Position control for hydraulic systems with incomplete differential backstepping sliding mode control

Further improvement in the control accuracy of the hydraulic servo system is hampered by its position control structure and non-structural uncertainty. For structural uncertainties, nonlinear adaptive control can be applied to achieve asymptotic tracking performance. While unstructured uncertainties, such as nonlinear frictions, always exist in hydraulic systems and reduce the tracking accuracy. In this paper, an incomplete differential backstepping sliding mode control (IDBSMC) controller is proposed to realize the position control of hydraulic servo systems based on friction compensation. The controller combines backstepping design with sliding mode control. The problem of structured uncertainties of hydraulic servo system is solved by using the invariance of control system parameters and external disturbances in the sliding state and the problem of unstructured uncertainty is solved by friction compensation. The incomplete differential is introduced to weaken the differential effect of the controller, reduce the interference caused by pure differential mutation signal, and the filtering effect caused by incomplete differential can suppress the chattering of the sliding mode control. This paper, the high precision asymptotic tracking performance of the system is proved by theory and experiment in the presence of various uncertainties.