JPH10250547A - Vehicle attitude control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly control a vehicle attitude via the prevention of the interference of rear wheel steering control at an attitude control process by making judgement as to whether the process is under way, and restraining the rear wheel steering control when the progress of the process is identified. SOLUTION: An SCS (supervision and control system for attitude) controller 5 has a rear wheel steering control part to control the steering or rear wheels 21RR and 21RL, depending on a yaw rate ψ' or the like detected with a yaw rate sensor 8. Also, when yaw rate feedback control is made during the control of the attitude, the yaw rate ψ' largely changes, due to the attitude control. As a result, the rear wheel steering control causes the rear wheels 21RR and 21RL to violently move, and the attitude control cannot be made. When the SCS controller 5 identifies that the attitude control is under way, therefore, a rear wheel steering angle θR is kept at and fixed to zero. Consequently, the same status as in the case of two-wheel steering occurs, and the attitude can be properly controlled. In addition, the attitude of a vehicle can be turned in a desired direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle attitude control for controlling a turning posture of a vehicle so as to converge in a target traveling direction by independently applying a braking force to front, rear, left and right wheels of the vehicle. The device belongs to the technical field of a device that performs steering control of rear wheels.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Unexamined Patent Publication No.
As shown in the publication, the vehicle is configured so that braking force can be individually applied to each of the front, rear, left, and right wheels of the vehicle, and the braking force is applied to each of the wheels independently, so that the vehicle 2. Description of the Related Art There is known a posture control device that controls a turning posture of a vehicle by applying a yaw moment. In such a posture control device, a vehicle state quantity representing a turning posture of the vehicle in a traveling direction such as a yaw rate is detected, and each detected vehicle state quantity is converged to a target vehicle state quantity corresponding to the target traveling direction. By applying a braking force to the wheels, a yaw moment is applied to the vehicle to control the turning posture of the vehicle. This control prevents the vehicle from spinning or drifting out.

[0003] On the other hand, a steering device that controls the turning of the rear wheels according to the front wheel steering angle or the front wheel steering angle and the vehicle speed, or as disclosed in Japanese Patent Laid-Open No. 6-107197, for example. 2. Description of the Related Art A steering device that controls turning of a rear wheel according to a yaw rate or the like in addition to an angle and a vehicle speed is known.

[0004]

By the way, when the attitude control is performed in the vehicle that performs the rear wheel steering control (4WS control) as described above, it is considered that the attitude control and the 4WS control are performed independently. Can be However, if they are controlled independently, the vehicle speed and the yaw rate change during the attitude control, so the 4WS control is performed according to the changed vehicle speed and the yaw rate, and the rear wheel steering angle changes. . For this reason, the vehicle may move unexpectedly, making it difficult to control the posture and giving the driver anxiety.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to devise a rear-wheel steering control during a posture control as a vehicle posture control device that performs 4WS control. Accordingly, it is to prevent the interference of the 4WS control during the posture control and to surely perform the posture control.

[0006]

In order to achieve the above object, according to the present invention, it is determined whether or not the posture control is being performed, and when it is determined that the posture control is being performed, the rear wheel steering control is suppressed. I did it.

More specifically, according to the first aspect of the present invention, a braking means configured to be capable of individually applying a braking force to each of the front, rear, left and right wheels of the vehicle, and controlling the operation of the braking means to control each of the above-mentioned respective wheels. Attitude control of a vehicle including attitude control means for controlling the turning attitude of the vehicle by independently applying braking force to the wheels, and rear wheel steering control means for steering control of the rear wheels according to the vehicle state Assume the device.

The attitude control-in-progress determining means for determining whether or not the attitude control is being performed by the attitude control means, and the rear-wheel steering control when the attitude control-in-progress determination means determines that the attitude control is being performed. Rear wheel turning suppression means for suppressing rear wheel turning control by the means.

As a result, the rear wheel steering control is suppressed during the attitude control, so that the rear wheel steering angle hardly changes even if the vehicle speed or the yaw rate changes due to the attitude control. For this reason, even if the rear wheel steering control is performed, the vehicle can be turned in the direction in which the attitude of the vehicle is desired. Therefore, it is possible to prevent the interference of the rear wheel steering control during the posture control and to surely perform the posture control.

According to a second aspect of the present invention, in the first aspect of the invention, the rear wheel turning suppressing means is configured to set the rear wheel steering angle to zero.

According to the present invention, when it is determined that the attitude control is being performed, the rear wheel steering angle is set to 0, and the state is fixed as it is. For this reason, the state becomes the same as the two-wheel steering, so that the posture can be reliably controlled. Therefore, a specific configuration of the rear wheel turning suppression means can be easily obtained.

According to a third aspect of the present invention, in the first aspect of the invention, the rear wheel turning control means determines a turning ratio of the rear wheel steering angle to the front wheel steering angle based on a vehicle state, and determines the turning ratio based on the vehicle state. The rear wheel turning suppression means is configured to fix the turning ratio to the turning ratio when the attitude control is being performed by the attitude control determination means. It is assumed to be configured as

As a result, the turning ratio determined based on the vehicle state such as the vehicle speed and the yaw rate is fixed to the turning ratio when it is determined that the attitude control is being performed.
It changes in proportion to only the front wheel steering angle regardless of the vehicle speed or yaw rate. For this reason, during the attitude control, the rear wheels are merely steered while maintaining a certain relationship with the front wheels in accordance with the steering operation of the driver, so that the motion of the vehicle can be predicted. Therefore, the posture control can be performed stably.

According to a fourth aspect of the present invention, in the first aspect of the invention, the rear wheel turning control means is configured to control turning of the rear wheels in accordance with the yaw rate generated in the vehicle. It is assumed that the rear wheel turning control means is configured to reduce the yaw rate sensitivity when turning control of the rear wheels is performed according to the yaw rate.

That is, since the yaw rate is particularly likely to change greatly by the attitude control, if the rear wheel steering control is performed in accordance with the yaw rate during the attitude control, the rear wheel steering angle frequently changes, and the vehicle attitude becomes very poor. Become stable. However, in the present invention, during the attitude control, the yaw rate sensitivity at the time of performing the steering control of the rear wheels is reduced, so that the change in the rear wheel steering angle is reduced, and the instability of the attitude can be prevented. On the other hand, when the attitude control is not being performed, the rear wheel turning control is performed in accordance with the yaw rate, so that the turning performance and the directional stability during running of the vehicle can be improved. Therefore, it is possible to prevent the posture control from becoming unstable due to the rear wheel turning control, while maintaining the effect of turning and controlling the rear wheels according to the yaw rate.

According to a fifth aspect of the present invention, in the first aspect of the invention, the rear wheel turning control means is configured to control turning of the rear wheels in accordance with the yaw rate and the vehicle speed generated in the vehicle. It is assumed that the rear wheel steering control means is configured to perform steering control of the rear wheels according to the vehicle speed.

In this manner, when the attitude control is not being performed, the rear wheel steering control is performed in accordance with the yaw rate and the vehicle speed. Can be improved. On the other hand, during the attitude control, the yaw rate is not added to the rear wheel steering control, and the rear wheels are controlled according to the vehicle speed. At this time, since the vehicle speed does not change as much as the yaw rate due to the attitude control, the influence on the attitude control can be reduced even if the rear wheel steering control is performed. Therefore, the same function and effect as the fourth aspect of the invention can be obtained.

According to a sixth aspect of the present invention, in the first aspect of the invention, the rear wheel turning suppression means fixes the rear wheel steering angle to the steering angle when the attitude control determination means determines that the attitude control is being performed. It is assumed to be configured to

As a result, if it is determined that the posture control is being performed, the rear wheels completely stop moving from that time, so that the movement of the rear wheels does not affect the posture control at all.
Therefore, the attitude control can be further stabilized.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1)-Overall configuration-Fig. 1 shows a vehicle 1 to which a vehicle attitude control device (Stability Control System) according to Embodiment 1 of the present invention is applied. , 21FL, 21
4 sets of hydraulic brakes individually arranged in RR and 21RL, 3 is a pressurizing unit for supplying pressurized liquid to each of these brakes 2, 4 is a pressurized liquid supplied from this pressurized unit 3 , And a hydraulic unit (hereinafter simply referred to as HU) for distributing and supplying the brakes 2 to each of the above-mentioned brakes 2, and these brakes 2, 2,..., The pressurizing unit 3 and the HU 4 constitute a braking means. Reference numeral 5 denotes an SCS controller as attitude control means for controlling the operation of each brake 2 via the pressurizing unit 3 and the HU 4;
Are wheel speed sensors for detecting the wheel speeds of the respective wheels 21, 7 are lateral G sensors for detecting a lateral acceleration y ″ acting on the vehicle 1, and 8 are acting on the vehicle 1. A yaw rate sensor as a yaw rate detecting means for detecting the present yaw rate ψ ', 9 is a steering angle θH
(A front wheel steering angle θF). In addition, 1
0 is a master cylinder, 11 is an engine, 12 is an automatic transmission (AT), and 13 is an EGI controller that adjusts the fuel injection amount according to the rotation speed of the engine 11, the amount of intake air, and the like.

As shown in FIG. 2, the brakes 2, 2... Of the right front wheel 21FR and the brake 2 of the left rear wheel 21RL are connected to the master cylinder 10 via a first hydraulic line 22a. On the other hand, the brake 2 of the left front wheel 21FL and the brake 2 of the right rear wheel 21RR are connected to the master cylinder 10 by a second hydraulic line 22b different from the first hydraulic line 22a. Two independent brake systems of the piping type are configured. Then, the wheels 21FR, 21FL,.
Is applied with a braking force.

The pressurizing unit 3 comprises the first and second
Hydraulic pumps 31a, 31b connected to the hydraulic lines 22a, 22b, respectively, and these hydraulic pumps 31a, 31b
b and cut valves 32a and 32b respectively provided in the first and second hydraulic lines 22a and 22b so that the master cylinder 10 can be connected and disconnected, and the cut valves 32a and 32b and the master cylinder 10 And a hydraulic pressure sensor 33 for detecting the hydraulic pressure between the two. And
The cut valves 32a and 32b are closed in response to a command from the SCS controller 5, whereby the hydraulic fluid discharged from the hydraulic pumps 31a and 31b is transferred via the HU4 regardless of the brake operation by the driver. Are supplied to the brakes 2, 2,.
As shown in FIG. 2, the HU 4 is provided with pressurizing valves 41, 41,... For pressurizing the brakes 2 with pressurized liquid supplied via the first hydraulic line 22a or the second hydraulic line 22b.
, And pressure reducing valves 43 connected to the reservoir tank 42 to reduce the pressure. The opening degree of each of the pressurizing valve 41 and each of the pressure reducing valves 43 is adjusted to increase or decrease according to a command from the SCS controller 5, so that the hydraulic pressure applied to each of the brakes 2 is increased or decreased, and the braking force is increased or decreased. It is configured to be changed.

The SCS controller 5 controls the operation of the pressurizing unit 3 and the HU 4 to independently apply a braking force to the front, rear, left and right wheels 21 to impart a required yaw moment to the vehicle 1. Thereby, the turning posture of the vehicle 1 is controlled so as to converge toward the target traveling direction. Specifically, the SCS controller 5
As shown in FIG. 3, the vehicle includes a state quantity calculation unit 51, a target state quantity calculation unit 52, a control intervention determination unit 53, a yaw rate control unit 54, and a sideslip angle control unit 55. The turning posture of the vehicle 1 is determined based on input signals from the speed sensors 6, 6,..., The lateral G sensor 7, the yaw rate sensor 8, and the steering angle sensor 9, and the pressure unit 3 and the HU 4 It is configured to perform operation control (SCS control). Further, the SCS controller 5
Detects a driver's brake operation based on an input signal from the hydraulic pressure sensor 33, and controls the operation of the pressurizing unit 3 and the HU 4 in response to the brake operation.

The state quantity calculation unit 51 is configured to determine the position of the vehicle 1 with respect to the traveling direction of the vehicle 1 based on the input signals from the wheel speed sensors 6, 6,..., The lateral G sensor 7, the yaw rate sensor 8, and the steering angle sensor 9. As the vehicle state quantity representing the turning posture,
The vehicle side slip angle β and the vehicle speed Vscs generated in the vehicle 1 are configured to be detected by calculation, and the target state amount calculation unit 52 similarly calculates the target side slip angle corresponding to the target travel direction. It is configured to calculate βTR and target yaw rate ψ′TR. Further, the control intervention determination unit 53 determines whether the slip angle deviation between the detected sideslip angle β and the target sideslip angle βTR and the detected yaw rate ψ ′ detected by the yaw rate sensor 8 and the target yaw rate ψ′TR. The yaw rate deviation amount is calculated, and the SCS control intervention determination is performed based on these sideslip angle deviation amount and yaw rate deviation amount.

The yaw rate control unit 54 applies a relatively small yaw moment to the vehicle 1 so that the detected yaw rate ψ ′ converges to the target yaw rate ψ′TR, thereby changing the vehicle attitude by the driver's driving operation (mainly, steering operation). The yaw rate control is performed so as to smoothly change to follow the steering angle), and the side slip angle control unit 55 applies a relatively large yaw moment to the vehicle 1 to thereby control the vehicle side slip angle β. Is the target sideslip angle β
The skid angle control for quickly correcting the turning posture of the vehicle 1 so as to converge to TR is performed.

As will be described later, the SCS controller 5 controls the rear wheels 21R according to the detected yaw rate ψ 'and the like.
A rear wheel turning control unit 56 (rear wheel turning control means) for performing turning control (4WS control) of R and 21RL is provided.

The SCS controller 5 has an SCS
In addition to control and 4WS control, well-known ABS (An
ti-Skid Brake System) control and TCS (Traction Con
trolSystem) also controls the ABS
Is a system for limiting the braking force applied to the wheels 21FR, 21FL,... In order to prevent the brake lock of the wheels 21FR, 21FL,. This is a system that limits the slip and prevents those slips.

FIG. 4 shows an outline of the basic control by the SCS controller 5. In this basic control, the driver first operates the vehicle 1.
Get on the ignition key and turn on the ignition key.
In step SA1, initialization of the SCS controller 5 and the EGI controller 13 is performed, and the calculated values and the like stored in the previous processing are cleared. In step SA2, after the origin correction of the wheel speed sensors 6, 6,... Is performed, signal input to the SCS controller 5 is performed from each of these sensors, and based on these input signals, the vehicle A common vehicle state quantity such as vehicle speed, vehicle deceleration, and vehicle speed at each wheel position is calculated.

Subsequently, an SCS control operation is performed in step SA4. That is, in step SA41, the SCS vehicle speed Vscs, the vehicle side slip angle β, the wheel slip ratio and slip angle of each wheel, the vertical load of each wheel, the tire load factor, and the road surface friction coefficient μ are calculated. The yaw rate ψ'TR and the target side slip angle βTR are calculated. Then, in step SA43, an intervention is determined for the yaw rate control or the side slip angle control based on the above calculation result. This step S
In A44, the wheels 21FR, 21FL,.
And the braking force to be applied to each of the selected wheels 21 is calculated. Then, based on the calculated braking force, in step SA45, the control output amount to the pressurizing unit 3 and the HU4, that is, the pressurizing valve 4 of each brake 2
, And the respective valve openings of the pressure reducing valves 43, 43,... Are calculated.

Further, in step SA5, a control target value and a control output amount necessary for the ABS control are calculated, and in step S5
In A6, a control target value and a control output amount required for the TCS control are calculated, and then, in step SA7, the respective calculation results of the ABS control, the TCS control, and the SCS control are arbitrated by a predetermined method, and the pressurization is performed. The control output amount to the unit 3 and the HU 4 is determined. Then, in step SA8, the pressure units 3 and HU4 are operated to control the degree of opening of each of the pressure valves 41 and the pressure reduction valves 43.
The brakes 2, 2, ... of the wheels 21FR, 21FL ...
Control the hydraulic pressure supplied to the wheels 21FR, 21FL
The required braking force is applied to. Finally, step SA9
Perform a fail-safe determination as to whether or not the wheel speed sensors 6, 6,... And the pressurizing unit 3 are operating normally, and return.

In the above flow chart, step SA41 corresponds to the state quantity calculation section 51, SA42 corresponds to the target state quantity calculation section 52, step SA43 corresponds to the control intervention determination section 53, and step SA44 and step SA45 correspond to each other. , The yaw rate control unit 54 and the sideslip angle control unit 55.

-Description of SCS control calculation- The details of the SCS control calculation in step SA4 will be described below with reference to FIGS. Note that the ABS control calculation in step SA5 and the TC control in step SA6
Since the S control calculation is well known, its description is omitted.

FIG. 5 shows the vehicle speed Vscs, the vehicle side slip angle β, the vertical load, the wheel slip ratio, the wheel slip angle, the tire load ratio, and the road surface friction coefficient μ obtained by the state quantity calculator 51 in step SA41 in FIG. The calculation and the calculation of the target side slip angle βTR and the target yaw rate ψ′TR by the target state quantity calculation unit 52 in step SA42 of FIG. That is, in step SB2, the wheel speed v1 of the wheel 21FR, the wheel speed v2 of the wheel 21FL, the wheel speed v3 of the wheel 21RR, the wheel speed v4 of the wheel 21RL, the lateral acceleration y ″ of the vehicle 1, and the yaw rate of the vehicle 1 'And the steering angle θH of the steering wheel.
The vehicle speed Vscs is calculated based on the wheel speeds v1, v2,..., And in step SB6, the wheel speeds v1, v2,.
The vertical weight at each wheel position is calculated based on the vehicle speed Vscs, the wheel speeds v1, v2,..., And the lateral acceleration y ″. The vehicle side slip angle β is calculated based on the yaw rate ψ ′ and the steering angle θH.

Subsequently, in step SB10, the slip ratio of each wheel 21 is determined based on the wheel speeds v1, v2,..., The vehicle speed Vscs, the vehicle side slip angle β, the yaw rate ψ ', and the steering angle θH. In step SB12, based on the vertical load at each wheel position and the slip ratio and the slip angle, the wheels 21FR,
For each of 21FL, ..., tires 23, 23, ...
Is calculated, which is the ratio of the current gripping force to the total gripping force that can be exerted. Then, Step SB1
In step SB16, a road friction coefficient μ is calculated based on the load factor and the lateral acceleration y ″. In step SB16, the road friction coefficient μ, the vehicle speed Vscs, and the steering angle θH are calculated.
Target yaw rate ψ′TR and target sideslip angle βTR
Is calculated.

FIG. 6 shows the SCS control after the SCS control intervention determination in step SA43 of FIG. 4. In step SB18, the yaw rate deviation amount (| ψ′TR−) between the yaw rate ψ ′ and the target yaw rate ψ′TR ψ '|), and
The side slip angle deviation amount (| βTR−β |) between the vehicle side slip angle β and the target side slip angle βTR is determined by the yaw rate control unit 54 in advance to determine the yaw rate control intervention. Compare with thresholds K1 and K2. If the yaw rate deviation amount is equal to or greater than the intervention determination threshold value K1 or the side slip angle deviation amount is equal to or greater than the intervention determination threshold value K2, the deviation of the vehicle attitude with respect to the target traveling direction increases. Yes S
It is determined that CS control intervention is necessary, and step SB20 is performed.
On the other hand, if the yaw rate deviation amount is smaller than the yaw rate control intervention determination threshold value K1 and the side slip angle deviation amount is smaller than the intervention determination threshold value K2, the SCS control It is determined that no intervention is necessary, and the process returns to step SB2.

Subsequently, in step SB20, the side slip angle deviation amount (| βTR−β |) is determined by the side slip angle control unit 55 to determine the side slip angle control intervention determined in advance for the side slip angle control intervention determination. Compare with the value K3 (K3> K2). If the side slip angle deviation is smaller than the intervention determination threshold value K3, the process proceeds to step SB22 to set the target yaw rate ψ'TR as the SCS control target value, and then proceeds to step SB24 to execute the actual SCS control. Is calculated mainly based on the yaw rate deviation amount (| ψ′TR−ψ ′ |). That is, while it is determined that the change in the vehicle attitude is relatively small and in a stable state (SB20), the vehicle is controlled so that the yaw rate ψ ′ of the vehicle 1 converges to the target yaw rate ψ′TR corresponding to the driving operation of the driver. A relatively small yaw moment is applied to the motor 1 (SB22, 24), whereby yaw rate control for smoothly changing the vehicle posture so as to follow the driving operation of the driver is performed.

On the other hand, if the side slip angle deviation amount (| βTR−β |) is equal to or larger than the side slip angle control intervention determination threshold value K3 in step SB20, the process proceeds to step SB26, where the target side slip angle βTR is subjected to SCS control. The target value is set as the target value, and thereafter, the process proceeds to step SB28, where the SCS control amount βamt actually used for the SCS control is set to the side slip angle deviation amount (| βTR−
β |). That is, when it is determined that the vehicle attitude is largely collapsed (SB20), the vehicle 1 is controlled so that the vehicle sideslip angle β converges to the target sideslip angle βTR.
A relatively large yaw moment is applied to the vehicle (SBs 26 and 28), whereby the side slip angle control for quickly correcting the vehicle attitude is performed.

Then, in step SB30 following step SB24 or step SB28, it is determined whether or not a failure has occurred in the pressurizing unit 3 or the HU4. If it is determined that a failure has occurred, the process proceeds to step SB32. The SCS control is stopped and the process returns. On the other hand, if the failure is not determined in step SB30, the process proceeds to step S30.
Proceeding to B34, the above SCS control, ABS control and TC
The calculation results of the S control are arbitrated by a predetermined method. An outline of the arbitration will be described. If the ABS control is performed when the SCS control is performed, the AB control is performed.
By correcting the S control amount based on the SCS control amount ψ′amt or βamt, the SCS control is performed while giving priority to the ABS control. When the SCS control is performed, the TCS control is performed. If so, its T
The operation of the pressurizing unit 3 and the HU 4 for CS control is stopped, and SCS control is performed.

Subsequently, at step SB36, SC
Wheels 21FR and 21FL that apply braking force for S control,
... and select these wheels 21FR, 21FL,
Are calculated based on the SCS control amount ψ′amt or βamt. If the yaw rate control increases the yaw rate ψ ′ of the vehicle 1 clockwise in the yaw rate control, and attempts to turn the turning posture of the vehicle 1 toward the right side in the sideslip angle control, the wheel selection and the calculation of the braking force will be outlined. In this case, the SCS control amount ψ'amt is applied to the right front wheel 21FR or the right front and rear wheels 21FR and 21RR.
Alternatively, the vehicle 1 is provided by applying a braking force according to βamt.
The clockwise yaw moment is applied to the motor. Conversely, when the yaw rate ψ ′ of the vehicle 1 is increased counterclockwise, and when the turning posture of the vehicle 1 is directed to the left side, the left front wheel 21FL or the left front wheel 2FL
For 1FL and 21RL, the SCS control amount ψ'amt or β
A counterclockwise yaw moment is applied to the vehicle 1 by applying a braking force according to amt. And those selected wheels 21FR, 21FL, ...
, The control output amounts to the pressurizing unit 3 and the HU 4 for applying the desired braking force, ie, the pressurizing valves 41, 41,. Step S for each valve opening etc.
Computation is performed in B38, and the computed control output amounts are outputted to the pressurizing unit 3 and HU4 in step SB40, and the SCS control is executed, and the process returns.

FIG. 7 schematically shows the configuration of the 4WS control system.
A front wheel steering mechanism 16 that steers FR and 21FL in accordance with the steering angle θH of the steering wheel, and a rear wheel steering mechanism 17 that steers rear wheels 21RR and 21RL independently of the front wheels 21FR and 21FL. The rear wheel steering mechanism 17 is connected to the S
It is controlled by the rear wheel turning control unit 56 of the CS controller 5.

The rear wheel steering mechanism 17 includes a driving means such as a motor (not shown).
The rear wheels 21RR and 21RL are driven by the front wheel steering mechanism 1 by being operated and controlled in response to a control signal from the S controller 5.
The steering is performed so as to have a predetermined target rear wheel steering angle TGθR which is determined by a relationship between the front wheel steering angle θF input from 6 and a predetermined steering ratio (the ratio of the rear wheel steering angle θR to the front wheel steering angle θF). It has become. The rear wheel turning control unit 56 of the SCS controller 5 sends the vehicle speed V from the vehicle speed sensor 18 to
The rear wheel steering angle θR is input from the rear wheel steering angle sensor 19, the yaw rate ψ 'is input from the yaw rate sensor 8, and the front wheel steering angle θF is input from the steering angle sensor 9.

The rear wheel turning control section 56 controls the operation of the rear wheel turning mechanism 17 to thereby control the rear wheel turning angle θR.
The steering control of the front wheel is carried out, and the detection signals of the vehicle speed V, the yaw rate ψ 'and the front wheel steering angle θF, and the front wheel steering angle speed (front wheel steering angle change rate) obtained by differentiating the front wheel steering angle θF are obtained. ) The steering control of the rear wheels 21RR and 21RL is mainly performed by the feedback control based on the yaw rate ψ ', using the signal calculation value of θ'F2 and the control parameter indicating the vehicle state.

The 4WS control by the rear wheel turning control unit 56 will be described. The target rear wheel steering angle TGθR is calculated by the following equation based on the above control parameters, and the rear wheel steering angle θR becomes the target rear wheel steering angle TGθR. The rear wheel steering mechanism 17
Operation control.

(Equation 1)

In the above equation (1), the value in parentheses on the right side is for calculating and determining the target turning ratio based on the control parameters. By multiplying the target turning ratio by the front wheel turning angle θF, the target rear wheel turning angle is obtained. TGθR is calculated. The first term in the right parenthesis in the above equation is a steering angle correction term, the second term is a yaw rate correction term, the third term is a steering angular velocity correction term, and the fourth term is a rear wheel rotation according to the vehicle speed. This is a vehicle speed sensitive term that is a base when performing rudder control. By setting the target rear wheel steering angle TGθR in this way, when the front wheels 21FR and 21FL are steered from the straight running state based on the vehicle speed sensitive rear wheel steering control, the rear wheels 21RR are initially turned. , 21RL are steered to the opposite phase side in which the directions are opposite to those of the front wheels 21FR, 21FL, and the turning performance is increased.
A control (phase reversal control) is performed to steer to the same phase side where the direction is the same as that of 21FL to achieve directional stability (phase inversion control). It has become.

In the above equation 1, G1, G2, G3,
G4 is a constant, and other variables are calculated as follows based on the vehicle speed V, the yaw rate ψ ', and the front wheel steering angle θF as shown in FIG.

The variables f 1 (V), f 2 (V),
f3 (V) and f4 (V) are vehicle speed-sensitive gains, respectively, and are maps m10, m5, and m1 based on the vehicle speed V.
3 and m1 respectively.

Next, the variable θR.ST of the first term on the right side is a steering angle correction value, which is calculated as follows. First, in order to provide a dead zone in the small steering angle area of the front wheel steering angle θF, an offset is added by using the map m8 to set the front wheel steering angle to θF1, and then, by using the map m11, hysteresis is added to the θF1 to prevent hunting. And θF2
The variable θR.ST is mapped to a map m9 based on the θF2.
It is calculated by:

The variable θR.YAW of the second term on the right side is a yaw rate correction value. After the yaw rate ψ ′ is offset by マ ッ プ ′ 1 by using the map m2 in the same manner as described above, the θ ′ is obtained by the map m3. Ψ ′ with hysteresis added to 1
2 and is calculated by the map m4. The variable K2 (θF2) of the second term on the right side is a steering angle sensitive gain, which is calculated by the map m6 based on θF2 obtained in the map m11. Furthermore, the variable J2 of the second term on the right side
(Θ′F2) is a steering angular velocity sensitive gain,
Map m based on θ'F2 obtained by differentiating θF2 obtained in step 11.
7 is calculated.

The variable θR.STD of the third term on the right side is a steering angular velocity correction value, and is calculated by the map m12 based on θ′F2 obtained by differentiating θF2 obtained by the map m11. Also,
The variable K3 (θF2) of the third term on the right side is a steering angle sensitive gain, which is calculated from θF2 obtained in map m11 by map m14.

FIG. 9 shows a control procedure in the rear wheel steering control unit 56 of the SCS controller 5. During the SCS control, the rear wheel steering angle θR is controlled to be the target rear wheel steering angle TGθR. Instead, it is set to 0.
That is, first, in step SC1, it is determined whether or not the SCS control is being performed. It is determined whether the SCS control is being performed or not after the SCS control intervention is once performed in the above SCS control procedure (after the determination in step SB18 is made YES).
The determination is made based on whether the S control intervention is not performed (the determination in step SB18 becomes NO). Specifically, the SCS control flag is set to 1 only during the above period, and the determination is made based on whether the SCS control flag is 1 or not. When the determination in step SC1 is NO, the process proceeds to step SC2, and as described above, the normal 4W
Perform S control and return. On the other hand, step SC
If the determination of 1 is YES, the process proceeds to step SC3, where the rear wheel steering angle θR is set to 0, and the process returns.

In the control procedure of the rear wheel turning control section 56, the attitude control determination means 6 determines at step SC1 whether or not the attitude control by the SCS controller 5 is being performed.
1 and a rear wheel turning suppression means 62 for suppressing the 4WS control by the rear wheel turning control unit 56 when the posture control is being performed by the posture control determination means 61 in step SC3. ing.

Therefore, in the first embodiment, when it is determined that the attitude control is not being performed, the normal 4WS control is performed and the rear wheel steering control is performed by the feedback control based on the yaw rate ψ ′. The turning property and the directional stability can be improved. On the other hand, if the yaw rate feedback control is performed during the attitude control, the yaw rate ψ ′ is greatly changed by the attitude control, and the rear wheels 21 RR and 21 RL move violently by the rear wheel steering control, so that the attitude cannot be controlled. . However, in the first embodiment, if it is determined that the posture control is being performed, the rear wheel steering angle θR is set to 0 and fixed in that state. As a result, the state becomes the same as that of two-wheel steering, so that the attitude can be reliably controlled, and the vehicle 1 can be turned in the direction in which the attitude is desired. Therefore, while maintaining the effect of steering control of the rear wheels 21RR and 21RL in accordance with the yaw rate ψ ', the attitude control can be reliably performed by preventing the interference of the 4WS control during the attitude control.

(Embodiment 2) FIG. 10 shows Embodiment 2 of the present invention, in which the processing (step SC3) when it is determined that the posture control is being performed is different from that of Embodiment 1 above (note that each of the following embodiments) In the embodiment, only the step SC3 is different, and the other steps are the same, so that the description thereof is omitted.) That is, when the determination of whether or not the posture control is being performed in step SC1 is YES, the steering ratio is fixed to the steering ratio when it is determined that the posture control is being performed.

Therefore, in the second embodiment, when it is determined that the attitude control is being performed, the steering ratio is fixed as it is, and therefore the rear wheel steering angle θR can be changed regardless of the vehicle speed V, the yaw rate ψ ', etc. It changes in proportion to only the steering angle θF. For this reason, during the attitude control, the rear wheels 21FR and 21FL maintain a fixed relationship with the front wheels 21FR and 21FL in accordance with the driver's steering operation.
Since only RR and 21RL are steered, the motion of the vehicle 1 can be predicted. Therefore, the posture control can be performed stably.

(Embodiment 3) FIG. 11 shows Embodiment 3 of the present invention, in which the rear wheel steering control unit 56 controls the rear wheels 21RR and 21RL to steer when it is determined that the attitude control is being performed. The yaw rate sensitivity is reduced. That is, during the attitude control, the yaw rate correction value θR.YAW, which is the variable of the second term on the right side of the above equation 1, is made smaller than that in the normal 4WS control.

Therefore, in the third embodiment, during the attitude control, the influence on the rear wheel steering control of the yaw rate ψ ′, which is particularly greatly changed by the attitude control, is reduced. It does not change much,
Posture instability can be prevented. Therefore, 4W
It is possible to prevent the posture control from becoming unstable due to the S control.

(Embodiment 4) FIG. 12 shows Embodiment 4 of the present invention, in which the turning ratio is determined based on only the vehicle speed V when it is determined that the posture control is being performed. . That is, the constants G1 to G3 in the above equation 1 are set to 0, and the right side thereof is only the fourth vehicle speed sensitive term. Accordingly, when it is determined that the attitude control is not being performed, the front wheel steering angle θF and the steering ratio determined based on the vehicle speed V, the yaw rate ψ ′, the front wheel steering angle θF, and the front wheel steering angular velocity θ′F2 are determined. While it is determined that the attitude control is not being performed, the 4WS control is performed according to the front wheel steering angle θF and the steering ratio determined based only on the vehicle speed V.

Therefore, in the fourth embodiment, during the attitude control, the yaw rate ψ 'is not added to the 4WS control, and the rear wheels are determined according to the front wheel steering angle θF and the steering ratio determined based only on the vehicle speed V. 21RR and 21RL are controlled. At this time,
Since the vehicle speed V does not change as much as the yaw rate ψ 'by the attitude control, the movement of the rear wheels 21RR and 21RL can be reduced. Therefore, the same function and effect as those of the third embodiment can be obtained.

(Fifth Embodiment) FIG. 13 shows a fifth embodiment of the present invention. When it is determined that the attitude control is being performed, the steering angle when the rear wheel steering angle θR is determined to be the attitude control is determined. It is designed to be fixed to a corner.

Therefore, in the fifth embodiment, when it is determined that the posture control is being performed, the rear wheels 21RR, 21RR,
21RL is fixed as it is and does not move completely. For this reason, the movement of the rear wheels 21RR and 21RL does not affect the attitude control at all, and the vehicle 1 can be reliably turned in the direction in which the attitude is desired. Therefore, 4WS during attitude control
Control interference can be completely prevented, and posture control can be performed more stably than in the above embodiments.

[0061]

As described above, according to the first aspect of the present invention, the attitude control means for controlling the turning attitude of the vehicle by independently applying the braking force to each wheel, and at least the front wheel steering angle And determining whether or not the vehicle is under attitude control. When it is determined that the vehicle is under attitude control, rear wheel steering is performed. By suppressing the control, it is possible to prevent the interference of the rear wheel steering control during the posture control and to execute the posture control reliably.

According to the second aspect of the present invention, when it is determined that the attitude control is being performed, the rear wheel steering angle is set to 0, so that a specific configuration of the rear wheel steering suppression means can be easily obtained. be able to.

According to the third aspect of the invention, when it is determined that the attitude control is being performed, the steering ratio is fixed to the steering ratio at that time, thereby stabilizing the attitude control. Can be.

According to the fourth aspect of the present invention, when it is determined that the attitude control is being performed, the yaw rate sensitivity when turning control of the rear wheels according to the yaw rate is reduced. In the invention of claim 5, when it is determined that the posture control is being performed, the turning control of the rear wheels is performed according to the vehicle speed. Therefore, according to these inventions, it is possible to prevent instability of the attitude control by the rear wheel turning control while maintaining the effect of the rear wheel turning control in consideration of the yaw rate.

According to the sixth aspect of the invention, when it is determined that the attitude control is being performed, the rear wheel steering angle is fixed to the steering angle at that time, thereby further stabilizing the attitude control. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a vehicle to which a vehicle attitude control device according to a first embodiment of the present invention is applied.

FIG. 2 is a diagram showing a hydraulic system of a brake.

FIG. 3 is a block diagram illustrating a configuration of an SCS controller.

FIG. 4 is a flowchart showing an outline of an SCS control procedure by the SCS controller.

FIG. 5 is a flowchart illustrating a control procedure in a state quantity calculation unit and a target state quantity calculation unit.

FIG. 6 is a flowchart showing details of an SCS control procedure after the control intervention determination by the SCS controller.

FIG. 7 is a plan view schematically showing a configuration of a 4WS control system.

FIG. 8 is a control block diagram illustrating 4WS control.

FIG. 9 is a flowchart illustrating a control procedure in a rear wheel steering control unit.

FIG. 10 is a diagram corresponding to FIG. 9 showing the second embodiment.

FIG. 11 is a diagram corresponding to FIG. 9, showing the third embodiment.

FIG. 12 is a diagram corresponding to FIG. 9 showing the fourth embodiment.

FIG. 13 is a diagram corresponding to FIG. 9 showing the fifth embodiment.

[Explanation of symbols]

 Reference Signs List 1 vehicle 2 brake (braking means) 3 pressurizing unit (braking means) 4 hydraulic unit (braking means) 5 SCS controller (posture controlling means) 6 wheel speed sensor (vehicle state detecting means) 7 lateral G sensor (vehicle state detecting) Means) 8 yaw rate sensor (vehicle state detecting means) 9 steering angle sensor (vehicle state detecting means) 21FR, 21FL, 21RR, 21RL wheels 51 state quantity calculating section (vehicle state detecting means) 52 target state quantity calculating section 56 rear wheel steering Control unit (rear wheel turning control means) 61 SCS control determination means 62 rear wheel turning suppressing means β Vehicle side slip angle (vehicle state quantity) ψ ′ Yaw rate (vehicle state quantity) θF Front wheel steering angle θR Rear wheel steering angle V Vehicle speed

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI B62D 113: 00 137: 00 (72) Inventor Tetsuya Tachihata 3-1, Fuchi-machi, Shinchu, Aki-gun, Hiroshima Mazda Co., Ltd.

Claims (6)

[Claims] 1. A braking means configured to be capable of individually applying a braking force to each of front, rear, left and right wheels of a vehicle, and applying an independent braking force to each of the wheels by controlling the operation of the braking means. And a rear-wheel turning control means for turning and controlling the rear wheels according to the state of the vehicle. Attitude control determination means for determining whether the vehicle is in the middle position, and rear wheel steering for suppressing rear wheel steering control by the rear wheel steering control means when the attitude control determination means determines that attitude control is being performed. An attitude control device for a vehicle, comprising: a suppression unit. 2. The vehicle attitude control device according to claim 1, wherein the rear wheel turning suppression means is configured to set the rear wheel steering angle to zero. 3. The vehicle attitude control device according to claim 1, wherein the rear wheel steering control means determines a steering ratio of a rear wheel steering angle to a front wheel steering angle based on a vehicle state, and determines the steering ratio. The rear wheel turning suppression means is configured to fix the turning ratio to the turning ratio when the posture control determination unit determines that the posture control is being performed. An attitude control device for a vehicle, comprising: 4. The attitude control device for a vehicle according to claim 1, wherein the rear wheel turning control means is configured to control turning of the rear wheels in accordance with a yaw rate generated in the vehicle. An attitude control device for a vehicle, wherein the rear wheel steering control means is configured to reduce yaw rate sensitivity when steering control of rear wheels is performed according to yaw rate. 5. The vehicle attitude control device according to claim 1, wherein the rear wheel turning control means is configured to control turning of the rear wheels according to a yaw rate and a vehicle speed generated in the vehicle. Is a vehicle attitude control device, wherein the rear wheel steering control means is configured to perform steering control of rear wheels according to vehicle speed. 6. The attitude control device for a vehicle according to claim 1, wherein the rear wheel turning suppression means fixes the rear wheel steering angle to a steering angle when the attitude control determination means determines that the attitude control is being performed. An attitude control device for a vehicle, wherein