Gas flow tracking for electronic pressure control system in gas chromatography under state constraints and...

In gas chromatography (GC) analysis, the gas flow control performance of the Electronic Pressure Control (EPC) system that is responsible for signal analysis and processing, critically determines the reliability and accuracy of analytical results. However, during the gas flow control, unknown hysteresis characteristics, voltage saturation, and state constraints significantly impact control performance. This study addresses the fuzzy adaptive practically finite-time output feedback and signal processing problem for the EPC system in GC, incorporating system state constraints and unknown hysteresis characteristics. First, a modified Prandtl-Ishlinskii model is employed to accurately describe the valve's unknown asymmetric hysteresis. A dynamic model reflecting the actual system, incorporating gas resistance characteristics, is then established. Second, a fuzzy state observer based on a fuzzy logic system (FLS) is designed to estimate unmeasurable system states. Third, considering state constraints and potential computational complexity, a fuzzy adaptive practically finite-time controller is proposed. This controller, built upon the observer, integrates backstepping, dynamic surface control (DSC), and barrier Lyapunov functions (BLF), utilizing filters for smooth processing of virtual signals. System stability is then proven via Lyapunov theory. Finally, experimental verification is performed using both step and dynamic gas flow targets with a newly constructed EPC system. The results demonstrate that the proposed controller achieves precise and stable tracking control of gas flow, even in the presence of unknown hysteresis, state constraints, and voltage saturation.