An electronic controller for adaptive suspension

Developing an adaptive suspension system for a luxury car weighing over 2000 kg presents an exacting challenge in embedded control. This article describes the development of an adaptive suspension controller by Lamerholm Fleming Ltd for Rolls-Royce Motor Cars Ltd. during the period from 1995 to 1997. The controller replaced an earlier design, which had originally entered production in 1989. The new system uses hydraulic dampers (shock absorbers) which can be switched between three different settings by means of two solenoid controlled valves. Each damper setting provides a different complex force/velocity response for bounce and rebound. These mechanical characteristics are determined by the precise magnitudes of springs and orifices within the damper. The function of the electronic controller is to select the optimum damper setting for any particular driving conditions and to choose the best time to switch from one setting to another. The aim of the whole suspension system is to provide the best possible compromise between ride, comfort and handling.