Anti-lock brake control system

A wheel lock control system for limiting the brake pressure applied to the brake of vehicle wheel, the system comprising:

• means for sensing wheel speed and
• control means, the control means including
• means for determining the brake pressure applied to the brake,
• means for determining the rate of change in the sensed wheel speed,
• means for detecting an incipient wheel lockup condition,
• means for reducing the brake pressure in response to a detected incipient wheel lockup condition to allow wheel speed recovery,
• means for determining the maximum tire torque tending to accelerate the wheel (A) during each period of application of brake pressure prior to a detected incipient wheel lockup condition and (B) during wheel speed recovery following each reduction of brake pressure in response to a detected incipient wheel lockup condition,
• means for storing the determined the brake pressure and the determined rate of change in wheel speed corresponding in time to the determined maximum tire torque during each period of application of brake pressure prior to a detected incipient wheel lockup condition,
• means for storing the determined brake pressure and the determined rate of change in wheel speed corresponding in time to the determined maximum tire torque during wheel speed recovery following each reduction of brake pressure in response to a detected incipient wheel lockup condition and
• means for applying brake pressure to the brake following wheel speed recovery with a value that is a predetermined function of the stored brake pressure and rate of change in wheel speed during the period of application of brake pressure prior to a detected incipient wheel lockup condition and the stored brake pressure and rate of change in wheel speed during wheel speed recovery after the detected incipient wheel lockup condition.

A wheel lock control system for limiting the brake pressure applied to the brake of a vehicle wheel, the system comprising:

• means for sensing wheel speed and
• control means, the control means including
• means for determining the brake pressure applied to the brake,
• means for determining the rate of change .omega. in the sensed wheel speed,
• means for detecting an incipient wheel lockup condition,
• means for reducing the brake pressure in response to a detected incipient wheel lockup condition to allow wheel speed recovery,
• means for determining the maximum value of tire torque T.sub.t tending to accelerate the wheel (A) during each period of application of brake pressure prior to a detected incipient wheel lockup condition and (B) during wheel speed recovery following each reduction of brake pressure in response to a detected incipient wheel lockup condition,
• means for storing a brake pressure value P.sub.1 of the determined brake pressure and a rate of change value .omega..sub.m in the determined rate of change in wheel speed corresponding in time to the determined maximum tire torque during each period of application of brake presusre prior to a detected incipient wheel lockup condition,
• means for storing a brake pressure value P.sub.2 and a rate of change value .omega..sub.r in the determined rate of change in wheel speed corresponding in time at the determined maximum tire torque during wheel speed recovery following each reduction of brake pressure in response to a sensed incipient wheel lockup condition and
• means for applying brake pressure to the brake following wheel speed recovery with a value P.sub.c defined by the expression P.sub.c =(.omega..sub.r P.sub.1 -.omega..sub.m P.sub.2)/(.omega..sub.r -.omega..sub.m).