Robust PPC-SMC for a Pneumatic Stage Considering Pressure Characteristics

Abstract

Pneumatic control systems possess severe nonlinearities resulting from the pressure and flow characteristics of compressed air as well as dynamic friction behavior. To facilitate their practical application, achieving high-speed and high-precision position control is indispensable. Therefore, to further enhance the tracking performance, this study proposes a novel control method that integrates the air pressure characteristic model from previous research with filtered factorization based on operator theory and prescribed performance control-sliding mode control (PPC-SMC). Specifically, by introducing new parameters into the model, independent parameter identification is enabled. Furthermore, a nominal model is utilized to improve the baseline tracking performance. In addition, the design of the PPC-SMC is extended to link with the reference trajectory, achieving further improvement in tracking performance. By integrating these methods, the proposed system can simultaneously account for cylinder friction, pressure characteristics, and sensor noise. In this study, a control system is designed based on a mathematical model that encompasses these nonlinear factors, and the control input is derived by defining a sliding surface for the PPC-SMC. Finally, experimental evaluations using an actual system confirm that the proposed method substantially reduces tracking errors and achieves superior tracking performance compared to conventional approaches.