Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1992-06-10
1994-09-20
Oberleitner, Robert J.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
3031154, B60T 842
Patent
active
053483804
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
An Anti-lock brake system for controlling brakes of a wheeled vehicle comprising: measurement pick-ups, each for measuring a respective wheel speed and producing a respective wheel speed signal; an analysis circuit which receives the wheel speed signals and which generates respective brake pressure control signals; brake pressure control devices which are each activated by the respective brake pressure control signal to vary the brake pressure to prevent wheel lock; and a determining device, for determining a wheel brake pressure, which receives the brake pressure control signals and has stored data and curves characterizing particular hydraulics of the brakes of the wheeled vehicle is known from German Patent 2,555,403. In this, a brake pressure signal is reduced exponentially in pressure reduction phases and is increased exponentially in pressure build-up phases. The pressure signal obtained can be used for improving the control as, for example, in the patent specification quoted, or also, for example, for the reduction of yaw moments, for which the calculated front wheel pressures are compared with one another.
SUMMARY OF THE INVENTION
Comparison between the pressure signals obtained in accordance with the invention and the measured pressure values shows that the pressure signals obtained in accordance with the invention provide a very good approximation to the actual pressure values.
The invention defines both an anti-lock brake system and a method for controlling an anti-lock brake system where the brake pressure signal is calculated rather than measured. One embodiment of the invention is an anti-lock brake system for controlling brakes of a wheeled vehicle comprising: measurement pick-ups, each for measuring a respective wheel speed and producing a respective wheel speed signal; an analysis circuit for receiving the wheel speed signals, the analysis circuit having a determining device for determining an instantaneous wheel brake pressure p.sub.R (t), and using the wheel speed signals and the instantaneous wheel brake pressure to generate respective brake pressure control signals; brake pressure control devices which are each activated by the respective brake pressure control signal to vary the brake pressure to prevent wheel lock; and wherein the determining device uses the brake pressure control signals and stored data and curves characterizing particular hydraulics of the brakes of the wheeled vehicle to determine the instantaneous wheel brake pressure p.sub.R (t), with the determining device including: a device for calculating the instantaneous wheel brake pressure p.sub.R (t) in accordance with the relationship (t.sub.o)}(1-e.sup.-(t-t.sbsp.o.sup.)/t.sbsp.2) (t.sub.o).multidot.(1-e.sup.-(t-t.sbsp.o.sup.)/T.sub.1) change of pressure for a control cycle, p.sub.V (t.sub.o) is an admission pressure at the starting time, and T.sub.1 and T.sub.2 are time constants specific to the wheeled vehicle; a device for deriving the pressure values p.sub.V (t.sub.o) and p.sub.R (t.sub.o) at the starting time for the control cycle, from an instantaneous vehicle deceleration and constants specific to the vehicle; a device for comparing a pressure value, corresponding to the average lock-up pressure and obtained from the instantaneous vehicle deceleration at the starting time for each control cycle, to an average of calculated instantaneous wheel brake pressures for wheels of a front axle, to produce a correction value; and a device for adjusting the calculated instantaneous wheel brake pressure p.sub.R (t) using the correction value.
The relationship specific to the vehicle between the pressure values and the vehicle deceleration values is determined empirically and stored both with respect to the determination of the initial values p.sub.V (t.sub.o) and p.sub.R (t.sub.o) and for the determination of the average lock-up pressure.
BRIEF DESCRIPTION OF THE FIGURES
A preferred embodiment of the invention is explained by means of following drawings:
FIG. 1 shows a block circuit diagr
Brachert Jost
Herzmansky Karl-Heinz
Korasiak Wolfgang
Muller Elmar
Oberleitner Robert J.
Robert & Bosch GmbH
Young Lee W.
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