Sliding control of an electropneumatic actuator using an integral switching surface

This paper presents a synthesis of a nonlinear switching control of a rotational electropneumatic servodrive using a sliding mode approach. A nonlinear sliding mode control law is applied to the system under consideration. First, the model of the electropneumatic servodrive is developed. This model is nonlinear with respect to both the state variables and the control input. It is transformed to be linear with respect to a new control variable and a coordinate transformation is then related to make possible the implementation of the nonlinear discontinuous controller. Two sliding mode controllers are synthesized with and without an integral term in the switching surface. The sliding regimes are particularly pointed out and their stability analyzed to show that the integral discontinuous control provides best results especially for a steady-state error cancellation. Practical considerations are proposed for choosing the control parameters and finally, the experimental results are presented and discussed.