Low-bandwidth Semi-active Damping for Suspension Control

Active damping has been shown to offer increased suspension performance in terms of vehicle isolaton, suspension packaging, and road-tire contact force. It can even approximate the performance of full state feedback control without requiring the difficult measurement of tire deflection. Many semi-active damping strategies have been introduced to approximate the response of active damping with the modulation of passive damping parameters. These strategies have typically required a relatevely high bandwidth for actuator response. This paper investigates the simulation performance and "frequency response" of two concepts in low-bandwidth semi-active suspension control. The first strategy controls the pressure drop in a hydraulic flow path, the second controls a hydraulic resistance. The bandwidth of these actuators is approximately an order of magnitude less than other semi-active devices. A quarter-car model is studied with the controlled damping replacing both passive and active damping of typical control schemes. Both low-bandwidth damping strategies perform remarkably well compared to both active and high-bandwidth, semi-active damping.