Comparison of sliding mode control with state feedback and PID control applied to a proportional solenoid valve

A novel nonlinear sliding mode controller has recently been developed for direct acting proportional solenoid valves. This paper presents a comparison between the valve performance using this controller, and that obtained using two alternative control strategies; state feedback and PID control. Each controller is described in turn, and experimental step response results are presented to demonstrate the validity of each strategy. These results are compared on the basis of response time, overshoot, and steady-state error. The time taken to design each controller, and the required level of knowledge of the valve dynamics, are also assessed. The ability of each controller to reject flow reaction forces is evaluated by observing the changes in the step response when oil is passed through the valve. The results demonstrate that the sliding mode controller results in a faster, more robust closed-loop response. In addition, only minimal knowledge of the valve dynamics is required in order to design the controller.