Method and apparatus for control of anti-skid vehicle braking system

Claim 1

In a vehicle having a wheel which engages a surface that the vehicle traverses, a brake through which braking force can be applied to the wheel to effect frictional retardation of the rotational speed of the wheel, a brake control element manually movable to and from a position in which braking force is produced, and regulator means for relieving braking force from the wheel in response to a brake releasing control input and for reapplying braking force to the wheel in response to a brake reapplying control input, so that the wheel can be alternately braked and released to prevent its locking, control means for said regulator means by which said control inputs are produced at such times as to assure deceleration of the vehicle substantially as quickly as conditions of said surface permit, said control means comprising: A. speed signal means for generating a speed signal which corresponds to the rotational speed of the wheel; B. differentiating means connected with the speed signal means to be responsive to the speed signal therefrom, for generating a deceleration output that corresponds to the rate of rotational deceleration of the wheel in response to applied braking force; C. deceleration reference signal generating means for generating a signal corresponding to a predetermined rate of rotational deceleration of the wheel, substantially equal to the maximum deceleration that the wheel could attain in sliding on a surface with which it had a substantially optimum coefficient of friction; D. deceleration comparison means for the wheel, connected with said differentiating means and with said deceleration reference signal generating means and which issues a brake releasing control input to said regulator means when the deceleration output of the differentiating means corresponds to a deceleration rate at least equal to that signified by the signal from the deceleration reference signal generating means; E. gradient signal generating means for the wheel for producing, beginning at each instant when a brake releasing control input is produced, a gradient signal which initially corresponds to the actual rotational speed of the wheel at said instant and including means for thereafter causing the gradient signal to correspond at each instant to the instantaneous rotational speed that the wheel would have if it had decelerated from said actual rotational speed at the maximum rate of deceleration that the vehicle could attain on a surface providing the lowest expectable friction with the wheel; and F. wheel speed comparison means connected with said speed signal means and said gradient signal means, for issuing a brake reapplying control input to said regulator means at that time after issuance of each brake releasing control input when rotational speed of the wheel becomes equal to the wheel speed then signified by the gradient signal.

Claim 3

The method by which a brake for a wheel of a vehicle can be temporarily released to prevent wheel locking and reapplied to obtain the optimum deceleration of the vehicle that is available on a surface traversed by the wheel, each release of the brake being effected in response to a release input to regulator means for the brake and each reapplication of the brake being effected in response to a restoration input to the regulator means, said method being characterized by: A. producing a wheel speed signal which at all times during braking corresponds to the prevailing rotational speed of the wheel; B. at times when the wheel is decelerating, differentiating said wheel speed sigNal to produce a wheel deceleration signal corresponding to the rate of deceleration of the wheel; C. producing a deceleration criterion signal which is comparable with said wheel deceleration signal and which corresponds to substantially the maximum rate of deceleration that the wheel could attain in sliding on a surface with which it had substantially the maximum attainable coefficient of friction; D. issuing a brake releasing input to the regulator means at each instant when the wheel deceleration signal becomes at least equal to the deceleration criterion signal; E. at each said instant beginning the generation of a speed criterion signal 1. which is comparable with the wheel speed signal, 2. which has an initial magnitude corresponding to the actual speed of the wheel at said instant, and F. so effecting the speed criterion signal as to produce thereafter an instantaneous magnitude corresponding to the rotational speed that the wheel would have had if it had decelerated from said actual speed at a rate corresponding to the maximum deceleration that the vehicle could attain on a surface providing the lowest expectable friction with the wheel; and G. issuing a restoration input to the regulator means when the magnitude of the wheel speed signal becomes equal to that of the speed criterion signal.

Claim 4

The method by which a brake for a wheel of a vehicle can be temporarily released to prevent wheel locking and reapplied to obtain the optimum deceleration of the vehicle that is available on a surface traversed by the wheel, each release of the brake being effected in response to a release input to regulator means for the brake and each reapplication of the brake being effected in response to a restoration input to the regulator means, said method being characterized by: A. producing a wheel speed signal which at all times during braking corresponds to the prevailing rotational speed of the wheel; B. at times when the wheel is decelerating, differentiating said wheel speed sigNal to produce a wheel deceleration signal corresponding to the rate of deceleration of the wheel; C. producing a deceleration criterion signal which is comparable with said wheel deceleration signal and which corresponds to substantially the maximum rate of deceleration that the wheel could attain in sliding on a surface with which it had substantially the maximum attainable coefficient of friction; D. issuing a brake releasing input to the regulator means at each instant when the wheel deceleration signal becomes at least equal to the deceleration criterion signal; E. at each said instant beginning the generation of a speed criterion signal 1. which is comparable with the wheel speed signal, 2. which has an initial magnitude corresponding to the actual speed of the wheel at said instant, and F. so effecting the speed criterion signal as to produce thereafter an instantaneous magnitude corresponding to the rotational speed that the wheel would have had if it had decelerated from said actual speed at a rate corresponding to the maximum deceleration that the vehicle could attain on a surface providing the lowest expectable friction with the wheel; and G. issuing a restoration input to the regulator means when the magnitude of the wheel speed signal becomes equal to that of the speed criterion signal.