Accurate pressure control of a pneumatic actuator with a novel pulse width modulation-sliding mode controller using a fast switching On/Off valve

Pressure control of a pneumatic actuator using fast switching On/Off valves continues to remain a major challenge for researchers. This article proposes a novel pulse width modulation–sliding mode controller that improves pressure tracking of pneumatic actuators. First, a comprehensive mathematical model of the pneumatic system was developed that consists of several submodels. The model comprises pressure and temperature equations describing the thermodynamic process inside the pneumatic chamber, an orifice flow model for the On/Off valve, and a model for the dynamic response of the On/Off valve to the control signal. Second, computer simulations were carried out using the model, and then, experimental tests were performed to verify the simulation results. The comparison between simulation and experimental results demonstrates good accuracy of the presented model. Since the governing equations of pneumatic systems are highly nonlinear in terms of parametric (including discharge coefficients of the valve) and structural uncertainties (the lack of knowledge about the exact type of the thermodynamic process), a robust controller was designed for such a system. In this study, a novel pulse width modulation–sliding mode controller is proposed that demonstrates a significant improvement in pressure control of pneumatic actuators compared to other proposed controllers from the literature.