A Study On Vibration Energy Harvesting Based On Mechanical-Electrical Coupling Material

Micro electro mechanical systems are developing rapidly as a new cross subject in recent years. Because of its mobility, self-controllable, integration and other characteristics, the energy device of Micro electro mechanical systems is also developed as small as possible. There are many disadvantages of conventional chemical batteries, such as the large volume, heavy weight, short service life for power supply, environmental pollution and so on. It is replaced by miniature solar batteries, fuel cell batteries, micro chemical batteries, wind turbines, solar generator, and thermal energy generator gradually. But these micro energy devices are restricted by lifetime limitation or working conditions, so it will bring a lot of inconvenience in application.Researchers have turned to the micro energy based on the electromechanical coupling material In recent years, for this kind of energy device does not need any additional sensors or converters, not have limitation in the design of structure size, and also can meet the different electricity needs of Micro electro mechanical systems. There are many papers about the research of vibration energy harvesting based on the electromechanical coupling materials, and this technology is becoming mature. The research and application of this technology is the mainly based on the piezoelectric materials rather than ferroelectric material. Ferroelectric material is a new type of electromechanical coupling intelligent material. It not only inherits the advantages and characteristics of the piezoelectric material, but also its electromechanical coupling characteristic is more obvious for the presence of spontaneous polarization. The research of secant modulus of ferroelectric has been increasingly improved, which provides favorable conditions for the research for the energy capture of ferroelectric material.This paper mainly does research on the hysterics character as a result of the polarization reversal phenomenon and on the differential constitutive equations of ferroelectric materials, based on the cognition of piezoelectric materials; Then, do analysis on the electromechanical coupling behavior of the piezoelectric cantilever beam, study the factors which influence the ability of generating power, and optimize its structure according to the analysis results; Next. do experiment to test vibration behavior of piezoelectric cantilever beam, compare the resonance frequency with the theoretical analysis results to verify the accuracy of experimental rig; Last, do vibration energy harvesting experiment on the ferroelectric materials and piezoelectric materials respectively, compare voltages generated in different excitation of the two kinds of materials, and Analysis the generating capacity of voltage.Chapter one:This chapter mainly introduced the background of this research, and described the needs of micro energy development. Introduce capture energy research based on electromechanical coupling vibration materials in and out of the world. Elaborated the research and development of electromechanical coupling material and secant modulus of ferroelectric, cited several differential models decrypting ferroelectric hysteretic characteristics. Described the advantages and disadvantages of these models, finally proposed the research content and research method of this paper.Chapter two:The front half part introduced the piezoelectric material and piezoelectrical effect, elaborated four kinds of piezoelectric equations and the piezoelectric coefficient transformation under different boundary conditions, Introduced the secondary piezoelectric effect and its calculation. The second part introduced the ferroelectric materials and ferroelectric effect; especially introduced the polarization reversal including90°domain and180°domain switching,which arouse hysteretic phenomenon, elaborated a new ferroelectric constitutive model based on the phenomenological Landau free energy theory, and successfully simulated ferroelectric hysteretic phenomenon and the double hysteretic phenomenon by this model.Chapter three:Introduced the coupled-modes, forms of structure, connecting method of piezoelectric energy harvesting, compared the advantages and disadvantages of these methods and accounted for choosing the cantilever beam as the type to capture energy. Analysis the electromechanical coupling behavior of the piezoelectric cantilever beam by using the ANSYS finite element software, analysis factors that impact the piezoelectric cantilever beam to capture energy. At last, performed the modal analysis and analysis the impaction of the mass to the resonant frequency of the piezoelectric cantilever beam.Chapter four:Designed and built the vibration test rig, optimized the size and structure of piezoelectric cantilever beam using the piezoelectric coupling analysis results in chapter three. Tested the resonance frequency of piezoelectric cantilever and contrasted it to the calculating result of resonance frequency by using ANSYS software to verify the reliability of the structure and the test rig. Compared the power generation behavior of piezoelectric cantilever beam and ferroelectric cantilever beam by inputting different excitation and analyze the two experimental results, and gave out the evaluation.