JPH07117655A - Vehicle attitude controller - Google Patents

Abstract

PURPOSE:To improve the stability of a vehicle by controlling the brake power distribution for the front and rear wheels so that the brake power increases on the front wheel side, when it is judged that the vehicle is in an unstable state and the yawing moment in the direction in which the vehicle leteral move ment state is stabilized by the front wheel lateral force is not generated. CONSTITUTION:The output signals of a stepping force sensor 11, optical speed sensor 13 for detecting the speed in the longitudinal and lateral directions of a vehicle, steering angle sensor 15, front wheel lateral acceleration speed sensor 16, etc., are inputted into a controller 9. The stability of the vehicle is judged accoring to the lateral movement state, and when it is judged that the vehicle is in an unstable state, the yawing moment of the vehicle is controlled by reducing the lateral force of the front wheel. In this control, only in the case where the yawing moment in the direction in which the leteral movement of the vehicle is stabilized according to the generation direction of the actual lateral acceleration speed generated by the atcual front wheel lateral force is not generated, the brake power distribution of the front and rear wheels is controlled so that the brake power increases on the front wheel side, and the lateral force of the front wheel is reduced, and the vehicle is stabilized.

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 system.

[0002]

2. Description of the Related Art Conventionally, as a vehicle attitude control device, a yaw rate feedback control type chassis control device is available. Further, Japanese Patent Laid-Open No. 62-299430 discloses a vehicle attitude control device that detects a side slip angle of a vehicle and distributes a driving force in the front and back so as to suppress the side slip angle within an allowable range.

[0003]

However, in the case of the chassis control device of the yaw rate feedback control system, it is possible to improve the steering stability of the vehicle by making the generated yaw rate follow the target yaw rate, but at a low μ road surface a high μ There is a problem in that it is difficult to set an appropriate target yaw rate due to the influence of the road surface μ, such that the driver's steering feeling is rather deteriorated by using the road surface target value. The target yaw rate calculated from the steering angle etc.
It may not always be the best vehicle behavior, and even if the yaw rate target value is not appropriate, if the yaw rate feedback control is executed to make the actual value uniformly follow the target value based on it, the attitude of the vehicle Make it difficult to fix.

On the other hand, in the one disclosed in the above-mentioned publication by the control according to the side slip angle, the driving force is distributed to the front and back so as to suppress the side slip angle to the allowable value, and the side slip angle is smaller than the allowable value. When it is judged that the vehicle becomes unstable and the vehicle becomes unstable, the driving force of the rear wheels is reduced to increase the lateral force of the rear wheels to improve the stability of the vehicle, and at the same time, the lateral force of the front wheels is increased by increasing the front wheel distribution. Is reduced. Such a chassis control device that controls the yawing moment of the vehicle by reducing the lateral force of the front wheels is good when the driver is steering in an unstable direction due to a panic condition or lack of skill, but In order to stabilize the vehicle, the steering is performed accurately, and the lateral force of the front wheels is controlled only in accordance with the sideslip angle even when the vehicle is in a stable direction.
Since the lateral force of the front wheels is reduced, it may take time for the vehicle to stabilize and the steering feeling of the driver may be deteriorated.

On the other hand, the present inventor has presumed that, when controlling the attitude of the vehicle, the steering state is detected and the yawing moment in the direction in which the lateral motion of the vehicle is stabilized is not generated by the lateral force of the front wheels. Only in this case, we have previously developed a method of performing control according to the sideslip angle. Although such a thing may be considered, it is difficult to estimate that the front wheel lateral force is acting in a stable direction when the vehicle is actually in a state near a spin in vehicle steering.

The present invention has been made in view of the above circumstances, and stabilizes the vehicle regardless of an uncertain driver's operation, and properly determines the driver's correct operation. Therefore, it is possible to utilize the operation, prevent the above-mentioned problems from occurring, cope with a wide range of vehicle traveling and driving situations, and improve the vehicle stability appropriately. The present invention aims to provide a vehicle attitude control device.

[0007]

According to the present invention, the following vehicle attitude control device is provided. That is, the wheel braking force control means capable of independently controlling the braking force of the wheels, the lateral motion state detecting means for detecting the lateral motion state of the vehicle, and the lateral acceleration on the front wheel axis of the vehicle are detected or estimated. Axial lateral acceleration detection means, vehicle stability determination means for determining vehicle stability according to the lateral motion state, and vehicle stability determination means for determining that the vehicle is unstable, and When it is determined by the signal from the acceleration detecting means that the yawing moment in the direction in which the lateral motion state of the vehicle is stabilized by the lateral force of the front wheels is not generated, the braking force control means distributes the braking force to the front and rear wheels. The vehicle attitude control device is provided with yawing / moment control means for controlling the vehicle so that the front wheel side becomes larger (FIG. 1). Further, in the above, the lateral movement state detecting means is a vehicle side slip angle detecting means, and the vehicle stability determining means includes the lateral movement state, vehicle speed, and steering angle of the vehicle. The vehicle attitude control device, characterized in that the stability of the vehicle is determined by comparison with the target lateral motion state calculated by the above, and the wheel braking force control means is such that the wheel speed is a predetermined slip ratio with respect to the vehicle body speed. The vehicle stability determining means determines that the vehicle is unstable, and a lateral motion state of the vehicle is generated by the front wheel lateral force based on a signal from the front axle lateral acceleration detecting means. If it is determined that the yawing moment in the stable direction is not generated, correct the wheel speed so that the front and rear wheels have a larger slip ratio and the rear wheels have a smaller slip ratio. Vehicle attitude control device and controls the power is provided.

[0008]

According to the vehicle attitude control device of the present invention, the wheel braking force control means capable of independently controlling the braking force of the wheels, the lateral motion state detecting means, the front axle lateral acceleration detecting means, the vehicle stability determining means, The yaw / moment control means is provided, the lateral motion state detection means detects the lateral motion state of the vehicle, and the front axle lateral acceleration detection means detects or estimates the lateral acceleration on the front wheel axle of the vehicle. The vehicle stability determining means determines the stability of the vehicle according to the lateral motion state, but the yawing / moment controlling means determines that the vehicle is unstable by the vehicle stability determining means, and When it is determined from the signal of the axial lateral acceleration detecting means that the yawing moment in the direction in which the lateral motion state of the vehicle is stabilized by the front wheel lateral force is not generated, the braking force control means performs The braking force distribution of the wheel is controlled so that the front wheel is increased.

Therefore, when it is judged that the vehicle is unstable and the yawing moment of the vehicle is controlled by reducing the lateral force of the front wheels, the actual lateral acceleration generated by the actual lateral force of the front wheels is also measured. It is possible to control the proper use properly considering it as a judgment factor, and the lateral movement of the vehicle is stabilized by looking at the lateral acceleration on the front wheel axis and the direction of the actual lateral acceleration generated by the actual front wheel lateral force. Only when it is detected that the yawing moment is not generated, the braking force distribution of the front and rear wheels is controlled so that the front wheel side becomes larger, and the lateral force of the front wheels is reduced to stabilize the vehicle. As a result, it is possible to stabilize the vehicle regardless of uncertain driver's operation, and to properly use the operation when the driver performs the correct operation and operates the vehicle in the stable direction by the steered front wheels. Therefore, the control for stabilizing the vehicle can be realized, the above-mentioned problems can be solved, and the vehicle stability can be effectively improved.

According to a second aspect of the present invention, the lateral motion state detecting means is a vehicle side slip angle detecting means, and in the third aspect, the vehicle stability determining means is a lateral motion state of the vehicle and the vehicle speed and The stability of the vehicle is judged by comparison with the target lateral motion state calculated from the steering angle. The lateral motion state detecting means and the vehicle stability judging means are respectively configured in this way, and the same as above. The vehicle attitude control device can be realized.

According to another aspect of the present invention, the wheel braking force control means controls the braking force so that the wheel speed has a predetermined slip ratio with respect to the vehicle body speed. Is judged to be unstable, and it is judged from the signal from the front-axis lateral acceleration detection means that the yaw moment in the direction in which the lateral motion state of the vehicle is stabilized by the front wheel lateral force is not generated. In order to control the braking force by correcting the wheel speed such that the front and rear wheels have a large slip ratio on the front wheels and the front and rear wheels have a small slip ratio, the vehicle attitude control device similar to that described above can be realized. You can

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a diagram showing the configuration of an embodiment of the vehicle attitude control device of the present invention. In this embodiment, the vehicle to be applied is capable of independently controlling the braking force (braking hydraulic pressure) of each of the front, rear, left and right wheels.

In the figure, 1L and 1R are left and right front wheels, and 2L and 2R are left and right rear wheels, respectively. Each wheel has a wheel cylinder (W / W / C) which applies a braking force (braking force) to each wheel by frictionally sandwiching the brake disk with the brake discs 3L, 3R, 4L, 4R and the supply of hydraulic pressure (hydraulic pressure).
C) 5L, 5R, 6L, 6R are provided, and when hydraulic pressure is supplied from the pressure servo unit (pressure control unit) 7 to each wheel cylinder of these brake units, each wheel is individually braked.

The pressure servo unit 7 constitutes a braking force control device together with a controller, which will be described later, including this, and adjusts the hydraulic pressure from the hydraulic pressure generation source 8 by an input control signal, and the wheel cylinders 5L, 5R of each wheel. , 6L, 6R
Controls the brake fluid pressure supplied to. Pressure servo unit 7
Is configured to include an actuator for each hydraulic pressure supply system (each channel) on the front and rear wheels.

As the actuator, for example, an actuator capable of controlling depressurization, holding, and pressure increase, which is also used for anti-skid control, can be used. In the pressure servo unit 7, the input hydraulic pressure command signal, specifically, the front wheel left hydraulic pressure command value P1 is provided by the hydraulic pressure control actuator of each supply system.
(S), front wheel right hydraulic pressure command value P2 (S), rear wheel left hydraulic pressure command value P3 (S), and rear wheel right hydraulic pressure command value P4 (S), respectively. The pressure of P4 shall be adjusted.

The above-mentioned respective signals to the pressure servo unit 7 are supplied from a controller 9, and the controller 9 is supplied with a signal from a pedaling force sensor 11 for detecting a pedaling force Fp of a brake petal 10, front and rear, left and right of the vehicle. Signal from the optical speed sensor 13 for detecting the directional speeds Vx and Vy, and the steering angle δ of the steering wheel (steering wheel) 14.
A signal from a steering angle sensor 15 for detecting the vehicle speed, a signal from a front axle lateral acceleration sensor 16 for detecting a lateral acceleration (lateral G) Ygf on the front wheel shaft, and the like are input to the vehicle.

The controller 9 is configured to include a microcomputer using an input detection circuit, an arithmetic processing circuit, a memory circuit for storing a control program executed by the arithmetic processing circuit and an arithmetic result, an output circuit, and the like. The processing circuit follows a program for controlling the brake fluid pressure based on predetermined input information. In this embodiment, basically, the braking force is controlled to control the yawing moment of the vehicle in order to stabilize the vehicle by controlling the distribution of the braking force in the front-rear direction. A target wheel cylinder pressure value (command value) is obtained as a control value, and a signal corresponding to that value is sent to the pressure servo unit 7.
As a result, the pressure servo unit 7 adjusts the hydraulic pressure from the hydraulic pressure generation source 8 so that the actual wheel cylinder pressure of the corresponding wheel matches the target hydraulic pressure, and supplies it to the corresponding wheel cylinder.

The controller 9 performs the yawing control of the vehicle by the front-rear distribution of the braking force control as described above. In that case, the controller 9 determines the stability of the vehicle according to the lateral motion state of the vehicle. In addition, in order to determine whether the operation of the front wheels that the driver is operating at that time will act in a direction that stabilizes the vehicle or not, in order to determine whether the operation is on the front wheel axle, The acceleration is also taken into consideration, and it is determined that the vehicle is unstable, and the lateral acceleration on the front wheel axis is detected, and the lateral movement of the vehicle is determined by the direction of the actual lateral acceleration generated by the actual front wheel lateral force. When it is determined that the yawing moment in the stable direction is not generated, the braking force control is executed so that the front wheel side increases the braking force distribution of the front and rear wheels when the scene concerned is hit based on the results of both of these determinations. None so that, to stabilize the vehicle. In this case, the signal from the front-axis lateral acceleration sensor 16 is used as information for determining the latter.

Preferably, the controller 9 detects the lateral motion state of the vehicle by detecting the side slip angle of the vehicle. Further, preferably, the vehicle stability can be determined by comparing the detected lateral motion state of the vehicle with a target lateral motion state calculated from the vehicle speed and the steering angle.

In the above, the signal from the speed sensor 13 is used as information for detecting the sideslip angle of the vehicle, and if the vehicle stability is judged as described above, the vehicle speed information used in that case. Also, the signal from the speed sensor 13 can be used. The signal from the steering angle sensor 15 is also used as steering angle information in that case.

FIG. 3 is a flowchart showing an example of a braking force control program executed by the controller 9. This processing is executed by a regular interrupt at regular time intervals by an operating system (not shown).

First, in step S100, the longitudinal speed Vx, the lateral speed Vy, the brake pedal force Fp, the steering angle δ, based on the signals from the sensors 11, 13, 15 and 16,
The lateral acceleration on the front wheel axis Ygf is read.

Next, in step S101, the sideslip angle β of the vehicle is calculated. In the present embodiment, it is assumed that this is calculated by the following equation from the front-rear velocity Vx and the left-right velocity Vy which are the sensor signals.

## EQU1 ## β = tan ^-1 (Vy / Vx) ≈Vy / Vx ... 1

In this embodiment, the front-back and left-right velocities are detected by the optical sensor, and the sideslip angle β is set as described above.
However, other methods may be used to determine the sideslip angle of the vehicle. For example, by providing front and rear and left and right acceleration sensors, front and rear / left and right acceleration and yaw rate,
The sideslip angle β may be calculated, or the signal of the steering angle sensor may be used to have a linear two-degree-of-freedom vehicle model in the controller, and the β value may be estimated therefrom.

Next, in step S103, the reference hydraulic pressure of the target wheel cylinder pressure Pi (i = 1 to 4) for each wheel is calculated. That is, the reference wheel cylinder pressure Po is calculated from the brake pedal force Fp. In the present embodiment, the reference wheel cylinder pressure Po is calculated according to the following equation using the brake pedal force Fp which is the sensor signal.

[Equation 2] Po = Kt × Fp ... 2 Here, Kt is a proportional constant, and therefore the reference wheel cylinder pressure Po as the reference hydraulic pressure is the brake pedal force Fp.
Shall be proportional to.

Next, in step S104, it is determined whether the direction of the lateral force generated by the front wheels is the stable direction or the unstable direction of the vehicle depending on the direction of the lateral acceleration Ygf on the front wheel shaft.

That is, in the present embodiment, as described above, the lateral acceleration Ygf value is read from the signal of the sensor 16 in step S101 and the vehicle side slip angle β value is calculated in step S102. When the direction (sign) of the lateral acceleration Ygf on the wheel axle is opposite, the driver is steering to stabilize the vehicle, and it is determined that the lateral force of the front wheels is also generated in the direction to stabilize the vehicle. In this case, the process proceeds to step S105, and control for reducing the lateral force of the front wheels is not performed. On the other hand, when the side slip angle β of the vehicle and the direction (sign) of the lateral acceleration Ygf on the front wheel shaft are the same, the driver does not steer to stabilize the vehicle, and the lateral force of the front wheel also stabilizes the vehicle. In this case, the control proceeds to step S106, and control is performed to reduce the lateral force of the front wheels, as will be described later.

Specifically, in step S105, the target wheel cylinder hydraulic pressure Pi (i = 1 to 4) of each wheel is set to be the same as the reference wheel cylinder pressure Po determined by the brake pedal force Fp. Therefore, at this time, the steps after step S106 described below are skipped, and the front, rear, left, and right 4
The process of step S110 described below is executed with Pi = Po for each wheel, and as a result, no differential pressure is generated in the braking force between the front and rear wheels.

On the other hand, steps S104 to S1
When proceeding to 06, in step S106, the target differential pressure ΔPx generated between the front and rear wheels is calculated.

In the present embodiment, the ΔPx value is obtained from the characteristic diagram shown in FIG. In the figure, a predetermined reference value (allowable value) βo (positive / negative) is set for the sideslip angle β of the vehicle. When the sideslip angle β value is within the range of −βo to βo, the ΔPx value is set to 0. When ΔPx is set to a value of 0 and applied to the processing described below, no differential pressure is generated in the braking force of the front and rear wheels. On the other hand, when the sideslip angle β takes a larger value, it is considered that the vehicle is unstable, and in such a region, according to the characteristic tendency as shown in the figure, according to the calculated sideslip angle β value at that time, for example, the β1 value Then, the illustrated value ΔPx1 corresponding thereto is determined as the target differential pressure.

Here, the characteristic curve is changed according to the vehicle speed, and the lateral force of the front wheels is reduced by the distribution of the braking force of the front and rear wheels to control the target differential pressure for controlling the yawing moment of the vehicle. ΔPx may be a function of the vehicle speed and the sideslip angle β. Further, the ΔPx value may be calculated in consideration of not only the magnitude of the sideslip angle β but also the rate of change thereof.

Regarding the allowable value βo of the sideslip angle β, as shown in FIG. 5, the steering angle δ and the vehicle speed Vx (front-rear speed)
It can be determined more, and this is the case in this embodiment. By doing so, the above-described ΔPx value calculation process can be performed using βo calculated as the allowable value βo from the steering angle and the vehicle speed at that time according to the characteristics of FIG. Therefore, in this case, the stability of the vehicle is also determined by comparing the calculated side slip angle β with the allowable value βo calculated from the vehicle speed Vx and the steering angle δ, and the vehicle stability determination can be performed more finely. .

Next, in step S107, the wheel for each wheel is used to generate a differential pressure between the front and rear wheels necessary for performing control for reducing the lateral force of the front wheels, using the reference wheel cylinder pressure P _o value as a basic value. A target value Pi of cylinder hydraulic pressure is set. That is, the target wheel cylinder differential pressure ΔP
Using x and the reference wheel cylinder pressure Po, the target wheel cylinder pressure Pi (i = 1 to 4) of each wheel is calculated from these.

Here, for the sake of simplicity, if the differential pressure is generated by increasing the pressure on the front wheel side, the target values Pi
Can be:

Equation 3] _{P1 = P o + ΔPx ··· 3a} P2 = P o + ΔPx in _{··· 3b P3 = P o ··· 3c} P4 = P o ··· 3d herein, normal front-rear braking force distribution (so-called Proportional I omitted it about the front and rear distribution by the
Of course, it may be taken into consideration. Further, the target differential pressure may be generated by increasing the pressure of the front wheels and decreasing the pressure of the rear wheels.

Steps S108 and S109 are processes for preventing the target wheel cylinder hydraulic pressure Pi from becoming 0 or less. If applicable, this process is incorporated and executed, and in the next step S110, each time this step is executed, The brake fluid pressure control process is executed, and this program ends.

The processing contents here are the control signal (Pi) corresponding to the hydraulic pressure command value Pi for each wheel obtained as described above.
(S)) is individually determined and output to the pressure servo unit 7.
To the wheel cylinders 5L, 5R, 6L, 6R for each wheel by adjusting the actual wheel cylinder hydraulic pressures P1 to P4 according to the above Pi.

Thus, according to the above control, when it is determined that the vehicle is unstable and the yawing moment of the vehicle is controlled by reducing the lateral force of the front wheels 1L and 1R, the front wheel axle is used. The lateral acceleration Ygf of
The braking force distribution for the front and rear wheels is distributed only when it is detected that the yawing moment in the direction in which the lateral movement of the vehicle is stable is not generated due to the direction of the actual lateral acceleration generated by the actual front wheel lateral force. It is possible to realize control that stabilizes the vehicle by controlling the lateral slip angle β of the vehicle so as to increase the 1L and 1R sides and reducing the lateral force of the front wheels.
Therefore, it is possible to deal with the situation where the driver erroneously steers in the direction of vehicle instability in view of the result in a panic condition and the vehicle becomes unstable at that time and the sideslip angle β becomes large. Controls the reduction of the lateral force on the front wheels by distributing the braking force to the front and rear wheels, and thus stabilizes the posture of the vehicle without the driver's erroneous operation in such a situation. In addition to being controllable, when the driver performs a correct operation and operates the vehicle in the stable direction by using the steered front wheels, the operation can be used to constantly stabilize the vehicle.

A further supplementary description of this will be given below with reference to FIGS. 6 and 7. Figure 6
The upper part is a two-wheel model, and the lower parts (a) to (e) are simplified representations of the modes of the forces acting on the front and rear wheels. Considering the balance of wheel forces, even if the yawing moment acting on the vehicle is the same (Figs. (A) to (e))
The lateral force acting on the front wheels is different in each case. Focusing on Figures (a) to (c) and (e), and assuming that the counterclockwise direction is the spin direction in the figures, in the case of Figure (e), unlike the other cases, the front wheel lateral force is directed in the direction that prevents the spin. You can see that is working.

The present control utilizes this effectively based on the above consideration. FIG. 7 and FIG. 8 are specific control scenes according to the present control, taking FIG. 7 as an example of turning inward when the vehicle is turning and FIG. 8 as an example of turning outward in turning. The former corresponds to a situation in which the vehicle stability control is executed by the above-mentioned distribution of the braking force before and after, and the latter corresponds to a situation in which the vehicle is stabilized by using the correct operation of the driver.

Referring to FIG. 7, this means that the vehicle is now making a left turn aiming at the turning trajectory shown, and the driver's operation is turning inward. Lateral acceleration (lateral G) that occurs on the front wheel axle of the vehicle in this vehicle traveling and maneuvering scene
Ygf acts in the direction of increasing the sideslip angle β of the vehicle. Therefore, in this case, according to the control of this embodiment,
In the region where the side slip angle β exceeds the set allowable value (region where it is determined that the vehicle is unstable), the braking force of the front wheels is corrected by increasing ΔPx (Figs. 4, 5, formulas 3a and 3b) to reduce the lateral force of the front wheels. (Steps S104 → S106 → S107 → S108 →
S109 → S110). As a result, the vehicle side slip angle β decreases. In this way, the vehicle can be stabilized.

In FIG. 8, the same left turn is being made, but the driver's operation is turning outward in the turn. At this time, the lateral acceleration (lateral G) Ygf generated on the front wheel shaft acts in the direction of decreasing the side slip angle β of the vehicle (FIG. 6).
(See (e)). Therefore, in this case, the braking force of the front wheels is maintained at Po in accordance with the control of this embodiment (steps S104 → S).
105 → S110). That is, this is a case where the driver steers accurately and the lateral force of the front wheels is also generated in a direction in which the vehicle stabilizes. I don't. As a result, the lateral acceleration Ygf that acts in the direction of decreasing the vehicle side slip angle β is secured.

In addition to the stability judgment of the vehicle based on the side slip angle β of the vehicle, the lateral acceleration Ygf on the front wheel axis is also taken into consideration in the direction of the actual lateral acceleration generated by the actual front wheel lateral force. With this control, which can be used properly and properly, even if the driver steers accurately in an attempt to stabilize the vehicle and the lateral force of the front wheels is also generated in the direction in which the vehicle stabilizes, the vehicle will only be able to uniformly slip. It controls according to the angle β and does not reduce the lateral force of the front wheels. Therefore, in such a case, it takes time for the vehicle to stabilize instead of the driver trying to stabilize the vehicle, or the steering feeling of the driver at that time may worsen. Since it can be prevented from occurring, it can effectively function as a vehicle stabilizer. In this way, the vehicle is stabilized regardless of uncertain driver's operation, and if the driver is operating the vehicle in a stable direction with the front steering wheel, it is possible to use that operation to ensure proper operation. The control that stabilizes the vehicle becomes possible, and the conventional problems can be solved.

Further, only when the steering state is detected and it is estimated that the yaw moment in the direction in which the lateral movement of the vehicle is stabilized by the front wheel lateral force is not generated, the control according to the side slip angle is performed. In this case, it is difficult to estimate that the front wheel lateral force is acting in a stable direction when the vehicle is actually in a state close to a spin. Even in a situation, it is possible to easily realize proper control and increase controllability.

According to the above embodiment, the control can be performed even when the driver is not braking, but the control may be performed only when braking in consideration of the discomfort caused by braking.

Although the anti-skid control is not described in the embodiment, there is no problem if the wheel speed of each wheel is detected and the anti-skid control is performed at the same time. In that case, the braking force control may be performed by controlling the slip ratio of each wheel instead of by controlling the yawing control by the differential pressure between the front and rear.

An example in which yawing control is performed by controlling the slip ratio during braking will be described. In this embodiment, each wheel braking force control means controls the wheel speed to a predetermined slip relative to the vehicle speed. The braking force is controlled so that the vehicle stability is determined by the vehicle stability determination means, and the lateral lateral motion of the vehicle is stabilized by the front wheel lateral force due to the lateral acceleration detected on the front wheel axis. If it is determined that the yawing moment in the direction of the front wheel is not generated, the braking force is controlled by correcting the wheel speed so that the front and rear wheels have a large slip ratio and the rear wheels have a small slip ratio. be able to.

For example, the wheel speed correction amount ΔVw is used according to a characteristic diagram as shown in FIG. the system,
In this case, for example, in the four-channel four-sensor type anti-skid control, a wheel speed sensor (not shown) is provided for each of the front, rear, left, and right wheels, so that the wheel speed V of the left front wheel is
w1, wheel speed Vw2 of the right front wheel, wheel speed Vw3 of the left rear wheel,
By detecting the wheel speed Vw4 of the right rear wheel and correcting the actual wheel speed using the wheel speed correction amount ΔVw, the apparent slip ratio is the same as that of the front wheel,
Assuming that the slip ratio of each wheel is controlled individually, the correction amount Δ according to the lateral slip angle β and the lateral acceleration Ygf on the front wheel shaft
From Vw, for example,

(4) Vw1 ^* = Vw1 + ΔVw ・ ・ ・ 4a Vw2 ^* = Vw2 + ΔVw ・ ・ ・ 4b Vw3 ^* = Vw3 ・ ・ ・ 4c Vw4 ^* = Vw4 ・ ・ ・ 4d (however, ^* indicates the corrected value) Anti-skid control is performed using the corrected wheel speed. As a result, the braking force of the front wheels is controlled to be more locked than the rear wheels, so the cornering force of the front wheels is reduced and the vehicle is understeered. The present invention can be carried out in this way, and the present embodiment has the same operational effect. When using a method that uses such a wheel speed correction amount, the wheel speed correction may be performed by positive correction of the front wheels and negative correction of the rear wheels.

Further, in each of the above-mentioned embodiments, only the front / rear braking force distribution according to the side slip angle β is touched, but normally, the front / rear / left / right braking force distribution is performed by the yaw rate feedback control, so that the vehicle is not operated. When the control becomes stable and the sideslip angle β becomes large, this control is activated so that there is no problem in using both controls together.

Further, according to the characteristic diagram as shown in FIG. 10, not only the front / rear braking force distribution by ΔPx but also the left / right distribution control may be simultaneously performed. For example, β1 shown in the figure
The ΔPy amount corresponding to the value represents the target differential pressure generated between the left and right wheels, which is set based on the characteristic indicated by the broken line for the left and right braking force distribution control. In this case, in order to reduce the sideslip angle, a differential pressure is generated on the left and right sides,
For example, since there is a direction in which the pressure is increased (in the case of one-side pressure increase control) or the pressure is decreased (in the case of one-side pressure decrease control), the characteristic diagram also has a symbol. The present invention can also be implemented in this manner.

Although the lateral acceleration on the front wheel shaft of the vehicle is obtained by the lateral acceleration sensor 16, the present control may be performed by estimating the lateral acceleration on the front wheel shaft.

Further, the lateral motion is not limited to the lateral slip of the vehicle,
Yaw rate is also acceptable. That is, if the detected yaw rate exceeds the predetermined reference value, the vehicle is determined to be unstable. Specifically, the system has a yaw rate sensor that detects the yaw rate generated in the vehicle, detects the lateral motion state of the vehicle by detecting the yaw rate of the vehicle, and detects the actual yaw rate and the vehicle speed and steering angle. By comparing with the calculated target yaw rate, it can be determined that the vehicle is unstable when the actual value of the yaw rate is larger than the target value by a predetermined value or more.
The vehicle stability determination means may perform this control in this way.

[0052]

According to the invention described in claim 1, the attitude control of the vehicle can be performed by the braking force control of the front and rear wheels, and
When it is judged that the vehicle is unstable and the yaw moment of the vehicle is controlled by reducing the lateral force of the front wheels, it is appropriate to use the actual lateral acceleration generated by the actual lateral force of the front wheels. It is possible to control and detect lateral acceleration on the front wheel axis, and the yawing moment in the direction in which the lateral motion of the vehicle is stabilized is generated by the direction of the actual lateral acceleration generated by the actual front wheel lateral force. If it is detected, the braking force distribution of the front and rear wheels is controlled so that it becomes larger on the front wheel side, and the lateral force of the front wheels can be reduced to stabilize the vehicle, regardless of uncertain driver operations. When the vehicle is stable and the driver is operating correctly and the vehicle is being steered in the stable direction by the steered front wheels, the operation can be utilized appropriately and control for stabilizing the vehicle is possible. To become. In the case of the conventional one, it takes time to stabilize the vehicle, and even in a situation where the steering feeling is deteriorated, it is possible to avoid it and realize the above,
It is possible to deal with a wide range of vehicle traveling and maneuvering situations, and effectively improve vehicle stability.

In the second aspect, the vehicle attitude control similar to the above can be performed by using the lateral motion state detecting means as the vehicle side slip angle detecting means, and the vehicle stability determining means according to the third aspect is used. The vehicle attitude control similar to that described above can be performed by determining the stability of the vehicle by comparing the lateral motion state of the vehicle with the target lateral motion state calculated from the vehicle speed and the steering angle.

Further, in the present invention, the wheel braking force control means controls the braking force so that the wheel speed has a predetermined slip ratio with respect to the vehicle body speed, and the vehicle stability judging means. When it is determined that the vehicle is unstable, and it is determined by the signal from the front axle lateral acceleration detecting means that the yaw moment in the direction in which the lateral motion state of the vehicle is stabilized by the front wheel lateral force is not generated. In order to control the braking force by correcting the wheel speed so that the front wheel side has a large slip ratio of the front and rear wheels and the rear wheel side has a small slip ratio,
Even in this case, the same vehicle attitude control as described above can be realized.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a vehicle attitude control device of the present invention.

FIG. 2 is a system diagram showing an embodiment of a vehicle attitude control device of the present invention.

FIG. 3 is a flowchart showing an example of a control program of a controller.

FIG. 4 is a diagram showing an example of characteristics for calculating a target differential pressure between front and rear wheels.

FIG. 5 is a diagram showing an example of setting characteristics of an allowable value of a sideslip angle.

FIG. 6 is a diagram for explaining the principle of the vehicle attitude control in consideration of the lateral acceleration generated on the front wheel shaft.

FIG. 7 is a diagram provided for explaining a control mode of vehicle attitude control, which is illustrated by way of an example of turning inward during turning of a vehicle.

FIG. 8 is a diagram for explaining a control mode in the case of steering in the outward turning direction.

FIG. 9 is a diagram showing an example of a characteristic of a wheel speed correction amount applicable in another embodiment of the present invention.

FIG. 10 is a diagram showing still another embodiment of the present invention and is a diagram showing an example of characteristics for calculating a target differential pressure that can be applied when the left and right braking force distributions are used together.

[Explanation of symbols]

 1L, 1R Left and right front wheels 2L, 2R Left and right rear wheels 3L, 3R, 4L, 4R Brake discs 5L, 5R, 6L, 6R Wheel cylinder 7 Pressure servo unit 8 Hydraulic pressure source 9 Controller 10 Brake petal 11 Pedal force sensor 13 Front / rear / Left / right vehicle speed Sensor 14 Steering wheel (Steering wheel) 15 Steering angle sensor 16 Lateral acceleration sensor on front axle

Claims (4)

[Claims] 1. A wheel braking force control means capable of independently controlling a braking force of a wheel, a lateral motion state detecting means for detecting a lateral motion state of a vehicle, and a lateral acceleration on a front wheel shaft of the vehicle, or Front-axis lateral acceleration detecting means for estimating, vehicle stability determining means for determining vehicle stability according to the lateral motion state, and vehicle stability determining means for determining that the vehicle is unstable, and By the signal from the front-axis lateral acceleration detection means,
When it is determined that the yawing moment in the direction in which the lateral motion state of the vehicle is stabilized by the front wheel lateral force is not generated, the braking force control means controls the braking force distribution of the front and rear wheels to be increased on the front wheel side. And a yaw / moment control means for controlling the vehicle attitude. 2. The vehicle attitude control device according to claim 1, wherein the lateral motion state detection means is a vehicle side slip angle detection means. 3. The vehicle stability determining means determines the vehicle stability by comparing a lateral motion state of the vehicle with a target lateral motion state calculated from a vehicle speed and a steering angle. 1. The vehicle attitude control device according to 1. 4. The wheel braking force control means controls the braking force so that the wheel speed has a predetermined slip ratio with respect to the vehicle body speed, and the vehicle stability determination means determines that the vehicle is unstable. If it is determined that the yaw moment in the direction in which the lateral motion state of the vehicle is stabilized by the front wheel lateral force is not generated by the signal from the front axle lateral acceleration detection means, the front and rear wheels slip. 2. The vehicle attitude control device according to claim 1, wherein the braking force is controlled by correcting the wheel speed so that the ratio is larger on the front wheel side and smaller on the rear wheel side.