Research On Piezoeiectric Pilot Pneumatic Valve Position Proportional Control System

Endoscopy is now one of the essential medical examination equipment.The field of view,the observation angle and the direction of endoscopic lens can be adjusted through the mirror system.Due to the simple control,fast response and intrinsically safe,without additional measures to be taken,such as explosion-proof,pneumatic control valve is widely used in industrial process control.With high sensitivity,good stability,easy to implement switching or proportional regulation,and easy to achieve pressure feedback,intrinsically safe and high positioning accuracy,piezoelectric valve is widely used in pneumatic adjustment process.The position proportional control system of pneumatic pilot pneumatic valve is researched and applied to medical endoscopic mirror system.The piezoelectric effect of the piezoelectric bending plate is adopted in the multilayered piezoelectric actuator.Multilayered piezoelectric actuator is commonly used as a piezoelectric pilot valve,whose driving ability is greater than the ordinary dual-chip.With the development of the technology,it is desirable that the multilayered piezoelectric actuator meet the requirement of low voltage driving and high reliability.In order to meet the new requirements of multilayered piezoelectric actuators,this paper designs a new low-voltage multilayered piezoelectric actuator and adds a self-deformation detection unit based on the traditional multilayered piezoelectric ceramics.The principle and performance of the piezoelectric actuator including the designed low-voltage multilayered piezoelectric actuator and the piezoelectric bimorph driver are analyzed in detail,and then the structure and the optimization of the piezoelectric pilot nozzle baffle valve are analyzed.On this basis,the control system of piezoelectric proportional valve and its hardware drive circuit are designed.The closed-loop control of pressure feedback is used to realize the proportional change of air pressure with the control signal.The valve is connected with the cylinder,and the position proportional control system based on the piezoelectric pneumatic valve is constructed,and the closed-loop control system is formed by the displacement sensor feedback to realize the proportional change of the cylinder displacement with the displacement setting signal.The system uses double closed-loop control mode,proposed an effective control model and control algorithm.The data acquisition card gathers the set value displacement signal and the feedback displacement signal of the cylinder in the Simulink Real_time module,then the PID parameter is adjusted and control signal is output in real-time.This output signal is taken as the control signal of the piezoelectricity electrical proportion valve.The experiment system of pneumatic pilot pneumatic valve position proportional control system is built and then the system is tested.The system displacement error is reduced by displacement closed loop control and hysteresis inverse compensation,which improves the control effect of the system.The results show that the control method can reduce the displacement error to a certain extent,the maximum displacement error is 0.31 cm,and the displacement error of the positive and negative stroke of the cylinder is different,so it is necessary to correct the displacement calibration.