Command-Filter-Based Velocity-Free Tracking Control of an Electrohydraulic System with Adaptive Disturbance Compensation

Achieving high-precision tracking control in electrohydraulic servo systems remains challenging due to internal uncertainties, external disturbances, and inaccessible state variables. To address these issues, a command-filter-based velocity-free tracking controller is proposed for an electrohydraulic system. A cascaded adaptive extended state observer is designed to simultaneously compensate for both matched and mismatched disturbances and estimate the unmeasurable velocity state. A first-order command filter is incorporated into the traditional backstepping framework to prevent “differential explosion”. Lyapunov analysis proves that the controller guarantees the boundedness of tracking errors, observer estimation errors, and all closed-loop signals. Comparative simulations demonstrate the superior performance of the proposed controller.