METHOD AND SYSTEM FOR CONTROLLING BRAKE PRESSURE UNDER LOW MU BRAKING SURFACE CONDITIONS IN A VEHICULAR ABS

摘要

Method and system for reducing the brakepressure rise rate under low Mu braking surfaceconditions by utilizing a vehicle reference speed and afixed bleed rate to determine if the wheels are beingover-braked. When over-braking occurs, the pressurerise rate is restricted by not allowing an ABS valve(10) to go into an Apply state (approximately 100psi/sec.), regardless of wheel acceleration levels. ARamp state is used in place of the Apply state and thepressure rise is therefore limited to approximately 30psi/sec. to improve wheel control. The Ramp duty cycleis also modified to provide the smallest pressure stepspossible with the current valve hardware.