JP2004050972A - Electric power steering device - Google Patents

Abstract

The present invention relates to an electric power steering apparatus, which can perform appropriate steering assist without requiring a torque sensor, thereby improving steering feeling at low cost.
A current detection unit detects current i flowing through a DC motor, and a control unit controls the operation of the DC motor by feedback-controlling a motor load voltage value applied to the DC motor. The control means 30 uses the motor load voltage value v to the DC motor 11, the detected motor current value i, and the yaw rate r of the vehicle based on a steering-vehicle system model including the DC motor 11, Estimating means 31 for estimating at least the driver torque Th applied to the steering-vehicle system, and setting means 32 for setting a target motor load voltage value to be applied to the DC motor 11 according to the estimated driver torque Th are provided. The set target motor load voltage value is provided to the DC motor 11.
[Selection diagram] Fig. 1

Description

【００２１】
ここで、外乱ｗを状態変数に拡張すると、次式（４）が得られる。
【００２２】
【数２】

【００２３】
式（４）に基づいて、電流ｉを観測値（検出値）とした場合のオブザーバの状態方程式を示すと、次式（５）のようになる。
【００２４】
【数３】

【００２５】
上記の状態方程式（５）において、ｉ_ｅ，ω_ｅ，ｗ_ｅはいずれも状態量としての推定値（前述のモータ電流推定値，モータ角速度推定値，外乱トルク推定値）であり、ｌ_ｍ１，ｌ_ｍ２，ｌ_ｍ３はいずれも係数である。ここで、係数ｌ_ｍ１，ｌ_ｍ２，ｌ_ｍ３を定めることによって、状態量ｉ_ｅ，ω_ｅ，ｗ_ｅを推定するオブザーバを構成することができる。また、係数ｌ_ｍ１，ｌ_ｍ２，ｌ_ｍ３は周波数特性を考慮した数式演算によって、適正値を設定することができる。
【００２６】
また、操舵−車両系１は、図３に示すようにモデル化することができる。
ただし、図３において、ω_ｅ，δ_ｅ，β_ｅ，ｒ_ｓ，ｒ_ｅはいずれも変数（状態量）であって、ω_ｅはモータ角速度の推定値、δ_ｅは前輪実舵角（操舵角）の推定値、β_ｅは車両の重心スリップ角の推定値、ｒ_ｓは車両のヨーレイトの検出値、ｒ_ｅは車両のヨーレイトの推定値、ω_ｅはモータ角速度の推定値、ｗ_ｅは外乱トルクの推定値（＝ドライバトルク推定値Ｔ_ｈｅと操舵反力トルク推定値Ｔ_ｃｅとの加算値、ｗ_ｅ＝Ｔ_ｈｅ＋Ｔ_ｃｅ）である。また、Ｋ_ｇ，ｍ，Ｉ，Ｖ，Ｋ_ｆ，Ｋ_ｒ，ｌ_ｆ，ｌ_ｒはいずれもモータ制御系に固有のパラメータ（定数値）であって、Ｋ_ｇは操舵ギア比（モータ位相角度と前輪（操舵輪）舵角との比）、ｍは車両の質量、Ｉは車両の慣性モーメント、Ｖは車速、Ｋ_ｆは前輪コーナリングパワー、Ｋ_ｒは後輪コーナリングパワー、ｌ_ｆは重心から前輪軸までの距離、ｌ_ｒは重心から後輪軸までの距離である。ｌ_ｖ１〜ｌ_ｖ３はオブザーバの定数である。
【００２７】
このようなモデルから、操舵角δ_ｅの微分方程式は次式（６）のように、重心スリップ角β_ｅの微分方程式は次式（７）のように、ヨーレイトｒ_ｓの微分方程式は次式（８）のように、たてることができる。
ｄδ_ｅ／ｄｔ＝ω_ｅ／Ｋ_ｇ　　　　　　　　　　　　　　・・・（６）
ｄβ_ｅ／ｄｔ＝（２Ｋ_ｆ／ｍＶ）δ_ｅ−［ｍＶ^２＋２（ｌ_ｆＫ_ｆ−ｌ_ｒＫ_ｒ）／ｍＶ^２］ｒ_ｅ−［２（Ｋ_ｆ＋Ｋ_ｒ）／ｍＶ］β_ｅ　　　　　・・・（７）
ｄｒ_ｅ／ｄｔ＝（２ｌ_ｆＫ_ｆ／Ｉ）δ_ｅ−［２（ｌ_ｆＫ_ｆ−ｌ_ｒＫ_ｒ）／Ｉ］β_ｅ−［２（ｌ_ｆ ^２Ｋ_ｆ＋ｌ_ｒ ^２Ｋ_ｒ）／ＩＶ］ｒ_ｅ　・・・（８）
式（６）〜（８）を状態方程式で表現すると、次式（９）のようになる。
【００２８】
【数４】

【００２９】
式（９）に基づいてヨーレイト検出値ｒ_ｓを観測値とし、モータ角速度推定値ω_ｓｅを入力値とした場合のオブザーバの状態方程式を示すと次式（１０）のようになる。
【００３０】
【数５】

【００３１】
上記の状態方程式（１０）において、δ_ｅ，β_ｅ，ｒ_ｅはいずれも状態量としての推定値（前述の前輪実舵角推定値，重心スリップ角推定値，ヨーレイト推定値）であり、ｌ_ｖ１，ｌ_ｖ２，ｌ_ｖ３はいずれも係数である。ここで、係数ｌ_ｖ１，ｌ_ｖ２，ｌ_ｖ３を定めることによって、状態量δ_ｅ，β_ｅ，ｒ_ｅを推定するオブザーバを構成することができる。また、係数ｌ_ｖ１，ｌ_ｖ２，ｌ_ｖ３は周波数特性を考慮した数式演算によって、適正値を設定することができる。
【００３２】
演算部３１ｂでは、このようなオブザーバ３１ａによる推定結果から演算によってドライバトルク推定値Ｔ_ｈｅを求める。
つまり、前輪タイヤの横滑り角β_ｆｅと操舵反力（セルフアライニングトルク）との関係を求めると、前輪タイヤの横滑り角β_ｆｅは、次式（１１）で算出することができる。
β_ｆｅ＝β_ｅ＋（ｌ_ｆ／Ｖ）ｒ_ｅ−δ_ｅ　　　　　　　　　　　　　　・・・（１１）
前輪タイヤの横滑り角β_ｆｅが小さい領域では、キングピン軸回りの操舵反力トルクＴ_ｓｅは、次式（１２）で算出することができる（ただし、ξは復元モーメントトレールである）。
Ｔ_ｓｅ＝２ξＫ_ｆβ_ｆｅ　　　　　　　　　　　　　　　　　　　　・・・（１２）
ただし、ξは復元モーメントトレールである。
【００３３】
ここで、キングピン軸回りの操舵反力トルクＴ_ｓｅをコラム軸（操舵軸）回りの操舵反力トルクＴ_ｃｅに換算すると、次式（１３）のようになる。
Ｔ_ｃｅ＝（２ξＫ_ｆ／Ｋ_ｇ）β_ｆｅ　　　　　　　　　　　　　　　　・・・（１３）
ただし、Ｋ_ｇはステアリングギア比である。
したがって、演算部３１ｂでは、次式（１４）に示すように、上記の推定値ｗ_ｅ，β_ｅ，ｒ_ｅ，δ_ｅからドライバトルク推定値Ｔ_ｈｅを算出することができる。
Ｔ_ｈｅ＝ｗ_ｅ−Ｔ_ｃｅ＝ｗ_ｅ−（２ξＫ_ｆ／Ｋ_ｇ）β_ｆｅ
＝ｗ_ｅ−（２ξＫ_ｆ／Ｋ_ｇ）［β_ｅ＋（ｌ_ｆ／Ｖ）ｒ_ｅ−δ_ｅ］　　　　・・・（１４）
制御量設定部３２は、このように推定されたモータ電流推定値ｉ_ｅ（この推定値はモータ電流検出値ｉ_ｓで置き換えることができる），モータ角速度推定値ω_ｅ，ドライバトルク推定値Ｔ_ｈｅ，前輪操舵角推定値δ_ｅ，重心スリップ角推定値β_ｅ及びヨーレイト推定値ｒ_ｅ（この推定値はヨーレイト検出値ｒ_ｓで置き換えることができる）と車速検出手段（車速センサ）４２からの検出情報とを入力され、各推定値ｉ_ｅ，ω_ｅ，Ｔ_ｈｅ，δ_ｅ，β_ｅ，ｒ_ｅを、それぞれの速度対応ゲインＫ_ｉ，Ｋ_ω，Ｋ_Ｔｈ，Ｋ_δ，Ｋ_β，Ｋ_ｒで乗算処理し、これらを、次式（１５）のように加算して目標電圧値ｖ_ｔを設定するようになっている。
ｖ_ｔ＝−Ｋ_ｉ・ｉ_ｅ−Ｋ_ω・ω_ｅ＋Ｋ_Ｔｈ・Ｔ_ｈｅ−Ｋ_δ・δ_ｅ−Ｋ_β・β_ｅ−Ｋ_ｒ・ｒ_ｅ・・・（１５）
なお、速度対応ゲインＫ_ｉ，Ｋ_ω，Ｋ_Ｔｈ，Ｋ_δ，Ｋ_β，Ｋ_ｒはそれぞれ図４に示すような特性で設定される。
【００３４】
モータ電流制御ゲインＫ_ｉは、図４（ａ）に示すように、車速にほとんど依存せずにほぼ定数に設定されており、目標電圧値ｖ_ｔに値Ｋ_ｉ・ｉ_ｅを反映させることで、制御の動特性が向上するようになっている。
モータ角速度制御ゲインＫ_ωは、図４（ｂ）に示すように、車速の増大に応じて増加するように設定されており、目標電圧値ｖ_ｔに値Ｋ_ω・ω_ｅを反映させることで、急操舵された際などに過剰な角速度の発生を抑制するようになっている。
【００３５】
ドライバトルク制御ゲインＫ_Ｔｈは、図４（ｃ）に示すように、車速の増大に応じて減少するように設定されており、車速が高くなるほど目標電圧値ｖ_ｔを小さくして、操舵アシストトルクＴ_ｍを減少させるようになっている。これは、車速が高いほど操舵安定感（保舵感）を重視して操舵アシストを弱め、逆に、車速が低いほど操舵操作を容易にできるように操舵アシストを強めるようにしているのである。速度対応ゲインＫ_ｉ，Ｋ_ω，Ｋ_Ｔｈのうちこのドライバトルク制御ゲインＫ_Ｔｈが最も大きく設定され、ドライバトルク制御ゲインＫ_Ｔｈが目標電圧値ｖ_ｔに最も大きく影響するようになっている。
【００３６】
前輪操舵角制御ゲインＫ_δは、図４（ｄ）に示すように、低車速時には負の値となって、車速の増加に応じて増加（負の値の場合には値の大きさが小さくなる）して高車速時には正の値となるように設定されている。ただし、極低速時には、車速の増加に応じて減少（負の値であって、絶対値の大きさは車速増加に応じて増加する）ようになっている。低速時に前輪操舵角制御ゲインＫ_δが負に設定されているのは、操舵角と同じ向きにアシストトルクを与えて操舵操作を容易にするためである。高速になるのに従って前輪操舵角制御ゲインＫ_δが増加して正になるように設定されているのは、車速が高いほど操舵安定感を重視すると共に、高速走行時の操舵フィーリングを向上させようとするものである。
【００３７】
重心スリップ角制御ゲインＫ_βは、図４（ｅ）に示すように、車速の増加に応じて増加するように設定されている。ただし、極低速時には、車速の増加に応じて急増しその後は緩やかに増加するようになっている。これは、低速から高速まで車両の安定性を保つと共に操舵フィーリングを向上させようとするものである。
ヨーレイト制御ゲインＫ_ｒは、図４（ｆ）に示すように、低車速時には０で、高中車速時には車速の増加に応じて増加するように設定されている。これも、上記と同様に、低速から高速まで車両の安定性を保つと共に操舵フィーリングを向上させようとするものである。
【００３８】
本発明の第１実施形態としての電動パワーステアリング装置は、上述のように構成されているので、モータ指令値であるモータ付加電圧ｖと電流センサ２１で検出されるモータ電流ｉとヨーレイトセンサ２３で検出されるヨーレイトｒから、操舵トルク（ドライバトルク）Ｔｈを推定して、この推定したドライバトルクＴ_ｈに応じて、モータ１１の付加電圧ｖを制御することにより、モータトルクＴ_ｍを調整するので、トルクセンサを要することなく、演算ソフトを追加するだけで、ドライバの操舵負荷状態に応じて適切に操舵アシストを実施することができる。すなわち、低コストで操舵フィーリングを向上させることができる。
【００３９】
また、ドライバトルクＴ_ｈを、車速の増大に応じて減少するように設定されるドライバトルク制御ゲインＫ_Ｔｈにより処理した上で、モータ１１の付加電圧ｖを制御するので、車速が低いほど操舵アシストが強められ操舵操作を容易にできるようになり、車速が高いほど操舵アシストが弱められ操舵安定感（保舵感）が増大し、操舵アシストを車速に応じて適切に実施することができる。
【００４０】
また、本実施形態では、モータ１１の付加電圧ｖの制御にモータ電流ｉをモータ電流制御ゲインＫ_ｉで処理した上で反映させているので、制御の動特性を向上させることができ、応答性のよい操舵アシスト制御を実現できる。
また、モータ１１の付加電圧ｖの制御にモータ角速度ωをモータ角速度制御ゲインＫωで処理した上で反映させているので、過剰な角速度の発生を抑制することができ、モータの保護も図ることができる。
【００４１】
さらに、モータ１１の付加電圧ｖの制御に前輪操舵角δを前輪操舵角制御ゲインＫ_δで処理した上で反映させているので、据え切り操舵の容易性を考慮しながら低速時にステアリング操作を容易にすることができると共に、高速走行時の操舵フィーリングを向上させることができる。
また、モータ１１の付加電圧ｖの制御に重心スリップ角βを重心スリップ角制御ゲインＫ_βで処理した上で反映させていることや、モータ１１の付加電圧ｖの制御にヨーレイトｒをヨーレイト制御ゲインＫ_ｒで処理した上で反映させていることにより、高速走行時の操舵フィーリングを向上させることができる。
【００４２】
なお、制御の動特性に特に課題がなければ、モータ１１の付加電圧ｖの制御にモータ電流ｉを反映させる必要はなく、モータ１１に過剰な角速度が発生するおそれがなければ、モータ１１の付加電圧ｖの制御にモータ角速度ωを反映させる必要はない。
また、操舵フィーリングを微妙に調整する必要が低ければ、モータ１１の付加電圧ｖの制御に、前輪操舵角δや重心スリップ角βやヨーレイトｒの一部を反映させるようにしたり、或いは、これらを反映させないようにしたりして、制御の簡素化を図ることもできる。
【００４３】
つぎに、本発明の第２実施形態を説明すると、図５は本発明の第２実施形態としての電動パワーステアリング装置の機能構成を示すブロック図である。
本実施形態は、上述第１実施形態で説明したように、トルクセンサを用いずに操舵アシストを制御する手法を、トルクセンサ付き電動パワーステアリング装置におけるトルクセンサ故障時のバックアップとして利用するものである。
【００４４】
つまり、本実施形態では、従来のトルクセンサ付き電動パワーステアリング装置に対して、トルクセンサ故障検出装置を追加するとともに、電動パワーステアリング制御装置に、適宜のソフトウェア，ハードウェアを追加して、トルクセンサ故障検出装置によりトルクセンサの故障の発生が検出されると、表示装置を通じてドライバに対してこの故障発生を知らせる一方で、トルクセンサを利用しない上述の手法を適用して操舵アシストを継続するようにしている。
【００４５】
具体的には、図５に示すように、操舵トルクを検出する操舵トルクセンサ（操舵トルク検出手段）５１を設け、ＥＣＵ３０には、この操舵トルクセンサ５１からの実操舵トルクの検出信号に基づいて実操舵トルクに対応してＤＣモータ２の付加電圧ｖを設定する第１制御量設定部（設定手段）５２を設け、操舵トルクセンサ５１が正常に作動しているときには、この第１制御量設定部５２により実操舵トルクに基づいて設定された付加電圧ｖをＤＣモータ２に与えて、実操舵トルクに対応して操舵アシストを行なうようにする。
【００４６】
さらに、上述の実施形態の制御量設定部３２、つまり、オブザーバ３１の推定に基づいてＤＣモータ２の付加電圧ｖを設定する制御量設定部３２をバックアップ用の第２制御量設定部（設定手段）３２´として設ける。そして、操舵トルクセンサ５１の故障を検出する操舵トルクセンサ故障検出手段５３を設けるとともに、故障検出手段５３により操舵トルクセンサ５１の故障が検出されたら、第１制御量設定部５２に代えて第２制御量設定部３２´によりＤＣモータ２の付加電圧ｖの設定を行なうように切り換える制御量設定切換部５４を設ける。
【００４７】
本発明の第２実施形態としての電動パワーステアリング装置は、上述のように構成されているので、操舵トルクセンサ５１が故障した場合にも、第２制御量設定部３２´によりＤＣモータ２の付加電圧ｖの設定を行なうことができるようになる。
すなわち、トルクセンサ故障時でも、操舵アシストが不可能になる事態を回避でき、常に操舵フィーリングを向上させることが可能になる。
【００４８】
また、トルクセンサの故障対策としては、予備のトルクセンサを別に設けることも考えられるが、本実施形態の構成を適用することで予備のトルクセンサが不要になる。
さらに、２つのトルクセンサをそなえた電動パワーステアリング装置において本実施形態の構成を適用すると、何れか一方のトルクセンサが故障して２つのトルクセンサの出力値の差が所定値以上になった場合に、ドライバトルクの推定値と２つのトルクセンサの出力値とを比較して、ドライバトルクの推定値との差が少ない方のトルクセンサの出力を利用して操舵アシストを継続する一方で、トルクセンサの故障を報知すればよい。この場合、何れのセンサが故障しているかがわかるので、故障しているトルクセンサを区別できるように報知することもできる。また、２つのトルクセンサの両方が故障した場合には、ドライバトルクの推定値を利用して操舵アシスト制御を継続させることもできる。
【００４９】
以上、本発明の実施形態を説明したが、本発明はかかる実施形態に限定されるものではなく、本発明の趣旨を逸脱しない範囲で種々変形して実施することができる。
例えば、速度対応ゲインＫ_ｉ，Ｋ_ω，Ｋ_Ｔｈ，Ｋ_δ，Ｋ_β，Ｋ_γについては、図４に各設定例を示したが、速度対応ゲインＫ_ｉ，Ｋ_ω，Ｋ_Ｔｈ，Ｋ_δ，Ｋ_β，Ｋ_γの設定特性はこれに限るものではなく、系の安定性や操舵フィーリングを向上させることができるように、速度対応ゲインＫ_ｉ，Ｋ_ω，Ｋ_Ｔｈ，Ｋ_δ，Ｋ_β，Ｋ_γを車速に応じて適宜設定することが重要である。
【００５０】
また、制御量設定部３２に、速度対応ゲイン処理機能に加えて、位相進み補償器や位相遅れ補償器を追加して、位相を調整するようにして、より適切に操舵アシスト制御を行なうことも考えられる。
【００５１】
【発明の効果】
以上詳述したように、本発明の電動パワーステアリング装置（請求項１）によれば、トルクセンサを要することなく、演算ソフトを追加するだけで、ドライバの操舵付加状態に応じて適切に操舵アシストを実施することができ、低コストで操舵フィーリングを向上させることができる。
【００５２】
さらに、該推定手段を、該ＤＣモータへのモータ付加電圧値と、該電流検出手段により検出されたモータ電流値と、該ヨーレイト検出手段により検出された車両のヨーレイトとを用いて、該ＤＣモータを含む操舵−車両系制御系のモデルに基づいて、該ＤＣモータの制御系に加わる該ドライバトルクに加えて、該ＤＣモータの角速度，該車両の操舵輪の舵角及び該車両の重心スリップ角のうちの少なくともいずれかを推定するとともに、該設定手段は、該電流検出手段により検出された該電流値と該ヨーレイト検出手段により検出された車両のヨーレイトと該推定手段により推定された各推定値とに応じて、該ＤＣモータへ与えるべき目標モータ付加電圧値を設定するように構成すれば、制御の動特性を向上させ応答性のよい操舵アシスト制御を実現することや、モータにおける過剰な角速度の発生を抑制して、モータの保護を図ることや、きめの細かい操舵フィーリングの向上が可能になる（請求項２）。
【００５３】
設定手段が、電流検出手段により検出された電流値とヨーレイト検出手段により検出された車両のヨーレイトと推定手段により推定された各推定値と、車速検出手段により検出された車速とに応じて、ＤＣモータへ与えるべき該目標モータ付加電圧値を設定することことで、車速に応じて綿密に操舵アシストを制御することができる（請求項４，５）。
【００５４】
また、本発明の電動パワーステアリング装置（請求項６）によれば、トルクセンサ故障時でも、操舵アシストが不可能になる事態を回避でき、常に操舵フィーリングを向上させることが可能になる。
【図面の簡単な説明】
【図１】本発明の第１実施形態としての電動パワーステアリング装置の機能構成を示すブロック図である。
【図２】本発明の第１実施形態としての電動パワーステアリング装置にかかるモータ制御系の状態量を推定するオブザーバのブロック図である。
【図３】本発明の第１実施形態としての電動パワーステアリング装置にかかる操舵−車両系の状態量を推定するオブザーバのブロック図である。
【図４】本発明の第１実施形態としての電動パワーステアリング装置における制御に用いる速度対応制御ゲインの特性を示す図であって、（ａ）はモータ電流に関する制御ゲインを示し、（ｂ）はモータ角速度に関する制御ゲインを示し、（ｃ）はドライバトルクに関する制御ゲインを示し、（ｄ）は前輪操舵角に関する制御ゲインを示し、（ｅ）は重心スリップ角に関する制御ゲインを示し、（ｆ）はヨーレイトに関する制御ゲインを示す。
【図５】本発明の第２実施形態としての電動パワーステアリング装置の機能構成を示すブロック図である。
【符号の説明】
１　操舵−車両系
１１　ＤＣモータ
２１　電流検出手段
２２　車速検出手段
２３　ヨーレイト検出手段
３０　制御手段としての電子制御ユニット（ＥＣＵ）
３１　推定手段
３１ａ　オブザーバ
３１ｂ　ドライバトルク演算部
３２　設定手段としての制御量設定部
３２´　第２制御量設定部（設定手段）
４１　モータトルク演算部
５１　操舵トルクセンサ（操舵トルク検出手段）
５２　第１制御量設定部（設定手段）
５３　操舵トルクセンサ故障検出手段[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electric power steering device mounted on a vehicle and assisting steering using a DC motor.
[0002]
[Prior art]
As a power steering device for an automobile, a hydraulic power steering device has become widespread, but an electric power steering device is more advantageous for performing fine-grained steering assist control. Is being developed.
In such an electric power steering device, a steering torque sensor that detects a steering torque applied to a steering system and a vehicle speed detection sensor that detects a vehicle speed are provided, and the steering torque sensor detects the steering torque and the vehicle speed detected by these sensors. Therefore, it is common to control the assist torque by the motor.
On the other hand, in order to further improve the steering feeling, a control method for compensating the inertia, viscosity, and the like of the steering system based on the angular velocity and the angular acceleration of the motor has been proposed.
[0003]
From this point of view, Japanese Patent No. 3133914 discloses an electric power steering apparatus for performing PWM control on a motor connected to a steering system by a circuit having a low-pass characteristic of a cutoff frequency lower than a PWM carrier frequency. There has been proposed a technique of detecting a motor applied voltage by removing a component and estimating a motor angular velocity based on the motor applied voltage.
[0004]
[Problems to be solved by the invention]
However, in the technology related to the conventional electric power steering device, although finer steering assist can be realized and the steering feeling can be improved, a steering torque sensor is required for controlling the assist torque by the control motor, This causes a problem that the steering assist cannot be performed when the cost increases or the torque sensor fails.
[0005]
The present invention has been made in view of the above-described problems, and provides an electric power steering device capable of improving steering feeling by performing appropriate steering assist without requiring a torque sensor. The purpose is to provide.
[0006]
[Means for Solving the Problems]
Therefore, an electric power steering apparatus according to the present invention is an electric power steering apparatus mounted on a vehicle and assisting steering using a DC motor, and a current detecting means for detecting a current flowing through the DC motor. A yaw rate detecting means for detecting a yaw rate of the vehicle; and a control means for controlling the operation of the DC motor by feedback-controlling a motor additional voltage value to the DC motor. Estimating a driver torque applied to the control system of the DC motor using a motor additional voltage value to the motor, a motor current value detected by the current detecting means, and a yaw rate of the vehicle detected by the yaw rate detecting means. And a target to be given to the DC motor in accordance with the driver torque estimated by the estimating means. And a setting means for setting the over data additional voltage value, configured to provide the target motor additional voltage value set by said setting means to said DC motor.
[0007]
The estimating means uses the motor added voltage value to the DC motor, the motor current value detected by the current detecting means, and the yaw rate of the vehicle detected by the yaw rate detecting means to calculate the DC motor Based on the model of the control system of the steering-vehicle system including the driver torque applied to the control system of the DC motor, the angular velocity of the DC motor, the steering angle of the steered wheels of the vehicle, and the center of gravity slip of the vehicle At least one of the angles is estimated, and the setting unit is configured to determine the current value detected by the current detection unit, the yaw rate of the vehicle detected by the yaw rate detection unit, and each of the estimations estimated by the estimation unit. It is preferable to set a target motor additional voltage value to be given to the DC motor according to the value (claim 2).
[0008]
Further, the estimating means calculates the motor current value as a state quantity, the angular velocity of the DC motor, the disturbance torque, and the vehicle torque from the motor additional voltage value, the motor current value as the state quantity, and the yaw rate of the vehicle. An observer for estimating at least one of a steering angle of a steered wheel, a slip angle of the center of gravity of the vehicle, and a yaw rate of the vehicle; and calculating the driver torque based on the estimated amount estimated by the observer. It is preferable that the driving circuit includes a driver torque calculator.
[0009]
Vehicle speed detecting means for detecting the vehicle speed of the vehicle; and the setting means estimates the current value detected by the current detecting means, the yaw rate of the vehicle detected by the yaw rate detecting means, and the estimating means. It is preferable that the target motor additional voltage value to be applied to the DC motor is set according to each estimated value and the vehicle speed detected by the vehicle speed detecting means.
[0010]
The setting means calculates a sum of values obtained by multiplying the current value, the yaw rate, and the respective estimated values estimated by the estimating means with respective control gains set in accordance with the vehicle speed. It is preferable to set the additional voltage value.
An electric power steering apparatus according to the present invention includes a steering torque sensor mounted on a vehicle and detecting a steering torque applied to a steering system, and a DC based on the steering torque detected by the steering torque sensor. An electric power steering apparatus for assisting steering using a motor, a steering torque sensor failure detecting means for detecting a failure of the steering torque sensor, a current detecting means for detecting a current flowing through the DC motor, and the DC motor And control means for controlling the applied voltage to the power supply. When the steering torque sensor failure detecting means detects the failure of the steering torque sensor, the control means includes: a motor additional voltage value to the DC motor; a motor current value detected by the current detecting means; Estimating means for estimating at least a disturbance torque applied to a control system of the DC motor based on a model of a control system of a steering-vehicle system including the DC motor, using the yaw rate of the vehicle detected by the detecting means, Setting means for setting a target motor additional voltage value to be applied to the DC motor in accordance with the disturbance torque estimated by the estimating means, and setting the target motor additional voltage value set by the setting means to the DC motor Give to motor.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, a first embodiment of the present invention will be described. FIGS. 1 to 4 show an electric power steering apparatus as a first embodiment of the present invention, and FIG. 1 is a block diagram showing the functional configuration thereof. , FIG. 3 is a block diagram of the observer, and FIG. 4 is a diagram showing characteristics of a speed-related control gain used for the control.
[0012]
As shown in FIG. 1, the electric power steering apparatus includes a control system of a DC motor (the whole system for controlling the output torque and the number of revolutions of the motor using an additional voltage to the motor as a control input, hereinafter referred to as a motor control system). The torque (steering assist torque) T generated by the DC motor 11 with respect to the steering-vehicle system (the entire system of the vehicle steering system and the vehicle body moving by the steering system) 1 including_mTo reduce the driver's steering burden. Steering assist torque T by DC motor 11_mIs applied according to the torque (disturbance torque) w applied to the motor control system, so that the driver's steering load can be reduced with a good feeling.
[0013]
The disturbance torque w in this case is the driver torque T_hAnd the steering reaction torque T received by the vehicle from the road surface_c(W = T_h+ T_c), The disturbance torque w and the steering assist torque T_mAnd will be added.
Also, the steering assist torque T generated by the DC motor 11_mIs based on the operating current (motor current) i of the DC motor 11, that is, the motor torque i_TMultiplied by
[0014]
Further, the DC motor 11 in the present apparatus controls the motor current i by controlling the applied voltage to the motor. In order to control the motor applied voltage v, an electronic control as control means is used. A unit (ECU) 30 is provided.
Therefore, the ECU 30 calculates the driver torque T_hAnd steering reaction torque T_cIs estimated, and mainly the driver torque T_hAnd steering reaction torque T_cAnd a target motor additional voltage value (hereinafter, referred to as a target voltage value) v_tAnd set the target voltage value v_tThe steering assist torque Tm is adjusted by controlling the motor additional voltage v.
[0015]
However, the target voltage value v_tIs the driver torque T_hAnd steering reaction torque T_cNot only the motor current estimated value i_e, Motor angular velocity (angular velocity of DC motor 11) estimated value ω_e, The estimated front wheel steering angle δ_e, Vehicle center-of-gravity slip angle estimated value β_eAnd the estimated yaw rate r of the vehicle_eIt is set according to.
Therefore, the ECU 30 provides the disturbance torque estimated value w_e, Motor current estimated value i_e, Motor angular velocity (angular velocity of DC motor 11) estimated value ω_e, The estimated front wheel steering angle δ_e, Vehicle center-of-gravity slip angle estimated value β_eAnd the estimated yaw rate r of the vehicle_eEstimating means 31 for estimating the estimated values w and the estimated values w estimated by the estimating means 31_e, I_e, Ω_e, Δ_e, Β_e, R_eControl amount (target voltage value) v_tAnd a control amount setting unit 32 as setting means for setting the control amount.
[0016]
The estimating means 31 includes an observer 31a and a driver torque calculator 31b.
In the observer 31a, the motor additional voltage value v and the motor current value i detected by the current detecting means (current sensor) 41_sAnd the yaw rate r of the vehicle detected by the yaw rate detection means (yaw rate sensor or means for calculating the yaw rate) 42_sAnd the disturbance torque estimated value w based on the model of the motor control system._e, Motor current estimated value i_e, Motor angular velocity (angular velocity of DC motor 11) estimated value ω_e, The estimated front wheel steering angle δ_e, Vehicle center-of-gravity slip angle estimated value β_eAnd the estimated yaw rate K of the vehicle_eIs estimated.
[0017]
To further explain the estimation by the observer 31a, the DC motor 11 can be modeled as shown in FIG.
However, in FIG._s, I_e, Ω_eAre variables (state quantities), v is a command value of the input voltage (motor additional voltage), i_sIs the detected value of the current (motor current), i_eIs the estimated current (motor current), ω_eIs the estimated value of the motor angular velocity, w_eIs the estimated value of the disturbance torque (= the estimated driver torque T_heAnd estimated steering reaction torque T_ceAnd w,_e= T_he+ T_ce).
[0018]
L, R, K_T, K_E, I_MAre parameters (constant values) unique to the motor, L is the inductance of the coil, R is the resistance of the coil, K_TIs the torque constant, K_EIs the back EMF constant, I_MIs the moment of inertia of the motor. l_m1~ L_m3Is the observer constant.
From such a model, the differential equation of the motor current can be expressed by the following equation (1), and the differential equation of the motor angular velocity can be expressed by the following equation (2).
[0019]
L (di / dt) + Ri + K_E・ Ω = v ・ ・ ・ (1)
I_M(Dω / dt) = K_T・ I + w ・ ・ ・ (2)
When Expressions (1) and (2) are expressed by a state equation, the following Expression (3) is obtained.
[0020]
(Equation 1)

[0021]
Here, when the disturbance w is extended to a state variable, the following equation (4) is obtained.
[0022]
(Equation 2)

[0023]
Based on equation (4), the state equation of the observer when the current i is an observed value (detected value) is shown as the following equation (5).
[0024]
(Equation 3)

[0025]
In the above equation of state (5), i_e, Ω_e, W_eAre the estimated values as the state quantities (the above-described motor current estimated value, motor angular velocity estimated value, and disturbance torque estimated value)._m1, L_m2, L_m3Are all coefficients. Where the coefficient l_m1, L_m2, L_m3By determining the state quantity i_e, Ω_e, W_eCan be configured. Also, the coefficient l_m1, L_m2, L_m3Can set an appropriate value by a mathematical operation in consideration of frequency characteristics.
[0026]
Further, the steering-vehicle system 1 can be modeled as shown in FIG.
However, in FIG._e, Δ_e, Β_e, R_s, R_eAre variables (state quantities), and ω_eIs the estimated value of the motor angular velocity, δ_eIs the estimated value of the front wheel actual steering angle (steering angle), β_eIs the estimated value of the slip angle of the center of gravity of the vehicle, r_sIs the detected value of the yaw rate of the vehicle, r_eIs the estimated yaw rate of the vehicle, ω_eIs the estimated value of the motor angular velocity, w_eIs the estimated value of the disturbance torque (= the estimated driver torque T_heAnd estimated steering reaction torque T_ceAnd w,_e= T_he+ T_ce). Also, K_g, M, I, V, K_f, K_r, L_f, L_rAre all parameters (constant values) unique to the motor control system._gIs the steering gear ratio (ratio between the motor phase angle and the front wheel (steering wheel) steering angle), m is the mass of the vehicle, I is the moment of inertia of the vehicle, V is the vehicle speed, K_fIs front wheel cornering power, K_rIs the rear wheel cornering power, l_fIs the distance from the center of gravity to the front axle, l_rIs the distance from the center of gravity to the rear wheel axle. l_v1~ L_v3Is the observer constant.
[0027]
From such a model, the steering angle δ_eIs given by the following equation (6):_eIs given by the following equation (7):_sCan be established as in the following equation (8).
dδ_e/ Dt = ω_e/ K_g・ ・ ・ (6)
dβ_e/ Dt = (2K_f/ MV) δ_e− [MV²+2 (l_fK_f−l_rK_r) / MV²] R_e− [2 (K_f+ K_r) / MV] β_e・ ・ ・ (7)
dr_e/ Dt = (2l_fK_f/ I) δ_e− [2 (l_fK_f−l_rK_r) / I] β_e− [2 (l_f ²K_f+ L_r ²K_r) / IV] r_e・ ・ ・ (8)
Expressions (6) to (8) are expressed by the following equation (9).
[0028]
(Equation 4)

[0029]
Yaw rate detection value r based on equation (9)_sIs the observed value, and the estimated motor angular velocity ω_seThe following equation (10) shows the state equation of the observer when is the input value.
[0030]
(Equation 5)

[0031]
In the above state equation (10), δ_e, Β_e, R_eAre estimated values as the state quantities (the above-described estimated values of the front wheel actual steering angle, the estimated value of the center of gravity slip angle, and the estimated value of the yaw rate)._v1, L_v2, L_v3Are all coefficients. Where the coefficient l_v1, L_v2, L_v3, The state quantity δ_e, Β_e, R_eCan be configured. Also, the coefficient l_v1, L_v2, L_v3Can set an appropriate value by a mathematical operation in consideration of frequency characteristics.
[0032]
The calculation unit 31b calculates the driver torque estimated value T by calculation based on the estimation result obtained by the observer 31a._heAsk for.
That is, the sideslip angle β of the front tire_feAnd the steering reaction force (self-aligning torque), the side slip angle β of the front tire_feCan be calculated by the following equation (11).
β_fe= Β_e+ (L_f/ V) r_e−δ_e・ ・ ・ (11)
Front wheel tire sideslip angle β_feIs small, the steering reaction torque T around the kingpin axis is small._seCan be calculated by the following equation (12) (where ξ is a restoring moment trail).
T_se= 2ξK_fβ_fe・ ・ ・ (12)
Where ξ is the restoring moment trail.
[0033]
Here, the steering reaction torque T around the kingpin axis_seIs the steering reaction torque T about the column axis (steering axis)._ceWhen converted to the following equation (13) is obtained.
T_ce= (2ξK_f/ K_g) Β_fe・ ・ ・ (13)
Where K_gIs the steering gear ratio.
Therefore, the calculation unit 31b calculates the above-mentioned estimated value w_e, Β_e, R_e, Δ_eFrom the estimated driver torque T_heCan be calculated.
T_he= W_e-T_ce= W_e− (2ξK_f/ K_g) Β_fe
= W_e− (2ξK_f/ K_g) [Β_e+ (L_f/ V) r_e−δ_e] (14)
The control amount setting unit 32 calculates the motor current estimated value i thus estimated._e(This estimated value is the motor current detection value i_s), The estimated motor angular velocity ω_e, Driver torque estimated value T_he, Front wheel steering angle estimated value δ_e, The center-of-gravity slip angle estimated value β_eAnd the yaw rate estimate r_e(This estimate is the yaw rate detection value r_s) And the detection information from the vehicle speed detecting means (vehicle speed sensor) 42 are input, and each estimated value i_e, Ω_e, T_he, Δ_e, Β_e, R_eIs the speed-dependent gain K_i, K_ω, K_Th, K_δ, K_β, K_r, And these are added as in the following equation (15) to obtain a target voltage value v_tIs set.
v_t= -K_i・ I_e-K_ω・ Ω_e+ K_Th・ T_he-K_δ・ Δ_e-K_β・ Β_e-K_r・ R_e... (15)
Note that the speed corresponding gain K_i, K_ω, K_Th, K_δ, K_β, K_rAre set with characteristics as shown in FIG.
[0034]
Motor current control gain K_iAs shown in FIG. 4A, is set almost constant almost without depending on the vehicle speed._tValue K_i・ I_eIs reflected, the dynamic characteristics of the control are improved.
Motor angular velocity control gain K_ωIs set so as to increase as the vehicle speed increases, as shown in FIG._tValue K_ω・ Ω_eIs reflected, the occurrence of an excessive angular velocity at the time of sudden steering or the like is suppressed.
[0035]
Driver torque control gain K_ThIs set so as to decrease as the vehicle speed increases, as shown in FIG. 4C, and the target voltage value v increases as the vehicle speed increases._tAnd the steering assist torque T_mIs to be reduced. This is because the higher the vehicle speed, the lower the steering assist with an emphasis on the steering stability (feeling of maintaining the steering), and conversely, the lower the vehicle speed, the stronger the steering assist to facilitate the steering operation. Speed gain K_i, K_ω, K_ThOut of this driver torque control gain K_ThIs set to be the largest, and the driver torque control gain K_ThIs the target voltage value v_tHas the greatest effect.
[0036]
Front wheel steering angle control gain K_δAs shown in FIG. 4D, the value becomes a negative value at a low vehicle speed, increases as the vehicle speed increases (the value decreases in the case of a negative value), and increases at a high vehicle speed. It is set to be a positive value. However, at an extremely low speed, the value decreases as the vehicle speed increases (the value is a negative value, and the magnitude of the absolute value increases as the vehicle speed increases). Front wheel steering angle control gain K at low speed_δIs set to be negative in order to facilitate the steering operation by applying an assist torque in the same direction as the steering angle. As the speed increases, the front wheel steering angle control gain K_δIs set to be positive so that the higher the vehicle speed, the greater the importance of the steering stability, and the higher the steering feeling during high-speed running.
[0037]
Center of gravity slip angle control gain K_βIs set to increase as the vehicle speed increases, as shown in FIG. However, at an extremely low speed, the vehicle speed increases rapidly with an increase in the vehicle speed, and thereafter increases gradually. This is intended to maintain the stability of the vehicle from low speed to high speed and to improve the steering feeling.
Yaw rate control gain K_rAs shown in FIG. 4 (f), is set to 0 when the vehicle speed is low, and to increase as the vehicle speed increases when the vehicle speed is high and medium. This also aims at maintaining the stability of the vehicle from low speed to high speed and improving the steering feeling in the same manner as described above.
[0038]
Since the electric power steering apparatus according to the first embodiment of the present invention is configured as described above, the motor additional voltage v as the motor command value, the motor current i detected by the current sensor 21 and the yaw rate sensor 23 are used. The steering torque (driver torque) Th is estimated from the detected yaw rate r, and the estimated driver torque T_hBy controlling the additional voltage v of the motor 11 in accordance with_mTherefore, the steering assist can be appropriately performed according to the driver's steering load state only by adding calculation software without the need for a torque sensor. That is, the steering feeling can be improved at low cost.
[0039]
Also, the driver torque T_hIs set to decrease as the vehicle speed increases._ThAfter the processing is performed, the additional voltage v of the motor 11 is controlled, so that the lower the vehicle speed, the stronger the steering assist and the easier the steering operation, and the higher the vehicle speed, the weaker the steering assist and the more stable steering. Steering feeling) is increased, and steering assist can be appropriately performed according to the vehicle speed.
[0040]
In the present embodiment, the motor current i is controlled by the motor current control gain K to control the additional voltage v of the motor 11._iThus, the dynamic characteristics of the control can be improved, and steering assist control with good responsiveness can be realized.
In addition, since the motor angular velocity ω is processed and reflected by the motor angular velocity control gain Kω in the control of the additional voltage v of the motor 11, the occurrence of excessive angular velocity can be suppressed, and the motor can be protected. it can.
[0041]
Further, the front wheel steering angle δ is controlled by the front wheel steering angle control gain K to control the additional voltage v of the motor 11._δThus, the steering operation can be facilitated at low speeds while considering the ease of stationary steering, and the steering feeling during high-speed running can be improved.
In addition, the center of gravity slip angle β is used to control the additional voltage v of the motor 11,_βThe yaw rate r is applied to the control of the additional voltage v of the motor 11 and the yaw rate control gain K_rThe steering feeling at the time of high-speed running can be improved.
[0042]
If there is no particular problem in the dynamic characteristics of the control, it is not necessary to reflect the motor current i in the control of the additional voltage v of the motor 11. It is not necessary to reflect the motor angular velocity ω in controlling the voltage v.
If it is not necessary to finely adjust the steering feeling, a part of the front wheel steering angle δ, the center of gravity slip angle β, and the yaw rate r may be reflected in the control of the additional voltage v of the motor 11, or Control can be simplified by not reflecting the
[0043]
Next, a second embodiment of the present invention will be described. FIG. 5 is a block diagram showing a functional configuration of an electric power steering apparatus according to a second embodiment of the present invention.
In the present embodiment, as described in the first embodiment, the method of controlling the steering assist without using the torque sensor is used as a backup when the torque sensor fails in the electric power steering device with the torque sensor. .
[0044]
In other words, in the present embodiment, a torque sensor failure detection device is added to the conventional electric power steering device with a torque sensor, and appropriate software and hardware are added to the electric power steering control device. When the failure detection device detects the occurrence of the failure of the torque sensor, the driver is notified of the occurrence of the failure through the display device, and the steering assist is continued by applying the above-described method without using the torque sensor. ing.
[0045]
Specifically, as shown in FIG. 5, a steering torque sensor (steering torque detecting means) 51 for detecting a steering torque is provided, and an ECU 30 is provided with a steering torque sensor based on a detection signal of the actual steering torque from the steering torque sensor 51. A first control amount setting unit (setting means) 52 for setting the additional voltage v of the DC motor 2 in accordance with the actual steering torque is provided. When the steering torque sensor 51 is operating normally, the first control amount setting is performed. The additional voltage v set based on the actual steering torque by the section 52 is applied to the DC motor 2 so that steering assist is performed in accordance with the actual steering torque.
[0046]
Further, the control amount setting unit 32 of the above-described embodiment, that is, the control amount setting unit 32 that sets the additional voltage v of the DC motor 2 based on the estimation of the observer 31 is replaced by a second control amount setting unit for backup (setting unit). ) 32 '. Then, a steering torque sensor failure detecting means 53 for detecting a failure of the steering torque sensor 51 is provided, and if the failure of the steering torque sensor 51 is detected by the failure detecting means 53, the second control amount setting section 52 is replaced with the second control amount setting section 52. A control amount setting switching unit 54 is provided for switching the control amount setting unit 32 'to set the additional voltage v of the DC motor 2.
[0047]
Since the electric power steering apparatus according to the second embodiment of the present invention is configured as described above, even if the steering torque sensor 51 fails, the DC motor 2 is added by the second control amount setting unit 32 '. The voltage v can be set.
That is, even when the torque sensor fails, it is possible to avoid a situation in which the steering assist cannot be performed, and it is possible to always improve the steering feeling.
[0048]
As a countermeasure against the failure of the torque sensor, it is conceivable to separately provide a spare torque sensor. However, by applying the configuration of the present embodiment, the spare torque sensor becomes unnecessary.
Further, when the configuration of the present embodiment is applied to an electric power steering device having two torque sensors, when one of the torque sensors fails and the difference between the output values of the two torque sensors becomes equal to or more than a predetermined value. In addition, while comparing the estimated value of the driver torque with the output values of the two torque sensors, the steering assist is continued using the output of the torque sensor having the smaller difference from the estimated value of the driver torque, What is necessary is just to notify the sensor failure. In this case, since it is possible to know which sensor is out of order, it is also possible to notify the faulty torque sensor so that it can be distinguished. Further, when both of the two torque sensors fail, the steering assist control can be continued using the estimated value of the driver torque.
[0049]
Although the embodiments of the present invention have been described above, the present invention is not limited to such embodiments, and can be variously modified and implemented without departing from the spirit of the present invention.
For example, speed-dependent gain K_i, K_ω, K_Th, K_δ, K_β, K_γFIG. 4 shows an example of each setting,_i, K_ω, K_Th, K_δ, K_β, K_γIs not limited to this, and the speed-dependent gain K is set so that the stability of the system and the steering feeling can be improved._i, K_ω, K_Th, K_δ, K_β, K_γIt is important to set the value appropriately according to the vehicle speed.
[0050]
Further, in addition to the speed-dependent gain processing function, a phase lead compensator or a phase lag compensator may be added to the control amount setting unit 32 to adjust the phase, thereby performing more appropriate steering assist control. Conceivable.
[0051]
【The invention's effect】
As described in detail above, according to the electric power steering device of the present invention (claim 1), the steering assist can be appropriately performed according to the driver's steering addition state by simply adding the calculation software without requiring the torque sensor. And the steering feeling can be improved at low cost.
[0052]
Further, the estimating means uses the motor added voltage value to the DC motor, the motor current value detected by the current detecting means, and the yaw rate of the vehicle detected by the yaw rate detecting means to calculate the DC motor Based on the model of the steering-vehicle control system including the driver torque applied to the control system of the DC motor, the angular velocity of the DC motor, the steering angle of the steered wheels of the vehicle, and the slip angle of the center of gravity of the vehicle. And the setting means calculates the current value detected by the current detecting means, the yaw rate of the vehicle detected by the yaw rate detecting means, and each estimated value estimated by the estimating means. If the target motor additional voltage value to be given to the DC motor is set in accordance with the above, the dynamic characteristics of the control can be improved and the steering assist control with good response can be achieved. The or be realized by suppressing the occurrence of excessive angular velocities of the motor, it becomes possible to protect the motor and to possible to improve the fine-grained steering feeling (claim 2).
[0053]
The setting means determines a DC according to the current value detected by the current detecting means, the yaw rate of the vehicle detected by the yaw rate detecting means, each estimated value estimated by the estimating means, and the vehicle speed detected by the vehicle speed detecting means. By setting the target motor additional voltage value to be given to the motor, the steering assist can be precisely controlled in accordance with the vehicle speed.
[0054]
Further, according to the electric power steering apparatus of the present invention (claim 6), even when the torque sensor fails, it is possible to avoid a situation in which the steering assist becomes impossible, and it is possible to always improve the steering feeling.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a functional configuration of an electric power steering device according to a first embodiment of the present invention.
FIG. 2 is a block diagram of an observer for estimating a state quantity of a motor control system according to the electric power steering device as the first embodiment of the present invention.
FIG. 3 is a block diagram of an observer for estimating a state quantity of a steering-vehicle system according to the electric power steering apparatus as the first embodiment of the present invention.
4A and 4B are diagrams showing characteristics of a speed-related control gain used for control in the electric power steering device according to the first embodiment of the present invention, wherein FIG. 4A shows a control gain related to a motor current, and FIG. (C) shows a control gain for a driver torque, (d) shows a control gain for a front wheel steering angle, (e) shows a control gain for a center-of-gravity slip angle, and (f) shows a control gain for a center-of-gravity slip angle. 6 shows a control gain related to yaw rate.
FIG. 5 is a block diagram illustrating a functional configuration of an electric power steering device according to a second embodiment of the present invention.
[Explanation of symbols]
1 Steering-vehicle system
11 DC motor
21 ° current detection means
22 Vehicle speed detection means
23 ° yaw rate detection means
Electronic control unit (ECU) as 30 ° control means
31 Estimation means
31a @ Observer
31b Driver torque calculator
Control amount setting unit as 32 ° setting means
32 ′ second control amount setting unit (setting means)
41 Motor torque calculator
51 ° steering torque sensor (steering torque detecting means)
52 first control amount setting unit (setting means)
53 ° steering torque sensor failure detecting means

Claims (6)

An electric power steering device mounted on a vehicle and assisting steering using a DC motor,
Current detection means for detecting a current flowing through the DC motor;
Yaw rate detection means for detecting the yaw rate of the vehicle,
Control means for controlling an additional voltage to the DC motor by feedback-controlling a motor additional voltage value to the DC motor;
The control means includes:
Using a motor additional voltage value to the DC motor, a motor current value detected by the current detecting means, and a yaw rate of the vehicle detected by the yaw rate detecting means, a steering-vehicle system including the DC motor is used. Estimating means for estimating at least a driver torque applied to the control system of the DC motor based on a model of the control system;
Setting means for setting a target motor additional voltage value to be applied to the DC motor according to the driver torque estimated by the estimating means,
An electric power steering apparatus, wherein the target motor additional voltage value set by the setting means is applied to the DC motor. The estimating unit includes the DC motor using a motor additional voltage value to the DC motor, a motor current value detected by the current detecting unit, and a yaw rate of the vehicle detected by the yaw rate detecting unit. Based on the model of the steering-vehicle control system, in addition to the driver torque applied to the DC motor control system, the angular velocity of the DC motor, the steering angle of the steered wheels of the vehicle, and the slip angle of the center of gravity of the vehicle Estimate at least one of them,
The setting means should supply the current to the DC motor in accordance with the current value detected by the current detection means, the yaw rate of the vehicle detected by the yaw rate detection means, and the estimated values estimated by the estimation means. The electric power steering apparatus according to claim 1, wherein a target motor additional voltage value is set. The estimating means calculates the motor current value as a state quantity, the angular velocity of the DC motor, the disturbance torque, the steering wheel of the vehicle from the motor additional voltage value, the motor current value as the state quantity, and the yaw rate of the vehicle. An observer for estimating at least one of a steering angle of the vehicle, a slip angle of the center of gravity of the vehicle, and a yaw rate of the vehicle;
3. The electric power steering apparatus according to claim 2, further comprising: a driver torque calculator that calculates the driver torque based on the estimated amount estimated by the observer. A vehicle speed detecting means for detecting a vehicle speed of the vehicle;
The setting means includes: a current value detected by the current detection means; a yaw rate of the vehicle detected by the yaw rate detection means; each estimated value estimated by the estimation means; and a vehicle speed detected by the vehicle speed detection means. 4. The electric power steering apparatus according to claim 2, wherein the target motor additional voltage value to be applied to the DC motor is set according to the following. The setting means calculates a sum of values obtained by multiplying the current value, the yaw rate, and the respective estimated values estimated by the estimating means with respective control gains set in accordance with the vehicle speed. The electric power steering apparatus according to claim 4, wherein the value is set to an additional voltage value. An electric power steering device comprising a steering torque sensor mounted on a vehicle and detecting a steering torque applied to a steering system, and assisting steering using a DC motor based on the steering torque detected by the steering torque sensor,
Steering torque sensor failure detecting means for detecting a failure of the steering torque sensor;
Current detection means for detecting a current flowing through the DC motor;
Control means for controlling an additional voltage to the DC motor;
The control means includes:
When the steering torque sensor failure detecting means detects a failure of the steering torque sensor, the motor additional voltage value to the DC motor, the motor current value detected by the current detecting means, and the motor current value detected by the yaw rate detecting means are detected. Estimating means for estimating at least a disturbance torque applied to a control system of the DC motor based on a model of a control system of a steering-vehicle system including the DC motor using the yaw rate of the vehicle.
Setting means for setting a target motor additional voltage value to be applied to the DC motor in accordance with the disturbance torque estimated by the estimating means,
An electric power steering apparatus, wherein the target motor additional voltage value set by the setting means is applied to the DC motor.

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