Robust control scheme for electrohydraulic servo systems using extended sliding mode observer

This paper addresses the robust control scheme for electrohydraulic servo systems (EHSS) with system uncertainties by utilizing a novel extended sliding mode observer (ESMO). The state-space model of the EHSS is derived by considering system uncertainties. The ESMO with only the displacement feedback signal is employed to estimate both the system full-state and the unmodelled system uncertainties. What’s more, with estimation values from the ESMO, a robust control scheme (RCS) is addressed in detail for the EHSS by employing the multiple-surface sliding control (MSSC) architecture. In addition, three proper boundary layers are properly employed to suppress the chattering phenomenon in the control input so that the controller can achieve a smooth sliding manifold. Subsequently, a proper Lyapunov function is defined to prove the stability of the closed-loop. Comparative simulation and experimental results prove the efficiency of the proposed control methodology.