Antiskid control system

An antiskid control system for vehicles including a variable atenuation shock absorber in a wheel suspension, said variable attenuation shock absorber having an attenuation control means producing a high attenuation force in a "hard" condition and an actuator for driving said atenuation control means to the "hard" condition, comprising;

• a liquid brake pressure control valve unit having an intensifying position in which a brake wheel cylinder is connected to a brake master cyinder, a decompressing position in which the brake wheel cylinder is connected to a drain pressure and a holding position in which the brake wheel cylinder is disconnected from the brake master cylinder and the drain pressure;
• valve unit operator for driivng the liquid brake pressure control valve unit to the intensifying, decompressing and holding positions;
• means for detecting the rotation speed of a wheel, and control means for calculating a reference vehicle speed from the rotational speed of the wheel and its associated acceleration/deceleration, determining the need to decompress or intensify the liquid brake pressure when the relationship among the reference vehicle speed, the rotation speed of the wheel and the acceleration/deceleration of the wheel is in a predetermined decompression or intensifying range, respectively, supplying a position command signal to the valve unit operator based on the detemrination for establishing a decompressing/intensifying condition in the liquid brake pressure control valve unit to initaite antiskid control, and supplying an attenuation command signal to the actuator for driving said attenuation control means to the "hard" condition when the initiation of antiskid control is determined to prevent resonance of unsprung oscillations of the vehicle with oscillations in the liquid brake pressure upon the initaiton of antiskid control;
• wherein said control means supplies position command signals to said valve unit operator to drive asid control valve unit to said decompressing position and said holding position alternately when the control means determines said decompressing condition;
• said control means supplies said position commadd signals to said valve unit operator to drive said control valve unit to said intensifying position and said holding position alternately when the control means determines said intensifying condition;
• and
• said control means supplies said position command signals to said valve unit operator to drive said control valve unit to said intensifying position and holding position alternately at least two times when the determination changes from said decompressing condition to said intensifying condition.