JP3775127B2 - Vehicle motion control device - Google Patents

Description

なお、各記号について説明すると、ｄψ：ヨーレート、Ｖｙ：横方向速度、Ｖ：車速、Ｍ：車両質量、Ｉｚ：ヨー慣性モーメント、Ｌ_Ｆ：前軸と重心間距離、Ｌ_Ｒ：後軸と重心間距離、ｅＫ_Ｆ：前輪等価コーナリングパワー、Ｋ_Ｒ：後輪コーナリングパワー、Ｃ_Ｆ：前輪コーナリングフォース、Ｃ_Ｒ：後輪コーナリングフォース、θ_Ｓ：操舵角、δ_Ｒ：後輪舵角、Ｎ：ステアリングギア比である。
【００６７】
ヨーレートｄψを出力として選ぶと、出力方程式は、次式（７）となる。
ｙ＝ＣＸ＝［１ ０］Ｘ＝ｄψ ・・・（７）
式（６）（７）をラプラス変換すると、
Ｘ（ｓ）＝（ｓＩ-Ａ）^{- １}ＢＵ（ｓ） ・・・（８）
Ｙ（ｓ）＝ＣＸ（ｓ） ・・・（９）
操舵角入力に対するヨーレート出力の伝達関数は次式（１０）となる。なお、これは請求項４記載の発明に対応している部分である。
Ｇ（ｓ）＝Ｃ（ｓＩ-Ａ）^{- １}Ｂ
＝（ｂ_１１ｓ-ａ_２２ｂ_１１+ａ_１２ｂ_２１）／
｛ｓ^２-（ａ_１１+ａ_２２）+ａ_１１ａ_２２-ａ_１２ａ_２１｝ ・・・（１０）
操舵角フィルタを考えるとき、入力に対して出力は定常状態では等しくなる必要がある。すなわち、ゲインは１ということになる。上記式（１０）は操舵角入力に対するヨーレート出力を表しているため、ゲインは１ではない。そこで、上記式（１０）を変形して定常ゲイン部分とゲイン１のフィルタ部分に分けて下記式（１１）に表現する。なお、これは請求項６に記載の発明に対応している部分である。
【００６８】
【式２】

また、むだ時間は、操舵角のフィルタ処理のみでは調整できない遅れを表現するために用いる。この遅れは、主に２自由度の車両モデルで表現できないタイヤ特性に起因するものである。本実施の形態では、むだ時間を車速に応じて大きくなるように設定した。車速によるむだ時間の変化を図４に示す。なお、これは請求項７ないし９に記載の発明に対応している部分である。
【００６９】
本実施の形態のヨーレートゲイン推定検出部５０１を図５に示すフローチャートに基づき説明する。
まず、ｓｔｅｐ１で操舵角入力値ＳＴＲ＿ｉｎの絶対値が２０°未満かどうかをチェックする。２０°未満の場合はｓｔｅｐ４へ進む。ＳＴＲ＿ｉｎが２０°以上の場合はｓｔｅｐ２で、まず、式（１２）のフィルタ演算を行い、さらに、車速に応じて設定されたむだ時間処理を行い、ＳＴＲ＿ｏｕｔを算出する。次にｓｔｅｐ３で式（１）の演算を行い、ヨーレートゲイン推定値ＹＧ＿ＥＳＴＩを算出する。ｓｔｅｐ４では、ヨーレートゲイン推定値ＹＧ＿ＥＳＴＩを目標ヨーレートゲインＲｅｆ＿ＹＧとする。
【００７０】
式（１２）のフィルタおよびむだ時間処理により算出した操舵角を用いて、ヨーレートゲインを推定したようすを図６に示す。図示のように、操舵速度などに影響を受けずに、精度良くヨーレートゲインを推定することが可能である。
【００７１】
次に、目標ヨーレートゲイン設定部５０２について説明する。目標ヨーレートゲイン設定部５０２では、走行状態に応じて目標となるヨーレートゲインを設定する。
【００７２】
本実施の形態では、図７に示すように、車両のスタビリティファクタが常に一定となるように、目標ヨーレートゲインＲｅｆ＿ＹＧを設定した。本実施の形態の他にも、横方向加速度に応じて目標ヨーレートゲインＲｅｆ＿ＹＧを変化させる方法や、後輪操舵システムにおいて、定常状態での後輪操舵量を決めるパラメータである定常ヨーレートゲインを目標ヨーレートゲインＲｅｆ＿ＹＧとする方法も考えられる。
【００７３】
次に、ブレーキ力配分制御部５０３について説明する。このブレーキ力配分制御部５０３は、請求項１０ないし１２に記載の発明に対応する制御を実行する部分であって、目標ヨーレートゲインＲｅｆ＿ＹＧとヨーレートゲイン推定値ＹＧ＿ＥＳＴＩの偏差に応じてブレーキ力の配分を行う。以下に、本実施の形態における、前後配分と左右配分の組み合わせによるブレーキ力配分制御について説明する。
【００７４】
アンダステア傾向、オーバステア傾向が小さい（目標ヨーレートゲインＲｅｆ＿ＹＧとヨーレートゲイン推定値ＹＧ＿ＥＳＴＩの偏差の絶対値が小さい）場合は、前後のブレーキ力配分を行い、一方、アンダステア傾向、オーバステア傾向がおおきい（目標ヨーレートゲインＲｅｆ＿ＹＧとヨーレートゲイン推定値ＹＧ＿ＥＳＴＩの偏差の絶対値が大きい）場合は、左右のブレーキ力配分を行う。
【００７５】
また、操舵角が±２０°以内の場合は、前述したように、ヨーレートゲイン推定値＝目標ヨーレートゲインとするため、ブレーキ力指令値の演算は行わず、これまでのブレーキ力指令値を保持する。ただし、別に設定した目標ヨーレートと実際のヨーレートとの偏差が所定値以内になった場合には、ブレーキ制御を終了する。
【００７６】
本実施の形態のブレーキ力配分制御部５０４を、図８に示すフローチャートに基づき説明する。
【００７７】
まず、ｓｔｅｐ１１で操舵角ＳＴＲの大きさをチェックする。操舵角ＳＴＲが±２０°以上の場合はｓｔｅｐ２１へ、その他の場合はｓｔｅｐ１１１へ進む。
ブレーキ力は、ＰＩ制御により決定する。ｓｔｅｐ２１で目標ヨーレートゲインＲｅｆ＿ＹＧとヨーレートゲイン推定値ＹＧ＿ＥＳＴＩの偏差の積分値ＥｒｒＩと偏差量ＥｒｒＰにそれぞれゲインＢｒｋＩ、ＢｒｋＰを掛けてブレーキ力指令値Ｂｒｋｃｏｍを算出する。
Ｂｒｋｃｏｍ＝ＥｒｒＩ×ＢｒｋＩ+ＥｒｒＰ×ＢｒｋＰ ・・・（１３）
次に、ｓｔｅｐ４１で、ブレーキ力指令値Ｂｒｋｃｏｍの大きさをチェックする。ＯＳ１≦Ｂｒｋｃｏｍ≦ＵＳ１の場合は、実際のヨーレートゲインが目標ヨーレートゲインに近い状態なので、ブレーキ配分制御を行わない。
【００７８】
Ｂｒｋｃｏｍ＞ＵＳ１の場合は、ｓｔｅｐ５１に進む。これは実際のヨーレートゲインが、目標ヨーレートゲインよりも小さい状態、または小さい状態が続いた場合（アンダステア傾向）である。Ｂｒｋｃｏｍ＜ＯＳ１の場合は、ｓｔｅｐ８１へ進む。これは、実際のヨーレートゲインが目標ヨーレートゲインよりも大きい状態、または大きい状態が続いた場合（オーバステア傾向）である。ｓｔｅｐ５１では、アンダステア傾向が大きいかどうかの判断を行う。Ｂｒｋｃｏｍ≦ＵＳ２の場合は、アンダステア傾向が小さいと判断して、ｓｔｅｐ６１で後輪にブレーキをかけるようにブレーキ圧制御部５０４へ指令値を出力する。後輪にブレーキをかけることにより後輪のコーナリングフォースを減少させ、相対的に前輪のコーナリングフォースが大きくなるようにして、アンダステアを抑える。
【００７９】
ｓｔｅｐ５１で、Ｂｒｋｃｏｍ＞ＵＳ２の場合は、アンダステア傾向が大きいと判断して、ｓｔｅｐ７１で、旋回内輪にブレーキをかけるようにブレーキ圧制御部５０４へ指令値を出力する。旋回内輪にブレーキをかけることにより内向きのモーメントを発生させてアンダステアを抑える。
【００８０】
ｓｔｅｐ８１では、オーバステア傾向が大きいかどうかの判断を行う。Ｂｒｋｃｏｍ≧ＯＳ２の場合は、オーバステア傾向が小さいと判断して、ｓｔｅｐ９１で前輪にブレーキをかけるようにブレーキ圧制御部５０４へ指令値を出力する。前輪にブレーキをかけることにより前輪のコーナリングフォースを減少させ、相対的に後輪のコーナリングフォースが大きくなるようにして、オーバステアを抑える。ｓｔｅｐ８１で、Ｂｒｋｃｏｍ＜ＯＳ２の場合は、オーバステア傾向が大きいと判断して、ｓｔｅｐ１０１で旋回外輪にブレーキをかけるようにブレーキ圧制御部５０４へ指令値を出力する。旋回外輪にブレーキをかけることにより外向きのモーメントを発生させてオーバステアを抑える。
【００８１】
ｓｔｅｐ１１で、操舵角ＳＴＲが±２０°未満の場合は、ｓｔｅｐ１１１で、目標ヨーレートＲｅｆ＿Ｙａｗと実際のヨーレートｙａｗｒａｔｅの偏差Ｅｒｒ＿Ｙａｗの算出を行う。
【００８２】
Ｅｒｒ＿Ｙａｗ＝｜Ｒｅｆ＿Ｙａｗ-ｙａｗｒａｔｅ｜ ・・・（１４）
本実施の形態では、目標ヨーレートは式（１０）を基に次式で算出する。
Ｒｅｆ＿Ｙａｗ＝［（ｂ_１１ｓ-ａ_２２ｂ_１１+ａ_１２ｂ_２１）／｛ｓ^２-（ａ_１１+ａ_２２）ｓ+ａ_１１ａ_２２-ａ_１２ａ_２１｝］θ_ｓ ・・・（１５）
次に、ｓｔｅｐ１２１でヨーレート偏差Ｅｒｒ＿Ｙａｗの大きさをチェックする。この偏差Ｅｒｒ＿Ｙａｗが所定値ＥＳ１よりも小さい場合には、ブレーキ制御は終了となる。また、前記偏差Ｅｒｒ＿Ｙａｗが所定値ＥＳ１よりも大きい場合は、ｓｔｅｐ４１へ進み、ブレーキ力指令値Ｂｒｋｃｏｍの大きさをチェックする。すなわち、操舵角ＳＴＲが±２０°未満の場合は、ｓｔｅｐ２１からｓｔｅｐ３１のブレーキ力指令値算出を行わず、これまでのブレーキ力指令値を用いて各輪にブレーキをかける。ただし、ヨーレート偏差Ｅｒｒ＿Ｙａｗが所定値ＥＳ１よりも小さくなるとブレーキ制御を終了する。
【００８３】
アンダステア傾向あるいはオーバステア傾向が比較的小さい場合は、車両挙動変化が穏やかなブレーキの前後配分制御を行い、一方、アンダステア傾向あるいはオーバステア傾向が大きい場合は、車両を安定方向に動かす効果の大きいブレーキの左右配分制御を行う。前後配分制御から左右配分制御の切り換えは、急に行わずに徐々に行うことで、車両挙動の乱れを防ぐことができる。
【００８４】
本実施の形態では、前後、左右の配分を行うものであるが、車両の状態に応じて前輪内輪、後輪外輪など、各輪のブレーキ圧を制御することにより、さらに滑らかで効果の大きい制御を行うことが可能である。
【図面の簡単な説明】
【図１】実施の形態の車両運動制御装置を示す全体システム図である。
【図２】実施の形態の車両運動制御装置を示す制御ブロック図である。
【図３】実施の形態の２次のローパスフィルタを用いたヨーレートゲイン推定の様子を示すタイムチャートである。
【図４】実施の形態の操舵角に施すむだ時間の設定方法の一例を示すむだ時間特性図である。
【図５】実施の形態のヨーレートゲイン推定検出部における制御流れを示すフローチャートである。
【図６】実施の形態の車両モデルフィルタとむだ時間を用いたヨーレートゲイン推定の様子を示すタイムチャートである。
【図７】実施の形態の目標ヨーレートゲインの設定方法の一例を示す目標ヨーレートゲイン特性図である。
【図８】実施の形態のブレーキ力配分制御部における制御流れを示すフローチャートである。
【符号の説明】
１ 操舵角センサ
２ 車速センサ
３ ヨーレートセンサ
４ ブレーキアクチュエータ
５ 車両運動制御コントローラ
５０１ ヨーレートゲイン推定検出部
５０２ 目標ヨーレートゲイン設定部
５０３ ブレーキ力配分制御部
５０４ ブレーキ圧制御部[0001]
BACKGROUND OF THE INVENTION
The present invention belongs to the technical field of a vehicle motion control device that estimates and detects a yaw rate gain of a vehicle and distributes a braking force so that the detected value matches a target yaw rate gain.
[0002]
[Prior art]
Conventionally, as a vehicle motion control device, a method for controlling the steering angles of front and rear wheels so that an actual yaw rate (estimated yaw rate) matches a target yaw rate is proposed as disclosed in, for example, Japanese Patent Laid-Open No. 5-105101. Has been.
[0003]
[Problems to be solved by the invention]
However, the conventional vehicle motion control device is a method of controlling the steering angle of the front and rear wheels so that the yaw rate generated in the vehicle matches the target yaw rate characteristic even in the turning limit travel region where the lateral acceleration is large. For,
(1) Since the target yaw rate is set regardless of the driver's steering amount, there is a risk that the driver may feel uncomfortable.
[0004]
(2) In the turning limit travel region, the effect of reducing the understeer tendency by increasing the steering angle is small.
[0005]
There are problems such as.
[0006]
Accordingly, the present inventor has proposed a vehicle motion control device described in the specification of Japanese Patent Application No. 10-266542 in order to solve the above-described problems. In this prior art, the yaw rate gain is estimated and detected by identifying each parameter of the yaw rate output transfer characteristic with respect to the steering input by using the least square method. As a result, it is possible to obtain a desired yaw rate output with respect to the driver's steering input even in the turning limit travel region without a sense of incongruity in steering.
[0007]
Thus, the above-mentioned prior art can obtain an excellent effect. However, in this prior art, since the yaw rate gain estimation calculation is complicated, when considering an in-vehicle system, it is necessary to improve the performance of the in-vehicle calculation microcomputer as compared with a normal one. Therefore, it has been desired to reduce the cost of the system by simplifying the calculation.
[0008]
  The present invention has been made by paying attention to such conventional problems. Basically, the yaw rate / steering angle is the yaw rate gain,Adjusting the delay from the yaw rate to the detected steering angleAn object of the present invention is to solve the above-mentioned problems by simplifying the calculation while performing filter processing to ensure estimation accuracy.
[0009]
[Means for Solving the Problems]
  In order to achieve the above object, the invention described in claim 1 is a vehicle speed detecting means for detecting the speed of the vehicle, a yaw rate detecting means for detecting the yaw rate of the vehicle, and a steering angle detecting means for detecting the steering angle. A yaw rate gain estimation detecting means for estimating and detecting a yaw rate gain of the vehicle based on the vehicle speed detection value, the yaw rate detection value, and the steering angle detection value; a target yaw rate gain setting means for setting a target value of the yaw rate gain;Estimated yaw rate gainAnd a brake force distribution unit that calculates a brake force command value of each wheel so as to eliminate a deviation between the target yaw rate gain and a brake pressure control unit that controls a brake pressure of each wheel according to the brake force command value; The yaw rate gain estimation detecting means has the steering angle detection value as aAdjusting the delay from the yaw rateSteering angle filter processing calculation means for performing filter processing, and using the yaw rate detection value as a dividend while dividing the steering angle filter processing calculation output value as a divisorEstimated yaw rate gainIt is characterized by.
[0010]
Note that, as in the invention described in claim 2, in the vehicle motion control device according to claim 1, the yaw rate gain estimation detection means is configured to perform the steering only when the absolute value of the steering angle detection value is a predetermined value or more. An angular filter processing calculation is performed to calculate a yaw rate gain estimated value by the division. When the absolute value of the detected steering angle is less than a predetermined value, the yaw rate gain estimated value is set as the target yaw rate gain set value. Is preferred.
[0011]
According to a third aspect of the present invention, in the vehicle motion control apparatus according to the first or second aspect, the steering angle filter processing calculation means is configured to change the filter characteristics according to the vehicle speed. Is preferred.
[0012]
Alternatively, as in a fourth aspect of the present invention, in the vehicle motion control apparatus according to the first or second aspect, the steering angle filter processing calculation means configures a filter using a transfer characteristic of a yaw rate with respect to a steering input. Also good.
[0013]
Alternatively, as in a fifth aspect of the invention, in the vehicle motion control apparatus according to the first or second aspect, the steering angle filter processing calculation means performs a filter using a two-degree-of-freedom vehicle model in yawing and lateral directions. It may be configured.
[0014]
According to a sixth aspect of the present invention, in the vehicle motion control apparatus according to the first or second aspect, the steering angle filter processing calculation means deforms the two-degree-of-freedom vehicle model in a yawing and lateral direction to make a steady state. A gain portion and a gain 1 filter portion may be divided and a gain 1 filter portion may be applied to the steering angle detection value.
[0015]
According to a seventh aspect of the present invention, in the vehicle motion control device according to the first to sixth aspects, the steering angle filter processing calculation means performs a filtering process and a dead time process on the steering angle detection value. Is preferred.
[0016]
Furthermore, as in the invention described in claim 8, in the vehicle motion control apparatus described in claim 7, it is preferable that the steering angle filter processing calculation unit changes the dead time according to the detected vehicle speed.
[0017]
According to a ninth aspect of the present invention, in the vehicle motion control apparatus according to the eighth aspect, the steering angle filter processing calculation means preferably sets the dead time to be longer as the detected vehicle speed value is larger. .
[0018]
  According to a tenth aspect of the present invention, in the vehicle motion control device according to the first to ninth aspects, the brake force distribution means includes theEstimated yaw rate gainIt is preferable that the balance of the cornering force of the front and rear wheels is controlled by front and rear brake distribution so as to eliminate the deviation between the target yaw rate gain and the target yaw rate gain.
[0019]
  Alternatively, as in the invention described in claim 11, in the vehicle motion control device according to claims 1 to 9, the brake force distribution unit includes the brake force distribution unit.Estimated yaw rate gainPreferably, the difference between the left and right braking force is controlled by the left and right braking force distribution so as to eliminate the deviation between the left and right target yaw rate gains.
[0020]
  Further, as described in claim 12, in the vehicle motion control device according to claims 1 to 9, the brake force distribution means includesEstimated yaw rate gainPreferably, the front and rear brake force distribution is performed when the deviation between the target yaw rate gain and the target yaw rate gain is small, and the left and right brake force distribution is performed when the deviation is large.
[0021]
Operation and effect of the invention
  In the invention according to claim 1, the yaw rate gain is estimated and detected,Estimated yaw rate gainThe brake force distribution of each wheel is controlled so as to eliminate the deviation between the target yaw rate gain and the target yaw rate gain. The estimated detection of the yaw rate gain is performed on the detected steering angle value.Adjusting the delay from the yaw rateA value obtained by dividing the yaw rate detection value by the steering angle filter processing calculation output value is obtained by performing the filter processing to obtain the steering angle filter processing calculation output value.Estimated yaw rate gainIt is said.
[0022]
Therefore, the yaw rate gain can be estimated and calculated more easily without using a microcomputer with high calculation capability,Adjusting the delay from the yaw rate to the detected steering angleFilteringApplyingAs a result, it is possible to obtain an effect that the estimation calculation accuracy of the yaw rate gain can be secured.
[0023]
In the invention according to claim 2, the yaw rate gain estimation detection means calculates the yaw rate gain estimation value by the above division only when the absolute value of the steering angle detection value is not less than a predetermined value. When the absolute value of the detected steering angle is less than the predetermined value, the yaw rate gain estimated value is set as the target yaw rate gain setting value.
[0024]
Therefore, the estimation detection accuracy of the yaw rate gain can be improved by not performing the yaw rate gain estimation calculation in a region where the steering angle is small where the calculation accuracy deteriorates.
[0025]
In the invention according to claim 3, the filter characteristic is changed according to the vehicle speed in the steering angle filter processing calculation means.
[0026]
Therefore, a delay due to tire characteristics or the like occurs depending on the vehicle speed. By obtaining a steering angle filter processing calculation output value in consideration of this delay, it is possible to improve the estimation and detection accuracy of the yaw rate gain.
[0027]
In the invention according to claim 4, in the steering angle filter processing calculation means, the steering angle filter processing calculation is performed by the filter configured using the transfer characteristic of the yaw rate with respect to the steering input.
[0028]
Therefore, a yaw rate delay occurs with respect to the steering angle. By obtaining a steering angle filter processing calculation output value in consideration of this delay, it is possible to improve the estimation detection accuracy of the yaw rate gain.
[0029]
In the fifth aspect of the invention, the steering angle filter processing calculation means performs the steering angle filter processing calculation using a filter configured using a two-degree-of-freedom vehicle model in yawing and lateral directions.
[0030]
Therefore, by obtaining a steering angle filter processing calculation output value in consideration of the yawing and lateral dynamic characteristics of the vehicle by the two-degree-of-freedom vehicle model, it is possible to improve the estimation detection accuracy of the yaw rate gain.
[0031]
In the invention according to claim 6, in the steering angle filter processing calculation means, the two-degree-of-freedom vehicle model in the yawing and lateral directions is deformed and divided into a steady gain portion and a gain 1 filter portion, and a gain 1 filter portion. Steering angle filter processing calculation is performed by a filter configured to apply to the detected steering angle value.
[0032]
Therefore, filter processing is necessary in a transient state where the relationship between the input and output is not steady. By obtaining a steering angle filter processing calculation output value that takes into account the necessity of this filter processing, it is possible to detect and estimate yaw rate gain. The accuracy can be improved.
[0033]
According to the seventh aspect of the present invention, the steering angle filter processing calculation means subjects the detected steering angle value to filter processing and dead time processing.
[0034]
Therefore, a delay that cannot be expressed by the vehicle model and that cannot be adjusted only by the steering angle filter processing is expressed by a dead time, so that a steering angle filter processing calculation output value that eliminates the influence of the steering speed or the like can be obtained. Thus, it is possible to improve the estimation detection accuracy of the yaw rate gain.
[0035]
In the invention according to claim 8, the dead time is changed in accordance with the detected vehicle speed in the steering angle filter processing calculation means.
[0036]
Therefore, although the dead time changes according to the vehicle speed, the estimation detection accuracy of the yaw rate gain can be improved by obtaining the steering angle filter processing calculation output value in consideration of this dead time change.
[0037]
In the invention according to claim 9, in the steering angle filter processing calculation means, the dead time is set longer as the vehicle speed detection value is larger.
[0038]
Therefore, although the dead time becomes longer as the vehicle speed becomes higher, it is possible to improve the estimation detection accuracy of the yaw rate gain by obtaining the steering angle filter processing calculation output value that accurately captures the change in the dead time. it can.
[0039]
  In the invention according to claim 10, in the brake force distribution means,Estimated yaw rate gainThe balance of the cornering force of the front and rear wheels is controlled by the front and rear brake distribution so as to eliminate the deviation between the target yaw rate gain and the target yaw rate gain.
[0040]
Therefore, because the control is based on the front and rear brake distribution, which has a smaller control gain than the left and right brake distribution, a relatively small vehicle moment is generated even if the front and rear brake distribution ratio is increased, which is higher than a slight operation correction. It is possible to perform vehicle motion control that meets the correction request with accuracy.
[0041]
  In invention of Claim 11, in a braking force distribution means,Estimated yaw rate gainThe left and right braking force difference is controlled by the left and right braking force distribution so as to eliminate the deviation between the left and right target yaw rate gains.
[0042]
Therefore, since the control is based on the left and right brake distribution with a large control gain, a relatively large vehicle moment is generated even if the left and right brake distribution ratio is reduced. Can be controlled.
[0043]
  In the invention according to claim 12, in the brake force distribution means,Estimated yaw rate gainWhen the deviation between the target yaw rate gain and the target yaw rate gain is small, the front and rear brake force distribution is performed. When the deviation is large, the left and right brake force distribution is performed.
[0044]
Therefore, it is possible to achieve both high-precision motion control that responds to a slight motion correction request with a small deviation and high-response motion control that responds to a motion correction request with a large deviation.
[0045]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
First, the configuration will be described.
[0046]
FIG. 1 is an overall system diagram showing the vehicle motion control device of the first embodiment, and FIG. 2 is a control block diagram showing the vehicle motion control device of the first embodiment.
[0047]
In FIG. 1, 1 is a steering angle sensor (steering angle detection means), 2 is a vehicle speed sensor (vehicle speed detection means), 3 is a yaw rate sensor (yaw rate detection means), 4 is a brake actuator, and 5 is a vehicle motion control controller.
[0048]
In FIG. 2, reference numeral 501 denotes a yaw rate gain estimation detection unit (yaw rate gain estimation detection unit), 502 denotes a target yaw rate gain setting unit (target yaw rate gain setting unit), 503 denotes a brake force distribution control unit (brake force distribution unit), Reference numeral 504 denotes a brake pressure control unit (brake pressure control means).
[0049]
The steering angle sensor 1 detects the steering angle, the vehicle speed sensor 2 detects the vehicle speed, which is the ground speed of the vehicle, and the yaw rate sensor 3 detects the yaw rate of the vehicle.
[0050]
The brake actuator 4 applies a brake pressure independently to each wheel in accordance with a brake actuator control signal from the vehicle motion controller 5.
[0051]
The vehicle motion control controller 5 is an electronic control unit that uses sensor signals from the sensors 1, 2, 3 as input information and outputs a brake actuator control signal obtained as a result of calculation processing to the brake actuator 4.
[0052]
The yaw rate gain estimation detection unit 501 estimates and detects the vehicle yaw rate gain based on the vehicle speed detection value from the vehicle speed sensor 2, the yaw rate detection value from the yaw rate sensor 3, and the steering angle detection value from the steering angle sensor 1.
[0053]
The target yaw rate gain setting unit 502 sets a target yaw rate gain according to the vehicle speed detection value from the vehicle speed sensor 2.
[0054]
  The brake force distribution control unit 503Estimated yaw rate gainAnd the target yaw rate gain, the brake force command value for each wheel is calculated so as to eliminate the deviation.
[0055]
The brake pressure control unit 504 outputs an actuator control signal to the brake actuator 4 so that the actual brake pressure matches the brake pressure command value.
[0056]
Next, the operation will be described.
[0057]
[About yaw rate gain estimation detection]
A detection method in the yaw rate gain estimation detection unit 501 will be described.
[0058]
The basic idea is
Estimated yaw rate gain = Yaw rate / steering angle (1)
And However, since the calculation accuracy deteriorates when the steering angle is near zero, in the present embodiment, when the steering angle is within ± 20 °, the above calculation is not performed.
Estimated yaw rate gain = target yaw rate gain
And Therefore, the control of the braking pressure based on the deviation between the target value of the yaw rate gain and the estimated value (actual value) is not performed. This corresponds to the invention described in claim 2.
[0059]
The yaw rate in the above equation (1) is obtained by performing low-pass filter processing on the yaw rate sensor value to remove noise. Since the sensor value is a pulse output, the steering angle is not filtered for the purpose of noise removal. Since the yaw rate generated with respect to the steering angle is delayed, the correct yaw rate gain cannot be calculated if the calculation of equation (1) is performed as it is. Therefore, the delay with respect to the yaw rate is adjusted by applying a filtering process to the steering angle.
[0060]
FIG. 3 shows the yaw rate gain calculation when the steering angle filter is a secondary low-pass filter. As shown in FIG. 5B, depending on the steering speed or the like, the accuracy of the yaw rate gain estimated value may deteriorate in a region where the steering angle is small. This is because there is a difference between the steering angle filtering value and the yaw rate value.
[0061]
In the present embodiment, the yaw rate gain is estimated with higher accuracy by applying the filtering process using the vehicle model and the dead time process to the steering angle (corresponding to the invention of claim 7). Hereinafter, a filter using a vehicle model will be described.
[0062]
The yaw rate output transmission characteristic with respect to the steering input is assumed to be a primary / secondary form using a two-degree-of-freedom vehicle model with yawing and lateral direction. This corresponds to the invention described in claim 5.
[0063]
If the dynamic characteristics of the steering mechanism of the front wheels, the rolling motion, and the dynamic characteristics of the tire are ignored, the plane motion including the yawing and the lateral direction of the vehicle can be expressed linearly as the following equations (2) and (3).
[0064]
I_Zddψ = 2L_FC_F-2L_RC_R    ... (2)
MdV_y= -MVψ + 2C_F+ 2C_R       ... (3)
However,
C_F= EK_F{Θ_S/ N- (V_y+ L_Fdψ) / V}
C_R= K_R{-(V_y-L_Rdψ) / V}
It is. In the above equation, dψ is the first derivative of ψ, ddψ is the second derivative of ψ, dV_yIs V_yThe first derivative of is shown.
[0065]
The plane motion state vector of the car is x (t) and the input is the steering angle θ_S(T) is defined as the following equation (4).
[0066]
x^T= [DψV_y] (4)
u = θ_S      ... (5)
At this time, the equations (2) and (3) can be expressed by the following equation of state.
[Formula 1]

Each symbol will be described. Dψ: Yaw rate, Vy: Lateral speed, V: Vehicle speed, M: Vehicle mass, Iz: Yaw inertia moment, L_F: Distance between front axis and center of gravity, L_R: Distance between rear axis and center of gravity, eK_F: Front wheel equivalent cornering power, K_R: Rear wheel cornering power, C_F: Front wheel cornering force, C_R: Rear wheel cornering force, θ_S: Steering angle, δ_R: Rear wheel rudder angle, N: Steering gear ratio.
[0067]
When the yaw rate dψ is selected as an output, the output equation is expressed by the following equation (7).
y = CX = [1 0] X = dψ (7)
When the Laplace transform is performed on the equations (6) and (7),
X (s) = (sI-A)^{- 1}BU (s) (8)
Y (s) = CX (s) (9)
The transfer function of the yaw rate output with respect to the steering angle input is expressed by the following equation (10). This is a part corresponding to the invention of claim 4.
G (s) = C (sI-A)^{- 1}B
= (B₁₁sa₂₂b₁₁+ a₁₂b₂₁) /
{S²-(A₁₁+ a₂₂) + A₁₁a₂₂-a₁₂a₂₁} (10)
When considering a steering angle filter, the output needs to be equal in the steady state to the input. That is, the gain is 1. Since the above equation (10) represents the yaw rate output with respect to the steering angle input, the gain is not 1. Therefore, the above equation (10) is modified and divided into a steady gain portion and a gain 1 filter portion and expressed in the following equation (11). This is a part corresponding to the invention described in claim 6.
[0068]
[Formula 2]

The dead time is used to express a delay that cannot be adjusted only by the steering angle filtering process. This delay is mainly due to tire characteristics that cannot be expressed by a two-degree-of-freedom vehicle model. In this embodiment, the dead time is set to increase according to the vehicle speed. FIG. 4 shows the change in dead time depending on the vehicle speed. This is a part corresponding to the invention described in claims 7 to 9.
[0069]
  The yaw rate gain estimation detector 501 of the present embodiment will be described based on the flowchart shown in FIG.
  First, in step 1, it is checked whether or not the absolute value of the steering angle input value STR_in is less than 20 °. If it is less than 20 °, go to step 4. When STR_in is 20 ° or more, in step 2, first, the filter calculation of Expression (12) is performed, and further, dead time processing set according to the vehicle speed is performed, and STR_out is calculated. Next, in step 3, the formula (1) is calculated,Estimated yaw rate gainYG_ESTI is calculated. In step 4,Estimated yaw rate gainLet YG_ESTI be the target yaw rate gain Ref_YG.
[0070]
FIG. 6 shows how the yaw rate gain is estimated using the filter of equation (12) and the steering angle calculated by the dead time processing. As shown in the figure, it is possible to estimate the yaw rate gain with high accuracy without being affected by the steering speed or the like.
[0071]
Next, the target yaw rate gain setting unit 502 will be described. The target yaw rate gain setting unit 502 sets a target yaw rate gain according to the running state.
[0072]
In the present embodiment, as shown in FIG. 7, the target yaw rate gain Ref_YG is set so that the stability factor of the vehicle is always constant. In addition to the present embodiment, in a method of changing the target yaw rate gain Ref_YG according to the lateral acceleration, or in a rear wheel steering system, a steady yaw rate gain that is a parameter for determining a rear wheel steering amount in a steady state is set as a target yaw rate. A method of setting the gain Ref_YG is also conceivable.
[0073]
  Next, the brake force distribution control unit 503 will be described. The brake force distribution control unit 503 is a part that executes control corresponding to the invention described in claims 10 to 12, and includes a target yaw rate gain Ref_YG andEstimated yaw rate gainBrake force is distributed according to the deviation of YG_ESTI. Below, the brake force distribution control by the combination of front-back distribution and left-right distribution in the present embodiment will be described.
[0074]
  Understeering tendency and oversteering tendency are small (target yaw rate gain Ref_YG andEstimated yaw rate gainIf the absolute value of the deviation of YG_ESTI is small), the front and rear brake force distribution is performed, while the understeer tendency and the oversteer tendency are large (the target yaw rate gain Ref_YG andEstimated yaw rate gainIf the absolute value of the deviation of YG_ESTI is large), the left and right brake force distribution is performed.
[0075]
Further, when the steering angle is within ± 20 °, since the yaw rate gain estimate value = the target yaw rate gain is set as described above, the brake force command value is not calculated and the previous brake force command value is held. . However, when the deviation between the separately set target yaw rate and the actual yaw rate is within a predetermined value, the brake control is terminated.
[0076]
The brake force distribution control unit 504 of the present embodiment will be described based on the flowchart shown in FIG.
[0077]
  First, at step 11, the magnitude of the steering angle STR is checked. If the steering angle STR is ± 20 ° or more, the process proceeds to step 21; otherwise, the process proceeds to step 111.
  The braking force is determined by PI control. At step 21, the target yaw rate gain Ref_YGEstimated yaw rate gainThe brake force command value Brkcom is calculated by multiplying the integral value ErrI and the deviation amount ErrP of YG_ESTI by the gains BrkI and BrkP, respectively.
Brkcom = ErrI × BrkI + ErrP × BrkP (13)
  Next, in step 41, the magnitude of the brake force command value Brkcom is checked. In the case of OS1 ≦ Brkcom ≦ US1, the brake distribution control is not performed because the actual yaw rate gain is close to the target yaw rate gain.
[0078]
If Brkcom> US1, proceed to step 51. This is a case where the actual yaw rate gain is smaller or smaller than the target yaw rate gain (understeer tendency). If Brkcom <OS1, proceed to step 81. This is a case where the actual yaw rate gain is larger or larger than the target yaw rate gain (oversteer tendency). In step 51, it is determined whether the understeer tendency is large. In the case of Brkcom ≦ US2, it is determined that the understeer tendency is small, and in step 61, a command value is output to the brake pressure control unit 504 so as to brake the rear wheel. By braking the rear wheel, the cornering force of the rear wheel is reduced, and the cornering force of the front wheel is relatively increased to suppress understeer.
[0079]
In step 51, if Brkcom> US2, it is determined that the understeer tendency is large, and in step 71, a command value is output to the brake pressure control unit 504 so as to brake the turning inner wheel. Brake is applied to the turning inner ring to generate an inward moment and suppress understeer.
[0080]
In step 81, it is determined whether the oversteer tendency is large. In the case of Brkcom ≧ OS2, it is determined that the oversteer tendency is small, and a command value is output to the brake pressure control unit 504 so as to brake the front wheels in step 91. By braking the front wheel, the cornering force of the front wheel is reduced, and the cornering force of the rear wheel is relatively increased to suppress oversteer. If Brkcom <OS2 in step 81, it is determined that the oversteer tendency is large, and in step 101, a command value is output to the brake pressure control unit 504 so as to brake the outer turning wheel. Brake is applied to the turning outer wheel to generate an outward moment and suppress oversteer.
[0081]
If the steering angle STR is less than ± 20 ° at step 11, the difference Err_Yaw between the target yaw rate Ref_Yaw and the actual yaw rate yawrate is calculated at step 111.
[0082]
Err_Yaw = | Ref_Yaw-yawrate | (14)
In the present embodiment, the target yaw rate is calculated by the following equation based on equation (10).
Ref_Yaw = [(b₁₁sa₂₂b₁₁+ a₁₂b₂₁) / {S²-(A₁₁+ a₂₂S + a₁₁a₂₂-a₁₂a₂₁}] Θ_s    ... (15)
Next, in step 121, the magnitude of the yaw rate deviation Err_Yaw is checked. When the deviation Err_Yaw is smaller than the predetermined value ES1, the brake control is finished. When the deviation Err_Yaw is larger than the predetermined value ES1, the process proceeds to step 41, and the magnitude of the brake force command value Brkcom is checked. That is, when the steering angle STR is less than ± 20 °, the brake force command values from step 21 to step 31 are not calculated, and each wheel is braked using the previous brake force command values. However, when the yaw rate deviation Err_Yaw becomes smaller than the predetermined value ES1, the brake control is terminated.
[0083]
When the understeer tendency or oversteer tendency is relatively small, the brake front / rear distribution control is performed with a gentle change in vehicle behavior. On the other hand, when the understeer tendency or oversteer tendency is large, the brake Perform distribution control. Switching from the front / rear distribution control to the left / right distribution control is performed gradually rather than suddenly, thereby preventing disturbance of vehicle behavior.
[0084]
In this embodiment, the front / rear and left / right distribution is performed, but smoother and more effective control is achieved by controlling the brake pressure of each wheel, such as the front wheel inner wheel and the rear wheel outer wheel, according to the state of the vehicle. Can be done.
[Brief description of the drawings]
FIG. 1 is an overall system diagram showing a vehicle motion control device according to an embodiment.
FIG. 2 is a control block diagram showing the vehicle motion control device of the embodiment.
FIG. 3 is a time chart showing a state of yaw rate gain estimation using the secondary low-pass filter of the embodiment.
FIG. 4 is a time delay characteristic diagram illustrating an example of a method for setting a time delay applied to the steering angle according to the embodiment.
FIG. 5 is a flowchart illustrating a control flow in a yaw rate gain estimation detection unit according to the embodiment.
FIG. 6 is a time chart showing a state of yaw rate gain estimation using the vehicle model filter and the dead time according to the embodiment.
FIG. 7 is a target yaw rate gain characteristic diagram showing an example of a target yaw rate gain setting method according to the embodiment;
FIG. 8 is a flowchart showing a control flow in a brake force distribution control unit of the embodiment.
[Explanation of symbols]
1 Steering angle sensor
2 Vehicle speed sensor
3 Yaw rate sensor
4 Brake actuator
5 Vehicle motion controller
501 Yaw rate gain estimation detector
502 Target yaw rate gain setting section
503 Brake force distribution control unit
504 Brake pressure control unit

Claims (12)

Vehicle speed detection means for detecting the speed of the vehicle;
Yaw rate detection means for detecting the yaw rate of the vehicle;
Steering angle detection means for detecting the steering angle;
Yaw rate gain estimation detection means for estimating and detecting a yaw rate gain of the vehicle based on the vehicle speed detection value, the yaw rate detection value, and the steering angle detection value;
Target yaw rate gain setting means for setting a target value of the yaw rate gain;
Braking force distribution means for calculating a braking force command value for each wheel so as to eliminate a deviation between the estimated yaw rate gain value and the target yaw rate gain;
Brake pressure control means for controlling the brake pressure of each wheel according to the brake force command value;
In a vehicle motion control device having
The yaw rate gain estimation detection means includes steering angle filter processing calculation means for performing a filter process for adjusting a delay from the yaw rate to the steering angle detection value, and sets the yaw rate detection value as a dividend while performing the steering angle filter process. A vehicle motion control device characterized in that a result obtained by performing division with an arithmetic output value as a divisor is used as an estimated yaw rate gain value . The vehicle motion control device according to claim 1,
The yaw rate gain estimation detection means performs the steering angle filter processing calculation only when the absolute value of the steering angle detection value is greater than or equal to a predetermined value, calculates a yaw rate gain estimation value by the division, and calculates the steering angle detection value. When the absolute value is less than a predetermined value, the vehicle motion control device is configured to use the estimated yaw rate gain value as the target yaw rate gain setting value. The vehicle motion control device according to claim 1 or 2,
The vehicle motion control apparatus, wherein the steering angle filter processing calculation means is configured to change a filter characteristic in accordance with a vehicle speed. The vehicle motion control device according to claim 1 or 2,
The vehicle motion control device, wherein the steering angle filter processing calculation means constitutes a filter using a transfer characteristic of a yaw rate with respect to a steering input. The vehicle motion control device according to claim 1 or 2,
The vehicle motion control device according to claim 1, wherein the steering angle filter processing calculation means constitutes a filter using a two-degree-of-freedom vehicle model in yawing and lateral directions. The vehicle motion control device according to claim 1 or 2,
The steering angle filter processing calculation means is a filter that transforms the two-degree-of-freedom vehicle model in yawing and lateral directions into a steady gain portion and a gain 1 filter portion, and applies the gain 1 filter portion to the detected steering angle value. A vehicle motion control device. The vehicle motion control device according to claim 1,
The steering angle filter processing calculation means performs a filter process and a dead time process on the detected steering angle value. The vehicle motion control device according to claim 7, wherein
The vehicle steering control device, wherein the steering angle filter processing calculation means changes the dead time according to the detected vehicle speed. The vehicle motion control device according to claim 8,
The steering angle filter processing calculation means sets the dead time longer as the vehicle speed detection value is larger. The vehicle motion control device according to any one of claims 1 to 9,
The vehicle motion control device according to claim 1, wherein the brake force distribution means controls a cornering force balance of the front and rear wheels by front and rear brake distribution so as to eliminate a deviation between the estimated yaw rate gain and the target yaw rate gain. The vehicle motion control device according to any one of claims 1 to 9,
The vehicle motion control device according to claim 1, wherein the brake force distribution means controls a difference between left and right braking force by left and right brake force distribution so as to eliminate a deviation between the yaw rate gain estimated value and the target yaw rate gain. The vehicle motion control device according to any one of claims 1 to 9,
The brake force distribution means distributes front and rear brake forces when the deviation between the yaw rate gain estimated value and the target yaw rate gain is small, and distributes left and right brake force when the deviation is large. A vehicle motion control device.

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