A Sliding Mode Variable Structure Control Approach for a Pneumatic Force Servo System

A sliding mode control (SMC) approach was used in a pneumatic force control servo-system with uncertainties and external disturbances in this paper. To reach exact force control in pneumatic force servo-system, the E/P pressure proportional valve was used as an electro-pneumatic converter in constructing an electro-pneumatic force control servo system. The dynamic model of the pneumatic force servo system was built firstly, and then a boundary layer approach was used to the design of controller, in which using a saturation function to substitute for the sign function based on Lyapunov theory. Finally, the performance of the controller was simulated and tested. The results show that the system performance has been much improved when compared with a conventional PID controller, and it has a good control precision and robustness