Extended-state-observer-based output feedback control for hydraulic systems with performance constraint.

This paper proposes an adaptive output feedback prescribed performance controller based on the extended state observer (ESO) for hydraulic systems with unmodeled dynamics. Considering the constraint on tracking errors, we have defined an improved convergence time-controllable prescribed performance function. It achieves the predetermined performance of the error signal for the original system by stabilizing the transformed system. In other words, the tracking error will remain within the specified constraint bounds over time. Unlike most existing prescribed performance control methods, this approach combines the advantages of finite-time performance functions and is derived from a modified transformation function related to tracking error and an asymmetric barrier function. It not only removes the constraints associated with initial error conditions, guaranteeing globally superior control performance but also offers flexibility in handling general cases of symmetric or asymmetric output constraints. Furthermore, an ESO is designed to estimate the unmeasured states and unknown dynamics through the output position signal, which avoids contamination of the velocity and acceleration signals by measurement noise and effectively mitigates the influence of most unfavorable factors on control performance. Building upon this foundation, we have developed a low-complexity control approach that integrates performance constraints with the ESO using filter-based backstepping techniques. Ultimately, the stability of the closed-loop system is substantiated using the Lyapunov method, and the effectiveness of the developed approach is validated through simulation. [ABSTRACT FROM AUTHOR]