JP2004149060A - Automatic steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a vehicle to stably follow a reference traveling line even when limiter processing is executed by an integrating process part to allow the vehicle to travel along the reference traveling line. <P>SOLUTION: A controller 20 is provided with a stabilizing control torque generating part 124 calculating stabilizing control torque u<SB>s</SB>for stabilizing the vehicle based on the reference traveling line of a certain road curvature in accordance with a traveling state of the vehicle obtained by an observer 110, a reference traveling line following torque generating part 130 and an accumulator 123 for calculating the deviation quantity of an actual traveling line with respect to the reference traveling line based on a relative position, and calculating reference traveling line following torque u<SB>2</SB>for allowing the vehicle to travel following the reference traveling line based on the deviation quantity, and an accumulator 122 for calculating target steering torque u by adding the stabilizing control torque u<SB>s</SB>to the reference traveling line following torque u<SB>2</SB>. <P>COPYRIGHT: (C)2004,JPO

Description

【００２８】
また、目標軌道の接線の傾きの変化量が道路曲率ρで定義したとき、単位時間当たりの目標軌道からの相対的な車両のヨー角変化、すなわち目標軌道に対する相対ヨーレートφ’_ｒは、
【００２９】
【数２】

【００３０】
であり、また、相対横速度ｙ’_ｃｒは、
【００３１】
【数３】

【００３２】
であるから、前記（１）式より横滑り角及び横滑り角速度を消去し、整理するとそれぞれ下記（４）式及び（５）式が得られる。
【００３３】
【数４】

【００３４】
【数５】

【００３５】
また、基準走行ラインに対する車両１の横方向の前方注視点横変位ｙ_ｓｒは、前方注視点位置の車両前方の距離をＬ_ｓ［ｍ］とおいて、目標軌道（走行車線）からの相対横変位ｙ_ｃｒ 、相対ヨー角φ_ｒ及び道路曲率ρを用いると、下記（６）式として記述できる。
【００３６】
【数６】

【００３７】
一方、前記図２に示す自動操舵装置における操舵系の運動方程式は次のように記述できる。
【００３８】
【数７】

【００３９】
ここで、ζ：車両のトレール長さ、Ｋ_Ｔ：操舵アクチュエータのトルク係数、Ｎ_ｓ：操舵アクチュエータから操舵系へのトルク伝達比、Ｃ_ｓ：操舵系の減衰係数そして、前記（４）式及び（５）式と同様に、横滑り角β及び横滑り角速度β’を消去し、整理すると下記（８）式のようになる。
【００４０】
【数８】

【００４１】
これら（４）式〜（６）式及び（８）式を新たに目標として道路曲率を状態変数に加えて行列表現することにより、曲線走行状態における車両モデルは下記（９）式のように記述できる。
【００４２】
【数９】

【００４３】
前記動的システムに対して、ある行列Ｌを用いて
【００４４】
【数１０】

【００４５】
なる演算を行って、状態変数ベクトルｚを算出する。ここで算出する状態変数ベクトルｚと、真の車両状態量ベクトルｘとの偏差をｅとすると、前記（９）式及び（１０）式から下記（１１）式が得られる。
【００４６】
【数１１】

【００４７】
前記遷移行列Ａ−ＬＣのすべての固有値の実部が負になるように行列Ｌを決定すると下記（１２）式のようになる。
【００４８】
【数１２】

【００４９】
これにより、任意の初期値ｅ（ｔ_０）の値によらず、十分に時間の経過後には先に算出された状態変数ベクトルｚと真の車両状態量ベクトルｘとの偏差ベクトルｅは０となり、状態変数ベクトルｚと真の車両状態量ベクトルｘと一致するので、車両の状態量を正しく検出することができる。
ここで、前記（１０）式はオブザーバを示すもので、このようなオブザーバを用いた解法は動的システムの状態推定に良く利用される手法である。
【００５０】
一方、システムへのプロセスノイズｗ及び観測ノイズ（センサーノイズ）ｎを考慮するとシステムの行列表現は下記（１３）式として記述できる。
【００５１】
【数１３】

【００５２】
そして、前述したオブザーバと同様に偏差ベクトルｅを下記（１４）式として得ることができる。
【００５３】
【数１４】

【００５４】
ここで、プロセスノイズｗとセンサーノイズｎとが正規性白色ノイズであると仮定した場合、推定誤差ｅを最小にするように行列Ｌを求めたものがカルマンフィルタとなり、動的システムの状態推定にしばしば利用される。
ところで、プロセスノイズｗには、横風や路面カント（片勾配）を原因とするヨー方向へのモーメント成分や横方向への横力成分のように、厳密には正規性白色ノイズではない持続的な外乱が作用したり、車両パラメータ誤差等のモデル化誤差が存在するため、状態推定値が真の値に収束しない場合がある。このような結果、前記図３に示すレギュレータ１２１だけの単純な状態フィードバック制御では定常的な位置ずれを生じる可能性がある。このような場合、車両が基準走行ラインからそれる方向へに舵制御されることになり、運転者は強い違和感を感じる可能性が高い。
【００５５】
これに対し、本実施の形態におけるコントローラ２０は、次のような構成を備えている。図５は、コントローラ２０を、基本的な機能構成（図３に示した構成）を含む本発明を適用した系全体をブロック図である。
すなわち、図５に示すコントローラ２０は、図３に示したコントローラ２０と同様に、曲線走行状態をモデルとして構成されたオブザーバ１１０と、レギュレータゲインＫ_ｓ（図３では、Ｋ_０）とを含んだ構成になっている。そして、オブザーバ１１０についても、前述したような手法で決定される行列Ａ，Ｂ，Ｃ及びゲインＬを有するとともに、加算器１１１，１１２を含んで構成されている。ここで、オブザーバ１１０中に示す、ｓはラプラス演算子であり、ｚは状態量ｘの推定値、 Ｃｚは観測値ベクトルｙの推定値である。
【００５６】
ここで、本実施の形態におけるコントローラ２０の詳細をさらに図６を用いて説明すると、コントローラ２０は、車両１の前方注視点横変位ｙ_ｓｒと基準走行ラインｙ_ｒｅｆとの偏差Δｙを得る加算器１２３と、加算器１２３により得た偏差Δｙに基づいて車両１に発生すべき基準走行ライン追従トルクｕ_２を算出する基準走行ライン追従トルク発生部１３０と、安定化制御トルクｕ_ｓを算出する安定化制御トルク発生部（Ｋ_ｓ）１２４と、基準走行ライン追従トルク発生部１３０が算出した前記基準走行ライン追従トルクｕ_２と安定化制御トルク発生部（Ｋ_ｓ）１２４が算出した安定化制御トルクｕ_ｓとを加算して目標操舵トルクｕを得る加算器１２２とを含んで構成されている。
【００５７】
基準走行ライン追従トルク発生部１３０は、積算部１４０と、積算部１４０からの出力値にゲインＫ_２を掛ける乗算部１３１とを備えている。
積算部１４０は図７に示すように構成されている。積算部１４０は、前記加算部１２３からの出力値である、前方注視点横変位ｙ_ｓｒと基準走行ラインｙ_ｒｅｆとの偏差Δｙにサンプリング時間Ｔを乗じ、その値に当該積算部１４０で１サンプリング時間前に得た積算値を加算し、リミット処理部１４１で所定のリミット処理を行って最新の積算値を算出する。
【００５８】
なお、積算部１４０中のｑ^−１はシフト演算子であり、入力された信号を、ｑ^−１で１サンプリング時刻だけ遅れて出力する。また、リミット処理部１４１で用いる積算値の上限値及び下限値については、基準走行ライン追従トルクｕ_２が所定の上限値及び下限値の範囲内にとどまるように決定している。
基準走行ライン追従トルク発生部１３０は、このような積算部１４０により算出した積算値に、乗算部１３１でゲインＫ_２を乗じ、基準走行ライン追従トルクｕ_２を得る。なお、乗算部のゲインＫ_２の値の選定については後で詳述する。
【００５９】
安定化制御トルク発生部（Ｋ_ｓ）１２４は、道路曲率ρによって与えられる基準走行ライン周りの車両の走行状態を安定化させるための安定化制御トルクｕ_ｓを算出するように構成されている。図８は、その具体的構成を示す。
安定化制御トルク発生部１２４にはオブザーバ１１０が推定する状態量ｚが入力されており、安定化制御トルク発生部１２４は、２種類のレギュレータゲインＫ_０，Ｋ_１それぞれをその状態量ｚに乗じ、それに対応して第１及び第２の安定化制御トルクｕ_０，ｕ_１を算出する。なお、レギュレータゲインＫ_０，Ｋ_１の値の選定については、レギュレータゲインＫ_ｓの値の選定として後で詳述する。
【００６０】
安定化制御トルク発生部１２４は、基準走行ライン追従トルクｕ_２がリミット処理されている場合とそうでない場合に応じて第１の安定化制御トルクｕ_０と第２の安定化制御トルクｕ_１とを切り換えて、第１の安定化制御トルクｕ_０と第２の安定化制御トルクｕ_１とのいずれか一方を安定化制御トルクｕ_ｓとして出力する。ここで、第１の安定化制御トルクｕ_０の方が第２の安定化制御トルクｕ_１よりも小さな値になっており、基準走行ライン追従トルクｕ_２のリミット処理作動時には、第１の安定化制御トルクｕ_０を安定化制御トルクｕ_ｓとして出力する。
【００６１】
このように安定化制御トルク発生部（Ｋ_ｓ）１２４により安定化制御トルクｕ_ｓが得られ、この安定化制御トルクｕ_ｓは、道路曲率をρとする基準走行ライン周りの微小なずれを補正する値となる。そして、この安定化制御トルクｕ_ｓは前記加算器１２２に入力される。加算器１２２では、この安定化制御トルクｕ_ｓと前記基準走行ライン追従トルク発生部１３０からの基準走行ライン追従トルクｕ_２とを加算して目標操舵トルクｕを得る。
【００６２】
ここで、積算部１３０のゲインＫ_２やレギュレータゲインＫ_ｓ（レギュレータゲインＫ_０，Ｋ_１）の値の決定について説明する。
ゲインＫ_２は、その値を大きくすると基準走行ラインへの追従速度が速くなるといった特性をもつゲインである。このようなことから、ゲインＫ_２は、前方注視点横変位ｙ_ｓｒと基準走行ラインｙ_ｒｅｆとの偏差Δｙの積分値がわずかに変化した場合であっても、基準走行ライン追従トルクｕ_２に大きな変化を与えてしまう。この結果、例えば前方注視点横変位ｙ_ｓｒの検出結果に含まれるノイズ成分に過敏に反応した基準走行ライン追従トルクｕ_２が算出されて、操舵系の動きがぎこちなくなる可能性がある。
【００６３】
また、レギュレータゲインＫ_ｓに比べてゲインＫ_２があまりに大きすぎると、基準走行ラインを基準に車両の安定化を図る安定化制御トルクｕ_ｓが相対的に低下してしまう。この結果、前方注視点横変位ｙ_ｓｒと基準走行ラインｙ_ｒｅｆとの偏差Δｙがそれほど大きくない場合であっても、基準走行ライン追従トルクｕ_２が支配的になり、基準走行ラインに対する行き過ぎ量が大きくなる。これにより、車両が基準走行ライン上を通過する瞬間には基準走行ラインから逸脱する方向への制御トルクが残ってしまい、車両の走行安定性といった面或いは運転者の操舵感といった面から好ましくない状態が発生する可能性がある。
【００６４】
逆に、ゲインＫ_２を小さくしすぎると、走行安定性は相対的に向上するが、追従速度は低下する。この結果、車両がまだ目標軌道に達していないにも拘わらず目標軌道へ向かっていくことに抵抗するような操舵トルクが演算されてしまい、運転者の操舵感といった面から好ましくない状態が発生する可能性がある。
以上のようなことから、ゲインＫ_２及びレギュレータゲインＫ_ｓ（レギュレータＫ_０，Ｋ_１）をそれぞれ任意の値として単独で設定するのではなく、ゲインＫ_２とレギュレータゲインＫ_ｓとがうまく協調するような組み合わせで決定する。例えば、車両１に対して自動操舵制御を実行した状態での動特性を実験やシミュレーションで充分に確認し、その動特性を考慮しつつ適宜選定するようにする。例えば、ゲインＫ_２の値とレギュレータゲインＫ_ｓの値との最適な組み合わせは次のような手法により求める。
【００６５】
例えば、図３のような構成においてレギュレータゲインＫ_０を求める手法として、前記（９）式に対応した次の評価関数Ｊを最小にするレギュレータを最適レギュレータにする、といった手法が知られている。
【００６６】
【式１５】

【００６７】
ここで、行列Ｑ，Ｒを調整することにより系の応答を調整することができ、また、下記（１６）式により安定化制御トルクｕ_０を算出できる。
【００６８】
【式１６】

【００６９】
このような手法を適用して、図６に示した装置では、前方注視点横変位ｙ_ｓｒと基準走行ラインｙ_ｒｅｆとの偏差Δｙの積分値をｈとしたとき、下記（１７）式を得ることができる。
【００７０】
【式１７】

【００７１】
このような拡張系で下記（１８）式に示す評価関数Ｊを最小にする最適レギュレータを演算すればよい。
【００７２】
【式１８】

【００７３】
ここで、行列ｑ_ｈ，Ｑ’，Ｒ’を調整することで系の応答を調整することができ、また、下記（１９）により目標操舵トルクｕを算出することができる。
【００７４】
【式１９】

【００７５】
なお、この場合でも、車両１に対して自動操舵制御を実行した状態での動特性を実験やシミュレーションで充分に確認し、その動特性を考慮しつつ適宜選定する必要がある。しかし、実際には基準走行ラインへの追従速度を行列ｑ_ｈで調整し、そのときの車両の安定度が不足気味なら行列Ｑ’の要素を徐々に大きい値へ修正していく程度で望ましい応答が得られる場合が多い。
【００７６】
図９は、コントローラ２０の処理手順を示す。コントローラ２０はこの処理を所定のサンプリング・クロックに同期して実行する。
自動操舵制御が実行されると、先ずステップＳ１において、コントローラ２０は、舵角センサ１４からの舵角検出信号δ_ｆ、車速センサ１９からの車速検出信号Ｖ、及びＣＣＤカメラ１７から画像をそれぞれ読み込む。
【００７７】
なお、車速検出信号Ｖは、オブザーバ１１０の行列Ａ，Ｂ，Ｃの要素を決定するのに必要な情報であるため、車速Ｖとして行列Ａ，Ｂ，Ｃに取り込まれることになる。
続いてステップＳ２において、コントローラ２０は、前記ステップＳ１で読み込んだ画像に基づいて、前記前方注視点横変位ｙ_ｓｒを検出する。
【００７８】
続いてステップＳ３において、コントローラ２０は、オブザーバ１１０に基づいた演算（前記（１０）式）を実行することで、実際の車両状態量ｘを推定する演算を行い、車両状態推定ベクトルｚを出力する。
続いてステップＳ４において、コントローラ２０は、前記ステップＳ３で得た車両状態量推定ベクトルｚと、２種類の減衰特性の異なるＫ_０，Ｋ_１とに基づいて、２種類の減衰特性の異なる安定化制御トルクｕ_０，ｕ_１を得る（前記（１９式）により得る）。すなわち、
ｕ_０＝−Ｋ_０ｚ，ｕ_１＝−Ｋ_１ｚ
を得る。
【００７９】
続いてステップＳ５において、コントローラ２０は、前記ステップＳ２で検出した前記前方注視点横変位ｙ_ｓｒと基準走行ラインｙ_ｒｅｆとの偏差Δｆを積算し、その積算値にゲインＫ_２を乗算し、基準走行ライン追従トルクｕ_２を算出する。
また、このステップＳ５において、コントローラ２０は、その基準走行ライン追従トルクｕ_２に対して所定の上限値又は下限値によるリミット処理を行うとともに、前記横変位ｙ_ｓｒと基準走行ラインｙ_ｒｅｆとの偏差Δｙの積算値についてもリミット処理を行う。そして、リミット時にリミットフラグをセットする。このようにそれぞれリミット処理することで、偏差積分値の絶対値がそれ以上増加しないようにする。すなわち、基準走行ライン追従トルクｕ_２がリミット処理された時点での前記横変位ｙ_ｓｒと基準走行ラインｙ_ｒｅｆとの偏差Δｙの積算値が上限値又は下限値になる。
【００８０】
続いてステップＳ６において、コントローラ２０は、前記ステップＳ５で得た基準走行ライン追従トルクｕ_２がリミット処理されているか否かの判定を行う。すなわち、前記リミットフラグがセットされているか否かを判定し、基準走行ライン追従トルクｕ_２がリミット処理されているか否かの判定を行う。ここで、コントローラ２０は、基準走行ライン追従トルクｕ_２がリミット処理されている場合、ステップＳ７に進み、基準走行ライン追従トルクｕ_２がリミット処理されていない場合、ステップＳ８に進む。
【００８１】
ステップＳ７では、コントローラ２０は、第１の安定化制御トルクｕ_０を安定化制御トルクｕ_ｓとして決定する。一方、コントローラ８では、コントローラ２０は、第２の安定化制御トルクｕ_１を安定化制御トルクｕ_ｓとして決定する。このようにステップＳ７及びステップＳ８により、コントローラ２０は、基準走行ライン追従トルクｕ_２がリミット処理されている場合とそうでない場合に応じて２種類の安定化制御トルクｕ_０，ｕ_１を切り換えて安定化制御トルクｕ_ｓを決定している。
【００８２】
続いてステップＳ９において、コントローラ２０は、この安定化制御トルクｕ_ｓと基準走行ライン追従トルクｕ_２とを加算して、目標操舵トルクｕを得る。ここでは、例えば、制御される操舵トルクが滑らかに推移するような処理を行う。
続いてステップＳ１０において、コントローラ２０は、ステップＳ９で得た目標操舵トルクｕの出力処理としてアクチュエータ駆動処理行う。すなわち、コントローラ２０は、自動操舵機構１０の電動モータ１０ａへの電流を制御してステアリングシャフト４に目標駆動トルクを入力することで、その目標操舵トルクとなるように車両の前輪３Ｌ，３Ｒに舵角を発生させる。ここでの制御として、例えば、自動操舵機構を構成している電動モータ１０ａに印加する電流をＨブリッジ回路を用いたＰＷＭ機構等によって制御し、目標操舵トルクｕを操舵系に入力する。
【００８３】
このステップＳ１０の処理が終了したら、今回の処理を終了する。その後は、所定のサンプリング時刻が経過するまで待機した後に、前記ステップＳ１から処理を再び実行する。
以上のような手順でコントローラ２０は処理を行う。このような処理により、車両は、基準走行ライン追従トルクの作用により曲率のある道路を追従して走行するとともに、安定化制御トルクの作用によりその曲率を有する道路に沿って安定して走行するようになる。
【００８４】
次に効果を説明する。
前述したように、基準走行ライン追従トルクｕ_２に対して所定の上限値又は下限値によるリミット処理を行うとともに、横変位ｙ_ｓｒと基準走行ラインｙ_ｒｅｆとの偏差Δｙの積算値についてもリミット処理を行うことで（前記ステップＳ５）、基準走行ライン追従トルクｕ_２の過剰な発生を抑え、これにより過剰な目標操舵トルクｕの発生を抑えることができる。
【００８５】
これにより、例えば、運転者の操舵介入が原因でなかなか基準走行ラインに到達しない状態から、運転者が急に操舵介入を中止した場合であっても、基準走行ライン追従トルクｕ_２の残留成分の影響で基準走行ラインを通り過ぎても未だ操舵トルクが入力され続けるような状態を防止できる。また同様に、強めの外乱が急に減少した場合や外乱の向きが急に変化した場合、さらには基準走行ラインの位置を大きく変更した場合等の状況において、余分な車両挙動を発生することなく車両１を走行させることができる。
【００８６】
リミット処理を行うことで以上のような効果がある一方で、リミット処理が作動している場合には、目標軌道が基準走行ライン追従トルクを増加させる方向へどんなに変化しても算出される基準走行ライン追従トルクが一定値になるので、等価的にオフセットトルクのフィードバックゲインが小さくなる。これは、本来は積分値が増大していく過程であるにも拘わらず基準走行ライン追従トルクが一定値で維持されるので、リミット処理が作動している間は、ゲインが小さくなっていくのと等価となるからである。そして、このような場合、制御系全体として減衰が過度に強い状態になってしまう。すなわち、状態フィードバックにより車両の姿勢を現状にとどめようとする作用が過剰に作用し、基準走行ラインへの移動を阻害する制御が行われてしまう。
【００８７】
このような事態に対応して、安定化制御トルクｕ_ｓを基準走行ライン追従系とは独立して設定可能とし、基準走行ライン追従トルクｕ_２の変化に応じて安定化制御トルクｕ_ｓを変化させることにより、基準走行ライン追従トルクｕ_２に関する制限が定常的に系に作用した場合に発生してしまう急激なトルク変化や走行位置の変化を抑止することができる。具体的には、基準走行ライン追従トルクｕ_２のリミット処理作動時には、安定化制御トルクｕ_ｓも小さくすることで、すなわちレギュレータゲインＫ_ｓ（車両状態量のフィードバックゲイン）を小さい値に変更（前記ステップＳ７においてレギュレータゲインＫ_ｓとしてレギュレータゲインＫ_１を選択）することで、系の減衰力を相対的に低下させて、基準走行ライン追従系の過減衰状態を解消する。このようにすることで、車両１の移動速度を適切にすることができる。
【００８８】
以上のように、リミッタ処理の作動時に、車両状態を安定させるための状態フィードバック制御を変化させることで、目標軌道への追従速度を劣化させてしまうことを解消でき、目標軌道への追従性と走行安定性とを両立することができる。
また、安定化制御トルクｕ_ｓの調整或いは補正を、複数のレギュレータゲインＫ_０，Ｋ_１を用意するだけでよく、すなわち基準走行ライン追従トルクｕ_２のリミット処理の作動により発生する基準走行ライン追従系の過減衰状態が起きないようにレギュレータゲインＫ_ｓを設計しておくだけでよく、目標軌道への追従性と走行安定性とを両立することができるシステムを簡単な構成として構築することができる。
【００８９】
また、前述したようにオブザーバ１１０としてカルマンフィルタを用いているので、より好適な演算を実効することができる。すなわち、オブザーバゲインの要素数は出力数（センサの個数）と状態変数との組み合わせ（出力数（センサの個数）×状態変数）になるので、安定で（オブザーバの極の実部が全て負の値であって）、推定精度が良く、かつセンサのノイズ成分を有効に除去することが可能なオブザーバの設計は一般に易しくない。一方、カルマンフィルタの設計にあたっては、センサのノイズや車両に作用するプロセスノイズの分散値が設計のパラメータとして必要ではあるが、これらは予め調べることが可能であるため、ほとんど試行錯誤することなくオブザーバゲインを設計することが可能である。このようなことから、前述したようにオブザーバ１１０としてカルマンフィルタを用いることで、より好適な演算を実効することが可能になる。
【００９０】
以上、本発明の実施の形態について説明した。しかし、本発明は、前述の実施の形態として実現されることに限定されるものではない。
すなわち、前述の実施の形態では、ＣＣＤカメラ１７が撮影した画像に基づいて、車両１の基準走行ラインに対する相対位置（横変位）を検出しているが、これに限定されるものではい。例えば、公知の誘導ケーブル方式や公知の磁気マーカ方式によって横変位を検出するようにしてもよい。或いは、特開平３−２９３４１１号公報に開示される技術のように、走行路に沿って設置されたガードレールと車両との間の距離を超音波を利用して測定し、その測定した距離から基準走行ラインに対する車両の横方向位置を検出してもよい。さらには、複数の方式を組み合わせてもよい。
【００９１】
また、前述の実施の形態では、前輪３Ｌ，３Ｒを操舵するようにしているが、後輪を操舵するようにしてもよいし、或いは、前輪及び後輪の両方を操舵するようにしてもよい。
また、前述の実施の形態では、操舵角のみが自動制御できるようになっているが、これに限定されるものではない。例えば、４輪のブレーキや駆動を独立に制御することができるアクチュエータを設け、そのアクチュエータの状態をコントローラ２０から供給する制御信号によって制御可能とすることで、車両のヨーモーメントを任意に制御できるようにしてもよい。
【００９２】
また、前述の実施の形態では、リミッタ処理作動時に選択される第１の安定化制御トルクｕ_０は１種類に限るものではなく、複数種類であってもよい。具体的には、車両１の横方向の移動速度が大きくなるときに徐々に小さくなるような複数のレギュレータゲインを用意し、この複数のレギュレータゲインを用いて複数の第１の安定化制御トルクｕ_０を得るようにする。この場合、横方向の移動速度に合わせてレギュレータゲインを変更して、第１の安定化制御トルクｕ_０（安定化制御トルクｕ_ｓ）を得ることで、多少移動速度は低下するが、より滑らかな車両挙動を得ることができる。すなわち、目標走行ライン追従トルクがリミット処理されている状態におけるレギュレータゲイン切り換え時には、ゲインの切り換えに伴う目標操舵トルクの変動や車両の横方向への移動速度を考慮した設定をきめ細く行うことが可能になり、これにより、なめらかな車両の走行を保つことが可能になる。
【００９３】
なお、ここでは、車両状態を車両１の横方向の移動速度とし、その移動速度に応じてレギュレータゲインを決定し、そして第１の安定化制御トルクｕ_０を変更しているが、他の車両状態に応じてレギュレータゲインし、第１の安定化制御トルクｕ_０を変更してもよい。
また、ゲイン切り換え後に車両が基準走行ライン上を交差する瞬間か、又は基準走行ライン上を交差することが予想されたとき、基準走行ライン追従トルクｕ_ｓを０にすると同時に基準走行ラインを修正する。具体的には、制御目標としている基準走行ラインを現在走行している走行ラインに修正する。これにより、車両の目標軌道に対する行き過ぎ量（オーバーシュート量）を極力減らし、より望ましい走行状態を保つことができる。
【００９４】
また、前述の実施の形態では、図７に積算部１４０の具体的な構成を示したが、これに限定されるものではない。例えば、積算部１４０を図１０に示すように構成してもよい。
この場合、積算部１４０は、前記加算部１２３からの前方注視点横変位ｙ_ｓｒと基準走行ラインｙ_ｒｅｆとの偏差Δｙと、１サンプリング時刻前の偏差Δｙとの移動平均を演算し、演算した値にサンプリング時間Ｔ／２を乗じる。そしてその値に、１サンプリング時間前の積算値を加算し、リミット処理部１４１で所定のリミット処理を行って最新の積算値を算出する。
【００９５】
なお、積算部１４０中のｑ^−１はシフト演算子であり、入力された信号をｑ^−１で１サンプリング時刻だけ遅れて出力する。また、リミット処理部１４１で用いる積算値の上限値及び下限値は、基準走行ライン追従トルクｕ_２が所定の上限値及び下限値の範囲内にとどまるように決定している。
そして、基準走行ライン追従トルク発生部１３０は、このような積算部１４０により算出した積算値に乗算部１３１でゲインＫ_２を乗じ、基準走行ライン追従トルクｕ_２を得る。
【００９６】
この図１０に示す積算部１４０と前記図７に示す積算部１４０とでは演算精度が違っている。すなわち、前記図７に示す積算部１４０は、サンプリング時点での値だけを考慮する零次ホールド回路による近似演算を用いた構成をなし、図１０に示す積算部１４０は、サンプリング区間の前後の値を考慮した台形公式による近似演算を用いた構成をなしている。図７に示す積算部１４０による演算と図１０に示す積算部１４０による演算とは実質的には同じ演算であるが、得られる精度に差がある。例えば、サンプリング時間Ｔをあまり小さくできない等の制約がある場合、台形公式を用いた方が演算精度が高く、また滑らかに変化する結果を得られるので、この場合には、図１０に示す積算部１４０を用いる方がよい。このように使用状況等に応じて使い分けるようにしてもよい。
【００９７】
なお、前述の実施の形態において、ＣＣＤカメラ１７及びステップＳ１の処理は、基準走行ラインに対する車両の横方向の相対位置を検出する相対位置検出手段を構成し、オブザーバ１１０、基準走行ライン追従トルク発生部１３０、安定化制御トルク発生部（Ｋ_ｓ）１２４、及び加算器１２２，１２３は、相対位置検出手段の検出結果に応じて目標操舵トルクを演算する目標操舵トルク演算手段を構成し、自動操舵機構１０は、目標操舵トルクに基づいて車両の転舵輪に舵角を発生させる舵角発生手段を構成している。
【００９８】
また、目標操舵トルク演算手段を構成するオブザーバ１１０、基準走行ライン追従トルク発生部１３０、安定化制御トルク発生部（Ｋ_ｓ）１２４、及び加算器１２２，１２３のうち、オブザーバ１１０は、車両が走行中の道路の曲率を推定する道路曲率推定手段と、相対位置検出手段の検出結果に基づいて車両の走行状態を推定する走行状態推定手段とを構成し、安定化制御トルク発生部（Ｋ_ｓ）１２４は、走行状態推定手段が得た車両の走行状態に基づいて、道路曲率推定手段が得た道路曲率の基準走行ラインを基準にして車両を安定にする安定化制御トルクを算出する安定化制御トルク演算手段を構成し、基準走行ライン追従トルク発生部１３０及び加算器１２３は、相対位置検出手段が検出した相対位置に基づいて基準走行ラインに対する実際の走行ラインのずれ量を算出し、ずれ量に基づいて車両を基準走行ラインに追従走行させるための基準走行ライン追従トルクを算出する基準走行ライン追従トルク演算手段を構成し、加算器１２２は、安定化制御トルクと基準走行ライン追従トルクとを加算して目標操舵トルクを算出する加算手段を構成している。
【図面の簡単な説明】
【図１】本発明の実施の形態における車両の平面図である。
【図２】層だけいの一部を拡大した斜視図である。
【図３】車両の２輪モデル図である。
【図４】曲線走行状態をモデルとするオブザーバを用いた自動操舵系の構成を示すブロック図である。
【図５】本発明の実施の形態におけるコントローラの基本的な機能構成を示すブロック図である。
【図６】本発明の実施の形態における基準走行ライン追従トルク発生部の構成を示すブロック図である。
【図７】前記基準走行ライン追従トルク発生部の積算部の構成を示すブロック図である。
【図８】本発明の実施の形態における安定化制御トルク発生部の構成を示すブロック図である。
【図９】本発明の実施の形態におけるコントローラの処理手順を示すフローチャートである。
【図１０】前記基準走行ライン追従トルク発生部の積算部の他の構成を示すブロック図である。
【符号の説明】
１ 車両
２ ステアリングホイール
３Ｌ，３Ｒ 前輪（操舵輪）
１０ 自動操舵機構
１４ 舵角センサ
１７ ＣＣＤカメラ
１９ 車速センサ
２０ コントローラ
１１０ オブザーバ（カルマンフィルタ）
１２２，１２３ 加算器
１２４ 安定化制御トルク発生部
１３０ 基準走行ライン追従トルク発生部
１４０ 積算部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an automatic steering device that calculates a target steering angle according to a relative position of a vehicle in a lateral direction with respect to a reference traveling line.
[0002]
[Prior art]
There is an automatic steering device that calculates a target steering angle in accordance with a relative position of a vehicle in a lateral direction with respect to a reference traveling line. In this automatic steering device, the state of the vehicle is estimated by an observer, and a target steering angle is calculated based on the estimated state amount.
[0003]
However, in such an automatic steering device, a Kalman filter based on a straight running model is used as an observer. When the vehicle travels on a curved road using an observer based on a straight-line traveling model, a deviation in the equilibrium point of the observer causes a travel position deviation or the like. The automatic steering apparatus disclosed in Patent Document 1 employs an equilibrium point steering angle (offset steering angle) estimator having an integral characteristic in order to eliminate a traveling position deviation or the like caused by such an observer's equilibrium point deviation. Provided. More specifically, a travel position shift or the like due to a shift in the balance point of the observer is eliminated as described below.
[0004]
Calculates the equilibrium point steering angle as a value obtained by integrating the target steering angle until the target trajectory matches the actual running trajectory, or multiplies the integrated value of the difference between the target trajectory and the actual running trajectory by a predetermined coefficient. An equilibrium point steering angle is calculated, and the equilibrium point steering angle is input to an observer based on the linear running model. Here, the observer is configured to calculate a vehicle state quantity estimated from a yaw rate, a yaw angle, a lateral displacement, or the like.
[0005]
By inputting the virtually calculated equilibrium point steering angle to the observer, even if the observer is designed as a straight running model, the equilibrium point deviation can be corrected and the correct vehicle state quantity can be estimated. I have. Then, by performing the state feedback control of the correctly estimated vehicle state quantity, the vehicle can be driven along the reference traveling line that is a curved road.
[0006]
As described above, on the premise that the observer is constructed by a straight-line traveling model, the deviation of the traveling position caused by the modeling error that occurs when traveling on a curved road is corrected, and the reference traveling on a curved road is corrected. It realizes running a vehicle along a line.
[0007]
[Patent Document 1]
JP-A-10-297521
[0008]
[Problems to be solved by the invention]
In the configuration described above, the steering angle of the equilibrium point is integrated until the target trajectory and the actual traveling trajectory match, so design in consideration of the effect of the steering wheel operation due to the driver's intervention considering the mounting on the vehicle. There is a need. In other words, when there is a steering wheel operation due to the driver's intervention, it is assumed that the target trajectory does not coincide with the target trajectory for a long time. The configuration must be such that the absolute value of the steering angle does not diverge.
[0009]
However, the limiter process is not limited to being performed only when the driver performs steering intervention. For example, even when the target trajectory is greatly changed, the limiter processing is performed. However, even when the target trajectory is greatly changed in this way, if limiter processing is performed in the integration operation unit, the balance of the gain with the stabilization control unit will be lost, and the speed of following the target trajectory will be significantly reduced. This causes a problem.
[0010]
Further, in the above-described configuration, since the state feedback element and the integral feedback gain are set independently, it is extremely difficult to optimize the operation of the entire system, and it is necessary to repeat trial and error. . Furthermore, since the model itself is a straight-line running model, a large error occurs when the radius of curvature is small or when the target trajectory changes frequently, which may disturb the running stability.
[0011]
Therefore, the present invention has been made in view of the above-described circumstances, and even when a limiter process is performed by an integration processing unit that causes a vehicle to travel along a reference traveling line, the vehicle is stably placed on the reference traveling line. It is an object of the present invention to provide an automatic steering device that can be followed.
[0012]
[Means for Solving the Problems]
In order to solve the above-described problem, an automatic steering device according to the present invention includes a relative position detection unit that detects a relative position of a vehicle in a lateral direction with respect to a reference traveling line, and a target that is set in accordance with a detection result of the relative position detection unit. In an automatic steering apparatus including target steering torque calculating means for calculating a steering torque, and steering angle generating means for generating a steering angle for a steered wheel of the vehicle based on the target steering torque, the target steering torque calculating means is The curvature of the road on which the vehicle is traveling is estimated by the road curvature estimating means, and the traveling state of the vehicle is estimated by the traveling state estimating means based on the detection result of the relative position detecting means. A stabilization control torque for stabilizing the vehicle with reference to a reference traveling line of the road curvature obtained by the road curvature estimating means based on a running state of the vehicle; Calculating a deviation amount of an actual traveling line with respect to the reference traveling line based on the relative position detected by the relative position detecting means, and causing the vehicle to follow the reference traveling line based on the deviation amount. The reference running line following torque is calculated by the reference running line following torque calculating means, and the target steering torque is calculated by adding the stabilization control torque and the reference running line following torque by the adding means.
[0013]
That is, the reference traveling line following torque for following the reference traveling line obtained as the predetermined road curvature and the stabilization control torque for stabilizing the vehicle based on the reference traveling line can be individually set. . Specifically, a value of the stabilization control torque is set based on a change in the reference traveling line following torque.
[0014]
【The invention's effect】
According to the present invention, by individually setting the reference traveling line following torque and the stabilization control torque, it is possible to suppress a sudden change in torque and a change in traveling position.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 6 are views showing an embodiment of the present invention.
FIG. 1 is a plan view showing a schematic configuration of a vehicle 1 on which an automatic steering device is mounted. First, the configuration shown in FIG. 1 will be described. In this vehicle 1, the driver basically steers the steering wheel 2 to steer the front wheels 3L and 3R as steered wheels in the same manner as a normal vehicle. Corners are generated. That is, as shown in an enlarged view in FIG. 2, an upper end of a steering shaft 4 is integrally connected to the steering wheel 2 in the rotation direction, and a relay means such as a universal joint (not shown) is used at the lower end of the steering shaft 4. Connected to the input shaft to the power steering device 5. A pinion shaft is formed integrally with the input shaft by a power steering device 5, and the pinion shaft meshes with a rack 6 that advances and retreats in the vehicle lateral direction by the power steering device 5. Further, a torque sensor (not shown) for detecting, for example, torque generated in the steering system is provided between the input shaft to the power steering device 5 and the pinion shaft, and the power steering device 5 is detected by the torque sensor. A steering assist torque is applied to the rack 6 by controlling a hydraulic actuator or the like so as to reduce the steering torque.
[0016]
Left and right tie rods 7L, 7R are connected to both ends of the rack 6, and outer ends of the tie rods 7L, 7R are connected to knuckles that rotatably support the front wheels 3L, 3R. Therefore, when the driver steers the steering wheel 2, the steering force is converted into the forward / backward force of the rack 6 via the steering shaft 4 and the power steering device 5 and is input to both the tie rods 7L, 7R, and is applied to the front wheels 3L, 3R. A steering angle occurs. At this time, the steering assist torque is generated by the power steering device 5 so as to reduce the steering torque generated in the steering system, thereby reducing the burden on the driver.
[0017]
Further, the steering shaft 4 is provided with an automatic steering mechanism 10 for automatically generating a steering angle for the front wheels 3L, 3R. The automatic steering mechanism 10 includes an electric motor 10a, a reduction mechanism such as a worm gear for expanding the rotational force of the electric motor 10a and transmitting the torque to the steering shaft 4, an electromagnetic clutch for enabling the power of the electric motor 10a to be connected and disconnected, and the like. And a transmission mechanism 10b.
[0018]
As an operation of the automatic steering mechanism 10, when the driver selects manual steering, the electromagnetic clutch is disconnected so that the electric motor 10a does not become a load on the steering system. That is, when the automatic steering is selected, the electromagnetic clutch is connected, and the rotational force of the electric motor 10a is transmitted to the steering shaft 4 via the transmission mechanism. A drive current is supplied from a controller 20 mounted on the vehicle 1 to the electric motor 10a of the automatic steering mechanism 10, and a rotational torque having a direction and magnitude corresponding to the drive current is supplied to the electric motor 10a. Since it occurs at 10a, a steering angle is generated at the front wheels 3L and 3R as in the case of manual steering.
[0019]
In this embodiment, since the torque sensor of the power steering device 5 is disposed closer to the rack 6 than the connection position of the transmission mechanism of the steering shaft 4, the torque of the electric motor 10a is small. Also, it is possible to generate a steering angle on the front wheels 3L, 3R.
Further, the steering shaft 4 is provided with a steering angle sensor 14 that measures the rotational displacement and detects the actual steering angles of the front wheels 3L and 3R. The steering angle sensor 14 is configured by combining a gear mechanism for increasing the rotation of the steering shaft and an angle detection mechanism such as a rotary encoder or a potentiometer as a configuration capable of accurately detecting the actual steering angle. The output of the steering angle sensor 14 is supplied to the controller 20 as a steering angle detection signal.
[0020]
Further, the vehicle 1 is equipped with a CCD camera 17 for photographing a traveling path in front of the vehicle 1. The CCD camera 17 is configured to be able to photograph a road surface several meters to several tens of meters ahead of the vehicle 1. The image captured by the CCD camera 17 is supplied to the controller 20. The controller 20 detects a lateral relative position of the vehicle 1 with respect to a reference traveling line along the traveling path based on an image captured by the CCD camera 17.
[0021]
Specifically, the controller 20 extracts information (for example, a center line or a side line drawn on a road surface, a guide rail, or the like) that can be used as a reference traveling line from an image captured by the CCD camera 17. The controller 20 assumes a reference traveling line based on the extracted information (for example, the center of the traveling lane) and determines the reference traveling line and the reference line extending in the vehicle longitudinal direction through the center of gravity of the vehicle 1. The distance (difference) from a predetermined position (for example, a position 10 m in front of the vehicle) is determined by the relative position in the lateral direction of the vehicle 1 with respect to the reference travel line at the forward gazing point (hereinafter, the forward gazing point lateral displacement y _sr That. ).
[0022]
Further, the vehicle 1 is provided with a vehicle speed sensor 19 for detecting a vehicle speed by detecting, for example, the rotation speed on the output side of the transmission and the rotation speed of the wheels. The vehicle speed detection signal detected by the vehicle speed sensor 19 is supplied to the controller 20.
The controller 20 inputs a steering torque to the steering shaft 4 based on the supplied detection signals and an image captured by the CCD camera 17. That is, the controller 20 performs a predetermined calculation based on the supplied detection signals and the like to obtain a target steering torque required for the vehicle 1 to travel along the reference traveling line on the traveling road surface, and performs automatic steering. The current supplied to the electric motor 10 a of the mechanism 10 is controlled to input the target steering torque to the steering shaft 4. As a result, a steering angle is generated for the front wheels 3L and 3R, which are the steered wheels of the vehicle, according to the target steering torque.
[0023]
Here, although not shown, the controller 20 is configured to include an interface circuit such as an A / D converter, a D / A converter, a memory device such as a ROM or a RAM, or a microcomputer.
Next, the automatic steering system will be described in more detail. Here, an automatic steering system using an observer will be described. FIG. 3 shows a configuration of a control system of the automatic steering system (a configuration in the controller 20), and basic processing and the like will be described with reference to FIG.
[0024]
In FIG. 3, reference numeral 110 denotes an observer, and 121 denotes a regulator gain.
Observer 110 is constructed as a Kalman filter. The observer 110 has matrices A, B, and C and a gain L, and includes adders 111 and 112. Note that s shown in the observer 110 is a Laplace operator, and z is an estimated value of the state quantity x.
[0025]
With such a configuration, the controller 20 controls the steering torque u of the vehicle 1. That is, the observer 110 has the steering torque u and the forward fixation point lateral displacement y. _sr Is supplied to the observer 110, the steering torque u and the forward fixation point lateral displacement y _sr A state quantity vector (state quantity) x is estimated based on Here, the state quantity vector x is a yaw rate γ, a relative yaw angle φ with respect to the traveling lane. _r , Relative lateral displacement y to the traveling lane _cr , Relative lateral speed y 'to the driving lane _cr , Steering angle δ _f And steering angular velocity δ ' _f It is.
[0026]
The matrices A, B, and C are matrices determined from the model of the vehicle 1. First, the vehicle model is represented by a general two-wheel model as shown in FIG. The meaning of each symbol in FIG. 4 is as follows.
β: body side slip angle, C _f : Front wheel cornering power (for two wheels), C _r : Rear wheel cornering power (for two wheels), m: vehicle weight, I: yaw moment of inertia, δ _f : Front wheel actual steering angle, V: vehicle speed, l _f : Distance between center of gravity and front wheel, l _r : Distance between center of gravity and rear wheel, F _f : Front wheel cornering force, F _r : Rear wheel cornering force
The equation of motion of this model is as shown in the following equation (1).
[0027]
(Equation 1)

[0028]
When the amount of change in the inclination of the tangent to the target track is defined by the road curvature ρ, the change in the yaw angle of the vehicle relative to the target track per unit time, that is, the relative yaw rate φ ′ to the target track _r Is
[0029]
(Equation 2)

[0030]
And the relative lateral velocity y ′ _cr Is
[0031]
[Equation 3]

[0032]
Therefore, the following equations (4) and (5) are obtained by eliminating and rearranging the sideslip angle and the sideslip angular velocity from the above equation (1).
[0033]
(Equation 4)

[0034]
(Equation 5)

[0035]
Also, the lateral displacement y of the vehicle 1 in the lateral direction ahead of the reference traveling line _sr Is the distance in front of the vehicle at the forward fixation point _s [M], relative lateral displacement y from the target track (traveling lane) _cr , Relative yaw angle φ _r And the road curvature ρ, the following equation (6) can be used.
[0036]
(Equation 6)

[0037]
On the other hand, the equation of motion of the steering system in the automatic steering apparatus shown in FIG. 2 can be described as follows.
[0038]
(Equation 7)

[0039]
Where: ζ: trail length of the vehicle, K _T : Torque coefficient of steering actuator, N _s : Torque transmission ratio from steering actuator to steering system, C _s The damping coefficient of the steering system And, as in the above equations (4) and (5), the side slip angle β and the side slip angular velocity β ′ are eliminated and rearranged to obtain the following equation (8).
[0040]
(Equation 8)

[0041]
By newly formulating the equations (4) to (6) and (8) and adding the road curvature to the state variables and expressing them in a matrix, the vehicle model in a curved running state is described as the following equation (9). it can.
[0042]
(Equation 9)

[0043]
Using a matrix L for the dynamic system
[0044]
(Equation 10)

[0045]
Is performed to calculate the state variable vector z. Assuming that the deviation between the calculated state variable vector z and the true vehicle state vector x is e, the following equation (11) is obtained from the equations (9) and (10).
[0046]
[Equation 11]

[0047]
When the matrix L is determined so that the real parts of all eigenvalues of the transition matrix A-LC become negative, the following equation (12) is obtained.
[0048]
(Equation 12)

[0049]
Thus, an arbitrary initial value e (t ₀ ), The deviation vector e between the previously calculated state variable vector z and the true vehicle state quantity vector x becomes 0 after a sufficient time has elapsed, and the state variable vector z and the true vehicle state quantity Since it matches the vector x, the state quantity of the vehicle can be correctly detected.
Here, the above equation (10) indicates an observer, and a solution using such an observer is a technique often used for estimating the state of a dynamic system.
[0050]
On the other hand, considering process noise w and observation noise (sensor noise) n to the system, the matrix expression of the system can be described as the following equation (13).
[0051]
(Equation 13)

[0052]
Then, similarly to the observer described above, the deviation vector e can be obtained as the following equation (14).
[0053]
[Equation 14]

[0054]
Here, when it is assumed that the process noise w and the sensor noise n are normal white noises, a matrix L obtained to minimize the estimation error e becomes a Kalman filter, which is often used for state estimation of a dynamic system. Used.
Incidentally, the process noise w includes a continuous noise that is not strictly normal white noise, such as a moment component in the yaw direction or a lateral force component in the lateral direction caused by a cross wind or a road surface cant (one-sided gradient). Due to disturbances and modeling errors such as vehicle parameter errors, the state estimation value may not converge to the true value. As a result, there is a possibility that steady positional deviation may occur with simple state feedback control using only the regulator 121 shown in FIG. In such a case, the vehicle is steered in a direction deviating from the reference traveling line, and the driver is likely to feel a strong sense of discomfort.
[0055]
On the other hand, the controller 20 according to the present embodiment has the following configuration. FIG. 5 is a block diagram of the entire system to which the present invention is applied, including the basic functional configuration (the configuration shown in FIG. 3) of the controller 20.
That is, similarly to the controller 20 shown in FIG. 3, the controller 20 shown in FIG. _s (In FIG. 3, K ₀ ). The observer 110 also has the matrices A, B, and C and the gain L determined by the method described above, and includes the adders 111 and 112. Here, s shown in the observer 110 is a Laplace operator, z is an estimated value of the state quantity x, and Cz is an estimated value of the observation value vector y.
[0056]
Here, the details of the controller 20 in the present embodiment will be further described with reference to FIG. _sr And reference traveling line y _ref 123 that obtains a deviation Δy from the reference line, and a reference traveling line following torque u to be generated in the vehicle 1 based on the deviation Δy obtained by the adder 123. ₂ And a reference traveling line following torque generating unit 130 for calculating _s Stabilizing control torque generator (K _s ) 124 and the reference traveling line following torque u calculated by the reference traveling line following torque generator 130. ₂ And stabilization control torque generator (K _s ) 124 stabilization control torque u calculated _s And an adder 122 that obtains a target steering torque u by adding
[0057]
The reference traveling line following torque generating section 130 includes an accumulating section 140 and a gain K ₂ And a multiplication unit 131 for multiplying by
The integrating unit 140 is configured as shown in FIG. The accumulating unit 140 calculates a forward fixation point lateral displacement y, which is an output value from the adding unit 123. _sr And reference traveling line y _ref Is multiplied by the sampling time T, the integrated value obtained one sampling time ago by the integrating unit 140 is added to the value, and the limit processing unit 141 performs a predetermined limit process to calculate the latest integrated value. I do.
[0058]
Note that q in the integrating section 140 ^-1 Is a shift operator, and converts the input signal into q ^-1 Output one sampling time later. The upper limit value and the lower limit value of the integrated value used in the limit processing unit 141 are determined based on the reference traveling line following torque u. ₂ Is determined to be within the range of predetermined upper and lower limits.
The reference traveling line following torque generating section 130 multiplies the integrated value calculated by the integrating section 140 with the gain K ₂ And the reference traveling line following torque u ₂ Get. Note that the gain K of the multiplication unit is ₂ The selection of the value of will be described later in detail.
[0059]
Stabilization control torque generator (K _s ) 124 is a stabilization control torque u for stabilizing the traveling state of the vehicle around the reference traveling line given by the road curvature ρ. _s Is calculated. FIG. 8 shows a specific configuration thereof.
The state quantity z estimated by the observer 110 is input to the stabilization control torque generator 124, and the stabilization control torque generator 124 has two types of regulator gains K ₀ , K ₁ Each is multiplied by its state quantity z and correspondingly the first and second stabilization control torques u ₀ , U ₁ Is calculated. Note that the regulator gain K ₀ , K ₁ The selection of the value of _s The selection of the value of will be described later in detail.
[0060]
The stabilization control torque generator 124 outputs the reference traveling line following torque u. ₂ The first stabilization control torque u depending on whether or not ₀ And the second stabilization control torque u ₁ And the first stabilization control torque u ₀ And the second stabilization control torque u ₁ And the stabilization control torque u _s Is output as Here, the first stabilization control torque u ₀ Is the second stabilization control torque u ₁ Is smaller than the reference traveling line following torque u. ₂ During the limit processing operation, the first stabilization control torque u ₀ Stabilizing control torque u _s Is output as
[0061]
As described above, the stabilization control torque generator (K _s ) 124 to stabilize control torque u _s And the stabilization control torque u _s Is a value for correcting a small deviation around the reference traveling line with the road curvature being ρ. And, this stabilization control torque u _s Is input to the adder 122. In the adder 122, the stabilization control torque u _s And the reference traveling line following torque u from the reference traveling line following torque generator 130. ₂ Is added to obtain a target steering torque u.
[0062]
Here, the gain K of the integrating section 130 ₂ And regulator gain K _s (Regulator gain K ₀ , K ₁ ) Will be described.
Gain K ₂ Is a gain having such a characteristic that as the value is increased, the speed of following the reference traveling line is increased. Therefore, the gain K ₂ Is the lateral displacement y of the forward fixation point _sr And reference traveling line y _ref Even if the integrated value of the deviation Δy slightly changes from the reference traveling line following torque u ₂ Will make a big change. As a result, for example, the forward fixation point lateral displacement y _sr Reference traveling line following torque u which is sensitive to the noise component included in the detection result ₂ Is calculated, and the movement of the steering system may become awkward.
[0063]
Also, the regulator gain K _s Gain K compared to ₂ Is too large, the stabilization control torque u for stabilizing the vehicle based on the reference traveling line _s Is relatively reduced. As a result, the forward fixation point lateral displacement y _sr And reference traveling line y _ref And the deviation Δy from the reference traveling line following torque u ₂ Becomes dominant, and the overshoot amount with respect to the reference traveling line increases. As a result, at the moment when the vehicle passes on the reference traveling line, a control torque in a direction deviating from the reference traveling line remains, which is not preferable in terms of vehicle running stability or driver's steering feeling. May occur.
[0064]
Conversely, the gain K ₂ Is too small, the running stability is relatively improved, but the following speed is reduced. As a result, a steering torque is calculated that resists the vehicle from moving toward the target trajectory even though it has not yet reached the target trajectory. there is a possibility.
From the above, the gain K ₂ And regulator gain K _s (Regulator K ₀ , K ₁ ) Are not individually set as arbitrary values, but the gain K ₂ And regulator gain K _s Are determined in such a combination that they cooperate well. For example, the dynamic characteristics in a state where the automatic steering control is performed on the vehicle 1 are sufficiently checked by experiments and simulations, and the dynamic characteristics are appropriately selected in consideration of the dynamic characteristics. For example, the gain K ₂ And regulator gain K _s The optimum combination with the value of is determined by the following method.
[0065]
For example, in the configuration shown in FIG. ₀ Is known as a method of determining the optimal regulator from a regulator that minimizes the next evaluation function J corresponding to the above equation (9).
[0066]
(Equation 15)

[0067]
Here, the response of the system can be adjusted by adjusting the matrices Q and R, and the stabilization control torque u is calculated by the following equation (16). ₀ Can be calculated.
[0068]
(Equation 16)

[0069]
By applying such a method, the apparatus shown in FIG. _sr And reference traveling line y _ref The following equation (17) can be obtained when the integral value of the deviation Δy from the above is h.
[0070]
(Equation 17)

[0071]
An optimal regulator that minimizes the evaluation function J shown in the following equation (18) may be calculated in such an extended system.
[0072]
(Equation 18)

[0073]
Where the matrix q _h , Q ′, and R ′, the response of the system can be adjusted, and the target steering torque u can be calculated by the following (19).
[0074]
(Equation 19)

[0075]
Even in this case, it is necessary to sufficiently confirm the dynamic characteristics in the state where the automatic steering control is performed on the vehicle 1 by experiments and simulations, and to appropriately select the dynamic characteristics in consideration of the dynamic characteristics. However, actually, the speed following the reference traveling line is represented by a matrix q _h If the stability of the vehicle at that time seems to be insufficient, it is often the case that a desired response can be obtained only by gradually modifying the elements of the matrix Q 'to larger values.
[0076]
FIG. 9 shows a processing procedure of the controller 20. The controller 20 executes this processing in synchronization with a predetermined sampling clock.
When the automatic steering control is executed, first, in step S1, the controller 20 controls the steering angle detection signal δ from the steering angle sensor 14. _f , The vehicle speed detection signal V from the vehicle speed sensor 19 and the image from the CCD camera 17 are read.
[0077]
Since the vehicle speed detection signal V is information necessary for determining the elements of the matrices A, B, and C of the observer 110, the vehicle speed detection signal V is taken into the matrices A, B, and C as the vehicle speed V.
Subsequently, in step S2, the controller 20 sets the forward gazing point lateral displacement y based on the image read in step S1. _sr Is detected.
[0078]
Subsequently, in step S3, the controller 20 performs a calculation for estimating the actual vehicle state quantity x by executing a calculation (formula (10)) based on the observer 110, and outputs a vehicle state estimation vector z. .
Subsequently, in step S4, the controller 20 sets the vehicle state quantity estimation vector z obtained in step S3 and K ₀ , K ₁ Stabilizing control torque u having two different damping characteristics based on ₀ , U ₁ (Obtained by the above (Equation 19)). That is,
u ₀ = -K ₀ z, u ₁ = -K ₁ z
Get.
[0079]
Subsequently, in step S5, the controller 20 controls the forward gazing point lateral displacement y detected in step S2. _sr And reference traveling line y _ref , And a deviation K is added to the integrated value. ₂ Is multiplied by the reference traveling line following torque u ₂ Is calculated.
In this step S5, the controller 20 sets the reference traveling line following torque u ₂ To a predetermined upper limit or lower limit, and the lateral displacement y _sr And reference traveling line y _ref The limit processing is also performed on the integrated value of the deviation Δy from. Then, the limit flag is set at the time of the limit. By performing the limit processes in this manner, the absolute value of the deviation integral value is prevented from increasing any more. That is, the reference traveling line following torque u ₂ The lateral displacement y at the time when _sr And reference traveling line y _ref Is the upper limit or the lower limit.
[0080]
Subsequently, in step S6, the controller 20 sets the reference traveling line following torque u obtained in step S5. ₂ It is determined whether or not is subjected to limit processing. That is, it is determined whether or not the limit flag is set, and the reference traveling line following torque u is determined. ₂ It is determined whether or not is subjected to limit processing. Here, the controller 20 determines the reference traveling line following torque u. ₂ Has been processed, the process proceeds to step S7, where the reference traveling line following torque u ₂ If has not been subjected to the limit processing, the process proceeds to step S8.
[0081]
In step S7, the controller 20 controls the first stabilization control torque u ₀ Stabilizing control torque u _s To be determined. On the other hand, in the controller 8, the controller 20 controls the second stabilization control torque u ₁ Stabilizing control torque u _s To be determined. As described above, by the steps S7 and S8, the controller 20 sets the reference traveling line following torque u ₂ The two types of stabilization control torques u depend on whether or not ₀ , U ₁ To stabilize control torque u _s Is determined.
[0082]
Subsequently, in step S9, the controller 20 controls the stabilization control torque u _s And reference traveling line following torque u ₂ Is added to obtain the target steering torque u. Here, for example, processing is performed so that the controlled steering torque changes smoothly.
Subsequently, in step S10, the controller 20 performs an actuator driving process as an output process of the target steering torque u obtained in step S9. That is, the controller 20 controls the electric current to the electric motor 10a of the automatic steering mechanism 10 and inputs the target drive torque to the steering shaft 4, so that the front wheels 3L and 3R of the vehicle are steered to the target steering torque. Generate horns. As the control here, for example, a current applied to the electric motor 10a constituting the automatic steering mechanism is controlled by a PWM mechanism using an H-bridge circuit or the like, and a target steering torque u is input to the steering system.
[0083]
When the process in step S10 ends, the current process ends. Thereafter, after waiting for a predetermined sampling time to elapse, the processing is executed again from step S1.
The controller 20 performs the process according to the above procedure. By such processing, the vehicle follows the curved road by the action of the reference traveling line following torque, and stably travels along the curved road by the action of the stabilization control torque. become.
[0084]
Next, the effects will be described.
As described above, the reference traveling line following torque u ₂ To a predetermined upper limit or lower limit, and a lateral displacement y _sr And reference traveling line y _ref By performing a limit process also on the integrated value of the deviation Δy from the above (step S5), the reference traveling line following torque u ₂ Is suppressed, whereby the generation of an excessive target steering torque u can be suppressed.
[0085]
Thus, for example, even when the driver suddenly stops the steering intervention from a state where the reference traveling line is not easily reached due to the driver's steering intervention, the reference traveling line following torque u ₂ A situation in which the steering torque is still input even after passing the reference traveling line due to the influence of the residual component can be prevented. Similarly, when strong disturbance suddenly decreases or when the direction of the disturbance changes suddenly, or when the position of the reference traveling line is greatly changed, no extra vehicle behavior occurs. The vehicle 1 can run.
[0086]
While performing the limit processing has the above effects, when the limit processing is operating, the reference trajectory is calculated regardless of the change in the target trajectory in the direction that increases the reference running line following torque. Since the line following torque becomes a constant value, the feedback gain of the offset torque is equivalently reduced. This is because the reference running line following torque is maintained at a constant value despite the fact that the integral value is originally increasing, so that the gain decreases while the limit processing is operating. This is because In such a case, the attenuation of the entire control system is excessively strong. In other words, the action of keeping the posture of the vehicle at the current state by the state feedback acts excessively, and control for hindering movement to the reference traveling line is performed.
[0087]
In response to such a situation, the stabilization control torque u _s Can be set independently of the reference traveling line following system, and the reference traveling line following torque u ₂ Stabilization control torque u according to the change of _s , The reference traveling line following torque u ₂ It is possible to suppress a sudden change in torque and a change in traveling position that occur when the restriction on the system constantly acts on the system. Specifically, the reference traveling line following torque u ₂ When the limit processing is activated, the stabilization control torque u _s Is also reduced, that is, the regulator gain K _s (The feedback gain of the vehicle state quantity) is changed to a small value (in step S7, the regulator gain K _s Regulator gain K ₁ Is selected), the damping force of the system is relatively reduced, and the over-damped state of the reference traveling line following system is eliminated. By doing so, the moving speed of the vehicle 1 can be made appropriate.
[0088]
As described above, at the time of the operation of the limiter process, by changing the state feedback control for stabilizing the vehicle state, it is possible to eliminate the deterioration of the speed of following the target trajectory, and to improve the followability to the target trajectory. It is possible to achieve both running stability.
Also, the stabilization control torque u _s Is adjusted or corrected by a plurality of regulator gains K ₀ , K ₁ , Ie, the reference traveling line following torque u ₂ The regulator gain K is set so that the over-attenuation state of the reference traveling line following system caused by the operation of the limit processing does not occur. _s , It is possible to construct a system having a simple configuration that can achieve both the followability to the target trajectory and the running stability.
[0089]
Further, since the Kalman filter is used as the observer 110 as described above, more suitable calculation can be performed. That is, since the number of elements of the observer gain is a combination of the number of outputs (the number of sensors) and the state variables (the number of outputs (the number of sensors) × the state variables), it is stable (all real parts of the observer poles are negative). In general, it is not easy to design an observer that has good estimation accuracy and can effectively remove the noise component of the sensor. On the other hand, when designing a Kalman filter, the variance of sensor noise and the process noise acting on the vehicle are required as design parameters. However, since these can be checked in advance, the observer gain can be determined almost without trial and error. It is possible to design For this reason, as described above, by using the Kalman filter as the observer 110, it is possible to perform more suitable calculation.
[0090]
The embodiment of the invention has been described. However, the present invention is not limited to being realized as the above-described embodiment.
That is, in the above-described embodiment, the relative position (lateral displacement) of the vehicle 1 with respect to the reference traveling line is detected based on the image captured by the CCD camera 17, but the invention is not limited to this. For example, the lateral displacement may be detected by a known induction cable system or a known magnetic marker system. Alternatively, as in the technique disclosed in Japanese Patent Application Laid-Open No. 3-293411, the distance between a guardrail installed along a traveling path and a vehicle is measured using ultrasonic waves, and a reference is determined from the measured distance. The lateral position of the vehicle with respect to the traveling line may be detected. Further, a plurality of methods may be combined.
[0091]
Further, in the above-described embodiment, the front wheels 3L and 3R are steered, but the rear wheels may be steered, or both the front wheels and the rear wheels may be steered. .
Further, in the above-described embodiment, only the steering angle can be automatically controlled, but the present invention is not limited to this. For example, an actuator capable of independently controlling the braking and driving of four wheels is provided, and the state of the actuator can be controlled by a control signal supplied from the controller 20, so that the yaw moment of the vehicle can be arbitrarily controlled. It may be.
[0092]
In the above-described embodiment, the first stabilization control torque u selected at the time of the limiter processing operation is set. ₀ Is not limited to one type, and may be plural types. Specifically, a plurality of regulator gains are prepared so as to gradually decrease as the lateral movement speed of the vehicle 1 increases, and a plurality of first stabilization control torques u are prepared using the plurality of regulator gains. ₀ To get In this case, the first stabilization control torque u is changed by changing the regulator gain in accordance with the moving speed in the lateral direction. ₀ (Stabilization control torque u _s ), A smoother behavior of the vehicle can be obtained although the moving speed is slightly reduced. In other words, when the regulator gain is switched in a state where the target traveling line following torque is in the limit processing, it is possible to make detailed settings in consideration of the fluctuation of the target steering torque and the lateral moving speed of the vehicle due to the gain switching. , Which makes it possible to keep the vehicle running smoothly.
[0093]
Here, the vehicle state is defined as a lateral moving speed of the vehicle 1, a regulator gain is determined according to the moving speed, and a first stabilization control torque u is determined. ₀ However, the regulator gain is adjusted according to other vehicle conditions, and the first stabilization control torque u ₀ May be changed.
At the moment when the vehicle crosses on the reference traveling line after the gain switching, or when it is expected that the vehicle crosses on the reference traveling line, the reference traveling line following torque u _s Is set to 0 and the reference traveling line is corrected at the same time. Specifically, the reference traveling line that is the control target is corrected to the traveling line that is currently traveling. As a result, the amount of overshoot (the amount of overshoot) of the vehicle with respect to the target track can be reduced as much as possible, and a more desirable running state can be maintained.
[0094]
Further, in the above-described embodiment, the specific configuration of the integrating unit 140 is shown in FIG. 7, but the present invention is not limited to this. For example, the integrating unit 140 may be configured as shown in FIG.
In this case, the integrating unit 140 calculates the forward fixation point lateral displacement y from the adding unit 123. _sr And reference traveling line y _ref , And the moving average of the deviation Δy before one sampling time is calculated, and the calculated value is multiplied by the sampling time T / 2. Then, the integrated value one sampling time ago is added to the value, and the limit processing unit 141 performs a predetermined limit process to calculate the latest integrated value.
[0095]
Note that q in the integrating section 140 ^-1 Is a shift operator, and the input signal is q ^-1 Output one sampling time later. The upper limit value and the lower limit value of the integrated value used in the limit processing unit 141 are based on the reference traveling line following torque u. ₂ Is determined to be within the range of predetermined upper and lower limits.
Then, the reference traveling line following torque generating unit 130 multiplies the integrated value calculated by the integrating unit 140 with the gain K ₂ And the reference traveling line following torque u ₂ Get.
[0096]
The calculation accuracy of the integrating unit 140 shown in FIG. 10 is different from that of the integrating unit 140 shown in FIG. That is, the integrating unit 140 shown in FIG. 7 has a configuration using an approximate calculation by a zero-order hold circuit that considers only the value at the time of sampling, and the integrating unit 140 shown in FIG. Is configured using an approximation calculation based on the trapezoidal rule in consideration of The calculation by the integration unit 140 shown in FIG. 7 and the calculation by the integration unit 140 shown in FIG. 10 are substantially the same operation, but there is a difference in the obtained accuracy. For example, in the case where there is a restriction that the sampling time T cannot be made too small, the calculation accuracy is higher by using the trapezoidal rule, and a smoothly changing result can be obtained. In this case, the integration unit shown in FIG. It is better to use 140. As described above, it is also possible to use differently according to the use situation and the like.
[0097]
In the above-described embodiment, the CCD camera 17 and the processing in step S1 constitute relative position detecting means for detecting a relative position of the vehicle in the lateral direction with respect to the reference traveling line. Section 130, stabilization control torque generation section (K _s ) 124 and adders 122 and 123 constitute a target steering torque calculating means for calculating a target steering torque according to the detection result of the relative position detecting means, and the automatic steering mechanism 10 controls the vehicle based on the target steering torque. It constitutes a steering angle generating means for generating a steering angle for the steered wheels.
[0098]
Further, the observer 110, the reference traveling line following torque generator 130, and the stabilization control torque generator (K _s ) 124 and the adders 122 and 123, the observer 110 estimates a traveling state of the vehicle based on a detection result of a road curvature estimating unit that estimates a curvature of a road on which the vehicle is traveling and a relative position detecting unit. A stabilizing control torque generator (K) _s ) 124 is a stabilization control torque for stabilizing the vehicle based on the reference running line of the road curvature obtained by the road curvature estimating means, based on the running state of the vehicle obtained by the running state estimating means. The reference travel line following torque generating unit 130 and the adder 123 form a control torque calculation unit, and calculate a deviation amount of the actual travel line from the reference travel line based on the relative position detected by the relative position detection unit. The reference traveling line following torque calculating means for calculating a reference traveling line following torque for causing the vehicle to follow the reference traveling line based on the amount is configured, and the adder 122 includes a stabilization control torque, a reference traveling line following torque, Is added to calculate a target steering torque.
[Brief description of the drawings]
FIG. 1 is a plan view of a vehicle according to an embodiment of the present invention.
FIG. 2 is a partially enlarged perspective view of a layer.
FIG. 3 is a diagram of a two-wheel model of a vehicle.
FIG. 4 is a block diagram showing a configuration of an automatic steering system using an observer modeled on a curved running state.
FIG. 5 is a block diagram illustrating a basic functional configuration of a controller according to the embodiment of the present invention.
FIG. 6 is a block diagram illustrating a configuration of a reference traveling line following torque generating unit according to the embodiment of the present invention.
FIG. 7 is a block diagram showing a configuration of an integrating section of the reference traveling line following torque generating section.
FIG. 8 is a block diagram illustrating a configuration of a stabilization control torque generating unit according to the embodiment of the present invention.
FIG. 9 is a flowchart illustrating a processing procedure of a controller according to the embodiment of the present invention.
FIG. 10 is a block diagram showing another configuration of the integrating section of the reference running line following torque generating section.
[Explanation of symbols]
1 vehicle
2 Steering wheel
3L, 3R front wheel (steering wheel)
10 Automatic steering mechanism
14 Steering angle sensor
17 CCD camera
19 Vehicle speed sensor
20 Controller
110 Observer (Kalman filter)
122,123 Adder
124 Stabilization control torque generator
130 Reference running line following torque generator
140 Accumulator

Claims (6)

Relative position detecting means for detecting a lateral relative position of the vehicle with respect to a reference traveling line; target steering torque calculating means for calculating a target steering torque in accordance with a detection result of the relative position detecting means; Steering angle generating means for generating a steering angle on the steered wheels of the vehicle,
The target steering torque calculating means, a road curvature estimating means for estimating a curvature of a road on which the vehicle is traveling, a running state estimating means for estimating a running state of the vehicle based on a detection result of the relative position detecting means, Stabilization control torque calculation for calculating a stabilization control torque for stabilizing the vehicle based on a reference running line of the road curvature obtained by the road curvature estimating means based on the running state of the vehicle obtained by the running state estimating means. Means for calculating a deviation amount of an actual traveling line with respect to the reference traveling line based on the relative position detected by the relative position detecting means, and causing the vehicle to follow the reference traveling line based on the deviation amount. A reference travel line following torque calculating means for calculating a reference travel line following torque; and adding the stabilization control torque and the reference travel line following torque to the target Automatic steering apparatus characterized by comprising an adding means for calculating the steering torque. 2. The stabilization control torque calculation means corrects the stabilization control torque in a decreasing direction when the reference travel line following torque calculation means limits the reference travel line following torque. Automatic steering device. The reference traveling line following torque calculating means calculates the reference traveling line following torque based on an integrated value of a deviation amount of an actual traveling line with respect to the reference traveling line,
When the deviation exceeds a predetermined value, the reference traveling line following torque calculation means performs at least one of a limit process that does not increase the integrated value of the deviation and a limit process that does not increase the reference traveling line following torque. 3. The automatic steering apparatus according to claim 2, wherein the stabilization control torque calculating means corrects the stabilization control torque in a decreasing direction. The road curvature estimating means and the traveling state estimating means are configured as observers for estimating a state quantity of a vehicle defined based on a reference traveling line that is a curved road,
The stabilization control torque calculating means calculates the stabilization control torque by multiplying a state gain of the vehicle estimated by the observer by a regulator gain,
4. The automatic steering apparatus according to claim 2, wherein the stabilization control torque calculation unit corrects the stabilization control torque in a decreasing direction by changing the regulator gain. 5. Until the reference running line following torque calculating means imposes a limit on the reference running line following torque, the stabilization control torque calculating means sets a regulator gain by which the state quantity of the vehicle estimated by the observer is multiplied according to the state of the vehicle. The automatic steering device according to claim 4, wherein the automatic steering device is changed by changing the position of the automatic steering device. The automatic steering device according to claim 4, wherein the observer is a Kalman filter.

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