JP3702779B2 - Vehicle behavior control device - Google Patents

Description

【００３３】
【数２】

【００３４】
【数３】

【００３５】
【数４】

【００３６】
なお、係数Ｋsは、図９に示すように、スリップ角βiが「０」であることを条件としタイヤのスリップ率Ｓiが「０」であるときの同スリップ率Ｓiに対する傾きである。係数Ｋbは図１０に示されているように、スリップ率Ｓiが「０」であることを条件としタイヤのスリップ角βiが「０」であるときのタイヤのスリップ角βiに対する傾きである。また、ｃｏｓθi、ｓｉｎθi、λi、ξiはそれぞれ下記数５〜数８で表される。
【００３７】
【数５】

【００３８】
【数６】

【００３９】
【数７】

【００４０】
【数８】

【００４１】
上記数１〜数４をスリップ率Ｓiにて偏微分することにより、各車輪の微小なスリップ率変化に対する各車輪の前後力変化及び横力変化が下記数９，１０で表される。
【００４２】
【数９】

【００４３】
【数１０】

【００４４】
次に、下記数１１〜数１８により各輪のタイヤの前後力Ｆtxi及び横力Ｆtyiを車両座標系に変換して車両重心に作用する前後力Ｆxi及び横力Ｆyiを演算し、モーメントＭiを演算する。なお、車両座標系は車両重心を原点とし、車両の前後方向、車両の左右方向及び車両の上下方向をそれぞれＸ方向、Ｙ方向及びＺ方向とする座標系である。また、下記の各式においてφｆ及びφｒはそれぞれ前輪及び後輪の舵角であり、Ｔrは車両のトレッド幅である。また、Ｌf及びＬrはそれぞれ車両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）は数１９，２０で表される。
【００４５】
【数１１】

【００４６】
【数１２】

【００４７】
【数１３】

【００４８】
【数１４】

【００４９】
【数１５】

【００５０】
【数１６】

【００５１】
【数１７】

【００５２】
【数１８】

【００５３】
【数１９】

【００５４】
【数２０】

【００５５】
同様に、下記数２１〜数２８により各タイヤの前後力Ｆtxi及び横力Ｆtyiの偏微分値を車両座標系に変換して車両に作用する前後力及び横力の偏微分値(微係数)を演算し、モーメントの偏微分値（微係数）を演算する。
【００５６】
【数２１】

【００５７】
【数２２】

【００５８】
【数２３】

【００５９】
【数２４】

【００６０】
【数２５】

【００６１】
【数２６】

【００６２】
【数２７】

【００６３】
【数２８】

【００６４】
次に、各輪のスリップ率が目標スリップ率Ｓiであるとしたときに発生する車両の前後力Ｆx、横力Ｆy及びモーメントＭをそれぞれ各輪による前後力Ｆxi、横力Ｆyi、モーメントＭiの和として下記数２９により推定演算する。
【００６５】
【数２９】

【００６６】
次に、下記数３０，３１により車両の目標前後力Ｆxa、目標横力Ｆya及び目標モーメントＭaを演算する。この演算においては、下記に示す（Ａ）及び（Ｂ）の考え方に基づいて演算する。なお、数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、横力及びモーメントを表している。
【００６７】
（Ａ）車両の運動制御により車両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、運動制御をしていないとき（スリップ率Ｓiが「０」であって運動制御が必要ないとき）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みなす。
【００６８】
（Ｂ）運動制御していないときの横力Ｆysoを目標横力Ｆya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。
【００６９】
【数３０】

【００７０】
【数３１】

【００７１】
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、横力の変化ｄＦy、モーメントの変化ｄＭは下記数３２により演算される。なお、数３２において、ｄＳfr、ｄＳfl、ｄＳrr、ｄＳrl、はそれぞれ右前輪２４FR、左前輪２４FL、右後輪２４RR、左後輪２４RL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。
【００７２】
【数３２】

【００７３】
次に目標前後力Ｆxa及び目標モーメントＭaを実現する目標スリップ率Ｓiを演算する。ただし、この目標スリップ率Ｓi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。
【００７４】
現在の前後力Ｆx、横力Ｆy及びモーメントＭと、目標前後力Ｆxa、目標横力Ｆya及び目標モーメントＭaとの各差をΔとすると、Δは下記数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をトランスポーズとして下記数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。
【００７５】
【数３３】

【００７６】
【数３４】

【００７７】
上記数３４の評価関数Ｌを最小化するスリップ率修正量δＳは下記数３５のとおりである。ただしＦx、Ｆy及びＭはそれぞれ現在の被制御輪のスリップ率に応じて発生している前後力、横力及びモーメント（数２９）であり、Ｆxa、Ｆya及びＭaはそれぞれ目標前後力、目標横力及び目標モーメント（数３１）であり、Ｓ及びδＳはそれぞれ数３６及び数３７で表される各輪のスリップ率及びスリップ率修正量であり、Ｅは数３８で表されるΔとδＳによる前後力、横力及びモーメントの修正量との各差である。また、Ｗds、Ｗs及びＷfはそれぞれスリップ率修正量δＳ、スリップ率Ｓi及び各力に対する重みであり、各重みは「０」又は正の値である。
【００７８】
【数３５】

【００７９】
【数３６】

【００８０】
【数３７】

【００８１】
【数３８】

【００８２】
したが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、目標横力Ｆya及び目標モーメント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。
【００８３】
次に下記数３９により基準車輪速度Ｖwを幾何学的に車両の重心位置に変換して、車体基準速度Ｖbを演算する。基準車輪速度Ｖwは、旋回内側前輪の車輪速度であり、例えば、右旋回時には、右前輪２４FRの車輪速度Ｖｗfrが基準車輪速度となる。逆に左旋回時には、左前輪２４FLの車輪速度ＶｗFLが基準車輪速度となる。また、車両の旋回時には、ヨーレートにより生じる左右輪の速度差を補正するため、補正係数としてＶyrを付加して車体基準速度Ｖbを演算する。ただし、補正係数Ｖyrは下記数４０により表される。
【００８４】
【数３９】

【００８５】
【数４０】

【００８６】
次に上記数３９より車体基準速度Ｖbを幾何学的に基準輪以外の各輪位置に変換して、下記数４１より基準輪以外の各輪位置速度Ｖbiを演算する。
【００８７】
【数４１】

【００８８】
次に基準輪以外の各輪の車輪速度の目標車輪速度Ｖriを演算する。目標スリップ率Ｓiに応じて下記数４２により基準輪以外の各輪の目標車輪速度Ｖriを演算することができる。
【００８９】
【数４２】

【００９０】
次に図３乃至図７に示すフローチャートを参照して本実施形態における車両の運動制御について説明する。イグニッションスイッチが閉成されると、マイクロコンピュータ７２は、図３のメインプログラムを所定の短時間ごとに繰り返し実行し始める。
【００９１】
このメインプログラムの実行は、図３のステップＳ１０にて開始され、ステップＳ１２にて各輪の目標スリップ率Ｓiをそれぞれ初期値として「０」に設定し、ステップＳ１４にて各センサ７６〜８８から検出信号を入力する。
【００９２】
次に、ステップＳ１６にて、挙動判定ルーチンを実行して、車両の挙動が異常であるかすなわち車両運動状態がスピン状態又はドリフトアウト状態にあるか否かを判定する。
【００９３】
この挙動判定ルーチンは図４に詳細に示されており、その実行はステップＳ１００にて開始され、ステップＳ１０２にて車体のスリップ角βを演算する。具体的には、前記ステップＳ１４の処理により入力した横加速度Ｇy、車速Ｖ及びヨーレートγを用いた下記数４３の演算により車体の横すべり速度Ｖyを演算し、この演算した車体の横すべり速度Ｖyと前記ステップＳ１４にて入力した車体の前後速度Ｖx(＝車速Ｖ)を用いた下記数４４の演算により車体のスリップ角βを演算する。なお、Ｖyｄは車両の横すべり加速度Ｖyｄである。
【００９４】
【数４３】

【００９５】
【数４４】

【００９６】
次に、ステップＳ１０４にて、前記演算した車体のスリップ角β、前記車速Ｖ及びヨーレートγを用いた下記数４５の演算によって後輪のスリップ角βrを演算する。なお、Ｌrは、車両の重心と後輪車軸との間の車両前後方向の距離であり、車種に応じて予め与えられる定数である。また、後輪の進行方向が後輪の中心面の向きに対して反時計回り方向にある場合に、後輪のスリップ角βrを正とする。
【００９７】
【数４５】

【００９８】
前記後輪のスリップ角βrの演算後、ステップＳ１０６，１０８にて同スリップ角βrの絶対値｜βr｜が基準値βrcの範囲内にあるかを判定することにより、車両の挙動が異常であるか、すなわち車両がスピン状態又はドリフトアウト状態にあるかを判定する。いま、後輪のスリップ角βrの絶対値｜βr｜が予め決めた基準値βrc以内であって、車両の挙動が正常であれば、ステップＳ１０６，Ｓ１０８にて共に「ＮＯ」すなわちスリップ角βrが正の基準値βrcよりも小さくかつ負の基準値βrcよりも大きいと判定し、ステップＳ１１０にてフラグＦＬＧを車両挙動の正常を表す“０”に設定する。
【００９９】
一方、スリップ角βrが正の基準値βrcよりも大きければ、ステップＳ１０６にて「ＹＥＳ」すなわち車両の挙動が異常であると判定し、ステップＳ１１２にて後輪のスリップ角βrを正の基準値βrcに設定するとともに、ステップＳ１１６にてフラグＦＬＧを車両挙動の異常を表す“１”に設定する。また、スリップ角βrが負の基準値−βrcよりも小さければ、ステップＳ１０８にて「ＹＥＳ」すなわち車両の挙動が異常であると判定し、ステップＳ１１４にて後輪のスリップ角βrを負の基準値−βrcに設定するとともに、ステップＳ１１６にてフラグＦＬＧを車両挙動の異常を表す“１”に設定する。前記ステップＳ１１０又はステップＳ１１６の処理後、ステップＳ１１８にてこの挙動判定ルーチンの実行を終了する。
【０１００】
ふたたび、図３のメインプログラムの説明に戻ると、前記ステップＳ１６の挙動判定ルーチンの実行後、ステップＳ１８にて、フラグＦＬＧが“１”であるか否か、すなわち車両が挙動異常であるかを判定する。前述のように、車両の挙動が正常であってフラグＦＬＧが“０”に設定されていれば、ステップＳ１８にて「ＮＯ」と判定して、ステップＳ４４にてメインプログラムの実行を終了する。この場合、左右前輪２４ＦＬ，２４ＦＲ及び左右後輪２４ＲＬ，２４ＲＲには、ブレーキペダル３２の踏み込み操作に応じた制動力が付与され、本発明に係る車両の挙動制御は行われない。
【０１０１】
一方、車両の挙動が異常であってフラグＦＬＧが“１”に設定されていれば、ステップＳ１８にて「ＹＥＳ」と判定して、ステップＳ２０にて運動状態量演算ルーチンを実行する。この運動状態量演算ルーチンは図５に詳細に示されており、その実行がステップＳ２００にて開始される。前記開始後、ステップＳ２０２にて、前記ステップＳ１４の処理により入力した前輪操舵角φf、ヨーレートγ及び車速Ｖ、並びに前記ステップＳ１６の挙動判定ルーチンの処理により計算した車体のスリップ角βを用いた下記数４６の演算により、前輪のスリップ角βfを演算する。ただし、Ｌfは車両の重心と前輪車軸との間の車両前後方向の距離を表す予め決めた定数である。なお、前輪の進行方向が前輪の中心面の向きに対して反時計回りにある場合に、前輪のスリップ角βfを正とする。
【０１０２】
【数４６】

【０１０３】
次に、ステップＳ２０４にて、前記ステップＳ１４の処理により入力した車体の前後加速度Ｇx及び横加速度Ｇyを用いた下記数４７の演算により、タイヤに対する路面の摩擦係数μを推定演算する。ただし、ｇは重力加速度である。
【０１０４】
【数４７】

【０１０５】
ステップＳ２０６にて、車体の前後加速度Ｇx及び横加速度Ｇyに定数を乗じて各輪の荷重移動量ΔＷiを演算するとともに、各輪の支持荷重Ｗiを予め決めた各輪の静荷重Ｗsiと荷重移動量ΔＷiとの和（Ｗsi＋ΔＷi）として演算する。例えば車両が制動されていて前後加速度Ｇxが負であるときには前輪の支持荷重Ｗfl，Ｗfrが増加し、車両が旋回しているときには旋回外側車輪の支持荷重が増加する。
【０１０６】
また、ステップＳ２０８においては、上記数７，８の演算の実行により各輪毎のグリップ状態（ロック状態）を表す判定値ξiを計算する。この数７の演算においては、ステップＳ２４にて前回演算された目標スリップ率Ｓi、すなわち現在のスリップ率Ｓiと、上記した係数Ｋs，Ｋb（図９、図１０に示す予め定めた所定値）とを用いるとともに、スリップ角βiとして上記ステップＳ２０２にて数４６の演算により、又はステップＳ１１２，１１４にて設定した後輪のスリップ角βrを用いる。数８の演算においては、前記計算したλiと、前記係数Ｋsと、前回演算された目標スリップ率Ｓi、すなわち現在のスリップ率Ｓiと、前記ステップＳ２０４にて計算した路面の摩擦係数μと、前記ステップＳ２０６にて計算した各輪の支持荷重Ｗiとを用いる。
【０１０７】
前記ステップＳ２０８の処理後、ステップＳ２１０にて前記計算した判定値ξiに基づいて、車輪がグリップ状態にあるか否か、言い換えれば車輪がロック状態にあるか否かの判定を行う。車輪がグリップ状態にあって（ロック状態になくて）、判定値ξiが「０」以上であれば、前記ステップＳ２１０にて「ＹＥＳ」と判定して、ステップＳ２１２に進む。一方、車輪がグリップ状態になくて（ロック状態にあり）、判定値ξiが「０」未満であれば、前記ステップＳ２１０にて「ＮＯ」と判定して、ステップＳ２１４に進む。
【０１０８】
ステップＳ２１２においては、数５，６，１，２の演算により各輪の前後力Ｆtxi及び横力Ｆtyiを計算する。数５，６の演算においては、上記ステップＳ２０８の処理により計算したλi及び上記ステップＳ２０８の演算に使用したＳi，Ｋs，Ｋb，βiを用いてｃｏｓθi，ｓｉｎθiを計算する。前記数１，２の計算においては、前記したξi，Ｓi，ｃｏｓθi，ｓｉｎθi，μ，Ｗi，βi，Ｋs，Ｋbを用いて各輪の前後力Ｆtxi及び横力Ｆtyiを計算する。
【０１０９】
また、ステップＳ２１４にて、上記数５，６，３，４を用いて各輪の前後力Ｆtxi及び横力Ｆtyiを計算する。この数５，６の演算は上述と同様であり、数３，４の演算においては、前記計算したｃｏｓθi，ｓｉｎθi，μ，Ｗiを用いて各輪の前後力Ｆtxi及び横力Ｆtyiを計算する。なお、ステップＳ２１０〜２１４の処理は各輪ごとに行なわれる。
【０１１０】
前記ステップＳ２１２，２１４の処理後、ステップＳ２１６にて、前記ステップＳ１４の処理により入力した前輪操舵角φfと、ステップＳ２１２，２１４にて計算した各輪の前後力Ｆtxi及び横力Ｆtyiとを用いた上記の数１１〜数２０の演算により車両の前後力Ｆxに対する各輪の成分Ｆxfl，Ｆxfr，Ｆxrl，Ｆxrr、横力Ｆyに対する各輪の成分Ｆyfl，Ｆyfr，Ｆyrl，Ｆyrr及びモーメントＭに対する各輪の成分Ｍfl，Ｍfr，Ｍrl，Ｍrrを計算する。
【０１１１】
次に、ステップＳ２１８にて、前記ステップＳ２１６の処理により計算した各輪による車両重心位置の前後力成分Ｆxi、横力成分Ｆyi、モーメント成分Ｍiを用いた上記の数２９により車両の実際の前後力Ｆx、横力Ｆy及びモーメントＭを演算する。そして、ステップＳ２２０のこの運動状態量演算ルーチンの実行を終了する。
【０１１２】
ふたたび、図３のプログラムの説明に戻ると、前記ステップＳ２０の運動状態量演算ルーチンの実行後、ステップＳ２２にて、車両のスピン及びドリフトアウトを抑制するための抑制量を計算する抑制量演算ルーチンを実行する。この抑制量演算ルーチンは図６に詳細に示されており、その実行がステップＳ３００にて開始される。
【０１１３】
前記開始後、ステップＳ３０２にて、前記ステップＳ１４の処理により入力した前輪操舵角φf及び車速Ｖを用いた下記数４８の演算により目標ヨーレートγcを計算する。なお、下記数４９の演算により目標ヨーレートγcを計算してもよい。ただし、下記数４８中のｎは、予め決められた定数値であるステアリングギア比であり、下記数４８及び数４９中のＫh，Ｈは、予め決められた定数値であるスタビリティーファクタ及びホイールベースである。
【０１１４】
【数４８】

【０１１５】
【数４９】

【０１１６】
また、同ステップＳ３０２にて、前記数４８の計算結果を用いた下記数５０の演算により基準ヨーレートγtを計算する。ただし、下記数５０中、Ｔは予め決められた時定数であり、ｓはラプラス演算子である。なお、上記数４９の計算結果を用いた下記数５０の演算により基準ヨーレートγtを計算してもよい。
【０１１７】
【数５０】

【０１１８】
次に、ステップＳ３０４にて、前記計算した基準ヨーレートγtと、前記ステップＳ１４の処理により入力したヨーレートγを用いた下記数５１の演算により両ヨーレートγt，γ間の偏差を表すドリフトアウト量Ｄvを計算する。
【０１１９】
【数５１】

【０１２０】
次に、ステップＳ３０６にて、前記入力したヨーレートγの符号に基づき車両の旋回方向を判定し、車両が左旋回中であればドリフトアウト状態量Ｄsを前記計算したドリフトアウト量Ｄvに設定し、車両が右旋回中であればドリフトアウト状態量Ｄsを前記計算したドリフトアウト量Ｄvを正負反転した値−Ｄvに設定する。
【０１２１】
次に、ステップＳ３０８にて、マイクロコンピュータ７２に内蔵されて図１１に示されたグラフに対応するマップを参照することにより、前記計算したドリフトアウト状態量Ｄsに対応した係数Ｋgを導出しておく。また、ステップ３１０においては、車両のスリップ角速度βd、車両の目標スリップ角βt及び車両の目標スリップ角速度βtdを計算する。この車両のスリップ角速度βdの計算にあっては、前記ステップＳ１６の挙動判定ルーチンにて計算した車両のスリップ角βを微分する。また、車両の目標スリップ角βtを計算するためには、まず前記ステップＳ３０２（数４８）にて計算した目標ヨーレートγc及び前記ステップＳ１４にて入力した車速Ｖを用いた下記数５２の演算により、目標横加速度Ｇycを計算する。なお、これに代えて前記数４９の演算の実行により目標横加速度Ｇycを計算してもよい。そして、図１２に示すような特性を表す予め定められた関数パラメータを用いて、目標横加速度Ｇycに対応した目標スリップ角βtを計算する。ただし、この場合、目標スリップ角βtの上限及び下限は、Ｋ＊μ及び−Ｋ＊μに制限される。なお、このＫは、予め車種ごとに定めた所定値（例えば、０．４程度）である。
【０１２２】
【数５２】

【０１２３】
また、ステップＳ３１２においては、前記計算した車両のスリップ角β及び角速度βdと、前記ステップＳ３１０にて計算した車両の目標スリップ角βt及び目標スリップ角速度βtdとを用いた下記数５３の演算により車両の挙動を安定化させるための目標モーメントＭtを計算する。ただし、Ｋm1，Ｋm2は、適宜定めた正の定数である。なお、前記目標スリップ角βt及び目標スリップ角速度βtdはいずれも「０」であってよい。
【０１２４】
【数５３】

【０１２５】
次に、ステップＳ３１４にて、前記計算した係数Ｋgを用いた下記数５４の演算により車両の挙動を安定化させるための目標前後力Ｆxtを計算する。ただし、Ｍassは車両の質量を表す予め定めた定数であり、ｇは重力加速度である。
【０１２６】
【数５４】

【０１２７】
次に、ステップＳ３１６にて、上記数３０の演算により各輪のスリップ率が０であるときの車両の前後力Ｆxso、横力Ｆyso、モーメントＭsoを計算する。この数３０の計算においては、Ｆxfrso，Ｆxflso，…Ｍrlso等の変数は上記ステップＳ２１６（数１１〜数２０）の処理と同様な各輪の成分の演算にてスリップ率Ｓiを「０」として計算する。
【０１２８】
次に、ステップＳ３１８にて、前記ステップＳ３１６の処理により計算した車両の前後力Ｆxso、横力Ｆyso、モーメントＭsoと、予め決められた目標前後力Ｆxt及び目標モーメントＭtとを用いた上記数３１の演算により車両の目標前後力Ｆxa、横力Ｆya、モーメントＭaを計算する。
【０１２９】
次に、ステップＳ３２０にて、前記ステップＳ２１２，２１４の処理により計算した各輪の前後力Ｆtxi及び横力Ｆtyiを用いた上記数９，１０の演算により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を計算するとともに、前記ステップ２１６の処理により計算した各輪による車両重心位置の前後力成分Ｆxi、横力成分Ｆyi、モーメント成分Ｍiを用いた上記数２１〜２８の演算により車両の前後力の微係数∂Ｆxi／∂Ｓi、横力の微係数∂Ｆyi／∂Ｓi、モーメントの微係数∂Ｍi／∂Ｓiを計算する。
【０１３０】
次に、ステップＳ３２２にて、前記ステップＳ３１８の処理により計算した車両の目標前後力Ｆxa、横力Ｆya、モーメントＭaと、前記ステップＳ２１８の処理により計算した車両の実際の前後力Ｆx、横力Ｆy及びモーメントＭとを用いた上記数３３の演算により車両の前後力の修正量δＦx、横力の修正量δＦy、モーメントの修正量δＭを計算する。そして、ステップＳ３２４のこの抑制量演算ルーチンの実行を終了する。
【０１３１】
ふたたび、図３のプログラムの説明に戻ると、前記ステップＳ２２の抑制量演算ルーチンの実行後、ステップＳ２４にて、目標スリップ率を計算する目標スリップ率演算ルーチンを実行する。この抑制量演算ルーチンは図７に詳細に示されており、その実行がステップＳ４００にて開始される。
【０１３２】
前記開始後、ステップＳ４０２にて、前記ステップＳ３２２の処理により計算した現在の車両の前後力Ｆx、横力Ｆy、モーメントＭと目標前後力Ｆxa、目標横力Ｆya、目標モーメントＭaとの差Δ（車両の前後力の修正量δＦx、横力の修正量δＦy、モーメントの修正量δＭ）を用いた上記数３４，３５の演算により各輪のスリップ率の修正量δＳiを計算する。ただし、上記数３５は上記数３４で表される評価関数Ｌを最小化する各輪のスリップ率の修正量δＳiを計算する。
【０１３３】
次に、ステップＳ４０４にて、前記ステップＳ４０２の処理により計算した各輪のスリップ率の修正量δＳiと、ステップＳ２４にて前回演算された目標スリップ率Ｓi、すなわち現在のスリップ率Ｓiとを用いた下記数５５の演算により各輪の目標スリップ率Ｓiを計算する。そして、ステップＳ４０６のこの抑制量演算ルーチンの実行を終了する。
【０１３４】
【数５５】

【０１３５】
ふたたび、図３のフローチャートの説明に戻ると、前記ステップＳ２４の目標スリップ率の計算後、マイクロコンピュータ７２は、ステップＳ２６にて、デフロックセンサ８８からの信号に基づいて、センターデフ１４がロック状態であるか否か判定する。センターデフ１４がロック状態になければ、ステップＳ２６にて「ＮＯ」と判定し、ステップＳ２８〜Ｓ３２の処理により各輪の目標車輪速度Ｖriを計算する。一方、センターデフ１４がロック状態にあれば、ステップＳ２６にて「ＹＥＳ」と判定し、ステップＳ３４〜Ｓ４０の処理により各輪の目標車輪速度Ｖriを計算する。
【０１３６】
まず、センターデフ１４がロック状態にない場合について説明する。ステップＳ２８においては、各輪２４FL，２４FR，２４RL，２４RRのうちのいずれか一つの車輪を基準輪として定め、前記ステップＳ１４の処理により入力した各車輪速度Ｖwfl，Ｖwfr，Ｖwrl，Ｖwrrのうちで前記基準輪の車輪速度Ｖwiを上記数３９を用いて車両重心位置の速度に変換することにより、車体基準速度Ｖbを計算する。この種の車両の挙動制御においては、車輪速度の検出誤差が最も少ない旋回内側前輪を基準輪として採用することが一般的であるので、具体的には、車両が左旋回中であれば左前輪２４FLが基準輪として決定され、車両が右旋回中であれば右前輪２４FRが基準輪として決定される。したがって、同ステップＳ２８では、前記ステップＳ１４の処理により入力したヨーレートγに基づいて車両の旋回方向が決定され、車両が左旋回中であれば左前輪２４FLが基準輪として決定され、左前輪２４FLの車輪速度Ｖwfl及びヨーレートγにより生じる左右輪の車輪速度差を補正する補正係数Ｖyrを用いた数３９の演算により車体基準速度Ｖbが計算される。また、車両が右旋回中であれば右前輪２４FRが基準輪として決定され、右前輪２４FRの車輪速度Ｖwfrを用いた数３９の演算により車体基準速度Ｖbが計算される。
【０１３７】
次に、ステップＳ３０にて、前記計算した車体基準速度Ｖbと、前記ステップＳ１４の処理により入力した前輪操舵角φf及びヨーレートγと、予め決められた車両のトレッド幅Ｔrを用いた数４１の演算により基準輪以外の３輪の各車輪速度Ｖbiを推定演算する。具体的には、車両の左旋回時にはＶbfr、Ｖbrl、Ｖbrrを計算し、車両の右旋回時ではＶbfl、Ｖbrl、Ｖbrｒを計算する。
【０１３８】
ステップＳ３２にて、前記計算した基準輪以外の３輪の各車輪速度Ｖbi及び前記ステップＳ２４の目標スリップ率演算ルーチンの実行により計算した目標スリップ率Ｓiを用いた上記数４２の演算により基準輪以外の目標車輪速度Ｖriを計算する。具体的には、車両の左旋回時にはＶrfr、Ｖrrl、Ｖrrrを計算し、車両の右旋回時ではＶrfl、Ｖrrl、Ｖrrｒを計算する。
【０１３９】
前記ステップＳ３２の処理後、ステップＳ４２にて、マイクロコンピュータ７２は駆動回路７４を介して制動装置装置３０内の各種開閉弁を制御することにより、基準輪に対する制動を解除するとともに、他の３輪を前記計算した目標車輪速度Ｖriに制御する。そして、ステップＳ４４にてメインプログラムの実行を一旦終了する。
【０１４０】
まず、左右前輪２４FL，２４FR及び左右後輪２４RL，２４RRにそれぞれ対応するブレーキ油圧制御装置３８，４０，４６，４８に設けられた電磁式の制御弁６０FL，６０FR，６０RL，６０RRを、図２で示されている第１の位置から第２の位置へ切換えて、ブレーキペダル３２の踏み込み操作がブレーキ油圧制御導管３６，４４を介してブレーキ油圧制御装置３８，４０，４６，４８に伝達されることを不能とする。この制御により、左右前輪２４FL，２４FR及び左右後輪２４RL，２４RRに対する制動力の付与は、運転者のブレーキペダル３２の踏み込み操作に依存しなくなる。
【０１４１】
また、前記制御と同時に、基準輪に対応したホイールシリンダに制動油圧が付与されないように開閉弁を制御する。具体的には、車両が左旋回中であれば、基準輪としての左前輪２４FLに対応した開閉弁６４FLを閉弁するとともに、開閉弁６６FLを開弁する。車両が右旋回中であれば、基準輪としての右前輪２４FRに対応した開閉弁６４FRを閉弁するとともに、開閉弁６６FRを開弁する。これにより、基準輪に対する制動は解除される。
【０１４２】
一方、他の３輪に関しては、各輪に対応した車輪速度センサにより検出された各検出車輪速度Ｖwiが前記ステップＳ３２の処理により計算した各目標車輪速度Ｖriにそれぞれ一致するように、他の３輪に対応した開閉弁を開閉制御することにより同３輪に対応したホイールシリンダへの制動油圧の供給を制御する。具体的には、車両が左旋回中であれば、右前輪２４FR及び左右後輪２４Rl，２４RRの各検出車輪速度Ｖwfr、Ｖwrl、Ｖwrrと各目標車輪速度Ｖrfr、Ｖrrl、Ｖrrrとの各比較に応じて開閉弁６４FR，６４RL，６４RR及び開閉弁６６FR，６６RL，６６RRを開閉制御する。
【０１４３】
すなわち、各検出車輪速度Ｖwfr、Ｖwrl、Ｖwrrが各目標車輪速度Ｖrfr、Ｖrrl、Ｖrrrよりも大きければ、開閉弁６４FR，６４RL，６４RRをそれぞれ開弁するとともに、開閉弁６６FR，６６RL，６６RRをそれぞれ閉弁して、ホイールシリンダ５８FR，５８RL，５８RRの制動圧を増圧する。逆に、各検出車輪速度Ｖwfr、Ｖwrl、Ｖwrrが各目標車輪速度Ｖrfr、Ｖrrl、Ｖrrrよりも小さければ、開閉弁６４FR，６４RL，６４RRをそれぞれ閉弁するとともに、開閉弁６６FR，６６RL，６６RRをそれぞれ開弁して、ホイールシリンダ５８FR，５８RL，５８RRの制動圧を減圧する。また、各検出車輪速度Ｖwfr、Ｖwrl、Ｖwrrが各目標車輪速度Ｖrfr、Ｖrrl、Ｖrrrに等しければ、開閉弁６４FR，６４RL，６４RRをそれぞれ閉弁するとともに、開閉弁６６FR，６６RL，６６RRをそれぞれ閉弁して、ホイールシリンダ５８FR，５８RL，５８RRの制動圧を保持する。これにより、右前輪２４FR及び左右後輪２４Rl，２４RRの各検出車輪速度Ｖwfr、Ｖwrl、Ｖwrrと各目標車輪速度Ｖrfr、Ｖrrl、Ｖrrrとがそれぞれ一致するように制御される。
【０１４４】
また、車両が右旋回中であれば、左前輪２４FL及び左右後輪２４Rl，２４RRの各検出車輪速度Ｖwfl、Ｖwrl、Ｖwrrと各目標車輪速度Ｖrfl、Ｖrrl、Ｖrrrとの各比較に応じて開閉弁６４FL，６４RL，６４RR及び開閉弁６６FL，６６RL，６６RRを前記左旋回の場合と同様に開閉制御する。これにより、左前輪２４FL及び左右後輪２４Rl，２４RRの各検出車輪速度Ｖwfl、Ｖwrl、Ｖwrrと各目標車輪速度Ｖrfl、Ｖrrl、Ｖrrrとがそれぞれ一致するように制御される。
【０１４５】
その結果、基準輪以外の車輪速度が、車両のスピン、ドリフトアウトなどの車両の挙動を修正するための目標スリップ率Ｓiに応じた目標車輪速度Ｖriとなるように各輪の車輪速度Ｖwiが制御されるので、車両の挙動、特に旋回時の挙動を確実に安定化させることができる。
【０１４６】
次に、センターデフ１４がロック状態である場合について説明する。この状態においても前記ステップＳ２８と同様に各輪２４FL，２４FR，２４RL，２４RRのうちのいずれか一つの車輪を基準輪として定め、ステップＳ３４にて、前記ステップＳ１４の処理により入力した各車輪速度Ｖwfl，Ｖwfr，Ｖwrl，Ｖwrrのうちで前記基準輪の車輪速度Ｖwiを上記数３９を用いて車両重心位置の速度に変換することにより、車体基準速度Ｖbを計算する。
【０１４７】
次に、ステップＳ３６にて、前記ステップＳ３４の処理により計算した車体基準速度Ｖbを用いた下記数５６の演算により、前記ステップＳ３４にて今回計算した車体基準速度Ｖbと、前回計算した車体基準速度Ｖbを補正した値とを比較して小さい方の値を車体基準速度Ｖbとして計算する。ただしＶb_lastは前回計算した車体基準速度であり、αは０．０５〜０．１の定数であり、Δｔは演算のサンプリング周期である。
【０１４８】
【数５６】

【０１４９】
次に、ステップＳ３８にて、前記計算した車体基準速度Ｖbと、前記ステップＳ１４の処理により入力した前輪操舵角φf及びヨーレートγと、予め決められた車両のトレッド幅Ｔrを用いた数４１の演算により基準輪以外の３輪の各車輪速度Ｖbiを推定演算する。具体的には、車両の左旋回時にはＶbfr、Ｖbrl、Ｖbrrを計算し、車両の右旋回時ではＶbfl、Ｖbrl、Ｖbrｒを計算する。
【０１５０】
次に、ステップＳ４０にて、前記計算した基準輪以外の３輪の各車輪速度Ｖbi及び前記ステップＳ２４の目標スリップ率演算ルーチンの実行により計算した目標スリップ率Ｓiを用いた上記数４２の演算により基準輪及び旋回内側後輪以外の目標車輪速度Ｖriを計算する。具体的には、車両の左旋回時にはＶrfr及びＶrrrを計算し、車両の右旋回時ではＶrfl及びＶrrlを計算する。また、センターデフ１４がロック状態とされたときには、下記数５７で表される関係が成立する。すなわち、左右前輪の車輪速度ＶwflとＶwfrとの和及び左右後輪の車輪速度ＶwrlとＶwrrとの和が等しくなる。
【０１５１】
【数５７】

【０１５２】
この関係に基づいて前記ステップＳ１４の処理により入力された車輪速度を用いた下記数５８，５９の演算により旋回内側後輪の目標車輪速度を演算する。具体的には、車両の左旋回時には数５８の演算によりＶrrlを計算し、車両の右旋回時には数５９の演算によりＶrrrを計算する。
【０１５３】
【数５８】

【０１５４】
【数５９】

【０１５５】
前記ステップＳ４０の処理後、ステップＳ４２にて、マイクロコンピュータ７２は駆動回路７４を介して制動装置装置３０内の各種開閉弁を制御することにより、基準輪に対する制動を解除するとともに、他の３輪を前記計算した目標車輪速度Ｖriに制御する。そして、ステップＳ４４にてメインプログラムの実行を一旦終了する。
【０１５６】
このセンターデフ１４がロック状態である場合においても、前記センターデフ１４がロック状態にない場合と同様に、左右前輪２４FL，２４FR及び左右後輪２４RL，２４RRにそれぞれ対応するブレーキ油圧制御装置３８，４０，４６，４８に設けられた電磁式の制御弁６０FL，６０FR，６０RL，６０RRを、第１の位置から第２の位置へ切換える。この制御により、左右前輪２４FL，２４FR及び左右後輪２４RL，２４RRに対する制動力の付与は、運転者のブレーキペダル３２の踏み込み操作に依存しなくなる。
【０１５７】
また、前記センターデフ１４がロック状態にない場合と同様に、基準輪に対応したホイールシリンダに制動油圧が付与されないように開閉弁を制御する。一方、他の３輪に関しても、前記センターデフ１４がロック状態にない場合と同様に、各輪に対応した車輪速度センサにより検出された各検出車輪速度Ｖwiが前記ステップＳ４０の処理により計算した各目標車輪速度Ｖriにそれぞれ一致するように、他の３輪に対応した開閉弁を開閉制御することにより同３輪に対応したホイールシリンダへの制動油圧の供給を制御する。これにより、車両が左旋回中であれば、右前輪２４FR及び左右後輪２４Rl，２４RRの各検出車輪速度Ｖwfr、Ｖwrl、Ｖwrrと各目標車輪速度Ｖrfr、Ｖrrl、Ｖrrrとがそれぞれ一致するように制御される。
【０１５８】
また、車両が右旋回中であれば、左前輪２４FL及び左右後輪２４Rl，２４RRの各検出車輪速度Ｖwfl、Ｖwrl、Ｖwrrと各目標車輪速度Ｖrfl、Ｖrrl、Ｖrrrとがそれぞれ一致するように制御される。
【０１５９】
その結果、この場合も基準輪以外の車輪速度が、車両のスピン、ドリフトアウトなどの車両の挙動を修正するための目標スリップ率Ｓiに応じた目標車輪速度Ｖriとなるよう各輪の車輪速度Ｖwiが制御されるので、車両の挙動、特に旋回時の挙動を確実に安定化させることができる。
【０１６０】
また、上記実施形態によれば、前記ステップＳ４０にて旋回内側の前輪を基準輪とし、旋回外側の前後２輪の目標車輪速度が主に車両の挙動異常を修正するように計算され、旋回内側の後輪の目標車輪速度でセンターデフ１４のロック状態による前後輪の回転数差の規制を吸収するように計算される。
【０１６１】
これにより、センターデフ１４がロック状態にあっても、例えば車両が左旋回中に、旋回外側の前輪である右前輪２４FRの目標車輪速度Ｖrfrを低下させても、旋回内側の後輪である左後輪２４RLの目標車輪速度Ｖrrlでセンターデフ１４のロック状態による前後輪の回転数差の規制を吸収するため、車両の挙動修正に重要な旋回外側の後輪である右後輪２４RRの車輪速度Ｖrrrが低下することがなくなり、この右後輪２４RRによって発生される横力が適切に保たれ、車両の挙動異常が的確に修正される。また、車両が右旋回中に、旋回外側の前輪である左前輪２４FLの目標車輪速度Ｖrflを低下させても、左旋回時と同様に旋回外側の後輪である左後輪２４RLの車輪速度Ｖrrlが低下することがなくなり、この左後輪２４RLによって発生される横力が適切に保たれ、車両の挙動異常が的確に修正される。
【０１６２】
また、上記実施形態によれば、前記ステップＳ３６にて今回計算した車体基準速度Ｖbと、前回計算した車体基準速度Ｖbを補正した値Ｖb_last＋（Ｇx＋α）＊Δｔとのうちの小さい方の値を車体基準速度Ｖbとして導出することにより、基準輪に対応した車輪速度センサによって検出された車輪速度の増加に対して所定の制限を加えて同制限された車輪速度を基準車輪速度とするようにした。
【０１６３】
これにより、例えば車両が左旋回中に、旋回外側の前輪である右前輪２４FRの目標車輪速度Ｖrfrを低下させた結果、スリップを伴って基準輪である左前輪２４FLの回転速度が急激に上昇しても、左前輪２４FLの車輪速度Ｖwflが精度よく検出される。したがって、基準車輪速度Ｖbに基づいて計算される他の３輪の目標車輪速度Ｖbiが適切になり、車両の挙動異常を的確に修正できるようになる。また、車両が右旋回中に、旋回外側の前輪である左前輪２４FLの目標車輪速度Ｖrflを低下させた結果、基準輪である右前輪２４FRの車輪速度Ｖwfrが急激に上昇しても、右前輪２４FRの車輪速度Ｖwfrが精度よく検出され、左旋回時と同様に車両の挙動異常を的確に修正できるようになる。
【０１６４】
なお、上記実施形態においては、基準輪を旋回内側の前輪としたが、同基準輪を旋回内側の後輪として実施してもよい。この場合、旋回外側の前輪及び後輪の目標車輪速度（目標スリップ率）を前記基準輪である旋回内側の後輪の車輪速度（基準車輪速度）と、車両の運動状態量（例えば、前後加速度Ｇx、横加速度Ｇy及びヨーレートγ）とに応じて、車両の挙動を修正するための旋回外側の前輪及び後輪の目標車輪速度（目標スリップ率）を上記実施形態の場合と同様にして計算するとともに、旋回内側の前輪の目標車輪速度を左右後輪の合計車輪速度から旋回外側の前輪の車輪速度を演算することにより計算するとよい。また、場合によっては、旋回外側の前輪又は後輪を基準輪とすることも可能である。
【０１６５】
さらに、上記実施形態で説明するとともに本発明に係る車両の挙動制御装置は、センターデフの形式がメカ式のデフロック装置に限らず、高粘度の粘性流体の剪断を利用してトルクを伝えて、デフの作動が生じたときに作動制限トルクが発生するビスカス式のデフロック装置であってもよい。
【図面の簡単な説明】
【図１】本発明の一実施形態に係り、車両の挙動制御装置の構成を概略的に示す構成図である。
【図２】本発明の一実施形態に係り、制動装置の構成を概略的に示す構成図である。
【図３】図２のマイクロコンピュータにより実行される車両の挙動制御を示すフローチャートである。
【図４】前記車両の挙動制御プログラムにおける挙動判定ルーチンの詳細を示すフローチャートである。
【図５】前記車両の挙動制御プログラムにおける運動状態演算ルーチンの詳細を示すフローチャートである。
【図６】前記車両の挙動制御プログラムにおける抑制量演算ルーチンの詳細を示すフローチャートである。
【図７】前記車両の挙動制御プログラムにおける目標スリップ率演算ルーチンの詳細を示すフローチャートである。
【図８】各輪に生ずる力を説明する説明図である。
【図９】スリップ率Ｓiと前後力Ｆtxiとの関係を示すグラフである。
【図１０】スリップ角βiと横力Ｆtyiとの関係を示すグラフである。
【図１１】ドリフトアウト状態量Ｄsと係数Ｋgの関係を示すグラフである。
【図１２】目標横加速度Ｇycと車体の目標スリップ角βtの関係を示すグラフである。
【符号の説明】
３２…ブレーキペダル、３４…マスタシリンダ、３８，４０，４６，４８…ブレーキ油圧制御装置、５８FL，５８FR，５８RL，５８RR…ホイールシリンダ、７２…マイクロコンピュータ、７６…車速センサ、７８FL，７８FR，７８RL，７８RR…車輪速度センサ、８０…前後加速度センサ、８２…横加速度センサ、８４…ヨーレートセンサ、８６…操舵角センサ、８８…デフロックセンサ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicle behavior control apparatus that corrects vehicle behavior anomalies such as spin and drift-out.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as shown in, for example, Japanese Patent Application Laid-Open No. 8-310366, a vehicle behavior control apparatus that corrects a behavior abnormality when a vehicle turns is known. In this device, when a vehicle behavior abnormality such as spin or drift out occurs, the wheel before turning is determined as a reference wheel, the application of braking force to the determined reference wheel is stopped, and the braking force is applied to the other three wheels. The behavior of the vehicle is modified. In this case, of the four wheels including the left and right front wheels and the left and right rear wheels, the front wheel on the inner side of the turn is used as the reference wheel, and the wheel speed detected by the wheel speed sensor corresponding to the reference wheel is used as the reference wheel speed. The target wheel speed of the other three wheels for correcting the behavior of the vehicle is calculated using the speed and the detected motion state amount of the vehicle, respectively, and the braking force of the other three wheels is controlled to determine the actual wheel speed. The calculated target wheel speed is set.
[0003]
[Problems to be solved by the invention]
However, in the above-described conventional device, there is no consideration for a vehicle equipped with a center differential with a lock mechanism that prohibits a difference in rotational speed between the front and rear wheels in a locked state (hereinafter, this differential is simply referred to as a differential). Absent. If the center differential is in the unlocked state (differential permissible state), a low value is calculated as the target wheel speed of the front wheel outside the turn to correct the behavior of the vehicle, and by applying braking force to the wheel Even if the actual wheel speed of the same wheel is controlled to the low value, a difference in rotational speed between the left and right front wheels and the left and right rear wheels is allowed, so that other wheel speeds are not affected. Therefore, in this case, an appropriate braking force can be applied to each wheel, and the abnormal behavior of the vehicle can be corrected accurately.
[0004]
However, in the state where the center differential is locked (differential prohibited state), the rotational speed difference between the front and rear wheels is prohibited, that is, the total value of the wheel speeds of the left and right front wheels and the total value of the wheel speeds of the left and right rear wheels Therefore, as the wheel speed of the front wheel outside the turn decreases, the wheel speed of the rear wheel decreases or the wheel speed of the front wheel inside the turn increases. Such a decrease in the wheel speed of the rear wheel, particularly a decrease in the wheel speed of the rear wheel outside the turn, which is important for correcting the behavior of the vehicle, reduces the lateral force generated by the rear wheel, thereby accurately correcting the vehicle behavior abnormality. In addition to being unable to correct, the behavior of the vehicle may become more abnormal. Further, the slip ratio of the front wheel on the inner side of the turn increases, and particularly the sudden increase of the wheel speed increases the slip ratio of the wheel. In this case, since the wheel speed is detected by measuring the rotational speed of the wheel, the increase in the slip ratio means a deterioration in the detection accuracy of the wheel speed of the front wheel inside the turn. There is a problem that the target wheel speeds of the other three wheels calculated based on the speed (reference wheel speed) are not appropriate, and the vehicle behavior abnormality cannot be corrected accurately.
[0005]
SUMMARY OF THE INVENTION
The present invention has been made in order to address the above-described problems, and an object of the present invention is to generate an abnormal behavior of a vehicle in a vehicle equipped with a center differential with a lock mechanism even when the center differential is locked. It is an object of the present invention to provide a vehicle behavior control device in which the behavior abnormality is sometimes corrected accurately.
[0006]
  In order to achieve the above object, the constitutional feature of the present invention is that a braking device capable of independently controlling the braking force of the four wheels including the left and right front wheels and the left and right rear wheels, and the rotational speed between the front and rear wheels in the unlocked state. Applies to vehicles equipped with a center differential with a lock mechanism that allows the difference and prohibits the difference in the number of rotations of the front and rear wheels in the locked state, and responds to the detection of vehicle behavior abnormalities when turning the vehicle. In the vehicle behavior control device to be corrected, a wheel speed sensor for detecting each wheel speed of the four wheels,A steering angle sensor for detecting the steering angle of the steering wheel of the vehicle;A movement state quantity detecting means for detecting a movement state quantity of the vehicle;One of the four wheels is used as a reference wheel, and a wheel speed detected by a wheel speed sensor corresponding to the reference wheel is used as a reference wheel speed, and the reference wheel speed and the steering angle detected by the steering angle sensor are used. as well asUsing the detected vehicle state of motion,To correct vehicle behaviorOther 3 wheelsFirst target wheel speed calculating means for calculating respective target wheel speeds ofOne of the four wheels is used as a reference wheel, and a wheel speed detected by a wheel speed sensor corresponding to the reference wheel is used as a reference wheel speed, and the reference wheel speed and the steering angle detected by the steering angle sensor are used. as well asUsing the detected vehicle state of motion,Fixed vehicle behaviorOf the other three wheels, one of the two wheels on the opposite side to the reference wheel and the two wheels on the opposite side of the reference wheelTarget wheel speedRespectivelycalculateAt the same time, the target wheel speed of the remaining one wheel is calculated by subtracting the target wheel speed of the one wheel on the opposite side from the total value of the reference wheel speed and the target wheel speed of the one wheel on the opposite side.Calculated by the first target wheel speed calculating means when the second target wheel speed calculating means and the center differential are unlocked.The other three wheelsTarget wheel speed and saidCorresponding to the other three wheelsUsing the wheel speed detected by the wheel speed sensor,The other three wheelsThe wheel speed of the wheels of the calculatedThe other three wheelsCalculated by the second target wheel speed calculating means when the braking device is controlled to become a target wheel speed and the center differential is in a locked state.The other three wheelsTarget wheel speed and saidCorresponding to the other three wheelsUsing the wheel speed detected by the wheel speed sensor,The other three wheelsThe wheel speed of the wheels of the calculatedThe other three wheelsAnd braking control means for controlling the braking device so as to achieve a target wheel speed.
[0007]
  In this case, the amount of motion state of the vehicle is, for example, longitudinal acceleration, lateral acceleration, and yaw rate of the vehicle.Further, the first target wheel speed calculating means calculates a target slip ratio necessary for correcting the behavior of the vehicle corresponding to the other three wheels based on the detected motion state quantity of the vehicle, Using the reference wheel speed, the steering angle, and the calculated target slip ratio, the target wheel speeds of other three wheels for correcting the behavior of the vehicle are respectively calculated, and the second target wheel speed calculating means includes: Corresponds to one of the other three wheels for correcting the behavior of the vehicle, one of the wheels on the opposite side to the reference wheel and the two wheels on the opposite side of the reference wheel. And calculating a target slip ratio necessary for correcting the behavior of the vehicle based on the detected motion state quantity of the vehicle, and using the reference wheel speed, the steering angle, and the calculated target slip ratio. 1 on the opposite side to the reference wheel And the target wheel speed of any one of the two wheels on the opposite side with respect to the reference wheel is calculated, and the target wheel speed of the remaining one wheel is set to 1 on the opposite side to the reference wheel speed. The value may be calculated by subtracting the target wheel speed of one wheel on the opposite side from the total value with the target wheel speed of the wheel. Further, the first target wheel speed calculation means calculates a reference speed of the vehicle at the center of gravity position of the vehicle based on the reference wheel speed, and calculates the calculated reference speed of the vehicle, the steering angle, and the motion state quantity of the vehicle. The second target wheel speed calculating means calculates the reference speed of the vehicle at the center of gravity position of the vehicle based on the reference speed. One wheel on the opposite side to the reference wheel among the other three wheels for calculating and correcting the behavior of the vehicle using the calculated vehicle reference speed, the steering angle and the vehicle motion state quantity And the target wheel speed of any one of the two wheels on the opposite side with respect to the reference wheel is calculated, and the target wheel speed of the remaining one wheel is set to 1 on the opposite side to the reference wheel speed. Wheel target wheel speed Target wheel speed from the sum of one wheel of said front and rear opposite side may be calculated to a value obtained by subtracting.
[0009]
  More specifically, the reference wheel may be one of the front wheel and the rear wheel inside the turn. Further, the reference wheel is a front wheel on the inside of the turn, and the second target wheel speed calculating means is configured to output the reference wheel speed.The steering angle detected by the steering angle sensorAnd calculating the target wheel speeds of the front and rear two wheels on the outside of the turn for correcting the behavior of the vehicle using the detected motion state quantity of the vehicle, and calculating the target wheel speeds of the rear wheels on the inside of the turn as the reference wheels. It is preferable to calculate a value obtained by subtracting the target wheel speed of the rear wheel outside the turn from the total value of the speed and the target wheel speed of the front wheel outside the turn.
[0010]
  According to the structural features of the invention,The first target wheel speed calculation means sets one of the four wheels as a reference wheel, and sets the wheel speed of the reference wheel as a reference wheel speed. Then, the first target wheel speed calculation means calculates the target wheel speeds of the other three wheels for correcting the behavior of the vehicle, using the reference wheel speed, the steering angle, and the motion state quantity of the vehicle. The second target wheel speed calculation means sets one of the four wheels as a reference wheel, and sets the wheel speed of the reference wheel as a reference wheel speed. Then, the second target wheel speed calculation means uses the reference wheel speed, the steering angle, and the motion state quantity of the vehicle to correct the behavior of the vehicle among the other three wheels on the opposite side to the reference wheel. Calculate the target wheel speed of any one of the two wheels on the opposite side of the front and back with respect to one wheel and the reference wheel, and set the remaining target wheel speed to the wheel on the opposite side to the reference wheel speed. Is calculated by subtracting the target wheel speed of one wheel on the opposite side from the total value with the target wheel speed. As a result, the other three wheels for correcting the behavior of the vehicleEach target wheel speed is calculated by different calculation methods depending on whether the center differential is unlocked (differential allowable state) or locked (differential prohibited state).TheEspecially when the center differential is locked (differential prohibited)The target wheel speeds of the other three wheels for correcting the behavior of the vehicle are calculated by the second target wheel speed calculating means,The calculation is performed so as not to be affected by the prohibition of the difference in the rotational speeds of the front and rear wheels, and the actual wheel speeds of a plurality of wheels are controlled to be the calculated target wheel speeds.
[0011]
  Therefore, even if the center differential is in the locked state and the rotational speed difference between the front and rear wheels is prohibited, it is necessary to correct the behavior of the vehicle.Other 3 wheelsThe target wheel speed of the wheel is accurately set, and the behavior of the vehicle is accurately corrected. For example, as described above, even if the wheel speed outside the turn is reduced, the wheel speed of the rear wheel outside the turn, which is important for correcting the behavior of the vehicle, is not reduced, and the lateral force generated by the rear wheel is reduced. Appropriately maintained and vehicle behavior abnormalities are corrected appropriately.
[0012]
Another structural feature of the present invention is a vehicle behavior control device that determines a target wheel speed of the other three wheels based on a wheel speed of the reference wheel, and is detected by a wheel speed sensor corresponding to the reference wheel. There is provided a reference wheel speed correcting means that applies a predetermined restriction to the increased wheel speed and sets the restricted wheel speed as a reference wheel speed.
[0013]
According to this, as a result of reducing the target wheel speed of the wheel on the opposite side to the reference wheel, for example, as a result of reducing the target wheel speed of the front wheel outside the turn when the front wheel inside the turn is used as the reference wheel, Even if there is a rapid increase in the rotational speed of the reference wheel accompanying the wheel speed, the wheel speed of the reference wheel is detected with high accuracy. Therefore, the target wheel speeds of the other three wheels calculated based on this wheel speed (reference wheel speed) are appropriate, and the vehicle behavior abnormality can be corrected accurately.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a vehicle behavior control device according to the present invention applied to a four-wheel drive vehicle according to the embodiment, and FIG. 2 shows an electrical control device for the braking device 30 shown in FIG. FIG.
[0015]
In FIG. 1, the rotational output of the engine 10 is shifted via a transmission 12, and further, a drive shaft on the front wheel side via a center differential 14 that allows differential between the left and right front wheels 24FL, 24FR and the left and right rear wheels 24RL, 24RR. 16F and the rear wheel side drive shaft 16R. The center differential 14 is provided with a lock mechanism that limits the differential function, and is a mechanism in which the differential lock actuator 18 is driven by the operation of the driver to perform differential lock and differential lock release. The center differential 14 is provided with a differential lock sensor 88 that detects that the center differential 14 is in a locked state (differential prohibited state).
[0016]
The front wheel side drive shaft 16F is connected to the left and right drive shafts 22FL, 22FR via the front differential 20F, and the rear wheel side drive shaft 16R is connected to the left and right drive shafts 22RL, 22RR via the rear differential 20R. Yes. The drive shafts 22FL and 22FR are connected to the left and right front wheels 24FL and 24FR, respectively, and the drive shafts 22RL and 22RR are connected to the left and right rear wheels 24RL and 24RR, respectively, and the rotational output of the engine 10 is transmitted to each wheel.
[0017]
The braking force of each wheel 24FL, 24FR, 24RL, 24RR is controlled by controlling the braking pressure of the wheel cylinders 58FL, 58FR, 58RL, 58RR by the hydraulic circuit A of the braking device 30. As will be described later, the hydraulic circuit A controls the braking pressures of the wheel cylinders 58FL, 58FR, 58RL, and 58RR according to the depression operation of the brake pedal 32 or controlled by the microcomputer 72 of the electric control device 70. .
[0018]
The left and right front wheels 24FL and 24FR, which are steering wheels, are steered according to the rotation of a steering wheel (not shown), and are driven by the output of the engine 10 being transmitted to the drive shafts 22FL and 22FR via the transmission 12. . The left and right rear wheels 24RL and 24RR are driven by the output of the engine 10 being transmitted to the drive shafts 22RL and 22RR via the transmission 12.
[0019]
As shown in FIG. 2, the braking device 30 has a master cylinder 34 that pressure-feeds brake oil from the first and second ports in response to the driver depressing the brake pedal 32, and the first port is a front wheel. The brake hydraulic control conduit 36 for the left and right front wheels is connected to the brake hydraulic control device 38, 40 for the left and right front wheels, and the second port is connected to the left and right rear wheels by the brake hydraulic control conduit 44 for the rear wheels having a proportional valve 42 in the middle. The brake hydraulic pressure control devices 46 and 48 are connected.
[0020]
Further, the braking device 30 has an oil pump 54 that pumps up the brake oil stored in the reservoir 50 and supplies it to the high-pressure conduit 52 as high-pressure oil. The high-pressure conduit 52 is connected to each brake hydraulic pressure control device 38, 40, 46, 48, and an accumulator 56 is connected in the middle thereof.
[0021]
The brake hydraulic pressure control devices 38, 40, 46, and 48 are respectively provided with wheel cylinders 58FL, 58FR, 58RL, and 58RR for the corresponding wheels, and 3-port 2-position switching electromagnetic control valves 60FL, 60FR, 60RL, and 60RR. The normally open type electromagnetic on / off valves 64FL, 64FR, 64RL, 64RR and the normally closed type electromagnetic on / off valves 66FL, 66FR provided between the low pressure conduit 62 connected to the reservoir 50 and the high pressure conduit 52 are provided. , 66RL, 66RR. The high-pressure conduits 52 between the on-off valves 64FL, 64FR, 64RL, and 64RR and the on-off valves 66FL, 66FR, 66RL, and 66RR are connected to the control valves 60FL, 60FR, 60RL, and 60RR by connecting conduits 68FL, 68FR, 68RL, and 68RR, respectively. Has been.
[0022]
The control valves 60FL and 60FR respectively connect the brake hydraulic pressure control conduit 36 for the front wheels and the wheel cylinders 58FL and 58FR in communication with each other, and block the communication between the wheel cylinders 58FL and 58FR and the connection conduits 68FL and 68FR. The position is switched to a second position where the communication between the brake hydraulic control conduit 36 and the wheel cylinders 58FL and 58FR is cut off and the wheel cylinders 58FL and 58FR are connected to the connection conduits 68FL and 68FR. .
[0023]
Similarly, the control valves 60RL and 60RR respectively connect the brake hydraulic pressure control conduit 44 for the rear wheels and the wheel cylinders 58RL and 58RR, and disconnect the communication between the wheel cylinders 58RL and 58RR and the connection conduits 68RL and 68RR. The first position is switched to the second position where the communication between the brake hydraulic control conduit 44 and the wheel cylinders 58RL and 58RR is cut off and the wheel cylinders 58RL and 58RR and the connection conduits 68RL and 68RR are connected and connected. It has become.
[0024]
When the control valves 60FL, 60FR, 60RL, 60RR are in the second position, when the on-off valves 64FL, 64FR, 64RL, 64RR and the on-off valves 66FL, 66FR, 66RL, 66RR are controlled to the illustrated state, the wheel cylinder 58FL, 58FR, 58RL, and 58RR are connected to the high-pressure conduit 52 through the control valves 60FL, 60FR, 60RL, and 60RR and the connecting conduits 68FL, 68FR, 68RL, and 68RR, thereby increasing the pressure in the wheel cylinder. .
[0025]
Further, when the control valves 60FL, 60FR, 60RL, 60RR are in the second position, when the on-off valves 64FL, 64FR, 64RL, 64RR are closed and the on-off valves 66FL, 66FR, 66RL, 66RR are opened, The wheel cylinders 58FL, 58FR, 58RL, and 58RR are connected to the low pressure conduit 62 through the control valves 60FL, 60FR, 60RL, and 60RR and the connection conduits 68FL, 68FR, 68RL, and 68RR, thereby reducing the pressure in the wheel cylinder. The
[0026]
Further, in the situation where the control valves 60FL, 60FR, 60RL, 60RR are in the second position, the wheel cylinder 58FL is closed when the on-off valves 64FL, 64FR, 64RL, 64RR and the on-off valves 66FL, 66FR, 66RL, 66RR are closed. , 58FR, 58RL, 58RR are disconnected from both the high pressure conduit 52 and the low pressure conduit 62, so that the pressure in the wheel cylinder is maintained as it is.
[0027]
For this reason, when the control valves 60FL, 60FR, 60RL, and 60RR are in the first position, the braking device 30 controls the wheel cylinders 58FL, 58FR, 58RL, and 58RR according to the amount of depression of the brake pedal 32 by the driver. Generate power. When any of the control valves 60FL, 60FR, 60RL, 60RR is in the second position, the operation of the oil pump 54 and the control valves 60FL, 60FR are not affected by the depression of the brake pedal 32 by the driver. , 60RL, 60RR, on-off valves 64FL, 64FR, 64RL, 64RR and on-off valves 66FL, 66FR, 66RL, 66RR, the braking force of each wheel can be controlled.
[0028]
The control valves 60FL, 60FR, 60RL, and 60RR, the on-off valves 64FL, 64FR, 64RL, and 64RR and the on-off valves 66FL, 66FR, 66RL, and 66RR are controlled by the electric controller 70. As shown in FIG. 2, the electric control apparatus 70 includes a microcomputer 72 and a drive circuit 74. The microcomputer 72 is not shown in detail in FIGS. (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output port device, which are connected to each other via a bidirectional common bus. .
[0029]
A vehicle speed sensor 76, wheel speed sensors 78FL, 78FR, 78RL, 78RR, a longitudinal acceleration sensor 80, a lateral acceleration sensor 82, a yaw rate sensor 84, a steering angle sensor 86, and a diff lock sensor 88 are connected to the microcomputer 72. The vehicle speed sensor 76 detects a vehicle speed V that represents the speed in the front-rear direction of the vehicle (vehicle body). The wheel speed sensors 78FL, 78FR, 78RL, and 78RR measure the rotational speeds of the wheels 24FL to 24RR, thereby representing the wheel speed Vwi (i = fl, fr, rl, rr) representing the speed in the front-rear direction of the wheels 24FL to 24RR. ) Are detected. The longitudinal acceleration sensor 80, the lateral acceleration sensor 82, and the yaw rate sensor 84 detect the longitudinal acceleration Gx, lateral acceleration Gy, and yaw rate γ of the vehicle (vehicle body), respectively. The steering angle sensor 86 detects the steering angle φf of the left and right front wheels 24FL and 24FR by measuring a rotation angle from a reference position of a steering column (not shown). The differential lock sensor 88 detects the locked state of the center differential 14. Note that the lateral acceleration Gy, the yaw rate γ, and the front wheel steering angle φf represent positive detection values when the vehicle turns left, and negative detection values when the vehicle turns right.
[0030]
Here, how to obtain the target wheel speed used in the present invention will be described. An example of a tire model that takes into account the reduction in lateral force during braking, load movement, tire slip angle, and road friction coefficient will be described.
[0031]
As shown in FIG. 8, the generated force Fti (i = fl, fr, rl, rr) 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. To do. Further, the tire slip angle is βi, the tire slip ratio is Si (positive during braking, −∞ <Si <1.0), the road friction coefficient is μ, the tire ground load is Wi, and Ks And Kb are positive coefficients. At this time, the longitudinal force Ftxi and the lateral force Ftyi when the tire is not in a locked state (when ξi ≧ 0) are expressed by the following formulas 1 and 2, respectively. On the other hand, when the tire is in a locked state (when ξi <0), the longitudinal force Ftxi and the lateral force Ftyi are expressed by the following equations 3 and 4, respectively. Note that ξi represents the grip state of the wheel.
[0032]
[Expression 1]

[0033]
[Expression 2]

[0034]
[Equation 3]

[0035]
[Expression 4]

[0036]
As shown in FIG. 9, the coefficient Ks is an inclination with respect to the slip ratio Si when the slip angle Si of the tire is “0” on condition that the slip angle βi is “0”. As shown in FIG. 10, the coefficient Kb is a slope with respect to the tire slip angle βi when the tire slip angle βi is “0” on condition that the slip ratio Si is “0”. Further, cos θi, sin θi, λi, and ξi are expressed by the following equations 5 to 8, respectively.
[0037]
[Equation 5]

[0038]
[Formula 6]

[0039]
[Expression 7]

[0040]
[Equation 8]

[0041]
By partially differentiating the above formulas 1 to 4 with the slip ratio Si, the longitudinal force change and lateral force change of each wheel with respect to a minute slip ratio change of each wheel are expressed by the following formulas 9 and 10.
[0042]
[Equation 9]

[0043]
[Expression 10]

[0044]
Next, the longitudinal force Ftxi and lateral force Ftyi of the tires of each wheel are converted into the vehicle coordinate system by the following formulas 11 to 18, and the longitudinal force Fxi and lateral force Fyi acting on the vehicle center of gravity are calculated, and the moment Mi is calculated. To do. The vehicle coordinate system is a coordinate system in which the center of gravity of the vehicle is the origin, and the longitudinal direction of the vehicle, the lateral direction of the vehicle, and the vertical direction of the vehicle are the X direction, the Y direction, and the Z direction, respectively. In the following equations, φf and φr are the steering angles of the front and rear wheels, respectively, and Tr is the tread width of the vehicle. Lf and Lr are distances from the center of gravity of the vehicle to the front wheel axle and the rear wheel axle, respectively, and T (φf) and T (φr) are expressed by Equations 19 and 20, respectively.
[0045]
## EQU11 ##

[0046]
[Expression 12]

[0047]
[Formula 13]

[0048]
[Expression 14]

[0049]
[Expression 15]

[0050]
[Expression 16]

[0051]
[Expression 17]

[0052]
[Expression 18]

[0053]
[Equation 19]

[0054]
[Expression 20]

[0055]
Similarly, the partial differential values (derivatives) of the longitudinal force and lateral force acting on the vehicle by converting the partial differential values of the longitudinal force Ftxi and lateral force Ftyi of each tire into the vehicle coordinate system by the following equations 21 to 28. Calculate the partial differential value (derivative) of the moment.
[0056]
[Expression 21]

[0057]
[Expression 22]

[0058]
[Expression 23]

[0059]
[Expression 24]

[0060]
[Expression 25]

[0061]
[Equation 26]

[0062]
[Expression 27]

[0063]
[Expression 28]

[0064]
Next, the vehicle longitudinal force Fx, lateral force Fy and moment M generated when the slip rate of each wheel is the target slip rate Si are the sum of the longitudinal force Fxi, lateral force Fyi and moment Mi of each wheel, respectively. As shown in FIG.
[0065]
[Expression 29]

[0066]
Next, the target longitudinal force Fxa, target lateral force Fya, and target moment Ma of the vehicle are calculated by the following equations 30,31. In this calculation, the calculation is performed based on the following concepts (A) and (B). The right side of Equation 30 represents the longitudinal force, lateral force and moment generated by each wheel when the slip ratio is “0”.
[0067]
(A) The target longitudinal force Fxt and the target moment Mt for stabilizing the vehicle behavior by the vehicle motion control are not controlled (the slip ratio Si is “0” and the motion control is not required). It is considered that the amount of addition to the longitudinal force Fxso and the moment Mso generated at the time.
[0068]
(B) By reducing the lateral force Fyso when the motion is not controlled to the target lateral force Fya, the reduction of the lateral force during the motion control is reduced as much as possible.
[0069]
[30]

[0070]
[31]

[0071]
The longitudinal force change dFx, lateral force change dFy, and moment change dM acting on the vehicle body due to the minute change dSi of the slip ratio of the four controlled wheels are calculated by the following equation (32). In Equation 32, dSfr, dSfl, dSrr, dSrl are the minute change amounts of the slip ratios of the right front wheel 24FR, the left front wheel 24FL, the right rear wheel 24RR, and the left rear wheel 24RL, respectively, and J is a Jacobian matrix.
[0072]
[Expression 32]

[0073]
Next, a target slip ratio Si for realizing the target longitudinal force Fxa and the target moment Ma is calculated. However, since it is difficult to analytically solve the target slip ratio Si, it is obtained by the following convergence calculation.
[0074]
If each difference between the current longitudinal force Fx, lateral force Fy and moment M and the target longitudinal force Fxa, target lateral force Fya and target moment Ma is Δ, Δ is expressed by the following equation 33, and this Δ is expressed as “0 "Slip rate correction amount δS that minimizes the evaluation function L expressed by the following equation 34 is obtained using T as a transpose.
[0075]
[Expression 33]

[0076]
[Expression 34]

[0077]
The slip ratio correction amount δS that minimizes the evaluation function L of the above equation 34 is as the following equation 35. However, Fx, Fy and M are the longitudinal force, lateral force and moment (Equation 29) generated according to the current slip ratio of the controlled wheel, respectively. Fxa, Fya and Ma are the target longitudinal force and the desired lateral force, respectively. The force and the target moment (Equation 31), S and δS are the slip ratio and slip rate correction amount of each wheel represented by Equations 36 and 37, respectively, and E is the Δ and δS represented by Equation 38. It is each difference with the amount of correction of the longitudinal force, lateral force and moment. Wds, Ws, and Wf are weights for the slip rate correction amount δS, the slip rate Si, and each force, respectively, and each weight is “0” or a positive value.
[0078]
[Expression 35]

[0079]
[Expression 36]

[0080]
[Expression 37]

[0081]
[Formula 38]

[0082]
Therefore, by correcting the previous target slip ratio Si by the slip ratio correction amount δSi, the target slip ratio Si of each wheel that achieves the target longitudinal force Fxa, the target lateral force Fya, and the target moment Ma can be calculated.
[0083]
Next, the vehicle body reference speed Vb is calculated by geometrically converting the reference wheel speed Vw into the position of the center of gravity of the vehicle by the following equation (39). The reference wheel speed Vw is the wheel speed of the turning inner front wheel. For example, when turning right, the wheel speed Vwfr of the right front wheel 24FR becomes the reference wheel speed. Conversely, when turning left, the wheel speed VwFL of the left front wheel 24FL becomes the reference wheel speed. Further, when the vehicle turns, in order to correct the speed difference between the left and right wheels caused by the yaw rate, Vyr is added as a correction coefficient to calculate the vehicle body reference speed Vb. However, the correction coefficient Vyr is expressed by the following equation 40.
[0084]
[39]

[0085]
[Formula 40]

[0086]
Next, the vehicle body reference speed Vb is geometrically converted to each wheel position other than the reference wheel from the above formula 39, and each wheel position speed Vbi other than the reference wheel is calculated from the following formula 41.
[0087]
[Expression 41]

[0088]
Next, the target wheel speed Vri of the wheel speed of each wheel other than the reference wheel is calculated. The target wheel speed Vri of each wheel other than the reference wheel can be calculated by the following equation 42 according to the target slip ratio Si.
[0089]
[Expression 42]

[0090]
Next, the vehicle motion control in the present embodiment will be described with reference to the flowcharts shown in FIGS. When the ignition switch is closed, the microcomputer 72 starts to repeatedly execute the main program of FIG. 3 every predetermined short time.
[0091]
The execution of the main program is started in step S10 in FIG. 3, the target slip ratio Si of each wheel is set to “0” as an initial value in step S12, and the sensors 76 to 88 are set in step S14. Input the detection signal.
[0092]
Next, in step S16, a behavior determination routine is executed to determine whether the vehicle behavior is abnormal, that is, whether the vehicle motion state is in a spin state or a drift-out state.
[0093]
This behavior determination routine is shown in detail in FIG. 4. The execution is started in step S100, and the slip angle β of the vehicle body is calculated in step S102. Specifically, the side slip speed Vy of the vehicle body is calculated by the following equation 43 using the lateral acceleration Gy, the vehicle speed V, and the yaw rate γ input in the process of step S14, and the calculated side slip speed Vy of the vehicle body and the calculated The slip angle β of the vehicle body is calculated by the following equation 44 using the vehicle longitudinal speed Vx (= vehicle speed V) input in step S14. Note that Vyd is the side slip acceleration Vyd of the vehicle.
[0094]
[Equation 43]

[0095]
(44)

[0096]
Next, in step S104, the rear wheel slip angle βr is calculated by the following equation 45 using the calculated vehicle body slip angle β, the vehicle speed V and the yaw rate γ. Lr is a distance in the vehicle front-rear direction between the center of gravity of the vehicle and the rear wheel axle, and is a constant given in advance according to the vehicle type. Further, when the traveling direction of the rear wheel is counterclockwise with respect to the direction of the center plane of the rear wheel, the rear wheel slip angle βr is positive.
[0097]
[Equation 45]

[0098]
After calculating the rear wheel slip angle βr, the vehicle behavior is abnormal by determining whether the absolute value | βr | of the slip angle βr is within the reference value βrc in steps S106 and S108. That is, whether the vehicle is in a spin state or a drift-out state. If the absolute value | βr | of the rear wheel slip angle βr is within the predetermined reference value βrc and the vehicle behavior is normal, both “NO”, that is, the slip angle βr is determined in steps S106 and S108. It is determined that it is smaller than the positive reference value βrc and larger than the negative reference value βrc, and in step S110, the flag FLG is set to “0” representing normal vehicle behavior.
[0099]
On the other hand, if the slip angle βr is larger than the positive reference value βrc, “YES” in step S 106, that is, it is determined that the vehicle behavior is abnormal, and the slip angle βr of the rear wheel is determined to be a positive reference value in step S 112. In addition to setting to βrc, in step S116, the flag FLG is set to “1” representing an abnormality in the vehicle behavior. If the slip angle βr is smaller than the negative reference value −βrc, “YES” in step S108, that is, the vehicle behavior is determined to be abnormal, and the slip angle βr of the rear wheel is determined to be a negative reference in step S114. The value is set to -βrc, and the flag FLG is set to "1" representing an abnormal vehicle behavior in step S116. After the process of step S110 or step S116, the execution of this behavior determination routine is terminated in step S118.
[0100]
Returning to the description of the main program in FIG. 3, after the execution of the behavior determination routine in step S16, it is determined in step S18 whether or not the flag FLG is “1”, that is, whether the vehicle is abnormal in behavior. judge. As described above, if the behavior of the vehicle is normal and the flag FLG is set to “0”, “NO” is determined in step S18, and the execution of the main program is terminated in step S44. In this case, the left and right front wheels 24FL and 24FR and the left and right rear wheels 24RL and 24RR are given a braking force according to the depression operation of the brake pedal 32, and the vehicle behavior control according to the present invention is not performed.
[0101]
  On the other hand, if the behavior of the vehicle is abnormal and the flag FLG is set to “1”, “YES” is determined in step S18, and an exercise state quantity calculation routine is executed in step S20. This exercise state quantity calculation routine is shown in detail in FIG. 5, and its execution is started in step S200. After the start, step S202Then, the following formula 46 using the front wheel steering angle φf, the yaw rate γ and the vehicle speed V input by the process of step S14 and the vehicle body slip angle β calculated by the process of the behavior determination routine of step S16, The front wheel slip angle βf is calculated. However, Lf is a predetermined constant representing the distance in the vehicle longitudinal direction between the center of gravity of the vehicle and the front wheel axle. When the traveling direction of the front wheels is counterclockwise with respect to the direction of the center plane of the front wheels, the front wheel slip angle βf is positive.
[0102]
[Equation 46]

[0103]
Next, in step S204, the friction coefficient μ of the road surface with respect to the tire is estimated and calculated by the following equation 47 using the longitudinal acceleration Gx and lateral acceleration Gy of the vehicle body input by the processing of step S14. However, g is a gravitational acceleration.
[0104]
[Equation 47]

[0105]
In step S206, the load movement amount ΔWi of each wheel is calculated by multiplying the longitudinal acceleration Gx and the lateral acceleration Gy of the vehicle body by constants, and the support load Wi of each wheel is determined in advance and the static load Wsi and load movement of each wheel. It is calculated as the sum (Wsi + ΔWi) with the amount ΔWi. For example, when the vehicle is braked and the longitudinal acceleration Gx is negative, the front wheel support loads Wfl and Wfr increase, and when the vehicle is turning, the support load of the turning outer wheel increases.
[0106]
In step S208, a judgment value ξi representing the grip state (lock state) for each wheel is calculated by executing the calculations of the above formulas 7 and 8. In the calculation of Equation 7, the target slip ratio Si previously calculated in step S24, that is, the current slip ratio Si, and the above-described coefficients Ks and Kb (predetermined predetermined values shown in FIGS. 9 and 10) and And the slip angle βr of the rear wheel set in steps S202 or S112 and 114 as the slip angle βi is used as the slip angle βi. In the calculation of Expression 8, the calculated λi, the coefficient Ks, the previously calculated target slip ratio Si, that is, the current slip ratio Si, the road friction coefficient μ calculated in step S204, The support load Wi of each wheel calculated in step S206 is used.
[0107]
After the process of step S208, based on the determination value ξi calculated in step S210, it is determined whether or not the wheel is in a grip state, in other words, whether or not the wheel is in a locked state. If the wheel is in the grip state (not in the locked state) and the determination value ξi is “0” or more, “YES” is determined in step S210, and the process proceeds to step S212. On the other hand, if the wheel is not in a grip state (is in a locked state) and the determination value ξi is less than “0”, it is determined “NO” in step S210, and the process proceeds to step S214.
[0108]
In step S212, the longitudinal force Ftxi and the lateral force Ftyi of each wheel are calculated by the calculations of equations 5, 6, 1 and 2. In the calculations of Equations 5 and 6, cos θi and sin θi are calculated using λi calculated by the processing of step S208 and Si, Ks, Kb, βi used for the calculation of step S208. In the calculations of Equations 1 and 2, the longitudinal force Ftxi and lateral force Ftyi of each wheel are calculated using the above-mentioned ξi, Si, cos θi, sin θi, μ, Wi, βi, Ks, Kb.
[0109]
In step S214, the longitudinal force Ftxi and the lateral force Ftyi of each wheel are calculated using the above formulas 5, 6, 3, and 4. The calculations of equations 5 and 6 are the same as described above. In the calculations of equations 3 and 4, the longitudinal force Ftxi and the lateral force Ftyi of each wheel are calculated using the calculated cos θi, sin θi, μ, and Wi. In addition, the process of step S210-214 is performed for every wheel.
[0110]
After the processing in steps S212 and 214, in step S216, the front wheel steering angle φf input by the processing in step S14 and the longitudinal force Ftxi and lateral force Ftyi of each wheel calculated in steps S212 and 214 are used. Each wheel component Fxfl, Fxfr, Fxrl, Fxrr with respect to the longitudinal force Fx of the vehicle and the components Fyfl, Fyfr, Fyrl, Fyrr with respect to the lateral force Fy, and the moment M with respect to the moment M by the calculation of the above formulas 11 to 20. The components Mfl, Mfr, Mrl, Mrr are calculated.
[0111]
Next, in step S218, the actual longitudinal force of the vehicle is calculated by the above equation 29 using the longitudinal force component Fxi, lateral force component Fyi, and moment component Mi of the vehicle center of gravity position calculated by the processing in step S216. Fx, lateral force Fy and moment M are calculated. Then, the execution of the motion state quantity calculation routine in step S220 is terminated.
[0112]
Returning to the description of the program in FIG. 3 again, after the execution of the motion state amount calculation routine in step S20, in step S22, a suppression amount calculation routine for calculating a suppression amount for suppressing vehicle spin and drift-out. Execute. This suppression amount calculation routine is shown in detail in FIG. 6, and its execution is started in step S300.
[0113]
After the start, in step S302, the target yaw rate γc is calculated by the following equation 48 using the front wheel steering angle φf and the vehicle speed V input in the process of step S14. Note that the target yaw rate γc may be calculated by the calculation of the following formula 49. However, n in the following equation 48 is a steering gear ratio which is a predetermined constant value, and Kh and H in the following equations 48 and 49 are a stability factor and a wheel which are predetermined constant values. Is the base.
[0114]
[Formula 48]

[0115]
[Formula 49]

[0116]
In step S302, the reference yaw rate γt is calculated by the calculation of the following formula 50 using the calculation result of formula 48. However, in the following formula 50, T is a predetermined time constant, and s is a Laplace operator. Note that the reference yaw rate γt may be calculated by the following calculation of 50 using the calculation result of the above 49.
[0117]
[Equation 50]

[0118]
Next, in step S304, the drift-out amount Dv representing the deviation between both yaw rates γt and γ is calculated by the following equation 51 using the calculated reference yaw rate γt and the yaw rate γ input by the processing of step S14. calculate.
[0119]
[Formula 51]

[0120]
Next, in step S306, the turning direction of the vehicle is determined based on the sign of the input yaw rate γ. If the vehicle is turning left, the drift-out state amount Ds is set to the calculated drift-out amount Dv. If the vehicle is turning right, the drift-out state quantity Ds is set to a value -Dv obtained by reversing the calculated drift-out quantity Dv.
[0121]
Next, in step S308, a coefficient Kg corresponding to the calculated drift-out state quantity Ds is derived by referring to a map built in the microcomputer 72 and corresponding to the graph shown in FIG. . In step 310, the vehicle slip angular velocity βd, the vehicle target slip angle βt, and the vehicle target slip angular velocity βtd are calculated. In calculating the vehicle slip angular velocity βd, the vehicle slip angle β calculated in the behavior determination routine of step S16 is differentiated. Further, in order to calculate the target slip angle βt of the vehicle, first, the following equation 52 using the target yaw rate γc calculated in step S302 (equation 48) and the vehicle speed V input in step S14 is performed. A target lateral acceleration Gyc is calculated. Instead of this, the target lateral acceleration Gyc may be calculated by executing the calculation of Formula 49. Then, a target slip angle βt corresponding to the target lateral acceleration Gyc is calculated using a predetermined function parameter representing characteristics as shown in FIG. However, in this case, the upper and lower limits of the target slip angle βt are limited to K * μ and −K * μ. In addition, this K is a predetermined value (for example, about 0.4) predetermined for each vehicle type.
[0122]
[Formula 52]

[0123]
In step S312, the vehicle slip angle β and angular velocity βd calculated in step S310 and the vehicle target slip angle βt and target slip angular velocity βtd calculated in step S310 are calculated by the following equation 53. A target moment Mt for stabilizing the behavior is calculated. However, Km1 and Km2 are positive constants determined as appropriate. The target slip angle βt and the target slip angular velocity βtd may both be “0”.
[0124]
[53]

[0125]
Next, in step S314, the target longitudinal force Fxt for stabilizing the behavior of the vehicle is calculated by the following equation 54 using the calculated coefficient Kg. Here, Mass is a predetermined constant representing the mass of the vehicle, and g is gravitational acceleration.
[0126]
[Formula 54]

[0127]
Next, in step S316, the longitudinal force Fxso, the lateral force Fyso, and the moment Mso of the vehicle when the slip ratio of each wheel is 0 are calculated by the calculation of Equation 30 above. In the calculation of Equation 30, variables such as Fxfrso, Fxflso,... Mrlso are calculated with the slip rate Si set to “0” by the calculation of the components of each wheel similar to the processing in Step S216 (Equations 11 to 20). To do.
[0128]
Next, in step S318, the vehicle longitudinal force Fxso, lateral force Fyso, and moment Mso calculated by the processing in step S316 and the predetermined target longitudinal force Fxt and target moment Mt are used. The target longitudinal force Fxa, lateral force Fya, and moment Ma of the vehicle are calculated by calculation.
[0129]
Next, in step S320, the front and rear of each wheel with respect to a minute change in slip ratio by the calculation of the above formulas 9 and 10 using the front and rear force Ftxi and lateral force Ftyi of each wheel calculated by the processing of steps S212 and 214. While calculating the change in force and the change in lateral force, and using the longitudinal force component Fxi, the lateral force component Fyi, and the moment component Mi of the center of gravity position of the vehicle calculated by the processing in step 216, the above formulas 21 to 28 are used. By calculating, the derivative of vehicle longitudinal force ∂Fxi / ∂Si, the derivative of lateral force ∂Fyi / ∂Si, and the derivative of moment ∂Mi / ∂Si are calculated.
[0130]
Next, in step S322, the target longitudinal force Fxa, lateral force Fya, moment Ma of the vehicle calculated by the process of step S318, and the actual longitudinal force Fx, lateral force Fy of the vehicle calculated by the process of step S218. And the correction amount δFx of the longitudinal force of the vehicle, the correction amount δFy of the lateral force, and the correction amount δM of the moment are calculated by the calculation of the above Expression 33 using the moment M. Then, the execution of the suppression amount calculation routine in step S324 is terminated.
[0131]
Returning to the description of the program in FIG. 3 again, after execution of the suppression amount calculation routine in step S22, a target slip ratio calculation routine for calculating the target slip ratio is executed in step S24. This suppression amount calculation routine is shown in detail in FIG. 7, and its execution is started in step S400.
[0132]
After the start, in step S402, the difference Δ () between the current vehicle longitudinal force Fx, lateral force Fy, moment M and target longitudinal force Fxa, target lateral force Fya, target moment Ma calculated by the processing of step S322. The correction amount δSi of the slip ratio of each wheel is calculated by the above calculations 34 and 35 using the correction amount δFx of the longitudinal force of the vehicle, the correction amount δFy of the lateral force, and the correction amount δM of the moment. However, the equation 35 calculates the correction amount δSi of the slip ratio of each wheel that minimizes the evaluation function L expressed by the equation 34.
[0133]
Next, in step S404, the correction amount δSi of each wheel slip ratio calculated by the process in step S402 and the target slip ratio Si previously calculated in step S24, that is, the current slip ratio Si are used. The target slip ratio Si of each wheel is calculated by the following equation 55. Then, the execution of the suppression amount calculation routine in step S406 is terminated.
[0134]
[Expression 55]

[0135]
  Returning to the description of the flowchart of FIG. 3, after calculating the target slip ratio in step S24, the microcomputer 72 determines that the center differential 14 is locked based on the signal from the differential lock sensor 88 in step S26. Judge whether there is. If the center differential 14 is not in the locked state, “NOAnd the target wheel speed Vri of each wheel is calculated by the processing of steps S28 to S32. On the other hand, if the center differential 14 is in the locked state, “YESAnd the target wheel speed Vri of each wheel is calculated by the processing of steps S34 to S40.
[0136]
First, the case where the center differential 14 is not in the locked state will be described. In step S28, any one of the wheels 24FL, 24FR, 24RL, and 24RR is determined as a reference wheel, and the wheel speeds Vwfl, Vwfr, Vwrl, and Vwrr input by the processing in step S14 are used. The vehicle body reference speed Vb is calculated by converting the wheel speed Vwi of the reference wheel into the speed of the center of gravity of the vehicle using the above equation (39). In this type of vehicle behavior control, it is common to use the turning inner front wheel with the smallest detection error of the wheel speed as a reference wheel. Specifically, if the vehicle is turning left, the left front wheel 24FL is determined as the reference wheel, and if the vehicle is turning right, the right front wheel 24FR is determined as the reference wheel. Accordingly, in step S28, the turning direction of the vehicle is determined based on the yaw rate γ input in the process of step S14. If the vehicle is turning left, the left front wheel 24FL is determined as the reference wheel, and the left front wheel 24FL The vehicle body reference speed Vb is calculated by the calculation of Formula 39 using the correction coefficient Vyr for correcting the wheel speed difference between the left and right wheels caused by the wheel speed Vwfl and the yaw rate γ. If the vehicle is turning right, the right front wheel 24FR is determined as the reference wheel, and the vehicle body reference speed Vb is calculated by the calculation of Formula 39 using the wheel speed Vwfr of the right front wheel 24FR.
[0137]
Next, in step S30, the calculation of Formula 41 using the calculated vehicle body reference speed Vb, the front wheel steering angle φf and the yaw rate γ input by the processing in step S14, and the predetermined tread width Tr of the vehicle. To estimate and calculate the wheel speeds Vbi of the three wheels other than the reference wheel. Specifically, Vbfr, Vbrl, Vbrr are calculated when the vehicle turns left, and Vbfl, Vbrl, Vbrr are calculated when the vehicle turns right.
[0138]
In step S32, the wheel speed Vbi of each of the three wheels other than the calculated reference wheel and the target slip ratio Si calculated by executing the target slip ratio calculation routine in step S24 are used to calculate the above formula 42, so that the wheels other than the reference wheel The target wheel speed Vri is calculated. Specifically, Vrfr, Vrrl, and Vrrr are calculated when the vehicle turns left, and Vrfl, Vrrl, and Vrrr are calculated when the vehicle turns right.
[0139]
After the process of step S32, in step S42, the microcomputer 72 controls the various on-off valves in the braking device 30 via the drive circuit 74, thereby releasing the braking on the reference wheel and the other three wheels. Is controlled to the calculated target wheel speed Vri. In step S44, the execution of the main program is temporarily terminated.
[0140]
First, the electromagnetic control valves 60FL, 60FR, 60RL, 60RR provided in the brake hydraulic control devices 38, 40, 46, 48 respectively corresponding to the left and right front wheels 24FL, 24FR and the left and right rear wheels 24RL, 24RR are shown in FIG. By switching from the first position shown to the second position, the depression operation of the brake pedal 32 is transmitted to the brake hydraulic control devices 38, 40, 46, 48 via the brake hydraulic control conduits 36, 44. Is impossible. By this control, the application of the braking force to the left and right front wheels 24FL and 24FR and the left and right rear wheels 24RL and 24RR does not depend on the driver's depression operation of the brake pedal 32.
[0141]
Simultaneously with the above control, the on-off valve is controlled so that the brake hydraulic pressure is not applied to the wheel cylinder corresponding to the reference wheel. Specifically, if the vehicle is turning left, the on-off valve 64FL corresponding to the left front wheel 24FL as the reference wheel is closed and the on-off valve 66FL is opened. If the vehicle is turning right, the on-off valve 64FR corresponding to the right front wheel 24FR as the reference wheel is closed and the on-off valve 66FR is opened. As a result, braking on the reference wheel is released.
[0142]
On the other hand, with respect to the other three wheels, the other three wheels are set such that the detected wheel speeds Vwi detected by the wheel speed sensors corresponding to the respective wheels coincide with the respective target wheel speeds Vri calculated by the process of step S32. By controlling the opening / closing valves corresponding to the wheels, the supply of braking hydraulic pressure to the wheel cylinders corresponding to the three wheels is controlled. Specifically, if the vehicle is turning left, according to each comparison between the detected wheel speeds Vwfr, Vwrl, Vwrr of the right front wheel 24FR and the left and right rear wheels 24Rl, 24RR and the target wheel speeds Vrfr, Vrrl, Vrrr. The on-off valves 64FR, 64RL, and 64RR and the on-off valves 66FR, 66RL, and 66RR are controlled to open and close.
[0143]
That is, if each detected wheel speed Vwfr, Vwrl, Vwrr is larger than each target wheel speed Vrfr, Vrrl, Vrrr, the on-off valves 64FR, 64RL, 64RR are opened, and the on-off valves 66FR, 66RL, 66RR are closed. Then, the braking pressure of the wheel cylinders 58FR, 58RL, 58RR is increased. Conversely, if the detected wheel speeds Vwfr, Vwrl, Vwrr are smaller than the target wheel speeds Vrfr, Vrrl, Vrrr, the on-off valves 64FR, 64RL, 64RR are closed and the on-off valves 66FR, 66RL, 66RR are respectively closed. The valve is opened to reduce the braking pressure of the wheel cylinders 58FR, 58RL, 58RR. If the detected wheel speeds Vwfr, Vwrl, Vwrr are equal to the target wheel speeds Vrfr, Vrrl, Vrrr, the on-off valves 64FR, 64RL, 64RR are closed and the on-off valves 66FR, 66RL, 66RR are closed. Thus, the braking pressure of the wheel cylinders 58FR, 58RL, 58RR is maintained. As a result, the detected wheel speeds Vwfr, Vwrl, Vwrr of the right front wheel 24FR and the left and right rear wheels 24Rl, 24RR and the target wheel speeds Vrfr, Vrrl, Vrrr are controlled to coincide with each other.
[0144]
If the vehicle is turning right, it opens and closes according to the comparison between the detected wheel speeds Vwfl, Vwrl, Vwrr of the left front wheel 24FL and the left and right rear wheels 24Rl, 24RR and the target wheel speeds Vrfl, Vrrl, Vrrr. The valves 64FL, 64RL, 64RR and the on-off valves 66FL, 66RL, 66RR are controlled to open and close in the same manner as in the case of the left turn. Thus, the detected wheel speeds Vwfl, Vwrl, Vwrr of the left front wheel 24FL and the left and right rear wheels 24Rl, 24RR are controlled so as to coincide with the target wheel speeds Vrfl, Vrrl, Vrrr, respectively.
[0145]
As a result, the wheel speed Vwi of each wheel is controlled so that the wheel speeds other than the reference wheel become the target wheel speed Vri corresponding to the target slip ratio Si for correcting the behavior of the vehicle such as vehicle spin and drift-out. Therefore, the behavior of the vehicle, particularly the behavior at the time of turning can be reliably stabilized.
[0146]
Next, the case where the center differential 14 is in the locked state will be described. Even in this state, as in step S28, any one of the wheels 24FL, 24FR, 24RL, 24RR is determined as a reference wheel, and in step S34, each wheel speed Vwfl input by the processing in step S14 is determined. , Vwfr, Vwrl, and Vwrr are used to calculate the vehicle body reference speed Vb by converting the wheel speed Vwi of the reference wheel into the speed of the vehicle center of gravity using the above equation (39).
[0147]
Next, in step S36, the vehicle body reference speed Vb calculated this time in step S34 and the vehicle body reference speed calculated last time are calculated by the following equation 56 using the vehicle body reference speed Vb calculated in the process of step S34. The value obtained by comparing Vb with the corrected value is calculated as the vehicle body reference speed Vb. However, Vb_last is the vehicle body reference speed calculated last time, α is a constant of 0.05 to 0.1, and Δt is a sampling period of calculation.
[0148]
[Expression 56]

[0149]
Next, in step S38, the calculation of the equation 41 using the calculated vehicle body reference speed Vb, the front wheel steering angle φf and the yaw rate γ input by the processing in step S14, and the predetermined tread width Tr of the vehicle. To estimate and calculate the wheel speeds Vbi of the three wheels other than the reference wheel. Specifically, Vbfr, Vbrl, Vbrr are calculated when the vehicle turns left, and Vbfl, Vbrl, Vbrr are calculated when the vehicle turns right.
[0150]
Next, in step S40, the calculation of the above equation 42 using the calculated wheel speeds Vbi of the three wheels other than the reference wheel and the target slip ratio Si calculated by executing the target slip ratio calculation routine in step S24. The target wheel speed Vri other than the reference wheel and the turning inner rear wheel is calculated. Specifically, Vrfr and Vrrr are calculated when the vehicle turns left, and Vrfl and Vrrl are calculated when the vehicle turns right. Further, when the center differential 14 is locked, the relationship represented by the following formula 57 is established. That is, the sum of the wheel speeds Vwfl and Vwfr of the left and right front wheels and the sum of the wheel speeds Vwrl and Vwrr of the left and right rear wheels are equal.
[0151]
[Equation 57]

[0152]
Based on this relationship, the target wheel speed of the turning rear rear wheel is calculated by the following formulas 58 and 59 using the wheel speed input by the processing of step S14. Specifically, Vrrl is calculated by the calculation of Formula 58 when the vehicle turns left, and Vrrr is calculated by the calculation of Formula 59 when the vehicle turns right.
[0153]
[Formula 58]

[0154]
[Formula 59]

[0155]
After the processing in step S40, in step S42, the microcomputer 72 controls the various on-off valves in the braking device 30 via the drive circuit 74, thereby releasing the braking on the reference wheel and the other three wheels. Is controlled to the calculated target wheel speed Vri. In step S44, the execution of the main program is temporarily terminated.
[0156]
Even when the center differential 14 is in the locked state, the brake hydraulic control devices 38 and 40 corresponding to the left and right front wheels 24FL and 24FR and the left and right rear wheels 24RL and 24RR, respectively, as in the case where the center differential 14 is not in the locked state. , 46, 48 are switched from the first position to the second position by the electromagnetic control valves 60FL, 60FR, 60RL, 60RR. By this control, the application of the braking force to the left and right front wheels 24FL and 24FR and the left and right rear wheels 24RL and 24RR does not depend on the driver's depression operation of the brake pedal 32.
[0157]
Further, as in the case where the center differential 14 is not in the locked state, the on-off valve is controlled so that the braking hydraulic pressure is not applied to the wheel cylinder corresponding to the reference wheel. On the other hand, as for the other three wheels, each detected wheel speed Vwi detected by the wheel speed sensor corresponding to each wheel is calculated by the process of step S40, as in the case where the center differential 14 is not locked. The supply of braking hydraulic pressure to the wheel cylinders corresponding to the three wheels is controlled by controlling the opening / closing valves corresponding to the other three wheels so as to match the target wheel speed Vri. Thus, if the vehicle is turning left, control is performed so that the detected wheel speeds Vwfr, Vwrl, Vwrr of the right front wheel 24FR and the left and right rear wheels 24Rl, 24RR coincide with the target wheel speeds Vrfr, Vrrl, Vrrr, respectively. Is done.
[0158]
If the vehicle is turning right, the detected wheel speeds Vwfl, Vwrl, Vwrr of the left front wheel 24FL and the left and right rear wheels 24Rl, 24RR are controlled so as to match the target wheel speeds Vrfl, Vrrl, Vrrr, respectively. Is done.
[0159]
As a result, also in this case, the wheel speed Vwi of each wheel is set so that the wheel speeds other than the reference wheel become the target wheel speed Vri corresponding to the target slip ratio Si for correcting the behavior of the vehicle such as vehicle spin and drift-out. Is controlled, it is possible to reliably stabilize the behavior of the vehicle, particularly when turning.
[0160]
Further, according to the above embodiment, in step S40, the front wheels on the inner side of the turn are used as reference wheels, and the target wheel speeds of the two front and rear wheels on the outer side of the turn are calculated so as to mainly correct the abnormal behavior of the vehicle. It is calculated so as to absorb the restriction of the rotational speed difference between the front and rear wheels due to the locked state of the center differential 14 at the target wheel speed of the rear wheel.
[0161]
Thus, even if the center differential 14 is in a locked state, for example, while the vehicle is turning left, even if the target wheel speed Vrfr of the right front wheel 24FR that is the front wheel outside the turn is reduced, the left wheel that is the rear wheel inside the turn The wheel speed of the right rear wheel 24RR, which is a rear wheel outside the turn important for correcting the behavior of the vehicle, is absorbed in order to absorb the restriction of the rotational speed difference between the front and rear wheels due to the locked state of the center differential 14 at the target wheel speed Vrrl of the rear wheel 24RL. Vrrr is no longer reduced, the lateral force generated by the right rear wheel 24RR is maintained appropriately, and the vehicle behavior abnormality is corrected appropriately. Further, even if the target wheel speed Vrfl of the left front wheel 24FL that is the front wheel outside the turn is decreased while the vehicle is turning right, the wheel speed of the left rear wheel 24RL that is the rear wheel outside the turn is the same as when turning left. Vrrl does not decrease, the lateral force generated by the left rear wheel 24RL is properly maintained, and the behavioral abnormality of the vehicle is corrected appropriately.
[0162]
Further, according to the above embodiment, the smaller value of the vehicle body reference speed Vb calculated this time in step S36 and the value Vb_last + (Gx + α) * Δt obtained by correcting the vehicle body reference speed Vb calculated last time is set to the vehicle body. By deriving as the reference speed Vb, a predetermined restriction is applied to the increase in wheel speed detected by the wheel speed sensor corresponding to the reference wheel, and the restricted wheel speed is set as the reference wheel speed.
[0163]
As a result, for example, while the vehicle is turning left, the target wheel speed Vrfr of the right front wheel 24FR, which is the front wheel outside the turn, is reduced. As a result, the rotational speed of the left front wheel 24FL, which is the reference wheel, rapidly increases with slip. However, the wheel speed Vwfl of the left front wheel 24FL is detected with high accuracy. Therefore, the target wheel speed Vbi of the other three wheels calculated based on the reference wheel speed Vb becomes appropriate, and the vehicle behavior abnormality can be corrected accurately. Further, while the vehicle is turning right, the target wheel speed Vrfl of the left front wheel 24FL, which is the front wheel outside the turn, is reduced. As a result, even if the wheel speed Vwfr of the right front wheel 24FR, which is the reference wheel, suddenly increases, The wheel speed Vwfr of the front wheel 24FR is detected with high accuracy, and the vehicle behavior abnormality can be corrected accurately in the same way as when turning left.
[0164]
In the above embodiment, the reference wheel is the front wheel on the turning inner side, but the reference wheel may be implemented as the rear wheel on the turning inner side. In this case, the target wheel speeds (target slip ratios) of the front wheels and the rear wheels outside the turn are set to the wheel speeds (reference wheel speeds) of the rear wheels inside the turn that are the reference wheels, and the vehicle motion state quantity (for example, longitudinal acceleration). In accordance with Gx, lateral acceleration Gy, and yaw rate γ), target wheel speeds (target slip ratios) for the front and rear wheels outside the turn for correcting the behavior of the vehicle are calculated in the same manner as in the above embodiment. At the same time, the target wheel speed of the front wheel inside the turn may be calculated by calculating the wheel speed of the front wheel outside the turn from the total wheel speed of the left and right rear wheels. In some cases, the front wheel or the rear wheel on the outside of the turn can be used as a reference wheel.
[0165]
Furthermore, the vehicle behavior control device according to the present invention described in the above embodiment is not limited to a mechanical differential diff lock device, and transmits torque using shearing of a viscous fluid with high viscosity. It may be a viscous differential lock device that generates an operation limiting torque when the differential operation occurs.
[Brief description of the drawings]
FIG. 1 is a configuration diagram schematically illustrating a configuration of a vehicle behavior control apparatus according to an embodiment of the present invention.
FIG. 2 is a configuration diagram schematically illustrating a configuration of a braking device according to an embodiment of the present invention.
FIG. 3 is a flowchart showing vehicle behavior control executed by the microcomputer of FIG. 2;
FIG. 4 is a flowchart showing details of a behavior determination routine in the vehicle behavior control program.
FIG. 5 is a flowchart showing details of a motion state calculation routine in the vehicle behavior control program.
FIG. 6 is a flowchart showing details of a suppression amount calculation routine in the vehicle behavior control program.
FIG. 7 is a flowchart showing details of a target slip ratio calculation routine in the vehicle behavior control program.
FIG. 8 is an explanatory diagram for explaining a force generated in each wheel.
FIG. 9 is a graph showing the relationship between the slip ratio Si and the longitudinal force Ftxi.
FIG. 10 is a graph showing the relationship between slip angle βi and lateral force Ftyi.
FIG. 11 is a graph showing a relationship between a drift-out state quantity Ds and a coefficient Kg.
FIG. 12 is a graph showing the relationship between the target lateral acceleration Gyc and the target slip angle βt of the vehicle body.
[Explanation of symbols]
32 ... Brake pedal, 34 ... Master cylinder, 38, 40, 46, 48 ... Brake hydraulic control device, 58FL, 58FR, 58RL, 58RR ... Wheel cylinder, 72 ... Microcomputer, 76 ... Vehicle speed sensor, 78FL, 78FR, 78RL, 78RR ... Wheel speed sensor, 80 ... Longitudinal acceleration sensor, 82 ... Lateral acceleration sensor, 84 ... Yaw rate sensor, 86 ... Steering angle sensor, 88 ... Differential lock sensor

Claims (6)

A braking device capable of independently controlling the braking force of the four wheels consisting of the left and right front wheels and the left and right rear wheels, and allowing the rotational speed difference between the front and rear wheels in the unlocked state and the rotational speed difference between the front and rear wheels in the locked state In a vehicle behavior control device that is applied to a vehicle having a center differential with a lock mechanism that is prohibited, and corrects the behavior of the vehicle in response to detection of an abnormal behavior of the vehicle when the vehicle turns,
A wheel speed sensor for detecting each wheel speed of the four wheels;
A steering angle sensor for detecting the steering angle of the steering wheel of the vehicle;
A movement state quantity detecting means for detecting a movement state quantity of the vehicle;
One of the four wheels is used as a reference wheel, and a wheel speed detected by a wheel speed sensor corresponding to the reference wheel is used as a reference wheel speed, and the reference wheel speed and the steering angle detected by the steering angle sensor are used. And first target wheel speed calculating means for calculating the target wheel speeds of the other three wheels for correcting the behavior of the vehicle using the detected motion state quantity of the vehicle,
One of the four wheels is used as a reference wheel, and a wheel speed detected by a wheel speed sensor corresponding to the reference wheel is used as a reference wheel speed, and the reference wheel speed and the steering angle detected by the steering angle sensor are used. And among the other three wheels for correcting the behavior of the vehicle using the detected vehicle state of motion , one wheel on the opposite side to the reference wheel and the other side on the front and back side with respect to the reference wheel the target wheel speed of any one wheel of the two wheels with calculating respectively, the target wheel speed of the remaining one wheel from the sum of the target wheel speed of one wheel of the right and left opposite side of the reference wheel speed of Second target wheel speed calculating means for calculating a value obtained by subtracting the target wheel speed of one wheel on the opposite side of the front and rear ;
When the center differential is in the unlocked state, the target wheel speed of the other three wheels calculated by the first target wheel speed calculating means and the wheel speed detected by the wheel speed sensor corresponding to the other three wheels. using the wheel speeds of the wheels of the other three wheels are controlled to the braking device such that the target wheel speed of the other three wheels, which is the calculated, also when the center differential is locked, Using the target wheel speed of the other three wheels calculated by the second target wheel speed calculating means and the wheel speed detected by the wheel speed sensor corresponding to the other three wheels , the other three wheels. elevation of the vehicle wheel speed is characterized in that a brake control means for controlling the braking device such that the target wheel speed of the calculated the other three wheels of The control device. In the vehicle behavior control apparatus according to claim 1 ,
The reference wheel is a front wheel inside the turn,
The second target wheel speed calculating means is configured to adjust the vehicle behavior using the reference wheel speed , the steering angle detected by the steering angle sensor, and the detected motion state quantity of the vehicle. The target wheel speed of each of the two wheels is calculated, and the target wheel speed of the rear wheel inside the turn is calculated from the total value of the reference wheel speed and the target wheel speed of the front wheel outside the turn. A vehicle behavior control device that calculates a value obtained by subtracting the speed. In the vehicle behavior control device according to claim 1 or 2 ,
A reference wheel speed correcting means is provided which applies a predetermined restriction to an increase in wheel speed detected by a wheel speed sensor corresponding to the reference wheel and sets the restricted wheel speed as a reference wheel speed. A vehicle behavior control device. In the vehicle behavior control apparatus according to any one of claims 1 to 3 ,
The vehicle motion control device is a vehicle behavior control device in which the vehicle motion state quantities are vehicle longitudinal acceleration, lateral acceleration, and yaw rate. In the vehicle behavior control apparatus according to claim 1,
The first target wheel speed calculating means calculates a target slip ratio necessary for correcting the behavior of the vehicle corresponding to the other three wheels based on the detected motion state quantity of the vehicle, Calculating the target wheel speeds of the other three wheels for correcting the behavior of the vehicle using the wheel speed, the steering angle and the calculated target slip ratio,
The second target wheel speed calculation means includes one of the other three wheels for correcting the behavior of the vehicle, one wheel on the opposite side to the reference wheel and two on the opposite side to the reference wheel. A target slip ratio necessary for correcting the behavior of the vehicle corresponding to any one of the wheels is calculated based on the detected motion state quantity of the vehicle, and the reference wheel speed, the steering angle, and Using the calculated target slip ratio, the target wheel speed of any one of the one wheel on the opposite side to the reference wheel and the two wheels on the opposite side to the reference wheel is calculated. And calculating the target wheel speed of the remaining one wheel by subtracting the target wheel speed of the one wheel on the opposite side from the total value of the reference wheel speed and the target wheel speed of the one wheel on the opposite side. A vehicle behavior control device. In the vehicle behavior control apparatus according to claim 1,
The first target wheel speed calculating means calculates a reference speed of the vehicle at the center of gravity position of the vehicle based on the reference wheel speed, and uses the calculated reference speed of the vehicle, the steering angle, and the motion state quantity of the vehicle. Calculating the target wheel speeds of the other three wheels for correcting the behavior of the vehicle,
The second target wheel speed calculation means calculates a reference speed of the vehicle at the center of gravity position of the vehicle based on the reference speed, and uses the calculated reference speed of the vehicle, the steering angle, and the motion state quantity of the vehicle. Target wheel speed of any one of the other three wheels for correcting the behavior of the vehicle, one wheel on the opposite side to the reference wheel and two wheels on the opposite side to the reference wheel And the target wheel speed of the remaining one wheel is subtracted from the total value of the reference wheel speed and the target wheel speed of the one wheel on the opposite left and right sides. A vehicle behavior control device characterized by calculating a value.

Images