A new robust sliding mode controller for a hydraulic actuator

We present the design of a robust sliding mode controller for the force control of a hydraulic actuator in presence of significant system nonlinearities and uncertainties. Our control strategy is based on sliding mode control. The design of a switching surface is based on Lyapunov techniques, and a variable structure control law is designed using the theory of sliding mode control. For the control we use a nonlinear mathematical model of a hydraulic system interacting with the environment. We try and consider most of the nonlinear and uncertain dynamics of this system in order to achieve robust performance over a range of operating conditions. The simulation results show that the proposed sliding mode controller is not sensitive to a large variation of parameters such as flow gain, supply pressure or environmental stiffness, and has an excellent tracking performance for various set point forces under uncertainties.