Boots – shoes – and leggings
Patent
1987-02-04
1989-08-29
LaRoche, Eugene R.
Boots, shoes, and leggings
36442601, 303100, 303109, B60T 832
Patent
active
048623687
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for adjusting a vehicle wheel slip which is optimized in terms of the coefficient of adhesion in the longitudinal and transverse directions, hereinafter.
Methods for regulating wheel slip are known and are used for anti-skid or anti-lock control (see German Patent 30 09519, for example). In these known methods, a fixed maximum wheel slip (V.sub.F -V.sub.R /V.sub.F), of 15%, for instance, is specified, where V.sub.R =wheel speed and V.sub.F is the vehicle speed, and the brake pressure is regulated such that the slip is below this threshold.
It is an object of the present invention, during a regulated braking of a vehicle wheel, to set a wheel slip value at which on the one hand the coefficient of adhesion .mu. in the longitudinal direction is near the maximum attainable value, and on the other hand an adequate coefficient of adhesion is available in the transverse direction. The slip value required for this is below the value at which the coefficient of adhesion in the longitudinal direction is at a maximum.
This object is attained by means of the novel characteristics recited herein.
While the wheel slip curve .mu.(.lambda.) has a zero slope at the maximum coefficient of adhesion in the longitudinal direction, .mu.(.lambda.) assumes positive slopes at the slip value that is to be set. This is shown in FIG. 1. Besides the advantage of higher cornering forces, the teaching according to the invention makes a purposeful limiation of the yawing moments engaging the vehicle during regulated braking possible, thus improving control of the vehicle.
As a function of the specified set-point values, the control concept thus automatically finds a compromise between the maximum possible braking force and high cornering force on the part of the wheel. In contrast to existing control concepts, overly high wheel slip ranges with lower cornering force can be avoided. This property continues to exist even with quite various frictional ratios between the tires and the road.
The specified positive slope value can be specified as a fixed value (e.g., 3-5), but it can also be varied in accordance with instantaneous conditions, for example making it dependent on the steering angle and even making it assume a value of 0 when driving straight ahead, that is, when no coefficient of adhesion in the transverse direction is needed. The slope value can also be made dependent on other parameters, such as on the yawing acceleration of the vehicle.
The slip regulator to which the difference between the detected slip value and a comparison value is supplied may be embodied as a P (proportional) regulator, preferably receiving an I (integral) and/or D differential component as well. From the control variable ascertained by means of this regulator, the appropriate trigger signals are formed depending on the embodiment of the brake pressure control device (for example, a 3/3-way magnetic value). If the brake pressure specified by the driver and the prevailing brake pressure are measured, then the period of time for which the brake pressure control unit must be triggered into one or the other direction (pressure buildup or pressure reduction) can be calculated. However, operation without these measured pressure values is also possible.
It is also possible to specify pulse trains of a given frequency, and to vary the width of the pulses.
In the superimposed cascade control circuit, an estimated variable (identification) for d.mu./d.lambda. must be obtained, which is then compared with the fixed value or a variable slope value for ##EQU1## In the controller of the superimposed circuit, either a comparison slip value .lambda.*.sub.ref is formed, by means of the differential value, and the slip value .lambda..sub.ref dected in the usual manner is compared with the comparison slip value, the difference being processed in the underlying circuit, or the reference speed obtained in the usual manner, which of course represents only an approximation of the actual vehicle speed, is varied by means of the regulation proce
REFERENCES:
patent: 3131975 (1964-05-01), Smith et al.
patent: 3614172 (1971-10-01), Riordan
patent: 3967862 (1976-07-01), Hunter et al.
patent: 4679866 (1987-07-01), van Zanten et al.
patent: 4693522 (1987-09-01), Wupper et al.
patent: 4715662 (1987-12-01), van Zanten et al.
Heess Gerhard
Kost Friedrich
Kreisselmeier Gerhard
van Zanten Anton
Greigg Edwin E.
Ham Seung
LaRoche Eugene R.
Robert & Bosch GmbH
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