Disturbance observer based robust motion control for single rod hydraulic actuators

A novel robust motion control method based on disturbance observer was presented.In order to achieve high performance control specifications for single rod hydraulic positioning servo systems using proportional valves.The disturbance observer was included in the proposed closed loop motion controller,which is used to estimate various external force disturbances and the changing of hydraulic parameters,and thus compensation was introduced to enhance the servo systems' motion performance and robust stability.In order to compensate for the dead zone nonlinearities of the proportional valve,a novel compensation term using the nominal model's output information was proposed,which was capable of avoiding the spool's frequently switching effectively and meanwhile have no impact on the servo system's dynamic performance.Computer simulations are developed for the excavator's hydraulic systems,and the results show that the proposed design have strong robustness to parameter uncertainty and external disturbance,and that applying the new dead area compensation term can obviously improve servo system's output smoothness.