Antilock system with proportional control and pressure memory

An antilock brake system for a wheeled vehicle having wheel brakes and a driver actuated master brake cylinder, wheel speed sensor means for detecting wheel speeds, an electronic controller means for detecting an incipient wheel lockup in response to wheel speeds detected by said wheel speed sensor means, said controller means including memory registers for storing motor voltage during operation of said antilock brake system and a brake pressure distribution circuit connecting said master brake cylinder and said wheel brakes;

• a power cylinder assembly having a brake pressure piston, an electric motor means for powering said piston and a selectively engageable clutch means for drivably connecting said motor means to said piston;
• a solenoid-operated valve means in said pressure distribution circuit having a first state in which said master cylinder is connected to said wheel brakes and a second state in which said master cylinder is isolated from said wheel brakes, said power cylinder assembly being connected to said wheel brakes when said valve assembly assumes said second state;
• means for applying a controlled memory voltage to said motor means when said clutch means is disengaged to accelerate rotary portions thereof, thereby storing rotary inertia energy when said valve means is in said second state;
• means for interrupting voltage applied to said motor means and for simultaneously disengaging said clutch means to effect a dumping of pressure in successive cycles from said wheel brakes to said power cylinder assembly as said brake pressure back-drives said piston;
• means for reapplying said clutch means to effect a first rate of pressure buildup;
• means for monitoring back EMF voltage of said motor means following said dumping of pressure from said wheel brakes as pressure builds up at said first rate upon re-engagement of said clutch means and as said inertia energy is converted to a brake pressure increase, said monitoring means including means for detecting a predetermined voltage value that is a function of said memory voltage;
• and
• means for establishing, when said predetermined voltage value is detected, a modified rate of pressure buildup, slower than said first rate, at said wheel brakes by applying a voltage to said motor means to effect said modified rate of wheel brake pressure buildup, whereby brake cycle time is increased and vehicle stopping distance is reduced as effective wheel brake pressure levels are increased.