Optimization Of The Piezoelectric Excitation Ball Valve And Flow Control

The traditional electric proportional valve is generally driven by the electromagnetic actuator, with the slow response rate, low control precision and the narrow working bandwidth, this traditional valve is already cannot satisfy some new demands of the automation control system, especially in the occasion which requires high-speed response. Although the powerful high-speed solenoid actuator can improve the response rate a little, because of the electromagnetic force, installation space and the inertia effect, further improvement of the response rate of the electromagnetic actuator will become more difficult. In view of the insufficiency of the traditional electric proportional valve, it is very necessary to design a new flow control valve driven by piezoelectric actuator combining with the pneumatic throttle valve organically.Based on the original pre-tightening limited digital piezoelectric ball valve, on the basis of analyzing its shortcomings, designs more perfect new experimental controlling and driving system and related mechanical structure are designed, and the dynamic mechanical model and the flow resonant characteristics of the new valve are analyzed both in theory and in experiment, and then some flow proportional control study is researched at last.First, a set of more perfect experimental controlling and driving system is designed to satisfy the demands of fast, high frequency response, efficiently control and so on. High frequency signal generator is adopted instead of computer to control the PZT driving power, reducing the signal delay, and realizing the high frequency range (1-10kHz) continuously adjusting test. Then high power PI PZT driving power is used replacing the original HPV PZT driving power to improve the performance of the piezoelectric valve. In the high frequency area, the ball valve will realize big flow output about 43L/min, and the deadline pressure will reach 0.5MPa above. Anyhow, this new system plays a remarkable role in the piezoelectric crystal drive performance improvement, and it will lay a firm foundation for the subsequent high-frequency continuously adjusting experiment study.Second, while the performance index of the piezoelectric ball valve has reached the industrial using standard, some relevant structural and function designs of optimization are implemented in this thesis, such as:The one is the realization of the function of working in arbitrary position, making it more adapted to the various complex industrial production environment. The second is the redesign of the flow pipeline, to solve the leakage problems of the valve, and reduce the leakage from originally quite dozens of liters per minute to 0.1 L/min below effectively.Third, based on the experimental research of the dynamic performance of the ball and the flow output of the valve, analyzing the relationship between the flow output and the drive frequency, it is found that when the drive frequency reach around 6000Hz, the throwing height of the ball and the flow output will get fiercely increase and reach a maximum. And then the dynamics model of the piezoelectric ball valve is established in this thesis, and then theoretical analyses the dynamic process of high frequency throwing ball is also researched to analyses the resonant characteristics generating mechanism of the piezoelectric valve.Finally, some flow control research on the basis of PWM control method is studied in this thesis after the flow characteristics of the piezoelectric valve is very clear. The flow output is controlled both in open-loop and closed-loop control method, achieving certain steady precision about 1 L/min below. The feasibility of the PWM control methods applying in the flow control of this new piezoelectric valve is verified in this thesis, and theoretical and experimental basis is provided for the subsequent higher precision control method and control algorithm study.All in all, this piezoelectric ball valve is not only simple and small, but also has realized the fast and big flow output target. And that a certain steady-state control accuracy is achieved and the feasibility of the proportion flow control of the new type of piezoelectric ball valve is also verified...