Enhanced reduced-order extended state observers-based position tracking error constraint control of a pump-controlled hydraulic system via multiparameter singular perturbation theory

Abstract

In this paper, the position tracking error constraint control is investigated for a pump-controlled hydraulic system (PHS) subject to an unmeasurable velocity signal and disturbances. A barrier Lyapunov function (BLF)-based backstepping controller is designed, and a set of enhanced reduced-order extended state observers (RESOs) is proposed to estimate the velocity and disturbances. Dynamic surface control (DSC) is used to avoid a repeated calculation of the derivatives of virtual control inputs. Multiparameter singular perturbation theory is utilized to clarify the working mechanism of the enhanced RESOs and the closed-loop system stability properties. Theoretical analysis results reveal that the closed-loop system is uniformly ultimately bounded and the position tracking error is always constrained within a prescribed bound by a proper selection of the perturbation parameters. Moreover, the final position tracking error can be arbitrarily small by further tuning these parameters. In addition, the enhanced RESOs are proven capable of improving the convergence performance of the closed-loop system. Experiments are conducted on an actual PHS to validate the superiority of the proposed control strategy.