科研之友
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摘要
Pneumatic control valves in practice are usually composed of three signal conversion processes that are associated with significant nonlinearities and dynamics. However, several physical, semi-physical, and data-driven models in the literature describe only one signal conversion process from the actuator force to the valve stem position. In this paper, a semi-physical model is proposed based on the physical principles of the three signal conversion processes. The proposed model contains two new components, namely, a backlash nonlinearity in the electric-pneumatic conversion process and an input-direction-dependent dynamics in the pneumatic-force conversion process. In addition, an updated model for the force-position conversion process is shown to be overdamped, instead of being the underdamped one in the literature. Experimental studies are provided to support the proposed semi-physical model and demonstrate the discrepancies of representatives of existing physical, semi-physical and data-driven models with experimental observations.
