Design And Study Of MEMS-based Low Frequency Piezoelectric Energy Harvester

The piezoelectric energy harvester,which is based on Micro-Electro-Mechanical System(MEMS),not only has a simple structure,small size,high conversion efficiency but also easy to achieve integration and miniaturization.So it's expected to replace the traditional battery provide power to Microelectronic devices,but the device still have some problems such as low output power and effective working band narrower.Based on the researches of many scholars,this thesis chooses and utilizes the positive piezoelectric effect of Pb-based Zirconate Titanates(PZT)materials,and uses the cantilever beam structure,to analysis the low frequency piezoelectric energy harvester which is based on MEMS technology.It is of great significance and value to analyze the research and realize the conversion of the mechanical energy to the electric energy in the low frequency environment.Firstly,based on the status of the domestic and international research,the piezoelectric effect of the piezoelectric materials,the piezoelectric mode and the electromechanical coupling model and the equivalent circuit model of the whole device have been analyzed in theoretically.The results shows that the structural parameters and material parameters can affect the output performance of the device,and a theoretical basis has been provided for further designed of new-type energy harvester.Secondly,combined with the classical rectangular cantilever beam structure and vibration theories,a new type of bifurcated three-degree-of-freedom piezoelectric energy harvester is designed by increasing the degree of freedom of the cantilever beam.The relationship between the relevant parameters and the harvest performance is analyzed.On this basis,the overall structure of the device is optimized,the resonant frequency of the piezoelectric energy harvester is reduced to 292.11Hz,the maximum output voltage can achieve 1.062V under an acceleration of 1G at 292.11Hz of frequency,the output power can be up to 0.155mW under the load of 0.4M?,and the power density is up to 496.79?W/mm~3.But there still have some problems such as the effective operating frequency band is narrow and the output voltage and power are low when the excitation is disturbed.Then,considering the situation that the excitation in the environment may be disturbed in a wide frequency range or the vibration environment at the single frequency point,the effective working frequency band of the device is analysis,the character that the resonant frequency of the cantilever with different length is different is used,and a wide-band hollow three-degree-of-freedom piezoelectric energy harvester is designed.By optimizing the structure of the device,the effective operating frequency band between third resonant frequency of the device is 23Hz,the maximum power of one cantilever is 40.5?W and the power density is 123.47?W/mm~3under the resonant frequency of 177.09Hz and 1.7M?load.Compared with the broadband piezoelectric energy harvester in recent years,the effective working frequency band of the device is wider while the similar output performance is achieved.Finally,thisthesisdiscussesthebifurcationtypeandthehollow three-degree-of-freedom piezoelectric energy harvester from the view of process.Through the analysis and simulation of the preparation process and the key process of the device,the feasibility of the two piezoelectric energy harvester is proved,and the basis for the physical preparation has been provided.