Robust position tracking for a hydraulic servo system

This paper deals with the robust asymptotic position tracking of a hydraulic servo system. The nonlinear model involves uncertain parameters due to linearization of the servo valve and variations of the initial volume of the cylinder. The problem is solved using the Internal Model Principle appropriately modified with a Hurwitz invariability technique and a Simulated Annealing Algorithm. The problem is proven to be always solvable and the controller parameters are chosen to provide a suboptimal solution for tracking error minimization. Simulation results are presented for the nonlinear model of the actuator and for a specific reference signal and all the expected range of model physical uncertainties.