JP2861571B2 - Vehicle steering angle control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering angle control device for improving the operability of a vehicle.

[0002]

2. Description of the Related Art As a steering angle control device for a vehicle, for example, a steering angle control as disclosed in Japanese Patent Application Laid-Open No. 61-67665 has been proposed by the present applicant. In the above-described technology, for example, in the case of rear wheel steering angle control, a traveling state is determined from a vehicle speed, a steering angle, and the like, and a target yaw rate as a controlled amount related to a plane motion of a vehicle to be aimed is determined from the traveling state. (Behavior target value), and the rear wheel steering angle required to make the generated yaw rate the target value is calculated by the equation of motion (vehicle model) based on vehicle specifications including wheel cornering power. The auxiliary steering of the rear wheels by the calculated steering angle is performed so that the behavior of the vehicle is as intended by the behavior target value. According to this, compared to the case of 2WS car,
It can contribute to adding new vehicle performance to maneuverability and stability.

[0003]

However, in such a steering angle control, if the wheel cornering power is assumed to be constant irrespective of the wheel side slip angle, the calculation of the auxiliary steering angle of the rear wheel as the control wheel is performed. Depending on the vehicle speed, the magnitude of the steering angle, the control area, etc., a deviation occurs between the actual cornering power of the wheels and the cornering power in the vehicle model, making it difficult to match the generated yaw rate to the target yaw rate. May be. In particular, at the time of a high-speed and large steering angle input in which the sideslip angle of the wheel is large, the cornering powers do not match, resulting in improper setting of the target yaw rate, resulting in an unrealistic value. In such a case, the generated yaw rate cannot be matched, and it is difficult to obtain a sufficient control effect. Therefore, for example, when the steering angle control is to be performed even in a region where the vehicle speed is 150 km / h and the steering angle is about 60 deg, there is a limit in that sense, and there is room for improvement.

An object of the present invention is to improve the above-mentioned object, and to further improve the controllability even in a region at a high speed and a large steering angle where the wheel side slip angle is large, and to expand the control region. An object of the present invention is to provide a vehicle steering angle control device.

[0005]

According to the present invention, there is provided the following vehicle steering angle control device. In a vehicle capable of assisting steering of at least one of the front wheels or the rear wheels and controlling the control steering angle to be equal to a target value by the control means, a steering angle detection means for detecting a steering angle of the vehicle; Speed detection means for detecting the front-rear direction speed, wheel side slip angle calculation means for calculating the sideslip angles of the front wheels and rear wheels of the running vehicle, and according to the sideslip angles of the front and rear wheels calculated by the sideslip angle calculation means. Means for estimating or correcting a value corresponding to the cornering power of the wheel, and a non-linear variable which is set in advance according to the vehicle specifications and the equation of motion and which varies according to the estimated or corrected value corresponding to the cornering power. Target setting means for setting target values of a steady-state characteristic and a transient characteristic of a controlled variable relating to the motion of the vehicle based on a vehicle model and detection values of the steering angle detection means and the speed detection means. A control obtained by giving the steering angle detection value, the speed detection value, and a linear steady controlled amount calculated from a linear vehicle model set by vehicle specifications and a motion equation to the nonlinear vehicle model. When the steady steering angle of the wheel is equal to or less than a predetermined threshold value, the steady value calculated from the linear vehicle model is set as the target steady value, and when it exceeds the threshold value, the steady value calculated from the nonlinear vehicle model is calculated. A vehicle motion target setting unit that sets a target steady value, and an auxiliary steering angle necessary for realizing the motion target value set by the vehicle motion target setting unit in a vehicle to be controlled by calculation based on the nonlinear vehicle model. A vehicle steering angle control device, comprising: a target auxiliary steering angle calculating unit that calculates and sets a target value, and at least one steering angle of a front wheel or a rear wheel can be assisted by steering. Yo In a vehicle that controls so that the control steering angle coincides with a target value, a steering angle detection unit that detects a steering angle of the vehicle, a speed detection unit that detects a longitudinal speed of the vehicle, and a vehicle specification and a motion equation in advance. A linear vehicle model to be set, and target setting means for setting target values of a steady-state characteristic and a transient characteristic of a controlled variable related to the motion of the vehicle based on the detection values of the steering angle detection means and the speed detection means, The control wheels are controlled by the non-linear vehicle model so that the target steady-state values calculated for the steering angle from both the non-linear vehicle model and the linear model considering the cornering force characteristics with respect to the tire sideslip angle are equal. Vehicle motion target setting means for obtaining a steady value obtained by inputting the steady steering angle and the steering angle to a linear vehicle model, and setting a steady value obtained as a target value. Target auxiliary steering angle calculating means for calculating an auxiliary steering angle required for realizing the motion target value set by the target setting means in the vehicle to be controlled by the calculation based on the linear vehicle model and obtaining the target value. A steering angle control device for a vehicle, comprising:

[0006]

In a vehicle capable of assisting steering of at least one of the front wheels or the rear wheels and controlling the control steering angle to be equal to a target value by the control means, a steering angle detecting means for detecting the steering angle of the vehicle; Speed detecting means for detecting the front-rear direction speed of the vehicle, side slip angle calculating means for calculating the sideslip angles of the front and rear wheels of the running vehicle, and front and rear wheelslip calculated by the sideslip angle calculating means. Means for estimating or correcting a value corresponding to the cornering power of the wheel according to the angle, and presetting by vehicle specifications and equations of motion;
And a vehicle model that varies in accordance with the estimated or corrected cornering power equivalent value, and a steady-state characteristic and an excessive characteristic of a controlled variable related to vehicle motion based on the detection values of the steering angle detection means and the speed detection means. Vehicle motion target setting means for setting a target value of the characteristic, wherein a value constantly generated when the steering angle detection value and the speed detection value are given to the vehicle model as a target steady value; Target auxiliary steering angle calculating means for calculating an auxiliary steering angle necessary for realizing the motion target value set by the vehicle motion target setting means in the vehicle to be controlled by a calculation based on the vehicle model and setting it as a target value In the steering angle control of the vehicle steering angle control device, the vehicle includes a wheel side slip angle calculation unit that calculates a side slip angle of a front wheel and a rear wheel of a running vehicle; ring Means for estimating or correcting the value corresponding to the cornering power of the wheel in accordance with the side slip angle, according to the estimated or corrected value corresponding to the cornering power which has been previously set by the vehicle specifications and the equation of motion. A vehicle motion target setting means for setting a target value of a steady-state characteristic and a transient characteristic of a controlled variable relating to the movement of the vehicle based on a variable vehicle model, a detection value of a steering angle detection means and a detection value of a speed detection means, The steering angle calculating means calculates an auxiliary steering angle necessary for realizing the movement target value set by the vehicle movement target setting means in the vehicle to be controlled by calculation based on the vehicle model, and calculates this as a command target value. However, in this case, the vehicle motion target setting means sets a value which constantly occurs when the steering angle detection value and the speed detection value are given to the vehicle model as a target steady value. As a result, even at a high speed and a large steering angle where the wheel sideslip angle becomes large, the target value of the controlled variable related to the motion of the vehicle becomes a realistic value,
As a result, overshoot does not occur in the generated value, and the vehicle maneuverability and stability can be improved as compared with a vehicle that does not use this control, and the control region can be further expanded. The invention is based on this.

In the case of claim 1, similarly, means for calculating the side slip angle of the wheel, means for estimating or correcting a value corresponding to the cornering power of the wheel, which are previously set by vehicle specifications and equations of motion, and A command target value is set by a non-linear vehicle model, a vehicle motion target setting means, and a target auxiliary steering angle calculation means, which are variable according to the estimated or corrected cornering power equivalent value. The motion target setting means obtains the nonlinear vehicle model by providing a steering angle detection value, a speed detection value, and a linear steady controlled amount calculated from a linear vehicle model set by vehicle specifications and a motion equation. When the steady steering angle of the controlled wheel is less than or equal to a predetermined threshold, the steady value calculated from the linear vehicle model is set as the target steady value. The steady-state value calculated from the linear vehicle model a target steady-state value. Thereby, even in this case, even at a high speed and a large steering angle where the wheel sideslip angle is large, the controlled amount relating to the vehicle motion can be made to match the target value better than that of the vehicle not employing this control. Vehicle maneuverability and stability can be improved, and the control area can be further expanded.

According to the second aspect of the present invention, the steady-state characteristic of the controlled variable related to the vehicle motion based on the linear vehicle model set in advance by the vehicle specifications and the equation of motion, and the detection values of the steering angle detecting means and the speed detecting means. And a vehicle motion target setting means for setting a target value of the transient characteristic, the target auxiliary steering angle calculating means realizing the motion target value set by the vehicle motion target setting means in a vehicle to be controlled. The required auxiliary steering angle is calculated by calculation based on the vehicle model and is used as a command target value. In this case, the cornering force characteristics with respect to the side slip angle of the tire are considered in advance in setting the vehicle motion target. The control wheels of the non-linear vehicle model are controlled so that the target steady-state values calculated for the steering angle from both the non-linear vehicle model and the linear model are equal. Seeking normal steering angle, the steady-state value obtained by inputting the steering angle and the constant steering angle linearly vehicle model and the target value. As a result, even at high speeds and large steering angles where the wheel sideslip angle is large, the steady-state characteristics can be improved as compared with a vehicle that does not employ this control, so that the vehicle controllability and stability can be similarly improved and the control region can be further improved. Enlargement is possible, and it is possible to realize the above even if a linear vehicle model is used for steering angle calculation.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows an embodiment of the steering angle control device according to the present invention. An applicable vehicle steering angle control system includes auxiliary steering means capable of assisting the steering angle of front wheels and / or rear wheels, and auxiliary steering control means capable of controlling the steering angle of the auxiliary steering means. The auxiliary steering control means may be based on a system for controlling the target auxiliary steering angle so that the target auxiliary steering angle and the steering angle of the auxiliary steering means coincide with each other. Here, a case where the present invention is applied to a steering angle control system for steering rear wheels will be described.

In FIG. 1, reference numerals 20L and 20R denote left and right rear wheels, respectively.
The front wheels not shown in FIG. 1 can be steered by a steering wheel 21 via a steering gear. The front wheel steering angle is represented by θ / N, where θ is the steering wheel steering angle and N is the steering gear ratio.

Here, the rear wheel steering angle control system has a rear wheel steering hydraulic cylinder 22 as an actuator for rear wheel steering, thereby enabling the rear wheels 20L and 20R to be steered. The hydraulic cylinder 22 is connected to a pressure source via a pressure servo valve 23 as a control valve. The pressure source is provided with an oil pump (rear wheel steering circulation pump) 25 driven by an engine 24 as a hydraulic pressure source for the cylinder 22. The pump draws in and discharges the operating oil of an oil reservoir (rear wheel steering reservoir) 26, regulates the discharged oil by an unload valve 27, and accumulates the accumulated oil (rear wheel steering accumulator). ) 28. The pressure servo valve 23 is interposed between the hydraulic supply passage 29 and the drain passage 30 of the pressure source and the chambers 22L and 22R of the hydraulic cylinder 22.

[0012] Pressure support - ball valve 23, the difference in the steering angle control - rear wheel for detecting click, i.e. the rear wheel steering angle (actual steering angle) [delta] _r - constitute a volume-based, therefore, stroke of the cylinder 22 A steering angle sensor 31 is provided so that a rear wheel steering angle value indicated by a feedback signal from the sensor matches a calculated value (target rear wheel steering angle) in a rear wheel target steering angle calculation method described later. Control the valve; That is, when the solenoid is OFF, the pressure servo valve 23 is at the position shown in the drawing, and the cylinder chambers 22L and 22R are disconnected from the supply passage 29 and the drain passage 30 to prohibit the stroke of the cylinder 22 and the rear wheel steering angle. Hold. Further, when the pressure servo valve 23 is turned on by a current in one direction, it is in the port position shown in the upper side, and the supply path 29
When the rear wheel is turned to the left by turning the rear wheel left and turned ON by the current in the other direction, the port position shown in the lower side is reached, and the pressure in the supply passage 29 is supplied to the cylinder chamber 22R. To steer the rear wheels to the right. When the rear wheel steering angle detected by the rear wheel steering angle sensor 31 coincides with the above-mentioned calculated value, the servo valve 23 is turned off to maintain the rear wheel steering angle.

The above control of the pressure servo valve 23 is performed by a controller 40, which inputs a signal from a steering angle sensor 3 for detecting a steering angle and a signal from a vehicle speed sensor 4 for detecting a vehicle speed. At the same time, a signal from the rear wheel steering angle sensor 31 is input. The controller, when realizing the motion target value set by the steering angle input and the vehicle speed by controlling the rear wheel steering angle, sets the vehicle motion target value based on the detected steering angle and the detected vehicle speed value as the vehicle motion target value. The auxiliary steering amount of the rear wheels required to achieve the set target value in the vehicle to be controlled is calculated by calculation based on the vehicle model.

In this case, the controller first calculates the wheel side slip angle of the running vehicle as a vehicle model set in advance based on the vehicle specifications and the equation of motion, and calculates the wheel side slip angle in accordance with the calculated side slip angle. Cornering power
A vehicle model that estimates or corrects a value corresponding to the vehicle model and that varies according to the estimated or corrected cornering power-equivalent value is used. A value which constantly occurs when the detected steering angle value and the detected vehicle speed value are given is set as a target steady value. In the above, the movement target value of the vehicle can be the yaw rate.

FIG. 2 shows a configuration of a control system represented as a functional block diagram, wherein 1a denotes a vehicle, and 2a denotes an auxiliary steering mechanism (here, a rear wheel steering mechanism). The auxiliary steering mechanism 2a is a hydraulic cylinder 2 in the system shown in FIG.
2. It includes a servo valve 23. In this embodiment, the steering state detecting means 3a for detecting the steering state of the vehicle, and the speed detecting unit 4a for detecting the longitudinal direction of the vehicle are configured to include the corresponding sensors 3, 4 and a part of the controller 40, respectively. You. Further, here, the controller 40 includes a vehicle motion target setting section 5a as a target yaw rate setting section and a rear wheel for realizing a motion target value (yaw rate target value) set by the setting section. Each function of the steering angle calculation unit 6a for calculating the steering angle is provided.

The target setting section 5a sets target values of the steady-state characteristics and the transient characteristics of the vehicle using a reference model. Specifically, the steady gain (here, the yaw rate gain in the reference model) and the transient response characteristic are set based on the detection values of the detection units 3a and 4a. In this case, the cornering power of the reference model is set. Correct and set the characteristics based on the sideslip angle of the tire (wheel).

The steering angle calculation unit 6a, when following this control example,
Wheel skid angle calculating means for calculating the skid angles of the front and rear wheels of the running vehicle, and cornering power of the wheels according to the skid angles of the front and rear wheels calculated by the skid angle calculating means.
Estimating means for estimating or correcting a value corresponding to a vehicle model and a target setting which are set in advance by vehicle specifications and equations of motion, and which vary according to a cornering power equivalent value estimated (corrected) by the estimating means. The target auxiliary steering angle calculating means for calculating the rear wheel auxiliary steering angle (target auxiliary steering angle) necessary for realizing the target yaw rate set by the part 5a by the own vehicle by the calculation based on the vehicle model. Calculate the control steering angle of the wheel. (In another example, the steering angle calculation unit may perform the rear wheel calculation by a calculation based on a vehicle model (linear vehicle model) set in advance by vehicle specifications and equations of motion instead of the above. It is based on the method of calculating the auxiliary steering angle).

As described above, in this embodiment, the steering angle calculating section 6a can calculate the wheel sideslip angles of the front and rear wheels, and the wheel cornering power of the model can be varied according to the relationship with the sideslip angles. The vehicle model (non-linear model) is used for steering angle calculation. Further, in this case, regarding the setting of the target yaw rate applied to the calculation by the steering angle calculation unit 6a, the yaw rate that is constantly generated by giving the steering angle and the vehicle speed to the vehicle model is set to the target yaw rate. -Set as late.

Hereinafter, referring to FIGS. 3 to 5, the target yaw rate (d / dt) in the control block diagram shown in FIG.
The method of setting φ, the method of calculating the target rear wheel steering angle value, and the like will be specifically described, respectively. These can be performed by the following calculations.

First, prior to the above description, the motion of the vehicle is considered as two degrees of freedom in the yawing and lateral directions shown in FIG. 3, and the equation of motion will be described as follows. It is to be noted that the drawing is an explanatory diagram of a vehicle motion model (linear two-degree-of-freedom vehicle model) having two degrees of freedom in the yawing and lateral directions.
3 and the corresponding symbols in the following formulas,
Each means the following.

[Table 1] M: vehicle weight I _Z: vehicle Yo - inertia mode - Instrument C _f: front wheel co - Naringufo - scan C _r: Kowako - Naringufo - scan L _f: between the center of gravity of the vehicle - the front axle distance L _r: Distance between the center of gravity of the vehicle and the rear axle V _x : Vehicle longitudinal speed (vehicle speed) V _y : Vehicle lateral speed (lateral speed) L: L _f + L _r

Equations of motion relating to the yawing and lateral directions of the vehicle are represented by the following (1),
It is known that it can be expressed by equation (2).

[Equation 1] I _Z · (d ² / dt ² ) φ (t) = C _f · L _f − C _r · L _r --- (1)

[Equation 2] M · (d / dt) V _y (t) = 2 (C _f + C _r ) −M · V _x (t) · (d / dt) φ --- (2) where C _The front wheel and rear wheel cornering forces of _f and C _r are respectively determined by using a front wheel cornering power K _f , a rear wheel cornering power K _r , a front wheel side slip angle β _f , and a rear wheel side slip angle β _r . It can be expressed by the following equation.

[Equation 3] C _f = K _f · β _f --- (3)

C _r = K _r · β _r --- (4) The front and rear wheel sideslip angles β _f and β _r are quantities defined by the following equations.

Β _f = θ (t) / N− (V _y + L _f · (d / dt) φ) / V _x (t) --- (5)

(6) β _r = δ _r (t) − (V _y −L _r · (d / dt) φ) / V _x (t) --- (6)

Here, by substituting the above equations (3) to (6) into equations (1) and (2) and considering the differential equation with respect to the yaw rate (d / dt) φ and the lateral velocity V _y , Equations (7) and (8) can be expressed.

(D ² / dt ² ) φ (t) = a ₁₁ (d / dt) φ (t) + a ₁₂ V _y (t) + b _f1 θ (t) + _br 1δ _r (t) − -(7)

Equation 8] _{(d / dt) V y (} t) = a 21 (d / dt) φ (t) + a 22 V y (t) + b f2 θ (t) + b r2 δ r (t) - -(8) Here, each coefficient in the above equations represents the following.

## EQU9 ## a ₁₁ = ₋₂ · (K _f · L _f ² + K _r · L _r ² ) / (I _Z · V _x ) --- (9)

Equation 10] _{a 12 = - 2 · (K} f · L f - K r · L r) / (I Z · V x) --- (10)

[Number 11] _{a 21 = - 2 · (K} f · L f - K r · L r) / (M · V x) - V x --- (11)

[Number 12] _{a 22 = - 2 · (K} f + K r) / (M · V x) --- (12)

[Equation 13] b _f1 = 2 ・ K _f・ L _f / (I _Z・ N) --- (13)

[ _Equation 14] b _f2 = 2 · K _f / (M · N) --- (14)

[ _Equation 15] b _r1 = −2 · K _r · L _r / I _Z --- (15)

## _EQU16 ## b _r2 = 2 · K _r / M --- (16) Thus, the equation of motion in the yaw and lateral directions of the vehicle is expressed by a linear two-degree-of-freedom model, and the derivative of the yaw rate and the lateral velocity is obtained. By rearranging the equations, the above (7) and
(8) It can be expressed like the expression.

Here, the yaw rate with respect to the steering angle input,
Consider the characteristics of lateral speed. From the above equations (7) and (8), first, the relationship of the generated yaw rate (d / dt) φ (t) with respect to the steering angle input θ (t) can be expressed by the following equation (17) when the differential operator S is used. ) Can be expressed as

Equation 17] (d / dt) φ (S ) / θ (S) = {b f1 S + (a 12 b f2 -a 22 b f1)} / {S 2 - (a 11 + a 22) S + ( a ₁₁ a ₂₂ −a ₁₂ a ₂₁ )｝ --- (17) On the other hand, similarly, the generated lateral velocity V with respect to the steering angle input θ (t)
The relation of _y (t) can be expressed by the following equation (18) using the differential operator S.

Equation 18] _{V y (S) / θ (} S) = {b f2 S + (a 21 b f1 -a 11 b f2)} / {S 2 - (a 11 + a 22) S + (a 11 a 22 −a ₁₂ a ₂₁ )｝ --- (18) Here, looking at the above equations (17) and (18), each of these equations has the form of (primary) / (secondary), and the vehicle speed V _x becomes large as occurs with respect to the steering angle input Yo - late (d / dt) φ (t ) and the lateral velocity V _y (t) becomes oscillatory, vehicle controllability, it can be seen that the stability is deteriorated.

Therefore, for example, the target yaw rate (d / dt) φ _r
If (t) is a first-order lag system with no over / undershoot for the steering angle input and the steady value is set to be equal to the normal (base vehicle), it is defined as follows: stability factor a, and constant yaw is defined by the following - by using a rate gain H _0, the target yaw - late
(d / dt) φ _r (t) is defined by the following equation (19).

(D / dt) φ _r (t) = H ₀ θ (t) / (1 + τS) --- (19) τ: time constant

[Number 20] _{H 0 = V x / (1} + A · V x 2) LN --- (20)

A = −M (L _f K _f0 −L _r K _r0 ) / (2L ² K _f0 K _r0 ) --- (21) The target yaw rate (d / dt) φ _r (t)
_Treats its K _f , K _r (in equation (21)) as a constant (linear region) .Therefore, the steady-state yaw gain H _{0 in} equation (20) also becomes a constant value if the vehicle speed V _x is constant. Therefore, the linear yaw rate is proportional to the steering angle input.

However, if the wheel cornering power is constant irrespective of the wheel sideslip angle, on the other hand, the target value may become unrealistic, such as when a large steering angle is input with a large sideslip angle. -The rate cannot be matched, resulting in a case where the vehicle behavior tends to be unstable, and in that sense the control region is limited. Therefore, in this control, the target yaw rate (d / dt) φ _r (t) is set to the same value for the primary delay system, and the steady-state value is set to the cornering power.
It is set to be equal to the 2WS characteristics of the base vehicle, taking into account the side slip angle dependence of the vehicle.

Hereinafter, a method of calculating the target yaw rate will be described. First, the steady-state characteristics of the 2WS are obtained from the above two-degree-of-freedom equations of motion, in the equations (1), (2), (5), and (6), as (d ² / dt ² ) φ
If (t), (d / dt) V _y (t) and δ _r (t) are each set to zero,
These equations are as follows.

[Equation 22] C _f · L _f = C _r · L _r --- (1A)

(23) M · V _x (t) · (d / dt) φ (t) = 2 (C _f + C _r ) --- (2A)

Equation 24] _{β f = θ / N- (V} y + L f · (d / dt) φ (t) / V x (t) --- (5A)

_Equation 25 β _r = − (V _y0 − L _r · (d / dt) φ (t) / V _x (t) --- (6A)

The front and rear wheel cornering powers K _f , K _f
The dependence of _{r on} the wheel sideslip angle can be explained with reference to FIG.
In general, the wheel sideslip angle and the cornering force have the characteristics represented in the figure, and the cornering power tends to decrease as the sideslip angle increases. Therefore, the front and rear wheel cornering powers K _f , K _r are defined as wheel side slip angles β _f ,
Handling as beta _r dependent variables, the target steady-state characteristics, Such as wheel co according to the wheel side slip angle - Naringupawa - considering that the changes constantly occurring Yo - computing the rate. For example, as shown in the characteristics shown in FIGS. 5 (a) and 5 (b), when the front wheel side slip angle β _f and the rear wheel side slip angle β _{r for} the front wheel and the rear wheel, respectively, the following equation (22) is obtained. ,
Approximate as in equation (23).

## _EQU26 ## C _f = K _fi · β _f −C _fi (i = 0,1,2) --- (22)

C _r = K _rj · β _r −C _rj (j = 0,1,2) --- (23) where, in the above approximation, the relation between β _f , K _fi , and C _fi , β _r , K _rj , and C _rj, the constants shown in FIGS. (A) and (b) are taken as follows.

[0028]

28 ≦ 0 ≦ | β _f | ≦ β _f1 K _fi = K _f0 , C _fi = 0 --- (24a)

(29) β _f1 <| β _f | ≦ β _f2 K _fi = K _f1 , C _fi = C _f1 --- (24b) (when β _f <0, C _fi = -C _f1 )

[ _Equation 30] β _f2 <| β _f | K _fi = K _f2 , C _fi = C _f2 --- (24c) (When β _f <0, C _fi = -C _f2 )

31 ≦ 0 ≦ | β _r | ≦ β _r1 K _rj = K _r0 , C _ri = 0 --- (24d)

Β _r1 <| β _r | ≦ β _r2 K _rj = K _r1 , C _ri = C _r1 --- (24e) (When β _r <0, C _ri = -C _r1 )

Equation 33] _{β r2 <| β r | K} rj = K r2, C ri = C r2 --- (24f) (β r < When 0, C _ri = -C _r2) Incidentally, the magnitude relationship of the constants Is a value satisfying the following conditions.

[ _Expression 34] K _f0 > K _f1 > K _f2 > 0 K _r0 > K _r1 > K _r2 > 0

[ _Equation 35] C _f2 > C _f1 > 0 C _r2 > C _r1 > 0

[ _Expression 36] β _f2 > β _f1 > 0 β _r2 > β _r1 > 0

From the cornering forces C _f and C _r calculated by the equations (22) and (23), the front and rear wheel cornering power is calculated.
K _f and K _r are calculated by the following equations (25) and (26).

(25) Equation K _f = C _f / β _f (β _f ≠ 0) --- (25a)

[Number 38] _{K f = K f0 (β f} = 0) --- (25b)

(26) Equation K _r = C _r / β _r (β _r ≠ 0) --- (26a)

[Number 40] _{K r = K r0 (β r} = 0) --- (26b)

Next, a method of calculating the target steady-state yaw rate will be described. First, a steady side slip angle is determined based on the above equations (1A), (2A), (5A), and (6A). In light of the formulas (1A) and (2A), (d / d
t) Let φ ₀ be the target steady-state yaw rate,

(M · V _x (t) · (d / dt) φ ₀ ) / 2 = (1 + L _f / L _r ) C _r is obtained. Therefore, (d / dt) φ ₀ is obtained from the above equation. Is expressed by the following equation.

(D / dt) φ ₀ = 2 (1 + p) C _f / MV _x --- (27) where p = L _f / L _r

On the other hand, in light of the equation (5A)-(6A),

(43) β _f −β _r = θ / N−L (d / dt) φ ₀ / V _x --− (28) ) By substituting φ ₀ and focusing on the front wheel cornering force C _f , the following is obtained.

Equation 44] _{β f -β r = θ / N-} 2L (1 + p) C f / MV x 2 d

４５C _f = k ₀ · θ / N- (β _f -β _r ) --- (29) where k ₀ = MV _x ² / 2L (1 + p)

[0032] In addition, Kowako - Naringufo - scan C _r is,
From the above (1A) and the above equation (29), the following equation is obtained.

C _r = p C _f = pk ₀ · θ / N− (β _f −β _r ) --- (30) Therefore, in these equations (29) and (30), By summarizing certain equations (23) and (24), the following determinant is obtained.

[0033]

[Equation 47]

[Equation 48]

From the above equation (31), β _f and β _r obtained by sequentially giving K _fi , C _fi , K _rj and C _rj are values satisfying the existence conditions defined by the equations (24a) to (24f). Select If β _f and β _r are obtained, stationary cornering forces C _f and C _r are obtained from the above equations (22) and (23), and furthermore, the steady generation rate (d / dt) is obtained from the equation (27). ) φ ₀ is obtained. Then, the target yaw rate is calculated as follows:
Since it is set to a first-order lag system with no data, it can be expressed as the following equation (32).

(D / dt) φ _r (t) = (d / dt) φ ₀ (t) / (1 + τS) --- (32) where (19) ), (D / d
t) φ ₀ is the steady-state yaw rate according to the above-mentioned equation (27). In this way, the target yaw rate can be set so that its steady value becomes equal to the 2WS characteristic of the base vehicle, taking into account that the cornering power changes according to the wheel side slip angle.

Further, using the rear wheel steering angle δ _r (t), the generated yaw rate (d / dt) φ (t) of the vehicle is calculated using the target yaw rate (d)
/ dt) φ _r (t). Above (3
By transforming equation (2), the differential value of the target yaw rate (d ² / dt
² ) φ _r (t) (yaw angular acceleration) is obtained by the following equation (33).

(D ² / dt ² ) φ _r (t) = ｛(d / dt) φ ₀ (t) − (d / dt) φ _r (t)｝ / τ --- (33) , the steering angle theta (t), the rear wheel steering angle [delta] _r (t) of 2 input by generating Yo - late (d / dt) φ (t ) is the target yaw - rate value (d
/ dt) φ _r (t), their differential values (d ² / dt ² ) φ (t) and (d ² / dt ² ) φ _r (t) also match, respectively. Therefore, (d / dt) φ _r (t) = (d / dt) φ (t) and (d ² / dt ² ) φ _r
(t) = (d ² / dt ² ) φ (t), and (d / dt) φ _r (t) =
(d / dt) φ (t ) the vehicle when the true lateral velocity V _y a (t)
If it is defined as V _yr (t), the following equations (34) and (35) are obtained from the equations (7) and (8) of the above equation of motion.

(D ² / dt ² ) φ _r (t) = a ₁₁ (d / dt) φ _r (t) + a ₁₂ V _yr (t) + b _f1 θ (t) + b _r1 δ _r (t ) --- (34)

Equation 52] _{(d / dt) V yr (} t) = a 21 (d / dt) φ r (t) + a 22 V yr (t) + b f2 θ (t) + b r2 δ r (t) - -(35) Accordingly, δ _r (t) is obtained from the following equation (36).

Δ _r (t) = ｛(d ² / dt ² ) φ _r (t) −a ₁₁ (d / dt) φ _r (t) −a ₁₂ V _yr (t) −b _f1 θ (t ｝ / _Br1 --- (36) By inputting the rear wheel steering angle obtained by the above equation (36), the generated yaw rate of the vehicle can be made to coincide with the target yaw rate.

Accordingly, the calculation of the target rear wheel steering angle by this control is performed as described above, and the rear wheel steering angle control is executed using this as a target value.

The calculation necessary for calculating the target rear wheel steering angle described based on the above equations (1) to (36) can be performed by the microcomputer in the controller 40. For example, FIG.
The target rear wheel steering angle is calculated according to the flowchart shown in FIG. This program is executed every fixed time ΔT, and in order to cope with the processing by the microcomputer, instead of the continuous operation (t) used in the above description,
In the following program processing, a symbol with (n) indicating that it is a discrete operation is used. Here, a value obtained by adding (n-1) to the corresponding calculated value represents a previous value with respect to the current value (n). Hereinafter, processing in the flowchart,
Description will be given while corresponding to the above-described expressions.

In FIG. 6, first, in step 200,
The vehicle speed V _x (n) and the steering angle θ are determined based on the outputs from the sensors 3 and 4.
Read (n). Next, in steps 201 to 203, a wheel cornering power calculation is executed. That is, in step 201, the near-end formula of the cornering force (the above-mentioned (22)) is obtained from the previous calculated values of the wheel side slip angles of the front and rear wheels (calculated in step 209 in FIG. 8), which are obtained as described later. , (23)), select the coefficients K _fi, C _fi , K _rj , and C _rj . Specifically, according to the previous values β _f (n-1) _and β _r (n-1), it is determined whether the values fall into any of the regions in the approximation characteristic of FIG. 5 ((24a) To (24f)), the respective coefficients are determined.

In step 202, the decision made in step 201 is made.
Based on the set coefficients, the front and rear wheels are calculated from the formulas (22) and (23).
Cornering force C_f(n)_, C_r(n) Calculate the value
You. Further, in step 203, the previous value β_f(n-1)_,β
_r(n-1) and calculated value C_f(n) _, C_r(n)
The calculation based on the equations (25) and (26) of
Cornering power K for front and rear wheels used in the calculation of_f(n)_,
 K_rCalculate (n).

Step 204 (FIG. 7) is based on the calculated K
_{f (n),} depending on the K _r (n), and corrects each coefficient of the vehicle model, K _f, using the respective calculated value _{K f (n), K r} (n) to K _r, also the vehicle speed V _{Using x} (n), calculations based on the above-mentioned equations (9) to (16) are performed, and coefficients a _{11 to} a ₂₂ , b _f1 to be applied to the target rear wheel steering angle calculation to be executed after step 207 described later. ~ B
Calculate _r2 .

Here, the above-mentioned calculated previous value β _f (n-1) _, β
A series of processes up to the values of K _f (n) _and K _r (n) based on _r (n-1) are performed using the vehicle model, including the process in the next target yaw rate calculation. And the relationship between the calculated sideslip angle and the sideslip angle and the cornering power preset independently for the front and rear wheels (in this example, FIG. 5)
Means that the cornering power of the vehicle model is corrected in accordance with the above equation, the steering angle and the vehicle speed are given to the vehicle model, and the constantly generated yaw rate is set as the target yaw rate.

That is, in the next step 205 (FIG. 7),
According to the above equations (27) and (31), the target steady-state yaw rate (d / dt) φ
₀Processing for calculating (n) is executed. The stationary yaw rate calculation
The output subroutine is shown in FIGS.
Step 300 is used when performing the calculation based on the above-mentioned equation (31).
Steps and steps for setting conditions for the existence range of the rear wheel sideslip angle
Step 311 calculates the front and rear wheels by performing the calculation based on the above equation (31).
Side slip angle β_f,β_rAnd the calculated value β_f,
β_rBy performing the calculations of the above equations (22) and (23) using
Steady cornering force C of rear wheel_f, C _rCalculate
Step 320 in FIG. 10
Side slip angle value β calculated in step 311_f,β_rBut on
Whether the existence condition assumed in step 300 is satisfied
This is the step of checking.

Step 300 comprises, for example, steps 301 to 305 as shown. The processing in step 301 uses the read vehicle speed V _x (n) to calculate β _{f and} β _r (step 311).
K _fi with computing the value p and the value k ₀ to be applied, to apply also the calculation (and C _f, C _r calculated) in the, C _fi, K
_{For rj} and C _rj , the first _loop selects K _f0 and K _r0 first and applies them (C _fi , C
_rj is 0). I = 0, j = 0 in step 301 means this. Similarly, in step 30
Steps 303 and 305 performed when the answer of each of steps 304 and 304 is NO. (Steps 302 to 305 are selected according to the determination results of steps 323 to 325 and 327 to 329 in FIG. 10) I = i + 1, j = j + 1 at
Is applied to K _fi , C _fi , K _rj , C _rj
In the description of the equations (22), (23), (24a) to (24f) and the approximation characteristics, the respective constants shown in FIGS. And apply it.

In step 311, the data obtained as described above is obtained.
P, k₀And K_fi, C_fi, K_rj, C_rj, And read
The side slip angle β using the steering angle θ (n)_f,β_rabout
Calculation, and here, the β_fvalue_,β_rBased on the value
K applied to the calculation_fi, C _fi, K_rj , C_rjIn response to,
According to the above equations (22) and (23), a steady corner of the front and rear wheels is obtained.
Ningforce C_f, C_rIs calculated. However
And the calculated C _fValue, C_rThe value is stored once
You.

Step 320 includes step 321 as shown.
Here, the constants β _f1, β _f2 , β _r1, set for the wheel sideslip angle in the approximation characteristics of Figs. 5 (a) and 5 (b)
Using β _r2 as a discrimination value, the calculated β _{f and} β _r values in step 311 are used to calculate K _fi , C _fi ,
A check is made to see if the values fall within the respective ranges of β _{f and} β _r in FIGS. _5A and _5B corresponding to K _rj and C _rj .

The β _{f and} β _r values obtained by giving K _fi , C _fi , K _rj and C _rj are obtained as values satisfying the existence conditions defined by the above equations (24a) to (24f). And the calculation β _f,
If the values of C _f and C _r are found in the corresponding relational expression using the β _r value, it is a stationary cornering force that can be applied in the next processing (step 331) (the equation (27) Based on
The cornering forces C _f and C _r that can be used to calculate (estimate) the steady-state yaw rate at θ (n) and V _x (n) can be obtained.

Therefore, in step 320, the condition is satisfied.
If it is determined that the
Calculated in and temporarily stored C_f, C_rValue to the next target steady state
-The next step is to apply the rate calculation process.
Proceed to the operation at step 330, if not satisfied
Returning to step 300, as already mentioned, K_fi,
C _fi, K_rj , C_rjSet other conditions for
Steps 311 and 320 are executed. In this process β_f,β_r
But also C_f, C_rIs newly calculated and β _f,β
_rIs determined to apply to the value within the existing range
Then, the processing proceeds to the next step 330 as in the above.

Proceeding to step 330 (FIG. 11),
Using the stationary cornering force C _f , C _r (C _f , C _r values determined according to the region of β _f, β _r and the size thereof) calculated in step 311 The above (27)
An operation based on the equation, that is, here, C _f · L _f = C _r ·
Relationship L _r (wherein (1A) type) of the following be represented using any of a (d / dt)
φ ₀ (n)

(D / dt) φ ₀ (n) = 2 (C _f + C _r ) / (M · V _x (n)) --- (41), and θ (n), V _The target steady-state yaw rate (d / dt) φ ₀ (n) for _x (n) is calculated (step 331). Further, the steering directionality is determined by the sign of θ (n) (step 33).
2), if θ (n) <0, this subroutine is terminated as it is, while if θ (n) <0, (d / dt) φ ₀ (n) is changed to − (d / dt) φ ₀
This is set to (n) (step 333), and this subroutine is terminated.

As described above, regarding the target steady-state characteristics of the target yaw rate, the above-mentioned values of C _f and C _r are used, and as a result, the wheel cornering power changes in accordance with the wheel side slip angle. The calculation of the yaw rate that occurs in a random manner is performed.

Returning to FIG. 7, in the next step 202, using (d / dt) φ ₀ (n) obtained above, the calculation based on the above equation (32) is performed, and the target yaw angular acceleration and the target yaw angular acceleration are calculated. Calculate the yaw rate. Specifically, the target yaw angular acceleration and the target yaw rate, respectively, are calculated as (d ² / dt ² ) φ _r (n) and (d / dt) φ _r (n), respectively.

(D ² / dt ² ) φ _r (n) = (1 / τ) ｛(d / dt) φ ₀ (n) − (d / dt) φ _r (n-1)｝ --- (42)

(D / dt) φ _r (n) = (d / dt) φ _r (n-1) + (d ² / dt ² ) φ _r (n) · ΔT --- (43) Shall be. The target yaw rate is the target yaw rate.
It is calculated by integrating the angular acceleration.In this case, the integration operation is performed by the discrete rectangular integration ((43)
Equation), which is approximated (this method is performed in the same manner even when similar processing is required thereafter).

In the next step 207 (FIG. 8), the above (35)
A differential value of lateral velocity (d / dt) V _yr (n) is calculated by an operation based on the equation, and a lateral velocity V _yr (n) is calculated by integration thereof.
In the following step 208, the target rear wheel steering angle δ _rm (n) is calculated so as to match the target yaw rate by the calculation based on the equation (36).
Is calculated. Specifically, these are defined in step 204
Using the coefficient values calculated in (i.e., each coefficient of the vehicle model corrected according to K _f (n) and K _r (n) obtained in the calculations in steps 201 to 203), the following is performed. I have.

(D / dt) V _yr (n) = a ₂₁ (d / dt) φ _r (n) + a ₂₂ V _yr (n−1) + b _f2 θ (n) + b _r2 δ _rm (n -1) --- (44)

V _yr (n) = V _yr (n−1) + (d / dt) V _yr (n) · ΔT --- (45)

Δ _rm (n) = ｛(d ² / dt ² ) φ _r (n) −a ₁₁ (d / dt) φ _r (n) −a ₁₂ V _yr (n) − b _f1 θ (n )｝ / B _r1 --- (46) Thus, the target rear wheel steering angle δ _rmFF (n) is set.

After the calculation of the target rear wheel steering angle δ _rm (n), in the present program example, the above-described step 20 is performed in the next calculation cycle.
The wheel sideslip angles used for the wheel cornering power calculation by 1 to 203 are given by the above formulas (5) and (6), and V _yr (n), δ _rm (n), and (d / dt) φ _r (n) ((45),
Using equations (46) and (43), the following equation is used.

Β _f (n) = θ (n) / N − ｛(V _yr (n) + L _f · (d / dt) φ _r (n)｝ / V _x (n) --- (47 )

Β _r (n) = δ _rm (n) − ｛(V _yr (n) −L _r · (d / dt) φ _r (n)｝ / V _x (n) --- (48)

Thus, in the system of FIG. 1, the controller 40 detects the steering angle sensor 31 based on the target rear wheel steering angle δ _rm (n) obtained by executing the flowcharts of FIGS. as wheel steering angle [delta] _r is matching the target value δ _rm (n), the pressure service - to control the ball valve 23.

According to the steering angle control as described above, it is set in advance according to the vehicle specification and the equation of motion to be controlled, and is made variable by an estimated value of the cornering power corresponding to the sideslip angle of the front and rear wheels. Using a vehicle model, a yaw rate that constantly occurs when a detected value of a steering angle and a vehicle speed is given can be set as a target yaw rate. Therefore, even at high speeds and large steering angles where the wheel sideslip angle is large, the target yaw
The late becomes a realistic value, and the generated value does not cause overshoot or the like, and the vehicle maneuverability and stability can be improved.

FIG. 12 shows a simulation calculation result showing an example of the control effect in the case of this control. FIG. 13 shows the target yaw rate defined by the above equations (19) to (21).
13 shows a comparative example obtained by a simulation calculation to compare the effect of the control method in the case of giving a late to control the rear wheel steering angle with FIG. In each case, the simulation conditions were as follows: vehicle speed V _x = 150 km / h, steering angle θ = 60
deg, lane change. In the comparative example, FIG.
3) As shown in (a) to (c), the target yaw rate is improperly set due to the running conditions of high speed and large steering angle as described above, and overshoot occurs in the generated yaw rate. Is
(Same (c)). On the other hand, in the case of this control,
As shown in FIGS. 12 (a) to 12 (c), the results when the control is performed based on the flowcharts 6 to 11 indicate that the overshoot is suppressed in the generated yaw rate. (
C)).

Thus, as shown in the above results,
According to this control, it is possible to further improve the vehicle maneuverability and stability as compared with the comparative example. The control area expands,
Even at a high speed and a large steering angle, the generated yaw rate of the vehicle can be made to coincide with the target value, and the behavior of the vehicle can be stabilized.

Next, another embodiment of the present invention will be described. Also in this embodiment, the cornering force characteristic is corrected based on the side slip angle of the tire so that the controlled value of the vehicle motion is matched with the target value of the vehicle motion during transient and steady conditions even at high speed and large steering angle where the side slip angle is large. In the same manner, the wheel side slip angle calculating means during running, and the estimation or correction of the value corresponding to the cornering power of the wheel according to the calculated side slip angle. Means, a vehicle model that varies according to the estimated (corrected) cornering power-equivalent value is used.However, the setting of the vehicle motion target value is as follows with respect to the method according to the above-described example. I do.
That is, a steering condition detection value, a speed detection value, and a linear vehicle model (a linear vehicle model set in advance by vehicle specifications and a motion equation) are calculated for a nonlinear vehicle model that varies according to the above-mentioned cornering power equivalent value. A steady rear wheel steering angle obtained by giving a linear steady controlled amount is introduced for setting a target value, and the steady rear wheel steering angle is compared with a predetermined threshold value.
When the threshold value is less than the threshold, a steady value calculated from the linear vehicle model is selected as the target steady value, and when the threshold value is exceeded, a steady value calculated from the nonlinear vehicle model is selected. The target value is set, and in the case of the present embodiment, the vehicle motion target value setting unit 5a in FIG. 2 has the above function.

Also in this case, the target movement value of the vehicle is the yaw rate, and the steady gain in the reference model is the yaw rate gain. Preferably, in the above, when the steady rear wheel steering angle exceeds the threshold value, the steady yaw rate generated when the rear wheel steering angle is set to the threshold value is set as the target steady value.

The setting of the target yaw rate in the case of this example is as follows. As already described, the vehicle maneuverability and stability are deteriorated according to the equations (17) and (18).
Therefore, for example, for the setting of the target yaw rate (d / dt) φ _r (t), a first-order lag system without over / undershoot is used, and the steady value is considered in consideration of the side slip angle dependence of the cornering power. After that, it is set as the 2WS characteristic of the base vehicle. In that case, this is done from the following viewpoints.

First, the steady side slip angles of the 4WS and 2WS vehicles are considered, and they are calculated from the above-described equation of motion with two degrees of freedom.
Since the differential term is set to zero since it is in a steady state, the equations (1) and (2) are as shown in the above-mentioned equations (1A) and (2A). "Steady side slip angle of 2WS" Now, regarding the steady side slip angle of 2WS, from the equations (1A) and (2A), as in the above example,
It is obtained _{M · V x · (d /} dt) φ 0/2 = (1+ L f / L r) C f
((d / dt) φ ₀ : steady-state yaw rate) Here, if the above equation is modified by focusing on C _f based on this relationship, the following is obtained.

C _f = k ₀₁ · (d / dt) φ ₀ / (1 + p) --- (50) where k ₀₁ = MV _x / 2, p = L _f / L _r

Further, also in this example, FIG. 5 and (2)
2), (23), (24a) to (24f) to apply the approximate characteristics as described in the equation, substituting the equation (50) into the equation (22),
The following equation summarizes the sideslip angle of the front wheel.

Β _f = ｛k ₀₁ · (d / dt) φ ₀ / (1 + p) −C _fi ｝ / K _fi --- (51) Also, the rear wheel sideslip angle is given by the above equation (51) and (1A), (2
From the expressions (2) and (23), the following expression (52) is obtained.

Β _r = (pK _fi · β _f + p C _fi −C _fj ) / K _rj = ｛pk ₀₁ · (d / dt) φ ₀ / (1 + p) − C _ri ｝ / K _fj --- (52) thus, the constant slip angle of 2WS is represented by the above formula that contains (d / dt) φ _0.

"Steady side slip angle of 4WS" Next, the steady side slip angle of 4WS is as follows. The steady side slip angle of 4WS is
Since the rear wheel steering angle is given as a known value, β _f and β _r are as follows, with Δ _r0 as the steady rear wheel steering angle, based on the above equations (5) and (6).

[Number 65] _{β f = θ (t) /} N - (V y + L f · (d / dt) φ 0 (t)) / V x (t) --- (5B)

Β _r = δ _r0 − (V _y −L _r · (d / dt) φ ₀ (t)) / V _x (t) --- (6B) where the difference ((5B ) Equation-(6B) Equation)
β _f −β _r can be expressed as follows.

Β _f −β _r = θ / N−δ _r0 − L (d / dt) φ ₀ / V _x --- (53) Further, the above equation (23) and the above equation (53) are _expressed by β _From the formulas arranged for _f , C _r becomes the following formula (54).

C _r = K _rj ｛β _f −θ / N + δ _r0 + L (d / dt) φ ₀ / V _x ｝ + C _rj --- (54)

Therefore, the above equation (54) and the above equations (2A) and (22) can be summarized as follows.

K ₀₁ · (d / dt) φ ₀ = (K _fi + K _rj ) β _f + (C _fi + C _rj ) − K _rj ｛θ / N−δ _r0 − L (d / dt) φ ₀ / V _x ｝

数 β _f = k ₀₁ (d / dt) φ ₀ -C _fi -C _rj + K _rj ｛θ / N -δ _r0 -L (d / dt) φ ₀ / V _x ｝ / (K _fi + K _rj ) --- (55)

Β _r = β _f − ｛θ / N−δ _r0 − L (d / dt) φ ₀ / V _x ｝ --- (56) Thus, the steady side slip angle of 4WS is obtained by the above (55), It is expressed by the relationship of equation (56). In the present embodiment, the target yaw rate is set by focusing on these relationships.

A specific method of calculating the target yaw rate to be set can be as follows. First, the vehicle speed, steering angle, and cornering power (linear value: K _f =
From K _f0 , K _r = K _r0 ), a linear stationary yaw rate is calculated as follows. That is, (d / dt) φ _L0 is a linear steady-state yaw rate, H ₀ is a steady-state yaw rate gain H ₀ , and A is a stability factor.

(D / dt) φ _L0 = H ₀ · θ --- (19)

H ₀ = V _x / ((1 + A · V _x ² ) LN) --- (20)

A = −M (L _f K _f0 − L _r K _r0 ) / (2L ² K _f0 K _r0 ) --- (21)

[0065] Thus, the steady yaw calculated - the late (51), (52) is applied to (d / dt) phi ₀ of equation determines the side slip angle of the front and rear wheels in accordance with Equation each as follows .

Equation 75] _{β f = {k 01 · (} d / dt) φ L0 / (1 + p) - C fi} / K fi --- (51A)

(76)_r= ｛Pk₀₁・ (D / dt) φ_L0/ (1 + p) -C_ri｝ / K_fj --- (52A) For the actual calculation (in the controller),
A), (52A)_fi, C _fi, K_fj, C_rjCalculated sequentially
Β_f, β_rAre defined by the equations (24a) to (24f).
Select each value (K, C, β) that satisfies the presence condition.
An example of the procedure is based on the method shown in FIGS.
May be used).

Further, by applying the sideslip angle values β _f and β _r obtained by the above equations (51A) and (52A) to the relation of the above equation (53), a steady rear wheel steering angle δ _r0 is calculated, The value of δ _r0 is a certain threshold (
δ _{r0 max} ) or less, β _f ,
Using β _r , K _fi , C _fi , K _fj , C _rj , the cornering force C
_f and _Cr (Equations (22) and (23)) are calculated. On the other hand, if the [delta] _r0 value exceeds its threshold, the a value [delta] _r0 = threshold (55), using (56) equation relationship, recalculated per slip angle to the next as.

(77) β _f = k ₀₁ (d / dt) φ _L0 -C _fi- C _rj + K _rj ｛θ / N-δ _r0- L (d / dt) φ _L0 / V _x V / (K _fi + K _rj ) --- (55A)

(78) β _r = β _f − ｛θ / N−δ _r0 − L (d / dt) φ _L0 / V _x ｝ --- (56A) In this case, the above (55A), (56A) The cornering forces C _f and C _r are determined from β _f and β _r recalculated by the equations.

Thus, in this example, the above procedure
C _f , C _r are obtained, and the C _f , C
_The yaw rate is calculated from the relationship between _r and the equation (2A), and this is set as the steady-state value of the target yaw rate by the following equation.

(D / dt) φ _rS (t) = 2 (C _f + C _r ) / (M · V _x (t)) --- (60) The target yaw rate (d / dt) φ _r (t) is set as shown in the following equation in order to set a first-order lag system having no over / undershoot with respect to the steady value of the equation.

(D / dt) φ _r (t) = (d / dt) φ _rS (t) / (1 + τS) --- (61) In this example, the target yaw rate is set in this manner.

FIGS. 14 to 16 show an example of the target rear wheel steering angle value calculation program including the target yaw rate setting processing described above. The calculation of the target rear wheel steering angle for making the generated yaw rate coincide with the set target yaw rate using the rear wheel steering angle is performed in the same manner as in the previous embodiment ((33) to (36). ) Formula), and the main part will be described below.

Referring to FIG. 14, first, at step 400, the vehicle speed V _x (n) and the steering angle θ (n) are read in the same manner as in the above-described example. From the original (L, N, A) and the read V _x (n) value, a steady-state yaw rate gain H ₀ based on the above equation (58) is calculated. Further, in step 402, the steady-state yaw rate gain is
Steady-state yaw rate (d / dt) φ _L0 from H ₀ value and reading θ (n) value
Calculate (n). Thus, V _x (n), θ linear steady Yo according to (n) - can be obtained late, then, is calculated from this linear steady sideslip angle and constant rear-wheel steering angle.

In step 403, the equations (51A) and (52A) are
Therefore, the steady-state yaw rate (d / dt) φ _L0Steady based on (n) value
Side slip angle β_f(n)_,β_r(n), and proceed to step 404.
And the steady rear wheel steering angle δ_r0Calculate (n).

Δ _r0 (n) = θ (n) / N − ｛L (d / dt) φ _L0 / V _x (n)｝ − (β _f (n) -β _r (n)) --- (71) In the next step 405 (FIG. 15), the absolute value of the steady rear wheel steering angle δ _r0 (n) calculated in
Check if it is less than _r0max (> 0), _δr0max If it is less than or equal to 408, the process directly proceeds to the processing after step 408,
_If it exceeds _r0max , the process proceeds to step 408 and subsequent steps after recalculating the sideslip angle in steps 406 and 407.

In step 408, the cornering force of the front and rear wheels based on the approximation formula (FIG. 5) based on the formulas (22) and (23) is used.
Calculation of C _f (n) _and C _r (n), and cornering power of front and rear wheels using the calculated values K _f (n) = C _f (n) / β _f (n),
K _r (n) = C _r (n) / β _r (n) is calculated, and step 409 is a target yaw rate calculation process. As described above, when the process directly proceeds to step 408, The above steps
As a result of applying β _f (n), β _r (n) calculated in 403 as it is, depending on the steady rear wheel steering angle δ _r0 (n), when it is _smaller than δ _{r0 max,} C _f (n) _, When calculating C _r (n), the linear steady-state sideslip angles β _f (n) and β _r (n) are used and calculated from the cornering force corrected according to the cornering force characteristics modeled in advance. The set yaw rate is set as the target value. On the other hand, in the case exceeding _δr0max , the rear wheel steering angle is changed to δ instead of the linear steady side slip angle described above.
_{Using the} steady side slip angle generated as _r0max , the corner corrected in accordance with the cornering force characteristic modeled in advance.
The yaw rate calculated from the nulling force is set as the target value. That is, when proceeding from step 405 to step 406 and below, in those steps,
at the _{δ r0 (n) = δ r0max} , wherein (55A), (56A) performs a calculation based on the formula, sideslip angle occurs constantly in a state where the rear wheels off _{δ r0 β f (n),} β r ( n).

Thus, proceeding to step 408, here, the sideslip angle calculated in step 403 or 407 and the constant K _fi, K of the approximate characteristic respectively applied (selected) at that time.
_rj , C _fi, C _{rj , the cornering force} C of the front and rear wheels
_f (n) _and C _r (n) (Equations (22) and (23))
From those C _f (n) _and C _r (n) and β _f (n) and β _r (n) values,
K _f (n) _, K applied to the operation of step 410 described later
Proceed to step 409 for _r (n). In step 409, using the calculated values C _f (n) _and C _r (n), a steady-state value (d / dt) φ _rS (n) of the target yaw rate is calculated based on the equation (60), Based on this, the target yaw angular acceleration (d ² / dt ² ) φ
_r (n) and the target yaw rate (d / dt) φ _r (n) are calculated in the same manner as in the previous embodiment (step in FIG. 7).
206).

Next, at step 410 (FIG. 16)
K calculated in step 408_f(n)_, K _r(n) Value and vehicle speed V
_xUsing (n), each of the vehicle models
Correct the rare number (Equations (9) to (16)), and
In 411 and 412, the target yaw rate and coefficient are applied.
In the same manner as in steps 207 and 208 in FIG.
Execute the arithmetic processing, and aim to match the target yaw rate.
Rear wheel steering angle δ_rmCalculate (n) and exit this program
You. Based on the target rear wheel steering angle calculated in this way,
The steering angle is controlled by the pressure servo valve in the system.
You.

FIGS. 17 and 18 show examples in which the effect of the above control is obtained by simulation calculation. FIG. 17 shows the case of step steering, FIG. 18 shows the case of lane change, and FIG. 17 shows the result of a comparative example similar to the above (in the case where the target yaw rate is based on the above equations (19) to (21)) shown in comparison with FIG. In each case, the driving conditions (simulation conditions) are as follows: vehicle speed V _x = 150 km /
h, the steering angle θ = 60 deg. In the case of step-like steering, in the comparative example, as shown in FIG. 19, the generated yaw rate does not match the target value, and a steady-state deviation occurs.
It can be seen that in the case of this control, as shown in FIG. Also, in the result of the lane change in FIG. 18, compared with the case of FIG. 13, according to the present control, similarly, overshoot does not occur in the yaw rate, and even under the running conditions of high speed and large steering angle. It can be seen that the behavior of the vehicle is stable.

Similarly, according to the present embodiment, the actual cornering power does not match the cornering power in the vehicle model at a high speed and a large steering angle at which the wheel sideslip angle becomes large, and the target yaw rate is similarly set. Avoiding unrealistic values is avoided. A linear stationary side slip angle and a stationary rear wheel steering angle are obtained from a linear stationary yaw rate obtained by giving a vehicle speed and a steering angle to a nonlinear vehicle model set in advance by a vehicle specification and a motion equation to be controlled. If the angle is equal to or less than the threshold, use the linear steady sideslip angle.If the rear wheel steering angle exceeds the threshold, calculate the steady sideslip angle that uses the rear wheel steering angle as a threshold and use it. Thus, it is possible to set the yaw rate calculated from the cornering force according to the side slip angle to be applied from the cornering force characteristics modeled in advance as a target yaw rate. In the control, the generated yaw rate can be made to coincide with the target value in the transient or steady state even at a high speed and a large steering angle,
The controllability and stability of the vehicle can be further improved as compared with the comparative example.

Next, as an example, the vehicle motion target setting means is set in advance by a vehicle model (non-linear model) in consideration of a cornering force characteristic with respect to a tire slip angle, a vehicle specification and a motion equation. The stationary rear wheel steering angle is calculated from the non-linear vehicle model so that the target stationary value calculated for each steering angle from both the linear model and the vehicle model is equal. This is a case where a steady-state value obtained by input to a model is set as a target value. Also in this case, the exercise target value is the yaw rate, and the steady gain in the reference model is the yaw rate gain. Preferably, the reference model stores the target steady-state value defined above as data corresponding to each vehicle speed and each steering angle.

This embodiment is based on the following viewpoints. In the case of the comparative example in which the target yaw rate is set by the above-described equations (19) to (21) and the rear wheel steering angle is controlled, there is no steady-state control, that is, the rear wheel steering angle becomes zero in a steady state. (Fig. 19
(B) The control law. The cornering power (
From the linear reference model where K _f , K _r ) is constant (linear region) as mentioned above, the target yaw rate ((d / dt) φ _r (t)) is calculated to be proportional to the steering angle (later The method of calculating the wheel rudder angle is as follows: the cornering power in the equation of motion represented by the equations (7) to (16) is calculated from a linear vehicle model defined as a fixed (linear value). When a large steering angle is input, the cornering force saturates, and a steady-state error occurs between the generated value and the target value for the yaw rate (for example, see FIG. 19C). In this embodiment, steady-state characteristics are not improved by calculating a steady-state rear wheel steering angle and performing steady-state control so that the yaw rate becomes a linear target value in a nonlinear region where the cornering force is saturated.

In this case, the reference target value is realized by mapping the steady-state characteristics depending on the steering angle and the vehicle speed in consideration of the non-linearity of the tire. This is due to the following. Improvements to the steady-state error and the like as shown in the comparative example can also be performed by using a nonlinear reference model and a nonlinear vehicle model that take into account the nonlinear characteristics of the tire.However, when the nonlinear model is implemented by a controller, the software uses a linear model. This is more complicated than that of the above case, and the memory and the operation time are required accordingly. Therefore, when emphasizing these points, a linear model is used for the vehicle model while the reference model is as follows, in order to achieve the above-mentioned improvement of the steady-state characteristics while avoiding software complexity due to the nonlinear model. The data relating to the steady-state yaw rate characteristic is mapped and stored, and such a method can be adopted, and this is the case in the present embodiment. Therefore, in the case of the present embodiment, the target value setting unit 5a in FIG. 2 sets the target value by searching from the map, and the steering angle calculation unit 6a calculates the target steering angle by calculation based on the linear vehicle model. .

Hereinafter, a method of mapping the reference model will be described with reference to FIG. FIGS. 20 and 21 are examples of flowcharts for calculating the map of the reference model.
FIG. 22 is an example of a steering angle-steady yaw rate characteristic diagram at a certain vehicle speed. First, in obtaining the steady-state characteristics of the 2WS, it is considered that the tire characteristics are modeled in the same manner as in the above-described embodiments. Also in this example, if an approximate characteristic as shown in FIG. 5 is applied to the characteristic in FIG.
2), (23), (24a) to (24f), and equations (25) and (26) hold, respectively. In addition, the steady-state characteristics of the 2WS are similarly calculated from the equation of motion of two degrees of freedom described above by using (d ² / dt ² ) φ (t) and (d / dt)
Assuming that V _y (t) and δ _r (t) are zero, (1
A), (2A), (5A), (6A) hold, and the first
Based on the equations (27), (28), (29), and (30) shown in the description of the embodiment, the equation (31) for the steady side slip angle is derived. That is, the steady sideslip angles β _f , β _r are, from the equation (31),

[ _Expression 82] β _f = ｛(pC _fi + K _rj θ / N− C _rj ) k ₀ − K _rj C _fi ｝ / a ₀ --- (81)

[ _Equation 83] β _r = ｛(pC _fi + pK _fi θ / N− C _rj ) k ₀ − K _fi C _rj ｝ / a ₀ --- (82) where a ₀ = (K _rj + pK _fi ) k ₀ + K _fi · K _rj .

From the above equations (81) and (82), the vehicle speed V _x and the steering angle θ are given (in the above, k ₀ is a variable of the vehicle speed V _x represented by k ₀ = MV _x ² / 2L (1 + p)) (Equation (29)), as described in the first embodiment, β _f and β _r calculated by sequentially inputting K _fi , C _fi , K _rj , and C _rj are (24a ) ~(twenty four
f) Select the value when the existence condition defined by the formula is satisfied. Then, if β _f and β _r are obtained, similarly, the steady cornering force C can be obtained from the above equations (22) and (23).
_f, Motomari is C _r, further the (2A) when 2WS from Equation steady Yo -
Late (d / dt) φ ₀

(D / dt) φ ₀ = 2 (C _f + C _r ) / MV _x --- (83)

Since the steady yaw rate is a two-variable function of the vehicle speed and the steering angle as described above, the map is formed by changing the steering angle for each certain vehicle speed as shown in FIG. -Determine the late characteristics. Further, in the same condition form, the linear stationary yaw rate (d / dt) φ _L0 is

(Eq. 85) (d / dt) φ _L0 = H ₀ θ --- (84) However, steady-state yaw rate gain: H ₀ = V _x / ((1 + A · V
_x ² ) LN).

Thus, the steady rear wheel steering angle δ _r0 is set so that the actual yaw rate becomes a linear steady yaw rate (d / dt) φ _L0.
From the equations (5) and (6) and the equations (81) to (83), they can be expressed as follows.

Δ _r0 = θ / N−L · (d / dt) φ _L0 / V _x − (β _f −β _r ) --- (85) If the rear wheel steering angle is constantly given to the vehicle, It is equal to the linear steady-state yaw rate even in a region where the cornering force is saturated. Therefore, in the map of the reference model, the steady-state yaw rate when the rear wheel steering angle is input to the linear model is set as a target steady-state value, and the target steady-state value is expressed by the following equation.

(D / dt) φ _r0 = V _x · (θ / N−δ _r0 ) / (L · (1 + A · V _x ² ) --- (86) The target steady-state value (d The steady-state characteristics can be improved by mapping / dt) _φr0 for each vehicle speed and using the data of the reference model.

In FIGS. 20 and 21, the above-mentioned mapping is performed according to the following procedure.
It is done in. Vehicle speed V_xAt any vehicle speed value V
(d / dt) φ_r0When obtaining data, first, θ = 0, V_x= 0
(Step 500), then steps 501-50
Perform step 5. Here, the steady side slip angle calculation (step
The specific contents of these processes including (502)
Basically the same as 0. (As in this program example, β
_f, β_rAfter determining the boundary conditions, C_f, C_rYou can do arithmetic
I). Front and rear wheel cornering force C_f, C_rCalculation (
After step 505), the steady-state yaw rate according to the above equations (83) and (84) is obtained.
(d / dt) φ₀(Nonlinear), steady-state yaw rate (d / dt) φ
_L0Calculation (linear) (steps 506 and 507)
Rear wheel steering angle δ_r0Is calculated (step 508), and the equation (86) is calculated.
The target steady-state yaw rate is calculated (step 509).
Replace the above calculation with θ until the θ value becomes 360deg, for example.
(Steps 510 and 511)
Value obtained in 9 (d / dt) φ_r0Is obtained as data. Change
And vehicle speed V_xAnd sequentially set in place of other values V (step
500), (d / dt) φ in the range of 0 to 360 deg θ for each vehicle speed
_r0Is obtained as data.

As described above, the nonlinear vehicle model is designed so that the steering angle-steady yaw rate characteristics obtained from both the linear model in which the tire characteristics are considered in advance and the linear reference model in which the cornering power is constant coincide. , A steering angle-steady yaw rate characteristic obtained by inputting the rear wheel steering angle to a linear vehicle model is mapped in a reference model to set a target steady value. As a reference model, a controller in which the target steady-state value is stored as data corresponding to the vehicle speed and the steering angle can be read out according to the detected steering angle and the vehicle speed value during the rear wheel steering angle control. A target rear wheel steering angle required for realizing this in the vehicle to be controlled is calculated by a calculation based on the vehicle model, and the steering angle control is performed.

FIG. 23 shows an example in which the effect of the present embodiment is obtained by simulation calculation. The simulation conditions are as follows: vehicle speed V _x = 150 km / h, steering angle θ
= 60 deg, high speed and large steering angle, but it can be seen that the steady state is improved in this control as compared with the case of the comparative example of FIG. 19 under the same conditions. It is also possible to realize the above while avoiding complicating software in the controller, etc., based on the vehicle specifications to be controlled, the equation of motion and the tire characteristics in advance, and the steady yaw rate characteristics at a certain vehicle speed and steering angle. On the basis of the steady-state yaw rate obtained from the linear reference model, a steady-state rear wheel steering angle at which the yaw rate matches even in a region where the cornering force of the tire is saturated is obtained. Since the calculated linear steady-state yaw rate is used as the target steady-state value of the reference model, the steady-state characteristics can be improved even when a linear vehicle model is used as the controller even at a high speed and a large steering angle where the wheel sideslip angle is large.

The present invention is not limited to the embodiment described above. For example, in each of the embodiments, the method of controlling the rear wheel steering angle has been described as an example, but the same control is performed by the front wheel steering angle by adding a mechanism that can increase or decrease the steering angle to the front wheel steering mechanism. It is also possible. Also,
Instead of the vehicle speed sensor (4), it is also possible to calculate a vehicle longitudinal direction speed by detecting a wheel speed, a vehicle longitudinal acceleration, and the like.

[0087]

According to the present invention, an appropriate target value is set in a steering angle control for realizing a motion target value set based on a detected steering angle value and a detected speed value in a vehicle longitudinal direction by controlling an auxiliary steering angle. As a result, it is possible to improve the maneuverability.
According to the above-described rudder angle control, which is the basis of the present invention, a vehicle model that is set in advance by vehicle specifications and equations of motion, and that is varied by a cornering power equivalent value corresponding to the sideslip angle of the front and rear wheels is used. When the steering angle detection value and the speed detection value are given thereto, the values that constantly occur can be used as the target steady value of the controlled variable related to the vehicle motion. Even at a large steering angle, the target value of the controlled variable becomes appropriate, and it is possible to suppress occurrence of overshoot or the like in the generated value, thereby improving the vehicle maneuverability and stability. Here, in claim 1, a linear steady side slip angle and a steady steering angle are obtained from a linear steady controlled amount obtained by giving a steering state detection value and a speed detection value to a linear vehicle model set in advance by vehicle specifications and a motion equation. When the steady steering angle is equal to or smaller than the threshold value, the steady value calculated from the linear vehicle model is calculated.
Each can be selected to be the target steady-state value of the controlled variable related to the movement of the vehicle, and even if the wheel skid angle is large at high speed and large steering angle, the generated value matches the target value of the controlled variable. And the vehicle maneuverability and stability can be improved. In the case of claim 2, the target steady-state value of the controlled variable relating to the vehicle motion is calculated from the vehicle model of the nonlinear vehicle model and the linear model in which the cornering force characteristic with respect to the tire slip angle is considered in advance. The steady-state steering angle of the control wheel is obtained from the non-linear vehicle model so that the target steady-state value calculated for each of them becomes equal, and the steady-state value obtained by inputting the steady-state steering angle and the steering angle to the linear vehicle model is the target value. Therefore, even when a linear vehicle model is used, the steady-state characteristics can be improved even at a high speed and a large steering angle where the wheel sideslip angle is large, and thereby the vehicle maneuverability and stability can be improved.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram showing an embodiment of the present invention.

FIG. 2 is a functional block diagram showing an example of a steering angle control system in the same example.

FIG. 3 is an explanatory diagram of a vehicle motion model having two degrees of freedom in yawing and a lateral direction.

FIG. 4 is a graph showing general characteristics of a wheel side slip angle and a cornering force.

FIG. 5 is a diagram showing an example of an approximate characteristic of a front wheel sideslip angle and an approximate characteristic of a front wheel cornering force, and an example of an approximate characteristic of a rear wheel sideslip angle and an approximate characteristic of a rear wheel cornering force applicable to the apparatus of the embodiment.

FIG. 6 is a diagram showing an example of a rear wheel target steering angle calculation flowchart executed by a controller in a divided manner, showing a part of the flowchart.

FIG. 7 is a view showing another part in the same manner.

FIG. 8 is a diagram showing still another part.

FIG. 9 is a diagram showing a divided flowchart of an example of the subroutine in FIG. 7 and showing a part thereof.

FIG. 10 is a view showing another part in the same manner.

FIG. 11 is a diagram showing still another part.

FIG. 12 is a diagram illustrating an example of a control effect by the embodiment apparatus by simulation calculation.

FIG. 13 is a diagram showing control contents in a comparative example.

FIG. 14 is a diagram illustrating an example of a rear wheel target steering angle calculation flowchart according to another embodiment of the present invention in a divided manner, showing a part thereof.

FIG. 15 is a view showing another part in the same manner.

FIG. 16 is a diagram showing still another part.

FIG. 17 is a diagram showing an example of a control effect in the same example by simulation calculation.

FIG. 18 is a diagram showing another example of the control effect by simulation calculation. It is a figure which shows another part.

FIG. 19 is a diagram showing control contents in a comparative example.

FIG. 20 is a diagram showing an example of a flow chart for mapping according to still another embodiment of the present invention in a divided manner, and showing a part thereof.

FIG. 21 is a view showing another part in the same manner.

FIG. 22 is a diagram showing a yaw rate characteristic and the like used for the description in the same example.

FIG. 23 is a diagram showing an example of a control effect in the same example by simulation calculation.

[Explanation of symbols]

 1a Vehicle 2a Auxiliary steering mechanism 3 Steering angle sensor 3a Steering state detector 4 Vehicle speed sensor 4a Forward / backward speed detector 5a Vehicle motion target setting unit 6a Steering angle calculator 20L, 20R Left and right rear wheels 21 Steering wheel 22 Rear wheel steering Hydraulic cylinder 23 pressure servo valve 31 rear wheel steering angle sensor 40 controller

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B62D 6/00

Claims (2)

(57) [Claims] 1. A front or rear at least one of the steering angle of the wheel can assist steering, in a vehicle control steering angle is controlled to match the target value by the control means, steering angle detection that detects a steering angle of the vehicle Means, speed detecting means for detecting the longitudinal speed of the vehicle, side slip angle calculating means for calculating the sideslip angles of the front wheels and rear wheels of the running vehicle, and front and rear wheels calculated by the sideslip angle calculating means Means for estimating or correcting a value corresponding to the cornering power of the wheel according to the side slip angle of the vehicle; and a value equivalent to the cornering power which is set in advance by vehicle specifications and equations of motion and is estimated or corrected. A target value of a steady-state characteristic and a transient characteristic of a controlled variable relating to the motion of the vehicle is set based on a nonlinear vehicle model that is variable according to the steering angle detection unit and a detection value of the speed detection unit. A target setting means, to the non-linear vehicle model, and the steering angle detection value, and the speed detection value, and a linear steady controlled amount calculated from a linear vehicle model which is set by the vehicle specification and motion equations When the steady steering angle of the control wheel obtained by giving is equal to or smaller than a predetermined threshold, a steady value calculated from the linear vehicle model is set as a target steady value,
Further, when the threshold value is exceeded, a vehicle motion target setting means for setting a steady value calculated from the non-linear vehicle model as a target steady value, and a vehicle for which the motion target value set by the vehicle motion target setting means is controlled. And a target assist steering angle calculating means for calculating an assist steering angle necessary for realizing the above by an operation based on the non-linear vehicle model to obtain a target value. 2. A front or rear at least one of the steering angle of the wheel can assist steering, in a vehicle control steering angle is controlled to match the target value by the control means, steering angle detection that detects a steering angle of the vehicle Means, a speed detecting means for detecting a longitudinal speed of the vehicle, a linear vehicle model set in advance by vehicle specifications and a motion equation, and a motion of the vehicle based on detection values of the steering angle detecting means and the speed detecting means. Target setting means for setting target values of a steady-state characteristic and a transient characteristic of a controlled variable with respect to a vehicle model of a non-linear vehicle model and a linear model in which a cornering force characteristic with respect to a tire slip angle is considered in advance. The steady-state steering angles of the control wheels are obtained from the nonlinear vehicle model so that the target steady-state values calculated for the steering angles are equal to each other. Vehicle motion target setting means for setting a steady value obtained by input to a vehicle model as a target value; and auxiliary steering necessary for realizing the motion target value set by the vehicle motion target setting means in a vehicle to be controlled. A vehicle steering angle control device, comprising: a target auxiliary steering angle calculating means for calculating an angle by a calculation based on the linear vehicle model to obtain a target value.