JP2861670B2 - 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 magnitude of a steering angle.

[0002]

2. Description of the Related Art In general, it is known that the behavior of a vehicle changes in accordance with a difference in left and right braking forces or a difference in left and right driving forces generated between left and right wheels on a front wheel side or a rear wheel side. Various techniques have been proposed for realizing a vehicle behavior intended by a driver by controlling a 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. This conventional example sets a target yaw rate, which is a target behavior state of the vehicle, based on a vehicle speed and a steering angle as parameters representing a running state of the vehicle, and matches the target yaw rate with a yaw rate actually generated in the vehicle. The required target left and right braking force difference is calculated by an operation based on a vehicle model set in advance by vehicle specifications and equations of motion (for example, an operation of multiplying the deviation between the yaw rates by a predetermined gain). The left and right braking forces calculated from the difference are equal to the actual left and right braking forces,
Yaw rate feedback control is performed.

[0003]

In the above conventional example, the yaw moment actually generated based on the predetermined brake fluid pressure control varies according to the magnitude of the steering angle of the steered wheels as described in detail below. Even if the intended yaw moment is generated when the steering angle is small because of a large change, the steering angle is large when the driver truly wants to generate the yaw moment. In this case, the actually generated yaw moment decreases, and the intended vehicle behavior control cannot be achieved.

For example, when the vehicle is in a straight running state (small steering angle), the yaw acceleration β generated by the differential pressure is obtained, and as shown in FIG.
_Assuming that _FL and B _FR and their deviation are ΔB, the yaw moment of inertia is I, and the tread is Tf, the equation of motion related to the yaw moment is expressed by the following equation.

(Equation 1) On the other hand, when the vehicle is in a turning state (large steering angle), assuming that 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 relating to the yaw moment is expressed by the following equation.

(Equation 2)

This equation (2) indicates that for a normal brake, 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 Accordingly, as the front wheel steering angle θ increases, the yaw acceleration β decreases in a COS waveform.

The present invention addresses the inconvenience that occurs because the yaw moment of the vehicle caused by the braking force difference or the driving force difference between the left and right steered wheels becomes smaller than the driver's truly desired yaw moment as the steering angle increases. The purpose is to eliminate.

[0007]

For this purpose, a vehicle behavior control apparatus according to the present invention has a structure as shown in FIG. 1 (a), which calculates a target behavior state of a vehicle. Behavior state calculating means, braking / driving force difference setting means for setting a braking force difference of a braking force applied to the left and right steered wheels or a driving force difference of a driving force applied to the left and right steered wheels according to the calculated target behavior state, The vehicle behavior control device, further comprising: left / 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 value set by the braking / driving force difference setting means. The vehicle target behavior state calculation 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 detecting means is Based on the detected steering angle, the shortage of the yaw moment of the vehicle caused by the braking force difference or the driving force difference between the left and right steered wheels caused by the change in the steering angle is compensated. It is.

FIG. 1 (b) is a schematic diagram showing a concept of vehicle target behavior state calculation means for calculating a target behavior state of a vehicle; Braking / driving force difference setting means for setting the braking force difference of the braking force to be applied or the driving force difference of the driving force to be applied to the left and right steered wheels; and A vehicle behavior control device comprising: a left / right braking / driving force difference control means for controlling a braking force difference or a driving force difference, wherein the vehicle target behavior state calculation means calculates a target behavior state of the vehicle; When the force difference setting means sets the braking force difference or the driving force difference, the yaw moment of the vehicle generated by the braking force difference or the driving force difference between the left and right steered wheels based on the steering angle detected by the steering angle detection means. Of steering angle The right / left braking / driving force difference correcting means for correcting the braking / driving force difference so as to compensate for the shortage caused by the above is provided in the braking / driving force difference setting means.

According to a third aspect of the present invention, in any one of the first to third aspects, the right / left braking / driving force difference correcting means includes a feedback gain calculated based on the steering angle detected by the steering angle detecting means. It is characterized in that it is corrected.

[0010]

According to the first aspect of the present invention, the braking / driving force difference setting means applies the braking force difference or the left / right braking force applied to the left and right steering wheels in accordance with the target behavior state calculated by the vehicle target behavior state calculation means. 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 between the left and right driving wheels based on the set value, the steering angle is detected. Based on the steering angle detected by the means, the shortage of the yaw moment of the vehicle caused by the braking force difference or the driving force difference between the left and right steered wheels caused by the change in the steering angle is compensated. It is possible to perform desired vehicle behavior control by preventing the vehicle behavior state from being changed depending on the magnitude of.

According to the second aspect of the present invention, the braking / driving force difference setting means sets the braking force difference of the braking force applied to the left and right steered wheels in accordance with the target behavior state calculated by the vehicle target behavior state calculation means. Alternatively, a driving force difference between the driving forces applied to the left and right steered wheels is set, and when the left / right braking / driving force difference control means controls the braking force difference or the driving force difference between the left and right driving wheels based on the set value, the steering is performed. The braking / driving force is adjusted so as to compensate for a shortage of the yaw moment of the vehicle caused by the braking force difference or the driving force difference between the left and right steered wheels based on the steering angle detected by the angle detection means. Since the right / left braking / driving force difference correcting means for correcting the difference is provided in the braking / driving force difference setting means, the same operation and effect as in claim 1 can be obtained.

According to a third aspect of the present invention, in any one of the above-mentioned aspects, the steering angle is corrected by the feedback gain calculated based on the steering angle by the steering angle detecting means. Insufficient yaw moment of the vehicle caused by the braking force difference or the driving force difference can be easily compensated.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 2 is a diagram showing the configuration of one embodiment of the vehicle behavior control device of the present invention. The applied vehicle is capable of independently controlling the braking force of each wheel, and in this embodiment, it is assumed that the braking force difference (braking fluid pressure difference) between the left and right front wheels is controlled. In the figure, 1L and 1R denote left and right front wheels, and 2L and 2R denote left and right rear wheels, respectively. Each wheel has a brake disc 3L,
3R, 4L, 4R and wheel cylinders 5L, 5R, 6L, 6R for applying a brake force (braking force) to each wheel by frictionally holding a brake disc by supplying hydraulic pressure (oil pressure).
By supplying hydraulic pressure from a 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 to be described later. The pressure servo unit 7 adjusts the hydraulic pressure from the hydraulic pressure generation source 8 according to an input control signal, and controls the wheel cylinders 5L, 5R, 6L, 6R of each wheel. Control the brake fluid pressure (brake fluid pressure) supplied to the vehicle. The pressure servo unit 7 includes an actuator for each hydraulic pressure supply system (each channel) for the left, right, front and rear wheels. As an actuator, for example, anti-skid control (ABS control)
Which can be used in combination, and can be controlled to reduce, maintain and increase the pressure. The above pressure servo unit 7
With the actuator for controlling the hydraulic pressure of each supply system, the input hydraulic pressure command signal, more specifically, the left front wheel hydraulic pressure command value P1
*, 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
Shall constitute a pressure adjustment ~ P _4.

These signals are supplied from a controller (control unit) 9 to the pressure servo unit 7.
The controller 9, a signal from the steering angle δ steering angle sensor 11 for detecting the (steering wheel angle) of the steering wheel 10, a signal from the depression force sensor 13 for detecting a depression force F _P of the brake pedal 12, the vehicle A signal from the yaw rate sensor 14 that detects the actual yaw rate (d / dt) φ that acts, and the wheel speed (rotation speed) Vw ₁ , Vw ₂ , V for each wheel
Signals from the wheel speed sensors 15, 16, 17, and 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 brake fluid pressure difference control by the yaw rate feedback method.

The controller 9 includes a microcomputer and the like, and controls the vehicle behavior by the yaw moment at the time of braking, that is, controls the braking force by the yaw rate feedback system so that the vehicle behavior becomes a target characteristic. More specifically, the arithmetic processing circuit calculates a target yaw rate, a yaw rate difference value, and the like according to a control program described later, and uses the calculated values to control a target wheel cylinder fluid used for controlling a braking force (braking force) for each wheel. The pressure value (command value) is calculated, and a signal corresponding to the pressure value is output to the pressure servo unit 7. This allows
The pressure servo unit 7 adjusts the oil pressure from the oil pressure source 8 so that the actual wheel cylinder fluid pressure of each wheel matches the above-mentioned target fluid pressure, and the respective wheel cylinders 5L, 5R are used as braking fluid pressure. , 6L, 6R.

FIG. 3 is executed by the controller 9.
4 is an example of a control program for vehicle behavior control by controlling a difference in braking hydraulic pressure between left and right front wheels. This processing is performed by a periodic interrupt at a fixed time interval by an operating system (not shown). First, in step S110 in FIG. 3, the steering angle δ, the wheels 1L, 1R, and 2 are determined based on the output signals of the steering angle sensor, the pedaling force sensor, the wheel speed sensor, and the yaw rate sensor.
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 (body speed) is estimated based on the wheel speed Vw _j (j = 1 to 4). In this embodiment, using the wheel speeds Vw ₁ and Vw ₂ of the driven wheels (for example, front left and right wheels in the case of an FR vehicle), the vehicle speed is obtained by calculation from V = (Vw ₁ + Vw ₂ ) / 2.

In the next step S112, the brake pedal force F
Calculating a reference value P ₀ of the brake pressure from _P. In this embodiment, obtaining the reference value P ₀ 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 pressing force F _P , but is determined by a function of the brake pressing force; P ₀ = f (F _P ) so as to match the driver's feeling. Is also good.

Next, in order to control the braking force of the yaw rate feedback system during braking, the vehicle speed V is set at step S113.
And the steering angle δ, the target yaw rate (d / dt) φ _ref is calculated. In this embodiment, the target yaw rate is calculated according to the following equation (note that the vehicle speed V
And the steering angle δ may be obtained from a map representing a certain characteristic).

(Equation 4) Here, A is a constant determined by the wheelbase and the steering gear ratio of the vehicle, and K is a constant representing the steering characteristic of the vehicle. In this step S113,
The controller 9 functions as a vehicle target behavior state calculation unit.

In the next step S114, the above step S
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), is given by the following equation:

(Equation 5) It is calculated 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, it is assumed that only the front wheels are steered.

(Equation 6) Here, N is a proportional constant determined by vehicle specifications such as a steering gear ratio and steering rigidity. When the present invention is applied to a vehicle provided with a rear wheel assist steering device, the actual steering angle δr of the rear wheel is obtained by the same calculation in order to generate a differential pressure on the rear wheel. In this step S115,
The controller 9 functions as a steering angle detecting means.

In the next step S116, a target differential pressure to be generated on the left and right wheels is calculated. In the present embodiment, step S11
4. The yaw rate difference value Δ (d / dt) φ obtained in
Based on the actual steering angle δf obtained in step 115, for example, the product of the target gain and the feedback gain Ks determined from the characteristic diagram of FIG. Calculate according to

(Equation 7) In step S116, the controller 9 functions as a braking / driving force difference setting unit and a left / right braking / driving force difference correcting unit.

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. Calculation of the wheel cylinder pressure target value Pj * is, in this embodiment, the reference value P ₀ and the target lateral differential pressure ΔP of the brake pressure is calculated according to the following equation.

(Equation 8)

(Equation 9)

(Equation 10)

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

Here, for the sake of simplicity, the left-right difference is generated only on the front wheel side. However, the left-right difference may be generated only on the rear wheel or on both the front and rear wheels. In addition, the left-right distribution control may be performed by one-side pressure reduction control. Further, the rear wheel side liquid pressure may be decreased in a conventional manner with respect to the reference wheel cylinder pressure P _0.

After the target wheel cylinder hydraulic pressure of each wheel is determined in step S117, in step S118,
The brake fluid pressure control is performed so that the actual wheel cylinder fluid pressure (brake fluid pressure) of each wheel becomes the target fluid pressure. The processing consists of processing for individually determining a control signal (PjA *) corresponding to the target wheel cylinder hydraulic pressure Pj * and outputting the control signal to the pressure servo unit 7. By supplying these signals to the unit, each wheel is controlled. wherein the wheel cylinder pressure P ₁ to P ₄ are adjusted actual wheel cylinder pressure Pj to control the target fluid pressure Pj * of the wheel cylinders 5L of each wheel, and that given 5R, 6L, the 6R I do.

In this embodiment, by executing the above-described control, as shown in FIG. 4, a desired yaw moment is obtained by a feedback gain (proportional constant) Ks ₀ determined by vehicle specifications when the vehicle is going straight (at a small steering angle). When turning (a large steering angle) in a situation where the driver truly wants to generate a yaw moment, the feedback is determined according to the steering angle δr and is much larger than Ks _0. Gain K
s prevents the decrease in the yaw moment actually generated by compensating for the shortage caused by the change in the steering angle of the yaw moment of the vehicle generated by the braking force difference between the left and right steered wheels, thereby preventing the actually generated yaw moment from decreasing. Vehicle behavior control.

In the above-described embodiment, a case has been described in which the braking force of the left and right steered wheels is controlled by yaw rate feedback. Alternatively, a vehicle in which the steered wheels and the drive wheels are common and the drive 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 controlled by yaw rate feedback. In this case, the same operation and effect can be obtained. In the above embodiment, the target wheel cylinder hydraulic pressure
Although the case where Pj * is corrected in accordance with the steering angle δr has been described, instead, a map or the like may be looked up using the steering angle δr to directly calculate parameters relating to the target behavior state or the braking / driving force difference. Good.

In the above embodiment, the yaw rate feedback type braking force control is used as the basic braking force control. However, a vehicle model (vehicle characteristics) is provided in the controller, and the braking force is fed forward. Also in the case of 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 the so-called proportional control. However, a control method in which one or both of the differential operation and the integral operation is added may be adopted instead. In the above embodiment, the feedback gain Ks is changed at the time of a large steering angle in order to prevent the fluctuation of the control effect from becoming larger than at the time of a small steering angle. However, a predetermined correction amount is added instead. It may be corrected in advance when calculating the yaw rate.

Further, in the above embodiment, the absolute differential pressure is changed, but instead, the lateral movement state of the vehicle is detected, and the target slip ratio on the left and right is changed according to the deviation on the left and right, resulting in the result. In the control for generating the differential pressure between the left and right wheels, 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.

[0030]

As described above, the vehicle behavior control device of the present invention compensates for the shortage of the yaw moment of the vehicle caused by the difference in braking force or driving force between the left and right steered wheels due to the change in the steering angle. As a result, it is possible to prevent a change in the vehicle behavior state depending on the magnitude of the steering angle, and perform desired vehicle behavior control.

[Brief description of the drawings]

1 (a) and 1 (b) are conceptual diagrams of the present invention.

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

FIG. 3 is a flowchart showing a control program of vehicle behavior control based on a brake fluid pressure difference control between left and right front wheels executed by a controller in the same example.

FIG. 4 is a characteristic diagram illustrating a feedback gain used for the brake hydraulic pressure difference control in relation to an actual steering angle;

FIGS. 5A and 5B are diagrams illustrating a relationship between a steering angle and a vehicle behavior.

[Explanation of symbols]

 1L, 1R Left and right front wheel 2L, 2R Left and right rear wheel 3L, 3R, 4L, 4R Brake disc 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 Treading force sensor 14 Yaw rate sensor 15-18 Wheel speed sensor

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Naoki Maruko 2 Nissan Motor Co., Ltd., 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture (56) References JP-A-4-66357 (JP, A) JP-A-4 232127 (JP, A) JP-A-6-1158 (JP, A) JP-A-5-262153 (JP, A) JP-A 5-262154 (JP, A) JP-A 5-262155 (JP, A) ) Actually open 1988-98225 (JP, U) Actually open 1986-196825 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) B60T 8/58 B60T 8/24 B60K 23 / 04

Claims (3)

(57) [Claims] 1. A vehicle target behavior state calculating means for calculating a target behavior state of a vehicle, and a braking force difference between braking forces applied to left and right steering wheels or a driving force applied to left and right steering wheels according to the calculated target behavior state. Braking / driving force difference setting means for setting a driving force difference between the left and right driving wheels, and a left / right braking / driving force difference controlling 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. A vehicle behavior control device, comprising: 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, the vehicle yaw caused by the braking force difference or the driving force difference between the left and right steered wheels based on the steering angle detected by the steering angle detection means. Of the moment Characterized in that the shortage of the yaw moment caused by the change of the steering angle and so as to compensate, the vehicle behavior control device. 2. A steering angle detecting means when the vehicle target behavior state calculating means calculates a target behavior state of the vehicle, or when the braking / driving force difference setting means sets the braking force difference or the driving force difference. Correcting the braking / driving force difference so as to compensate for the shortage of the yaw moment of the vehicle caused by the braking force difference or the driving force difference between the left and right steered wheels based on the detected steering angle due to the change in the steering angle. 2. The vehicle behavior control device according to claim 1, wherein the left / right braking / driving force difference correcting means is provided in the braking / driving force difference setting means. 3. The braking / driving force difference correction means corrects the braking / driving force difference with a feedback gain determined based on a steering angle detected by a steering angle detection means. Item 3. A vehicle behavior control device according to item 2.