Process for controlling the stability of vehicles

Details Process for controlling the stability of vehicles Process for controlling the stability of vehicles

1992-12-11

1994-07-26

Oberleitner, Robert J.

Fluid-pressure and analogous brake systems

Speed-controlled

Having a valve system responsive to a wheel lock signal

303110, 36442602, 180197, B60T 832

Patent

active

053323009

DESCRIPTION:

BRIEF SUMMARY
SUMMARY OF THE INVENTION

The invention relates to a process for controlling the stability of a vehicle, particularly during the negotiation of curves.
It is the object of the invention to stabilize a vehicle in all possible road and driving conditions while the vehicle is braking and to have the vehicle under control by the driver. Stabilizing is required, for example, when friction coefficients are different for the left and right wheels of the vehicle or if the vehicle is susceptible to oversteering during braking in curves. The vehicle is considered to be controllable if it reacts to steering in the manner desired by the driver.
This object, as well as other objects which will become apparent from the discussion that follows, are achieved, according to the present invention, by a process comprising the steps of: the vehicle forward speed v.sub.F and the coefficient of friction .mu. between the tires and road; curve of the yaw speed .PHI. as a function of the steering angle .delta. and in dependence upon the vehicle speed v.sub.F and the coefficient of friction .mu.; and falls below the limiting value curve or adjusting the brake pressure to vary the yaw speed in the direction of the desired value curve.
To optimize the brake system, the stability control can override another control or be integrated into the latter. The stability control requires sensors for the yaw movement and the steering angle of the vehicle and also information on the friction coefficient of the road and the vehicle speed. The coefficient of the friction, for example, can be computed from the highest possible vehicle deceleration. Vehicle deceleration and vehicle speed are generally known from the brake pressure regulator of the anti-lock braking system or they can be measured directly.
A desired value or a valid range for the yaw speed can be calculated from the steering angle, the speed of the vehicle and the coefficient of friction.
Possibilities of employing the yaw speed control to influence the brake force depend upon the number of brake channels; i.e., the number of groups of wheels to which the brake pressure can be independently applied.
A one-channel system permits only a common change of all wheel brake pressures. A pressure increase or reduction caused by the yaw speed control therefore always affects all wheels at once. A pressure increase must not cause both rear wheels to lock.
In a two-channel system, for example, each diagonal can be independently controlled. The manner in which the channels are influenced is dependent upon the sign of the yaw speed, the steering angle and other boundary conditions.
Three or four-channel systems permit the influence of brake pressure at each individual wheel.
For a full understanding of the present invention, reference should now be made to the following detailed description of the preferred embodiments of the invention and to the accompanying drawing.


BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a brake pressure control system where the invention is used as an overriding control,
FIG. 2 is a block diagram of an exemplary control system,
FIG. 3 and 5 are explanatory diagrams, and
FIG. 6 is a block diagram of another control system.


DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a one-channel configuration of an anti-lock braking system having a sensor 2 for the vehicle acceleration in the longitudinal direction of the vehicle, as indicated by the arrow. Actuating signals for a pressure regulator 5 are produced by a microprocessor-based control unit 4. The pressure regulator, for example a controllable brake force booster, can synchronously change the pressure in both brake circuits. As standard equipment of the vehicle, devices such as one or two load-controlled brake pressure reducers 6 are provided to adjust the brake pressure ratio between front and rear axles. With such a configuration, it is possible to advantageously combine the entire control system 3 into one unit which can replace the present brake force booster without requiring further modi

REFERENCES:
patent: 3910647 (1975-10-01), Takeuchi
patent: 4794538 (1988-12-01), Cao et al.
patent: 4862368 (1989-08-01), Kost et al.
patent: 4902076 (1990-02-01), Ushijima et al.
patent: 4998593 (1991-03-01), Karnopp et al.
patent: 5066074 (1991-11-01), Wupper

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