Design of an adaptive backstepping controller for active suspension systems

Abstract

This thesis presents a method to design an adaptive controller for active suspen sion systems which cancel the effect of the unknown road disturbance in presence of parametric uncertainty. In this thesis, three different cases is investigated which are a seat, a quarter and a half vehicle models. The full state feedback is chosen for the seat and the quarter vehicle model since all states are available for measurement. In the half vehicle model, partial states are available for feedback. Therefore, state derivative feedback is employed. In addition, the dynamics of the actuator model is considered in the quarter and half car models. It is assumed that the applied force on the system depends on the current of the actuator. Since, the aim of the controller is to isolate the body from road disturbance, an adaptive controller is designed to regulate the current of the actuator. The controller design is based on the following steps; the parametrization of the sinusoidal disturbance where the amplitude, the phase and the frequency is considered as unknown. Then an adaptive controller is designed to cancel the effect of the dis turbance where the mass of the body and the parameters of suspension is considered as unknown. The backstepping procedure is employed due to the unmatched situation between the road disturbance and the actuator input. The stability of the controller is guaranteed with using the proposed lyapunov function. A simulation is shown to reveal the performance of the designed controller.