JP4267976B2 - Electric power steering device - Google Patents

Description

【００４５】
図６（ａ）は正常時の３相電流を示し、横軸は電気角を示し、縦軸は３相電流を示す。曲線Ｃ１０は電流Ｉｕ、曲線Ｃ１１は電流Ｉｗを示す。図６（ｂ）は、正常時の２軸電流を示し、横軸は電気角を示し、縦軸は２軸電流を示す。曲線Ｃ１２はｄ軸電流Ｉｄ、曲線Ｃ１３はｑ軸電流Ｉｑを示す。図６（ｃ）は電流センサのオフセットずれ時の３相電流を示し、横軸は電気角を示し、縦軸は３相電流を示す。曲線Ｃ２０は電流Ｉｕ、曲線Ｃ２１は電流Ｉｗを示す。図６（ｄ）は、電流センサのオフセットずれ時の２軸電流を示し、横軸は電気角を示し、縦軸は２軸電流を示す。曲線Ｃ２２はｄ軸電流Ｉｄ、曲線Ｃ２３はｑ軸電流Ｉｑを示す。図６（ｅ）は電流センサのゲインずれ時の３相電流を示し、横軸は電気角を示し、縦軸は３相電流を示す。曲線Ｃ３０は電流Ｉｕ、曲線Ｃ３１は電流Ｉｗを示す。図６（ｆ）は、電流センサのゲインずれ時の２軸電流を示し、横軸は電気角を示し、縦軸は２軸電流を示す。曲線Ｃ３２はｄ軸電流Ｉｄ、曲線Ｃ３３はｑ軸電流Ｉｑを示す。この図より電流センサにオフセットずれが生じた場合は電気角１周期に対して１次の脈動、電流センサにゲインずれが生じた場合は電気角１周期に対して２次の脈動が検出されるｄｑ軸電流に現れることが分かる。
【００４６】
図７は、電動パワーステアリング装置での制御を説明する模式図である。電動パワーステアリング装置における制御は、トルクループ１０５と電流ループ１０６の２重の制御がなされている。すなわち、トルク制御部１０７で設定される目標電流に基づいて電流ループ１０６内の電流制御部１００によって駆動電圧が出力され、それにより、モータ１９が駆動される。その駆動するモータ１９のモータ電流を電流センサ２０６，２０７で検出し、検出電流を電流制御部１００にフィードバックさせている。この電流制御部１００、モータ１９、電流センサ２０６，２０７、電流制御部１００によって形成されるループが電流ループ１０６である。また、モータ１９の駆動によってギアボックス２４内のステアリング軸１２にアシストトルクがかかり、トルクセンサ２０によって検出されたトルク信号がトルク制御部１０７にフィードバックされる。このトルク制御部１０７、電流制御部１００、モータ１９、ギアボックス２４、トルクセンサ２０、トルク制御部１０７によって形成されるループがトルクループ１０５である。このように、電動パワーステアリング装置１０の制御は、モータ１９に流れる電流を検出している検出電流が目標電流と一致するように制御する電流ループ１０６と、操舵補助力を発生するために操舵トルクを検出して目標電流を指示するトルクループ１０５の２重の制御が働き、このうちトルクループ１０５は車速、操舵トルク、操舵速度等により制御の度合いを変化させている。
【００４７】
図７のように構成されている電動パワーステアリング装置１０の制御において、図６で示す電流センサ２０６，２０７の故障が生じた場合の各制御の動作について説明する。
【００４８】
電流センサ２０６，２０７が故障した場合、モータ１９内を流れる２軸電流が図６（ｂ）のように正常時の２軸電流のように流れているにもかかわらず、検出される２軸電流が図６（ｄ）と（ｆ）で示されるように、電流センサのオフセットずれ時、ゲインずれ時の２軸電流のように検出されてしまう。そして、この検出された電流が目標電流と一致するように制御が働く。
【００４９】
仮に目標電流がゼロの場合を考えると、検出される２軸電流は制御によってゼロとなる。このとき、モータ１９内を流れている２軸電流は故障による分だけの脈動が現れ、モータ１９を駆動している駆動電圧にも脈動分が現れる。モータ電流の脈動は、これに応じてモータ１９の発生するトルクも脈動させ、脈動するモータトルクがドライバーに違和感を感じさせたり、操舵できなくさせてしまう。
【００５０】
しかし、電動パワーステアリング装置１０には操舵トルクの脈動を低減させるような効果を持つトルク制御があることにより、操舵トルクに現れた脈動を打ち消すように目標電流が調整される。そこで、仮に操舵トルクに脈動が一切現れないような制御がなされた場合を考えると、モータ１９内を流れている電流も脈動がなくなり、このモータ１９を駆動している駆動電圧の脈動もなくなる。この場合、電流センサ２０６，２０７の故障分は検出電流の脈動として現れることになる。
【００５１】
このようなことから、電動パワーステアリング装置における電流センサ故障時の故障信号は図８に示すように電流制御とトルク制御の働き度合いによって駆動電圧と検出電流の両方に現れ、それらを合わせた分が電流センサの故障分になると考えられる。すなわち、図８の電流センサの故障している分の駆動電圧に現れる割合と検出電流に現れる割合は、図示するように、電流制御が強くなるほど、発生トルクを乱して検出電流を制御し、駆動電圧に現れる割合が大きくなり、逆に、トルク制御が強い場合には、検出電流を乱して発生トルクを制御し、検出電流に現れる割合が大きくなる。
【００５２】
このことに基づき、本発明では、駆動電圧および検出電流の両方に対して監視手段を設け、それらを合わせて故障検出を行うようにしている。ただし、駆動電圧と検出電流では単位が異なるため、単純な加算ができないことから、モータの抵抗値を用いて駆動電圧で検出された成分を電流の単位に換算して処理を行っている。ここで用いるモータの抵抗値は図９に示すような方法で算出され、初期値をモータの設計値、温度変化等に対応するため、保舵時でのｖｑ＝Ｒ×ｉｑが成立する条件において、この関係式から算出した値にローパスフィルタをかけて計測した値を用いている。すなわち、回路方程式は、（２）式で表され、
【００５３】
【数２】

【００５４】
保舵状態ではωｅ＝０，ＰＩｑ＝０よりＶｑ＝ＲＩｑであり、モータ抵抗値の算出のフローチャートは、図９で示すように、まず、Ｉｑ微分処理を行いＩｑの微分値を求め（ステップＳ１０）、Ｉｑローパスフィルタ処理を行いＩｑＬＰＦを求め（ステップＳ１１）、Ｖｑローパスフィルタ処理を行いＶｑＬＰＦを求め（ステップＳ１２）、回転速度がしきい値より小さく、Ｉｑの微分値がしきい値より小さく、ＶｑＬＰＦがしきい値より大きく、ＩｑＬＰＦがしきい値より大きいかどうか判断する（ステップＳ１３）。もし、これが満たされなければ、計算は終了し、満たされれば、Ｒ＝ＶｑＬＰＦ／ＩｑＬＰＦを計算し（ステップＳ１４）、ＲＬＰＦ＝ＲＬＰＦ処理（ステップＳ１５）を行い、終了する。
【００５５】
次に駆動電圧監視部１０１と検出電流監視部１０２の説明をする。駆動電圧監視部１０１は、いずれかの相の駆動電圧とモータ１９の回転角度から他の相の電圧を推定する電圧推定部と、他の相の駆動電圧と電圧推定部により推定される推定電圧を比較して駆動電圧の異常信号を生成する駆動電圧異常信号生成部とから成り、検出電流監視部１０２は、いずれかの相の検出電流とモータの回転角度から他の相の電流を推定する電流推定部と、他の相の検出電流と電流推定部により推定される推定電流を比較して検出電流の異常信号を生成する検出電流異常信号生成部とから成る。
【００５６】
図１０は、駆動電圧監視部１０１と検出電流監視部１０２を示し、駆動電圧監視部１０１は、２軸３相変換部２１３からのＵ相電圧を偏差演算部１０８に入力し、また、Ｕ相電圧を角度センサ２３からのモータ回転角度に基づく係数（ｓｉｎ（θ＋１２０°）／ｓｉｎθ）を掛ける演算部（電圧推定部）１０９を介して、偏差演算部１１０に出力する。また、２軸３相変換部２１３からのＷ相電圧を偏差演算部１１０に出力し、また、Ｗ相電圧に角度センサ２３からのモータ回転角度に基づく係数（ｓｉｎθ／ｓｉｎ（θ＋１２０°））を掛ける演算部（電圧推定部）１１１を介して偏差演算部１０８に出力する。偏差演算部１０８では、偏差信号を駆動電圧異常信号生成部１１２に出力する。また、偏差演算部１１０では、偏差信号を駆動電圧異常信号生成部１１２に出力する。
【００５７】
駆動電圧異常信号生成部１１２は、偏差演算部１０８，１１０からの偏差が所定値より小さければ、正常であることを判断し、正常値信号を故障検出部１０３に出力し、その偏差が所定値より大きければ、故障と判断し、故障信号（異常信号）、例えば１を故障検出部１０３に出力する。
【００５８】
検出電流監視部１０２は、電流センサ２０７からのＵ相電流を偏差演算部１１３に入力し、また、Ｕ相電流を角度センサ２３からのモータ回転角度に基づく係数（ｓｉｎ（θ＋１２０°）／ｓｉｎθ）を掛ける演算部（電流推定部）１１４を介して、偏差演算部１１５に出力する。また、電流センサ２０６からのＷ相電流を偏差演算部１１５に出力し、また、Ｗ相電流に角度センサ２１７からのモータ回転角度に基づく係数（ｓｉｎθ／ｓｉｎ（θ＋１２０°））を掛ける演算部（電流推定部）１１６を介して偏差演算部１１３に出力する。偏差演算部１１３では、偏差信号を検出電流異常信号生成部１１７に出力する。また、偏差演算部１１５では、偏差信号を検出電流異常信号生成部１１７に出力する。
【００５９】
検出電流異常信号生成部１１７は、偏差演算部１１３，１１５から出力される偏差が所定値より小さければ、正常であることを判断し、正常値信号を故障検出部１０３に出力し、その偏差が所定値より大きければ、故障と判断し、故障信号（異常信号）、例えば１を故障検出部１０３に出力する。
【００６０】
故障検出部１０３は、駆動電圧異常信号生成部１１２または検出電流異常信号生成部１１７から異常信号が出力されたとき故障と判断し、故障信号、例えば１を故障表示部１０４に出力する。
【００６１】
故障表示部１０４は、電流センサ２０６，２０７が故障かどうかを表示する装置であり、例えば、故障検出部１０３からの入力信号に基づいて点滅する発光ダイオードなどを設けたものである。その発光ダイオードは、故障検出部１０３からの信号がゼロのときには、点灯しない状態を保ち、故障検出部１０３からの入力が１のとき、点灯するようにすれば良い。それにより、発光ダイオードが点灯したとき、電流センサ２０６，２０７が故障と判断することができる。
【００６２】
図１１は、センサ故障検出のフローチャートである。舵角速度が２０ｄｅｇ／ｓより小さいかどうか判断する（ステップＳ２０）。舵角速度が２０ｄｅｇ／ｓより小さくないときは、リターンし再びステップＳ２０を実行する。舵角速度が２０ｄｅｇ／ｓより小さいときは、モータ回転角度θが０〜６０°、１８０〜２４０°の範囲にあるかどうか判断する（ステップＳ２１）。もし、この範囲にモータ回転角度がなければ、ステップＳ２２を実行する。もし、モータ回転角度θがこの範囲にあるならば、Ｖｕ＊＝Ｖｖ・（ｓｉｎθ／ｓｉｎ（θ−１２０°））を計算する（ステップＳ２３）。次にＩｕ＊＝Ｉｖ・（ｓｉｎθ／ｓｉｎ（θ−１２０°））を計算する（ステップＳ２４）。Ｖｗ＊＝Ｖｕ・（ｓｉｎ（θ＋１２０°）／ｓｉｎ（θ−１２０°））を計算し（ステップＳ２５），Ｉｗ＊＝Ｉｕ・（ｓｉｎ（θ＋１２０°）／ｓｉｎ（θ−１２０°））を計算し（ステップＳ２６）、Ｅｒｒ１＝（Ｖｕ−Ｖｕ＊）／Ｒ＋（Ｉｕ−Ｉｕ＊）とＥｒｒ２＝（Ｖｗ−Ｖｗ＊）／Ｒ＋（Ｉｗ−Ｉｗ＊）とを計算し（ステップＳ２７）、Ｅｒｒ＝Ｍａｘ（Ｅｒｒ１，Ｅｒｒ２）を計算し（ステップＳ２８）、そして故障判定する（ステップＳ２９）。
【００６３】
ステップＳ２１でＮｏならば、ステップＳ２２を実行し、θが６０〜１２０°、２４０〜３００°の範囲内にあるならば、Ｖｗ＊＝Ｖｕ・（ｓｉｎ（θ＋１２０°）／ｓｉｎθを計算し（ステップＳ３０）、Ｉｗ＊＝Ｉｕ・（ｓｉｎ（θ＋１２０°）／ｓｉｎθ）を計算し（ステップＳ３１）、Ｅｒｒ＝（Ｖｗ−Ｖｗ＊）／Ｒ＋（Ｉｗ−Ｉｗ＊）を計算し（ステップＳ３２）、故障判定をする（ステップＳ２９）、ステップＳ２２でＮｏならば、Ｖｕ＊＝Ｖｗ・（ｓｉｎθ／ｓｉｎ（θ＋１２０°））を計算し（ステップＳ３３）、Ｉｕ＊＝Ｉｗ・（ｓｉｎθ／ｓｉｎ（θ＋１２０°））を計算し（ステップＳ３４）、Ｅｒｒ＝（Ｖｕ−Ｖｕ＊）／Ｒ＋（Ｉｕ−Ｉｕ＊）を計算し（ステップＳ３５）、故障判定する（ステップＳ２９）。
【００６４】
このように、３相モータを正弦波通電で使用した場合の駆動電圧波形および電流波形は３相がそれぞれ１２０°ずつの位相差を持った正弦波となる。よってＵ相電流に対して１２０°分の位相を変更する係数を掛けてＷ相電流を推定した値と、検出されるＷ相電流を比較することで、センサにずれが生じているか否かの判定ができると考える。
【００６５】
ただし、推定するための係数はｓｉｎ（θ＋１２０°）／ｓｉｎ（θ）のようになり、θがゼロとなる角度では無限大の値となる等の問題があることからこれを回避するために、図１１に示すように角度により切り換えることで、推定する際の係数は１よりも小さい値となり、推定する際の誤差を低減することができる。
【００６６】
図１２は、他相推定によるセンサ故障量を示すグラフである。図１２（ａ）は、オフセットずれのときの電気角に対する３相電流の変化を示す。横軸は電気角を示し、縦軸は振幅を示す。曲線Ｃ４０はＵ相電流を示し、曲線Ｃ４１はＶ相電流を示し、曲線Ｃ４２はＷ相電流を示す。また、曲線Ｃ４３はＵ相推定電流を示し、曲線Ｃ４５はＷ相推定電流を示す。図１２（ｂ）は、電気角に対するずれ量を示すグラフである。図１２（ｃ）は、ゲインずれのときの電気角に対する３相電流の変化を示す。横軸は電気角を示し、縦軸は振幅を示す。曲線Ｃ５０はＵ相電流を示し、曲線Ｃ５１はＶ相電流を示し、曲線Ｃ５２はＷ相電流を示す。また、曲線Ｃ５３はＵ相推定電流を示し、曲線Ｃ５５はＷ相推定電流を示す。図１２（ｄ）は、電気角に対するずれ量を示すグラフである。
【００６７】
このように角度により推定相手を切り換えることで、図１２に示すようにずれ量が検出され、駆動電圧のずれ分と検出電流のずれ分をそれぞれ算出し、単位をそろえた上で合わせることで、電流センサのずれ量を検出している。このように検出されたずれをチェックし、ずれ量が閾値を越えた時間が規定時間連続した場合に故障であると判断するようになっている。
【００６８】
ただしこの手法では電圧・電流の位相が電気角に対して一致していることが前提となるが、操舵速度が速くなると、駆動電圧の位相が進んでしまうため、操舵速度が充分低い場合に限定して処理を行うようにしている。
【００６９】
次に、本発明の第２の実施形態に係る電動パワーステアリング装置を説明する。第２の実施形態では、図１で示した電動パワーステアリング装置の制御装置２２における駆動電圧監視部と検出電流監視部を後に述べるように変更した装置である。他の構成要素は同様なので説明を省略する。
【００７０】
第２の実施形態における駆動電圧監視部と検出電流監視部の説明をする。図１３に示すように駆動電圧監視部１２０は、電流センサ２０６，２０７の配置されている各々の相の駆動電圧の１周期分のデータの最大値および最小値を検出する電圧最大値最小値検出部１２１，１２２と、電圧最大値最小値検出部１２１，１２２により検出された最大値および最小値から駆動電圧の異常信号を生成する駆動電圧異常信号生成部１２３とから成り、検出電流監視部１２４は、電流センサ２０６，２０７により検出される各々の相の検出電流の１周期分のデータの最大値および最小値を検出する電流最大値最小値検出部１２５，１２６と、電流最大値最小値検出部１２５，１２６により検出された最大値および最小値から検出電流の異常信号を生成する検出電流異常信号生成部１２７と、から成る。
【００７１】
駆動電圧監視部１２０は、２軸３相変換部２１３からのＵ相電圧を電圧最大値最小値検出部１２１に入力し、駆動電圧の１周期分のデータの最大値および最小値を検出し、それらの値を駆動電圧異常信号生成部１２３に出力する。駆動電圧異常信号生成部１２３では、最大値最小値を用いてオフセットずれと振幅ずれを算出し、オフセットずれの値が所定値以上の時、あるいは、振幅ずれの値が所定値以上の時には異常信号を故障検出部１０３に出力する。また、２軸３相変換部２１３からのＷ相電圧を電圧最大値最小値検出部１２２に入力し、駆動電圧の１周期分のデータの最大値および最小値を検出し、そららの値を駆動電圧異常信号生成部１２３に出力する。駆動電圧異常信号生成部１２３では、最大値最小値を用いてオフセットずれと振幅ずれを算出し、オフセットずれの値が所定値以上の時、あるいは、振幅ずれの値が所定値以上の時には異常信号を故障検出部１０３に出力する。
【００７２】
検出電流監視部１２４は、電流センサ２０７からのＵ相電流を電流最大値最小値検出部１２５に入力し、検出電流の１周期分のデータの最大値および最小値を検出し、それらの値を検出電流異常信号生成部１２７に出力する。検出電流異常信号生成部１２７では、最大値最小値を用いてオフセットずれと振幅ずれを算出し、オフセットずれの値が所定値以上の時、あるいは、振幅ずれの値が所定値以上の時には異常信号を故障検出部１０３に出力する。また、電流センサ２０６からのＷ相電流を電流最大値最小値検出部１２６に入力し、電流センサ２０６の１周期分のデータの最大値および最小値を検出し、それらの値を検出電流異常信号生成部１２７に出力する。検出電流異常信号生成部１２７では、最大値最小値を用いてオフセットずれと振幅ずれを算出し、オフセットずれの値が所定値以上の時、あるいは、振幅ずれの値が所定値以上の時には異常信号を故障検出部１０３に出力する。
【００７３】
図１４は、駆動電圧異常信号生成部１２３と検出電流異常信号生成部１２４での最大値・最小値からの電流センサ２０６，２０７のオフセットずれとゲインずれの検出の原理を示すグラフである。図１４（ａ）は、オフセットずれでの電流、あるいは電圧の変化を示す。曲線Ｃ６０はＵ相電流あるいは電圧であり、曲線Ｃ６１はＷ相電流あるいは電圧である。横軸は電気角である、縦軸は振幅を示す。オフセットずれはＵ相電流あるいは電圧の最大値ＭＡＸ１０と最小値ＭＩＮ１０の中央値のゼロからのずれとして求められる。また、オフセットずれはＷ相電流あるいは電圧の最大値ＭＡＸ１１と最小値ＭＩＮ１１の中央値のゼロからのずれとして求められる。図１４（ｂ）は、ゲインずれでの電流、あるいは電圧の変化を示す。曲線Ｃ７０はＵ相電流あるいは電圧であり、曲線Ｃ７１はＷ相電流あるいは電圧である。横軸は電気角である、縦軸は振幅を示す。ゲインずれはＵ相電流あるいは電圧の最大値ＭＡＸ２０と最小値ＭＩＮ２０から求まる振幅のＷ相電圧あるいは電流の最大値ＭＡＸ２１と最小値ＭＩＮ２１から求まる振幅の差として求められる。
【００７４】
故障検出部１０３は、駆動電圧異常信号生成部１２３または検出電流異常信号生成部１２７から異常信号が入力されたときは故障と判断し、故障信号、例えば１を故障表示部１０４に出力する。それにより、故障表示部１０４の発光ダイオードが点灯したとき、電流センサ２０６，２０７が故障と判断することができる。
【００７５】
図１５は、センサ故障検出のフローチャートである。舵角速度が５ｄｅｇ／ｓ以上かどうか判断する（ステップＳ４０）。舵角速度が５ｄｅｇ／ｓより小さいときは、リターンしステップＳ４０を実行する。舵角速度が５ｄｅｇ／ｓ以上のときは、電気角１周期分データ収集したかどうか判断する（ステップＳ４１）。もし、１周期分のデータを収集していない場合は、継続してＵ相電圧Ｖｕの最大値ＶｕＭＡＸと最小値ＶｕＭＩＮを検出し（ステップＳ４２）、Ｗ相電圧Ｖｗの最大値ＶｗＭＡＸと最小値ＶｗＭＩＮを検出し（ステップＳ４３）、Ｕ相電流Ｉｕの最大値ＩｕＭＡＸと最小値ＩｕＭＩＮを検出し（ステップＳ４４）、Ｗ相電流Ｉｗの最大値ＩｗＭＡＸと最小値ＩｗＭＩＮを検出する（ステップＳ４５）。ステップＳ４１で電気角１周期分データ収集したならば、Ｕ相電圧Ｖｕの最大値ＶｕＭＡＸと最小値ＶｕＭＩＮを確定し（ステップＳ４６）、Ｗ相電圧Ｖｗの最大値ＶｗＭＡＸと最小値ＶｗＭＩＮを確定し（ステップＳ４７）、Ｕ相電流Ｉｕの最大値ＩｕＭＡＸと最小値ＩｕＭＩＮを確定し（ステップＳ４８）、Ｗ相電流Ｉｗの最大値ＩｗＭＡＸと最小値ＩｗＭＩＮを確定する（ステップＳ４９）。次に、Ｕ相オフセットずれＵｏｆｆｓｅｔ＝｛（ＩｕＭＡＸ＋ＩｕＭＩＮ）−（ＶｕＭＡＸ＋ＶｕＭＩＮ）／Ｒ｝／２を計算し（ステップＳ５０）、Ｗ相オフセットずれＷｏｆｆｓｅｔ＝｛（ＩｗＭＡＸ＋ＩｗＭＩＮ）−（ＶｗＭＡＸ＋ＶｗＭＩＮ）／Ｒ｝／２を計算し（ステップＳ５１）、電圧ゲインずれＶｐｐｅｒｒ＝｛ＶｕＭＡＸ−ＶｕＭＩＮ）−（ＩｗＭＡＸ−ＩｗＭＩＮ）｝／２を計算し（ステップＳ５２）、電流ゲインずれＩｐｐｅｒｒ＝｛（ＩｕＭＡＸ−ＩｕＭＩＮ）−（ＩｗＭＡＸ−ＩｗＭＩＮ）｝／２を計算し（ステップＳ５３）、ゲインずれＰｐｅｒｒ＝Ｖｐｐ／Ｒ＋Ｉｐｐｅｒｒを計算し（ステップＳ５４）、故障判定する（ステップＳ５５）。
【００７６】
このようにして確実に電流センサの故障を検知することができる。
【００７７】
次に、本発明の第３の実施形態に係る電動パワーステアリング装置を説明する。第３の実施形態では、図１で示した電動パワーステアリング装置の制御装置２２における駆動電圧監視部と検出電流監視部を後に述べるように変更した装置である。他の構成要素は同様なので説明を省略する。
【００７８】
図１６は第３の実施形態での駆動電圧監視部と検出電流監視部を示した図である。第３の実施形態での駆動電圧監視部は、第１の駆動電圧監視部１３０と第２の駆動電圧監視部１３１から成り、検出電流監視部は、第１の検出電流監視部１３２と第２の検出電流監視部１３３から成り、第１の駆動電圧監視部１３０は、いずれかの相の駆動電圧とモータの回転角度から他の相の電圧を推定する電圧推定部１０９，１１１と、他の相の駆動電圧と電圧推定部１０９，１１１により推定される推定電圧を比較して駆動電圧の異常信号を生成する第１の駆動電圧異常信号生成部１１２とから成り、第２の駆動電圧監視部１３１は、電流センサ２０６，２０７の配置されている各々の相の駆動電圧の１周期分のデータの最大値および最小値を検出する電圧最大値最小値検出部１２１，１２２と、電圧最大値最小値検出部１２１，１２２により検出された最大値および最小値から駆動電圧の異常信号を生成する第２の駆動電圧異常信号生成部１２３とから成り、第１の検出電流監視部１３２は、いずれかの相の検出電流とモータの回転角度から他の相の電流を推定する電流推定部１１４，１１６と、他の相の検出電流と電流推定部１１４，１１６により推定される推定電流を比較して検出電流の異常信号を生成する第１の検出電流異常信号生成部１１７とから成り、第２の検出電流監視部１３３は、電流センサ２０６，２０７により検出される各々の相の検出電流の１周期分のデータの最大値および最小値を検出する電流最大値最小値検出部１２５，１２６と、電流最大値最小値検出部１２５，１２６により検出された最大値および最小値から検出電流の異常信号を生成する第２の検出電流異常信号生成部１２７と、から成り、回転数に応じて第１の駆動電圧監視部１３０と第１の検出電流監視部１３２と、第２の駆動電圧監視部１３１と第２の検出電流監視部１３３とを切り換える切換部１３４，１３５を備えた。
【００７９】
この構成において、第１の駆動電圧監視部１３０と第１の検出電流監視部１３２は、第１の実施形態での駆動電圧監視部１０１と検出電流監視部１０２の構成と同様であり、また、第２の駆動電圧監視部１３１と第２の検出電流監視部１３３は、第２の実施形態での駆動電圧監視部１２０と検出電流監視部１２４の構成と同様であるので符号を同じにして説明を省略し、切換部１３４，１３５について説明する。
【００８０】
切換部１３４，１３５は、回転速度算出部２０８からの角速度信号ωを入力し、その角速度信号ωが所定の角速度（例えば、２０ｄｅｇ／ｓ）以下のときには、第１の駆動電圧監視部１３０と第１の検出電流監視部１３２に切り換え、第１の実施形態で説明したように故障検知を行う。また、所定の角速度より大きいときは、第２の駆動電圧監視部１３１と第２の検出電流監視部１３３に切り換え、第２の実施形態で説明したように故障検知を行う。
【００８１】
これにより、第１の実施形態での故障検知では操舵速度が充分低い場合以外では位相ずれの影響により誤検出してしまい、第２の実施形態での回転していない場合などでの１周期分のデータが取得できないことによる検出できなくなってしまうということを解消できる。すなわち、モータの回転速度が低い場合（ハンドル上２０ｄｅｇ／ｓｅｃ以下）には第１の駆動電圧監視部１３０と第１の検出電流監視部１３２により検出し、回転速度が高い場合（ハンドル上５ｄｅｇ／ｓｅｃ以上）には第２の駆動電圧監視部１３１と第２の検出電流監視部１３３により検出する。これにより、すべての回転速度において検出が可能となる。ハンドル上、５ｄｅｇ／ｓｅｃ〜２０ｄｅｇ／ｓｅｃの間では、第１、第２両方で監視し、故障検出中に切り替えが起こり、故障検出の時間が長くなることを防止している。
【００８２】
【発明の効果】
以上の説明で明らかなように本発明によれば、次の効果を奏する。
【００８３】
目標電流と実電流が一致するように電流制御が働き、目標電流と実電流が一致している場合においては、駆動電圧監視手段により検出される異常信号により故障が判定され、一方、検出トルクの脈動が無くなるように目標電流が設定され、モータを駆動する電圧に異常信号が現れない場合は、検出電流監視手段により検出される異常信号により故障が判定されるので、電動パワーステアリング装置における電動パワーステアリング装置制御の効き具合（不感帯かどうか、車速応動による制御の強弱）によらず、すべてのシチュエーションにおいて故障検出が可能となる。また、電流により検出される量と電圧により検出される量の単位を統一して合わせることにより、電流センサの故障量を推定することができ、センサの故障の程度に合わせたアクションをとることができる。
【００８４】
また、検出電流監視手段を２相の検出電流から算出される信号を用いて構成していることにより、３個目の電流センサを用いずに済み、コスト高になることがない。
【図面の簡単な説明】
【図１】本発明の第１の実施形態に係る電動パワーステアリング装置の全体構成図である。
【図２】電動パワーステアリング装置の機械的機構の要部と電気系の具体的構成を示す図である。
【図３】図２におけるＡ−Ａ線断面図である。
【図４】図３におけるＢ−Ｂ線断面図である。
【図５】電流制御部のブロック構成図である。
【図６】電流センサが故障した場合の３相２軸変換前後の波形を示すグラフである。
【図７】電動パワーステアリング装置での制御を説明する模式図である。
【図８】電流センサの故障している分の駆動電圧に現れる割合と検出電流に現れる割合を示す図である。
【図９】モータの抵抗値の算出方法の手順を示す図である。
【図１０】第１の実施形態での駆動電圧監視部と検出電流監視部のブロック構成図である。
【図１１】第１の実施形態での電流センサ故障検出フローチャートである。
【図１２】第１の実施形態での電流センサ故障量の検出を説明するグラフである。
【図１３】第２の実施形態での駆動電圧監視部と検出電流監視部のブロック構成図である。
【図１４】第２の実施形態での電流センサ故障量の検出を説明するグラフである。
【図１５】第２の実施形態での電流センサ故障検出フローチャートである。
【図１６】第３の実施形態での駆動電圧監視部と検出電流監視部のブロック構成図である。
【図１７】従来の電動パワーステアリング装置の制御装置のブロック構成図である。
【符号の説明】
１０ 電動パワーステアリング装置
１１ ステアリングホイール
１２ ステアリング軸
１８ 動力伝達機構
１９ ブラシレスモータ
２０ 操舵トルク検出部
２０ｄ 舵角センサ
２２ 制御装置
２３ モータ回転角検出部（角度センサ）
１００ 電流制御部
１０１ 駆動電圧監視部
１０２ 検出電流監視部
１０３ 故障検出部
１０４ 故障表示部
２０６ 電流センサ
２０７ 電流センサ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric power steering apparatus, and more particularly to an electric power steering apparatus provided with failure detection means such as a field effect transistor (FET), a wire harness, and a current sensor of motor current control means.
[0002]
[Prior art]
A conventional electric power steering device includes a steering force booster using a motor with a brush or a brushless motor as a power source, a control device including a microcomputer unit and a motor drive device, and the like. By detecting the vehicle speed and the like and driving a motor by a control device based on these detection signals, auxiliary torque is generated to reduce the steering force of the steering wheel.
[0003]
FIG. 17 is a block diagram of a conventional control device for controlling the rotation of the brushless motor. The control device 200 is a device that controls the brushless motor 203 with the steering torque signal T from the steering torque detection unit 201 and the vehicle speed signal V from the vehicle speed detection unit 202 as inputs, and a target current determination unit 204 and a current control unit 205. And current sensors 206 and 207 and a rotation speed calculation unit 208. The current control unit 205 includes deviation calculation units 209 and 210, PI setting units 211 and 212, a two-axis three-phase conversion unit 213, a motor drive unit 214, a calculation unit 215, and a three-phase two-axis conversion unit 216. . An angle sensor 217 such as a resolver for detecting the rotation angle of the brushless motor 203 is attached to the brushless motor 203.
[0004]
The target current determination unit 204 determines the two-phase target currents Idt and Iqt based on the steering torque signal T, the vehicle speed signal V, and the rotational angular velocity ω of the rotor of the brushless motor 203 output from the rotational speed calculation unit 208 with respect to the stator. Calculate and output. The target currents Idt and Iqt correspond to the d-axis in the same direction as the permanent magnet and the q-axis orthogonal thereto in the rotating coordinate system synchronized with the rotating magnetic flux generated by the permanent magnet on the rotor of the brushless motor 203, respectively. These target currents Idt and Iqt are referred to as “d-axis target current” and “q-axis target current”, respectively.
[0005]
The d-axis and q-axis target currents Idt and Iqt are subtracted from the d-axis and q-axis target currents Idt and Iqt in the deviation calculation units 209 and 210, respectively. To calculate the deviations DId and DIq and output them to the PI setting units 211 and 212.
[0006]
The PI setting units 211 and 212 execute calculations using the deviations DId and DIq so that the detected currents Idr and Iqr of the d-axis and the q-axis follow the target currents of the d-axis and the q-axis. Target voltages Vd and Vq are calculated respectively. The d-axis and q-axis target voltages Vd and Vq are output to the 2-axis 3-phase converter 213.
[0007]
The two-axis three-phase conversion unit 213 converts the d-axis and q-axis target voltages Vd, Vq into three-phase target voltages Vu, Vv, Vw, and converts the three-phase target voltages Vu, Vv, Vw into a motor drive unit (motor Drive circuit) 214.
[0008]
The motor drive unit 214 includes a PWM voltage generation unit (pre-drive circuit) and an inverter circuit. The motor drive unit 214 generates PWM control voltage signals (gate drive signals) UU, VU, WU corresponding to the three-phase target voltages Vu, Vv, Vw by a PWM voltage generation unit (not shown) in the motor drive unit 214. This is output to an inverter circuit (not shown) in the motor drive unit 214. The inverter circuit generates three-phase AC drive currents Iu, Iv, Iw corresponding to the PWM control voltage signals UU, VU, WU, and supplies these to the brushless motor 203 via the three-phase drive current path 218, respectively. . Three-phase AC drive currents Iu, Iv, and Iw are sinusoidal currents for PWM driving the brushless motor 203, respectively.
[0009]
Two of the three-phase drive current paths 218 are provided with motor current detection units (current sensors) 206 and 207, and each of the motor current detection units 206 and 207 is supplied with the three-phase drive current path 218. Two drive currents Iu and Iw out of the drive currents Iu, Iv, and Iw are detected and output to the three-phase biaxial conversion unit 216. Further, the calculation unit 215 calculates the remaining drive current Iv based on the detected drive currents Iu and Iw and outputs the calculated drive current Iv to the three-phase biaxial conversion unit 216. The three-phase two-axis conversion unit 216 converts these three-phase detection drive currents Iu, Iv, Iw into two-phase d-axis and q-axis detection currents Idr, Iqr and outputs them.
[0010]
The angle sensor 217 detects an angle (rotation angle) θ of the rotor with respect to the stator in the brushless motor 203, and outputs signals corresponding to the detected angle θ to the two-axis three-phase conversion unit 213 and the three-phase two-axis conversion unit. 216. Further, the rotation speed calculation unit 208 calculates a rotation angular speed ω of the rotor of the brushless motor 203 relative to the stator based on the signal from the angle sensor 217, and determines a signal corresponding to the calculated rotation angular speed ω as a target current. To the unit 204.
[0011]
As described above, in the conventional control device 200, the target current supplied to the brushless motor 203 based on the steering torque signal T output from the steering torque detection unit 201, the vehicle speed signal V output from the vehicle speed detection unit 202, and the like. Set. PI control is performed so that the deviation between the target current and the detection currents output from the motor current detection units (current sensors) 206 and 207 becomes zero, and the brushless motor 203 is vector-controlled.
[0012]
In the control device as described above, as a device for detecting when a current sensor fails, an abnormality detection device for a brushless motor disclosed in Patent Literature 1 and a control device for an electric vehicle motor disclosed in Patent Literature 2 An electric vehicle drive control device disclosed in Patent Document 3 is known.
[0013]
The abnormality detection device for a brushless motor disclosed in Patent Literature 1 includes a current sensor that detects a current of a motor winding provided in each phase of a three-phase motor, an adder that calculates the sum of output values of each current sensor, and an addition A comparator that compares a value with a predetermined value is used, and the fact that the sum of currents flowing through the three-phase motor is zero is determined to be a failure when the sum does not become zero.
[0014]
A control device for an electric motor for an electric vehicle disclosed in Patent Document 2 includes a current control unit that controls a current flowing through a motor to match a current command value, an integration unit that integrates a deviation between the current command value and the actual current, and an integral value It is composed of an abnormality determination means that determines that an abnormality occurs when the value exceeds a predetermined value. Utilizing the fact that the current command value matches the actual current by current control, it is determined that there is a failure when they do not match. To do.
[0015]
The drive control device for an electric vehicle disclosed in Patent Document 3 includes a rotation position detection unit that detects a rotation position of a motor, a motor current control unit that supplies a motor current according to the rotation position, and at least two that detects a phase current of the motor. One current detection means, a motor current estimation means for estimating a current value that should flow to the other phase based on the rotational position and the current value of one of the phases, and the detected current of the other phase and the estimation means Comparing the estimated currents, it is composed of failure detection means that determines that a failure occurs if the difference between the two is greater than or equal to a predetermined value. The current flowing through the three-phase motor is energized with a phase difference of 120 °. The current flowing in the other phase is estimated from the value shifted by 120 ° with respect to the current detected in one of the phases, and the detected current is compared with the detected current to detect the fault. Do.
[0016]
[Patent Document 1]
JP-A-6-253585
[Patent Document 2]
JP 11-332002 A
[Patent Document 3]
JP 2001-8484 A
[0017]
[Problems to be solved by the invention]
However, since the abnormality detection device for a brushless motor disclosed in Patent Document 1 detects the current for three phases and makes a determination based on the sum of the currents, all three-phase currents can be controlled even though it can be controlled by two current sensors. In order to detect, three current sensors are needed, and there exists a problem that cost becomes high.
[0018]
In addition, in the control device for the electric vehicle electric motor of Patent Document 2, it is possible to detect a failure such as no actual current flowing or the sensor output being stuck, but it seems to be an offset deviation or gain deviation of the current sensor. When the detected value changes with a value different from the true value, the current command value and the detected value are driven by current control so that the current command value and the detected value match. This method has a problem that a failure of the current sensor cannot be detected.
[0019]
Similarly, in the drive control device for an electric vehicle disclosed in Patent Document 3, the phase currents are controlled to flow with a phase difference of 120 ° by current control, so that the relationship between the phase currents is 120 ° in phase difference. There is a problem that a failure of the current sensor cannot be detected depending on whether or not it has a current.
[0020]
In order to solve the above problems, an object of the present invention is to provide an electric power steering device capable of reliably detecting a failure at a low cost when detecting a failure of a current sensor in an assist assist motor of the electric power steering device. is there.
[0021]
[Means and Actions for Solving the Problems]
The electric power steering apparatus according to the present invention is configured as follows to achieve the above object.
[0022]
A first electric power steering apparatus (corresponding to claim 1) includes a target current determining means for determining a target current based on a steering torque, a three-phase brushless motor for generating assist torque, and a three-phase brushless motor. Among them, a current sensor for detecting a two-phase current, a three-phase target current calculation means for calculating a one-phase current remaining from the two-phase current, an angle sensor for detecting a rotation angle of a three-phase brushless motor, Current control means for generating a motor current control signal based on the detected current and the target current; Drive voltage monitoring means for monitoring the drive voltage of the three-phase brushless motor; detection current monitoring means for monitoring the detected drive current of the three-phase brushless motor; In an electric power steering apparatus comprising: The first failure detection current is calculated from the drive voltage input to the drive voltage monitoring means, the second failure detection current is calculated from the current input to the detection current monitoring means, and the first failure detection current and the second failure detection current are calculated. And current sensor It is characterized by having a failure detection means for determining the failure.
[0023]
According to the first electric power steering apparatus, target current determining means for determining a target current based on the steering torque, a three-phase brushless motor that generates assist torque, and a two-phase current among the three phases of the three-phase brushless motor A current sensor that detects a rotation angle of a three-phase brushless motor, a three-phase target current calculation unit that calculates a one-phase current remaining from a two-phase current, a rotation angle, and a detected current Current control means for generating a motor current control signal based on the target current; Drive voltage monitoring means, detected current monitoring means, In an electric power steering apparatus comprising: The first failure detection current is calculated from the drive voltage input to the drive voltage monitoring means, the second failure detection current is calculated from the current input to the detection current monitoring means, and the first failure detection current and the second failure detection current are calculated. With the sum of Since it has a failure detection means to determine the failure of the current sensor, current control works so that the target current and the actual current match, and when the target current and the actual current match, it is detected by the drive voltage monitoring means On the other hand, if the target current is set so that there is no pulsation of the detected torque and no abnormal signal appears in the voltage that drives the motor, the abnormal signal detected by the detected current monitoring means Since the failure of the current sensor is determined, it is possible to detect the failure of the current sensor in all situations regardless of whether it is a dead zone in the electric power steering device or the effectiveness of the electric power steering device control, such as the strength of control due to vehicle speed response. It becomes. Also, by unifying the unit of the amount detected by the current and the amount detected by the voltage, the amount of failure of the current sensor can be estimated, and the action according to the degree of failure of the current sensor should be taken Can do.
[0024]
In the second electric power steering device (corresponding to claim 2), the drive voltage monitoring unit preferably estimates the voltage of the other phase from the drive voltage of any phase and the rotation angle of the motor. Comprising voltage estimation means, and drive voltage abnormality signal generation means for comparing the estimated voltage estimated by the voltage estimation means with the drive voltage of the other phase to generate an abnormality signal of the drive voltage. The current estimation means for estimating the current of the other phase from the detected current of the phase and the rotation angle of the motor, and the detected current abnormality signal by comparing the detected current of the other phase and the estimated current estimated by the current estimation means And a detected current abnormality signal generating means for generating.
[0025]
According to the second electric power steering apparatus, the drive voltage monitoring means includes voltage estimation means for estimating the voltage of the other phase from the drive voltage of any phase and the rotation angle of the motor, and the drive voltage of the other phase. Drive voltage abnormality signal generation means for comparing the estimated voltage estimated by the voltage estimation means to generate a drive voltage abnormality signal, and the detection current monitoring means is based on the detection current of any phase and the rotation angle of the motor. Current estimation means for estimating the current of the other phase, and detection current abnormality signal generation means for generating a detection current abnormality signal by comparing the detection current of the other phase with the estimation current estimated by the current estimation means Therefore, by configuring the detection current monitoring means using a signal calculated from the two-phase detection current, it is not necessary to use the third current sensor, and the cost is not increased.
[0026]
In the third electric power steering apparatus (corresponding to claim 3), in the above-mentioned configuration, the drive voltage monitoring means preferably has a maximum of data for one cycle of the drive voltage of each phase where the current sensor is arranged. Voltage maximum value / minimum value detection means for detecting the value and minimum value, and drive voltage abnormality signal generation means for generating a drive voltage abnormality signal from the maximum value and minimum value detected by the voltage maximum value / minimum value detection means. The detected current monitoring means includes a current maximum value minimum value detecting means for detecting a maximum value and a minimum value of data for one cycle of the detected current of each phase detected by the current sensor, and a current maximum value minimum value detecting means. And a detected current abnormality signal generating means for generating an abnormality signal of the detected current from the maximum value and the minimum value detected by the above.
[0027]
According to the third electric power steering apparatus, the drive voltage monitoring means detects the maximum value and the minimum value of the data for one cycle of the drive voltage of each phase where the current sensor is arranged. The detection means and a drive voltage abnormality signal generation means for generating a drive voltage abnormality signal from the maximum value and the minimum value detected by the voltage maximum value minimum value detection means, and the detected current monitoring means is detected by the current sensor. Current maximum value / minimum value detection means for detecting the maximum value and minimum value of data for one cycle of the detected current of each phase, and the detected current from the maximum value and the minimum value detected by the current maximum value / minimum value detection means Detection current abnormality signal generation means for generating an abnormal signal of the above, so that the detection current monitoring means is configured by using signals calculated from the two-phase detection current, thereby providing three Finished without using a current sensor, it never becomes costly.
[0028]
In the fourth electric power steering apparatus (corresponding to claim 4), in the above configuration, preferably the drive voltage monitoring means includes a first drive voltage monitoring means and a second drive voltage monitoring means, and a detected current monitor. The means includes first detection current monitoring means and second detection current monitoring means, and the first drive voltage monitoring means estimates the voltage of the other phase from the drive voltage of any phase and the rotation angle of the motor. And a first drive voltage abnormality signal generation means for generating a drive voltage abnormality signal by comparing the drive voltage of the other phase with the estimated voltage estimated by the voltage estimation means, The drive voltage monitoring means includes a voltage maximum value / minimum value detection means for detecting a maximum value and a minimum value of data for one cycle of the drive voltage of each phase in which the current sensor is arranged, and a voltage maximum value / minimum value detection means. Detected by And a second drive voltage abnormality signal generating means for generating a drive voltage abnormality signal from the value and the minimum value. The first detection current monitoring means determines the other from the detection current of any phase and the rotation angle of the motor. Current estimation means for estimating the current of the phase, and first detection current abnormality signal generation means for generating an abnormality signal of the detection current by comparing the detection current of the other phase and the estimation current estimated by the current estimation means The second detection current monitoring means comprises a current maximum value / minimum value detection means for detecting a maximum value and a minimum value of data for one cycle of the detection current of each phase detected by the current sensor, and a current maximum value. Second detection current abnormality signal generation means for generating an abnormality signal of the detection current from the maximum value and the minimum value detected by the minimum value detection means, and the first drive voltage monitoring means and the first detection voltage according to the rotational speed 1 detection current monitor And means, characterized by comprising a second driving voltage monitoring means and switching means for switching a second detection current monitoring means. Thereby, a failure of the current sensor can be reliably detected.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the accompanying drawings.
[0030]
The overall configuration of the electric power steering apparatus according to the present invention, the main configuration of the mechanical mechanism, and the layout of the electronic circuit unit will be described with reference to FIGS.
[0031]
FIG. 1 is an overall configuration diagram of an electric power steering apparatus according to a first embodiment of the present invention. The electric power steering device 10 is configured to give auxiliary steering force (steering torque) to the steering shaft 12 and the like connected to the steering wheel 11. An upper end of the steering shaft 12 is connected to the steering wheel 11, and a pinion gear 13 is attached to the lower end. A rack shaft 14 provided with a rack gear 14a meshing with the pinion gear 13 is disposed. A rack and pinion mechanism 15 is formed by the pinion gear 13 and the rack gear 14a. Tie rods 16 are provided at both ends of the rack shaft 14, and front wheels 17 are attached to the outer ends of the tie rods 16. A brushless motor 19 is provided on the steering shaft 12 via a power transmission mechanism 18. The brushless motor 19 outputs a rotational force (torque) that assists the steering torque, and applies this rotational force to the steering shaft 12 via the power transmission mechanism 18. The steering shaft 12 is provided with a steering torque detector 20. The steering torque detector 20 detects the steering torque applied to the steering shaft 12 when the steering torque generated by the driver operating the steering wheel 11 is applied to the steering shaft 12. Reference numeral 20d denotes a steering angle sensor that detects a steering angle, reference numeral 21 denotes a vehicle speed detection unit that detects the vehicle speed of the vehicle, and reference numeral 22 denotes a control device constituted by a computer. The control device 22 takes in the steering torque signal T output from the steering torque detection unit 20, the steering angle signal output from the steering angle sensor 20d, and the vehicle speed signal V output from the vehicle speed detection unit 21, and information related to the steering torque. And a drive control signal SG1 for controlling the rotation operation of the brushless motor 19 based on the information on the steering angle and the information on the vehicle speed. Further, the brushless motor 19 is provided with a motor rotation angle detector (angle sensor) 23 constituted by a resolver or the like. The rotation angle signal SG2 of the motor rotation angle detector 23 is fed back to the control device 22. The rack and pinion mechanism 15 and the like are housed in a gear box 24 not shown in FIG.
[0032]
In the above, the electric power steering device 10 adds a steering torque detection unit 20, a steering angle sensor 20d, a vehicle speed detection unit 21, a control device 22, a brushless motor 19, and a power transmission mechanism 18 to a normal steering system configuration. Is made up of.
[0033]
In the above configuration, when the driver operates the steering wheel 11 to steer in the traveling direction during the traveling operation of the automobile, the rotational force based on the steering torque applied to the steering shaft 12 is transmitted via the rack and pinion mechanism 15. It is converted into a linear motion in the axial direction of the rack shaft 14, and further, the traveling direction of the front wheel 17 is changed via the tie rod 16. At this time, at the same time, the steering torque detector 20 attached to the steering shaft 12 detects the steering torque corresponding to the steering by the driver at the steering wheel 11 and converts it into an electrical steering torque signal T. A steering torque signal T is output to the control device 22. The steering angle sensor 20 d detects the steering angle and outputs a steering angle signal to the control device 22. Further, the vehicle speed detection unit 21 detects the vehicle speed of the vehicle, converts it into a vehicle speed signal V, and outputs this vehicle speed signal V to the control device 22. The control device 22 generates a motor current for driving the brushless motor 19 based on the steering torque signal T, the steering angle signal, and the vehicle speed signal V. The brushless motor 19 driven by the motor current causes an auxiliary steering force to act on the steering shaft 12 via the power transmission mechanism 18. By driving the brushless motor 19 as described above, the steering force applied by the driver to the steering wheel 11 is reduced.
[0034]
FIG. 2 shows a specific configuration of the main part of the mechanical mechanism of the electric power steering apparatus 10 and the electric system. A part of the left end portion and the right end portion of the rack shaft 14 is shown in cross section. The rack shaft 14 is housed in a cylindrical housing 31 arranged in the vehicle width direction (left-right direction in FIG. 2) so as to be slidable in the axial direction. Ball joints 32 are screwed to both ends of the rack shaft 14 protruding from the housing 31, and left and right tie rods 16 are connected to these ball joints 32. The housing 31 includes a bracket 33 for attaching to a vehicle body (not shown), and includes stoppers 34 at both ends.
[0035]
In FIG. 2, 35 is an ignition switch, 36 is an in-vehicle battery, and 37 is an AC generator (ACG) attached to the vehicle engine. The AC generator 37 starts power generation by the operation of the vehicle engine. Necessary electric power is supplied from the battery 36 or the AC generator 37 to the control device 22. The control device 22 is attached to the brushless motor 19. Reference numeral 38 denotes a rack end that contacts the stopper 34 when the rack shaft is moved, and 39 is a dust seal boot for protecting the inside of the gear box from water, mud, dust and the like.
[0036]
FIG. 3 is a cross-sectional view taken along line AA in FIG. In FIG. 3, the specific structure of the support structure of the steering shaft 12, the steering torque detector 20, the power transmission mechanism 18, the rack and pinion mechanism 15, and the layout of the brushless motor 19 and the control device 22 are clearly shown.
[0037]
In FIG. 3, the steering shaft 12 is rotatably supported by two bearing portions 41 and 42 in a housing 24 a forming the gear box 24. A rack and pinion mechanism 15 and a power transmission mechanism 18 are housed inside the housing 24a, and a steering torque detector 20 is additionally provided at the top. The upper opening of the housing 24 a is closed with a lid 43, and the lid 43 is fixed with bolts 44. The pinion 13 provided at the lower end portion of the steering shaft 12 is located between the bearing portions 41 and 42. The rack shaft 14 is pressed against the pinion 13 side by a contact member 47 guided by a rack guide 45 and biased by a compressed spring 46. The power transmission mechanism 18 is formed by a worm gear 49 fixed to a transmission shaft 48 coupled to an output shaft of the brushless motor 19 and a worm wheel 50 fixed to the steering shaft 12. The steering torque detection unit 20 includes an electronic circuit unit 20b that electrically processes a detection signal output from a steering torque detection sensor 20a disposed around the steering shaft 12. The steering torque detection sensor 20 a is attached to the lid 43.
[0038]
4 is a cross-sectional view taken along line BB in FIG. In FIG. 4, specific configurations of the brushless motor 19 and the control device 22 are clearly shown.
[0039]
The brushless motor 19 includes a rotor 52 made of a permanent magnet fixed to the rotation shaft 51 and a stator 54 disposed around the rotor 52. The stator 54 includes a stator winding 53. The rotating shaft 51 is rotatably supported by the two bearing portions 55 and 56. The tip of the rotating shaft 51 is an output shaft 19 a of the brushless motor 19. The output shaft 19a of the brushless motor 19 is coupled to the transmission shaft 48 through the torque limiter 57 so that rotational power is transmitted. As described above, the worm gear 49 is fixed to the transmission shaft 48, and the worm wheel 50 meshing with the worm gear 49 is disposed. At the rear end portion of the rotation shaft 51, the above-described motor rotation angle detection unit (angle sensor) 23 that detects the rotation angle (rotation position) of the rotor 52 of the brushless motor 19 is provided. The motor rotation angle detection unit 23 includes a rotor 23a fixed to the rotation shaft 51 and a detection element 23b that detects the rotation angle of the rotor 23a using a magnetic action. For example, a resolver is used for the motor rotation angle detector 23. A motor current is supplied to the stator winding 53 of the stator 54. The above components of the brushless motor 19 are arranged inside the motor case 58.
[0040]
Next, the control device 22 will be described. The control device 22 includes a target current determination unit, a current control unit, a current sensor, and a rotation speed calculation unit, similarly to the control device 200 shown in FIG. In the embodiment of the present invention, since the current control unit is different from the conventional one, the current control unit will be described in detail, and the target current determination unit, the current sensor, and the rotation speed calculation unit are the same as those of the conventional control device 200. Omitted.
[0041]
FIG. 5 is a block diagram of the current control unit. The current control unit 100 includes deviation calculation units 209 and 210, a PI setting unit 211 and 212, a two-axis three-phase conversion unit 213, a motor drive unit 214, a calculation unit 215, and a three-phase unit similar to the conventional current control unit 205. In addition to the biaxial conversion unit 216, a drive voltage monitoring unit 101, a detected current monitoring unit 102, and a failure detection unit 103 are provided. An angle sensor 23 such as a resolver for detecting the rotation angle of the brushless motor 19 is attached to the brushless motor 19. The drive voltage monitoring unit 101 receives the three-phase target voltages Vu and Vw output from the two-axis three-phase conversion unit 213, and estimates the W-phase drive voltage Vw from the U-phase drive voltage Vu and the rotation angle of the motor. A voltage estimator (not shown) compares the estimated voltage estimated by the W-phase drive voltage Vw and the voltage estimator (not shown), and outputs an abnormal signal when the absolute value of the difference is equal to or greater than a predetermined value. It is a device that outputs to the failure detection unit 103. The detection current monitoring unit 102 receives the detection drive currents Iu and Iw, a current estimation unit (not shown) that estimates the W-phase detection drive current Iw from the U-phase detection drive current Iu and the rotation angle of the motor, A device that compares the detected drive current Iw of the W phase with the estimated current estimated by a current estimation unit (not shown) and outputs an abnormal signal to the failure detection unit 103 when the absolute value of the difference is a predetermined value or more. is there. The failure detection unit 103 receives signals from the drive voltage monitoring unit 101 and the detection current monitoring unit 102 and detects a failure of the current sensors 206 and 207. In addition, a failure display unit 104 is connected to the failure detection unit 103. Then, the failure detection unit 103 outputs a signal to the failure display unit 104 when the failure of the current sensors 206 and 207 is determined and as a signal when the failure is not determined. The deviation calculation units 209 and 210, the PI setting units 211 and 212, the two-axis three-phase conversion unit 213, the motor drive unit 214, the calculation unit 215, and the three-phase two-axis conversion unit 216 are basically shown in FIG. Since it is the same as that described, the same reference numerals are given and description thereof is omitted.
[0042]
Next, the reason for providing monitoring means for both the drive voltage and the detection current in the control device of the present invention will be described.
[0043]
FIG. 6 shows waveforms before and after the three-phase biaxial conversion when the current sensor has a failure such as offset deviation or gain deviation. In the three-phase two-axis conversion, the three-phase currents Iu and Iw are converted into two-axis currents Id and Iq according to the equation (1).
[0044]
[Expression 1]

[0045]
FIG. 6A shows a three-phase current in a normal state, the horizontal axis shows an electrical angle, and the vertical axis shows a three-phase current. A curve C10 indicates the current Iu, and a curve C11 indicates the current Iw. FIG. 6B shows a normal biaxial current, the horizontal axis shows an electrical angle, and the vertical axis shows a biaxial current. A curve C12 indicates the d-axis current Id, and a curve C13 indicates the q-axis current Iq. FIG. 6C shows the three-phase current when the current sensor is offset, the horizontal axis shows the electrical angle, and the vertical axis shows the three-phase current. A curve C20 indicates the current Iu, and a curve C21 indicates the current Iw. FIG. 6D shows the biaxial current at the time of offset deviation of the current sensor, the horizontal axis shows the electrical angle, and the vertical axis shows the biaxial current. A curve C22 indicates the d-axis current Id, and a curve C23 indicates the q-axis current Iq. FIG. 6E shows the three-phase current when the gain of the current sensor is shifted, the horizontal axis shows the electrical angle, and the vertical axis shows the three-phase current. A curve C30 indicates the current Iu, and a curve C31 indicates the current Iw. FIG. 6F shows the biaxial current at the time of gain deviation of the current sensor, the horizontal axis shows the electrical angle, and the vertical axis shows the biaxial current. A curve C32 indicates the d-axis current Id, and a curve C33 indicates the q-axis current Iq. From this figure, when an offset deviation occurs in the current sensor, a primary pulsation is detected for one period of electrical angle, and when a gain deviation occurs in the current sensor, a secondary pulsation is detected for one period of electrical angle. It can be seen that it appears in the dq-axis current.
[0046]
FIG. 7 is a schematic diagram for explaining control in the electric power steering apparatus. The control in the electric power steering apparatus is a double control of the torque loop 105 and the current loop 106. That is, the drive voltage is output by the current control unit 100 in the current loop 106 based on the target current set by the torque control unit 107, thereby driving the motor 19. The motor current of the motor 19 to be driven is detected by current sensors 206 and 207, and the detected current is fed back to the current control unit 100. A loop formed by the current control unit 100, the motor 19, the current sensors 206 and 207, and the current control unit 100 is a current loop 106. Further, assist torque is applied to the steering shaft 12 in the gear box 24 by driving the motor 19, and a torque signal detected by the torque sensor 20 is fed back to the torque control unit 107. A loop formed by the torque control unit 107, the current control unit 100, the motor 19, the gear box 24, the torque sensor 20, and the torque control unit 107 is a torque loop 105. As described above, the control of the electric power steering apparatus 10 includes the current loop 106 for controlling the detected current for detecting the current flowing through the motor 19 to match the target current, and the steering torque for generating the steering assist force. Double control of the torque loop 105 that detects the target current and detects the target current works, and the torque loop 105 changes the degree of control according to the vehicle speed, steering torque, steering speed, and the like.
[0047]
In the control of the electric power steering apparatus 10 configured as shown in FIG. 7, the operation of each control when the failure of the current sensors 206 and 207 shown in FIG. 6 occurs will be described.
[0048]
When the current sensors 206 and 207 fail, the detected biaxial current is detected even though the biaxial current flowing in the motor 19 is flowing like the normal biaxial current as shown in FIG. 6B. 6 (d) and 6 (f), the current sensor is detected as a biaxial current at the time of offset deviation and gain deviation. Control is performed so that the detected current matches the target current.
[0049]
Considering the case where the target current is zero, the detected biaxial current becomes zero by control. At this time, a pulsation corresponding to the failure appears in the biaxial current flowing in the motor 19, and a pulsation appears in the drive voltage driving the motor 19. The pulsation of the motor current causes the torque generated by the motor 19 to pulsate accordingly, and the pulsating motor torque makes the driver feel uncomfortable or cannot be steered.
[0050]
However, since the electric power steering apparatus 10 has torque control having an effect of reducing the pulsation of the steering torque, the target current is adjusted so as to cancel the pulsation appearing in the steering torque. Thus, if control is performed such that no pulsation appears in the steering torque, the current flowing in the motor 19 is also free from pulsation, and the pulsation of the drive voltage driving the motor 19 is also eliminated. In this case, the failure of the current sensors 206 and 207 appears as a pulsation of the detected current.
[0051]
For this reason, the failure signal at the time of failure of the current sensor in the electric power steering device appears in both the drive voltage and the detected current depending on the working degree of the current control and the torque control as shown in FIG. This is considered to be the failure of the current sensor. That is, the ratio that appears in the drive voltage corresponding to the failure of the current sensor in FIG. 8 and the ratio that appears in the detected current are, as shown in FIG. In contrast, when the torque control is strong, the ratio that appears in the drive voltage increases, and the ratio that appears in the detection current increases by controlling the generated torque by disturbing the detection current.
[0052]
Based on this, in the present invention, monitoring means are provided for both the drive voltage and the detected current, and they are combined to perform failure detection. However, since the units of the drive voltage and the detected current are different, simple addition cannot be performed. Therefore, the component detected by the drive voltage using the resistance value of the motor is converted into the unit of current. The resistance value of the motor used here is calculated by the method shown in FIG. 9, and the initial value corresponds to the motor design value, temperature change, etc., so that vq = R × iq at the time of steering is satisfied. The value measured by applying a low pass filter to the value calculated from this relational expression is used. That is, the circuit equation is expressed by the equation (2),
[0053]
[Expression 2]

[0054]
In the steered state, ωe = 0 and PIq = 0, so Vq = RIq. As shown in FIG. 9, in the flowchart of calculating the motor resistance value, first, Iq differentiation processing is performed to obtain a differential value of Iq (step S10). ), Iq low pass filter processing is performed to obtain IqLPF (step S11), Vq low pass filter processing is performed to obtain VqLPF (step S12), the rotational speed is smaller than the threshold value, and the differential value of Iq is smaller than the threshold value. It is determined whether VqLPF is larger than the threshold value and IqLPF is larger than the threshold value (step S13). If this is not satisfied, the calculation ends, and if it is satisfied, R = VqLPF / IqLPF is calculated (step S14), RLPF = RLPF processing (step S15) is performed, and the process ends.
[0055]
Next, the drive voltage monitoring unit 101 and the detected current monitoring unit 102 will be described. The drive voltage monitoring unit 101 includes a voltage estimation unit that estimates a voltage of another phase from the drive voltage of any phase and the rotation angle of the motor 19, and an estimated voltage estimated by the drive voltage and voltage estimation unit of the other phase. The detection current monitoring unit 102 estimates the current of the other phase from the detection current of one of the phases and the rotation angle of the motor. The current estimation unit includes a detection current abnormality signal generation unit that generates a detection current abnormality signal by comparing a detection current of another phase with an estimation current estimated by the current estimation unit.
[0056]
FIG. 10 shows the drive voltage monitoring unit 101 and the detected current monitoring unit 102. The drive voltage monitoring unit 101 inputs the U-phase voltage from the two-axis three-phase conversion unit 213 to the deviation calculation unit 108, and the U-phase The voltage is output to the deviation calculation unit 110 via a calculation unit (voltage estimation unit) 109 that multiplies a coefficient (sin (θ + 120 °) / sin θ) based on the motor rotation angle from the angle sensor 23. In addition, the W-phase voltage from the biaxial three-phase conversion unit 213 is output to the deviation calculation unit 110, and the coefficient (sin θ / sin (θ + 120 °)) based on the motor rotation angle from the angle sensor 23 is added to the W-phase voltage. It outputs to the deviation calculating part 108 via the calculating part (voltage estimation part) 111 to multiply. The deviation calculation unit 108 outputs the deviation signal to the drive voltage abnormality signal generation unit 112. Further, the deviation calculation unit 110 outputs the deviation signal to the drive voltage abnormality signal generation unit 112.
[0057]
The drive voltage abnormality signal generation unit 112 determines that the deviation is normal when the deviation from the deviation calculation units 108 and 110 is smaller than a predetermined value, and outputs a normal value signal to the failure detection unit 103. The deviation is a predetermined value. If it is larger, it is determined as a failure, and a failure signal (abnormal signal), for example, 1 is output to the failure detection unit 103.
[0058]
The detected current monitoring unit 102 inputs the U-phase current from the current sensor 207 to the deviation calculating unit 113, and the coefficient based on the motor rotation angle from the angle sensor 23 (sin (θ + 120 °) / sinθ). Is output to the deviation calculation unit 115 via the calculation unit (current estimation unit) 114. In addition, the W-phase current from the current sensor 206 is output to the deviation calculation unit 115, and the calculation unit (sin θ / sin (θ + 120 °)) based on the motor rotation angle from the angle sensor 217 is multiplied by the W-phase current ( Output to the deviation calculator 113 via the current estimator 116. Deviation calculation unit 113 outputs the deviation signal to detected current abnormality signal generation unit 117. Further, the deviation calculation unit 115 outputs a deviation signal to the detected current abnormality signal generation unit 117.
[0059]
The detected current abnormality signal generation unit 117 determines that the deviation is normal if the deviation output from the deviation calculation units 113 and 115 is smaller than a predetermined value, and outputs a normal value signal to the failure detection unit 103. If it is larger than the predetermined value, it is determined as a failure, and a failure signal (abnormal signal), for example, 1 is output to the failure detection unit 103.
[0060]
The failure detection unit 103 determines that a failure has occurred when an abnormality signal is output from the drive voltage abnormality signal generation unit 112 or the detected current abnormality signal generation unit 117, and outputs a failure signal, for example, 1 to the failure display unit 104.
[0061]
The failure display unit 104 is a device that displays whether or not the current sensors 206 and 207 are in failure. For example, the failure display unit 104 includes a light emitting diode that blinks based on an input signal from the failure detection unit 103. The light emitting diode may be kept off when the signal from the failure detection unit 103 is zero, and lit up when the input from the failure detection unit 103 is 1. Thereby, when the light emitting diode is turned on, it can be determined that the current sensors 206 and 207 are out of order.
[0062]
FIG. 11 is a flowchart of sensor failure detection. It is determined whether the rudder angular velocity is smaller than 20 deg / s (step S20). When the rudder angular velocity is not smaller than 20 deg / s, the process returns and step S20 is executed again. When the rudder angular velocity is smaller than 20 deg / s, it is determined whether or not the motor rotation angle θ is in the range of 0 to 60 ° and 180 to 240 ° (step S21). If there is no motor rotation angle in this range, step S22 is executed. If the motor rotation angle θ is within this range, Vu * = Vv · (sin θ / sin (θ−120 °)) is calculated (step S23). Next, Iu * = Iv · (sin θ / sin (θ−120 °)) is calculated (step S24). Vw * = Vu · (sin (θ + 120 °) / sin (θ−120 °)) is calculated (step S25), and Iw * = Iu · (sin (θ + 120 °) / sin (θ−120 °)) is calculated. (Step S26), Err1 = (Vu−Vu *) / R + (Iu−Iu *) and Err2 = (Vw−Vw *) / R + (Iw−Iw *) are calculated (Step S27), and Err = Max (Err1, Err2) is calculated (step S28), and a failure is determined (step S29).
[0063]
If NO in step S21, step S22 is executed. If θ is in the range of 60 to 120 ° and 240 to 300 °, Vw * = Vu · (sin (θ + 120 °) / sin θ is calculated (step S30), Iw * = Iu · (sin (θ + 120 °) / sinθ) is calculated (step S31), Err = (Vw−Vw *) / R + (Iw−Iw *) is calculated (step S32), and a failure occurs. Judgment is made (step S29). If No in step S22, Vu * = Vw · (sin θ / sin (θ + 120 °)) is calculated (step S33), and Iu * = Iw · (sin θ / sin (θ + 120 °)). ) Is calculated (step S34), Err = (Vu−Vu *) / R + (Iu−Iu *) is calculated (step S35), and a failure is determined (step S29).
[0064]
As described above, when the three-phase motor is used with sine wave energization, the drive voltage waveform and the current waveform are sine waves in which the three phases each have a phase difference of 120 °. Therefore, by comparing the value obtained by multiplying the U-phase current by a coefficient for changing the phase by 120 ° and estimating the W-phase current with the detected W-phase current, it is determined whether or not there is a deviation in the sensor. I think it can be judged.
[0065]
However, the coefficient for estimation is sin (θ + 120 °) / sin (θ), and there is a problem such as an infinite value at an angle where θ is zero. By switching according to the angle as shown in FIG. 11, the coefficient for estimation becomes a value smaller than 1, and the error in estimation can be reduced.
[0066]
FIG. 12 is a graph showing the sensor failure amount based on the other phase estimation. FIG. 12A shows a change in the three-phase current with respect to the electrical angle at the time of offset deviation. The horizontal axis indicates the electrical angle, and the vertical axis indicates the amplitude. A curve C40 indicates a U-phase current, a curve C41 indicates a V-phase current, and a curve C42 indicates a W-phase current. A curve C43 indicates the U-phase estimated current, and a curve C45 indicates the W-phase estimated current. FIG. 12B is a graph showing the amount of deviation with respect to the electrical angle. FIG. 12C shows a change in the three-phase current with respect to the electrical angle when there is a gain shift. The horizontal axis indicates the electrical angle, and the vertical axis indicates the amplitude. Curve C50 shows the U-phase current, curve C51 shows the V-phase current, and curve C52 shows the W-phase current. A curve C53 indicates the U-phase estimated current, and a curve C55 indicates the W-phase estimated current. FIG. 12D is a graph showing the amount of deviation with respect to the electrical angle.
[0067]
By switching the estimation partner according to the angle in this way, the deviation amount is detected as shown in FIG. 12, and the deviation amount of the driving voltage and the deviation amount of the detected current are calculated, and after matching the units, The deviation amount of the current sensor is detected. The deviation detected in this way is checked, and if the deviation exceeds the threshold for a predetermined time, it is determined that a failure has occurred.
[0068]
However, this method assumes that the voltage / current phase matches the electrical angle. However, if the steering speed increases, the phase of the drive voltage will advance, so only if the steering speed is sufficiently low. To process.
[0069]
Next, an electric power steering apparatus according to a second embodiment of the present invention will be described. In the second embodiment, the drive voltage monitoring unit and the detected current monitoring unit in the control device 22 of the electric power steering apparatus shown in FIG. 1 are changed as described later. Since other components are the same, description thereof is omitted.
[0070]
A drive voltage monitoring unit and a detection current monitoring unit in the second embodiment will be described. As shown in FIG. 13, the drive voltage monitoring unit 120 detects the maximum value and the minimum value of the voltage to detect the maximum value and the minimum value of one cycle of the drive voltage of each phase where the current sensors 206 and 207 are arranged. Sections 121 and 122, and a drive voltage abnormality signal generation section 123 that generates a drive voltage abnormality signal from the maximum and minimum values detected by the voltage maximum value and minimum value detection sections 121 and 122, and a detected current monitoring section 124. Includes current maximum value / minimum value detection units 125 and 126 for detecting the maximum value and minimum value of data for one cycle of the detected current of each phase detected by the current sensors 206 and 207, and current maximum value / minimum value detection. A detection current abnormality signal generation unit 127 that generates an abnormality signal of the detection current from the maximum value and the minimum value detected by the units 125 and 126.
[0071]
The drive voltage monitoring unit 120 inputs the U-phase voltage from the two-axis three-phase conversion unit 213 to the voltage maximum value / minimum value detection unit 121, detects the maximum value and the minimum value of data for one cycle of the drive voltage, Those values are output to the drive voltage abnormality signal generator 123. The drive voltage abnormality signal generation unit 123 calculates the offset deviation and the amplitude deviation using the maximum value and the minimum value, and when the offset deviation value is a predetermined value or more, or when the amplitude deviation value is a predetermined value or more, the abnormal signal Is output to the failure detection unit 103. In addition, the W-phase voltage from the biaxial three-phase conversion unit 213 is input to the voltage maximum value / minimum value detection unit 122, and the maximum value and the minimum value of the data for one cycle of the drive voltage are detected. This is output to the drive voltage abnormality signal generator 123. The drive voltage abnormality signal generation unit 123 calculates the offset deviation and the amplitude deviation using the maximum value and the minimum value, and when the offset deviation value is a predetermined value or more, or when the amplitude deviation value is a predetermined value or more, the abnormal signal Is output to the failure detection unit 103.
[0072]
The detected current monitoring unit 124 inputs the U-phase current from the current sensor 207 to the current maximum value / minimum value detection unit 125, detects the maximum value and the minimum value of the data for one cycle of the detected current, and detects these values. The detected current abnormality signal generation unit 127 outputs the detected current abnormality signal. The detected current abnormality signal generation unit 127 calculates the offset deviation and the amplitude deviation using the maximum value and the minimum value. When the offset deviation value is equal to or larger than a predetermined value, or when the amplitude deviation value is equal to or larger than the predetermined value, an abnormal signal is detected. Is output to the failure detection unit 103. Further, the W-phase current from the current sensor 206 is input to the current maximum value / minimum value detection unit 126, the maximum value and the minimum value of the data for one cycle of the current sensor 206 are detected, and those values are detected as a detected current abnormality signal. The data is output to the generation unit 127. The detected current abnormality signal generation unit 127 calculates the offset deviation and the amplitude deviation using the maximum value and the minimum value. When the offset deviation value is equal to or larger than a predetermined value, or when the amplitude deviation value is equal to or larger than the predetermined value, an abnormal signal is detected. Is output to the failure detection unit 103.
[0073]
FIG. 14 is a graph showing the principle of detection of offset deviation and gain deviation of the current sensors 206 and 207 from the maximum value / minimum value in the drive voltage abnormality signal generation unit 123 and the detected current abnormality signal generation unit 124. FIG. 14A shows changes in current or voltage due to offset deviation. A curve C60 is a U-phase current or voltage, and a curve C61 is a W-phase current or voltage. The horizontal axis represents the electrical angle, and the vertical axis represents the amplitude. The offset deviation is obtained as a deviation from the median of the maximum value MAX10 and the minimum value MIN10 of the U-phase current or voltage from zero. Further, the offset deviation is obtained as a deviation from the median of the maximum value MAX11 and the minimum value MIN11 of the W-phase current or voltage from zero. FIG. 14B shows changes in current or voltage due to gain deviation. A curve C70 is a U-phase current or voltage, and a curve C71 is a W-phase current or voltage. The horizontal axis represents the electrical angle, and the vertical axis represents the amplitude. The gain deviation is obtained as a difference in amplitude obtained from the maximum value MAX21 and the minimum value MIN21 of the W-phase voltage or current having the amplitude obtained from the maximum value MAX20 and the minimum value MIN20 of the U-phase current or voltage.
[0074]
The failure detection unit 103 determines that a failure has occurred when an abnormality signal is input from the drive voltage abnormality signal generation unit 123 or the detected current abnormality signal generation unit 127, and outputs a failure signal, for example, 1 to the failure display unit 104. Thereby, when the light emitting diode of the failure display unit 104 is turned on, the current sensors 206 and 207 can be determined as a failure.
[0075]
FIG. 15 is a flowchart of sensor failure detection. It is determined whether the rudder angular velocity is 5 deg / s or more (step S40). If the rudder angular velocity is less than 5 deg / s, the process returns and executes step S40. When the steering angular velocity is 5 deg / s or more, it is determined whether or not data for one electrical angle cycle has been collected (step S41). If data for one cycle is not collected, the maximum value VuMAX and minimum value VuMIN of the U-phase voltage Vu are continuously detected (step S42), and the maximum value VwMAX and minimum value VwMIN of the W-phase voltage Vw are detected. (Step S43), the maximum value IuMAX and the minimum value IuMIN of the U-phase current Iu are detected (step S44), and the maximum value IwMAX and the minimum value IwMIN of the W-phase current Iw are detected (step S45). If data for one electrical angle period is collected in step S41, the maximum value VuMAX and minimum value VuMIN of the U-phase voltage Vu are determined (step S46), and the maximum value VwMAX and minimum value VwMIN of the W-phase voltage Vw are determined ( In step S47, the maximum value IuMAX and minimum value IuMIN of the U-phase current Iu are determined (step S48), and the maximum value IwMAX and minimum value IwMIN of the W-phase current Iw are determined (step S49). Next, U phase offset deviation Uoffset = {(IuMAX + IuMIN) − (VuMAX + VuMIN) / R} / 2 is calculated (step S50), and W phase offset deviation Woffset = {(IwMAX + IwMIN) − (VwMAX + VwMIN) / R} / 2. Calculate (step S51), calculate voltage gain deviation Vpperr = {VuMAX−VuMIN) − (IwMAX−IwMIN)} / 2 (step S52), and calculate current gain deviation Iperr = {(IuMAX−IuMIN) − (IwMAX−IwMIN). )} / 2 (step S53), gain deviation Pperr = Vpp / R + Ipperr is calculated (step S54), and a failure is determined (step S55).
[0076]
In this way, a failure of the current sensor can be reliably detected.
[0077]
Next, an electric power steering apparatus according to a third embodiment of the present invention will be described. In the third embodiment, the drive voltage monitoring unit and the detected current monitoring unit in the control device 22 of the electric power steering apparatus shown in FIG. 1 are changed as described later. Since other components are the same, description thereof is omitted.
[0078]
FIG. 16 is a diagram showing a drive voltage monitoring unit and a detection current monitoring unit in the third embodiment. The drive voltage monitoring unit in the third embodiment includes a first drive voltage monitoring unit 130 and a second drive voltage monitoring unit 131, and the detection current monitoring unit includes the first detection current monitoring unit 132 and the second drive voltage monitoring unit 132. The first drive voltage monitoring unit 130 includes voltage estimation units 109 and 111 that estimate the voltage of the other phase from the drive voltage of any phase and the rotation angle of the motor, A first drive voltage abnormality signal generation unit 112 that generates a drive voltage abnormality signal by comparing the phase drive voltage with the estimated voltage estimated by the voltage estimation units 109 and 111, and a second drive voltage monitoring unit Reference numeral 131 denotes a voltage maximum value / minimum value detection unit 121, 122 for detecting the maximum value and the minimum value of data for one cycle of the driving voltage of each phase in which the current sensors 206, 207 are arranged, and a voltage maximum value minimum Value detectors 121 and 12 And a second drive voltage abnormality signal generation unit 123 that generates a drive voltage abnormality signal from the maximum value and the minimum value detected by the first detection current monitoring unit 132. The current estimation units 114 and 116 that estimate the current of the other phase from the rotation angle of the motor, and the detected current of the other phase and the estimated current estimated by the current estimation units 114 and 116 are compared to generate an abnormal signal of the detected current. The second detection current monitoring unit 133 includes a first detection current abnormality signal generation unit 117 to be generated, and the second detection current monitoring unit 133 is a maximum value of data for one cycle of the detection current of each phase detected by the current sensors 206 and 207. Current maximum value / minimum value detection units 125 and 126 for detecting the minimum value, and an abnormality signal of the detected current is generated from the maximum value and the minimum value detected by the current maximum value / minimum value detection units 125 and 126. Two detection current abnormality signal generation units 127, and according to the number of rotations, the first drive voltage monitoring unit 130, the first detection current monitoring unit 132, the second drive voltage monitoring unit 131, and the second drive voltage monitoring unit 131 Switching sections 134 and 135 for switching between the detected current monitoring section 133 are provided.
[0079]
In this configuration, the first drive voltage monitoring unit 130 and the first detected current monitoring unit 132 are the same as the configurations of the drive voltage monitoring unit 101 and the detected current monitoring unit 102 in the first embodiment, and Since the second drive voltage monitoring unit 131 and the second detection current monitoring unit 133 are the same as the configuration of the drive voltage monitoring unit 120 and the detection current monitoring unit 124 in the second embodiment, the same reference numerals are used for explanation. The switching units 134 and 135 will be described.
[0080]
The switching units 134 and 135 receive the angular velocity signal ω from the rotational velocity calculation unit 208, and when the angular velocity signal ω is equal to or lower than a predetermined angular velocity (for example, 20 deg / s), the switching unit 134 and 135 1 is switched to the detected current monitoring unit 132, and failure detection is performed as described in the first embodiment. When the angular velocity is higher than the predetermined angular velocity, the second drive voltage monitoring unit 131 and the second detection current monitoring unit 133 are switched to perform failure detection as described in the second embodiment.
[0081]
As a result, the failure detection in the first embodiment is erroneously detected due to the effect of the phase shift except when the steering speed is sufficiently low, and for one cycle in the case of no rotation in the second embodiment. It is possible to solve the problem that the data cannot be detected because the data cannot be acquired. That is, when the rotational speed of the motor is low (up to 20 deg / sec on the handle), it is detected by the first drive voltage monitoring unit 130 and the first detected current monitoring unit 132, and when the rotational speed is high (5 deg / up on the handle). (second or more) is detected by the second drive voltage monitoring unit 131 and the second detection current monitoring unit 133. As a result, detection is possible at all rotational speeds. On the handle, between 5 deg / sec and 20 deg / sec, monitoring is performed in both the first and second, and switching occurs during failure detection, and the failure detection time is prevented from becoming longer.
[0082]
【The invention's effect】
As is apparent from the above description, the present invention has the following effects.
[0083]
Current control works so that the target current and the actual current match, and when the target current and the actual current match, the failure is determined by the abnormal signal detected by the drive voltage monitoring means, while the detected torque If the target current is set so that there is no pulsation, and no abnormal signal appears in the voltage that drives the motor, the failure is determined by the abnormal signal detected by the detected current monitoring means. Regardless of the effectiveness of steering device control (whether it is a dead zone or the strength of control due to vehicle speed response), failure detection is possible in all situations. Also, by unifying the unit of the amount detected by the current and the amount detected by the voltage, the amount of failure of the current sensor can be estimated, and an action can be taken according to the degree of failure of the sensor. it can.
[0084]
Further, since the detection current monitoring means is configured using a signal calculated from the two-phase detection current, it is not necessary to use the third current sensor, and the cost is not increased.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of an electric power steering apparatus according to a first embodiment of the present invention.
FIG. 2 is a diagram showing a specific configuration of a main part and an electric system of a mechanical mechanism of the electric power steering apparatus.
FIG. 3 is a cross-sectional view taken along line AA in FIG.
4 is a cross-sectional view taken along line BB in FIG. 3. FIG.
FIG. 5 is a block configuration diagram of a current control unit.
FIG. 6 is a graph showing waveforms before and after three-phase two-axis conversion when a current sensor fails.
FIG. 7 is a schematic diagram for explaining control in the electric power steering apparatus.
FIG. 8 is a diagram illustrating a ratio appearing in a drive voltage and a ratio appearing in a detection current corresponding to a failure of the current sensor.
FIG. 9 is a diagram illustrating a procedure of a method for calculating a resistance value of a motor.
FIG. 10 is a block configuration diagram of a drive voltage monitoring unit and a detection current monitoring unit in the first embodiment.
FIG. 11 is a current sensor failure detection flowchart in the first embodiment;
FIG. 12 is a graph illustrating detection of a current sensor failure amount in the first embodiment.
FIG. 13 is a block configuration diagram of a drive voltage monitoring unit and a detection current monitoring unit in the second embodiment.
FIG. 14 is a graph illustrating detection of a current sensor failure amount in the second embodiment.
FIG. 15 is a current sensor failure detection flowchart in the second embodiment;
FIG. 16 is a block configuration diagram of a drive voltage monitoring unit and a detection current monitoring unit in the third embodiment.
FIG. 17 is a block configuration diagram of a control device of a conventional electric power steering device.
[Explanation of symbols]
10 Electric power steering device
11 Steering wheel
12 Steering shaft
18 Power transmission mechanism
19 Brushless motor
20 Steering torque detector
20d Rudder angle sensor
22 Control device
23 Motor rotation angle detector (angle sensor)
100 Current controller
101 Drive voltage monitoring unit
102 Detection current monitoring unit
103 Failure detection unit
104 Failure indicator
206 Current sensor
207 Current sensor

Claims (4)

Target current determining means for determining a target current based on the steering torque, a three-phase brushless motor for generating assist torque, a current sensor for detecting two-phase current among the three phases of the three-phase brushless motor, and the two-phase Calculating means for calculating a current of one phase remaining from the current of the motor, an angle sensor for detecting a rotation angle of the three-phase brushless motor, and generating a motor current control signal based on the rotation angle, the detected current and the target current An electric power steering apparatus comprising: current control means for performing drive voltage monitoring means for monitoring drive voltage of the three-phase brushless motor; and detection current monitoring means for monitoring detected drive current of the three-phase brushless motor .
A first failure detection current is calculated from the drive voltage input to the drive voltage monitoring means, a second failure detection current is calculated from the current input to the detection current monitoring means, and the first failure detection current and the first failure detection current are calculated. 2. An electric power steering apparatus comprising a failure detection means for determining a failure of the current sensor based on a sum of two failure detection currents . The drive voltage monitoring means includes a voltage estimation means for estimating a voltage of another phase from the drive voltage of any phase and the rotation angle of the motor, and an estimation estimated by the drive voltage of the other phase and the voltage estimation means. Drive voltage abnormality signal generating means for comparing the voltages and generating a drive voltage abnormality signal,
The detection current monitoring means includes a current estimation means for estimating a current of another phase from a detection current of any phase and a rotation angle of the motor, and a detection current estimated by the detection current of the other phase and the current estimation means. 2. The electric power steering apparatus according to claim 1, further comprising detected current abnormality signal generation means for generating a detected current abnormality signal by comparing the two. The drive voltage monitoring means includes a voltage maximum value / minimum value detection means for detecting a maximum value and a minimum value of data for one cycle of the drive voltage of each phase in which the current sensor is disposed, and the voltage maximum value minimum Drive voltage abnormality signal generating means for generating a drive voltage abnormality signal from the maximum value and the minimum value detected by the value detection means,
The detection current monitoring means includes a current maximum value / minimum value detection means for detecting a maximum value and a minimum value of data for one cycle of the detection current of each phase detected by the current sensor, and the current maximum value / minimum value. 2. The electric power steering apparatus according to claim 1, further comprising detected current abnormality signal generating means for generating an abnormality signal of a detected current from the maximum value and the minimum value detected by the detecting means. The drive voltage monitoring means comprises a first drive voltage monitoring means and a second drive voltage monitoring means, and the detection current monitoring means comprises a first detection current monitoring means and a second detection current monitoring means,
The first drive voltage monitoring means is estimated by a voltage estimation means for estimating a voltage of another phase from the drive voltage of any phase and the rotation angle of the motor, and estimated by the drive voltage of the other phase and the voltage estimation means. A first drive voltage abnormality signal generating means for comparing the estimated voltages to generate a drive voltage abnormality signal,
The second drive voltage monitoring means includes a voltage maximum value / minimum value detection means for detecting a maximum value and a minimum value of data for one cycle of the drive voltage of each phase in which the current sensor is disposed, and the voltage A second drive voltage abnormality signal generating means for generating a drive voltage abnormality signal from the maximum value and the minimum value detected by the maximum value / minimum value detection means;
The first detection current monitoring means is estimated by a current estimation means for estimating a current of another phase from a detection current of any phase and a rotation angle of the motor, and a detection current of the other phase and the current estimation means. Comprising a first detected current abnormality signal generating means for comparing the estimated currents generated to generate an abnormality signal of the detected current,
The second detection current monitoring means includes a current maximum value / minimum value detection means for detecting a maximum value and a minimum value of data for one cycle of the detection current of each phase detected by the current sensor, and the current maximum A second detected current abnormality signal generating means for generating an abnormality signal of a detected current from the maximum value and the minimum value detected by the value minimum value detecting means,
There is provided switching means for switching between the first drive voltage monitoring means, the first detection current monitoring means, the second drive voltage monitoring means, and the second detection current monitoring means in accordance with the rotational speed. The electric power steering apparatus according to claim 1.

Images