Abstract:Electrohydraulic positioning servo system is a complicated nonlinear control object, and usually suffers various modeling uncertainties, which make it more difficult of the high performance controllers design to meet the servo accuracy requirements. A supertwisting sliding mode control strategy with adaptive gains was designed for the electrohydraulic system with consideration of various modeling uncertainties. With using known information of the model, the feedforward control law based on the model was imported into the traditional supertwisting sliding mode control algorithm, so as to improve the accuracy of servo system. By utilizing the adaptive laws to update the control gains in realtime and without knowing the prior knowledge of the exact bounds of modeling uncertainties, the conservatism caused by the artificially selected control gains which are related to those bounds in traditional control algorithm was avoided. The global stability of the closedloop system was proved based on the Lyapunov stability theory. The system tracking error was guaranteed to converge to an arbitrary small neighborhood around zero in finite time, and the converging rate and the bound of the steady state tracking error could be adjusted by control parameters. Simulation results show that the proposed control strategy can effectively attenuate the adverse effect brought by the modeling uncertainties and apparently improve the tracking accuracy. In addition, the achieved control input is continuous, which is more suitable for application in practice.