Structural Design And Key Technology Study On Multi-Chamber Series Piezoelectric Pump

As a kind of new fluid pump developed in recent years, piezoelectric pump has broadapplication prospects in a fluid system.The output performances of piezoelectric pumpdepend not only on features of inlet and outlet of check valve，but also chamber structureclosely related.Combining with the national natural science fund project " Reserch onmechanism and key technology of active valve piezoelectric pump "(project number:50575093) and fostering fund project of institutions of higher learning engineering supportedministry of education-"Research on drive test control functional integration for new typepiezoelectric institutions "(project number:708028), we adopt piezoelectric bimorph todrive piezoelectric pump work, construct multi-chamber series piezoelectric pump withwheel flat valves，carry on theory design and experimental research for multi-chamber seriespiezoelectric pump1、Domestic and foreign research situation and development of piezoelectric pumpAlthough research history of piezoelectric pump is more than30years only, it hasbecome one of research topics of many countries scholars, which has advantages of simplestructure， high efficient conversion， reliable performance， and not affected byelectromagnetic interference. On the basis of related literatures at home and abroad，variousclassification methods of piezoelectric pump are summarized in this paper. Moreover，research status of valve piezoelectric pump and no valve piezoelectric pump are reviewed athome and abroad. And that pressure pump products have been widely used in aerospace,chemical analysis, biological engineering and other fields.Because output pressure and flow ofsingle-chamber piezoelectric pump is limited，multi-chamber series piezoelectric pump becomes a goodsolution. But that is still at the beginning stages in the domestic and overseas，hence research results areless. So it is necessary to research operating characteristics of multi-chamber series piezoelectric pump and improve output capacity of multi-chamber series piezoelectric pumps, which can establish researchfoundation towards practicalization and productization.2、Piezoelectric vibrator characteristic researchPiezoelectric vibrator is powe component of piezoelectric pump，whose performance directly affectsthe output capacity of piezoelectric pump. Based on thin plate deformation theory，curve equation ofcircular piezoelectric vibrator deformation is established and analytical expression of deformation andvolume variation si deduced.We select bimorph piezoelectric vibrator that its base diameter is35mm andceramic diameter is29mm，and so calculate its theoretical deformation.Finite element model ofpiezoelectric vibrator is established by ANSYS software.Subsequently some of the vibration modesfrequencies are obtained by modal analysis，and the amount of demoration is analyzed.Through staticcharacteristics tests of piezoelectric vibrator，we verify the validity of theoretical analysis and finiteelement simulation results.3、Design of passive check valve of piezoelectric pumpOne-way check valve is a key part to output performance of valve piezoelectric pump，its researchand development of valve piezoelectric pump is accompanied by one-way valve development. Becauseoutput pressure is relatively high to multi-chamber series piezoelectric pump, we adopt wheel flat valveby eryllium bronze that thickness is about5-7μm in order to improve bearing and reverse blockingcapacity.Deformation and flow capacity is analyzed under static load by theory，and its geometry size ofwheel flat valve is determined. In addition，we turn to study the effect on flow capactity between bothsides of flow capactity pressure difference. It can provide theoretical basis for improving output flow afteranalyzing dynamic response characters.4、Performance analysis and test for multi-chamber series piezoelectric pumpMulti-chamber series piezoelectric pump can be thought of as serial working mode with many single–chamber piezoelectric pump，which has a larger output flow and pressure. Because the output ofmulti-chamber series piezoelectric pump is fluctuating，it is difficult to establish accurate mathematicalmodel to calculate output performance.Therefore, prototype machines such as double-chamber，three-chamber and four-chamber series structure are designed using multiple piezoelectric bimorph，andtheir working performances also analyze further. Moreover output pressure, output flow, valveinstallation position and different drive mode are also tested.From the view point of output pressure，experimental results show that output pressure ofthree-chamber series piezoelectric pump is about1.5times than that of double-chamber in the workingfrequency，whose output pressure is more stable，but four-chamber output pressure mostly fluctuates.However with the series increases，output pressure also increases.From the view point of output flowrate，with chamber number increases，output flow is also increased at high frequencies(greater than 200Hz). When the working frequency of output voltage is300Hz，output flow of four-chamber seriespiezoelectric pump reached nearly1000ml/min. Obviously，multi-chamber series piezoelectric pump caneffectively improve output flow performance5、Design of drive power supply for Multi-chamber series piezoelectric pumpTo meet requirements of quick response for piezoelectric vibrator, we use FPGA and DDStechnology to design drive power supply that has quickly response. DDS is a kind of frequent synthesistechnology newly， which proceeds to frequent syntheis by phase concept and has high resolution.FPGA chip is the core of the hardware circuit. IP cores of drive supplys power are embedded in internalFPGA chip by VHDL language. We design DDS peripheral circuit and software flow by modularity.Experimental results show that output waves (sine wave, triangular wave and square wave) have highprecision and quick response speed, when parameters such as frequency and waveform changes that canmeet stability requirements.6、Design of closed-loop control systemfor multi-chamber series piezoelectric pumpPiezoelectric pump is vulnerable to bubbles，impurities interference，so sometimes output flow is notstable.Therefore we design closed-loop control system for multi-chamber series piezoelectric pumpincluding buffer circuit，modulation circuit，power amplifier circuit and step-up transformer，whose corecomponent is variable gain modulation circuit contrrolled by digital potentiometer.After actual outputflow converted to avoltage value， is compared with reference voltage value. If deviation exists，digitalpotentiometer tap position is regulated by FPGA chip. It is goode method sto adjust gain of modulationcircuit in order o realize flow stability control，which provide new thinkings for future research andexperiment platform.