An electronic control system is provided for monitoring the speed of a vehicle wheel, differentiating the speed signal to obtain the wheel deceleration rate and comparing the deceleration rate with a predetermined threshold to obtain a wheel skid control signal when the deceleration rate exceeds the threshold level. At the time a wheel skid control signal occurs, the threshold automatically increases in value in accordance with increasing rates of deceleration of the wheel so that upon a subsequent decrease in said deceleration signal incident to the wheel skid being corrected, the deceleration signal is reduced below the threshold signal to terminate the skid control signal at a point in time prior to the deceleration signal decreasing to the predetermined value of the threshold.

An anti-skid braking system for an automobile including apparatus for sensing rotational wheel speed, reference comparison apparatus for developing a signal indicating excessive rotational deceleration incident to incipient or actual skidding of the wheel for effecting brake relaxation and reference control apparatus for controlling the reapplication of braking effort.

A vehicle braking system for minimising the risk of skidding has a generator driven by a wheel for producing an electrical signal representing the angular speed of the wheel, this signal then being differentiated to produce a signal representing acceleration or deceleration. The brakes are released when the output of the differentiating circuit reaches a predetermined value, and at the point of release of the brakes the output of the differentiating circuit is clamped. The differentiating circuit includes an input capacitor and a feedback resistor which acts as a memory to monitor loss of wheel speed during the period between initiation of the release of the brakes and initiation of the re-application of the brakes. The memory permits unclamping of the differentiating circuit output and re-application of the brakes in a manner dependent on the monitored wheel speed loss signal.

An antiskid brake control system for a wheeled vehicle having a second order lead network in parallel connection with a deceleration detector. The deceleration detector includes both a current threshold level and a voltage threshold level, the deceleration rate of a wheel having to exceed both thresholds to result in a brake control signal to the modulator and brake control valves. The lead network, deceleration detector, and a modulator all feed a summing circuit which includes a switching circuit providing the system with two distinct characteristic gains. Also included is a circuit for linearly discharging certain capacitors in the system. Also included are locked wheel, touchdown protection, and low speed drop-out circuitry to regulate the application and release of antiskid control and touchdown and upon the occurrence of preselected vehicle activities.

In an anti-skid type control system for automotive vehicles, apparatus for maintaining wheel slip in a region of values associated with a maximum coefficient of road friction. Periodic modulation of the wheel brake torque in conjunction with wheel acceleration measurement are employed to determine the variation of the coefficient of road friction from an optimum value, while integral-plus-proportional control of the pulse modulation allows compensatory variation of the wheel torque and slip condition to a condition providing the optimum coefficient of road friction.