Iterative approximation control of hydraulic press

In this paper, a sliding mode controller is designed for a hydraulic press based on iterative approximation method. The nonlinear model of the hydraulic press is approached by a sequence of iterative linear time-varying systems, thus the control problem of the nonlinear system could be solved through these linear systems. Then a series of sliding controllers are designed for the sequence of linear time-varying approximations, these controllers will converge to a effective sliding mode controller of the original nonlinear system. Simulation results show that precise speed tracking could be achieved through this method. And when the bulk modulus and the reaction force change, the controller is robust.