JPH0370663A - Braking force control device of vehicle - Google Patents

Abstract

PURPOSE:To apply a brake with the suitable steering characteristic kept by individually controlling braking force in each wheel so as to attain both the target yaw rate, based on a steering condition and a speed of a vehicle, and the target deceleration based on stepping force of a brake pedal. CONSTITUTION:A steering condition of a vehicle is detected by a means (a), while a car speed is detected by a means (b). While stepping force of a brake pedal is detected by a means (c) simultaneously with an actual yaw rate of the vehicle detected by a means (d). While being based on the steering condition and the car speed, a target yaw rate of the vehicle is calculated in a means (e) simultaneously with target deceleration of the vehicle calculated in a means (f) being based on the stepping force. Further a differential value between the target yaw rate and the actual yaw rate is calculated in a means (g). Brake control force in each wheel, in which the target deceleration is satisfied further with the yaw rate differential value corrected in a zero direction, is calculated in a means (h), while braking force is controlled by a means (i) in accordance with an output of this means (h).

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a braking force control device for a vehicle, and in particular, when operating the brakes during turning, individual control of each wheel of play and kick taking into consideration the yaw rate. The present invention relates to a braking force control device for a vehicle.

(Prior Art) In recent years, various techniques have been proposed to perform the braking of a vehicle in a female-controlled manner, and the techniques in (G) and () have already been put into practical use.

For example, an anti-skin control device is a device that finely controls the braking force of each wheel and always controls the slip rate to around 10% to 30%, which is a device that controls the slip rate between the tires and the road surface. By making the most of the frictional force between the wheels, it is possible to shorten the stopping distance, and it is also possible to secure cornering force during turning braking, thereby improving the maneuverability and stability of the vehicle.

Furthermore, as another example, JP-A-63-13851
The "vehicle brake control device" described in the publication detects turning conditions, dynamically determines the load on each wheel, and operates the brake force on each wheel according to the load distribution, increasing the lock limit. It is possible to improve the braking feeling.

(Problem to be Solved by the Invention) However, in the first conventional example, each wheel speed and vehicle body speed are detected, and the slip ratio calculated from the detected values is always kept around 10% to 30%. In addition, in the second conventional example, the turning state of the vehicle is detected from the lateral acceleration of the vehicle, and the amount of load movement between the inner and outer wheels due to turning is taken into consideration. Although it is configured to control the brake force, and the brake force is controlled for each wheel during turning, it is not configured to perform control that focuses on the yaw rate generated by the vehicle.

Therefore, when the braking force or cornering force acting on each wheel changes, a yaw rate that is contrary to the driver's will may occur.Especially when braking is applied from near the turning limit, spin or drift may occur. There was a problem in that it could sometimes fall out.

(Objective of the Invention) Therefore, the present invention makes it possible to perform braking while maintaining desirable steering characteristics that are consistent with the steering and braking operations of the driver by individually controlling the wheel braking force while taking into account the yaw rate of the vehicle. The purpose is

(Means for Solving the Problems) In order to achieve the above object, the braking force control device for a vehicle according to the present invention provides a steering system that detects the steering state of the vehicle, as shown in FIG. A state detection means a, a vehicle speed detection means for detecting the vehicle body speed, a depression force detection means C for detecting the depression force of the brake pedal, a yaw rate detection means d for detecting the actual yaw rate of the vehicle, and the steering state detection means a. and target yaw rate calculation means e which calculates a target yaw rate of the vehicle based on the detected value of the vehicle speed detection means S, and target deceleration calculation means e which calculates the target deceleration of the vehicle based on the detected value of the pedal force detection means C. means f, yaw rate difference value calculation means g for calculating a difference value between the target yaw rate and the actual yaw rate, and a brake for each wheel that satisfies the target deceleration and corrects the yaw rate difference value toward zero. The vehicle includes a brake force calculation means for calculating a force control value, and a brake force operation means i for manipulating the brake force for each wheel based on an output signal from the brake force calculation means.

(Operation) In the present invention, the target yaw rate that should naturally be obtained from the steering condition and vehicle speed is calculated, and the target deceleration that should naturally be obtained from the brake pedal depression force is calculated, and both the target yaw rate and the target deceleration are calculated. To achieve this, the braking force for each wheel is individually controlled.

Therefore, during turning braking, an appropriate yaw rate can be generated depending on the amount of steering effort of the driver and the vehicle speed at that time, and braking can be performed while maintaining desirable steering characteristics.

(Example) Hereinafter, the present invention will be explained based on the drawings.

FIG. 2 is a diagram showing an embodiment of a braking force control device for a vehicle according to the present invention.

First, the configuration will be explained. In Figure 2, 1 to 4 are wheels, 5 to 8 are brake discs for each wheel, and 9 is a brake disc for each wheel.
~12 is a wheel cylinder that frictionally clamps a brake disc and applies braking force to each wheel by supplying hydraulic pressure, 13 is a steering handle, and 14 is a steering angle δ of the steering handle.
15 is a brake pedal, 16 is a pedal force sensor that detects the brake pedal depression force Fp, 17 is a vehicle speed sensor that detects ground vehicle speed V, and 18 is an actual yaw rate (yaw) acting on the vehicle. a sensor for the yaw angular velocity that detects the angular velocity) φ; 19 is a control unit; 2
0 is a hydraulic pressure generation source, 21 is a pressure servo unit, and the control unit 19 includes a microcomputer, etc., and calculates a target yaw rate φref, a target deceleration Gref, a yaw rate difference value Δφ, etc. according to a program described later. A target wheel cylinder pressure Pi''' is calculated as a brake force control value for each wheel based on each calculated value.The pressure servo unit 21 controls the pressure servo unit 21 so that the actual cylinder pressure for each wheel matches Fi9. The hydraulic pressure from the hydraulic pressure generating source 20 is adjusted and supplied to each wheel cylinder 9 to 12.The above-mentioned steering angle sensor 14 functions as a steering state detection means, the pedal force sensor 16 functions as a pedal force detection means, and the vehicle speed sensor 17 The control unit 7 functions as a vehicle speed detection means, and the control unit 19 functions as a target yaw rate calculation means, a target deceleration calculation means, a yaw rate difference value calculation means, and a brake force calculation means. 20 and pressure servo unit 21 function as a brake force operating means.

Next, the effect will be explained.

FIG. 3 is a flowchart of a program executed by the control unit 19.

In this flowchart, first, signals from each sensor, steering angle δ, vehicle speed V, brake pedal force Fp, and actual yaw rate J are read (step 101), and the following formula
Calculate the target deceleration G ref according to (Step 1
02).

Gref=to, Xp'p ・−・・=■However,
Fp: 1 for pedal force: proportionality constant Here, the target deceleration of the vehicle is treated as being proportional to the brake pedal force. Next, the target yaw rate (target yaw angular velocity) φref is calculated according to the following formula (Step 10
3).

Here, φref in the formula (2) is determined in relation to the target turning radius Rref when an arbitrary steering angle δ and vehicle speed V are given, and Rref is determined according to the following formula (2).

Rref =AX (1+kl XV") /δ...
...■ However, A: a constant determined by the vehicle's wheel base and steering gear ratio, k2: a constant representing the steering characteristics of the vehicle, -C, the steering characteristics that are said to be easy to drive are the so-called weak understeer characteristics It is said that this is ■2 in the formula kz
>0 and k z dan 0, that is, it can be expressed as a steering characteristic in which the turning radius does not increase much even when the vehicle speed V is increased while the steering angle δ is fixed. Therefore, in order to obtain this preferable steering characteristic, Rref is calculated when arbitrary δ and ■ are given, and in relation to this Rref, φ
You will need to find the ref.

Next, calculate the yaw rate difference value Δmount according to the following formula (step 104), Δφ = φref - φ...■, where φ is the actual jaw rate and the target wheel cylinder pressure Pi for each wheel. (
Each wheel is represented by a number from ill to 4) (step 105'').The relationship between the actual wheel cylinder pressure Pi and the braking force Fi is calculated by the following equation (2), assuming that the wheel slip is sufficiently small. Can be expressed.

ri ・・・・・・■ However, ai: Wheel cylinder area μpi: Friction coefficient between the pad and disc rotor, rpt: Distance from the center of the disc rotor to the pad ri: Tire rotation radius Therefore, target deceleration G ref The relationship expressed by the following equation (2) holds true between the target wheel cylinder pressure Pi'' and the target wheel cylinder pressure Pi''.

However, (ri: (2XatX/JPtXrPi/r
t) W: Vehicle weight For simplicity, set the target wheel cylinder pressures of the front and left wheels on the same side to be the same (P, ” = P, ”, P2'” = P4')
Also, α, = α2 = αf (f: front)
, α3=α4=α, (r: rear), the previous equation becomes
It can be expressed as the following formula (■).

Gref = ((1'r+αr) (P +
"10P z'")......■ Here, the target wheel cylinder pressure difference (the difference in braking force between the left and right wheels) that causes the vehicle to generate a yawing torque that makes the yaw rate difference value Δφ determined by the braking formula ■ zero ), if we set the feed bank gain for Δφ at this time, we get
It is determined by the following formula (■).

P I” P z” = k: lxΔφ ・・・・・・
-■ Then, from the previous equations (■) and (2), PI* to P4' are determined as follows (step 105). [Phase] In the formula, p
, m or Pi may take a negative value; in this case, the target wheel cylinder pressure may be set to zero (
Steps 106-109). Further, although a so-called proportional control method is used as a feedback control method for Δφ, the present invention is not limited to this, and a control method that includes either or both of differential operation and integral operation may be used. In this way, the responsiveness and stability of the vehicle's actual yaw rate to the target yaw rate can be improved.

The signal corresponding to the target wheel cylinder pressure Pt" for each wheel determined in this way is input to the pressure servo unit 21, and the actual wheel cylinder pressure Pt (hydraulic pressure) is adjusted according to this Pi". provided to wheel cylinders 9-12 for each wheel. Therefore, according to this embodiment, the generated yaw rate of the vehicle is directly detected, the target yaw rate is calculated from the steering state and the vehicle speed, the target deceleration is calculated from the brake pedal force, and the actual yaw rate (yaw rate) of the vehicle is calculated. The brake force for each wheel is individually controlled so that the angular velocity (angular velocity) and deceleration are within the same range as each of the above target values. An appropriate yaw rate can be generated, and braking can be performed while maintaining favorable steering characteristics (weak understeer).

<Effects> According to the present invention, since the wheel braking force is individually controlled in consideration of the yaw rate of the vehicle, braking can be performed while maintaining desirable steering characteristics that match the driver's steering and braking operations. I can do it.

[Brief explanation of drawings]

Fig. 1 is a basic conceptual diagram of the present invention, Figs. 2 and 3 are diagrams showing an embodiment of a braking force control device for a vehicle according to the present invention, Fig. 2 is a configuration diagram thereof, and Fig. 3 is a diagram showing an embodiment of the braking force control device for a vehicle according to the present invention. is a flowchart of the program. 1-4...wheels, 5-8...brake discs, 13...
- Steering handle, 14... Rudder angle sensor (steering state detection means), 1
5...brake pedal, 16...treading force sensor (treading force detection means), 17...
...Vehicle speed sensor (vehicle speed detection means), 18...
... Yaw angular velocity sensor (yaw rate detection means), 19.
--- Control unit (target yaw rate calculation means, target deceleration calculation means, yaw rate difference value calculation means, brake force calculation means),

Claims (1)

[Scope of Claims] a) Steering state detecting means for detecting the steering state of the vehicle; b) Vehicle speed detecting means for detecting the vehicle body speed; c) Depressing force detecting means for detecting the depressing force of the brake pedal; d) yaw rate detection means for detecting the actual yaw rate of the vehicle; e) target yaw rate calculation means for calculating a target yaw rate of the vehicle based on the detected values of the steering state detection means and the vehicle speed detection means; and f) the pedal force detection means. g) target deceleration calculation means for calculating a target deceleration of the vehicle based on the detected value; g) yaw rate difference calculation means for calculating a difference between the target yaw rate and the actual yaw rate; and h) yaw rate difference calculation means for calculating the target deceleration. satisfied,
and a brake force calculation means for calculating a brake force control value for each wheel to correct the yaw rate difference value toward zero; i) operating the brake force for each wheel based on the output signal of the brake force calculation means; A braking force control device for a vehicle, comprising: a braking force operating means for controlling the braking force;