Research on Disturbance Control of Electro-Hydraulic Servo Systems Based on Fractional-Order Sliding Mode Control

To improve the disturbance rejection performance of valve-controlled cylinder electro-hydraulic servo systems under external disturbances and load variations, this paper proposes a fractional-order sliding mode control (FOSMC) strategy. A system model with dual-inertia compensation is established, and a fractional-order sliding surface with the corresponding control law is designed to improve convergence and reduce chattering compared with conventional sliding mode control. Unlike conventional SMC, the proposed method combines fractional-order sliding surface design with dual-inertia-compensated modeling to enhance tracking robustness. A physical test bench is constructed, and both simulations and experiments are conducted under different disturbance and load conditions. In representative cases, FOSMC reduced the Root-Mean-Square Error (RMSE) under white-noise disturbance by 14.3% and lowered the maximum tracking error in experiments by 72.9% compared with PID. The results verify the effectiveness of the proposed method in improving tracking accuracy, disturbance rejection, and robustness.