Design and realization of a sliding mode control scheme for a pneumatic cylinder X-Y axles position servo system

Due to the pneumatic air provided a large effective power, the pneumatic system are adopted in many automation industries. However, the pneumatic air is compressible, and pneumatic system has many nonlinear characteristics, such as the mass flow rate parameters variable and the servo valve dead zone problems. In this paper, a sliding mode control for a pneumatic cylinder position servo control system was proposed to realize position regulating and tracking control. The key feature of this control scheme is the using of extra adjustable free parameters to the design of sliding surface and switching variable boundary layer for the pneumatic servo system to improve the control performances. The validity of the proposed control scheme is verified through practical testing on an experimental pneumatic cylinder X-Y axle servo system device. In the cases of step, multi-steps, and sinusoidal level position command inputs, the test results show that the proposed control scheme is capable of improving the tracking precision.