Mathematical Modeling Of Electronic Electro-Pneumatic Inverter With Membrane And Its Structural Optimization

In process control system, popular automatic mechanism is controlled by current signal which can be processed easily during transmission, and executed by pneumatic signal which is safely in nature at present. Electro-Pneumatic Inverter is designed specially to convert the current signal to pneumatic signal to provide precise proportional control of valves, actuators and other pneumatical devices. Electronic and intelligent Electro-Pneumatic Inverter is taking the place of traditional mechanical inverter based on the development of the micro-electronic technology, the control theory and the computer science. Required by Technology Committee of Anshan City and Thermal Instrument Group of Anshan City, the subject is founded on 1997 and it has been researched as the subject of National Creative Foundation of National Science and Technology Department for Chinese enterprise with small and medium scale(00C26222121163). Basing on the research of Electro-Pneumatic Inverter in designing and manufacturing both in China and in international, the author establishes an uncouple model for the inverter and make some further research about structural design and optimization for it. At the same time an electronic electro-pneumatic inverter with membrane is worked out according to the model and related theory. The main work is described as follows:The thesis has established the design theory and system solution for electronic electro-pneumatic inverter with membrane after analyzed the issues of traditional mechanism. And the integration of gas/magnetic circuit and modularization of the inverter are introduced in practice also.Three Deformation/Deflection math models for circular flat diaphragm are set up based on classical theory of elastic thin plate, Von Karman's theory of large deflection and membrane theory. According to the three models and experimental results, the optimized model is established which is the basic element of transition model.Considering the couple fields, the transition process is disassembled into magnetic character and air circuit character by single-physical unit input. After analyzed the flexibility payload of flat diaphragm, it has set up an uncouple model for electro-pneumatic inverter to disassemble interactions into the action of pneumatic field, electromagnetic field and elastic field, which are worked together on inverter. The magnetic field and gas filed transition models have been verified by experiments. All these supply the theoryfoundation for getting precise and optimized design parameters.The paper sets up the architecture and technologic procedure for elastic element. At present the flat diaphragm is easy to be out of action and difficult to be debugged. The author analyzes the reason of the invalidation, finds the golden parameters for the upper and lower space of the flat diaphragm, and has make a plenty of experiments related with the temperature and the fatigue. And now the results are used effectively as guideline in design, at the same time it can supply more reliable inverter.Structural design and optimization of gas and magnetic circuit for inverter is achieved. It has been validated by experiments. The result of inverter performance test and practical instance is all right.The result and related model of the research have been used for the design of new generation Membrane Electro-Pneumatic Inverter (M-EPI97 Series), which has gotten the acceptance from National Creative Foundation of National Science and Technology Department for Chinese enterprise in Nov 2003.