Design and Implementation of a Reference Model-Based Disturbance Observer for Position Control of Electro-Hydraulic Servo Systems

Electro-hydraulic servo systems are often subject to parameter uncertainties and external disturbances, which degrade position tracking accuracy and control robustness. To address these challenges, this paper proposes a reference model-based disturbance observer (RMDO) control strategy. The state-space model of the system is first established, followed by the design of an ideal reference model. Based on this, a reference model controller is developed to enable the reference model output to track the desired input, while a disturbance observer is constructed to estimate real-time disturbances. A corresponding control law is then formulated to compensate for the estimated disturbances, ensuring that the system output accurately follows the reference model output and ultimately achieves precise tracking. Stability analysis of the closed-loop error system is performed using a Lyapunov-based approach within the input-to-state stability (ISS) framework, demonstrating that the tracking error remains bounded under bounded disturbance derivatives. Finally, simulation and experimental results verify the effectiveness and robustness of the proposed control strategy.