Robust output feedback control of electro-hydraulic system

This paper presents output feedback second order sliding mode control to achieve robust finite time position control for Electro-Hydraulic Servo System (EHSS). The system is subjected to inherent uncertainties, parametric perturbations and disturbances. A nonlinear dynamics of EHSS is represented by linear uncertain dynamics for the sake of control design. A relative degree one sliding surface is proposed. It is shown that super twisting controller using this relative degree one sliding surface attains finite time positioning. Further disturbance estimation is used to augment the control for getting desired performance with less control effort. The method is validated in simulation and experiment both. The performance of the proposed controller is compared with the super twisting controller devised using non singular terminal sliding surface which also yields finite time positioning.