算する。ただしこのスリップ率を解析的に解くことは困難であるため、以下の収束演算により求める。
【００３９】
いま現在の前後力、前輪横力、後輪横力、モーメントと目標前後力、目標前輪横力、目標後輪横力、目標モーメントとの差をΔとすると、Δは下記の式３３により表され、このΔを０にするスリップ率修正量のうち、Ｔをトランスポートとして下記の式３４にて表される評価関数Ｌを最小化するスリップ率修正量δＳを求める。
【００４０】
【数１６】

Ｌ＝δＳ^ＴＷｄｓδＳ＋（Ｓ＋δＳ）^ＴＷｓ　（Ｓ＋δＳ）＋Ｅ^ＴＷｆ　Ｅ……（３４）
【００４１】
式３４の評価関数Ｌを最小化するスリップ率修正量δＳは、上記式３４に於いて∂Ｌ／∂δＳ＝０として下記の式３５の通りである。
δＳ＝（Ｗｄｓ＋Ｗｓ　＋Ｊ^ＴＷｆ　Ｊ）^−１（−Ｗｓ　Ｓ＋Ｊ^ＴＷｆ　Δ）……（３５）
【００４２】
ただしＦｘ　、Ｆｙｆ、Ｆｙｒ、Ｍはそれぞれ現在の被制御輪のスリップ率で発生している前後力、前輪横力、後輪横力、モーメント（式２９）であり、Ｆｘａ、Ｆｙｆａ、Ｆｙｒａ　、Ｍａ　はそれぞれ目標前後力、目標前輪横力、目標後輪横力、目標モーメント（式３１）であり、Ｓ及びδＳはそれぞれ各輪のスリップ率（下記の式３６）及びスリップ率修正量（下記の式３７）であり、ＥはΔとδＳによる前後力、前輪横力、後輪横力、モーメントの修正量との差（下記の式３８）であり、Ｗｄｓはスリップ率修正量δＳに対する重み（下記の式３９）であり、Ｗｓ　はスリップ率Ｓに対する重み（下記の式４０）であり、Ｗｆ　は各力に対する重み（下記の式４１）であり、各重みは０又は正の値である。また下記の式４１の重みＷｆのうち、後輪横力に対する重みＷＦｙｒは前輪横力に対する重みＷＦｙｆよりも大きい値である。
【００４３】
【数１７】

【００４４】
【数１８】

【００４５】
【数１９】

【００４６】
【数２０】

【００４７】
【数２１】

【００４８】
【数２２】

【００４９】
従って前回の目標スリップ率Ｓｉ　をスリップ率修正量δＳｉ　にて修正することにより、目標前後力Ｆｘａ、目標前輪横力Ｆｙｆａ、目標後輪横力Ｆｙｒａ、目標モーメントＭａ　を達成する各輪の目標スリップ率Ｓｉ　を演算することができる。
【００５０】
尚上記式３４の評価関数Ｌは１〜４をそれぞれ右前輪、左前輪、右後輪、左後輪を意味するとして、下記の式５１を行列表現したものであり、上記式３４の評価関数Ｌは上述の先の提案にかかる特開平１１−３４８７５３号に於ける評価関数の基礎式（下記の式５２）を行列表現したものと同一になる。
【００５１】
【数２３】

【００５２】
【数２４】

【００５３】
【課題解決手段の好ましい態様】
本発明の一つの好ましい態様によれば、上記請求項１の構成に於いて、各輪の目標制御量を算出する手段は「実際の車輌状態量とその目標値との偏差」と「微係数と目標制御量の変化量との積」との差、目標制御量の変化量、目標制御量とその変化量との和の二乗和からなる評価関数の値が最小になるよう各輪の目標制御量の変化量を収束演算により算出し、目標制御量の変化量にて前回算出された目標制御量を修正するよう構成される（好ましい態様１）。
【００５４】
本発明の他の一つの好ましい態様によれば、上記好ましい態様１の構成に於いて、前記二乗和の演算に際し「実際の後輪横力とその目標値との偏差」の重みが「実際の前輪横力とその目標値との偏差」の重みよりも大きく設定されるよう構成される（好ましい態様２）。
【００５５】
本発明の他の一つの好ましい態様によれば、上記請求項１の構成に於いて、タイヤモデルは制動時の横力の低下、荷重移動、タイヤスリップ角、路面の摩擦係数を考慮したタイヤモデルであるよう構成される（好ましい態様３）。
【００５６】
本発明の他の一つの好ましい態様によれば、上記請求項１の構成に於いて、各輪の目標制御量は目標スリップ率であるよう構成される（好ましい態様４）。
【００５７】
本発明の他の一つの好ましい態様によれば、上記請求項１の構成に於いて、各輪の目標制御量は目標スリップ率であるよう構成される（好ましい態様５）。
【００５８】
本発明の他の一つの好ましい態様によれば、上記請求項１の構成に於いて、車輪制御量は車輪のスリップ率であるよう構成される（好ましい態様６）。
【００５９】
本発明の他の一つの好ましい態様によれば、上記請求項１の構成に於いて、車輪操作装置は車輪の制駆動力を制御する装置であるよう構成される（好ましい態様７）。
【００６０】
本発明の他の一つの好ましい態様によれば、上記請求項２の構成に於いて、全ての車輪のスリップ率が零であるときの前輪横力及び後輪横力が推定され、該前輪横力及び後輪横力がそれぞれ目標前輪横力及び目標後輪横力に設定されるよう構成される（好ましい態様８）。
【００６１】
本発明の他の一つの好ましい態様によれば、上記好ましい態様３の構成に於いて、タイヤモデルはブラッシュタイヤモデルであるよう構成される（好ましい態様９）。
【００６２】
本発明の他の一つの好ましい態様によれば、上記請求項１の構成に於いて、後輪の目標スリップ率は０に低減されるよう構成される（好ましい態様１０）。
【００６３】
本発明の他の一つの好ましい態様によれば、上記請求項１の構成に於いて、重み設定手段は車輪のスリップ角の符号及びヨーモーメントの符号に基づき当該車輪の目標スリップ率の変化量に対する重みを可変設定するよう構成される（好ましい態様１１）。
【００６４】
【発明の実施の形態】
以下に添付の図を参照しつつ、本発明を好ましい実施形態について詳細に説明する。
【００６５】
図１は本発明による車輌の運動制御装置の一つの好ましい実施形態を示す概略構成図である。
【００６６】
図１に於て、１０ＦＬ及び１０ＦＲはそれぞれ車輌１２の左右の前輪を示し、１０ＲＬ及び１０ＲＲはそれぞれ車輌の駆動輪である左右の後輪を示している。従動輪であり操舵輪でもある左右の前輪１０ＦＬ及び１０ＦＲは運転者によるステアリングホイール１４の転舵に応答して駆動されるラック・アンド・ピニオン式のパワーステアリング装置１６によりタイロッド１８Ｌ　及び１８Ｒ　を介して操舵される。
【００６７】
各車輪の制動力は制動装置２０の油圧回路２２によりホイールシリンダ２４ＦＲ、２４ＦＬ、２４ＲＲ、２４ＲＬの制動圧が制御されることによって制御されるようになっている。図には示されていないが、油圧回路２２はリザーバ、オイルポンプ、種々の弁装置等を含み、各ホイールシリンダの制動圧は通常時には運転者によるブレーキペダル２６の踏み込み操作に応じて駆動されるマスタシリンダ２８により制御され、また必要に応じて後に詳細に説明する如く電気式制御装置３０により制御される。
【００６８】
車輪１０ＦＲ〜１０ＲＬにはそれぞれ車輪速度Ｖｗｉ（ｉ＝ｆｒ、ｆｌ、ｒｒ、ｒｌ）を検出する車輪速度センサ３２ＦＲ、３２ＦＬ、３２ＲＲ、３２ＲＬが設けられ、ステアリングホイール１４が連結されたステアリングコラムには操舵角φを検出する操舵角センサ３４が設けられている。また車輌１２にはそれぞれ車輌のヨーレートγを検出するヨーレートセンサ３６、前後加速度Ｇｘ　を検出する前後加速度センサ３８、横加速度Ｇｙ　を検出する横加速度センサ４０、車速Ｖを検出する車速センサ４２が設けられている。尚操舵角センサ３４、ヨーレートセンサ３６及び横加速度センサ４０は車輌の左旋回方向を正としてそれぞれ操舵角、ヨーレート及び横加速度を検出する。
【００６９】
図示の如く、車輪速度センサ３２ＦＲ〜３２ＲＬにより検出された車輪速度Ｖｗｉを示す信号、操舵角センサ３４により検出された操舵角φを示す信号、ヨーレートセンサ３６により検出されたヨーレートγを示す信号、前後加速度センサ３８により検出された前後加速度Ｇｘ　を示す信号、横加速度センサ４０により検出された横加速度Ｇｙ　を示す信号、車速センサ４２により検出された車速Ｖを示す信号は電気式制御装置３０に入力される。尚図には詳細に示されていないが、電気式制御装置３０は例えばＣＰＵとＲＯＭとＲＡＭと入出力ポート装置とを有し、これらが双方向性のコモンバスにより互いに接続された一般的な構成のマイクロコンピュータを含んでいる。
【００７０】
電気式制御装置３０は、後述の如く図２乃至図７に示されたフローチャートに従い、各輪のスリップ率Ｓｉ　が０であるときの車輌の前後力Ｆｘｓｏ　、前輪横力Ｆｙｆｓｏ、後輪横力Ｆｙｒｓｏ、モーメントＭｓｏと車輌の挙動を安定化させるための目標前後力Ｆｘｔ及び目標モーメントＭｔ　との和として車輌の目標前後力Ｆｘａ、目標前輪横力Ｆｙｆａ、目標後輪横力Ｆｙｒａ、目標モーメントＭａ　を演算し、各輪のスリップ率の微小な変化ｄＳｉ　に対する車輌の前後力、前輪横力、後輪横力、モーメントの変化ｄＦｘ　、ｄＦｙｆ、ｄＦｙｒ、ｄＭを示す微係数∂Ｆｘｉ／∂Ｓｉ　、∂Ｆｙｉ／∂Ｓｉ　、∂Ｍｉ　／∂Ｓｉ　を演算する。
【００７１】
また電気式制御装置３０は、目標前後力Ｆｘａと実際の前後力Ｆｘ　との差、目標前輪横力Ｆｙｆａ　と実際の前輪横力Ｆｙｆとの差、目標後輪横力Ｆｙｒａ　と実際の後輪横力Ｆｙｒとの差、目標モーメントＭａ　と実際のモーメントＭとの差及び微係数∂Ｆｘｉ／∂Ｓｉ　、∂Ｆｙｉ／∂Ｓｉ　、∂Ｍｉ　／∂Ｓｉ　に基づき収束演算により前後力の修正量δＦｘ　、前輪横力の修正量δＦｙｆ、後輪横力の修正量δＦｙｒ、モーメントの修正量δＭを演算し、前後力、前輪横力、後輪横力、モーメントの修正量を達成するための各輪のスリップ率の修正量δＳｉ　を演算し、前回演算された目標スリップ率をスリップ率修正量δＳｉ　にて修正することにより今回の目標スリップ率Ｓｉ　を演算し、必要に応じて目標スリップ率Ｓｉ　を補正し、各輪の実際のスリップ率が目標スリップ率になるよう各輪の制動力を制御する。
【００７２】
次に図２乃至図７に示されたフローチャートを参照して図示の実施形態に於ける車輌の運動制御について説明する。尚図２に示されたゼネラルフローチャートによる制御は図には示されていないイグニッションスイッチの閉成により開始され、所定の時間毎に繰返し実行される。
【００７３】
まずステップ５０に於いては各輪のスリップ率Ｓｉ　がそれぞれ初期値として０に設定され、ステップ１００に於いては車輪速度Ｖｗｉ等を示す信号の読み込みが行われ、ステップ１５０に於いては図３に示されたルーチンに従って後輪のスリップ角βｒ　が演算される。
【００７４】
ステップ２００に於いては図４に示されたルーチンに従って前回のステップ５００に於いて演算された目標スリップ率での車輌の前後力Ｆｘ　、前輪横力Ｆｙｆ、後輪横力Ｆｙｒ、モーメントＭ、即ち現在の前後力、前輪横力、後輪横力、モーメントが演算され、ステップ２５０に於いては図５に示されたルーチンに従って車輌の目標前後力Ｆｘａ、目標前輪横力Ｆｙｆａ　、目標後輪横力Ｆｙｒａ　、目標モーメントＭａ　が演算される。
【００７５】
ステップ３００に於いては上記式９及び１０に従って微小なスリップ率の変化に対する各輪の前後力の変化及び横力の変化が演算されると共に、上記式２１〜２８及び式３２に従って車輌の前後力の微係数∂Ｆｘｉ／∂Ｓｉ　、横力の微係数∂Ｆｙｉ／∂Ｓｉ　、モーメントの微係数∂Ｍｉ　／∂Ｓｉ　が演算される。
【００７６】
ステップ３５０に於いては上記式３３に従ってそれぞれ前後力、前輪横力、後輪横力、モーメントの目標値Ｆｘａ、Ｆｙｆａ、Ｆｙｒａ　、Ｍａ　と実際の値Ｆｘ　、Ｆｙｆ、Ｆｙｒ、Ｍとの偏差として車輌の前後力の修正量δＦｘ　、前輪横力の修正量δＦｙｆ、後輪横力の修正量δＦｙｒ、モーメントの修正量δＭが演算される。
【００７７】
ステップ４００に於いては図６に示されたルーチンに従って各輪のスリップ率の修正量δＳｉ　に対する重みＷｄｓ（式３９）が演算されると共に、現在の車輌の前後力、前輪横力、後輪横力、モーメントと目標前後力、目標前輪横力、目標後輪横力、目標モーメントとの差Δを０にするスリップ率修正量のうち、上記式３４にて表される評価関数Ｌを最小化する各輪のスリップ率の修正量δＳｉ　が上記式３５に従って演算される。
【００７８】
ステップ４５０に於いては前回の目標スリップ率Ｓｉ　とステップ４００に於いて演算されたスリップ率の修正量δＳｉ　との和（Ｓｉ　＋δＳｉ　）として修正後の目標スリップ率Ｓｉ　が演算される。
【００７９】
ステップ５００に於いては図７に示されたルーチンに従って目標スリップ率Ｓｉ　が必要に応じて補正され、ステップ５５０に於いては各輪の車輪速度Ｖｗｉに基づき各輪の実際のスリップ率が演算されると共に、各輪の実際のスリップ率が目標スリップ率Ｓｉ　になるよう各輪の制動力が車輪速度フィードバックにて制御され、しかる後ステップ１５０へ戻る。
【００８０】
図３に示された後輪のスリップ角βｒ　演算ルーチンのステップ１５５に於いては、横加速度Ｇｙ　と車速Ｖ及びヨーレートγの積Ｖγとの偏差Ｇｙ　−Ｖγとして横加速度の偏差、即ち車輌の横すべり加速度Ｖｙｄが演算され、横すべり加速度Ｖｙｄが積分されることにより車体の横すべり速度Ｖｙ　が演算され、車体の前後速度Ｖｘ　（＝車速Ｖ）に対する車体の横すべり速度Ｖｙ　の比Ｖｙ　／Ｖｘ　として車体のスリップ角βが演算される。
【００８１】
ステップ１６０に於いてはＬｒ　を車輌の重心と後輪車軸との間の車輌前後方向の距離として下記の式４２に従って後輪のスリップ角βｒ　が演算される。尚後輪のスリップ角βｒ　は後輪のころがり方向に対し後輪のすべり方向が反時計廻り方向にある場合が正である。
βｒ　＝β−Ｌｒ　γ／Ｖ　　　　　　　　　　　　　　　……（４２）
【００８２】
ステップ１６５に於いては基準値βｒｃを正の定数として後輪のスリップ角βｒ　が基準値βｒｃを越えているか否かの判別が行われ、否定判別が行われたときにはステップ１７５へ進み、肯定判別が行われたときにはステップ１７０に於いて後輪のスリップ角βｒ　が基準値βｒｃに設定される。
【００８３】
同様にステップ１７５に於いては後輪のスリップ角βｒ　が−βｒｃ未満であるか否かの判別が行われ、否定判別が行われたときにはそのままステップ２００へ進み、肯定判別が行われたときにはステップ１８０に於いて後輪のスリップ角βｒ　が−βｒｃに設定され、しかる後ステップ２００へ進む。
【００８４】
図４に示された目標スリップ率での車輌の前後力Ｆｘ　、前輪横力Ｆｙｆ、後輪横力Ｆｙｒ、モーメントＭ演算ルーチンのステップ２０５に於いては、操舵角φに基づき前輪の実舵角φｆ　が演算されると共に、Ｌｆ　を車輌の重心と前輪車軸との間の車輌前後方向の距離として下記の式４３に従って前輪のスリップ角βｆ　が演算される。尚前輪のスリップ角βｆ　は前輪のころがり方向に対し前輪のすべり方向が反時計廻り方向にある場合が正である。
βｆ　＝−φｆ　＋β＋Ｌｆ　γ／Ｖ　　　　　　　　　　　……（４３）
【００８５】
ステップ２１０に於いてはｇを重力加速度として車体の前後加速度Ｇｘ　及び横加速度Ｇｙ　に基づき下記の式４４に従ってタイヤに対する路面の摩擦係数μが推定演算される。
μ＝（Ｇｘ^２＋Ｇｙ^２）^１／２／ｇ　　　　　　　　　　　　……（４４）
【００８６】
ステップ２１５に於いては車体の前後加速度Ｇｘ　及び横加速度Ｇｙ　に基づき当技術分野に於いて周知の要領にて各輪の荷重移動量ΔＷｉ　が演算されると共に、各輪の支持荷重Ｗｉ　が各輪の静荷重Ｗｓｉと荷重移動量ΔＷｉ　との和（Ｗｓｉ＋ΔＷｉ　）として演算される。
【００８７】
ステップ２２０に於いては各輪のグリップ状態の判定値ξｉ　が上記式８に従って演算され、ステップ２２５に於いては判定値ξｉ　が正又は０であるか否かの判別、即ち車輪がグリップ状態にあるか否かの判別が行われ、肯定判別が行われたときにはそれぞれ上記式１及び２に従って各輪の前後力Ｆｔｘｉ　及び横力Ｆｔｙｉ　が演算され、否定判別が行われたときにはステップ２３５に於いてそれぞれ上記式３及び４に従って各輪の前後力Ｆｔｘｉ　及び横力Ｆｔｙｉ　が演算される。尚ステップ２２５〜２３５は各輪毎に実行される。
【００８８】
ステップ２４０に於いては車輌の前後力Ｆｘ　、前輪横力Ｆｙｆ、後輪横力Ｆｙｒ、モーメントＭに対する各輪の成分が上記式１１〜２０に従って演算され、ステップ２４５に於いては上記式２９に従って車輌の実際の前後力Ｆｘ　、実際の前輪横力Ｆｙｆ、実際の後輪横力Ｆｙｒ、実際のモーメントＭが演算され、しかる後ステップ２５０へ進む。
【００８９】
図５に示された車輌の目標前後力Ｆｘａ、目標前輪横力Ｆｙｆａ　、目標後輪横力Ｆｙｒａ　、目標モーメントＭａ　演算ルーチンのステップ２５５に於いては、Ｋｈ　をスタビリティファクタとしＨをホイールベースとして下記の式４５に従って目標ヨーレートγｃ　が演算されると共に、Ｔを時定数としｓをラプラス演算子として下記の式４６に従って基準ヨーレートγｔ　が演算される。尚目標ヨーレートγｃ　は動的なヨーレートを考慮すべく車輌の横加速度Ｇｙ　を加味して演算されてもよい。
γｃ　＝Ｖφ／（１＋Ｋｈ　Ｖ^２）Ｈ　　　　　　　　　　　……（４５）
γｔ　＝γｃ　／（１＋Ｔｓ）　　　　　　　　　　　　　……（４６）
【００９０】
ステップ２６０に於いては下記の式４７に従ってドリフトアウト量ＤＶが演算される。尚ドリフトアウト量ＤＶはＨをホイールベースとして下記の式４８に従って演算されてもよい。
ＤＶ＝（γｔ　−γ）　　　　　　　　　　　　　　　　……（４７）
ＤＶ＝Ｈ（γｔ　−γ）／Ｖ　　　　　　　　　　　　　……（４８）
【００９１】
ステップ２６５に於いてはヨーレートγの符号に基づき車輌の旋回方向が判定され、ドリフトアウト状態量ＤＳが車輌が左旋回のときにはＤＶとして、車輌が右旋回のときには−ＤＶとして演算され、演算結果が負の値のときにはドリフトアウト状態量は０とされる。
【００９２】
ステップ２７０に於いてはドリフトアウト状態量ＤＳに基き図８に示されたグラフに対応するマップより係数Ｋｇ　が演算され、ステップ２７５に於いてはＫｍ１及びＫｍ２をそれぞれ正の定数とし、βｄ　を車輌のスリップ角βの微分値とし、βｔ　及びβｔｄをそれぞれ車輌の目標スリップ角及び目標スリップ角の微分値として下記の式４９に従って挙動制御の目標モーメントＭｔ　が演算される。尚目標スリップ角βｔ　及び目標スリップ角の微分値βｔｄは何れも０であってもよい。
Ｍｔ　＝Ｋｍ１（β−βｔ　）＋Ｋｍ２（βｄ　−βｔｄ）　　　　……（４９）
【００９３】
ステップ２８０に於いては下記の式５０に従って係数Ｋｇ　と車輌の質量Ｍａｓｓ　と重力加速度ｇとの積として挙動制御の目標前後力Ｆｘｔが演算される。
Ｆｘｔ＝−Ｋｇ　Ｍａｓｓ　ｇ　　　　　　　　　　　　　　　……（５０）
【００９４】
ステップ２８５に於いては各輪のスリップ率Ｓｉ　が０であるときの車輌の前後力Ｆｘｓｏ　、前輪横力Ｆｙｆｓｏ、後輪横力Ｆｙｒｓｏ、モーメントＭｓｏが上記式３０に従って演算され、ステップ２９０に於いては車輌の目標前後力Ｆｘａ、目標前輪横力Ｆｙｆａ　、目標後輪横力Ｆｙｒａ、モーメントＭａ　が上記式３１に従って演算され、しかる後ステップ３００へ進む。
【００９５】
図６に示された各輪のスリップ率の修正量演算ルーチンのステップ４０２に於いては、右前輪及び左前輪のスリップ率の修正量δＳｆｒ及びδＳｆｌに対する重みＷｄｓｆｒ及びＷｄｓｆｌがそれぞれ１に設定され、ステップ４０４に於いては前輪のスリップ角βｆ　が正であるか否かの判別が行われ、否定判別が行われたときにはステップ４１０へ進み、肯定判別が行われたときにはステップ４０６へ進む。
【００９６】
ステップ４０６に於いては目標モーメントＭａ　が負であるか否かの判別が行われ、否定判別が行われたときにはステップ４１４へ進み、肯定判別が行われたときにはステップ４０８に於いて右前輪のスリップ率の修正量δＳｆｒに対する重みＷｄｓｆｒが５に設定される。同様にステップ４１０に於いては目標モーメントＭａ　が正であるか否かの判別が行われ、否定判別が行われたときにはステップ４１４へ進み、肯定判別が行われたときにはステップ４１２に於いて左前輪のスリップ率の修正量δＳｆｌに対する重みＷｄｓｆｌが５に設定される。
【００９７】
またステップ４１４に於いては右後輪及び左後輪のスリップ率の修正量δＳｒｒ及びδＳｒｌに対する重みＷｄｓｒｒ及びＷｄｓｒｌがそれぞれ１に設定され、ステップ４１６に於いては後輪のスリップ角βｒ　が正であるか否かの判別が行われ、否定判別が行われたときにはステップ４２２へ進み、肯定判別が行われたときにはステップ４１８へ進む。
【００９８】
ステップ４１８に於いては目標モーメントＭａ　が正であるか否かの判別が行われ、否定判別が行われたときにはステップ４２６へ進み、肯定判別が行われたときにはステップ４２０に於いて右後輪のスリップ率の修正量δＳｒｒに対する重みＷｄｓｒｒが５に設定される。同様にステップ４２２に於いては目標モーメントＭａ　が負であるか否かの判別が行われ、否定判別が行われたときにはステップ４２６へ進み、肯定判別が行われたときにはステップ４２４に於いて左後輪のスリップ率の修正量δＳｒｌに対する重みＷｄｓｒｌが５に設定される。
【００９９】
ステップ４２６に於いてはステップ４０２〜４２４に於いて設定された各輪のスリップ率の修正量δＳに対する重みＷｄｓｆｒ〜Ｗｄｓｒｌを用いて、上記式３４にて表される評価関数Ｌを最小化する各輪のスリップ率の修正量δＳｉ　が上記式３５に従って演算される。
【０１００】
図７に示された目標スリップ率補正演算ルーチンのステップ５０５に於いては、目標モーメントＭａ　が負であり且つ後輪のスリップ角βｒ　が正であり且つ車輌のヨーレートγが正であるか否かの判別が行われ、否定判別が行われたときにはステップ５１０へ進み、肯定判別が行われたときにはステップ５１５に於いて後輪の目標スリップ率Ｓｒｒ及びＳｒｌがそれぞれ０に設定され、しかる後ステップ５５０へ進む。
【０１０１】
ステップ５１０に於いては目標モーメントＭａ　が正であり且つ後輪のスリップ角βｒ　が負であり且つ車輌のヨーレートγが負であるか否かの判別が行われ、肯定判別が行われたときにはステップ５１５へ進み、否定判別が行われたときにはそのままステップ５５０へ進む。
【０１０２】
かくして図示の実施形態によれば、ステップ１５０に於いて後輪のスリップ角βｒ　が演算され、ステップ２００に於いて現在の車輌の前後力Ｆｘ　、前輪横力Ｆｙｆ、後輪横力Ｆｙｒ、モーメントＭが演算され、ステップ２５０に於いて各輪のスリップ率Ｓｉ　が０であるときの車輌の前後力Ｆｘｓｏ　、前輪横力Ｆｙｆｓｏ、後輪横力Ｆｙｒｓｏ　、モーメントＭｓｏと車輌の挙動を安定化させるための目標前後力Ｆｘｔ及び目標モーメントＭｔ　との和として車輌の目標前後力Ｆｘａ、目標前輪横力Ｆｙｆａ、目標後輪横力Ｆｙｒａ、モーメントＭａ　が演算され、ステップ３００に於いて各輪のスリップ率の微小な変化ｄＳｉ　に対する車輌の前後力、前輪横力、後輪横力、モーメントの変化ｄＦｘ　、ｄＦｙｆ、ｄＦｙｒ、ｄＭを示す微係数∂Ｆｘｉ／∂Ｓｉ　、∂Ｆｙｉ／∂Ｓｉ　、∂Ｍｉ　／∂Ｓｉ　が演算される。
【０１０３】
またステップ３５０に於いて目標前後力Ｆｘａと実際の前後力Ｆｘ　との差、目標前輪横力Ｆｙｆａと実際の前輪横力Ｆｙｆとの差、目標後輪横力Ｆｙｒａと実際の後輪横力Ｆｙｒとの差、目標モーメントＭａ　と実際のモーメントＭとの差及び微係数∂Ｆｘｉ／∂Ｓｉ　、∂Ｆｙｉ／∂Ｓｉ　、∂Ｍｉ　／∂Ｓｉ　に基づき収束演算により前後力の修正量δＦｘ　、前輪横力の修正量δＦｙｆ、後輪横力の修正量δＦｙｒ、モーメントの修正量δＭが演算され、ステップ４００に於いて前後力、前輪横力、後輪横力、モーメントの修正量を達成するための各輪のスリップ率の修正量δＳｉ　が演算され、ステップ４５０に於いて前回演算された目標スリップ率がスリップ率修正量δＳｉ　にて修正されることにより今回の目標スリップ率Ｓｉ　が演算され、ステップ５００に於いて必要に応じて目標スリップ率Ｓｉ　が補正され、ステップ５５０に於いて各輪の実際のスリップ率が目標スリップ率になるよう制御される。
【０１０４】
従って図示の実施形態によれば、車輌の前後力Ｆｘ　が目標前後力Ｆｘａになり、前輪横力Ｆｙｆが目標前輪横力Ｆｙｆａになり、後輪横力Ｆｙｒが目標後輪横力Ｆｙｒａになり、モーメントＭが目標モーメントＭａ　になるよう各輪のスリップ率が制御されるので、車輌の運動、特に旋回時の挙動を確実に安定化させることができるだけでなく、ステップ３５０に於ける収束演算に於いて上記式４１にて表わされる各力の重みのうち、後輪横力に対する重みＷＦｙｒは前輪横力に対する重みＷＦｙｆよりも大きい値に設定されるので、収束演算に際し前輪横力の減少に比して後輪横力の減少を抑制し、これにより後輪の横力が前輪横力に比して大きく低下すること及びこれに起因して車輌に旋回方向のヨーモーメントが過剰に作用して車輌が前輪の周りに自転することを確実に防止することができる。
【０１０５】
特に図示の実施形態によれば、各輪のスリップ率修正量δＳｉ　は現在の車輌の前後力、前輪横力、後輪横力、モーメントと目標前後力、目標前輪横力、目標後輪横力、目標モーメントとの差Δを０にするスリップ率修正量のうち、上記式３４にて表される評価関数Ｌを最小化する各輪のスリップ率の修正量として上記式３５に従って演算されるので、車輌や車輌の走行環境毎に各輪のスリップ率と車輌の運動を安定化させるための前後力、前輪横力、後輪横力、モーメントとの間を対応関係を示す多数のマップを設定する必要がなく、これにより運動制御装置を簡便に構成することができ、また目標前後力、目標前輪横力、目標後輪横力、目標モーメントを実現する各輪のスリップ率Ｓｉ　が解析により演算される場合に比して迅速に目標スリップ率を演算することができ、これにより車輌の運動を応答遅れなく適切に制御することができる。
【０１０６】
また車輌の運動を安定化させるための目標状態量が目標前後力及び目標モーメントのみである場合には、横力の低下が考慮されないため、車輌のコーストレース性が悪化し易いが、図示の実施形態によれば、目標前後力及び目標モーメントに加えて目標前輪横力及び目標後輪横力が考慮されるので、横力の低下に起因する車輌のコーストレース性の悪化を確実に回避することができる。
【０１０７】
また図９に示されている如く、後輪１０ＲＲ及び１０ＲＬのスリップ角βｒ　の大きさが大きいときには、後輪に小さい前後力を発生させる場合にもこれらの目標スリップ率Ｓｒｒ及びＳｒｌが高い値になり、かかる状況に於いて旋回方向が逆転されると、後輪の車輪速度が小さ過ぎて車輌がスピンし易くなる。
【０１０８】
図示の実施形態によれば、ステップ１６５〜１８０に於いて後輪のスリップ角βｒ　の大きさが大きいときには後輪のスリップ角βｒ　が基準値βｒｃ又は−βｒｃに設定された状態にてステップ２００以降が実行されるので、後輪の実際のスリップ角の大きさが大きいときにも後輪の目標スリップ率Ｓｒｒ及びＳｒｌが高い値に演算されることがなく、従って車輌の旋回方向が逆転される場合にも後輪の車輪速度が小さ過ぎることに起因して車輌がスピン状態になることを確実に回避することができる。
【０１０９】
また右前輪について図１０に示されている如く、右前輪のスリップ角βｆ　が正である場合には、ブラッシュタイヤモデルによれば、右前輪のスリップ率Ｓｆｒと右前輪が車輌に与える前後力Ｆｘｆｒ　及び横力Ｆｙｆｒ　との関係は図１１（Ａ）に示されている通りであり、右前輪のスリップ率Ｓｆｒと右前輪が車輌に与えるモーメントＭｆｒとの関係は図１１（Ｂ）に示されている通りである。
【０１１０】
図１１（Ａ）に示されている如く、スリップ率Ｓｆｒが増大するにつれて前後力Ｆｘｆｒ　は単純に漸次減少し、横力Ｆｙｆｒ　は単純に漸次増大するのに対し、モーメントＭｆｒは図１１（Ｂ）に示されている如くスリップ率Ｓｆｒが特定の値であるときにピーク値を有し、ピーク値の点Ａの両側に於けるモーメントＭｆｒの傾きは互いに逆である。
【０１１１】
従って右前輪のスリップ率Ｓｆｒの修正量δＳｆｒに対する重みＷｄｓｆｒが一定のまま目標モーメントＭａ　が負の大きい値であるとして収束演算が行われると、右前輪のスリップ率Ｓｆｒの修正量δＳｆｒが比較的大きい絶対値にて符号が逆転し、そのため右前輪の目標スリップ率Ｓｆｒが点Ａの近傍に於いて振動的に変化し、車輌の運動を適正に制御することが困難である。
【０１１２】
尚このことは左後輪についても同様であり、また上記問題は左前輪及び右後輪については車輪のスリップ角が正であり且つ目標モーメントＭａ　が正である場合に生じる。
【０１１３】
図示の実施形態によれば、ステップ４０４〜４１０及びステップ４１６〜４２２に於いて各輪の目標スリップ率が振動的に変化する虞れがあるか否かが判定され、その虞れがあるときにはそれぞれステップ４０８、４１２、４２０、４２４に於いて対応する車輪の目標スリップ率の修正量δＳｉ　に対する重みＷｄｓｆｒ〜Ｗｄｓｒｌが１より５に増大されるので、収束演算により各輪の目標スリップ率Ｓｉ　が振動的に変化することを防止して車輌の運動を適正に制御することができる。
【０１１４】
また図示の実施形態によれば、各輪の目標スリップ率が振動的に変化する虞れがあるか否かの判定は車輪のスリップ角の符号だけでなく目標モーメントＭａの符号も考慮して行なわれるので、車輪のスリップ角の符号のみに基づく場合に比して各輪の目標スリップ率が振動的に変化する虞れがあるか否かを正確に判定することができる。従って各輪の目標スリップ率が振動的に変化する虞れがない状況に於いて車輪の目標スリップ率の修正量δＳｉ　に対する重みＷｄｓｆｒ〜Ｗｄｓｒｌが不必要に増大され、そのため車輪の目標スリップ率の修正量の収束が遅くなることに起因して車輌の運動制御の応答性が悪化することを確実に防止することができる。
【０１１５】
更に図１２に示されている如く、目標モーメントＭａ　と後輪のスリップ角βｒ　の符号が逆の場合には、後輪の横力Ｆｙｒｒ　、Ｆｙｒｌ　を低下させて目標モーメントを達成するよう後輪の目標スリップ率Ｓｒｒ、Ｓｒｌが高い値に演算され、かかる状況にて後輪のスリップ角の符号が逆転すると、後輪の横力の方向も逆転する。しかし後輪の目標スリップ率が高く後輪の横力が小さいので、目標モーメントが達成されず、そのため後輪の目標スリップ率が急激に低くなり、かかる後輪の目標スリップ率の急激な変化が旋回方向の逆転時に発生すると、後輪の制動力の低減が間に合わず、車輌のスピンが助長されてしまう。
【０１１６】
これに対し図示の実施形態によれば、ステップ５０５又は５１０に於いて目標モーメント及び後輪のスリップ角の符号が逆の関係であることが判別されるとステップ５１５に於いて後輪の目標スリップ率Ｓｒｒ及びＳｒｌがそれぞれ０に低減されるので、後輪のスリップ角の符号が逆転しても目標スリップ率は急激に変化せず、後輪の制動力の低減の遅れに起因して車輌のスピンが助長されることを確実に回避することができる。
【０１１７】
以上に於いては本発明を特定の実施形態について詳細に説明したが、本発明は上述の実施形態に限定されるものではなく、本発明の範囲内にて他の種々の実施形態が可能であることは当業者にとって明らかであろう。
【０１１８】
例えば上述の実施形態に於いては、ステップ２５０に於いて車輌の目標前後力Ｆｘａ、目標前輪横力Ｆｙｆａ　、目標後輪横力Ｆｙｒａ、目標モーメントＭａ　を演算するための式３１に於いて挙動制御の目標横力が０に設定されるようになっているが、挙動制御の目標前輪横力Ｆｙｆｔ　及び目標後輪横力Ｆｙｒｔ　がＫｙｆ１　、Ｋｙｒ１　及びＫｙｆ２　、Ｋｙｒ２をそれぞれ正の定数として目標モーメントＭｔ　と同様下記の式５３及び５４２に従って演算され、車輌の目標前後力Ｆｘａ、目標前輪横力Ｆｙｆａ、目標後輪横力Ｆｙｒａ、目標モーメントＭａ　が下記の式５５に従って演算されてもよい。
【０１１９】
Ｆｙｆｔ＝Ｋｙｆ１（β−βｔ　）＋Ｋｙｆ２（βｄ　−βｔｄ）　　　　……（５３）
Ｆｙｒｔ＝Ｋｙｒ１（β−βｔ　）＋Ｋｙｒ２（βｄ　−βｔｄ）　　　　……（５４）
【数２５】

【０１２０】
また上述の実施形態に於いては、ステップ５５０に於いて各輪の制動力が制御されることにより各輪の実際のスリップ率が目標スリップ率Ｓｉ　に制御されるようになっているが、図には示されていないエンジンの出力が制御されることにより、各輪の制動力若しくは駆動力が制御されてもよい。
【０１２１】
また上述の実施形態に於いては、挙動制御の目標前後力Ｆｘｔ及び目標モーメントＭｔ　はステップ２５５〜ステップ２８０に従って演算されるようになっているが、挙動制御の目標前後力Ｆｘｔ及び目標モーメントＭｔ　又は挙動制御の目標前後力Ｆｘｔ、目標前輪横力Ｆｙｆｔ　、目標後輪横力Ｆｙｒｔ、目標モーメントＭｙ　は当技術分野に於いて公知の任意の態様にて演算されてよい。
【０１２２】
更に上述の実施形態に於いては、各輪の目標スリップ率が振動的に変化する虞れがあるか否かの判定は車輪のスリップ角の符号及び目標モーメントＭａの符号の両者に基づき行なわれるようになっているが、各輪の目標スリップ率が振動的に変化する虞れがあるか否かの判定は車輪のスリップ角の符号のみに基づ行なわれてもよい。
【図面の簡単な説明】
【図１】本発明による車輌の運動制御装置の一つの好ましい実施形態を示す概略構成図である。
【図２】図示の実施形態に於ける運動制御ルーチンを示すゼネラルフローチャートである。
【図３】図２に示されたフローチャートのステップ１５０に於ける後輪スリップ角βｒ　演算ルーチンを示すフローチャートである。
【図４】図２に示されたフローチャートのステップ２００に於ける実際の前後力Ｆｘ　、前輪横力Ｆｙｆ、後輪横力Ｆｙｒ、モーメントＭ演算ルーチンを示すフローチャートである。
【図５】図２に示されたフローチャートのステップ２５０に於ける目標前後力Ｆｘａ、目標前輪横力Ｆｙｆａ　、目標後輪横力Ｆｙｒａ、目標モーメントＭａ　演算ルーチンを示すフローチャートである。
【図６】図２に示されたフローチャートのステップ４００に於ける各輪のスリップ率の修正量δＳｉ　演算ルーチンを示すフローチャートである。
【図７】図２に示されたフローチャートのステップ５００に於ける目標スリップ率Ｓｉ　演算ルーチンを示すフローチャートである。
【図８】ドリフトアウト状態量ＤＶと係数Ｋｇ　との間の関係を示すグラフである。
【図９】左右後輪のスリップ角βｒ　の大きさが大きい状況を示す説明図である。
【図１０】車輌が右旋回状態にあるときの右前輪のスリップ角βｆｒを示す説明図である。
【図１１】右前輪のスリップ率Ｓｆｒと右前輪が車輌に与える前後力Ｆｘｆｒ　及び横力Ｆｙｆｒ　との関係（Ａ）及び右前輪のスリップ角βｆｒが正であるときの右前輪のスリップ率Ｓｆｒと右前輪が車輌の重心の周りに発生するモーメントＭｆｒとの関係（Ｂ）を示すグラフである。
【図１２】目標モーメントＭａ　及び後輪のスリップ角βｒ　の符号が逆の関係にある状況を示す説明図である。
【図１３】タイヤの発生力Ｆｔｉがタイヤの横方向に対しなす角度θｉ　等を示す説明図である。
【図１４】スリップ率が０であるときのタイヤのスリップ角βｉ　に対する横力Ｆｔｙｉ　の関係を示すグラフである。
【図１５】スリップ角βｉ　が０であるときのタイヤのスリップ率Ｓｉ　に対する前後力Ｆｔｘｉ　の関係を示すグラフである。
【符号の説明】
１０ＦＲ〜１０ＲＬ…車輪
２０…制動装置
２８…マスタシリンダ
３０…電気式制御装置
３２ＦＲ〜３２ＲＬ…車輪速度センサ
３４……操舵角センサ
３６…ヨーレートセンサ
３８…前後加速度センサ
４０…横加速度センサ
４２…車速センサ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a motion control device for a vehicle, and more particularly, to a motion control device for improving the stability of a vehicle during traveling.
[0002]
[Prior art]
As one of motion control devices for vehicles such as automobiles, for example, as described in Japanese Patent Application Laid-Open No. H11-348753 filed by the present applicant, the derivative of the change in the vehicle state quantity with respect to the small change in the wheel control quantity. From the tire model, means for calculating the target value of the vehicle state quantity for stabilizing the vehicle motion based on the vehicle model or the driver's request, and convergence using the derivative and the target value. Means for calculating a target control amount of each wheel for realizing the target value by calculation; and means for controlling the wheel operating device to realize the target control amount, wherein the vehicle state quantity is the longitudinal force and the lateral force of the vehicle. A vehicle motion control device characterized by a yaw moment is conventionally known.
[0003]
According to such a motion control device, the differential coefficient of the change in the vehicle state quantity with respect to the slight change in the wheel control amount is calculated from the tire model, and the target value of the vehicle state quantity for stabilizing the motion of the vehicle is set in the vehicle model or the driving mode. A target control amount of each wheel that achieves the target value is calculated by a convergence calculation using the derivative and the target value, and the wheel operating device is controlled to realize the target control amount. Therefore, the control amount of each wheel can be controlled to the target control amount with high accuracy without requiring a large number of maps, whereby the motion of the vehicle can be reliably and appropriately stabilized.
[0004]
[Problems to be solved by the invention]
However, in the motion control device according to the above-mentioned proposal, the target values of the longitudinal force, the lateral force, and the yaw moment may be calculated to unrealizable values. Since a trade-off is made between the target values of the yaw moment, the target control amount of each wheel may be a value that reduces the lateral force of the rear wheel and gives the vehicle a turning inward yaw moment. Therefore, there is a problem that the behavior of the vehicle may not always be completely optimized.
[0005]
The present invention relates to a method for achieving a target value of each wheel that achieves a target value by a convergence calculation using a differential coefficient of a change in a vehicle state quantity with respect to a small change in a wheel control amount and a target value of a vehicle state quantity for stabilizing the movement of the vehicle. The present invention has been made in view of the above-described problems in the conventional motion control device configured to calculate the control amount, and a main problem of the present invention is that the front wheel lateral force is not the target value of the vehicle lateral force but the target value. By calculating the target value of the rear wheel lateral force and the target value of the rear wheel lateral force, the vehicle motion control can be more preferably achieved.
[0006]
[Means for Solving the Problems]
SUMMARY OF THE INVENTION According to the present invention, the above-mentioned main object is to provide a structure according to claim 1, that is, a means for calculating a differential coefficient of a change in a vehicle state amount with respect to a small change in a wheel control amount from a tire model, and stabilizing the movement of the vehicle. Means for calculating a target value of a vehicle state quantity for the vehicle based on a vehicle model or a driver's request, and a target control amount of each wheel for realizing the target value by a convergence calculation using the differential coefficient and the target value. In a vehicle motion control device having means for calculating and a means for controlling a wheel operating device so as to achieve the target control amount, the vehicle state amount is a longitudinal force of the vehicle, a front wheel lateral force, and a rear wheel lateral force. , The yaw moment of the vehicle.
[0007]
According to the present invention, in order to effectively achieve the above-described main object, the means for calculating the target control amount of each wheel is smaller than the reduction in the lateral force of the front wheels. Then, the convergence calculation is performed so that the reduction of the lateral force of the rear wheels is suppressed (the configuration of claim 2).
[0008]
Function and effect of the present invention
According to the configuration of claim 1, as in the case of the motion control device according to the above proposal, the derivative of the change in the vehicle state quantity with respect to the slight change in the wheel control quantity is calculated from the tire model, and the motion of the vehicle is calculated. The target value of the vehicle state quantity for stabilization is calculated based on the vehicle model or the driver's request, and the target control amount of each wheel that achieves the target value by the convergence calculation using the differential coefficient and the target value is calculated. The wheel operation device is controlled so as to realize the target control amount. In this case, the target values of the vehicle front-rear force, front wheel lateral force, rear wheel lateral force, and yaw moment of the vehicle are set as target values of the vehicle state amount. Since the values are calculated, the front wheel lateral force and the rear wheel lateral force are compared with the case where the target values of the longitudinal force of the vehicle, the lateral force of the vehicle, and the yaw moment of the vehicle are calculated as the target values of the vehicle state quantity. Calculate the desired value of Therefore, it is possible to reduce the possibility that the target control amount of each wheel becomes a value that reduces the lateral force of the rear wheel and imparts a turning inward yaw moment to the vehicle, thereby more preferably controlling the motion of the vehicle. Can be achieved.
[0009]
According to the configuration of the second aspect, the means for calculating the target control amount of each wheel performs the convergence calculation so that the decrease in the lateral force of the rear wheel is suppressed as compared with the decrease in the lateral force of the front wheel. Is reliably prevented from increasing as compared with the reduction in the lateral force of the front wheels, whereby the possibility that a turning inward yaw moment is applied to the vehicle can be reliably reduced.
[0010]
[Basic principle of the present invention]
The requirements required for a tire model are as follows.
(A) The longitudinal force Fxi and the lateral force Fyi have saturation characteristics with respect to the slip ratio Si.
(B) The partial differential value of the slip ratio Si of the longitudinal force Fxi and the lateral force Fyi has load dependency.
(C) The longitudinal force Fxi and the lateral force Fyi are differentiable with respect to the slip ratio Si.
[0011]
The basic principle of the present invention will be described using a brush tire model as an example of a tire model that satisfies the above requirements in consideration of a reduction in lateral force during braking, a load shift, a tire slip angle, and a road surface friction coefficient.
[0012]
First, the longitudinal force Ftxi and the lateral force Ftyi (i = fr, fl, rr, rl) generated by the tire of each wheel are obtained based on the brush tire model, and the tire longitudinal force change and lateral force due to a small change in the slip ratio. Seek change.
[0013]
As shown in FIG. 13, the generated force Fti of the tire 100 of each wheel, that is, the angle formed by the resultant force of the longitudinal force Ftxi and the lateral force Ftyi with respect to the longitudinal direction of the tire is θi, and the slip angle of the tire is βi, The slip ratio of the tire is Si (positive during braking, -∞ <Si <1.0), the friction coefficient of the road is μ, the ground contact load of the tire is Wi, and Ks and Kb are coefficients (positive constants). Then, the longitudinal force Ftxi and the lateral force Ftyi when the tire is not in the locked state (when ξi ≧ 0) are expressed by the following equations 1 and 2, respectively, and when the tire is in the locked state (when ξi <0). The force Ftxi and the lateral force Ftyi in (case) are expressed by the following equations 3 and 4, respectively.
[0014]
(Equation 1)

[0015]
The coefficient Kb is the slope at the origin of the graph of the lateral force Ftyi with respect to the slip angle βi of the tire when the slip ratio Si is 0, as shown in FIG. 14, and the coefficient Ks is shown in FIG. As described above, this is the slope at the origin of the graph of the longitudinal force Ftxi versus the slip ratio Si of the tire when the slip angle βi is 0. Further, cos θ, sin θ, λ, and ξ are represented by the following equations 5 to 8, respectively.
[0016]
(Equation 2)

[0017]
By partially differentiating the above formulas 1 to 4 with the slip ratio Si 2, a change in the longitudinal force and a change in the lateral force (tire coordinate system) with respect to a small change in the slip ratio are calculated (the following formulas 9 and 10).
[0018]
[Equation 3]

[0019]
Next, the front-rear force and the lateral force (tire coordinate system) of each tire of the right front wheel (fr), the left front wheel (fl), the right rear wheel (rr), and the left rear wheel (rl) are calculated according to the following equations 11 to 18. The coordinate system is converted to calculate the longitudinal force Fxi and the lateral force Fyi acting on the center of gravity of the vehicle, and the moment Mi is calculated. In the following equations, φf and φr are the steering angles of the front wheels and the rear wheels, respectively, Tr is the tread width of the vehicle, and Lf and Lr are the distances from the center of gravity of the vehicle to the front wheel axle and the rear wheel axle, respectively. It is a distance, and T (φf) and T (φr) are values represented by the following equations 19 and 20, respectively.
[0020]
(Equation 4)

[0021]
(Equation 5)

[0022]
(Equation 6)

[0023]
(Equation 7)

[0024]
(Equation 8)

[0025]
Similarly, the partial differential values of the front-rear force and the lateral force (tires) of the right front wheel (fr), the left front wheel (fl), the right rear wheel (rr), and the left rear wheel (rl) are calculated according to the following equations 21 to 28. The coordinate system is converted into a vehicle coordinate system to calculate the partial differential value (derivative coefficient) of the longitudinal force and the lateral force acting on the vehicle, and to calculate the partial differential value (differential coefficient) of the moment.
[0026]
(Equation 9)

[0027]
(Equation 10)

[0028]
[Equation 11]

[0029]
(Equation 12)

[0030]
Next, the longitudinal force Fx, the front wheel lateral force Fyf, the rear wheel lateral force Fyr, and the moment M, which are generated when the slip ratio of each wheel is the target slip ratio Si, are respectively determined by the longitudinal force Fxi and the front wheel lateral force Fyfr by each wheel. And the sum of Fyfl, rear wheel lateral force Fyrr and Fyrl, and moment Mi are calculated according to the following equation 29.
[0031]
(Equation 13)

[0032]
Next, based on the following concepts (A) and (B), the target longitudinal force Fxa, the target front wheel lateral force Fyfa, the target rear wheel lateral force Fyra, and the target moment Ma are calculated according to the following equations 30 and 31. The right side of the following equation 30 represents the longitudinal force, the lateral force, and the moment generated by each wheel when the slip ratio is 0.
[0033]
(A) The target longitudinal force Fxt and the target moment Mt for stabilizing the behavior of the vehicle by controlling the vehicle motion are the longitudinal force Fxso and the moment generated when the motion control is not performed (when the slip ratio Si is 0). It is regarded as an additional amount to Mso.
[0034]
(B) The front wheel lateral force Fyfso and the rear wheel lateral force Fyrso when the motion control is not performed are set to the target front wheel lateral force Fyfa and the target rear wheel lateral force Fyra, respectively, so that the decrease in the lateral force during the motion control is reduced as much as possible. .
[0035]
[Equation 14]

[0036]
The change dFx of the longitudinal force acting on the vehicle body due to the small change dSi of the slip ratio of the controlled four wheels dFx, the change dFyf of the front wheel lateral force, the change dFyr of the rear wheel lateral force, and the change dM of the moment are expressed by the following equation (32). You. In the following Expression 32, dSfr, dSfl, dSrr, and dSrl are small changes in the slip ratio of the right front wheel, the left front wheel, the right rear wheel, and the left rear wheel, respectively, and J is a Jacobian matrix.
[0037]
[Equation 15]

[0038]
Next, the slip ratio Si for realizing the target front-rear force Fxa, the target front wheel lateral force Fyfa, the target rear wheel lateral force Fyra, and the target moment Ma is calculated. However, since it is difficult to analytically solve this slip ratio, it is obtained by the following convergence calculation.
[0039]
Assuming that the difference between the current front-rear force, front wheel lateral force, rear wheel lateral force, moment and target front-rear force, target front wheel lateral force, target rear wheel lateral force, and target moment is Δ, Δ is expressed by the following equation 33. Then, among the slip ratio correction amounts that set Δ to 0, a slip ratio correction amount δS that minimizes the evaluation function L expressed by the following Expression 34 using T as a transport is obtained.
[0040]
(Equation 16)

L = δS ^T WdsδS + (S + δS) ^T Ws (S + δS) + E ^T Wf E ... (34)
[0041]
The slip rate correction amount δS for minimizing the evaluation function L in Expression 34 is as shown in Expression 35 below, where ∂L / と し て δS = 0 in Expression 34 above.
δS = (Wds + Ws + J ^T Wf J) ^-1 (-Ws S + J ^T Wf Δ) (35)
[0042]
Where Fx, Fyf, Fyr, and M are the longitudinal force, the front wheel lateral force, the rear wheel lateral force, and the moment (Equation 29) generated at the current slip ratio of the controlled wheel, respectively, and Fxa, Fyfa, Fyra, and Ma. Are the target front-rear force, the target front wheel lateral force, the target rear wheel lateral force, and the target moment (Equation 31), respectively, and S and δS are the slip rate of each wheel (Equation 36 below) and the slip rate correction amount (Equation 31 below), respectively. Equation 37), E is the difference between the longitudinal and lateral force, the front wheel lateral force, the rear wheel lateral force, and the amount of correction of the moment due to Δ and δS (Equation 38 below), and Wds is the weight for the slip rate correction amount δS ( In the following Expression 39, Ws is a weight for the slip ratio S (Expression 40 below), Wf is a weight for each force (Expression 41 below), and each weight is 0 or a positive value. Also, among the weights Wf in the following Expression 41, the weight WFyr for the rear wheel lateral force is a larger value than the weight WFyf for the front wheel lateral force.
[0043]
[Equation 17]

[0044]
(Equation 18)

[0045]
[Equation 19]

[0046]
(Equation 20)

[0047]
(Equation 21)

[0048]
(Equation 22)

[0049]
Accordingly, by correcting the previous target slip rate Si with the slip rate correction amount δSi, the target slip rate of each wheel achieving the target front-rear force Fxa, the target front wheel lateral force Fyfa, the target rear wheel lateral force Fyra, and the target moment Ma is obtained. Si can be calculated.
[0050]
The evaluation function L of the above equation 34 is a matrix expression of the following equation 51, where 1 to 4 mean the right front wheel, the left front wheel, the right rear wheel, and the left rear wheel, respectively. L is the same as the matrix expression of the basic expression of the evaluation function (Equation 52 below) in the above-mentioned Japanese Patent Application Laid-Open No. 11-348753.
[0051]
(Equation 23)

[0052]
[Equation 24]

[0053]
Preferred embodiments of the means for solving the problems
According to one preferred aspect of the present invention, in the configuration of the first aspect, the means for calculating the target control amount of each wheel includes “the deviation between the actual vehicle state amount and the target value” and “the differential coefficient”. And the product of the target control variable and the target control variable, the target of each wheel is minimized so that the value of the evaluation function consisting of the sum of squares of the target control variable and the sum of the target control variable and the change is minimized. The control amount is calculated by a convergence calculation, and the target control amount calculated last time is corrected by the change amount of the target control amount (preferred mode 1).
[0054]
According to another preferred embodiment of the present invention, in the configuration of the above-described preferred embodiment 1, the weight of "the deviation between the actual rear wheel lateral force and its target value" is set to "actual" when calculating the sum of squares. It is configured to be set to be larger than the weight of "the deviation between the front wheel lateral force and its target value" (preferred mode 2).
[0055]
According to another preferred embodiment of the present invention, in the configuration of the above-mentioned claim 1, the tire model takes into account a reduction in lateral force during braking, a load shift, a tire slip angle, and a road surface friction coefficient. (Preferred embodiment 3).
[0056]
According to another preferred aspect of the present invention, in the configuration of the first aspect, the target control amount of each wheel is configured to be a target slip ratio (preferred aspect 4).
[0057]
According to another preferred embodiment of the present invention, in the configuration of the first aspect, the target control amount of each wheel is configured to be a target slip ratio (preferred embodiment 5).
[0058]
According to another preferred embodiment of the present invention, in the configuration of the first aspect, the wheel control amount is configured to be a wheel slip ratio (preferred embodiment 6).
[0059]
According to another preferred embodiment of the present invention, in the configuration of the first aspect, the wheel operating device is configured to be a device that controls braking / driving force of the wheel (preferred embodiment 7).
[0060]
According to another preferred aspect of the present invention, in the configuration of claim 2, the front wheel lateral force and the rear wheel lateral force when the slip ratio of all the wheels is zero are estimated, and the front wheel lateral force is estimated. The force and the rear wheel lateral force are set to the target front wheel lateral force and the target rear wheel lateral force, respectively (preferred mode 8).
[0061]
According to another preferred embodiment of the present invention, in the configuration of the preferred embodiment 3, the tire model is configured to be a brush tire model (preferred embodiment 9).
[0062]
According to another preferred aspect of the present invention, in the configuration of the first aspect, the target slip ratio of the rear wheel is configured to be reduced to zero (preferred aspect 10).
[0063]
According to another preferred embodiment of the present invention, in the configuration of the first aspect, the weight setting means determines a change amount of the target slip ratio of the wheel based on the sign of the wheel slip angle and the sign of the yaw moment. The weight is variably set (preferred mode 11).
[0064]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0065]
FIG. 1 is a schematic configuration diagram showing one preferred embodiment of a vehicle motion control device according to the present invention.
[0066]
In FIG. 1, 10FL and 10FR denote left and right front wheels of the vehicle 12, respectively, and 10RL and 10RR denote left and right rear wheels that are driving wheels of the vehicle, respectively. The left and right front wheels 10FL and 10FR, which are both driven wheels and steering wheels, are driven by a rack-and-pinion type power steering device 16 driven in response to the steering of the steering wheel 14 by the driver via tie rods 18L and 18R. Steered.
[0067]
The braking force of each wheel is controlled by controlling the braking pressure of the wheel cylinders 24FR, 24FL, 24RR, 24RL by the hydraulic circuit 22 of the braking device 20. Although not shown in the drawing, the hydraulic circuit 22 includes a reservoir, an oil pump, various valve devices, and the like, and the braking pressure of each wheel cylinder is normally driven in accordance with the driver's depression operation of the brake pedal 26. It is controlled by a master cylinder 28 and, if necessary, by an electric controller 30 as will be described in detail later.
[0068]
The wheels 10FR to 10RL are provided with wheel speed sensors 32FR, 32FL, 32RR, 32RL for detecting wheel speeds Vwi (i = fr, fl, rr, rl), respectively. A steering column to which the steering wheel 14 is connected is used for steering. A steering angle sensor 34 for detecting the angle φ is provided. The vehicle 12 is provided with a yaw rate sensor 36 for detecting the yaw rate γ of the vehicle, a longitudinal acceleration sensor 38 for detecting the longitudinal acceleration Gx, a lateral acceleration sensor 40 for detecting the lateral acceleration Gy, and a vehicle speed sensor 42 for detecting the vehicle speed V. ing. The steering angle sensor 34, the yaw rate sensor 36, and the lateral acceleration sensor 40 detect the steering angle, the yaw rate, and the lateral acceleration, respectively, with the left turning direction of the vehicle being positive.
[0069]
As shown, a signal indicating the wheel speed Vwi detected by the wheel speed sensors 32FR to 32RL, a signal indicating the steering angle φ detected by the steering angle sensor 34, a signal indicating the yaw rate γ detected by the yaw rate sensor 36, A signal indicating the longitudinal acceleration Gx detected by the acceleration sensor 38, a signal indicating the lateral acceleration Gy detected by the lateral acceleration sensor 40, and a signal indicating the vehicle speed V detected by the vehicle speed sensor 42 are input to the electric control device 30. You. Although not shown in detail in the drawing, the electric control device 30 has, for example, a general configuration in which a CPU, a ROM, a RAM, and an input / output port device are connected to each other by a bidirectional common bus. Includes a microcomputer.
[0070]
The electric control device 30, according to flowcharts shown in FIGS. 2 to 7 as described later, controls the longitudinal force Fxso, the front wheel lateral force Fyso, and the rear wheel lateral force Fyrso when the slip ratio Si of each wheel is 0. The target longitudinal force Fxa, the target front wheel lateral force Fyfa, the target rear wheel lateral force Fyfa, and the target moment Ma are calculated as the sum of the moment Mso, the target longitudinal force Fxt for stabilizing the behavior of the vehicle, and the target moment Mt. Then, differential coefficients ∂Fxi / ∂Si, ∂Fyi / indicating the changes dFx, dFyf, dFyr, and dM of the vehicle longitudinal force, front wheel lateral force, rear wheel lateral force, and moment with respect to the minute change dSi of the slip ratio of each wheel. Calculate ∂Si, ∂Mi / ∂Si.
[0071]
In addition, the electric control device 30 controls the difference between the target longitudinal force Fxa and the actual longitudinal force Fx, the difference between the target front wheel lateral force Fyfa and the actual front wheel lateral force Fyf, the target rear wheel lateral force Fyra and the actual rear wheel lateral force. The correction amount δFx of the longitudinal force by the convergence calculation based on the difference between the force Fyr, the difference between the target moment Ma and the actual moment M, and the derivatives ∂Fxi / ∂Si, ∂Fyi / ∂Si, and ∂Mi / ∂Si, Calculate the lateral force correction amount δFyf, the rear wheel lateral force correction amount δFyr, and the moment correction amount δM, and slip each wheel to achieve the longitudinal force, front wheel lateral force, rear wheel lateral force, and moment correction amounts. The target slip rate Si is calculated by correcting the target slip rate Si calculated by correcting the target slip rate calculated last time by the slip rate correction amount δSi, and correcting the target slip rate Si 2 as necessary. The actual of each wheel The braking force of each wheel is controlled so that the slip ratio becomes the target slip ratio.
[0072]
Next, the motion control of the vehicle in the illustrated embodiment will be described with reference to the flowcharts shown in FIGS. The control according to the general flowchart shown in FIG. 2 is started by closing an ignition switch (not shown), and is repeatedly executed at predetermined time intervals.
[0073]
First, in step 50, the slip ratio Si of each wheel is set to 0 as an initial value, and in step 100, a signal indicating the wheel speed Vwi or the like is read, and in step 150, the signal shown in FIG. The rear wheel slip angle βr is calculated according to the routine shown in FIG.
[0074]
In step 200, the longitudinal force Fx, the front wheel lateral force Fyf, the rear wheel lateral force Fyr, and the moment M at the target slip ratio calculated at step 500 in the previous step 500 in accordance with the routine shown in FIG. The current front-rear force, front-wheel lateral force, rear-wheel lateral force, and moment are calculated, and in step 250, the target longitudinal force Fxa, target front-wheel lateral force Fyfa, and target rear-wheel lateral force according to the routine shown in FIG. The force Fira and the desired moment Ma are calculated.
[0075]
In step 300, the change in the longitudinal force and the change in the lateral force of each wheel with respect to the minute change in the slip rate are calculated according to the above equations 9 and 10, and the longitudinal force of the vehicle is calculated according to the above equations 21 to 28 and 32. , The differential coefficient 横 Fyi / ∂Si of the lateral force and the differential coefficient ∂Mi / ∂Si of the moment are calculated.
[0076]
In step 350, the deviation between the target values Fxa, Fyfa, Fira, Ma of the front-rear force, the front wheel lateral force, the rear wheel lateral force, and the moment and the actual values Fx, Fyf, Fyr, M according to the above equation 33, respectively. The correction amount δFx of the front-rear force, the correction amount δFyf of the front wheel lateral force, the correction amount δFyr of the rear wheel lateral force, and the correction amount δM of the moment are calculated.
[0077]
In step 400, the weight Wds (Equation 39) for the correction amount δSi of the slip ratio of each wheel is calculated according to the routine shown in FIG. 6, and the present longitudinal force, front wheel lateral force, and rear wheel lateral force of the vehicle are calculated. Among the slip rate correction amounts that make the difference Δ between the force, the moment and the target front-rear force, the target front wheel lateral force, the target rear wheel lateral force, and the target moment zero, the evaluation function L expressed by the above equation 34 is minimized. The correction amount δSi of the slip ratio of each wheel is calculated according to the above equation 35.
[0078]
In step 450, the corrected target slip rate Si is calculated as the sum (Si + δSi) of the previous target slip rate Si and the slip rate correction amount δSi calculated in step 400.
[0079]
In step 500, the target slip ratio Si is corrected as necessary according to the routine shown in FIG. 7, and in step 550, the actual slip ratio of each wheel is calculated based on the wheel speed Vwi of each wheel. At the same time, the braking force of each wheel is controlled by the wheel speed feedback so that the actual slip ratio of each wheel becomes the target slip ratio Si.
[0080]
In step 155 of the routine for calculating the rear wheel slip angle βr shown in FIG. 3, the deviation of the lateral acceleration as the deviation Gy−Vγ between the lateral acceleration Gy and the product Vγ of the vehicle speed V and the yaw rate γ, that is, the vehicle slip The acceleration Vyd is calculated, and the side slip acceleration Vyd is integrated to calculate the side slip speed Vy of the vehicle body. The slip angle of the vehicle body is calculated as a ratio Vy / Vx of the side slip speed Vy of the vehicle body to the longitudinal speed Vx (= vehicle speed V) of the vehicle body. β is calculated.
[0081]
In step 160, the rear wheel slip angle βr is calculated according to the following equation 42, using Lr as the distance between the center of gravity of the vehicle and the rear wheel axle in the vehicle front-rear direction. The slip angle βr of the rear wheel is positive when the slip direction of the rear wheel is counterclockwise with respect to the rolling direction of the rear wheel.
βr = β−Lrγ / V (42)
[0082]
In step 165, it is determined whether or not the rear wheel slip angle βr exceeds the reference value βrc, using the reference value βrc as a positive constant. If a negative determination is made, the process proceeds to step 175, and an affirmative determination is made. Is performed, in step 170, the slip angle βr of the rear wheel is set to the reference value βrc.
[0083]
Similarly, in step 175, it is determined whether or not the rear wheel slip angle βr is smaller than −βrc. If a negative determination is made, the process directly proceeds to step 200, and if a positive determination is made, the process proceeds to step 200. At 180, the slip angle βr of the rear wheel is set to −βrc, and then the routine proceeds to step 200.
[0084]
In step 205 of the vehicle front-rear force Fx, front wheel lateral force Fyf, rear wheel lateral force Fyr, and moment M calculation routine at the target slip ratio shown in FIG. 4, the actual steering angle of the front wheels is calculated based on the steering angle φ. φf is calculated, and the front wheel slip angle βf is calculated according to the following equation 43, where Lf is the distance between the center of gravity of the vehicle and the front wheel axle in the vehicle front-rear direction. The slip angle βf of the front wheel is positive when the slip direction of the front wheel is counterclockwise with respect to the rolling direction of the front wheel.
βf = −φf + β + Lfγ / V (43)
[0085]
In step 210, the friction coefficient μ of the road surface with respect to the tire is estimated and calculated based on the longitudinal acceleration Gx and the lateral acceleration Gy of the vehicle body using g as the gravitational acceleration according to the following equation 44.
μ = (Gx ² + Gy ² ) ^1/2 / G (44)
[0086]
In step 215, based on the longitudinal acceleration Gx and the lateral acceleration Gy of the vehicle body, the load movement amount ΔWi of each wheel is calculated in a manner well known in the art, and the supporting load Wi of each wheel is calculated. Is calculated as the sum of the static load Wsi and the load movement amount ΔWi (Wsi + ΔWi).
[0087]
In step 220, the judgment value ξi of the grip state of each wheel is calculated according to the above equation 8, and in step 225, it is determined whether the judgment value ξi is positive or 0, that is, the wheel is in the grip state. It is determined whether or not there is a vehicle. When an affirmative determination is made, the longitudinal force Ftxi and the lateral force Ftyi of each wheel are calculated according to the above equations 1 and 2, respectively. When a negative determination is made, the routine proceeds to step 235. The longitudinal force Ftxi and the lateral force Ftyi of each wheel are calculated in accordance with Equations 3 and 4, respectively. Steps 225 to 235 are executed for each wheel.
[0088]
In step 240, the components of each wheel with respect to the longitudinal force Fx, the front wheel lateral force Fyf, the rear wheel lateral force Fyr, and the moment M of the vehicle are calculated according to the above equations 11 to 20, and in step 245, according to the above equation 29. The actual longitudinal force Fx of the vehicle, the actual front wheel lateral force Fyf, the actual rear wheel lateral force Fyr, and the actual moment M are calculated.
[0089]
In step 255 of the calculation routine of the target longitudinal force Fxa, the target front wheel lateral force Fyfa, the target rear wheel lateral force Fira, and the target moment Ma shown in FIG. 5, Kh is used as a stability factor and H is used as a wheel base. The target yaw rate γc is calculated according to the following equation 45, and the reference yaw rate γt is calculated according to the following equation 46 using T as a time constant and s as a Laplace operator. The target yaw rate γc may be calculated in consideration of the dynamic yaw rate by taking into account the lateral acceleration Gy of the vehicle.
γc = Vφ / (1 + Kh V ² ) H …… (45)
γt = γc / (1 + Ts) (46)
[0090]
In step 260, the drift-out amount DV is calculated according to the following Expression 47. Note that the drift-out amount DV may be calculated according to the following Expression 48 using H as a wheel base.
DV = (γt−γ) (47)
DV = H (γt−γ) / V (48)
[0091]
In step 265, the turning direction of the vehicle is determined based on the sign of the yaw rate γ, and the drift-out state amount DS is calculated as DV when the vehicle is turning left, and is calculated as -DV when the vehicle is turning right. Is a negative value, the drift-out state amount is set to zero.
[0092]
In step 270, a coefficient Kg is calculated from the map corresponding to the graph shown in FIG. 8 based on the drift-out state quantity DS, and in step 275, Km1 and Km2 are each set to a positive constant, and βd is set to the vehicle. And the target moment Mt of the behavior control is calculated according to the following equation 49 by using βt and βtd as differential values of the target slip angle and the target slip angle of the vehicle, respectively. Note that both the target slip angle βt and the differential value βtd of the target slip angle may be zero.
Mt = Km1 (β−βt) + Km2 (βd−βtd) (49)
[0093]
In step 280, a target longitudinal force Fxt for behavior control is calculated as the product of the coefficient Kg, the mass Mass of the vehicle, and the gravitational acceleration g according to the following equation 50.
Fxt = −Kg Mass g (50)
[0094]
In step 285, the longitudinal force Fxso, the front wheel lateral force Fyfso, the rear wheel lateral force Fyrso, and the moment Mso when the slip ratio Si of each wheel is 0 are calculated according to the above equation 30, and in step 290. , The target front-rear force Fxa, the target front-wheel lateral force Fyfa, the target rear-wheel lateral force Fyra, and the moment Ma are calculated according to the above equation 31, and then the routine proceeds to step 300.
[0095]
In step 402 of the slip ratio correction amount calculation routine of each wheel shown in FIG. 6, the weights Wdsfr and Wdsfl for the slip ratio correction amounts δSfr and δSfl of the right front wheel and the left front wheel are set to 1, respectively. In step 404, it is determined whether or not the front wheel slip angle βf is positive. If a negative determination is made, the process proceeds to step 410, and if an affirmative determination is made, the process proceeds to step 406.
[0096]
In step 406, it is determined whether or not the target moment Ma is negative. If a negative determination is made, the process proceeds to step 414. If an affirmative determination is made, the flow proceeds to step 408 in which the right front wheel slips. The weight Wdsfr for the rate correction amount δSfr is set to 5. Similarly, in step 410, it is determined whether or not the target moment Ma is positive. If a negative determination is made, the process proceeds to step 414. If an affirmative determination is made, the process proceeds to step 412. The weight Wdsfl for the correction amount δSfl of the slip ratio is set to 5.
[0097]
In step 414, the weights Wdsrr and Wdsrl for the correction amounts δSrr and δSrl of the slip ratio of the right rear wheel and the left rear wheel are respectively set to 1. In step 416, the slip angle βr of the rear wheel is positive. A determination is made as to whether or not there is, and when a negative determination is made, the process proceeds to step 422, and when an affirmative determination is made, the process proceeds to step 418.
[0098]
In step 418, it is determined whether or not the target moment Ma is positive. If a negative determination is made, the process proceeds to step 426; The weight Wdsrr for the correction amount δSrr of the slip ratio is set to 5. Similarly, in step 422, it is determined whether or not the target moment Ma is negative. If a negative determination is made, the process proceeds to step 426. If a positive determination is made, the process proceeds to step 424. The weight Wdsrl for the correction amount δSrl of the wheel slip ratio is set to 5.
[0099]
In step 426, each of the weights Wdsfr to Wdsrl with respect to the correction amount δS of the slip ratio of each wheel set in steps 402 to 424 is used to minimize the evaluation function L represented by the above equation 34. The correction amount δSi of the wheel slip ratio is calculated according to the above equation (35).
[0100]
In step 505 of the target slip ratio correction calculation routine shown in FIG. 7, it is determined whether the target moment Ma is negative, the rear wheel slip angle βr is positive, and the vehicle yaw rate γ is positive. When the negative determination is made, the process proceeds to step 510, and when the positive determination is made, the target slip ratios Srr and Srl of the rear wheels are set to 0 in step 515, and thereafter, the process proceeds to step 550. Proceed to.
[0101]
In step 510, it is determined whether the target moment Ma is positive, the rear wheel slip angle βr is negative, and the yaw rate γ of the vehicle is negative. The process proceeds to 515, and if a negative determination is made, the process directly proceeds to step 550.
[0102]
Thus, according to the illustrated embodiment, in step 150, the rear wheel slip angle βr is calculated, and in step 200, the present vehicle longitudinal force Fx, front wheel lateral force Fyf, rear wheel lateral force Fyr, and moment M are calculated. Is calculated in step 250 to stabilize the vehicle's longitudinal force Fxso, front wheel lateral force Fyfso, rear wheel lateral force Fyrso, moment Mso and the vehicle behavior when the slip ratio Si of each wheel is 0. The target longitudinal force Fxa, the target front wheel lateral force Fyfa, the target rear wheel lateral force Fyra, and the moment Ma are calculated as the sum of the target longitudinal force Fxt and the target moment Mt, and in step 300, the small slip ratio of each wheel is calculated. Derivative coefficient 変 化 indicating the change dFx, dFyf, dFyr, dM of the vehicle longitudinal force, front wheel lateral force, rear wheel lateral force, and moment with respect to various changes dSi xi / ∂Si, ∂Fyi / ∂Si, ∂Mi / ∂Si is calculated.
[0103]
In step 350, the difference between the target longitudinal force Fxa and the actual longitudinal force Fx, the difference between the target front wheel lateral force Fyfa and the actual front wheel lateral force Fyf, the target rear wheel lateral force Fyra and the actual rear wheel lateral force Fyr. , The difference between the target moment Ma and the actual moment M and the correction amount δFx of the longitudinal force by the convergence calculation based on the differential coefficients ∂Fxi / ∂Si, ∂Fyi / ∂Si, and ∂Mi / ∂Si, and the front wheel lateral force. The correction amount δFyf, the correction amount δFyr of the rear wheel lateral force, and the correction amount δM of the moment are calculated. In step 400, the front-rear force, the front wheel lateral force, the rear wheel lateral force, and the moment for achieving the correction amount of the moment are calculated. The correction amount δSi of the wheel slip ratio is calculated, and the target slip ratio previously calculated in step 450 is corrected with the slip ratio correction amount δSi to calculate the current target slip ratio Si. In step 500, the target slip ratio Si is corrected as necessary, and in step 550, control is performed so that the actual slip ratio of each wheel becomes the target slip ratio.
[0104]
Therefore, according to the illustrated embodiment, the longitudinal force Fx of the vehicle becomes the target longitudinal force Fxa, the front wheel lateral force Fyf becomes the target front wheel lateral force Fyfa, the rear wheel lateral force Fyr becomes the target rear wheel lateral force Fyra, Since the slip ratio of each wheel is controlled so that the moment M becomes the target moment Ma, not only the movement of the vehicle, particularly the behavior at the time of turning can be reliably stabilized, but also the convergence calculation in step 350 Since the weight WFyr for the rear wheel lateral force is set to a larger value than the weight WFyf for the front wheel lateral force among the weights of the respective forces represented by the above Expression 41, the convergence calculation is performed in comparison with the decrease in the front wheel lateral force. The lateral force of the rear wheel is suppressed to a large extent as compared with the lateral force of the front wheel, and the yaw moment in the turning direction acts on the vehicle excessively due to this. But It is possible to reliably prevent the rotation around the wheel.
[0105]
In particular, according to the illustrated embodiment, the slip ratio correction amount δSi of each wheel is the current vehicle longitudinal force, front wheel lateral force, rear wheel lateral force, moment and target longitudinal force, target front wheel lateral force, target rear wheel lateral force. Since the slip rate correction amount that makes the difference Δ from the target moment zero is 0, the slip amount correction amount of each wheel that minimizes the evaluation function L expressed by the above equation (34) is calculated according to the above equation (35). Numerous maps showing the correspondence between the slip ratio of each wheel and the longitudinal force, front wheel lateral force, rear wheel lateral force, and moment for stabilizing the vehicle motion are set for each vehicle and the driving environment of the vehicle Therefore, the motion control device can be simply configured, and the slip ratio Si of each wheel that achieves the target longitudinal force, the target front wheel lateral force, the target rear wheel lateral force, and the target moment can be calculated by analysis. Target slot faster than It can be calculated the flop rate, thereby it is possible to appropriately control without delay in response to movement of the vehicle.
[0106]
Further, when the target state quantities for stabilizing the motion of the vehicle are only the target longitudinal force and the target moment, the reduction of the lateral force is not taken into account, so that the course tracing property of the vehicle is likely to be deteriorated. According to the embodiment, the target front wheel lateral force and the target rear wheel lateral force are considered in addition to the target longitudinal force and the target moment, so that it is possible to reliably avoid the deterioration of the vehicle's course tracing property due to the decrease in the lateral force. Can be.
[0107]
As shown in FIG. 9, when the magnitude of the slip angle βr of the rear wheels 10RR and 10RL is large, even when a small longitudinal force is generated at the rear wheels, these target slip ratios Srr and Srl become high values. If the turning direction is reversed in such a situation, the wheel speed of the rear wheel is too low, and the vehicle tends to spin.
[0108]
According to the illustrated embodiment, when the magnitude of the rear wheel slip angle βr is large in steps 165 to 180, step 200 and subsequent steps are performed with the rear wheel slip angle βr set to the reference value βrc or −βrc. Is executed, the target slip ratios Srr and Srl of the rear wheels are not calculated to be high even when the actual slip angle of the rear wheels is large, so that the turning direction of the vehicle is reversed. In this case as well, it is possible to reliably prevent the vehicle from spinning due to the wheel speed of the rear wheel being too low.
[0109]
When the slip angle βf of the right front wheel is positive as shown in FIG. 10 for the right front wheel, according to the brush tire model, the slip ratio Sfr of the right front wheel and the longitudinal force Fxfr applied to the vehicle by the right front wheel 11 (A), and the relationship between the slip ratio Sfr of the right front wheel and the moment Mfr applied to the vehicle by the right front wheel is shown in FIG. 11 (B). It is as it is.
[0110]
As shown in FIG. 11A, as the slip ratio Sfr increases, the longitudinal force Fxfr simply decreases gradually and the lateral force Fyfr simply increases gradually, whereas the moment Mfr changes as shown in FIG. 11B. Has a peak value when the slip ratio Sfr is a specific value as shown in FIG. 7, and the slopes of the moments Mfr on both sides of the point A of the peak value are opposite to each other.
[0111]
Therefore, if the convergence calculation is performed on the assumption that the target moment Ma is a large negative value while the weight Wdsfr for the correction amount δSfr of the slip ratio Sfr of the right front wheel is constant, the correction amount δSfr of the slip ratio Sfr of the right front wheel is relatively large. The sign reverses in absolute value, so that the target slip ratio Sfr of the right front wheel vibrates near point A, making it difficult to properly control the movement of the vehicle.
[0112]
The same applies to the rear left wheel, and the above problem occurs when the slip angle of the front left wheel and the rear right wheel is positive and the target moment Ma is positive.
[0113]
According to the illustrated embodiment, it is determined in steps 404 to 410 and steps 416 to 422 whether or not there is a possibility that the target slip ratio of each wheel may change in a vibrational manner. In steps 408, 412, 420, and 424, the weights Wdsfr to Wdsrl for the correction amount δSi of the target slip rate of the corresponding wheel are increased from 1 to 5, so that the target slip rate Si of each wheel is vibrated by the convergence calculation. And the motion of the vehicle can be properly controlled.
[0114]
Further, according to the illustrated embodiment, the determination as to whether or not there is a possibility that the target slip ratio of each wheel may vibrate may be performed in consideration of not only the sign of the wheel slip angle but also the sign of the target moment Ma. Therefore, it is possible to accurately determine whether or not there is a possibility that the target slip ratio of each wheel may change in a vibrational manner as compared with the case based only on the sign of the wheel slip angle. Therefore, the weights Wdsfr to Wdsrl for the correction amount δSi of the target slip rate of the wheel are unnecessarily increased in a situation where there is no possibility that the target slip rate of each wheel changes in an oscillatory manner. It is possible to reliably prevent the response of the motion control of the vehicle from being deteriorated due to the delay of the convergence of the quantity.
[0115]
Further, as shown in FIG. 12, when the sign of the target moment Ma and the sign of the slip angle βr of the rear wheel are opposite, the lateral force Fyrr, Fyrl of the rear wheel is reduced to achieve the target moment by reducing the rear wheel lateral force Fyrr. When the target slip ratios Srr and Srl are calculated to be high values and the sign of the slip angle of the rear wheel reverses in such a situation, the direction of the lateral force of the rear wheel also reverses. However, since the target slip ratio of the rear wheel is high and the lateral force of the rear wheel is small, the target moment is not achieved, so that the target slip ratio of the rear wheel sharply decreases, and such a sudden change in the target slip ratio of the rear wheel is reduced. If this occurs during the reversal of the turning direction, the reduction of the braking force of the rear wheels cannot be made in time, and the spin of the vehicle will be promoted.
[0116]
On the other hand, according to the illustrated embodiment, if it is determined in step 505 or 510 that the sign of the target moment and the sign of the rear wheel slip angle have the opposite relationship, in step 515, the target slip of the rear wheel is determined. Since the rates Srr and Srl are each reduced to 0, the target slip rate does not change abruptly even if the sign of the slip angle of the rear wheel is reversed, and the vehicle is not driven due to a delay in reducing the braking force of the rear wheel. It is possible to reliably prevent the spin from being promoted.
[0117]
In the above, the present invention has been described in detail with respect to a specific embodiment, but the present invention is not limited to the above embodiment, and various other embodiments are possible within the scope of the present invention. Some will be apparent to those skilled in the art.
[0118]
For example, in the above-described embodiment, in step 250, the behavior control is performed by the equation 31 for calculating the target longitudinal force Fxa, the target front wheel lateral force Fyfa, the target rear wheel lateral force Fyra, and the target moment Ma of the vehicle. Is set to 0, but the target front wheel lateral force Fyft and the target rear wheel lateral force Fyrt of the behavior control are set to Kyf1, Kyr1, Kyf2, and Kyr2 as positive constants and the target moment Mt and the target moment Mt, respectively. Similarly, the target longitudinal force Fxa, the target front wheel lateral force Fyfa, the target rear wheel lateral force Fyra, and the target moment Ma may be calculated according to the following Expressions 55 and 542.
[0119]
Fyft = Kyf1 (β−βt) + Kyf2 (βd−βtd) (53)
Fyrt = Kyr1 (β−βt) + Kyr2 (βd−βtd) (54)
(Equation 25)

[0120]
In the above embodiment, the actual slip ratio of each wheel is controlled to the target slip ratio Si by controlling the braking force of each wheel in step 550. The braking force or the driving force of each wheel may be controlled by controlling the output of the engine not shown in FIG.
[0121]
In the above-described embodiment, the target longitudinal force Fxt and the target moment Mt of the behavior control are calculated according to steps 255 to 280. However, the target longitudinal force Fxt and the target moment Mt of the behavior control or The target longitudinal force Fxt, the target front wheel lateral force Fyft, the target rear wheel lateral force Fyrt, and the target moment My of the behavior control may be calculated in any manner known in the art.
[0122]
Further, in the above-described embodiment, the determination as to whether or not there is a possibility that the target slip ratio of each wheel may change in an oscillatory manner is performed based on both the sign of the wheel slip angle and the sign of the target moment Ma. However, the determination as to whether or not there is a possibility that the target slip ratio of each wheel may change in an oscillatory manner may be performed based only on the sign of the slip angle of the wheel.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing one preferred embodiment of a vehicle motion control device according to the present invention.
FIG. 2 is a general flowchart showing a motion control routine in the illustrated embodiment.
FIG. 3 is a flowchart showing a routine for calculating a rear wheel slip angle βr in step 150 of the flowchart shown in FIG. 2;
FIG. 4 is a flowchart showing a routine for calculating actual front-rear force Fx, front wheel lateral force Fyf, rear wheel lateral force Fyr, and moment M in step 200 of the flowchart shown in FIG. 2;
5 is a flowchart showing a routine for calculating a target longitudinal force Fxa, a target front wheel lateral force Fyfa, a target rear wheel lateral force Fyra, and a target moment Ma in step 250 of the flowchart shown in FIG.
6 is a flowchart showing a routine for calculating a correction amount δSi of the slip ratio of each wheel in step 400 of the flowchart shown in FIG. 2;
FIG. 7 is a flowchart showing a target slip ratio Si calculation routine in step 500 of the flowchart shown in FIG. 2;
FIG. 8 is a graph showing a relationship between a drift-out state amount DV and a coefficient Kg.
FIG. 9 is an explanatory diagram showing a situation where the magnitude of the slip angle βr of the left and right rear wheels is large.
FIG. 10 is an explanatory diagram showing the slip angle βfr of the right front wheel when the vehicle is turning right.
FIG. 11 shows the relationship (A) between the slip ratio Sfr of the right front wheel and the longitudinal force Fxfr and the lateral force Fyfr applied to the vehicle by the right front wheel, and the slip ratio Sfr of the right front wheel when the slip angle βfr of the right front wheel is positive. 6 is a graph showing a relationship (B) between a right front wheel and a moment Mfr generated around the center of gravity of the vehicle.
FIG. 12 is an explanatory diagram showing a situation in which the signs of the target moment Ma and the slip angle βr of the rear wheels are in the opposite relationship.
FIG. 13 is an explanatory diagram showing an angle θi and the like formed by a tire generated force Fti with respect to a lateral direction of the tire.
FIG. 14 is a graph showing a relationship between a tire slip angle βi and a lateral force Ftyi when the slip ratio is 0.
FIG. 15 is a graph showing the relationship between the longitudinal force Ftxi and the slip ratio Si of the tire when the slip angle βi is 0.
[Explanation of symbols]
10FR-10RL ... Wheel
20 ... Brake device
28 ... Master cylinder
30 ... Electric control device
32FR-32RL ... wheel speed sensor
34 ... steering angle sensor
36 ... Yaw rate sensor
38 ... longitudinal acceleration sensor
40 ... lateral acceleration sensor
42 ... Vehicle speed sensor

Claims (2)

Means for calculating the differential coefficient of the change in the vehicle state amount with respect to the minute change in the wheel control amount from the tire model, and calculating the target value of the vehicle state amount for stabilizing the movement of the vehicle based on the vehicle model or the driver's request Means for calculating a target control amount of each wheel for achieving the target value by convergence calculation using the derivative and the target value, and means for controlling a wheel operating device so as to realize the target control amount. Wherein the vehicle state quantity is a longitudinal force of the vehicle, a front wheel lateral force, a rear wheel lateral force, and a yaw moment of the vehicle. 2. The vehicle according to claim 1, wherein the means for calculating the target control amount of each wheel performs a convergence calculation so that a decrease in the lateral force of the rear wheels is suppressed as compared with a decrease in the lateral force of the front wheels. Motion control device.

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