Robust Optimized Sliding Mode Tracking Control of an Electrohydraulic Actuator System under Internal Leakage Flow Variation

In modern industrial applications, the advantages of an electrohydraulic actuator (EHA) system include a high power-to-load ratio, a precise trajectory with a rapid motion, and the ability to create a substantial amount of torque. Nevertheless, owing to its exceptionally high nonlinearity, the EHA system is difficult to control, especially in terms of position tracking. This work thus provides a robust optimized sliding mode controller (SMC) for effective tracking control. Utilizing the constant rate reaching law and Lyapunov stability theorem, the proposed controller achieves closed-loop stability. In addition, by substituting the signum function with hyperbolic tangent function, the chattering in the SMC controller was significantly decreased, and particle swarm optimization (PSO) was used to minimize the total absolute errors in order to achieve the variable design. The mean square error (MSE) and robustness index (RI) evaluations suggest that the proposed controller is, in fact, rather robust to internal leakage.