Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1985-08-16
1987-12-29
Caldwell, Sr., John W.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
303100, 303104, 303DIG4, 364426, B60T 832
Patent
active
047156627
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for determining an optimal slip value .lambda. of at least one wheel of a vehicle in order to regulate braking force, using signals (V.sub.R *; V.sub.F *) that are at least approximated to the wheel speed V.sub.R and the vehicle speed V.sub.F.
In anti-skid braking, the pressure in the wheel cylinder of the regulated wheel is regulated such that the tire slip is as nearly as possible within the range of the maximum coefficient of adhesion in braking. Accordingly, a good estimate of this maximum is a prerequisite for good anti-skid braking regulation. Typically, it is primarily the wheel acceleration that is monitored to this end.
The invention differs from this by ascertaining the .mu.-slip curve continuously by means of measurements and perhaps estimates of "measured values" and with the aid of mathematical substitution models. Once the course of this curve is known, the position of its maximum is known as well, and then the set-point value for the slip can be determined in accordance with the location of this maximum, possibly taking other parameters into account as well. For instance, when driving straight ahead, the set-point slip value can be set below the maximum by a predetermined small amount or percentage, and this amount or percentage can be increased when cornering, in order to increase lateral guidance.
In the invention, the identification methodology of identification is applied in order to ascertain the slip curve. This methodology is based on measurements and mathematical substitution models of physical processes. The mathematical substitution models here describe (1) the wheel under the influence of braking moment and braking force; (2) the tire as a slip curve; (3) the wheel brake cylinder under the influence of the pressure in the main brake cylinder and switching valve positions; and (4) the vehicle that is decelerated by the braking forces. The pressure in the main brake cylinder and the wheel speed are what is measured. An improvement and simplication of the identification could be attained if the pressure in the wheel brake cylinder and the vehicle speed could be measured. The regulator-controlled switching valve signals can also be used to calculate the brake pressure in the wheel brake cylinder. Based on the measurements and the mathematical models, the identification now furnishes parameter values from which the characteristic values of the slip curve, and hence the slip curve itself, can be determined.
The mathematical models, the identification methodolgy and the preparation (filtering) of the measurement signals are described below. A computer (microcomputer) can be programmed with the aid of the algorithms, in order thereby to determine the slip curve. An exemplary calculation concludes this description.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a mathematical substitution model for a brake-wheel-tire system;
FIG. 2 sets forth a program for carrying out the method;
FIGS. 3 and 4 illustrates different algorithms for shifting from a linear algorithm to a nonlinear algorithm shown in block form;
FIG. 5 illustrates a system for an averaging vehicle speed values which are delivered to the Kalman filter;
FIG. 6 illustrates a flow chart for identification of Kalman amplification factors stored in memory;
FIG. 7 sets forth calculations for dynamic changes in axle load of a vehicle shown.
BRAKE-WHEEL-TIRE SYSTEM
The mathematical substitution model for this system is sketched in FIG. 1.
The switching valve 1 is controlled by the ABS (anti-skid braking system) regulator not shown, which is well known in the prior art. In the position shown, the wheel brake cylinder 2 is connected to the main brake cylinder, and the pressure in the wheel brake cylinder 2 increases. In the middle position, the line to the wheel brake cylinder is interrupted, and the braking pressure in the wheel brake cylinder remains constant. In the lower position, the wheel brake cylinder communicates with the return line, and the pressure in the wheel brake cylinder decr
REFERENCES:
patent: 3131975 (1964-05-01), Smith et al.
patent: 3235036 (1986-02-01), Meyer et al.
patent: 3663069 (1972-05-01), Perry et al.
patent: 3744852 (1973-07-01), Riordan
patent: 4392202 (1983-07-01), Matsuda
Heess Gerhard
van Zanten Anton
Caldwell Sr. John W.
Greigg Edwin E.
Oberley Alvin
Robert & Bosch GmbH
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