Extended-State-Observer Based Second Order Sliding Mode Control for Electro-Hydraulic System with Desired Compensation

A super-twisting algorithm (STA) based output feedback nonlinear controller is developed for the precision position tracking control of the electro-hydraulic system (EHS) in this paper. First, a nonlinear extended state observer (ESO) is designed to simultaneously estimate the unmeasured states and the lumped disturbance based on extended model of the EHS. The designed nonlinear ESO is finite time stable according to the homogeneity theory. Then the STA is employed to make the position tracking error as small as possible based on the estimated signals provided by the nonlinear ESO. Moreover, to further reduce the influence of the estimate errors, the desired compensation technology is employed. The proposed controller theoretically guarantees finite time tracking performance in the presence of various uncertainties and disturbances in the sense of Lyapunov theory, which is very important for the output tracking control of EHS. Extensive comparative simulation results are obtained to verify the tracking performance of the proposed control strategy.