Robust Tracking for Time-Varying Uncertain Systems with Application to 4WS Vehicles

The problem of asymptotic robust output command tracking is studied for the case of time-varying systems with nonlinear uncertain structure. The problem is solved using a compensator with time varying state feedback, static state feedback, unity output feedback and integral action. The controller is restricted to be independent from the uncertainties. The output of the closed loop system tracks polynomial type reference signals. Sufficient conditions for the problem to have a solution are established. The result of asymptotic robust output command tracking is applied to four wheel steering (4WS) time varying vehicle model. An analytic algorithm for the computation of the vehicle tracking controller is presented. The effectiveness of the controller is illustrated through simulation.