Method and apparatus for controlling an active suspension system

Abstract

An apparatus for controlling a vehicle active suspension system having a plurality of actuatable hydraulic motors, each corner having a motor connecting the sprung mass with its associated unsprung mass. Each motor has an associated spool valve for connecting either of two expandable fluid chambers of said motor to a pump or reservoir. Each corner has an associated force sensor for sensing the force value between its associated unsprung mass and the sprung mass. An analog, closed force loop control circuit provides a valve control signal having a value functionally related to the difference between a sensed force value and a desired force value for a selected corner. The closed loop control circuit includes a variable gain amplifier for controlling the value of the valve control signal as a function of the frequency of variations in the difference between the sensed force value and the desired force value on the selected corner. The amplifier gain is controlled as a function of hub velocity so as to undamp a selected corner and as a function of chassis velocity so as to damp the chassis. A digital processing circuit determines a displacement error value for selected corner. The displacement error value is summed with the valve drive signal. An actuator bump stop arrangement is also provided.