Anti-skid brake control system with control of sampling timing of input timing values of wheel speed sensor signal pulses

Claim 1

An anti-skid brake control system for an automotive vehicle comprising: a hydraulic brake circuit including a wheel cylinder for applying hydraulic braking pressure to a vehicle wheel; a pressure control valve disposed within said hydraulic brake circuit for controlling braking pressure to be applied to said wheel cylinder, said pressure control valve being operative to increase the braking pressure in said wheel cylinder in a first position thereof, to decrease the braking pressure in said wheel cylinder in a second position thereof and to hold the braking pressure at constant value in a third position thereof; a wheel speed sensor means for producing a sequence of sensor signal pulses having intervals representative of wheel rotation speed; a timer means sequentially outputting timer signals; a counter counting said sensor signal pulses to produce a counter signal when a value of said counter reaches a given count threshold; a first means for deriving an interval between adjacent sensor signal pulses and determining a number of sensor signal pulses to be needed in sampling of input timing value to form a group of a given number of sensor signal pulses so that the duration of said group is longer than a predetermined period which is necessary for accurate calculation of wheel speed, said first means comparing the duration of said group with said predetermined period to increment said count threshold to a given value for adjusting the number of said sensor signal pulses forming said group; a second means for sampling said input timing indicative timer signal values in response to said counter signal; a third means for deriving brake control parameters based on sampled input timing indicative timer signal values and producing a control signal to be fed to said pressure control valve to operate the latter to one of said first, second and third positions; and a fourth means for governing operations of said second and third means, said fourth means interrupting operation of said third means in response to every leading sensor signal pulse of every group of sensor signal pulses to operate said second means for sampling input timing indicative timer signal values, said fourth means further governing operation of said second means so that said second means samples the input timing indicative signal values of the sensor signal pulses immediately after terminating of operation of said first means and prior to said counter counting said sensor signal pulses to said given count threshold.