JP2006069496A - Front-rear wheel steering control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a front-rear wheel steering control device capable of bringing the generated yaw rate close to the target yaw rate characteristic by suppressing the change of the vehicular yaw rate characteristic attributable to the follow-up delay of a steering actuator. <P>SOLUTION: The front-rear wheel steering control device controls the yaw rate and the lateral velocity of a vehicle by using steering actuators 6, 7 provided on a front wheel steering mechanism 12 and a rear wheel steering mechanism 17, respectively. A steering controller 3 corrects the target steering angle of the other steering actuator according to the difference in the steering angle between the actual steering angle and the target steering angle when a delay occurs in which the actual steering angle of one steering actuator cannot follow the target steering angle so that the change in the vehicular yaw rate characteristic attributable to the follow-up delay is suppressed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention belongs to the technical field of front and rear wheel steering control devices that provide auxiliary steering angles to front wheels and rear wheels at the time of steering input to front wheels.

In the conventional front and rear wheel steering control device, the front wheel steering actuator and the rear wheel steering actuator are driven by the added value of the feed forward term based on the steering steering angle and the feedback term based on the detected yaw rate, and the vehicle yaw rate and lateral The speed is controlled (see, for example, Patent Document 1).
JP-A-5-105102

  However, in the above prior art, since the front wheel steering angle and the rear wheel steering angle are feedback controlled based on the target yaw rate according to a predetermined control law, the target steering angle value is applied to one of the front wheels or the rear wheel steering actuator. When a follow-up delay occurs, the target vehicle yaw rate characteristic cannot be realized.

  The present invention has been made paying attention to the above-mentioned problem, and the object of the present invention is to change the vehicle yaw rate characteristic caused by the delay even when a tracking delay occurs in one of the front wheel or rear wheel steering actuators. An object of the present invention is to provide a front and rear wheel steering control device that can suppress the generated yaw rate to be close to the target yaw rate.

In order to achieve the above object, in the present invention,
In the front and rear wheel steering control device for controlling the yaw rate and the lateral speed of the vehicle using the steering actuators provided for the front wheel steering mechanism and the rear wheel steering mechanism,
Follow-up delay detecting means for detecting the follow-up delay of the steering actuator;
Rudder angle deviation detecting means for detecting a rudder angle deviation between the actual rudder angle and the target rudder angle of each of the front and rear wheels;
When the tracking delay of one steering actuator is detected, the target steering angle of the other steering actuator is set to the steering angle deviation on the side where the tracking delay is detected so that a change in the yaw rate characteristic of the vehicle is suppressed. A target rudder angle correcting means for correcting in response,
Is provided.

  In the present invention, when a follow-up delay occurs in one of the steering actuators, the change in the vehicle yaw rate characteristic due to the follow-up delay is suppressed in accordance with the rudder angle deviation between the target rudder angle and the actual rudder angle. Since the target steering angle of the other steering actuator is corrected, the generated yaw rate can be brought close to the target yaw rate characteristic of the vehicle.

  Hereinafter, the best mode for carrying out the present invention will be described based on the first embodiment.

First, the configuration will be described.
FIG. 1 is an overall system diagram of the front and rear wheel steering control device according to the first embodiment.
A steering angle sensor 1 and a front wheel steering actuator 6 are provided on a column shaft 13 that connects a steering wheel 10 and a front wheel steering mechanism 12 that steers the front wheels 11 and 11.

  For example, the front wheel steering actuator 6 includes a motor and a speed reducer, and the output shaft of the motor is connected to the column shaft 13 via the speed reducer. The front wheel steering actuator 6 is a device that decelerates the rotation input via the column shaft 13 by the variable gear ratio according to the steering angle command value from the front wheel steering controller 4 and outputs it to the steering gear of the front wheel steering mechanism 12. As a result, the steering gear ratio, which is the ratio of the steering angle of the steering wheel 10 to the steering angle of the front wheels 11, 11, is variably controlled.

  Similar to the front wheel steering actuator 6, the rear wheel steering actuator 7 is composed of a motor, a speed reducer, and the like, and is output to the rack shaft of the rear wheel steering mechanism 15 for steering the rear wheels 14, 14 via the speed reducer. The shafts are connected. The rear wheel steering actuator 7 variably controls the steering angles of the rear wheels 14 and 14 based on the steering angle command value from the rear wheel steering controller 5.

  The front wheel steering controller 4 calculates a steering angle command value that eliminates the deviation between the target front wheel steering angle generated by the steering control controller 3 and the actual front wheel steering angle value detected by the front wheel actual steering angle sensor 16. The calculated steering angle command value is output to the front wheel steering actuator 6.

  The rear wheel steering controller 5 controls the steering angle command so as to eliminate the deviation between the target rear wheel steering angle generated by the steering control controller 3 and the actual rear wheel steering angle value detected by the rear wheel actual steering angle sensor 17. A value is calculated, and the calculated steering angle command value is output to the rear wheel steering actuator 7.

  The steering angle sensor 1 detects the steering angle of the steering wheel 10 using a pulse encoder or the like. The vehicle speed sensor 2 detects the vehicle speed from the average value of the wheel speeds.

  The steering control controller 3 generates a target front wheel steering angle and a target rear wheel steering angle according to the steering angle detected by the steering angle sensor 1 and the vehicle body speed detected by the vehicle speed sensor 2, and performs target front wheel steering. The angle is output to the front wheel steering controller 4, and the target rear wheel steering angle is output to the rear wheel steering controller 5.

  FIG. 2 is a control block diagram of the steering control controller 3, and the steering control controller 3 includes a target value generation unit 31, a target output generation unit 32, and a target output correction unit 33.

  As shown in FIG. 3, the target value generation unit 31 includes a vehicle model calculation unit 311, a target value calculation unit 312, and a target value correction unit 313.

  The vehicle model calculation unit 311 calculates vehicle parameters using a two-wheel model based on the steering angle and the vehicle body speed. The calculated vehicle parameter is output to the target value calculation unit 312.

  The target value calculation unit 312 determines the target yaw rate and the target lateral speed of the vehicle based on the steering angle, the vehicle body speed, and the vehicle parameters. The determined target yaw rate and target lateral velocity are output to the target output generator 32.

  As shown in FIG. 4, the target output generation unit 32 includes a target front and rear wheel steering angle calculation unit 321 for yaw rate / lateral speed control and a target rear wheel steering angle calculation unit 322 for yaw rate control.

  The target front and rear wheel steering angle calculation unit 321 of the yaw rate / lateral speed control determines a target front wheel steering angle and a target rear wheel steering angle based on the target yaw rate and the target lateral speed, and outputs them to the front wheel steering controller 4.

  The yaw rate control target front and rear wheel steering angle calculation unit 322 determines the yaw rate control target front wheel steering angle and the yaw rate control target rear wheel steering angle from the target yaw rate, the front wheel steering angle value, and the rear wheel steering angle value, and the rear wheel steering controller 5. Output to.

  As shown in FIG. 5, the target output correction unit 33 includes an actuator delay detection unit (following delay detection unit) 331, a correction value calculation unit (correction value calculation unit) 332, and an output steering angle correction unit (target steering angle correction). Means) 333, the target front wheel steering angle during normal control, the target rear wheel steering angle during normal control, the yaw rate control target front wheel steering angle, the yaw rate control target rear wheel steering angle, the front wheel steering angle value, and the rear wheel steering angle value. Based on this, the target front wheel steering angle and the target rear wheel steering angle are determined.

  The actuator delay detection unit 331 determines a front wheel delay flag and a rear wheel delay flag based on the target front wheel steering angle, the target rear wheel steering angle, the front wheel steering angle value, and the rear wheel steering angle value, and an output steering angle correction unit 333. Output to.

  The correction value calculation unit 332 calculates the front wheel correction value based on the target front wheel steering angle, the target rear wheel steering angle, the front wheel steering angle value, the rear wheel steering angle value, the yaw rate control target front wheel steering angle, and the yaw rate control target rear wheel steering angle. The rear wheel correction value is determined and output to the output steering angle correction unit 333.

  The output steering angle correction unit 333 is based on the target front wheel steering angle during normal control, the target rear wheel steering angle during normal control, the front wheel correction value, the rear wheel correction value, the front wheel delay flag, and the rear wheel delay flag. The target rear wheel steering angle is determined, the target front wheel steering angle is output to the front wheel steering controller 4, and the target rear wheel steering angle is output to the rear wheel steering controller 5.

Next, the operation will be described.
[Vehicle model calculation]
The vehicle model calculation unit 311 calculates vehicle parameters using the vehicle model shown below.

ここで、

である。 In general, assuming a two-wheel model, the yaw rate and lateral speed of the vehicle can be expressed by the following equation (1).

here,

It is.

When the transfer functions of the yaw rate and lateral velocity for the front wheel steering are obtained from the state equation, the following equations (3) and (4) are obtained.

ここで、

である。 The yaw rate transfer function is expressed by the following equation (5) from equation (3).

here,

It is.

ここで、

である。 Similarly, the lateral velocity transfer function is expressed by the following equation (7) from equation (4).

here,

It is.

が求められる。 From the above, vehicle parameters

Is required.

[Target value calculation]
The target value calculation unit 312 obtains a target yaw rate ψ ′ ^* and a target lateral velocity V _y ^* from the vehicle body speed V, the vehicle parameters, and a target value parameter described later.

The target yaw rate ψ ′ ^* is expressed by the following equation (9) from equation (5).

The target lateral velocity V _y ^* is expressed by the following equation (10) from equation (7).

ただし、yrate_gain_map，yrate_omegn_map，yrate_zeta_map，yrate_zero_mapはチューニングパラメータである。 Here, the parameter of the target yaw rate ψ ′ ^* is expressed by the following equation (11).

However, yrate_gain_map, yrate_omegn_map, yrate_zeta_map, and yrate_zero_map are tuning parameters.

ただし、vy_gain_map，vy_omegn_map，vy_zeta_map，vy_zero_mapはチューニングパラメータである。 Further, the parameter of the target lateral speed V _y ^* is expressed by the following equation (12).

However, vy_gain_map, vy_omegn_map, vy_zeta_map, and vy_zero_map are tuning parameters.

から、

[Target rudder angle calculation]
The yaw rate / lateral speed control target front / rear wheel steering angle calculation unit 321 calculates the target front wheel steering angle θ ^* and the target rear wheel steering angle δ ^* from the target yaw rate ψ ′ ^* and the target lateral speed V _y ^* .

From

Therefore, the target front wheel steering angle θ ^* is expressed by the following equation (15).

The target rear wheel steering angle δ ^* is expressed by the following equation (16).

[Yaw rate control target value calculation]
The yaw rate control target front and rear wheel steering angle calculation unit 322 calculates the yaw rate control target front wheel steering angle θ _{ψ ′} ^* and the yaw rate control target from the target yaw rate ψ ′ ^* , the front wheel actual steering angle value θ, and the rear wheel actual steering angle value δ. The wheel steering angle δ _{ψ ′} ^* is calculated.

In the case of yaw rate control using only front wheel steering, the yaw rate control target front wheel steering angle θ _{ψ ′} ^* is expressed by the following equation (17) using the actual rear wheel steering angle δ at that time.
^{_{θ ψ '* = {ψ "}} * - (a 11 ψ' * + a 12 V y + b f1 δ)} / b r1 ... (17)

Similarly, in the case of yaw rate control only by rear wheel steering, the yaw rate control target rear wheel steering angle δ _{ψ ′} ^* is expressed by the following equation (18) using the actual front wheel steering angle θ at that time.
_{δψ ′} ^* = {ψ ” ^* − (a ₁₁ ψ ′ ^* + a ₁₂ V _y + b _f1 θ)} / b _r1 (18)

Here, there is no tracking delay in each actuator,
If θ ^* = θ then δ ^* = δ
That is, if there is no delay in the front wheels, the target rear wheel rudder angle of the yaw rate / lateral speed control and the yaw rate control match,
If δ ^* = δ, θ ^* = θ
That is, if there is no delay in the rear wheels, the target front wheel steering angles of the yaw rate / lateral speed control and the yaw rate control are the same.

[Actuator delay detection processing]
In the actuator lag detection unit 331, the target front-wheel steering angle theta _r ^{*, *} target rear wheel steering angle [delta] _r corrected, based on the front-wheel steering angle value theta and the rear wheel steer angle [delta], a front wheel delay determination flag F _theta A rear wheel delay determination flag _Fδ is determined.

Deviation threshold for front wheel delay judgment is V _θ (≧ 0), time threshold is T _θ , deviation threshold for rear wheel delay judgment is V _δ (≧ 0), and time threshold is T _δ Then
When θ ≦ (θ _r ^* −V _θ ) or (θ _r ^* + V _θ ) ≦ θ continues for T _θ or more and F _δ = 0, F _θ = 1
Otherwise, F _θ = 0
And

Also, when δ ≦ (δ _r ^* −V _θ ) or (δ _r ^* + V _θ ) ≦ δ continues for T _δ or more and F _θ = 0, F _δ = 1,
Otherwise, F _δ = 0
And Only one of the delay determination flags is 1.

[Correction value calculation]
In the correction value calculation unit 332, the target front wheel steering angle θ _r ^* , the target rear wheel steering angle δ _r ^* , the yaw rate control target front wheel steering angle θ _{ψ ′} ^* , the yaw rate control target rear wheel steering angle δ _{ψ ′} ^* , and the front wheel steering angle A front wheel output correction value G _θ and a rear wheel output correction value G _δ are determined based on the value θ and the rear wheel steering angle value δ.

When a delay occurs in the front wheel steering actuator 6 (F _θ = 1), a correction value for correcting the target rear wheel steering angle is derived. A target value is set between the target rear wheel steering angle δ ^{* of} normal control (yaw rate / lateral speed control) and the yaw rate control target rear wheel steering angle δ _{ψ ′} ^* according to the delay steering angle deviation of the front wheels 11, 11. To do.

The difference between the target value θ _r ^* of the front wheel steering angle and the actual front wheel steering angle θ (corresponding to the steering angle deviation), the target value δ ^* during normal control of the rear wheel steering, and the target rear wheel steering angle δ _{ψ ′} during yaw rate control ^{From *} , it sets like the following formula (19).
^{_{G δ = (δ * -δ ψ}} '*) (θ r * -θ) / {MAX (| θ r * |, | θ |, | θ r * -θ |)} ... (19)
However, if θ _r ^* = θ = 0, G _δ = 0.
In addition, G _δ is set to be smaller as | θ _r ^* | or | θ | is larger and the steering angle deviation (θ _r ^* −θ) is smaller. Therefore, when the yaw rate is large and the steering angle is large, vehicle behavior The correction value is suppressed so as not to disturb.

Similarly, when a delay occurs in the rear wheel steering, a correction value for correcting the target front wheel steering angle is derived from the following equation (20).
^{_{G θ = (θ * -θ ψ}} '*) (δ r * -δ) / {MAX (| δ r * |, | δ |, | δ r * -δ |)} ... (20)
However, when δ _r ^* = δ = 0, G _θ = 0.
Further, G _δ is set to be smaller as | δ _r ^* | or | δ | is larger and the steering angle deviation (δ _r ^* −δ) is smaller. Therefore, when the yaw rate is large and the steering angle is large, vehicle behavior The correction value is suppressed so as not to disturb.

[Target output correction processing]
In the output rudder angle correction unit 333, the target front wheel steering angle θ ^* during normal control, the target rear wheel steering angle δ ^* during normal control, the front wheel delay determination flag F _θ , the rear wheel delay determination flag F _δ , and the front wheel output correction value G _θ The target front wheel steering angle θ _r ^* and the target rear wheel steering angle δ _r ^* are determined based on the rear wheel output correction value G _δ .

(1) When the front wheel delay determination flag _Fθ is 1 When the front wheel steering actuator 6 is delayed with respect to the target value, for example, if the steering is increased by control, only a small value is obtained for the desired yaw rate characteristic. become.

  In that case, the characteristic change due to the delay of the front wheel steering actuator 6 is improved by correcting the target rear wheel steering angle, and the yaw rate characteristic of the vehicle is brought close to the target value.

Using the correction value obtained by Equation (20), the target rear wheel steering angle δ _r ^*
δ _r ^* = δ ^* −G _δ (21)
And The front wheel target steering angle θ ^* is not changed. If the front wheel delay determination flag F θ ₌ 0, is δ _r ^* = δ ^*.

(2) When the rear wheel delay flag F _δ is 1 Similarly, when the rear wheel steering actuator 7 is delayed with respect to the target value, the target front wheel steering angle θ _r ^* is calculated using the correction value obtained by the equation (19). Use
θ _r ^* = θ ^* −G _θ (22)
And The rear wheel target rudder angle δ ^* is not changed. When the rear wheel delay determination flag F _δ = 0, θ _r ^* = θ ^* .

[Front and rear wheel steering control processing]
FIG. 6 is a flowchart showing the flow of front and rear wheel steering control processing executed by the steering controller 3, and each step will be described below.

In step S1, the target value generator 31 calculates the target yaw rate ψ ′ ^* and the target lateral velocity V _y ′ from the steering angle θ and the vehicle body speed V, and the process proceeds to step S2.

In step S2, the target front wheel steering angle θ ^* during normal control and the target are calculated from the target yaw rate ψ ′ ^* and the target lateral velocity V _y ′ calculated in step S1 in the yaw rate / lateral speed control target front and rear wheel steering angle calculation unit 321. In addition to calculating the rear wheel steering angle δ ^* , the steering controller 3 determines the target front wheel steering angle and the target rear wheel steering angle from the target front wheel steering angle θ ^* during normal control and the target rear wheel steering angle δ ^* during normal control. The front wheel steering controller 4 outputs the front wheel steering angle command value to the front wheel steering actuator 6, the rear wheel steering controller 5 outputs the rear wheel steering angle command value to the rear wheel steering actuator 7, and the process proceeds to step S3.

In step S3, the actuator delay detector 331 determines the front wheel delay determination flag F _θ based on the target front wheel steering angle θ _r ^* , the target rear wheel steering angle δ _r ^* , the front wheel steering angle value θ, and the rear wheel steering angle value δ. The rear wheel delay determination flag _Fδ is determined, and the process proceeds to step S4.

In step S4, the yaw rate control target front and rear wheel steering angle calculator 322 calculates the yaw rate control target front wheel steering angle θ _{ψ ′} ^* from the target yaw rate ψ ′ ^* , the front wheel actual steering angle value θ, and the rear wheel actual steering angle value δ. The yaw rate control target rear wheel steering angle _{δψ ′} ^* is calculated, and the process proceeds to step S5.

In step S5, in the correction value calculation unit 332, the target front wheel steering angle θ _r ^* , the target rear wheel steering angle δ _r ^* , the yaw rate control target front wheel steering angle θ _{ψ ′} ^* , and the yaw rate control target rear wheel steering angle δ _{ψ ′} ^*. Based on the front wheel steering angle value θ and the rear wheel steering angle value δ, the front wheel output correction value G _θ and the rear wheel output correction value G _δ are determined, and the process proceeds to step S6.

In step S6, the output rudder angle correction unit 333 performs the normal control target front wheel steering angle θ ^* , the normal control target rear wheel steering angle δ ^* , the front wheel delay determination flag F _θ , the rear wheel delay determination flag F _δ , and the front wheel output. based on the correction value G _theta and the rear wheel output correction value G _[delta], to determine the target front wheel steering angle theta _r ^* and the target rear-wheel steering angle [delta] _r ^*, the routine proceeds to step S7.

In step S7, the front wheel steering controller 4 and the rear wheel steering controller 5 use the front wheel steering actuator 6 and the rear wheel steering actuator based on the target front wheel steering angle θ _r ^* and the target rear wheel steering angle δ _r ^* determined in step S6. 7 is driven and shifted to return.

[Front and rear wheel steering control operation]
When a follow-up delay has occurred in the front wheel steering actuator 6, in the flowchart shown in FIG. 6, the target rear wheel steering angle δ _r ^* is determined in step S6 by the rear wheel output correction value G _δ obtained in step S5. The value obtained by subtracting the rear wheel output correction value _Gδ from the target rear wheel steering angle δ ^* during normal control. The target front wheel steering angle θ _r ^* is maintained at the target front wheel steering angle θ ^* during normal control.

When a follow-up delay occurs in the rear wheel steering actuator 7, in the flowchart shown in FIG. 6, the target front wheel steering angle θ _r ^* is calculated in step S6 by the front wheel output correction value G _θ obtained in step S5. The value is obtained by subtracting the front wheel output correction value _Gδ from the target front wheel steering angle θ ^* during normal control. Note that the target rear wheel steering angle δ _r ^* is maintained at the target rear wheel steering angle δ ^* during normal control.

[Prior art issues]
In the technique described in Japanese Patent Application Laid-Open No. 5-105102, the auxiliary steering angle is given to the front and rear wheels by the addition value of the feed forward term based on the detected steering angle and the feedback term based on the detected yaw rate.

  However, in this prior art, the front wheel auxiliary rudder angle and the rear wheel auxiliary rudder angle are feedforward and feedback controlled in accordance with a certain control law based on the target yaw rate. In the case where a follow-up delay of the actual rudder angle with respect to the target rudder angle occurs, there is a problem that the target yaw rate characteristic of the vehicle cannot be achieved.

  Further, since the vehicle yaw rate is feedback-controlled, if the desired target rudder angle cannot be followed due to insufficient response of the actuator or insufficient thrust, the steering angle command value can be further set by performing yaw rate feedback. Even if it is increased, there is a problem that the target value cannot be followed and the target yaw rate characteristic cannot be satisfied.

[Target rudder angle correction action]
In contrast, in the front and rear wheel steering control device according to the first embodiment, even when a tracking delay occurs in one steering actuator, the target steering angle of the other steering actuator is suppressed, and a change in the yaw rate characteristic of the vehicle due to the tracking delay is suppressed. By changing to the direction in which the yaw rate is changed, the increase or decrease in the yaw rate characteristic due to the tracking delay can be improved.

  In addition, because the target steering angle of the other steering actuator is corrected according to the deviation between the target steering angle and the actual steering angle of the steering actuator where the delay occurred, the control output changes smoothly and the driver feels uncomfortable. There is no.

  FIG. 7 is a diagram showing the vehicle behavior when normal front and rear wheel steering control is performed by steering the front wheel at the middle vehicle speed and steering the rear wheel in the same phase. The yaw rate is increased by increasing the front wheel. The vehicle body slip angle is decreased by turning to the same phase as the front wheels and increasing the lateral acceleration (FIG. 8 (b)). At this time, the breakdown of the front wheel steering angle is the sum of the yaw rate increase and the rear wheel under (the amount by which the understeer by the rear wheel in-phase control is canceled) added to the driver's steering angle by the front wheel steering actuator. (FIG. 8 (a)).

  Here, when a follow-up delay occurs in the front wheel steering actuator, an understeer state in which the yaw rate does not increase even when the steering angle increases is obtained. On the other hand, when a follow-up delay occurs in the rear wheel steering actuator, an oversteer state in which the lateral acceleration does not increase although the yaw rate is increased is obtained.

In the first embodiment, when a follow-up delay occurs in the front wheel steering actuator 6 (FIG. 9), the front wheel steering angle deviation (deviation between the target front wheel steering angle θ _r ^* and the front wheel steering angle value θ) is the deviation threshold value V _θ. When the above time continues for the time threshold value _Tθ or more (FIG. 10), it is determined that a follow-up delay has occurred in the front wheel steering actuator 6.

When it is determined that a follow-up delay occurs in the front wheel steering actuator 6, the target yaw rate control target rear wheel steering angle δ _{ψ that the} target rear wheel steering angle δ ^* during normal control is obtained only from the target yaw rate ψ ′ ^*. _'so as to approach the ^*, normal control time by correcting the target rear wheel steering angle [delta] ^* in accordance with the front wheel steering angle deviation decreases the target rear wheel steering angle [delta] _r ^* (Fig. 11).

  Thereby, since the change in the yaw rate characteristic of the vehicle due to the follow-up delay of the front wheel steering actuator 6 is suppressed, the generated yaw rate is set to the target as shown in FIG. It can be closer to the yaw rate, and the traceability with respect to the driving trajectory intended by the driver is enhanced.

Further, when a follow-up delay occurs in the rear wheel steering actuator 7, by reducing the target front wheel steering angle θ _r ^* , the generation of an excessive yaw rate can be suppressed and the generated yaw rate can be brought close to the target yaw rate.

  In addition, when the front wheel steering actuator is steered at a low vehicle speed and the rear wheel is reversely steered, if the tracking delay occurs in the front wheel steering actuator, the yaw rate does not increase even if the steering angle increases, and the rear wheel Even when a follow-up delay occurs in the steering actuator, an understeer state occurs.

At this time, in the first embodiment, when the tracking delay occurs in the front wheel steering actuator 6, the target rear wheel steering angle δ _r ^* is increased, and when the tracking delay occurs in the rear wheel steering actuator 7, the target front wheel steering angle θ _The generated yaw rate can be made closer to the target yaw rate by increasing _r ^* .

Next, the effect will be described.
In the front and rear wheel steering control device of the first embodiment, the following effects can be obtained.

  (1) In the front and rear wheel steering control device for controlling the yaw rate and the lateral speed of the vehicle using the steering actuators 6 and 7 provided in the front wheel steering mechanism 12 and the rear wheel steering mechanism 17 respectively, the following delay of the steering actuators 6 and 7 When the following delay of one of the steering actuators is detected, the target steering angle of the other steering actuator is set to the actual steering of the steering actuator so that the change in the yaw rate characteristic of the vehicle is suppressed. Since the output rudder angle correction unit 333 that corrects the angle according to the rudder angle deviation between the angle and the target rudder angle is provided, the change in the vehicle yaw rate characteristic due to the follow-up delay can be suppressed, and the yaw rate characteristic of the vehicle targeting the generated yaw rate Can be approached.

  (2) The output rudder angle correction unit 333 corrects the target rudder angle during normal control for controlling the target yaw rate and the target lateral velocity in the direction of the target rudder angle during yaw rate control for controlling only the target yaw rate (formula (21)). Therefore, the vehicle can be easily brought close to the travel locus intended by the driver. If the target rudder angle is set based on the target lateral speed, the generated yaw rate becomes small, and it becomes difficult to bring the host vehicle close to the travel locus intended by the driver.

  (3) When the rear wheels 14, 14 are steered to the same phase as the front wheels 11, 11, the output rudder angle correction unit 333 corrects the output rudder angle correction unit 333 in a direction to decrease the target rudder angle according to the rudder angle deviation. By reducing the target rudder angle, the host vehicle can be easily brought close to the travel locus intended by the driver.

(4) When the rear wheels 14 and 14 are steered to the same phase as the front wheels 11 and 11, the output steering angle correction unit 333 determines that the actual front wheel steering angle θ cannot follow the target front wheel steering angle θ ^*. Since the target rear wheel steering angle δ ^* is corrected so as to decrease, the decrease of the slip angle is suppressed and the generated yaw rate can be made closer to the target yaw rate.

(5) When the rear wheels 14, 14 are steered in the same phase as the front wheels 11, 11, the output steering angle correction unit 333 follows the target rear wheel steering angle δ ^* . When this is not possible, the target front wheel steering angle θ ^* is corrected so as to decrease, so that the generation of an excessive yaw rate is suppressed and the generated yaw rate can be made closer to the target yaw rate.

  (6) The output rudder angle correction unit 333 corrects the rear wheel 14, 14 in a direction to increase the target rudder angle according to the rudder angle deviation when the rear wheels 14, 14 are steered to the opposite side to the front wheels 11, 11. The generated yaw rate can be made closer to the target yaw rate by increasing the target rudder angle.

(Other examples)
Although the best mode for carrying out the present invention has been described based on the first embodiment, the specific configuration of the present invention is not limited to the first embodiment. For example, the present invention can be applied to a vehicle using a so-called steer-by-wire type steering device in which a steering wheel and a front wheel steering mechanism are mechanically separated.

1 is an overall system diagram of a front and rear wheel steering control device of Embodiment 1. FIG. 4 is a control block diagram of a steering control controller 3. FIG. 3 is a control block diagram of a target value generation unit 31. FIG. 4 is a control block diagram of a target output generation unit 32. FIG. 4 is a control block diagram of a target output correction unit 33. FIG. 3 is a flowchart showing a flow of front and rear wheel steering control processing executed by a steering control controller 3. FIG. 6 is a diagram showing a vehicle behavior in a case where normal front / rear wheel steering control is performed by increasing front wheel turning steering and rear wheel in-phase steering at a medium vehicle speed. It is a figure which shows the breakdown of the front-wheel steering angle and the rear-wheel steering angle in the case of steering by increasing at medium vehicle speed. It is a figure which shows the delay of the front-wheel actual steering angle with respect to a target front-wheel steering angle. It is a figure which shows a front-wheel steering angle deviation. It is a change characteristic figure of the target rear-wheel steering angle which shows the target rear-wheel steering angle correction effect | action of Example 1. FIG. It is a change characteristic figure of generated yaw rate which shows a target rear wheel rudder angle correction operation of Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering angle sensor 2 Vehicle speed sensor 3 Steering control controller 31 Target value generation part 311 Vehicle model calculation part 312 Target value calculation part 32 Target output generation part 321 Yaw rate / lateral speed control target front and rear wheel steering angle calculation part 322 Yaw rate control target front and rear wheels Steering angle calculation unit 33 Target output correction unit 331 Actuator delay detection unit 332 Correction value calculation unit 333 Output steering angle correction unit 4 Front wheel steering controller 5 Rear wheel steering controller 6 Front wheel steering actuator 7 Rear wheel steering actuator 10 Steering wheel 11, 11 Front wheel 12 front wheel steering mechanism 13 column shaft 14, 14 rear wheel 15 rear wheel steering mechanism 16 front wheel actual steering angle sensor 17 rear wheel actual steering angle sensor

Claims (6)

In the front and rear wheel steering control device for controlling the yaw rate and the lateral speed of the vehicle using the steering actuators provided for the front wheel steering mechanism and the rear wheel steering mechanism,
Follow-up delay detecting means for detecting the follow-up delay of the steering actuator;
Rudder angle deviation detecting means for detecting a rudder angle deviation between the actual rudder angle and the target rudder angle of each of the front and rear wheels;
When the tracking delay of one steering actuator is detected, the target steering angle of the other steering actuator is set to the steering angle deviation on the side where the tracking delay is detected so that a change in the yaw rate characteristic of the vehicle is suppressed. A target rudder angle correcting means for correcting in response,
A front and rear wheel steering control device characterized by comprising: In the front and rear wheel steering control device according to claim 1,
The target rudder angle correcting means corrects the target rudder angle during normal control for controlling the target yaw rate and the target lateral velocity in the direction of the target rudder angle during yaw rate control for controlling only the target yaw rate. Control device. In the front and rear wheel steering control device according to claim 1 or 2,
The target rudder angle correction means corrects the target rudder angle in a direction to decrease the target rudder angle according to the rudder angle deviation when the rear wheel is steered to the same phase as the front wheel. . The front and rear wheel steering control device according to claim 3,
The front and rear wheel steering control device, wherein the target rudder angle correction means corrects the target rear wheel rudder angle in a direction to decrease when the actual front wheel rudder angle cannot follow the target front wheel rudder angle. The front and rear wheel steering control device according to claim 3,
The front and rear wheel steering control device, wherein the target rudder angle correcting means corrects the target front wheel rudder angle in a direction to decrease when the actual rear wheel rudder angle cannot follow the target rear wheel rudder angle. In the front and rear wheel steering control device according to claim 1 or 2,
The target rudder angle correction means corrects the front and rear wheel steering control in a direction to increase the target rudder angle according to the rudder angle deviation when the rear wheel is steered to the opposite phase side to the front wheel. apparatus.

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