JPH0687420A - Vehicle behavior control device - Google Patents

Abstract

PURPOSE:To prevent the change for a vehicle behavior condition due to the degree of a steered angle, by reducing effect on steered angle change to a vehicle yaw rate caused by the difference of braking force and driving force between right and left steering wheels. CONSTITUTION:The signals concerning the steered angle delta of a steering wheel 10, the footing force FP of a brake pedal 12, the actual yaw rate (d/dt) phi of a vehicle and wheel speeds VW1, VW2, VW3, and VW4 are inputted to a controller 9 from each sensor in order to control the braking force difference between right and left steering wheels (front wheels) 1L and 1R. In the controller 9, feed-back gain, for deciding the target wheel cylinder hydraulic pressure of each wheel, is decided according to a steered angle, so as to obtain a desired moment at both the time of straight-going (in a small steered angle) and turning (in a large steered angle) by performing a given control program.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle behavior control device capable of obtaining a yaw moment of a vehicle as intended by a driver regardless of the steering angle.

[0002]

2. Description of the Related Art Generally, it is known that the behavior of a vehicle changes according to a left-right braking force difference or a left-right driving force difference generated between left and right wheels on a front wheel side or a rear wheel side. Various techniques have been proposed for achieving the vehicle behavior intended by the driver by controlling the driving force difference. As a conventional example of such a vehicle behavior control device, for example,
There is one disclosed in JP-A-4-66357. In this conventional example, a target yaw rate, which is a target behavior state of the vehicle, is set based on the vehicle speed and the steering angle as parameters representing the running state of the vehicle, and the target yaw rate is made to match the yaw rate actually generated in the vehicle. The required target left / right braking force difference is calculated by calculation based on the vehicle model set in advance by the vehicle specifications and the equation of motion (for example, the deviation between the yaw rates is multiplied by a predetermined gain). Make sure that the left / right braking force calculated from the difference matches the actual left / right braking force.
Yaw rate feedback control is performed.

[0003]

In the above-mentioned conventional example, the yaw moment actually generated based on the predetermined braking fluid pressure control depends on the steering angle of the steered wheels, as will be described in detail below. Since the change is so large, even if the intended yaw moment is generated when the steering angle is small, the driver really wants to generate the yaw moment, and the steering angle is large. Therefore, the actually generated yaw moment is reduced, and the intended vehicle behavior control cannot be achieved.

For example, when the vehicle is in a straight traveling state (small steering angle)
The yaw acceleration β generated by the differential pressure,
As shown in Fig. 5 (a), the braking force of the left and right front wheels is set to B
_FL, B _FR, Their deviation is ΔB, and yaw inertia moment
Let T be T and tread be Tf.
The equation of motion is as follows.

[Equation 1] On the other hand, when the vehicle is in a turning state (large steering angle), if the front wheel steering angle is θ and the distance from the vehicle center of gravity to the front wheel axis is Lf, the equation of motion regarding the yaw moment is expressed by the following equation.

[Equation 2]

In the case of a normal brake, this equation (2) is I
・ Β = −Lf (B _FL + B _FR ) SIN θ, so the yaw acceleration β due to the differential pressure is

[Equation 3] Will be represented by. Therefore, the yaw acceleration β decreases in the COS waveform as the front wheel steering angle θ increases.

An object of the present invention is to solve the above-mentioned problems by reducing the influence of the steering angle change on the yaw rate of the vehicle caused by the difference in braking force or the difference in driving force between the left and right steered wheels.

[0007]

To this end, the configuration of claim 1 of the vehicle behavior control device of the present invention is, as shown in the concept of FIG. 1 (a), a vehicle target for calculating a target behavior state of the vehicle. A behavior state calculating means, and a braking / driving force difference setting means for setting a braking force difference of the braking force applied to the left and right steered wheels or a driving force difference of the driving force applied to the left and right steered wheels according to the calculated target behavior state, In the vehicle behavior control device, the left and right steered wheels include a left and right braking / driving force difference control means for controlling a braking force difference or a driving force difference between the left and right driving wheels based on a set value by the braking / driving force difference setting means. Steering angle detecting means for detecting the steering angle of the vehicle is provided, and when the vehicle target behavior state calculating means calculates the target behavior state of the vehicle, or the braking / driving force difference setting means sets the braking force difference or the driving force difference. When the steering angle detection means Based on the detected steering angle, the amount of change caused by the steering angle change amount in the yaw rate of the vehicle caused by the difference in braking force or the difference in driving force between the left and right steered wheels is reduced.

Further, according to the second aspect of the present invention, as shown in the concept of FIG. 1 (b), the vehicle target behavior state calculating means for calculating the target behavior state of the vehicle and the left and right steered wheels according to the calculated target behavior state. A braking / driving force difference setting unit that sets a braking force difference of the braking force to be applied or a driving force difference of the driving force to be applied to the left and right steered wheels, and the left and right driving wheels based on the set value by the braking / driving force difference setting unit. In a vehicle behavior control device comprising left and right braking / driving force difference control means for controlling a braking force difference or a driving force difference, a steering angle detecting means for detecting a steering angle of the left and right steered wheels is provided, The braking / driving force difference is corrected on the basis of the steering angle detected by the steering angle detecting means so as to reduce the change amount caused by the steering angle change amount in the yaw rate of the vehicle caused by the braking force difference or the driving force difference. Braking / driving force difference The correction means is provided in the braking / driving force difference setting means.

[0009]

In the structure of claim 1 of the present invention, the braking force difference between the braking force applied to the left and right steered wheels by the braking / driving force difference setting means or the left or right side in accordance with the target behavioral state calculated by the vehicle target behavioral state calculating means. A steering angle detection is performed when the driving force difference of the driving force applied to the steered wheels is set, and the left / right braking / driving force difference control means controls the braking force difference or the driving force difference of the left / right driving wheels based on the set value. Based on the steering angle detected by the means, the amount of change caused by the steering angle change amount in the yaw rate of the vehicle caused by the braking force difference or the driving force difference between the left and right steered wheels is reduced. A desired vehicle behavior control can be performed by preventing the vehicle behavior state from changing.

According to the second aspect of the present invention, the braking force difference of the braking force applied to the left and right steered wheels by the braking / driving force difference setting means in accordance with the target behavior state calculated by the vehicle target behavior state calculation means. Alternatively, when the driving force difference of the driving force applied to the left and right steered wheels is set, and the left and right braking / driving force difference control means controls the braking force difference or the driving force difference of the left and right driving wheels based on the set value, The braking / driving force difference is corrected on the basis of the steering angle detected by the steering angle detecting means so as to reduce the amount of change caused by the steering angle change amount in the yaw rate of the vehicle caused by the difference in braking force or the difference in driving force between the left and right steered wheels. Since the left and right braking / driving force difference correction means is provided in the braking / driving force difference setting means, the same operational effect as that of the first aspect can be obtained.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 2 is a diagram showing the configuration of an embodiment of the vehicle behavior control device of the present invention. The vehicle to be applied is capable of independently controlling the braking force of each wheel, and in the present embodiment, the left and right braking force differences (braking hydraulic pressure differences) of the front wheels are individually controlled. In the figure, 1L and 1R indicate left and right front wheels, and 2L and 2R indicate left and right rear wheels, respectively. Each wheel has a brake disc 3L,
Wheel cylinders 5L, 5R, 6L, 6R that apply a braking force (braking force) to each wheel by frictionally sandwiching a brake disc by supplying hydraulic pressure (hydraulic pressure) with 3R, 4L, 4R
By supplying hydraulic pressure from the pressure servo unit (pressure control unit) 7 to each wheel cylinder of these brake units, each wheel is individually braked to control the behavior of the vehicle.

The pressure servo unit 7 constitutes a braking force control unit together with a controller which will be described later. The pressure servo unit 7 adjusts the hydraulic pressure from the hydraulic pressure generation source 8 in response to an input control signal to control the wheel cylinders 5L, 5R, 6L of the respective wheels. The braking hydraulic pressure (brake hydraulic pressure) supplied to 6R is controlled. The pressure servo unit 7 is configured to include an actuator for each hydraulic pressure supply system (each channel) of the left and right front wheels. As the actuator, for example, an actuator that can be used in combination with anti-skid control (ABS control) and that can perform pressure reduction, pressure holding, and pressure increase control is used. In the pressure servo unit 7, the input hydraulic pressure command signal, specifically, the left front wheel hydraulic pressure command value P1 is provided by the actuator for controlling the hydraulic pressure of each supply system.
*, Right front wheel hydraulic pressure command value P2 *, left rear wheel hydraulic pressure command value P3 *, individually brake fluid corresponding to the right rear wheel hydraulic pressure command value P4 * each signal pressure P ₁
~ P ₄ shall be regulated.

The above signals are supplied from the controller (control unit) 9 to the pressure servo unit 7.
The controller 9 includes a signal from the steering angle sensor 11 that detects the steering angle δ (steering wheel angle) of the steering wheel (steering wheel) 10, a signal from the pedaling force sensor 13 that detects the pedaling force F _P of the brake pedal 12, and A signal from the yaw rate sensor 14 that detects the actual yaw rate (d / dt) that acts, the wheel speed (rotational speed) Vw ₁ , Vw ₂ , V for each wheel.
The signals from the wheel speed sensors 15, 16, 17, 18 for detecting w ₃ and Vw ₄ are input respectively. Here, the signal from the yaw rate sensor is used as a control parameter in the braking fluid pressure difference control by the yaw rate feedback method.

The controller 9 includes a microcomputer and the like, and basically controls the vehicle behavior by the yaw moment during braking, that is, controls the braking force by the yaw rate feedback method so that the vehicle behavior becomes a target characteristic. Specifically, in the arithmetic processing circuit, a target yaw rate, a yaw rate difference value, etc. are calculated according to a control program described later, and the target wheel cylinder fluid used for the braking force (brake force) control for each wheel is calculated using these calculated values. The pressure value (command value) is calculated and a signal corresponding to it is output to the pressure servo unit 7. This allows
The pressure servo unit 7 is used to adjust the hydraulic pressure from the hydraulic pressure generation source 8 so that the actual wheel cylinder hydraulic pressure for each wheel matches the above target hydraulic pressure, and the wheel cylinders 5L, 5R are used as braking hydraulic pressures. , 5L, 6R.

FIG. 3 is executed by the controller 9,
It is an example of a control program for vehicle behavior control by the brake fluid pressure difference control of the left and right front wheels. This processing is executed by a regular interrupt at regular time intervals by an operating system (not shown). First, in step S110 of FIG. 3, based on the output signals of the steering angle sensor, the pedal effort sensor, the wheel speed sensor, and the yaw rate sensor, the steering angle δ, each wheel 1L, 1R, 2
L, the wheel speed Vw ₁ ~ Vw ₄ of 2R, reads each brake pressing force F _P and the yaw rate (d / dt) φ. In the following step S111, the vehicle speed (vehicle body speed) is estimated based on the wheel speed Vw _j (j = 1 to 4). In this embodiment, (for example FR vehicle, the left and right front wheels) driven wheels with the wheel speed Vw _1, Vw ₂ of, determined by calculating the vehicle speed from _{V = (Vw 1 + Vw 2} ) / 2.

In the next step S112, the brake pedal force F
_The brake pressure reference value P ₀ is calculated from P. In this embodiment, the reference value P ₀ is calculated by P ₀ = k · F _P. Here, k is a proportional constant determined by vehicle specifications. In addition,
The reference value P ₀ is not simply proportional to the brake pedal force F _P , but is determined by a function of the brake pedal force; P ₀ = f (F _P ), so as to match the driver's feeling. Good.

Next, in order to control the braking force by the yaw rate feedback system during braking, the vehicle speed V is determined in step S113.
The target yaw rate (d / dt) φ _ref is calculated from the steering angle δ and the steering angle δ. In the present embodiment, the target yaw rate is calculated according to the following equation (the vehicle speed V
And a steering angle δ may be used to obtain a certain characteristic map).

[Equation 4] Here, A is a constant determined by the vehicle wheel base and the steering gear ratio, and K is a constant representing the steer characteristic of the vehicle. In this step S113,
The controller 9 functions as a vehicle target behavior state calculation means.

In the next step S114, the above step S114 is performed.
The yaw rate difference value Δ (d / dt) φ, which is the deviation between the target yaw rate (d / dt) φ _ref obtained in 113 and the actual yaw rate (d / dt) φ (actual yaw rate),

[Equation 5] Calculate by

In the next step S115, the actual steering angle δf is calculated from N and the steering angle δ described later. This operation is
In the present embodiment, since it is premised that only the front wheels are steered, it is determined according to the following equation.

[Equation 6] Here, N is a proportional constant obtained by vehicle specifications such as steering gear ratio and steering rigidity. When applied to a vehicle provided with a rear wheel auxiliary steering device, the actual steering angle δr of the rear wheels is obtained by the same calculation in order to generate a differential pressure at the rear wheels. In this step S115,
The controller 9 functions as steering angle detection means.

In the next step S116, the target differential pressure generated on the left and right wheels is calculated. In this embodiment, step S11
The yaw rate difference value Δ (d / dt) φ obtained in step 4 and step S
The target left-right differential pressure ΔP to be generated in the wheel cylinders of the left and right front wheels to be controlled is calculated by the following equation based on the product of the actual steering angle δf and the feedback gain Ks determined by the characteristic diagram of FIG. Calculate according to.

[Equation 7] In step S116, the controller 9 functions as braking / driving force difference setting means and left / right braking / driving force difference correction means.

In the next step S117, the target left / right differential pressure Δ
Using P, the target wheel cylinder hydraulic pressure Pj * of each wheel is calculated. In the present embodiment, the calculation of the wheel cylinder hydraulic pressure target value Pj * is performed according to the following equation based on the brake pressure reference value P ₀ and the target left-right differential pressure ΔP.

[Equation 8]

[Equation 9]

[Equation 10]

[Equation 11] In step S117, the controller 9 functions as a left / right braking / driving force difference control means.

Here, for the sake of simplicity, the left-right difference is generated only on the front wheel side, but the left-right difference may be generated only on the rear wheel or both the front and rear wheels, and in that case as well. Including, the left-right distribution control may be performed by the one-side pressure reduction control. Further, the rear wheel side hydraulic pressure may be reduced with respect to the reference wheel cylinder hydraulic pressure P _{0 by a} usual method.

After the target wheel cylinder hydraulic pressure for each wheel is determined in step S117, in step S118
The brake hydraulic pressure control is executed so that the actual wheel cylinder hydraulic pressure (brake hydraulic pressure) of each wheel becomes the target hydraulic pressure. The processing content consists of individually determining a control signal (PjA *) corresponding to the target wheel cylinder hydraulic pressure Pj * and outputting it to the pressure servo unit 7. By supplying these signals to this unit, each wheel is supplied. It is assumed that the actual wheel cylinder hydraulic pressure Pj is adjusted so as to control the wheel cylinder hydraulic pressures P _{1 to} P ₄ to the target hydraulic pressure Pj * and is applied to the wheel cylinders 5L, 6L, 6R for each wheel.

In the present embodiment, by executing the above-described control, as shown in FIG. 4, a desired yaw moment is obtained by the feedback gain (proportional constant) Ks ₀ determined by the vehicle specifications when the vehicle is straight ahead (small steering angle). When the vehicle is turning (when the steering angle is large) and the driver really wants to generate a yaw moment, the feedback is much larger than Ks ₀ , which is determined according to the steering angle δr. Gain K
By reducing the amount of change caused by the steering angle change amount in the yaw rate of the vehicle, s prevents the actually generated yaw moment from decreasing and realizes the intended vehicle behavior control.

In the above-described embodiment, the yaw rate feedback control of the braking force of the left and right steered wheels has been described. Instead, the vehicle in which the steered wheels and the driving wheels are common and the driving force distribution control can be performed by the left and right wheels Applying the present invention to
The driving force of the left and right steered wheels may be yawed rate feedback controlled, and in that case, the same effect can be obtained. Further, in the above embodiment, the target wheel cylinder hydraulic pressure
Although the case where Pj * is corrected according to the steering angle δr is shown, instead, a parameter relating to the target behavior state or the braking / driving force difference may be calculated directly by looking up a map or the like with the steering angle δr. Good.

In the above embodiment, the yaw rate feedback type braking force control is used for the basic braking force control. Instead, however, the controller is provided with a vehicle model (vehicle characteristics) and the braking force is fed forward. Even when controlling, the present invention can be applied by correcting the generated differential pressure so as to suppress the fluctuation of the control effect based on the steering angle. Further, in the above embodiment, the feedback control is performed by so-called proportional control, but instead, a control method in which one or both of a differential operation and an integral operation are added may be adopted. Further, in the above-described embodiment, the feedback gain Ks is changed in order to prevent the problem that the control effect fluctuates more at the large steering angle than at the small steering angle, but instead, a predetermined correction amount is added or the target gain is changed. It may be corrected in advance when the yaw rate is calculated.

Further, in the above embodiment, the absolute differential pressure is changed, but instead, by detecting the lateral motion state of the vehicle and changing the left and right target slip ratios according to the left and right deviations of the vehicle, the result is changed. In addition, the present invention can be applied by correcting the target slip ratio so as to suppress the fluctuation of the control effect due to the steering in the control for generating the differential pressure between the left and right wheels.

[0028]

As described above, the vehicle behavior control system according to the present invention reduces the influence of the steering angle change on the yaw rate of the vehicle caused by the difference in the braking force or the difference in the driving force between the left and right steered wheels. The desired vehicle behavior control can be performed by preventing the vehicle behavior state from changing depending on the magnitude of the.

[Brief description of drawings]

1A and 1B are conceptual diagrams of the present invention.

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

FIG. 3 is a flow chart showing a control program for vehicle behavior control by a brake fluid pressure difference control for the left and right front wheels, which is executed by the controller in the same example.

FIG. 4 is a characteristic diagram illustrating a feedback gain used for the brake fluid pressure difference control in association with an actual steering angle.

5 (a) and 5 (b) are diagrams for explaining a relationship between a steering angle and vehicle behavior.

[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 Steering wheel 11 Steering angle sensor 12 Brake pedal 13 Tread force sensor 14 Yaw rate sensor 15 to 18 Wheel speed sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location B62D 137: 00 (72) Inventor Naoki Maruko 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd. Within

Claims (2)

[Claims] 1. A vehicle target behavior state calculating means for calculating a target behavior state of a vehicle, and a braking force difference of a braking force applied to the left and right steered wheels or a driving force applied to the left and right steered wheels according to the calculated target behavior state. Braking / driving force difference setting means for setting the driving force difference, and left / right braking / driving force difference control means for controlling the braking force difference or the driving force difference of the left / right driving wheels based on the set value by the braking / driving force difference setting means. In a vehicle behavior control device comprising: a steering angle detection means for detecting a steering angle of the left and right steered wheels, wherein the vehicle target behavior state calculation means calculates a target behavior state of the vehicle, or the braking / driving When the force difference setting means sets the braking force difference or the driving force difference, based on the steering angle detected by the steering angle detecting means, the vehicle is generated by the braking force difference or the driving force difference between the left and right steered wheels. For yaw rate Characterized in that so as to reduce the variation caused by the steering angle change amount Te, the vehicle behavior control device. 2. A vehicle target behavior state calculating means for calculating a target behavior state of the vehicle, and a braking force difference of a braking force applied to the left and right steered wheels or a driving force applied to the left and right steered wheels according to the calculated target behavior state. Braking / driving force difference setting means for setting the driving force difference, and left / right braking / driving force difference control means for controlling the braking force difference or the driving force difference of the left / right driving wheels based on the set value by the braking / driving force difference setting means. And a steering angle detecting means for detecting a steering angle of the left and right steered wheels, wherein a steering angle change occurs in a yaw rate of the vehicle caused by a braking force difference or a driving force difference between the left and right steered wheels. The left / right braking / driving force difference correcting means for correcting the braking / driving force difference based on the steering angle detected by the steering angle detecting means is provided in the braking / driving force difference setting means so as to reduce the change caused by the amount. thing Wherein, the vehicle behavior control device.