Design of coupled disturbance observers for nonlinear half-car active suspension system

The design of a disturbance observer (DOB) for a nonlinear half-car hydraulic active suspension system is presented. The system is controlled by the flatness-based controller (FBC) which is capable to provide efficient control under deterministic road disturbances and model uncertainties. The main objective is to design the mutually coupled general-proportional-integral (GPI) disturbance observers which estimate the disturbances in on-line mode during the car driving. It is assumed that the nonlinear effects, parameter variations, road profiles and possibly input unmodeled dynamics are lumped into an unknown time-varying and stochastic disturbance input signal. The quality and effectiveness of the proposed GPI-based DOB are shown by simulation results.