Unknown dynamic estimator based control for hydraulic servo systems

Abstract

This paper investigates precise tracking control for a class of high-order hydraulic servo systems. For modeling of servo systems, the unknown nonlinearities of the hydraulic actuator and valve that may decrease the tracking performance and system stability are taken into account and then addressed via an unknown dynamic estimator with a simple structure and fewer tuning parameters. A recursive control design procedure is developed to achieve precise position tracking, where the calculations of the derivatives of the virtual control laws in traditional backstepping are remedied. The suggested controller guarantees that both the estimation error and tracking error will converge to a small set around zero. Simulation results are provided to verify the effectiveness of the proposed control strategy.