Feedback nonlinear robust control for hydraulic system with disturbance compensation

In this article, a practical method named feedback nonlinear robust control with disturbance compensation is proposed for a hydraulic system with matched and mismatched generalized uncertainties (e.g. parameter derivations, external disturbances, modeled errors and/or unmodeled dynamics), in which a finite-time disturbance observer and a nonlinear robust controller are integrated together by backstepping method. The finite-time disturbance observer is used to estimate matched and mismatched generalized uncertainties. The design of the nonlinear robust controller is to make the closed-loop system stable. Not only the nonlinearities (e.g. nonlinear flow features of servo-valve) but also matched and mismatched generalized uncertainties are considered by the proposed controller. Furthermore, asymptotic output tracking performance after a time T-0 is theoretically ensured by the proposed controller. The high-performance nature of the proposed control strategy is verified by extensive comparative experimental results.