JP2004237928A - Vehicle motion control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicle motion control device capable of stably controlling a behavior of a vehicle without imparting unnatural feeling to a driver, even if changing vehicle speed during the vehicle motion control. <P>SOLUTION: This control device is provided with a rear wheel steering angle imparting means to impart a rear wheel steering angle of the vehicle and a vehicle motion target value calculating means for calculating a vehicle motion target value so that a response characteristic of a plane behavior of the vehicle may be a prescribed response characteristic based on a steering angle detection value, a vehicle speed detection value and a vehicle speed dependent constant set as a map for every vehicle speed in advance. The vehicle motion target value calculating means is provided with a two-wheel steering time vehicle speed dependent constant calculating part for calculating the vehicle speed dependent constant based on a vehicle parameter at a two-wheel steering time and an interpolation operation part for performing an interpolation operation for the vehicle speed dependent constant based on the calculated two-wheel steering time vehicle speed dependent constant and the speed dependent constant set as the map for every vehicle speed in advance. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

なお、式１において、Ｇψ’，ω_ｎ，ｎ_１及びζは車速依存定数であって、Ｇψ’はヨーレイトゲイン、ω_ｎは固有角周波数、ｎ_１は零点相当値、ζは減衰係数である。これらの車速依存定数は、予め設定した車速と車速依存定数との対応を表す制御マップに基づいて設定される。
【００１４】
図６は車速Ｖに対するヨーレイトゲインＧψ’の関係を表すマップである。この車速依存定数は、操舵角θの変化に対するヨーレイトψ’の応答特性において、ヨーレイトゲインＧψ’は定常ゲイン、すなわち、操舵角に対する定常的なヨーレイトを特定し、固有角周波数ω_ｎはその振動周波数を特定し、零点相当値ｎ_１は操舵角の変化に対するヨーレイトの立ち上がりの速さ、つまり、ヨーレイトの立ち上がり特性を特定し、減衰係数ζは収束の速さ、つまり、ヨーレイトの収束性を特定している。したがって、車速依存定数を所定の応答特性となり得る値に設定し、設定した車速依存定数と前記式（１）とに基づき算出した目標ヨーレイトψ’^＊の応答特性は、所定の応答特性となる。
【００１５】
よって、車速依存定数を車速に応じて設定することにより、目標ヨーレイトψ’^＊の応答特性は、車速に応じて異なる応答特性となり、また、ヨーレイトゲインＧψ’，固有角周波数ω_ｎ，零点相当値ｎ_１，減衰係数ζを個別に変更することによって、例えば定常ゲインのみ、或いは振動周波数のみが異なる応答特性を得ることができる。
【００１６】
図３は、車両運動目標値設定部４１の構成を表すブロック図である。後輪舵角指令値演算部４２において、目標ヨー角加速度ψ’’^＊を必要としていることから、目標ヨー角加速度ψ’’^＊を算出した後、これを積分処理して目標ヨーレイトψ’^＊を算出する。尚、図中のＢ_０，Ｂ_１，Ｆ_０，Ｆ_１は次式に基づき算出した値である。
Ｂ_０＝ω_ｎ ^２
Ｂ_１＝２ζω_ｎ
Ｆ_０＝ｎ_１ω_ｎ ^２
Ｆ_１＝ω_ｎ ^２−Ｂ_１・Ｆ_１
【００１７】
後輪舵角指令値演算部４２では、目標ヨーレイトψ’^＊，及び目標ヨー角加速度ψ’’^＊と、操舵角センサ１４からの操舵角検出値θ及び車速センサ１６からの車速検出値Ｖとを基に、下記式（２）に基づいて、に自由度車両運動方程式の逆計算によって、目標ヨーレイトψ’^＊に実際のヨーレイトを一致させ得る後輪舵角を算出し、これを目標後輪舵角δ^＊とする。
（式２）

ただし、
Ｖｙ：車両横速度
β_Ｆ：前輪横滑り角
β_Ｒ：後輪横滑り角
Ｌ_Ｆ：前車軸から車両重心点までの距離
Ｌ_Ｒ：後車軸から車両重心点までの距離
Ｃ_Ｆ：前輪のコーナリングフォース
Ｃ_Ｒ：後輪のコーナリングフォース
Ｋ_Ｒ：車両の後輪のコーナリングパワー
ｅＫ_Ｆ：車両の前輪の等価コーナリングパワー（前輪のコーナリングパワーであるが、ステアリング剛性の影響によるステアリング角に対するコーナリングパワー低下分も加味した値）
Ｉ_Ｚ：車両のヨー慣性モーメント
Ｍ：車両の重量
Ｎ：ステアリングギヤ比
である。
【００１８】
後輪舵角サーボ演算部４３では、後輪舵角指令値δ^＊と後輪舵角センサの後輪舵角検出信号δとの偏差に基づいて、ロバストモデルマッチング制御を用いたサーボ演算を行い、後輪操舵アクチュエータ４に制御信号を出力する。
【００１９】
次に、上記実施の形態の動作について説明する。図４は、車両運動制御コントローラ４が行う処理手中を示すフローチャートである。なお、この処理は、所定制御周期（例えば１０ｍｓｅｃ）で実行される。
【００２０】
ステップ１０１では、操舵角センサ１４からの操舵角検出値θ、車速センサ１６からの車速検出値Ｖ、後輪舵角センサ１７からの後輪舵角検出信号δを読み込む。
【００２１】
ステップ１０２では、予め設定した車速と車速依存定数との対応を表す制御マップを参照し、車速に対応するヨーレイトゲインＧψ’，減衰係数ζ，固有角周波数ω_ｎ，零点相当値ｎ_１を設定する。図５に示すように、マップは所定車速毎に設けられた値を持っているため、検出された車速がマップ上の所定車速以外のポイントにあるときは、当該車両の２ＷＳ特性に基づく補間演算によりマップ間の値を求めることで、各車速依存定数を設定する。尚、詳細については後述する。
【００２２】
ステップ１０３では、設定した車速依存定数と前記式（１）と、操舵角検出値θとに基づいて目標ヨーレイトψ’^＊を算出する。
【００２３】
ステップ１０４では、算出した目標ヨーレイトψ’^＊に実際のヨーレイトψ’を一致させることの可能な後輪舵角指令値δ^＊を前記式（２）に基づいて算出する。
【００２４】
ステップ１０５では、後輪舵角指令値δ^＊と、後輪舵角検出値δとの偏差に基づいて、例えばロバストモデルマッチング制御を落ちいたサーボ演算を行い、後輪操舵アクチュエータ３に出力する制御信号を算出する。
【００２５】
（車速依存定数算出における補間演算処理）
次に、ステップ１０２について詳細に説明する。各車速依存定数を設定する際に直線補間を用いることで誤差が生じ、結果的に運転者に違和感を与える虞がある。この現象について説明する。ここで、簡略化するため、車速依存定数を２ＷＳ（後輪を転舵しない）車両の持つ車速依存定数と同じ値に設定していると仮定する。図６の車速Ａ以下の領域では、車速依存定数に基づいて算出される目標ヨーレイトψ’^＊は２ＷＳで生じるヨーレイト特性に等しくなるため、この目標ヨーレイトψ’^＊に基づいて算出される目標後輪舵角δ^＊は０となるはずである。
【００２６】
しかし、車速と車速依存定数との対応を表す制御マップは所定車速毎に値を有しているため、各車速ポイント間の値は直線補間で求めており、図７のマップ拡大図に示すように、厳密には２ＷＳ特性と一致しない領域が存在する。例えば車速ａ１のときの実際の２ＷＳ特性と補間による特性との差ΔＧψ’はｐとなり、車速ａ２のときの差ΔＧψ’は０となり、また車速ａ３のときの差ΔＧψ’はｑ（＞ｐ）となる。このため、目標ヨーレイトψ’^＊が２ＷＳ車両で生じるヨーレイト特性と異なり、誤差ｐやｑに対応して目標ヨーレイトψ’^＊を実現するように、ある値を持った（０以外）後輪舵角指令値δ^＊が算出される。
【００２７】
この現象は、一定の車速では運転者に与える違和感はない（たとえ後輪舵角が生じても微少かつ一定値なので影響が少ない）。しかしながら、車速が変化する場合には、後輪舵角が変動する（２ＷＳ特性との誤差が大きくなったり小さくなったりする：ｐ→０→ｑもしくはｑ→０→ｐを補償するために変動）ため、運転者が違和感を感じる虞がある。
【００２８】
そこで、車速と車速依存定数との対応を表す制御マップを参照する際、２ＷＳの車両パラメータを利用した補間演算を行うことで、上記誤差による影響を抑えるようにした。２ＷＳの車両パラメータを用いて、車速Ｖに対するヨーレイトゲインは下記式（３）により表される。
（式３）
Ｇ２ＷＳψ’（Ｖ）＝〔１．０／（１．０＋Ａ・Ｖ・Ｖ）〕・｛Ｖ／｛Ｎ・（Ｌ_Ｆ＋Ｌ_Ｒ）｝｝
ただし、Ａはスタビリティファクタであり、下記式（４）により表される。
（式４）
Ａ＝−〔Ｍ・（Ｌ_Ｆ／ｅＫ_Ｆ−Ｌ_Ｒ・Ｋ_Ｒ）／｛２．０・（Ｌ_Ｆ＋Ｌ_Ｒ）２・ｅＫ_Ｆ・Ｋ_Ｒ｝〕
【００２９】
図５は２ＷＳの車両パラメータを利用した補間演算処理を表すフローチャートである。
【００３０】
ステップ２０１では、車速検出値Ｖを１０ｎ＋ｖ_０の値に変換する。
【００３１】
ステップ２０２では、２ＷＳのヨーレイトゲインＧ_２ＷＳψ’（１０ｎ）に対するヨーレイトゲインＧψ’（１０ｎ）の比率ｋ（ｎ）と、２ＷＳのヨーレイトゲインＧ_２ＷＳψ’（１０（ｎ＋１））に対するヨーレイトゲインＧψ’（１０（ｎ＋１））の比率ｋ（ｎ＋１）を算出する。
【００３２】
ステップ２０３では、車速検出値Ｖにおける比率ｋｖを下記式により算出する。
ｋｖ＝｛ｖ_０・ｋ（ｎ＋１）＋ｖ_１・ｋ（ｎ）｝
ただし、ｖ_０＋ｖ_１＝１０とする。
【００３３】
ステップ２０４では、補間ヨーレイトゲインＧψ’を下記式により算出する。Ｇψ’＝Ｇ２ＷＳψ’（Ｖ）・ｋｖ
【００３４】
上記処理内容を図８を用いて説明する。まず、車速検出値Ｖを１０ｎ＋ｖ_０の値に変換し、１０ｎ及び１０（ｎ＋１）における２ＷＳのヨーレイトゲインＧ_２ＷＳψ’を演算し、更にマップ上のヨーレイトゲインＧψ’を読み込む。これらのヨーレイトゲインから、１０ｎにおける２ＷＳ／マップ比率ｋ（ｎ）と、１０（ｎ＋１）における２ＷＳ／マップ比率ｋ（ｎ＋１）を算出する。
【００３５】
次に、これらの比率から、１０ｎと１０（ｎ＋１）の間に存在するｖ_０における２ＷＳのヨーレイトゲインと補間ヨーレイトゲインの比率ｋｖを算出する。ここで、車速検出値Ｖにおける２ＷＳヨーレイトゲインは計算により算出できるため、この２ＷＳヨーレイトゲインＧ２ＷＳψ’（Ｖ）と比率ｋｖを用いて、補間ヨーレイトゲインを算出する。
【００３６】
以上説明したように、２ＷＳの車両パラメータを利用した補間演算処理を行うことで、車速依存定数を補完して得られる定数値がきわめて自然なカーブを描くことが可能となる。また、２ＷＳと同じ特性を指示した速度域では、定数マップを補間した結果が、２ＷＳのパラメータから演算した値に一致するようになるため、後輪舵角指令値として確実に０を算出することができる。
【００３７】
よって、２ＷＳの車両パラメータに基づく車速依存定数の補間演算を行うことで、各マップのポイント間の値を直線補間することで起因する車両挙動への悪影響を抑えることができる（請求項１に対応）。
【００３８】
（その他の実施例）
以上、第１実施例について説明してきたが、本発明は上述の構成に限られるものではなく、例えば、前輪に補助舵角を付与する前輪舵角付与手段を備えた車両に適用してもよいし、さらに、左右制動輪のブレーキ液圧差を用いて車両のヨーレイトを制御可能なブレーキ制御手段を備えた車両に適用してもよい。これらの車両に本願発明の車速依存定数補間処理を適用することで、制御目標値（例えば目標ヨーレイトや目標横速度等）が急激に変動することがなく、さらに安定した車両運動制御を達成することができる。
【図面の簡単な説明】
【図１】第１実施例における基本構成を示す概略図である。
【図２】第１実施例における、操舵制御コントローラの構成を表すブロック図である。
【図３】第１実施例における、目標値生成部の構成を表すブロック図である。
【図４】第１実施例における、操舵制御を表すフローチャートである。
【図５】第１実施例における、車速依存定数の補間演算処理を表すフローチャートである。
【図６】第１実施例における、車速−ヨーレイトゲインマップである。
【図７】車速−ヨーレイトゲインマップの拡大図である。
【図８】第１実施例における、車速依存定数の補間演算処理を説明する説明図である。
【符号の説明】
１Ｌ，１Ｒ 前輪
２Ｌ，２Ｒ 後輪
３ 後輪操舵アクチュエータ
４ 制御装置
８ タイロッド
１１ 駆動モータ
１４ 操舵角センサ
１６ 車速センサ
１７ 後輪舵角センサ
４１ 車両運動目標値設定部
４２ 後輪舵角指令値演算部
４３ 後輪舵角サーボ演算部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a vehicle motion control device that controls the motion of a vehicle at the time of steering input to a front wheel or the like.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, for example, a technique described in Patent Document 1 is known. This publication controls the yaw rate and the like of the vehicle when the steering wheel is steered to maintain the stability of the vehicle when the steering wheel is steered. Specifically, based on the steering angle and the vehicle speed, a target yaw rate is calculated so that the response characteristic relating to the plane behavior of the vehicle can be a predetermined response characteristic, and a yaw rate generated in the vehicle is required to match this target value. The yaw motion of the vehicle according to the target yaw rate is calculated by calculating the rear wheel steering angle command value by a motion equation based on the vehicle specification value and controlling the rear wheel actual steering angle to follow the rear wheel steering angle command value. It is to be.
[0003]
The target yaw rate is calculated by setting a response characteristic of the target yaw rate to a change in the steering angle as a first-order / second-order transfer function and setting a vehicle speed-dependent constant in advance according to the vehicle speed. As a result, the yaw rate steering responsiveness during low-speed running is maintained, and a vehicle behavior excellent in steering responsiveness and stability without giving a driver an uncomfortable feeling during high-speed running is realized.
[0004]
[Patent Document 1]
JP-A-10-007010 (see page 4).
[0005]
[Problems to be solved by the invention]
However, in the above-described vehicle motion control device, the vehicle speed dependent constant is stored in advance as a discrete value as a map for each vehicle speed, and the vehicle speed at the time of calculating the target yaw rate does not match a point on the map axis. , Linear interpolation is performed based on adjacent points on the map to calculate a vehicle speed dependent constant. Therefore, an error caused by the linear interpolation affects the target yaw rate and the like, and as a result, the rear wheel steering angle may be affected. Therefore, in a case where the vehicle speed changes during steering, such as turning braking, there is a possibility that the driver may feel uncomfortable when the rear wheel steering angle becomes a movement other than the desired movement.
[0006]
The present invention has been made in view of the above problems, and in a vehicle motion control device, a vehicle motion control device capable of stably controlling the behavior of a vehicle without giving a driver an uncomfortable feeling even when the vehicle speed changes during the vehicle motion control. The purpose is to provide.
[0007]
[Means for Solving the Problems]
To achieve the above object, a steering wheel steering angle detecting means for detecting a steering wheel steering angle, a vehicle speed detecting means for detecting a vehicle speed, a rear wheel steering angle providing means for providing a rear wheel steering angle of the vehicle, and a rear wheel steering angle Based on the rear wheel steering angle detecting means, the steering angle detected value, the vehicle speed detected value, and a vehicle speed dependent constant set in advance as a map for each vehicle speed, the response characteristic relating to the plane behavior of the vehicle is a predetermined value. Vehicle motion target value calculating means for calculating a vehicle motion target value for obtaining response characteristics, and rear wheel steering angle command value calculation for calculating a rear wheel steering angle command value required to realize the vehicle motion target value Means, and a servo operation means for providing a control signal to the rear wheel steering angle applying means so that the detected rear wheel steering angle coincides with the rear wheel steering angle command value, the vehicle motion control device, The vehicle motion target value calculating means includes two wheels A two-wheel-steering-time vehicle-speed-dependent constant calculating unit for calculating a vehicle-speed-dependent constant based on the vehicle parameter at the time of steering; and The provision of the interpolation calculation unit for performing the interpolation calculation of the vehicle speed dependent constant has led to the solution of the above problem.
[0008]
Effect of the Invention
According to the present invention, by interpolating the vehicle speed dependent constant based on the vehicle parameter characteristics at the time of two-wheel steering, it is possible to suppress the fluctuation of the control command value even if the vehicle speed changes, Steering control can be achieved without giving an uncomfortable feeling to the driver.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the vehicle steering control device according to the present invention will be described based on examples, but the present invention is not limited to the examples.
[0010]
(First embodiment)
FIG. 1 is an overall system diagram showing a basic configuration in a first embodiment of the present invention. In the figure, a steering angle variable mechanism (auxiliary steering means) 3 for mechanically steering left and right rear wheels (non-steered wheels) 2L and 2R, and a control device 4 for driving and controlling the steering angle variable mechanism 3 are provided. ing.
[0011]
The variable steering angle mechanism 3 includes a sliding screw 9 formed on a tie rod 8 between knuckle arms 5L, 5R attached to left and right rear wheels 2L, 2R via kingpin shafts 6L, 6R and ball joints 7L, 7R. A nut 10 having external teeth formed on an outer peripheral surface thereof is screwed, and external teeth 12 attached to a rotation shaft of a drive motor 11 composed of a step motor are meshed with the external teeth of the nut 10. The tie rod 8 is moved in the left-right direction by rotating and driving the rear wheel 11, and the rear left and right wheels are steered. Reference numeral 13 denotes a return spring that returns the tie rod 8 to the neutral position.
[0012]
FIG. 2 shows a functional block diagram of the control device 4. As shown in FIG. 2, the control device 4 provides a target yaw rate as a vehicle motion target value based on a front wheel steering angle detection value θ from the front wheel steering angle sensor 14 and a vehicle speed detection value V from the vehicle speed sensor 16. A vehicle motion target value setting unit (vehicle target value calculating means) 41 for calculating ψ ′ ^* and a target yaw angular acceleration ψ ″ ^* is provided. Also, the target yaw rate [psi ^'* and the target yaw angle acceleration [psi'^'* from the vehicle motion target value setting unit 41, based on the front wheel steering angle detected value θ and the vehicle speed detection value V, the target rear wheel steering angle [delta] ^* Is provided. Further, a rear wheel steering angle servo calculation for supplying a control signal to the rear wheel steering actuator 3 so that the rear wheel steering angle detection signal δ from the rear wheel steering angle sensor 17 matches the target rear wheel steering angle δ ^*. A part 43 is provided.
[0013]
The vehicle motion target value setting unit 41 calculates a target yaw rate as a vehicle motion target value for the front wheel steering angle detected value θ based on a transfer function between a front wheel steering angle detected value and a target yaw rate ψ ′ ^* shown in the following equation. ψ ' ^* is calculated.
(Equation 1)

In Equation 1, Gψ ′, ω _n , n ₁ and ζ are vehicle speed dependent constants, Gψ ′ is a yaw rate gain, ω _n is a natural angular frequency, n ₁ is a zero-point equivalent value, and ζ is an attenuation coefficient. . These vehicle speed dependent constants are set on the basis of a control map representing a correspondence between a preset vehicle speed and a vehicle speed dependent constant.
[0014]
FIG. 6 is a map showing the relationship between the vehicle speed V and the yaw rate gain G # '. In the response characteristic of the yaw rate ψ ′ with respect to the change in the steering angle θ, the yaw rate gain Gψ ′ specifies a steady gain, that is, a steady yaw rate with respect to the steering angle, and the natural angular frequency ω _n is the vibration frequency identify the zeros corresponding value n ₁ rate of rise of yaw rate with respect to change in the steering angle, that is, to identify the rise characteristic of the yaw rate, the ζ damping coefficient rate of convergence, that is, to identify convergence of the yaw rate ing. Therefore, the vehicle speed dependent constant is set to a value that can provide a predetermined response characteristic, and the response characteristic of the target yaw rate ψ ′ ^* calculated based on the set vehicle speed dependent constant and Equation (1) is a predetermined response characteristic.
[0015]
Therefore, by setting the vehicle speed dependent constant according to the vehicle speed, the response characteristics of the target yaw rate ψ ′ ^* become different response characteristics according to the vehicle speed, and the yaw rate gain Gψ ′, the natural angular frequency ω _n , and the zero-point equivalent value By individually changing n ₁ and the damping coefficient ζ, it is possible to obtain a response characteristic that differs only in, for example, only the steady-state gain or only the vibration frequency.
[0016]
FIG. 3 is a block diagram illustrating a configuration of the vehicle motion target value setting unit 41. In the rear wheel steering angle command value calculating section 42, ^'since in need of ^*, target yaw angular acceleration [psi' target yaw angle acceleration [psi 'After calculating ^{the' *,} target yaw rate [psi this by integration processing ^'* Is calculated. Note that B ₀ , B ₁ , F ₀ , and F ₁ in the figure are values calculated based on the following equation.
B ₀ = ω _n ²
B ₁ = 2ζω _n
F ₀ = n ₁ ω _n ²
F ₁ = ω _n ² −B ₁ · F ₁
[0017]
The rear wheel steering angle command value calculation unit 42 calculates the target yaw rate ψ ′ ^* and the target yaw angular acceleration ψ ″ ^* , the steering angle detection value θ from the steering angle sensor 14 and the vehicle speed detection value V from the vehicle speed sensor 16. Based on the following equation (2), a rear wheel steering angle that allows the actual yaw rate to match the target yaw rate ψ ′ ^* is calculated based on the following equation (2). The steering angle is δ ^* .
(Equation 2)

However,
Vy: vehicle lateral velocity beta _F: front wheel side slip angle beta _R: rear-wheel slip angle L _F: the distance L _R from the front axle to vehicle center of _gravity: Distance C _F from the rear axle to the vehicle center of _gravity: front wheel cornering force C _R: rear wheel cornering force K _R: cornering power of the rear wheels of the vehicle eK _F: is a front equivalent cornering power (front wheel cornering power of the vehicle, taking into account also the cornering power decrease amount with respect to the steering angle due to the influence of the steering stiffness Value)
I _Z : yaw moment of inertia of the vehicle M: weight of the vehicle N: steering gear ratio.
[0018]
The rear wheel steering angle servo calculation unit 43 performs servo calculation using robust model matching control based on the deviation between the rear wheel steering angle command value δ ^* and the rear wheel steering angle detection signal δ of the rear wheel steering angle sensor. And outputs a control signal to the rear wheel steering actuator 4.
[0019]
Next, the operation of the above embodiment will be described. FIG. 4 is a flowchart showing the processing performed by the vehicle motion controller 4. This processing is executed at a predetermined control cycle (for example, 10 msec).
[0020]
In step 101, the steering angle detection value θ from the steering angle sensor 14, the vehicle speed detection value V from the vehicle speed sensor 16, and the rear wheel steering angle detection signal δ from the rear wheel steering angle sensor 17 are read.
[0021]
In step 102, a yaw rate gain Gψ ′, a damping coefficient ζ, a natural angular frequency ω _n , and a zero-point-corresponding value n ₁ corresponding to the vehicle speed are set with reference to a control map representing a correspondence between a vehicle speed and a vehicle speed dependent constant set in advance. . As shown in FIG. 5, since the map has a value provided for each predetermined vehicle speed, when the detected vehicle speed is at a point other than the predetermined vehicle speed on the map, the interpolation calculation based on the 2WS characteristic of the vehicle is performed. By calculating the values between the maps, the vehicle speed dependent constants are set. The details will be described later.
[0022]
In step 103, the target yaw rate ψ ' ^* is calculated based on the set vehicle speed-dependent constant, the equation (1), and the detected steering angle θ.
[0023]
In step 104, a rear wheel steering angle command value δ ^* that allows the actual yaw rate ψ ′ to match the calculated target yaw rate ψ ′ ^* is calculated based on the above equation (2).
[0024]
In step 105, control is performed based on the deviation between the rear wheel steering angle command value δ ^* and the rear wheel steering angle detection value δ, for example, to perform a servo calculation with the robust model matching control reduced, and output it to the rear wheel steering actuator 3. Calculate the signal.
[0025]
(Interpolation calculation processing for calculating the vehicle speed dependent constant)
Next, step 102 will be described in detail. When linear interpolation is used when setting each vehicle speed dependent constant, an error occurs, and as a result, the driver may feel uncomfortable. This phenomenon will be described. Here, for the sake of simplicity, it is assumed that the vehicle speed dependent constant is set to the same value as the vehicle speed dependent constant of a 2WS (the rear wheel is not steered) vehicle. In the region below the vehicle speed A in FIG. 6, the target yaw rate ψ ′ ^* calculated based on the vehicle speed dependent constant becomes equal to the yaw rate characteristic generated at 2WS, so the target rear wheel calculated based on the target yaw rate ψ ′ ^* The steering angle δ ^* should be zero.
[0026]
However, since the control map representing the correspondence between the vehicle speed and the vehicle speed-dependent constant has a value for each predetermined vehicle speed, the value between each vehicle speed point is obtained by linear interpolation, as shown in the enlarged map of FIG. There is an area that does not exactly match the 2WS characteristic. For example, the difference ΔGψ ′ between the actual 2WS characteristic at the vehicle speed a1 and the characteristic by interpolation is p, the difference ΔGψ ′ at the vehicle speed a2 is 0, and the difference ΔGψ ′ at the vehicle speed a3 is q (> p). It becomes. Therefore, 'unlike the yaw rate ^{characteristics *} occurs 2WS vehicle, target yaw rate ψ corresponding to the error p and q' target yaw rate ψ to achieve ^*, with a certain value (non-zero) rear-wheel steering angle Command value δ ^* is calculated.
[0027]
This phenomenon does not give the driver an unpleasant sensation at a constant vehicle speed (even if the rear wheel steering angle occurs, the influence is small because it is very small and constant). However, when the vehicle speed changes, the rear wheel steering angle fluctuates (the error from the 2WS characteristic increases or decreases: f → 0 → q or f → 0 → p to compensate). Therefore, the driver may feel uncomfortable.
[0028]
Therefore, when referring to a control map representing the correspondence between the vehicle speed and the vehicle speed-dependent constant, the influence of the above error is suppressed by performing an interpolation calculation using a vehicle parameter of 2WS. Using the vehicle parameters of 2WS, the yaw rate gain with respect to the vehicle speed V is expressed by the following equation (3).
(Equation 3)
G2WSψ '(V) = [1.0 / (1.0 + A · V · V) ] _{· {V / {N · (} L F + L R)}}
Here, A is a stability factor, and is represented by the following equation (4).
(Equation 4)
A = - _{[M · (L F / eK F} -L R · K R) / {2.0 · (L F + L R) 2 · eK F · K R} ]
[0029]
FIG. 5 is a flowchart showing an interpolation calculation process using 2WS vehicle parameters.
[0030]
In step 201, it converts the vehicle speed detecting value V to the value of 10n + _{v 0.}
[0031]
In step 202, the ratio k (n) of the yaw rate gain Gψ '(10n) to the yaw rate gain G _2WS ψ' (10n) of 2WS, and the yaw rate gain Gψ 'to the yaw rate gain G _2WS ψ' (10 (n + 1)) of 2WS. The ratio k (n + 1) of (10 (n + 1)) is calculated.
[0032]
In step 203, the ratio kv at the vehicle speed detection value V is calculated by the following equation.
kv = {v ₀ · k (n + 1) + v ₁ · k (n)}
Here, v ₀ + v ₁ = 10.
[0033]
In step 204, the interpolated yaw rate gain Gψ 'is calculated by the following equation. Gψ '= G2WSψ' (V) · kv
[0034]
The above processing will be described with reference to FIG. First, to convert the vehicle speed detecting value V to the value of 10n + _{v 0,} 'then calculates, further yaw rate gain Gψ on map' 10n and 10 (n + 1) 2WS the yaw rate gain _{G 2WS} [psi in read. From these yaw rate gains, a 2WS / map ratio k (n) at 10n and a 2WS / map ratio k (n + 1) at 10 (n + 1) are calculated.
[0035]
Then, from these ratios to calculate the 10n and 10 (n + 1) ratio kv yaw rate gain and the interpolation yaw rate gain of 2WS in _{v 0} that exists between. Here, since the 2WS yaw rate gain at the vehicle speed detection value V can be calculated by calculation, the interpolation yaw rate gain is calculated using the 2WS yaw rate gain G2WSψ ′ (V) and the ratio kv.
[0036]
As described above, by performing the interpolation calculation processing using the vehicle parameters of 2WS, the constant value obtained by complementing the vehicle speed dependent constant can draw a very natural curve. In the speed range in which the same characteristics as 2WS are specified, the result of interpolation of the constant map becomes equal to the value calculated from the 2WS parameter. Therefore, it is necessary to reliably calculate 0 as the rear wheel steering angle command value. Can be.
[0037]
Therefore, by performing the interpolation calculation of the vehicle speed dependent constant based on the vehicle parameter of 2WS, it is possible to suppress the adverse effect on the vehicle behavior caused by linearly interpolating the value between the points of each map. ).
[0038]
(Other Examples)
Although the first embodiment has been described above, the present invention is not limited to the above-described configuration, and may be applied to, for example, a vehicle including front wheel steering angle applying means for applying an auxiliary steering angle to front wheels. Further, the present invention may be applied to a vehicle provided with brake control means capable of controlling the yaw rate of the vehicle using the difference in brake fluid pressure between the left and right braking wheels. By applying the vehicle speed dependent constant interpolation processing of the present invention to these vehicles, the control target values (for example, the target yaw rate, the target lateral speed, etc.) do not fluctuate rapidly, and more stable vehicle motion control is achieved. Can be.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a basic configuration in a first embodiment.
FIG. 2 is a block diagram illustrating a configuration of a steering controller according to the first embodiment.
FIG. 3 is a block diagram illustrating a configuration of a target value generation unit according to the first embodiment.
FIG. 4 is a flowchart showing steering control in the first embodiment.
FIG. 5 is a flowchart illustrating an interpolation calculation process of a vehicle speed dependent constant in the first embodiment.
FIG. 6 is a vehicle speed-yaw rate gain map in the first embodiment.
FIG. 7 is an enlarged view of a vehicle speed-yaw rate gain map.
FIG. 8 is an explanatory diagram illustrating an interpolation calculation process of a vehicle speed dependent constant in the first embodiment.
[Explanation of symbols]
1L, 1R Front wheel 2L, 2R Rear wheel 3 Rear wheel steering actuator 4 Control device 8 Tie rod 11 Drive motor 14 Steering angle sensor 16 Vehicle speed sensor 17 Rear wheel steering angle sensor 41 Vehicle motion target value setting unit 42 Rear wheel steering angle command value calculation Unit 43 rear wheel steering angle servo calculation unit

Claims (1)

Steering wheel steering angle detecting means for detecting a steering wheel steering angle;
Vehicle speed detecting means for detecting a vehicle speed;
Rear wheel steering angle applying means for applying a rear wheel steering angle of the vehicle,
Rear wheel steering angle detection means for detecting a rear wheel steering angle,
Based on the detected steering angle, the detected vehicle speed, and a vehicle speed dependent constant set in advance as a map for each vehicle speed, a vehicle motion target value for allowing a response characteristic relating to a plane behavior of the vehicle to become a predetermined response characteristic. Vehicle motion target value calculating means for calculating
A rear wheel steering angle command value calculating means for calculating a rear wheel steering angle command value required to realize the vehicle motion target value,
Servo calculating means for providing a control signal to the rear wheel steering angle applying means so that the detected rear wheel steering angle matches the rear wheel steering angle command value;
In the vehicle motion control device provided with
The vehicle motion target value calculating means includes a two-wheel steering vehicle speed dependent constant calculating unit for calculating a vehicle speed dependent constant based on vehicle parameters during two-wheel steering, and a calculated two-wheel steering vehicle speed dependent constant and A vehicle motion control device, comprising: an interpolation operation unit that interpolates the vehicle speed dependent constant based on a vehicle speed dependent constant set as a map.

Images