Research On The Pneumatic Control Valve Driven By Ultrasonic Motor

Ultrasonic motor(USM) has been widely used in the high-precision micro drivers occasions because of its simple structure, easy miniaturization, high positioning accuracy, and no electromagnetic interference. In this paper, the ultrasonic motor was used as the pilot driver pneumatic proportional pressure valve, in order to increase the accuracy and stability of electric pressure valve. It is a exploration in the field of piezoelectric technology's application in pneumatic direction.A test system of USM was built, the speed characteristics of USM was tested, and the position servo control characteristics was analyzed. Experimental results show that in the rated load capacity (22N) or less, ultrasonic motor with 10-nanometer positioning accuracy, and high speed rigidity. On this basis, the ultrasonic motor servo control model for the ultrasonic motor was proposed, which provides a foundation for the USM'application in the pneumatic pressure valve.The program of USM driven pneumatic pressure valve was proposed. The valve has a two-stage structure with nozzle flapper valve as the pilot valve, while the displacement of the flapper is controlled by a linear USM. Analysis on the static characteristics of nozzle flapper valve showed that nozzle diameter and inlet of nozzle flapper valve area is the main factors of the impact of the sensitivity.The mathematical model of the USM driven pneumatic pressure valve was established. The transfer function of output pressure versus input flapper displacement was derived, which shows that the valve is a complex fourth-order system. Then the flow gain and flow pressure coefficient expression was derived. Simulation on the valve's nonlinear model was taken, and drive performance characteristics'impact on the valve is analysised.A USM driven pneumatic pressure valve prototype was tested, including its open-loop input-output experiments, the steady-state and dynamic characteristics of closed-loop experiments. Results show that under the 0.3MPa working pressure, the valve's linearity is±0.5%, resolution 0.1%, hysteresis±0.5%, the dynamic response time of about 2s approximately. Because of USM's continuous displacement output capability, this pneumatic proportional pressure valve does not exist problems affecting the valve's stability such as drift and zero-drift.