JPH07228235A - Turning behavior control device for vehicle - Google Patents

Abstract

PURPOSE:To obtain desired turning behavior without being influenced by a change in a road surface (mu), and reduce the cost by obveating an expensive sensor in a wheel speed control device for a vehicle. CONSTITUTION:A turning behavior objective value to show objective turning behavior of a vehicle is set (M3) from detected steering operation and vehicle speed. Objective wheel speeds of respective four wheels are calculated (M4) by calculating at least one of an objective wheel speed longitudinal difference and an objective wheel speed lateral difference according to a preset turning behavior objective value. The wheel speeds of the respective wheels are independently controlled according to the calculated objective wheel speeds of the respective wheels.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turning behavior control device for a vehicle, and more particularly to a turning behavior of a vehicle which is controlled so that the turning behavior of the vehicle matches a target turning behavior determined according to a steering operation by a driver. Regarding the control device.

[0002]

2. Description of the Related Art Conventionally, there has been known a technique for improving turning performance of a vehicle by using a brake.

For example, the one disclosed in Japanese Patent Application Laid-Open No. 4-66357 detects a vehicle speed and a steering angular velocity, and a difference in braking force between a wheel on the inside of a turn and an outer wheel is detected according to the vehicle speed and the steering angular velocity. This improves the turning performance and stability of the vehicle.

[0004]

Since the conventional device controls the braking force of each wheel in accordance with the vehicle speed and the steering angular velocity, when the friction coefficient μ of the road surface (hereinafter referred to as road surface μ) is low, the vehicle speed and the steering angular velocity are the same. Even if each wheel is controlled with the braking force obtained from the above, there is a problem in that the expected wheel speed cannot be obtained and the desired turning behavior cannot be obtained.

Further, conventionally, a device for detecting a yaw rate or a vehicle body sideslip angle of a vehicle and controlling a braking force of each wheel according to a deviation between the yaw rate or the vehicle body sideslip angle and a target yaw rate or a vehicle body sideslip angle obtained from a vehicle speed and a steering angle is provided. However, a very expensive yaw rate sensor or vehicle body sideslip angle sensor is required, and there is a problem that the cost becomes high.

The present invention has been made in view of the above points,
By obtaining the wheel speed difference of each of the four wheels to obtain the target turning behavior obtained from the vehicle speed and the steering angle and obtaining the target wheel speed of each wheel, the desired turning behavior is obtained without being affected by the change in the road surface μ. It is an object of the present invention to provide a turning behavior control device for a vehicle, which is capable of reducing the cost because an expensive sensor is unnecessary.

[0007]

FIG. 1 shows the principle of the present invention.

In the figure, steering operation detecting means M1 detects the steering operation of the driver.

The vehicle speed detecting means M2 detects the vehicle speed. The target setting means M3 sets a turning behavior target value representing a target turning behavior of the vehicle based on the detected steering operation and the vehicle speed.

The target wheel speed calculation means M4 calculates at least one of the target wheel speed front-back difference based on the set turning behavior target value and the target wheel speed left-right difference, and calculates the target wheel speed of each of the four wheels. .

The control means M5 independently controls the wheel speed of each wheel based on the calculated target wheel speed of each wheel.

[0012]

In the present invention, the wheel speed difference of each of the four wheels is determined so that the turning behavior target value obtained from the vehicle speed and the steering angle is obtained.
Since the target wheel speed of each wheel is obtained and the wheel speed of each wheel is controlled so as to match the target wheel speed, a desired turning behavior can be obtained without being affected by changes in the road surface μ. Further, since the turning behavior target value is calculated from the vehicle speed and the steering angle, an expensive sensor is unnecessary.

[0013]

FIG. 2 is a block diagram of an embodiment of the device of the present invention. In the figure, when the brake pedal 10 is depressed, hydraulic pressure is generated in each of the two pressurizing chambers of the master cylinder 12. Each pressurizing chamber of the master cylinder 12 has two-position switching valves 14, 15
It is connected to each one. The two-position switching valve 14 has a main passage 16
The two-position changeover valves 17 and 1 corresponding to the front wheels on the left and right respectively.
The two-position changeover valve 15 is connected to each of the eight position changeover valves 15 and the two-position changeover valve 15 is connected to each of the two position changeover valves 20 and 21 corresponding to the right and left rear wheels by a main passage 19.

The pump 25 has one end connected to the reservoir 26 and the other end connected to the accumulator 28 via the check valve 27, and the brake fluid is supplied from the reservoir 26 to the hydraulic accumulator 28 and stored therein. . A relief valve 29 is provided between the check valve 27 and the hydraulic accumulator 28.

The hydraulic accumulator 28 is connected to each of the linear hydraulic control valves 31, 32, 33 and 34, and the discharge brake fluid of each of these control valves 31 to 34 is passed through the passage 35 to the reverser 26. Will be returned. Each of the linear hydraulic pressure control valves 31 to 34 is a two-position switching valve 17, 18, 2
Two-position switching valves 17, 1 connected to 0, 21 respectively
8, 20, 21 are wheel cylinders 41, 42 of the right front wheel 36, left front wheel 37, right rear wheel 38, left rear wheel 39, respectively.
43 and 44 are respectively connected.

The electronic control unit (ECU) 50 has wheels 36.
.About.39 wheel speed signals for detecting the wheel speeds, a steering angle signal for detecting the steering angle of the steering wheel, and a pedaling force signal for detecting the pedaling force of the brake pedal 10, respectively.
The ECU 50 performs various calculations based on the above signals, and supplies drive control signals to the drive circuits 51 and 52 as needed.

The drive circuit 51 supplies a drive signal to each of the linear hydraulic pressure control valves 31 to 34 based on the drive control signal to vary the brake hydraulic pressure of each, and the drive circuit 52 switches between two positions based on the drive control signal. Valves 14, 15, 17, 18, 2
A drive signal is supplied to each of 0 and 21 to switch their positions.

During normal traveling, 2 is controlled by the ECU 50.
The position switching valves 14, 15, 17, 18, 20, 21 are switched to the positions shown in FIG. 2, and the hydraulic pressure of the master cylinder 12 according to the pedaling force of the brake pedal 10 is supplied to the wheel cylinders 41 to 44, so that the wheels are rotated. Braking of each of 36 to 39 is performed.

Further, at the time of antilock brake (ABS) control and turning control, the two-position switching valves 14, 15, 17, 18, 20, 21 are controlled by the ECU 50 as shown in FIG.
The positions are switched to the positions opposite to the positions shown in (4), and the hydraulic pressures of the linear hydraulic pressure control valves 31 to 34 controlled by the ECU 50 are supplied to the wheel cylinders 41 to 44 to brake the wheels 36 to 39, respectively.

FIG. 3 shows a flow chart of the first embodiment of the turning control processing executed by the ECU 50 of the device of the present invention. This process is executed, for example, every 6 to 10 msec. In the figure,
In step S10 corresponding to the steering operation detecting means M1, the steering angle θ and the wheel 3 as steering operation detected by each sensor
The wheel speeds V _W of 6 to 39 are read. Further, in step S12 as the vehicle speed detection means M2, the vehicle speed V is set to the wheel
It is calculated from the wheel speed V _W of the driven wheels among 6 to 39. Next, in step S14, it is determined whether or not ABS control is in progress. If ABS control is not in progress, the process ends, and if ABS control is in progress, the process proceeds to step S16.

In step S16, the four-wheel reference wheel speeds Vfr, Vfl, Vrr, Vrl are calculated from the vehicle speed V. Here, for example, values obtained by reducing the vehicle speed V by several percent are set as four-wheel reference wheel speeds Vfr, Vfl, Vrr, and Vrl.

Next, in step S18 corresponding to the target setting means M3, from the vehicle speed V and the steering angle θ, the target yaw rate γ ^* and the target vehicle body sideslip angle β ^*, which are the turning behavior target values, are calculated by the equations (1) and (2) ^. To calculate.

[0023]

[Equation 1]

Ω _n and ζ are the resonance frequency and damping coefficient of the vehicle m is the vehicle weight I is the moment of inertia Kf of the vehicle, Kr is the cornering power Lf of the front and rear wheels, and is the front wheel base (from the center of gravity to the center of the front axle). Distance) Lr, is the rear wheel base (distance from the center of gravity to the rear wheel axle center) L is the wheel base (the distance from the front wheel axle center to the rear wheel axle center) A is the stability factor N is the steering gear ratio s is Laplace calculation Here, in general, when the steering angle is small during non-braking and non-driving, the yaw rate γ and the wheel speed V of the right and left wheels shown in FIG.
The relationship between _RH and _VLH is expressed by the following equation.

Γ = (V _RH -V _LH ) / t where t is the wheel tread, and γ ^* is substituted for this to express the target wheel speed left / right difference ΔV ₁ ^* by the following equation.

ΔV ₁ ^* = V _RH −V _LH = t · γ ^* (3) Further, the yaw rate γ during non-braking and non-driving, the vehicle side slip angle β, the front wheel actual steering angle δ (≈θ / N), The relationship between the wheel speeds V _F and V _R of the front wheels and the rear wheels is expressed by the following equation.

[0027] beta = Therefore _{(V F / V R -cos δ} ) / sin δ-Lf · γ / V R, where _{V F = (cos δ + sin} δ · β) V R + Lf · γ · sin δ, a steering angle When δ is small, sin δ≈δ, cos δ≈1
Because it _{is, V F = (1 + δβ} ) V R + Lf · γ · δ ∴V F -V R = (V R · β + Lf · γ) δ This alpha ^*, by substituting beta ^* target wheel speed difference across ΔV ₂ ^*
Is expressed by the following equation. ^{_{Δ V 2 * = V F -V}} R = (V R · β * + Lf · γ *) θ / N ... (4) In step S20 (3) equation (4) target wheel speed difference between right and left ΔV using equation ₁ ^* and target wheel speed front-back difference ΔV ₂ ^* are calculated. Thereafter, the target wheel speed of each wheel by the following equation Vfr ^* in step S22, Vfl ^*, Vrr ^*, seek Vrl ^*.

[0028] _{^{Vfr * = Vfr + ΔV 1 *}} / 2 + ΔV 2 * / 2 Vfl * = Vfl-ΔV 1 * / 2 + ΔV 2 * / 2 Vrr * = Vrr + ΔV 1 * / 2-ΔV 2 * / 2 Vrl * = Vrl-ΔV 1 _{^{* / 2-ΔV 2 * /}} 2 above steps S20, S22 corresponds to the target wheel speed calculation means M4.

Further, step S24 which is the control means M5.
So that the brake fluid pressure is applied to each of the wheel cylinders 41 to 44 of the wheels 36 to 39 so that the target wheel speed is achieved.
Also, the linear hydraulic pressure control valves 31 to 34 are driven, and the processing is ended.

FIG. 5 shows a block diagram of the process shown in FIG. In the figure, the estimated vehicle speed calculator 60 calculates the vehicle speed V from the wheel speeds V _W of the four wheels. The four-wheel reference vehicle speed calculation unit 61 calculates from the vehicle body speed V to the reference wheel speeds Vfr, Vfl, Vr.
Calculate r and Vrl.

The target model 62 calculates the target yaw rate γ ^* and the target vehicle body sideslip angle β ^* from the vehicle speed V and the steering angle θ by the equations (1) and (2). Further, the target model 63 uses the target yaw rate γ ^* to calculate the target wheel speed left / right difference ΔV ₁ ^*.
Then, the target model 64 calculates the target wheel speed front-back difference ΔV ₂ ^* using the target yaw rate γ ^{*, the} target vehicle side slip angle β ^*, and the steering angle θ. The mixer 65 is a model 61, 6
4 wheel reference wheel speeds Vfr, Vfl, V from 3, 64 respectively
The target wheel speed left / right difference ΔV ₁ ^* and the target wheel speed front / rear difference ΔV ₂ ^* are added to and subtracted from rr and Vrl to obtain a four-wheel target wheel speed Vf.
^{r *, Vfl *, Vrr *} , calculates and outputs the Vrl ^*.

In this embodiment, during ABS control, the wheel speed difference between each of the four wheels is calculated to obtain the target yaw rate obtained from the vehicle speed and the steering angle and the target vehicle side slip angle, and the target wheel speed of each wheel is obtained. , To control the wheel speed of each wheel,
Even if the road surface μ changes, a desired turning behavior according to the vehicle speed and the steering angle can be obtained, stable turning can be performed, and an expensive sensor such as a yaw rate sensor or a vehicle side slip angle sensor is unnecessary.

FIG. 6 shows a flowchart of the second embodiment of the turning control processing. In this embodiment, the wheel speed is controlled even before the ABS control is started, and the same parts as those in FIG. 3 are designated by the same reference numerals.

In FIG. 6, in step S10, the steering angle θ detected by each sensor and the wheel speed V _{W of} each of the wheels 36 to 39 are detected.
Is read, the vehicle speed V is obtained in step S12, and then the four-wheel vehicle speed V _W is directly used as the four-wheel reference wheel speed V in step S30.
fr, Vfl, Vrr, and Vrl.

Next, in step S18, the vehicle speed V and the steering angle θ
From equations (1) and (2), the target yaw rate γ ^* and the target vehicle body sideslip angle β ^* are calculated, and in step S20, the target wheel speed left / right difference ΔV ₁ ^* is calculated using equations (3) and (4) ^.
And the target wheel speed front-back difference ΔV ₂ ^* is calculated.

Thereafter, it is determined in step S32 whether the target wheel speed left / right difference ΔV ₁ ^* is greater than 0, and then in steps S34 and S36 it is determined whether the target wheel speed front-rear difference ΔV ₂ ^* is greater than 0. Determine. As a result, ΔV ₁ ^* ≦ 0,
If ΔV ₂ ^* ≦ 0, the process proceeds to step S40, and the target wheel speeds Vfr ^* , Vfl ^* , Vrr ^* , Vrl ^* of the respective wheels are referenced by the following equation using the reference wheel speed Vrl of the left rear wheel as a reference ^.
To calculate.

[0037] _{^{Vfr * = Vrl + ΔV 1 *}} + ΔV 2 * Vfl * = Vrl + ΔV 2 * Vrr * = Vrl + ΔV 1 * Vrl * = Vrl Further, [Delta] V ₁ ^* ≦ 0 and, in the case of [Delta] V ₂ ^*> 0 the process proceeds to step S42 , The reference wheel speed V of the left front wheel by the following equation
Target wheel speeds Vfr ^* , Vfl of each wheel with fl as a reference
^*, Vrr ^*, to calculate the Vrl ^*.

[0038] _{^{Vfr * = Vfl + ΔV 1 *}} Vfl * = Vfl Vrr * = Vfl + ΔV 1 * -ΔV 2 * Vrl * = Vfl-ΔV 2 * Further, [Delta] V ₁ ^*> 0 and, step in the case of [Delta] V ₂ ^* ≦ 0 Proceeding to S44, the target wheel speeds Vfr ^* , Vf of the respective wheels are calculated by the following equation with reference to the reference wheel speed Vrr of the right rear wheel.
l ^*, Vrr ^*, to calculate the Vrl ^*.

[0039] _{^{Vfr * = Vrr + ΔV 2 *}} Vfl * = Vrr-ΔV 1 * + ΔV 2 * Vrr * = Vrr Vrl * = Vrr-ΔV 1 * Also, ΔV ₁ ^*> 0, and, in the case of ΔV ₂ ^*> 0 is Proceeding to step S46, the target wheel speeds Vfr ^* , Vf of the respective wheels are calculated based on the reference wheel speed Vfr of the right front wheel by the following equation.
l ^*, Vrr ^*, to calculate the Vrl ^*.

[0040] ^{Vfr * = Vfr Vfl * = Vfr} -ΔV 1 * Vrr * = Vfr-ΔV 2 * Vrl * = Vfr-ΔV 1 * - ΔV 2 * Furthermore, each wheel 36 so that the target wheel speed in Step S24 2-position switching valves 14, 15, 1 so that the brake fluid pressure is applied to each of the wheel cylinders 41-44.
7, 18, 20, 21 and linear hydraulic control valves 31-34
Drive, and the process ends.

In this embodiment, the wheel speed difference between each of the four wheels is calculated so that the target yaw rate obtained from the vehicle speed and the steering angle and the target vehicle sideslip angle are calculated not only during the ABS control but the target wheel speed of each wheel is calculated. In order to control the wheel speed of each wheel,
Even if the road surface μ changes, a desired turning behavior is obtained according to the vehicle speed and the steering angle, stable turning can be performed, and an expensive sensor such as a yaw rate sensor or a vehicle body side slip angle sensor is unnecessary.

The present invention controls the front and rear or left and right wheel speeds by changing the characteristics of the proportioning valve or the LSPV (load sensing proportioning valve) before entering the ABS control. It can also be applied to possible systems, only front and rear wheel speeds,
Alternatively, it can be applied to a system that controls the wheel speed of only the left and right wheels. Further, instead of controlling the braking force of each wheel in step S24, the driving force of each wheel may be independently controlled, and the present invention is not limited to the above embodiment.

[0043]

As described above, according to the vehicle wheel speed control device of the invention, the wheel speed difference of each of the four wheels is calculated so as to obtain the target turning behavior obtained from the vehicle speed and the steering angle, and the target of each wheel is calculated. Since the wheel speed of each wheel is controlled by obtaining the wheel speed, the desired turning behavior can be obtained without being affected by the change in the road surface μ,
You don't need expensive sensors, you can keep costs low,
It is extremely useful in practice.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a configuration diagram of the device of the present invention.

FIG. 3 is a flowchart of turning control processing.

FIG. 4 is a diagram for explaining the present invention.

5 is a block diagram of the process of FIG.

FIG. 6 is a flowchart of turning control processing.

[Explanation of symbols]

 10 Brake Pedal 12 Master Cylinder 14, 15, 17, 18, 20, 21 2 Position Switching Valve 25 Pump 26 Reverser 27 Check Valve 28 Hydraulic Accumulator 31-34 Linear Hydraulic Control Valve 36-39 Wheel 41-44 Wheel Cylinder 50 electronic control device 51,52 drive circuit M1 steering operation detection means M2 vehicle speed detection means M3 target setting means M4 target wheel speed calculation means M5 control means

Claims (1)

[Claims] 1. A steering operation detection means for detecting a steering operation of a driver, a vehicle speed detection means for detecting a vehicle speed, and a turning behavior target value representing a target turning behavior of a vehicle from the detected steering operation and the vehicle speed. The target wheel speed front-back difference based on the set turning behavior target value and the target wheel speed left-right difference are calculated to obtain 4
A vehicle turning characterized by having target wheel speed calculation means for calculating the target wheel speed of each wheel and control means for independently controlling the wheel speed of each wheel based on the calculated target wheel speed of each wheel. Behavior control device.