JP3959860B2 - Vehicle body slip angle estimation method and estimation apparatus - Google Patents

Description

ここで、Ｋ₁₁，Ｋ₂₁は誤差信号に対して線型なフィードバックを与えるゲイン、Ｋ₁₂，Ｋ₂₂は誤差の符号についてのみフィードバックを与えるゲインとなっている。これらのゲインの値は実験結果などから決定することができる。
【００３２】
そして、上記（７）式及び（８）式で推定された前後方向速度Ｖ＾_X 及び横方向速度Ｖ＾_Y を用いて、下記（９）式に従って最終的な横滑り角β＾を算出する。
【００３３】
β＾＝ｔａｎ^-1（Ｖ＾_Y ／Ｖ＾_X ） …………（９）
このように、上記第１の実施形態においては、車両状態量推定装置１０で、ヨーレイトセンサ１１で検出した実ヨーレートγ、前後加速度センサ１２で検出した前後加速度α_X ，横加速度センサ１３で検出した横加速度α_Y 、車輪速センサ１４で検出した車輪速Ｖｗ_FL〜Ｖｗ_RRに基づいて算出される前後方向速度Ｖ_X に基づいて前記（７）式および（８）式のオブザーバ演算を行うことにより、横方向速度Ｖ_Y に推定前後方向速度Ｖ＾_X と実際に検出した前後方向速度Ｖ_X との誤差信号をフィードバックして、推定横方向速度Ｖ＾_Y を算出し、これと推定前後方向速度Ｖ＾_X とに基づいて推定横滑り角β＾を算出することができる。
【００３４】
このとき、前記（７）式および（８）式で推定前後方向速度Ｖ＾_X と実際に検出した前後方向速度Ｖ_X との誤差信号をフィードバックするようにしているだけであり、非線型な運動を線型化してモデル化する必要がないので、低車速の急発進時などに車両の挙動が不安定になり車両に大きな横滑り角を発生してスピンしている状態においても、より正確な横滑り角の推定を行うことができる。
【００３５】
しかも、推定前後方向速度Ｖ＾_X と実際に検出した前後方向速度Ｖ_X との誤差信号をフィードバックするので、推定値が初期値を誤って与えた等の何らかの理由で真値から離れた場合にも真値に収束することになり、前述した第２従来例のように積分処理を利用した方式におけるドリフトの発生を確実に防止することができる。
【００３６】
次に、本発明の第２の実施形態を図３について説明する。
この第２の実施形態は、前後方向速度Ｖ_X を車輪速度又はその推定値から求めるようにしたものである。
【００３７】
すなわち、前輪又は後輪駆動車では非駆動輪が存在するために、駆動時において非駆動輪の車輪速を使用して前後方向速度を算出することが可能である。
一般に、低速時に大きな横滑り角が発生するのは、後輪駆動車などが急発進を行った場合が想定される。そのような状態では、前輪には駆動力等が発生していないために車輪速度は概略その位置でのタイヤの前後方向の車体速度と考えて差し支えない。このた、下記（１０）式を用いることで、車輪の回転速度より車輪位置での前後方向速度を得ることができる。
【００３８】
Ｖｗ_X ＝Ｖｗ・ｃｏｓδ …………（１０）
ここで、Ｖｗは車輪の回転速度を並進速度に換算したものであり、δは舵角（後輪では零又は４輪操舵システム登載時にはその舵角となる）、Ｖｗ_X はＶｗの車体の前後方向の成分であり、車輪のスリップが零の状態では車輪位置での車体の前後方向速度となる。
【００３９】
また、前記第１の実施形態における（７）および（８）式のオブザーバ演算で使用されるのは、重心位置での前後方向速度であるが、これは下記（１１）式を用いて重心位置での前後方向速度に変換することで算出することができる。
【００４０】
Ｖ_X ＝Ｖｗ_X ＋（−１）ⁱ ・γ・ｔｒ／２ …………（１１）
ここで、ｔｒはトレッド、ｉは車輪位置を表す添え字で奇数が左輪、偶数が右輪を夫々表す。
【００４１】
そして、前記（７）および（８）式のオブザーバ演算で必要な前後方向速度Ｖ_X として上記（１１）式を適用することにより、後輪駆動車が加速している場合の横滑り角β＾を算出することができる。
【００４２】
一方、制動時においては、車輪速の推定を行うために、車両の四輪の内の一輪の制動力を意図的に下げてスリップを抑制することにより、概略スリップがないときと同じと見なせることになり、前後方向速度Ｖｗ_X を算出することが可能となる。また、全ての車輪において制動力によって車輪のスリップが発生している状態でも、例えば車輪の回転運動のモデルを使用し、車輪速度を他の手段によりって推定することによって前記（７）および（８）式のオブザーバ演算で必要な前後方向速度Ｖ_X を算出することができる。ここで、タイヤの摩擦係数は摩擦係数推定手段によって与えられる。
【００４３】
このように加速状態および減速状態の何れの状態においても、車輪の回転を使用して、車輪位置若しくは重心位置での前後方向速度を求めることができる。
具体的には、図３に示すように、車両状態量推定装置１０に、前述したヨーレートセンサ１１、前後加速度センサ１２、横加速度センサ１３及び車輪速センサ１４に加えて、前輪１Ｆの操舵角を検出する操舵角センサ１５で検出した操舵角δ及びマスタシリンダ圧を検出するマスタシリンダ圧センサ１６で検出したマスタシリンダ圧ＭＰが入力されると共に、制動力制御装置３０からの制動力制御状態であるか否かを表す制動力制御状態信号ＳＢが入力され、且つこの車両状態量推定装置１０で、図４に示す状態量演算処理を実行することにより、車輪速度に基づいて推定横滑り角β＾を算出する。
【００４４】
この状態量演算処理は、所定時間（例えば１０ｍｓｅｃ）毎のタイマ割込処理によって実行され、先ずステップＳ１でマスタシリンダ圧センサ１６で検出したマスタシリンダ圧ＭＰを読込み、これが予め設定した比較的小さい１ＭＰａ程度の閾値ＭＰ_S 以上であるか否かを判定することにより、運転者がブレーキペダルを踏込んだ制動状態であるか否かを判定し、ＭＰ＜ＭＰ_S であるときには運転者による制動状態でないと判断して、ステップＳ２に移行し、制動力制御装置３０からの制動力制御状態信号ＳＢを読込んで、これがオン状態であるか否かを判定することにより、ブレーキペダルの踏込以外のトラクション制御又はヨーモーメント抑制制御による制動力制御が行われているか否かを判定し、制動力制御が行われていないときにはステップＳ３に移行して、非駆動輪となる前輪の左右何れか一方の車輪速度Ｖｗ_FL，Ｖｗ_FRを車輪速度Ｖｗとして設定してからステップＳ４に移行する。
【００４５】
このステップＳ４では、車輪速度Ｖｗをもとに前記（１０）式の演算を行って前後方向速度Ｖｗ_X を算出し、次いでステップＳ５に移行して、ヨーレートセンサ１１で検出したヨーレートγ(n) を読込んでからステップＳ６に移行する。
【００４６】
このステップＳ６では、前後方向速度Ｖｗ_X 及びヨーレートγ(n) をもとに前記（１１）式の演算を行って、重心位置での前後方向加速度Ｖ_X (n) を算出する。
【００４７】
次いで、ステップＳ７に移行して、重心位置での前後方向速度Ｖ_X (n) をもとに下記（１２）式及び（１３）式に従って車両の前後方向推定車体速度Ｖ＾_X (n) 及び横方向推定車体速度Ｖ＾_Y (n) を算出する。
【００４８】
Ｖ＾_X (n) ＝Ｖ＾_X (n) ＋Δｔ（−Ａ＋α_X (n) −Ｂ−Ｃ） ……（１２）
Ｖ＾_Y (n) ＝Ｖ＾_Y (n) ＋Δｔ（Ｄ＋α_Y (n) −Ｅ−Ｆ） ……（１２）
Ａ＝Ｖ＾_Y (n-1) γ(n-1)
Ｂ＝Ｋ₁₁（Ｖ＾_X (n-1) −Ｖ_X (n) ）
Ｃ＝Ｋ₁₂sign（Ｖ＾_X (n-1) −Ｖ_X (n) ）
Ｄ＝Ｖ＾_X (n-1) γ(n-1)
Ｅ＝Ｋ₂₁（Ｖ＾_X (n-1) −Ｖ_X (n) ）
Ｆ＝Ｋ₂₂sign（Ｖ＾_X (n-1) −Ｖ_X (n) ）
次いで、ステップＳ８に移行して、車両の前後方向推定車体速度Ｖ＾_X (n) 及び横方向推定車体速度Ｖ＾_Y (n) をもとに、前記（９）式に従って推定横滑り角β＾(n) を算出し、次いでステップＳ９に移行して、算出した車両の前後方向推定車体速度Ｖ＾_X (n) 及び横方向推定車体速度Ｖ＾_Y (n) を前回値Ｖ＾_X (n-1) 及びＶ＾_Y (n-1) として記憶してからタイマ割込処理を終了して所定のメインプログラムに復帰する。
【００４９】
一方、ステップＳ１の判定結果が、運転者がブレーキペダルを踏込んでいる制動状態であるときには、ステップＳ１０に移行して、例えばアンチロックブレーキ制御装置で使用する推定車体速度を参照して、これを車輪速度Ｖｗとして設定してから前記ステップＳ４に移行する。
【００５０】
また、ステップＳ２の判定結果が、車両が制動力制御を行っているときには、ステップＳ１１に移行して、非駆動輪に制動制御力を解除可能な車輪があるか否かを判定し、解除可能な車輪があるときにはステップＳ１２に移行して、該当車輪の制御力を解除してから該当車輪の車輪速を車輪速度Ｖｗとして設定してから前記ステップＳ４に移行し、解除可能な車輪がないときには前記ステップＳ１０に移行する。
【００５１】
この図４の横滑り角演算処理において、ステップＳ１〜Ｓ６の処理前後方向速度算出手段に対応し、ステップＳ７の処理が速度推定手段に対応し、ステップＳ８の処理が横滑り角算出手段に対応している。
【００５２】
したがって、運転者がブレーキペダルを踏込んでおらず、トラクション制御やヨーレート制御等の制動力制御が行われていないときには、非駆動輪となる前輪１Ｆの左右輪の何れか一方の車輪速Ｖｗ_FL又はＶｗ_FRに基づいて重心位置における前後方向速度Ｖ_X (n) を算出し、これと前回の推定前後方向速度Ｖ＾_X (n-1) 及び推定横方向速度Ｖ＾_Y (n-1) と、前後加速度α_X 及び横加速度α_Y に基づくオブザーバ演算によって推定前後方向速度Ｖ＾_X (n) 及び推定横方向速度Ｖ＾_Y (n) を算出し、これらに応じて推定横滑り角β＾(n) を算出する。
【００５３】
一方、運転者が制動操作を行っていないが、トラクション制御やヨーレート制御が行われている場合には、トラクション制御では非駆動輪となる前輪では制動力制御されていないので、これらの何れかの車輪速が選択され、ヨーレート制御では内輪側又は外輪側の何れかの車輪が制動力制御されないので、この車輪が選択されて、これらに基づいて重心位置における前後方向速度Ｖ_X (n) を算出する。
【００５４】
また、運転者が制動操作を行っている場合や制動操作を行っていないがトラクション制御やヨーレート制御によって全ての車輪が制動力制御されている場合には、例えばアンチロックブレーキ制御での推定車体速度に基づいて重心位置における前後方向速度を算出する。
【００５５】
この結果、車両の制動状態に応じてそのときの前後方向速度を的確に表す車輪速を選択して、これに基づいて重心位置おける前後方向速度を算出することができ、高精度で横滑り角を推定することができる。
【００５６】
なお、上記第２の実施形態においては、運転者の制動操作をマスタシリンダ圧センサ１６でマスタシリンダ圧を検出することにより検出する場合について説明したが、これに限定されるものではなく、ブレーキペダルの踏込み時にオンとなるブレーキランプスイッチのスイッチ信号等によって検出するようにしてもよい。
【００５７】
次に、本発明の第３の実施形態を図５について説明する。
この第３の実施形態は、前述した第１及び第２の実施形態においては、推定横滑り角を算出する際に、操舵角δを使用していないので、低車速域での前後方向加速度α_X に対して横方向加速度α_Y が大きい状態では高精度で横滑り角を推定することができるが、それ以外の高車速域では、推定精度が低下することになるため、高車速域では他の推定方法に切換えることにより、全ての車速域で高精度の横滑り角推定を行うことができるようにしたものである。
【００５８】
すなわち、車両状態量推定装置１０で、図５に示す推定方法切換処理を実行する。
この推定方法切換処理は、所定時間（例えば１０ｍｓｅｃ）毎のタイマ割込処理として実行され、先ず、ステップＳ２１で、前回使用した推定方法が前述した第１従来例と同様の運動モデルを使用した高速用横滑り角推定方法であったか否かを判定し、高速用横滑り角推定方法であったときには、ステップＳ２２に移行して、駆動輪としての後輪１Ｒの左右輪のうちの高い車輪速Ｖｗ_RHから非駆動輪としての前輪１Ｆの左右輪のうちの高い車輪速Ｖｗ_FHを減算した値（Ｖｗ_RH−Ｖｗ_FH）が予め設定した設定値ΔＶｗ₁ より大きく且つ非駆動輪としての前輪１Ｆの高い車輪速Ｖｗ_FHが予め設定した設定車速Ｖｗ_S1より小さいか否かを判定し、（Ｖｗ_RH−Ｖｗ_FH）＞ΔＶｗ₁ 且つＶｗ_FH＜Ｖｗ_S1であるときには、低車速域での駆動輪スピン状態であると判断して、ステップＳ２３に移行する。
【００５９】
このステップＳ２３では、前述した第１の実施形態又は第２の実施形態による前後方向速度Ｖ_X (n) と推定前後方向速度Ｖ＾_X (n) との誤差信号をフィードバックすることにより、推定前後方向速度Ｖ＾_X (n) 及び推定横方向速度Ｖ＾_Y (n) を算出し、これらから推定横滑り角β＾(n) を算出する横滑り角推定方法を使用する低速用横滑り角推定方法によって推定横滑り角β＾(n) を算出してからステップＳ２４に移行する。
【００６０】
このステップＳ２４では、後述する高車速用横滑り角推定方法で推定ヨーレートγ＾(n) を使用するので、ヨーレートセンサ１１で検出した実ヨーレートγ(n) を推定ヨーレートγ＾(n) として記憶してからステップＳ２５に移行して、今回の推定結果（γ(n) 、β(n) 、Ｖ_X (n) 、Ｖ_Y (n) ）を前回値として記憶すると共に、使用した横滑り推定方法に応じた種別を表すフラグＦを設定してからタイマ割込処理を終了して所定のメインプログラムに復帰する。
【００６１】
一方、ステップＳ２２の判定結果が設定条件を満足しないときには、ステップＳ２６に移行して、高速用横滑り角推定方法によって推定横滑り角β＾(n) を算出し、次いでステップＳ２７に移行して、ステップＳ２３での低速用横滑り角推定方法で使用する推定前後方向速度Ｖ＾_X として車速Ｖ(n) を設定すると共に、下記（１３）式に従って推定横方向速度Ｖ＾_Y (n) を算出してから前記ステップＳ２５に移行する。
【００６２】
Ｖ＾_X (n) ＝Ｖ(n) ＊ｔａｎ（β＾(n) ） …………（１３）
また、ステップＳ２１の判定結果が前回の推定方法が低速用横滑り角推定方法であるときには、ステップＳ２８に移行して、前記ステップＳ２２と同様に駆動輪としての後輪１Ｒの左右輪のうちの高い車輪速Ｖｗ_RHから非駆動輪としての前輪１Ｆの左右輪のうちの高い車輪速Ｖｗ_FHを減算した値（Ｖｗ_RH−Ｖｗ_FH）が予め設定した前記設定値ΔＶｗ₁ より大きい設定値ΔＶｗ₂ より大きく且つ非駆動輪としての前輪１Ｆの高い車輪速Ｖｗ_FHが予め設定した前記設定車速Ｖｗ_S1よ大きい設定車速Ｖｗ_S2より大きいか否かを判定し、（Ｖｗ_RH−Ｖｗ_FH）＞ΔＶｗ₁ 且つＶｗ_FH＞Ｖｗ_S2であるときには、高車速域であるか駆動輪にホイールスピンを生じていないものと判断して前記ステップＳ２６に移行し、そうでないときには駆動輪にホイールスピンを生じているものと判断して前記ステップＳ２３に移行する。
【００６３】
また、ステップＳ２６での高速用横滑り角推定方法は、前述した図２の２輪運動モデルから前輪のタイヤの横滑り角β_f 及び後輪のタイヤの横滑り角β_r は、下記（１４）式及び（１５）式で表すことができる。
【００６４】
β_f ＝ｔａｎ^-1｛（Ｖ_Y −Ｌ_f γ）／Ｖ_X ｝＋δ …………（１４）
β_r ＝ｔａｎ^-1｛（Ｖ_Y −Ｌ_r γ）／Ｖ_X ｝ …………（１５）
さらに、車速Ｖ_X がある程度大きい状態では線形化が可能であり、下記（１６）式で表される車体横滑り角βと車体前後方向速度Ｖ_X 及び横方向速度Ｖ_Y との関係を用い、前記（１４）式及び（１５）式に代えて下記（１７）式及び（１８）式の関係が得られ、以上より最終的に下記（１９）式及び（２０）式の線形２輪モデルが得られる。
【００６５】

この線形２輪モデルは制御設計を行うために下記（２１）〜（２８）の状態空間で表現できる。
【００６６】
【数１】

【００６７】
そして、上記（２１）式及び（２２）式の車両モデルに対し、オブザーバは下記（３０）式ように設計される。
ｘ＾′＝Ａｘ＾＋Ｂｕ＋Ｌｙ〜 …………（３０）
ここで、Ａ，Ｂ，Ｃ，Ｄは車両の運動を計算するための行列である。ｘ＾は、推定された状態量、Ｌは状態推定量の補正量を決定するゲインである。ここで、誤差信号ｙ〜は、下記（３１）式によって求められ、推定状態量ｘ＾は下記（３２）式で求められる。
【００６８】
ｙ〜＝ｙ−（Ｃｘ＾＋Ｄｕ） …………（３１）
【００６９】
【数２】

【００７０】
したがって、図６におけるステップＳ３１で前記（２５）式〜（２８）式の行列Ａ〜Ｄを計算し、次いでステップＳ３２に移行して、前記（２９）式及び（３０）式を使用して推定ヨーレートγ＾及び推定横滑り量β＾を算出し、次いでステップＳ３３に移行して、算出した推定ヨーレートγ＾及び推定横滑り量β＾を前回値として記憶してから処理を終了する。
【００７１】
この第３の実施形態によると、車両の発進時等の低車速域で駆動輪となる後輪にホイールスピンを生じる状態となると、前回の処理時に高速用横滑り角推定方法が選択されているものとしても、ステップＳ２２からステップＳ２３に移行して、第１又は第２の実施形態による前後方向速度Ｖ_X (n) と推定前後方向速度Ｖ＾_X (n) との誤差信号をフィードバックすることにより、推定前後方向速度Ｖ＾_X (n) 及び推定横方向速度Ｖ＾_Y (n) を算出し、これらから推定横滑り角β＾(n) を算出する横滑り角推定方法を使用する低速用横滑り角推定方法によって推定横滑り角β＾(n) を算出するので、高精度で推定横滑り角β＾を算出することができる。
【００７２】
この状態から、駆動輪としての後輪のホイールスピンが収まるか、車速が速くなると、ステップＳ２８での判定条件を満足しなくなると、ステップＳ２６に移行して、図８に示す高速用横滑り角推定処理が実行されるので、高車速域で高精度の横滑り角推定を行うことができる。
【００７３】
なお、上記第３の実施形態においては、高速用横滑り推定方法として、（２５）式〜（３１）式を使用して推定ヨーレートγ＾及び推定横滑り角β＾を算出する場合について説明したが、これに限定されるものではなく、前述した第１従来例や第２従来例のような他の横滑り角推定方法を適用することができる。
【図面の簡単な説明】
【図１】本発明の第１の実施形態の全体構成を示すブロック図である。
【図２】２輪運動モデルを示す説明図である。
【図３】本発明の第２の実施形態の全体構成を示すブロック図である。
【図４】第２の実施の形態における演算処理の概要を示すフローチャートである。
【図５】本発明の第３の実施形態における演算処理の概要を示すフローチャートである。
【図６】第３の実施形態における高速用横滑り角演算処理の一例を示すフローチャートである。
【符号の説明】
１０ 車両状態量推定装置
１１ ヨーレートセンサ
１２ 前後加速度センサ
１３ 横加速度センサ
１４ 車輪速センサ
１５ 操舵角センサ
１６ マスタシリンダ圧センサ
２０ 目標制動力設定装置
３０ 制動力制御装置[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicle body slip angle estimation method and an estimation device for a vehicle, and in particular, aims to improve estimation accuracy of a vehicle body slip angle in a low vehicle speed range.
[0002]
[Prior art]
As this type of conventional technology, for example, those disclosed in Japanese Patent Application Laid-Open No. 8-268306 (hereinafter referred to as a first conventional example) and Japanese Patent Application Laid-Open No. 8-332934 (hereinafter referred to as a second conventional example). It has been known.
[0003]
The first conventional example calculates the estimated side slip angle based on the estimated side slip angle and the estimated yaw rate calculated based on the observer's equation of state and the detected longitudinal velocity, while calculating the ratio between the detected lateral acceleration and the calculated estimated side acceleration. It is calculated as a correction coefficient, and the correction coefficient is multiplied by a factor related to the cornering power in the observer's equation of state. By this means, if the skid angle is estimated based on the observer's equation of state, the cornering power is accurately corrected. Therefore, the estimation accuracy of the skid angle is improved.
[0004]
In addition, the second conventional example includes a skid physical quantity calculation block for calculating a vehicle skid physical quantity by integral calculation using vehicle speed, yaw rate, and lateral acceleration as parameters, and a vehicle model using a detected vehicle state quantity as an input variable. Side slip physical quantity estimation block that estimates the side slip amount of the vehicle and an integral time constant setting block that increases the integration time constant of the integral calculation when the turning behavior of the vehicle is unstable, and the side slip physical quantity calculated by the side slip physical quantity calculation block And the side slip physical quantity of the vehicle is finally calculated by the final calculation block based on the side slip physical quantity estimated by the side slip physical quantity estimation block.
[0005]
[Problems to be solved by the invention]
Here, tire lateral force and cornering force generally have non-linear characteristics in a region where the tire slip angle is large, so when estimating the vehicle body side slip angle using an estimation formula based on a tire model, It has been found that the estimation accuracy of the vehicle body side slip angle is lowered in a region where the tire characteristics (relation between the tire side slip angle and the cornering force) are nonlinear.
[0006]
Therefore, for example, as in the first conventional example, the vehicle body side slip angle is estimated by correcting the cornering power included in the estimation formula by using a correction coefficient corresponding to the ratio between the detected lateral acceleration and the estimated lateral acceleration. It can be considered that the accuracy is not lowered. However, even with such a method using correction factors, a vehicle turning motion model that uses vehicle body mass, vehicle body yawing moment of inertia, horizontal distance from the center of gravity of the vehicle to the front and rear axles, vehicle longitudinal speed, cornering power, etc. is used. Therefore, since the approximation formula is not effective in the region where the vehicle speed is low, there is an unsolved problem that the accuracy of the side slip angle is deteriorated. In particular, there is a high possibility that the side slip angle will increase even when driving at low speeds, including the phenomenon called so-called power oversteer due to the driving force immediately after the start of the car that drives the rear wheels. It is desired to estimate.
[0007]
In addition, as in the second conventional example, when calculating the vehicle slip physical quantity by integral calculation using the vehicle speed, the yaw rate, and the lateral acceleration as parameters, the estimation accuracy in the low vehicle speed range as in the first conventional example is described. However, there is a possibility that the drift of the estimated value deviates from the true value due to the difference in the dynamic characteristics between the sensors and the integration error because the integration process is used. However, there is an unsolved problem that it is necessary to use in combination with a method using a vehicle model.
[0008]
Accordingly, the present invention has been made paying attention to the unsolved problems of the above-described conventional example, and provides a skid angle estimation method and an estimation device capable of improving the estimation accuracy of the body slip angle in a low vehicle speed range. The purpose is to do.
[0009]
[Means for solving the problems]
  In order to achieve the above object, a vehicle body side slip angle estimating method according to claim 1 includes:When the value of the wheel speed of the rear wheel that is the driving wheel is larger than a certain value or a certain ratio with respect to that of the front wheel that is the non-driving wheel, and the wheel speed or the vehicle speed of the front wheel is smaller than a certain value In addition,In addition to detecting the longitudinal speed and yaw rate of the vehicle, the longitudinal acceleration and lateral acceleration of the vehicle are detected, and the vehicle is moving around the vertical axis in the longitudinal and lateral directions of the vehicle, respectively. The front-rear direction velocity, yaw rate, front-rear direction acceleration and lateral acceleration detected in the motion model to be used are known amounts, the estimated front-rear direction velocity and estimated lateral direction velocity are unknown amounts, and the errors in the front-rear direction velocity and the estimated front-rear direction velocity are Is used as a feedback signal to calculate the estimated longitudinal speed and estimated lateral speed, and the side slip angle of the vehicle body is estimated based on the estimated estimated longitudinal speed and estimated lateral speed.Use low-speed vehicle side slip angle estimation method, otherwise use other high-speed vehicle side slip angle estimation methodIt is characterized by doing so.
[0011]
  And claims2The vehicle side slip angle estimating method for a vehicle according to claim 1 is characterized in that, in the invention according to claim 1, the front-rear direction speed uses one of a wheel speed and an estimated value of the wheel speed.
[0013]
  Still further, the claims3The vehicle body side slip angle estimating apparatus according to the invention detects wheel speed calculating means for calculating the wheel speed of each wheel of the vehicle, yaw rate detecting means for detecting the yaw rate generated in the vehicle body, and detecting longitudinal acceleration generated in the vehicle body. Longitudinal acceleration detection means, lateral acceleration detection means for detecting lateral acceleration generated in the vehicle body, longitudinal speed based on the wheel speed detected by the wheel speed calculation means and the yaw rate detected by the yaw rate detection means The longitudinal speed calculation means for calculating the longitudinal speed, the yaw rate, the longitudinal acceleration detected in the motion model describing the state in which the vehicle is moving around the vertical axis for the longitudinal direction and the lateral direction of the vehicle, respectively. And the lateral acceleration as a known quantity, the estimated longitudinal speed and the estimated lateral speed as unknown quantities, and the longitudinal speed calculation means Speed estimation means for estimating the longitudinal and lateral speeds by performing an observer operation that feeds back an error signal between the generated longitudinal speed and the estimated longitudinal speed; and the longitudinal and lateral speeds estimated by the speed estimation means A skid angle calculating means for calculating a skid angle based onFor low speedBody slip angle estimation device andA high-speed vehicle body side slip estimation device having a configuration different from that of the low-speed vehicle body side slip angle estimation device, and the larger value of the wheel speed of the rear wheel serving as the drive wheel is that of the front wheel serving as the non-drive wheel. The low-speed vehicle body side slip angle estimating device is selected when the front wheel speed or the vehicle body speed is smaller than a certain value, and in other cases, the high-speed vehicle body side slip is selected. The feature is that the angle estimator is selected.is doing.
[0014]
【The invention's effect】
  According to the first aspect of the present invention, the larger value of the wheel speed of the rear wheel that is the driving wheel is larger than a certain value or a certain ratio with respect to that of the front wheel that is the non-driving wheel, and the wheel speed of the front wheel is larger. Or when the vehicle speed is below a certain value,Motion model describing forward and backward motionThe front-rear direction speed, yaw rate, front-rear direction acceleration and lateral acceleration detected in step 4 are known amounts, the estimated front-rear direction velocity and estimated lateral direction rate are unknown amounts, and the errors in the front-rear direction velocity and the estimated front-rear direction velocity areAs a feedback signalObserver calculation is performed to calculate the estimated longitudinal speed and estimated lateral speed, and the side slip angle of the vehicle body is estimated based on the estimated estimated longitudinal speed and estimated lateral speed.Therefore, it is possible to estimate the sideslip angle with high accuracy in the low vehicle speed range, and to converge to the true value even if the estimated value leaves the true value for some reason such as giving an initial value by mistake. Drift does not occur unlike the second conventional example described above,By switching to other estimation methods at medium and high vehicle speeds, high-precision skid angle estimation is continued, and skid angles are accurately estimated at all vehicle speeds.The effect that it can do is acquired.
[0015]
  Also,Detect longitudinal speedTherefore, it is possible to perform an accurate measurement and to obtain an effect that a more accurate side slip angle can be estimated.
[0016]
  And claims2According to the invention according to the present invention, since the longitudinal speed is calculated using either the wheel speed or the estimated value of the wheel speed, it can be calculated as a value according to the actual traveling state of the vehicle. The effect that the side slip angle can be accurately estimated is obtained.
[0018]
  Still further, the claims3According to the invention according to claim 1, similarly to the invention according to claim 1, in the low vehicle speed range.Is a vehicle body slip angle estimation device for low speed,It is possible to estimate the sideslip angle with high accuracy and to converge to the true value even when the estimated value leaves the true value for some reason such as giving an initial value by mistake. Drift does not occur as in the conventional example, and in the middle and high vehicle speed range, the high-speed vehicle body side slip angle estimation device can estimate the side slip angle with high accuracy.Predicts skid angle with high accuracy in the vehicle speed rangeThe effect that it can do is acquired.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing the overall configuration of a first embodiment of the present invention. A vehicle in the present embodiment includes a vehicle state quantity estimating device 10 that estimates a state quantity such as a vehicle body side slip angle, and a target control. A power setting device 20 and a braking force control device 30 are provided. The target braking force setting device 20 is a device for setting an appropriate braking force based on each value supplied from the vehicle body side slip angle estimating device 10, and its specific configuration is executed control. (For example, control applicable to a vehicle such as VDC, ABS, TCS, etc.) is appropriately determined, but since the contents are not the essence of the present invention, the specific description thereof is omitted. . Also, since the braking force control device 30 can adopt a known configuration as appropriate according to the control to be executed, a specific description thereof is also omitted.
[0020]
The vehicle state quantity estimation device 10 is actually constituted by a microcomputer, a necessary interface circuit, and the like, and an actual yaw rate r supplied from a yaw rate sensor 11 for detecting the yaw rate generated in the vehicle, and generated in the vehicle. The longitudinal acceleration α supplied from the longitudinal acceleration sensor 12 for detecting the longitudinal acceleration_XAnd the lateral acceleration α supplied from the lateral acceleration sensor 13 for detecting the lateral acceleration generated in the vehicle._YAnd the wheel speed Vw supplied from the wheel speed sensor 14 that detects the wheel speed of each wheel._FL~ Vw_RRBased on the above, a predetermined calculation process is executed to estimate the side slip angle β of the vehicle body.
[0021]
That is, a general two-wheel motion model that describes a state in which the vehicle is moving around the vertical axis in the longitudinal direction and the lateral direction of the vehicle includes a front wheel 1F having a steering mechanism and a steering mechanism as shown in FIG. The rear wheel 1R has no front wheel, the front wheel steering angle is δ, the front wheel side slip angle is β_f, Rear wheel skid angle β_r, V is the vehicle speed at the center of gravity 2 and V is the longitudinal speed._X, The lateral speed is V_Y, Α is the longitudinal acceleration_X, The lateral acceleration α_Y, Where γ is the yaw rate, β is the side slip angle, and the horizontal distance from the center of gravity to the front axle is L_f, The horizontal distance from the center of gravity to the rear wheel axle_r, The equation of motion is that the mass of the vehicle is M and the rotational moment of inertia of the vehicle in the yaw direction is I._Z, CP for tire cornering power of front and rear wheels_f, CP_rThen, it can be expressed by the following formulas (1) and (2).
[0022]
MV_X(Β '+ γ) = 2CP_fβ_f+ 2CP_rβ_r  ………… (1)
I_Zγ '= 2L_fCP_fβ_f-2L_fCP_fβ_f    ………… (2)
In order to accurately describe the motion with a large side slip angle, the longitudinal acceleration α of the vehicle is determined from the motion model of FIG._XLateral acceleration α_YAnd longitudinal speed V_XAnd lateral velocity V_YCan be expressed by the following equations (3) and (4).
[0023]
α_X= V_X'+ V_Yγ (3)
α_Y= V_Y'-V_xγ (4)
Where V_X′ Is the longitudinal speed V_XDifferential value of V_Y′ Is a differential value of the lateral speed.
[0024]
  Above (3)formulaIf the vehicle is decelerating, if the vehicle has a lateral velocity component and yaw at the center of gravity,-That the detected value of the longitudinal acceleration sensor does not match the differential value of the longitudinal acceleration.
[0025]
In addition, the above equation (4) indicates that the vehicle's lateral speed V_YDifferential value V_Y'And the detected value of the lateral acceleration sensor do not match.
[0026]
As can be seen from these equations (3) and (4), in the state where the yaw rate is generated in the vehicle, the movement of the vehicle in the front-rear direction and the lateral direction is closely related via the yaw rate.
[0027]
  Also, the longitudinal speed V_XIs the lateral speed V_YHowever, it is necessary to model the movement of the vehicle in consideration of the situation. Therefore, among the variables used in the above equations (3) and (4), the physical quantity that can be directly measured by the sensor in the vehicle is the yaw rate γ.,in frontreardirectionAcceleration α and lateral acceleration α_YIt is.
[0028]
Also, the vehicle's longitudinal speed V_XCan be measured or estimated relatively easily based on the speed of the wheel or the like. Furthermore, the above formulas (3) and (4) are used to express the longitudinal acceleration α_XAnd lateral acceleration α_yAnd longitudinal speed V_XAnd lateral velocity V_YAt the same time, the longitudinal velocity V_XAnd lateral velocity V_YIt can be considered as an equation of motion represented by the following equations (5) and (6), where is a state quantity.
[0029]
V_X'= -V_Yγ + α_X    ............ (5)
V_Y'= V_Xγ + α_Y      ………… (6)
Therefore, it is possible to describe the motion of the vehicle by directly using the equations (5) and (6).
[0030]
  Therefore, the longitudinal speed V based on the above formulas (5) and (6)._XUsing the error signal as a known quantity,Every timeV_YBy setting an observer for estimating the side slip angle, it is possible to obtain the side slip angle with high accuracy even in a region where the side slip angle is large.
[0031]
Here, since the equations (5) and (6) are non-linear motion equations, the observers shown in the following equations (7) and (8) are used.

Where K₁₁, K_{twenty one}Is the gain that gives linear feedback to the error signal, K₁₂, K_{twenty two}Is a gain that provides feedback only for the sign of the error. These gain values can be determined from experimental results.
[0032]
And the longitudinal speed V ^ estimated by the above equations (7) and (8)_XAnd lateral velocity V ^_YIs used to calculate the final skid angle β ^ according to the following equation (9).
[0033]
β ^ = tan^-1(V ^_Y/ V ^_X) ………… (9)
As described above, in the first embodiment, the vehicle state quantity estimating apparatus 10 uses the actual yaw rate γ detected by the yaw rate sensor 11 and the longitudinal acceleration α detected by the longitudinal acceleration sensor 12._X, Lateral acceleration α detected by the lateral acceleration sensor 13_YThe wheel speed Vw detected by the wheel speed sensor 14_FL~ Vw_RRThe longitudinal speed V calculated based on_XBy performing the observer calculation of the equations (7) and (8) based on the_YEstimated longitudinal speed V ^_XAnd the longitudinal velocity V actually detected_XThe error signal is fed back and the estimated lateral speed V ^_YAnd the estimated longitudinal speed V ^_XBased on the above, the estimated side slip angle β ^ can be calculated.
[0034]
At this time, the estimated longitudinal speed V ^ in the equations (7) and (8)_XAnd the longitudinal velocity V actually detected_XError signal is fed back and there is no need to model non-linear motion linearly, so the behavior of the vehicle becomes unstable when suddenly starting at a low vehicle speed, etc. Even in a state where a side slip angle is generated and spinning, a more accurate side slip angle can be estimated.
[0035]
Moreover, the estimated longitudinal speed V ^_XAnd the longitudinal velocity V actually detected_XThe error signal is fed back to the true value even if the estimated value deviates from the true value for some reason, such as when the initial value is given incorrectly, as in the second conventional example described above. It is possible to reliably prevent the occurrence of drift in the method using the integration process.
[0036]
Next, a second embodiment of the present invention will be described with reference to FIG.
This second embodiment has a longitudinal speed V_XIs obtained from the wheel speed or its estimated value.
[0037]
That is, since there are non-driven wheels in the front-wheel or rear-wheel drive vehicle, it is possible to calculate the longitudinal speed using the wheel speed of the non-driven wheels during driving.
In general, it is assumed that a large skid angle occurs at a low speed when a rear wheel drive vehicle or the like makes a sudden start. In such a state, since no driving force or the like is generated on the front wheels, the wheel speed can be considered as the vehicle body speed in the front-rear direction of the tire at that position. Therefore, by using the following equation (10), the front-rear direction speed at the wheel position can be obtained from the rotational speed of the wheel.
[0038]
Vw_X= Vw · cos δ (10)
Here, Vw is a value obtained by converting the rotational speed of the wheel into a translational speed, and δ is a steering angle (zero at the rear wheel or the steering angle when the four-wheel steering system is installed), Vw_XIs a front-rear direction component of the vehicle body of Vw. When the wheel slip is zero, the vehicle body front-rear speed at the wheel position is obtained.
[0039]
Also, what is used in the observer calculation of the equations (7) and (8) in the first embodiment is the longitudinal speed at the center of gravity position, which is expressed by the following equation (11). It can be calculated by converting to the longitudinal speed at.
[0040]
V_X= Vw_X+ (-1)ⁱ・ Γ ・ tr / 2 (11)
Here, tr is a tread, i is a subscript representing a wheel position, and an odd number represents a left wheel and an even number represents a right wheel.
[0041]
Then, the longitudinal speed V required for the observer calculation of the equations (7) and (8)_XBy applying the above equation (11), the side slip angle β ^ when the rear wheel drive vehicle is accelerating can be calculated.
[0042]
On the other hand, at the time of braking, in order to estimate the wheel speed, the braking force of one of the four wheels of the vehicle is intentionally lowered to suppress the slip, so that it can be regarded as the same as when there is almost no slip , The longitudinal speed Vw_XCan be calculated. Further, even in a state where the wheels slip due to the braking force in all the wheels, for example, by using a model of the rotational motion of the wheels and estimating the wheel speed by other means, the above (7) and ( 8) V-direction velocity required for observer calculation_XCan be calculated. Here, the friction coefficient of the tire is given by the friction coefficient estimating means.
[0043]
As described above, in any of the acceleration state and the deceleration state, the front-rear direction speed at the wheel position or the center of gravity position can be obtained by using the rotation of the wheel.
Specifically, as shown in FIG. 3, in addition to the yaw rate sensor 11, the longitudinal acceleration sensor 12, the lateral acceleration sensor 13, and the wheel speed sensor 14 described above, the steering angle of the front wheel 1 </ b> F is added to the vehicle state quantity estimation device 10. The steering angle δ detected by the steering angle sensor 15 to be detected and the master cylinder pressure MP detected by the master cylinder pressure sensor 16 for detecting the master cylinder pressure are inputted, and the braking force control state from the braking force control device 30 is entered. The braking force control state signal SB indicating whether or not the vehicle is input, and the vehicle state quantity estimation device 10 executes the state quantity calculation process shown in FIG. 4 to obtain the estimated skid angle β ^ based on the wheel speed. calculate.
[0044]
This state quantity calculation process is executed by a timer interrupt process every predetermined time (for example, 10 msec). First, in step S1, the master cylinder pressure MP detected by the master cylinder pressure sensor 16 is read, and this is set to a relatively small 1 MPa. Threshold MP_SBy determining whether or not it is above, it is determined whether or not the driver is in a braking state in which the brake pedal is depressed, and MP <MP_SWhen it is determined that the braking state is not set by the driver, the process proceeds to step S2 and the braking force control state signal SB from the braking force control device 30 is read to determine whether or not the braking state is on. Then, it is determined whether or not braking force control by traction control other than depression of the brake pedal or yaw moment suppression control is performed. When the braking force control is not performed, the process proceeds to step S3 and becomes a non-driven wheel. Wheel speed Vw on either the left or right side of the front wheel_FL, Vw_FRIs set as the wheel speed Vw, and then the process proceeds to step S4.
[0045]
In this step S4, the calculation of the above equation (10) is performed based on the wheel speed Vw, and the longitudinal speed Vw is calculated._XThen, the process proceeds to step S5, the yaw rate γ (n) detected by the yaw rate sensor 11 is read, and then the process proceeds to step S6.
[0046]
In this step S6, the longitudinal speed Vw_XAnd the yaw rate γ (n) based on the above equation (11), the longitudinal acceleration V at the center of gravity is calculated._X(n) is calculated.
[0047]
Next, the process proceeds to step S7, and the longitudinal speed V at the position of the center of gravity._XBased on (n), the estimated vehicle body speed V ^ in the longitudinal direction of the vehicle according to the following equations (12) and (13)_X(n) and lateral estimated vehicle speed V ^_Y(n) is calculated.
[0048]
V ^_X(n) = V ^_X(n) + Δt (−A + α_X(n) -BC) (12)
V ^_Y(n) = V ^_Y(n) + Δt (D + α_Y(n) -EF) (12)
A = V ^_Y(n-1) γ (n-1)
B = K₁₁(V ^_X(n-1) -V_X(n))
C = K₁₂sign (V ^_X(n-1) -V_X(n))
D = V ^_X(n-1) γ (n-1)
E = K_{twenty one}(V ^_X(n-1) -V_X(n))
F = K_{twenty two}sign (V ^_X(n-1) -V_X(n))
Next, the process proceeds to step S8, where the estimated vehicle body speed V ^_X(n) and lateral estimated vehicle speed V ^_YBased on (n), an estimated side slip angle β ^ (n) is calculated according to the above equation (9), and then the process proceeds to step S9, where the calculated vehicle longitudinal estimated vehicle speed V ^_X(n) and lateral estimated vehicle speed V ^_Y(n) is the previous value V ^_X(n-1) and V ^_YAfter being stored as (n-1), the timer interrupt process is terminated and the process returns to the predetermined main program.
[0049]
On the other hand, when the determination result in step S1 is a braking state in which the driver is stepping on the brake pedal, the process proceeds to step S10, and this is referred to, for example, by referring to the estimated vehicle body speed used in the antilock brake control device. After the wheel speed Vw is set, the process proceeds to step S4.
[0050]
Moreover, when the determination result of step S2 is that the vehicle is performing the braking force control, the process proceeds to step S11, where it is determined whether there is a wheel that can release the braking control force in the non-driven wheels, and the release is possible. When there is a correct wheel, the process proceeds to step S12. After the control force of the corresponding wheel is released, the wheel speed of the corresponding wheel is set as the wheel speed Vw, and then the process proceeds to step S4. The process proceeds to step S10.
[0051]
In the skid angle calculation process of FIG. 4, the process front-rear direction speed calculation means in steps S1 to S6 corresponds to the process S7, the process in step S7 corresponds to the speed estimation means, and the process in step S8 corresponds to the skid angle calculation means. Yes.
[0052]
Therefore, when the driver does not step on the brake pedal and braking force control such as traction control or yaw rate control is not performed, the wheel speed Vw of any one of the left and right wheels of the front wheel 1F that is a non-driven wheel._FLOr Vw_FRThe longitudinal velocity V at the center of gravity based on_X(n) is calculated, and this and the previous estimated longitudinal speed V ^_X(n-1) and estimated lateral velocity V ^_Y(n-1) and longitudinal acceleration α_XAnd lateral acceleration α_YEstimated longitudinal velocity V ^ by observer calculation based on_X(n) and estimated lateral velocity V ^_Y(n) is calculated, and the estimated sideslip angle β ^ (n) is calculated according to these.
[0053]
On the other hand, when the driver does not perform the braking operation but the traction control or the yaw rate control is performed, the braking force control is not performed on the front wheels that are non-driven wheels in the traction control. The wheel speed is selected, and either the inner wheel side or the outer wheel side is not subjected to the braking force control in the yaw rate control. Therefore, this wheel is selected, and based on these, the longitudinal speed V at the center of gravity position is selected._X(n) is calculated.
[0054]
In addition, when the driver is performing a braking operation or when the braking operation is not performed, but all wheels are controlled by the traction control or the yaw rate control, the estimated vehicle speed in the anti-lock brake control, for example, Based on the above, the longitudinal speed at the center of gravity is calculated.
[0055]
As a result, the wheel speed that accurately represents the front-rear speed at that time can be selected according to the braking state of the vehicle, and the front-rear speed at the center of gravity position can be calculated based on this wheel speed. Can be estimated.
[0056]
In the second embodiment, the case where the driver's braking operation is detected by detecting the master cylinder pressure with the master cylinder pressure sensor 16 has been described. However, the present invention is not limited to this. It may be detected by a switch signal of a brake lamp switch that is turned on when the pedal is depressed.
[0057]
Next, a third embodiment of the present invention will be described with reference to FIG.
In the third embodiment, since the steering angle δ is not used when calculating the estimated side slip angle in the first and second embodiments described above, the longitudinal acceleration α in the low vehicle speed range is used._XLateral acceleration α_YThe side slip angle can be estimated with high accuracy in the state of large, but the estimation accuracy will be reduced at other high vehicle speeds, so by switching to other estimation methods at high vehicle speeds, It is designed to enable highly accurate sideslip angle estimation in the vehicle speed range.
[0058]
That is, the estimation method switching process shown in FIG.
This estimation method switching process is executed as a timer interruption process every predetermined time (for example, 10 msec). First, in step S21, the estimation method used last time uses a motion model similar to the first conventional example described above. It is determined whether or not the vehicle side slip angle estimation method is used. If the vehicle side slip angle estimation method is the high speed side slip angle estimation method, the process proceeds to step S22, and the higher wheel speed Vw of the left and right wheels of the rear wheel 1R as the drive wheel is determined._RHHigh wheel speed Vw of the left and right wheels of the front wheel 1F as a non-drive wheel_FHThe value obtained by subtracting (Vw_RH-Vw_FH) Is a preset value ΔVw₁Larger and higher wheel speed Vw of the front wheel 1F as a non-drive wheel_FHSet vehicle speed Vw set in advance_S1It is determined whether it is smaller than (Vw_RH-Vw_FH)> ΔVw₁And Vw_FH<Vw_S1When it is, it is determined that the driving wheel is spinning in the low vehicle speed range, and the process proceeds to step S23.
[0059]
In this step S23, the longitudinal speed V according to the first embodiment or the second embodiment described above._X(n) and estimated longitudinal speed V ^_XBy feeding back an error signal with (n), the estimated longitudinal speed V ^_X(n) and estimated lateral velocity V ^_Y(n) is calculated, and the estimated skid angle β ^ (n) is calculated by the low speed skid angle estimating method using the skid angle estimating method for calculating the estimated skid angle β ^ (n) from these. Transition.
[0060]
In this step S24, since the estimated yaw rate γ ^ (n) is used in the high vehicle speed side slip angle estimating method described later, the actual yaw rate γ (n) detected by the yaw rate sensor 11 is stored as the estimated yaw rate γ ^ (n). Then, the process proceeds to step S25, where the current estimation result (γ (n), β (n), V_X(n), V_Y(n)) is stored as the previous value, and a flag F indicating the type according to the used skid estimation method is set, and then the timer interrupt process is terminated and the program returns to a predetermined main program.
[0061]
On the other hand, when the determination result in step S22 does not satisfy the set condition, the process proceeds to step S26, the estimated skid angle β ^ (n) is calculated by the high-speed skid angle estimation method, and then the process proceeds to step S27. Estimated longitudinal speed V ^ used in the low-speed side slip angle estimation method in S23_XAs the vehicle speed V (n) and the estimated lateral speed V ^ according to the following equation (13):_YAfter calculating (n), the process proceeds to step S25.
[0062]
V ^_X(n) = V (n) * tan (β ^ (n)) ………… (13)
Further, when the determination result in step S21 is that the previous estimation method is the low-speed side slip angle estimation method, the process proceeds to step S28, and the higher of the left and right wheels of the rear wheel 1R as the drive wheels is the same as in step S22. Wheel speed Vw_RHHigh wheel speed Vw of the left and right wheels of the front wheel 1F as a non-drive wheel_FHThe value obtained by subtracting (Vw_RH-Vw_FH) Is the preset value ΔVw₁Greater set value ΔVw₂Larger and higher wheel speed Vw of the front wheel 1F as a non-drive wheel_FHIs the preset vehicle speed Vw_S1Very large set vehicle speed Vw_S2It is determined whether it is larger than (Vw_RH-Vw_FH)> ΔVw₁And Vw_FH> Vw_S2If it is, it is determined that the vehicle is in the high vehicle speed range or that the wheel is not spun on the driving wheel, and the process proceeds to step S26. Otherwise, it is determined that the wheel is spun on the driving wheel. The process proceeds to S23.
[0063]
In addition, the high-speed side slip angle estimating method in step S26 is based on the two-wheel motion model of FIG._fAnd the slip angle β of the rear tire_rCan be represented by the following formulas (14) and (15).
[0064]
β_f= Tan^-1{(V_Y-L_fγ) / V_X} + Δ (14)
β_r= Tan^-1{(V_Y-L_rγ) / V_X} ………… (15)
Furthermore, vehicle speed V_XCan be linearized in a state where is somewhat large, the vehicle body side slip angle β and the vehicle body longitudinal speed V expressed by the following equation (16):_XAnd lateral velocity V_YThe relationship of the following formulas (17) and (18) is obtained instead of the formulas (14) and (15), and the following formulas (19) and (20) are finally obtained from the above. The linear two-wheel model is obtained.
[0065]

This linear two-wheel model can be expressed by the following state spaces (21) to (28) for control design.
[0066]
[Expression 1]

[0067]
The observer is designed as shown in the following equation (30) for the vehicle models of the above equations (21) and (22).
x ^ '= Ax ^ + Bu + Ly ~ (30)
Here, A, B, C, and D are matrices for calculating the motion of the vehicle. x ^ is an estimated state quantity, and L is a gain that determines a correction amount of the state estimated quantity. Here, the error signal y˜ is obtained by the following equation (31), and the estimated state quantity x ^ is obtained by the following equation (32).
[0068]
y- = y- (Cx ^ + Du) (31)
[0069]
[Expression 2]

[0070]
Therefore, the matrixes A to D of the expressions (25) to (28) are calculated in step S31 in FIG. 6, and then the process proceeds to step S32 to estimate using the expressions (29) and (30). The yaw rate γ ^ and the estimated skid amount β ^ are calculated, and then the process proceeds to step S33, where the calculated estimated yaw rate γ ^ and the estimated skid amount β ^ are stored as previous values, and the process is terminated.
[0071]
According to the third embodiment, when a state in which a wheel spin occurs in the rear wheel, which is a driving wheel at a low vehicle speed range such as when the vehicle starts, the high-speed skid angle estimation method is selected during the previous processing. However, the process proceeds from step S22 to step S23, and the longitudinal speed V according to the first or second embodiment is determined._X(n) and estimated longitudinal speed V ^_XBy feeding back an error signal with (n), the estimated longitudinal speed V ^_X(n) and estimated lateral velocity V ^_Y(n) is calculated, and the estimated side slip angle β ^ (n) is calculated by the low side slip angle estimation method using the side slip angle estimation method that calculates the estimated side slip angle β ^ (n) from these. The estimated side slip angle β ^ can be calculated.
[0072]
From this state, when the wheel spin of the rear wheel as the driving wheel is settled or the vehicle speed is increased, when the determination condition in step S28 is not satisfied, the process proceeds to step S26, and the high-speed side slip angle estimation shown in FIG. Since the process is executed, it is possible to estimate the side slip angle with high accuracy in the high vehicle speed range.
[0073]
In the third embodiment, the case where the estimated yaw rate γ ^ and the estimated skid angle β ^ are calculated using the equations (25) to (31) as the high-speed skid estimation method has been described. The present invention is not limited to this, and other sideslip angle estimation methods such as the first conventional example and the second conventional example described above can be applied.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an overall configuration of a first embodiment of the present invention.
FIG. 2 is an explanatory diagram showing a two-wheel motion model.
FIG. 3 is a block diagram showing an overall configuration of a second embodiment of the present invention.
FIG. 4 is a flowchart showing an outline of arithmetic processing in the second embodiment.
FIG. 5 is a flowchart showing an outline of arithmetic processing according to a third embodiment of the present invention.
FIG. 6 is a flowchart illustrating an example of a high-speed skid angle calculation process in the third embodiment.
[Explanation of symbols]
10. Vehicle state quantity estimation device
11 Yaw rate sensor
12 Longitudinal acceleration sensor
13 Lateral acceleration sensor
14 Wheel speed sensor
15 Steering angle sensor
16 Master cylinder pressure sensor
20 Target braking force setting device
30 Braking force control device

Claims (3)

When the value of the wheel speed of the rear wheel that is the driving wheel is larger than a certain value or a certain ratio with respect to that of the front wheel that is the non-driving wheel, and the wheel speed or the vehicle speed of the front wheel is smaller than a certain value In addition, the longitudinal speed and yaw rate of the vehicle are detected, the longitudinal acceleration and lateral acceleration of the vehicle are detected, and the vehicle is moving around the vertical axis in the longitudinal direction and lateral direction of the vehicle, respectively. The front-rear speed, yaw rate, front-rear acceleration, and lateral acceleration detected in the motion model described as a known quantity, the estimated front-rear speed and the estimated lateral speed as unknown quantities, the front-rear speed and the estimated front-rear speed The estimated longitudinal velocity and the estimated lateral velocity are calculated by performing an observer operation using the error of the feedback signal as the feedback signal. Using the low-speed vehicle body slip angle estimating method for estimating a sideslip angle of the vehicle body on the basis of the estimated lateral velocity, characterized in that to use a vehicle slip angle estimating method for other fast otherwise A vehicle body side slip angle estimation method. The longitudinal direction of speed, the vehicle body slip angle estimating method for a vehicle according to claim 1, characterized by using any of the estimated value of the wheel speed and the wheel speed. Wheel speed calculation means for calculating the wheel speed of each wheel of the vehicle, yaw rate detection means for detecting the yaw rate generated in the vehicle body, longitudinal acceleration detection means for detecting the longitudinal acceleration generated in the vehicle body, and generated in the vehicle body A lateral acceleration detecting means for detecting a lateral acceleration; a longitudinal speed calculating means for calculating a longitudinal speed based on a wheel speed detected by the wheel speed calculating means and a yaw rate detected by the yaw rate detecting means; and a vehicle For the longitudinal direction and lateral direction of the vehicle, the longitudinal velocity, yaw rate, longitudinal acceleration and lateral acceleration detected in the motion model describing the state in which the vehicle is moving around the vertical axis are assumed to be known amounts, respectively. The front-rear direction speed and the estimated front-rear direction speed calculated by the front-rear direction speed calculating means are defined as unknown amounts of the direction speed and the estimated lateral speed. Speed estimation means for estimating the longitudinal and lateral velocities by performing an observer operation that feeds back an error signal from the above, and a skid angle calculation for calculating a side slip angle based on the longitudinal and lateral velocities estimated by the speed estimation means A vehicle body side slip angle estimating device for low speed and a vehicle body side slip angle estimating device for high speed having a configuration different from that of the vehicle body side slip angle estimating device for low speed. The low-speed vehicle body slip angle estimation device is selected when the value of is greater than a certain value or a certain ratio with respect to that of the front wheels that are non-driven wheels, and the wheel speed or vehicle speed of the front wheels is smaller than a certain value. In other cases, the vehicle body side slip angle estimating device for a vehicle is selected.

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