Robust control of a vehicle active suspension system using sliding mode observer

In this paper, an 8-DOF vehicle model including driver seat dynamics, subjected to random road disturbances is introduced in order to investigate the advantages of active over conventional passive suspension system. Force actuators are mounted parallel to the body suspensions and the driver seat suspension. State feedback control approach is taken in the active suspension system. Due to practical limitations, not all states of the system required for the state-feedback control are measurable, and thus must be estimated with an observer. To estimate the system unavailable states, Luenberger and sliding mode observer are used. With the states estimated from mentioned observers, state feedback control will be applied on the suspension system. The simulation results indicate that in the presence of external disturbances and model uncertainties, a sliding mode observer-based controller has better performance than the Luenberger observer-based adjusting system. This indicates that the sliding mode observer is robust observer against disturbances and system uncertainties.