Output feedback disturbance rejection control for full-state constrained hydraulic systems with guaranteed tracking performance

In this paper, a practical output feedback disturbance rejection controller holding the desired dynamic behavior is proposed for precise movement control of hydraulic systems with disturbances, unknown states, and severe measurement noise. To relieve the noise and deal with unknown states, the estimated values obtained by the state observer are used to replace the actual states. Considering the matched and mismatched disturbances in hydraulic systems, the state observer and disturbance observer are combined to obtain their estimations. A prescribed performance function constraining tracking performance and the barrier Lyapunov function maintaining the desired dynamics are synthesized to guarantee the tracking error and all state errors within desired boundaries. Then, an integrated output feedback disturbance rejection controller is constructed through backstepping design to stabilize the closed-loop system. Finally, abundant comparative experimental results validate the tracking performance of the proposed controller.