Digital control circuit for producing acceleration and deceleration

Abstract

An antiskid control system for a vehicle in which acceleration and deceleration control signals are generated by a control circuit in accordance with the rotational speed of a wheel monitored by a sensor device that produces a pulse train whose frequency varies with wheel speed. A digital counter operates for the duration of each pulse cycle of the sensor signal whereby the pulse count obtained represents a cycle duration of the sensor signal. Within the control circuit to which the sensor signal is supplied, a control unit transfers the pulse count after each cycle to a first shift register as a measure of the cycle duration. The first shift register outputs the pulse count of the measured cycle duration to a comparator to which there is also connected a pulse count of a reference cycle duration supplied by a second shift register to which the pulse count of a previous measured cycle duration has been supplied by the first shift register to form the reference cycle duration. The reference cycle duration and measured cycle durations are compared to obtain a difference signal which is subsequently compared to an admissible difference signal to provide the acceleration and deceleration control signals when the difference exceeds a preselected amount. The admissible difference is formed as a fraction of the reference cycle duration by selecting an output of the second shift register corresponding to a preselected stage thereof.