Dynamic characteristic research for piezo pneumatic intelligent valve positioner

In this paper, the model of piezo-valve type electric-pneumatic valve positioner is established based on the motion equation, the ideal air equation, the energy equation, and the Newton´s Second law. It takes into consideration the friction force in piston seals, the change of active volume due to the piston moving, leakage at the positioner, dynamics and flow nonlinearities through the positioner orifice, the difference between the entering process and exhausting process of each piezo-valve, and the difference between the charging process and discharging process. Experiment result provides an accurate description for dynamic process and characteristic of the positioner. The time response of regulation process can be determined based on these curves. It is very useful for control strategy investigation of positioner, in spite of that the control strategy is Pulse Width Modulation, Fuzzy Control, or Adapt Control. This approach can be applied to process control, automatic instrument, robotic, and auto.