Robust Adaptive Control of Hydraulic System With Input Saturation and Valve Dead-Zone

In this paper, a first attempt is made to deal with the motion tracking problem for a hydraulic system in the existence of input saturation, unknown valve dead-zone, parametric uncertainties, and uncertain disturbances. To address the problem of input saturation and valve dead-zone simultaneously, the designed anti-windup is integrated with the compensation of the dead-zone nonlinearity effectively via a combined and comprehensive inverse model. A dynamic auxiliary system and a smooth dead-zone inverse model, which are utilized to attenuate input saturation and compensate the nonlinearity of dead-zone, are synthesized into the design of the robust adaptive controller based on the backstepping technology. Meanwhile, the adaptive law and the nonlinear robust control law are conducted to handle parametric uncertainties and various disturbances. Based on the Lyapunov stability theory, the closed-loop asymptotic stability of the designed control strategy is proved, and the boundedness of all the signals are ensured. The excellent performance of the proposed control scheme is verified by comparative experimental results.