Patent ID: 7165818

Claim:
A vehicle attitude control system of an automotive vehicle comprising: a hydraulic pump and motor assembly comprising at least one hydraulic pump and a motor driving the pump; a hydraulic actuator that regulates fluid pressures in wheel-brake cylinders of road wheels of the vehicle, independently of each other; and a control unit being configured to be electronically connected to at least the motor and the hydraulic actuator, for executing vehicle attitude control by controlling a discharge pressure of the motor-driven pump and by controlling the fluid pressures in the wheel-brake cylinders to respective desired fluid pressures independently of each other; the control unit comprising a processor programmed to: determine a duty ratio of a drive signal of the motor, based on the desired fluid pressure of at least one of the wheel-brake cylinders; calculate duty ratios, needed for motor drive control, based on the respective desired fluid pressures of the wheel-brake cylinders of the road wheels; select a highest duty ratio of the duty ratios as the duty ratio of the drive signal of the motor; calculate a road-surface friction factor dependent duty-ratio maximum value based on a road-surface friction factor (μ); and execute a road-surface μ dependent duty-ratio limiter processing for limiting an upper limit value of the duty ratio of the drive signal of the motor to the road-surface μ dependent duty-ratio maximum value, wherein the road-surface μ dependent duty-ratio limiter processing comprises a select-low process by which a lower duty ratio of the selected highest duty ratio and the road-surface μ dependent duty-ratio maximum value is selected as the duty ratio of the drive signal of the motor.