Patent ID: 7232192

Claim:
A system for braking the wheels of a hydraulic hybrid vehicle, comprising: a brake pedal having a range of pedal displacement including a deadband displacement range; an accumulator containing fluid at relatively high pressure; a reservoir containing fluid at lower pressure; a pump/motor having variable volumetric displacement connected to the accumulator and reservoir, and driveably connected to the wheels; a controller determining a desired vehicle deceleration on the basis of the pedal displacement, determining a vehicle deceleration due to current friction braking based on brake hydraulic pressure and brake pedal displacement, determining the vehicle deceleration due to engine braking and friction braking, determining a net vehicle deceleration from the desired vehicle deceleration, and the vehicle deceleration due to current friction braking and engine braking and multiplying the net vehicle deceleration by vehicle mass, determining a magnitude of braking force to decelerate the vehicle at the desired deceleration, determining a wheel torque corresponding to the required braking force, determining a net wheel torque to stop the vehicle at the desired deceleration, from a current vehicle speed, determining a torque magnitude to be applied to the pump/motor by the wheels based on the net wheel torque, determining the pump displacement corresponding to the magnitude of torque to be applied to the pump/motor by the wheels, and producing a command signal representing a magnitude of pump displacement corresponding to the torque magnitude to be applied by the wheels to the pump/motor; and a control valve for changing the volumetric displacement of the pump/motor in response to said command signal.