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Adaptive Sliding Mode Control of a Nonlinear Electro-hydraulic Servo System for Position Tracking

In view of the electro-hydraulic position servo system with parameter uncertainty and bounded disturbances, an improved adaptive sliding mode control scheme is proposed. The mathematical model of the valve-controlled system is first constructed with consideration of the external disturbance, matched and mismatched unknown parameters. Then, the parametric adaptive estimation laws are established by Lyapunov technique to estimate the generalized uncertainty parameters, and the discontinuous projection algorithm is used to ensure the boundedness of parameter estimation. In order to eliminate the chattering phenomenon in sliding mode control, the saturation function is designed to replace the sign function and the gain coefficient is adjustable on the sliding surface. Finally, the comparative experimental results clarify that the proposed control scheme has better control performance than the PID controller and the SMC controller.