An active suspension employing an electrohydraulic pressure control system

An active suspension employing an electrohydraulic servosystem in which pressure control valves are applied for the first time has been developed. The suspension is controlled by a microprocessor and acceleration sensors. The authors describe the theoretical and experimental analyses that were conducted in developing this system, including the studies of the active control system, vehicle system dynamics, and transmission of vertical inputs from the road surface. This system features a skyhook damper which can reduce body vibration to less than one-half that of conventional suspensions at low frequencies by applying an active damping force to the body proportional to its absolute velocity. The hydraulic system has passive damping characteristics dependent on the frequencies of road inputs. Optimization of these characteristics results in a reduction of vibration caused by high-frequency road surface inputs. An active moment control function using lateral and longitudinal sensors which can reduce body pitching and rolling is provided