| In the past decade,vibration energy harvesting technology has received more and more attention,and the energy supply demand of low power electronic components is an impetus to promote the development of this research field.The advantage of vibration energy harvesting technology is that it can not only save external power,reduce maintenance cost due to periodic replacement of batteries,but also reduce chemical waste caused by traditional batteries.The basic mechanisms of vibration-to-electric energy conversion includes electromagnetic,electrostatic and piezoelectric.When compared with the electrostatic,the energy harvesting devices based on piezoelectric and electromagnetic principles obtain higher energy capture efficiency and simpler structure,thus they receives more attention.The paper reviews the research status of piezoelectric vibration energy recovery device.For the problem of single resonant frequency and limited working bandwidth as well as low energy harvesting efficiency in low frequency environment of the existing micro piezoelectric energy harvesting device,a novel magnetic frequency-modulated hybrid piezoelectric electromagnetic energy harvesting device is designed and put forward,and the device is studied from three aspects of numerical calculation,simulation analysis and experimental research.Firstly,a magnetic frequency-modulated hybrid piezoelectric electromagnetic energy harvesting device is designed according to the performance requirement,and the threedimensional model of the device is established.In order to broaden the frequency band of the hybrid piezoelectric electromagnetic energy harvesting device,the nonlinear magnetic force is introduced into the device to modulate resonant frequency,thus the electromechanical coupling mathematical model of magnetic frequency-modulated hybrid piezoelectric electromagnetic energy harvester is establised.Secondly,the electromechanical coupling model of the magnetic frequency-modulated hybrid piezoelectric electromagnetic energy harvesting device is solved,and the output power frequency response curve is obtained.Results show the magnetic frequency modulation can broaden the power generation frequency band of the system.The output characteristics of the energy harvesting device are discussed from the aspects of natural frequency ratio,mechanical damping ratio and other structural parameters respectively,and the theoretical value of the optimal load is obtained.Then,the finite element simulation software ANSYS workbench and Ansoft Maxwell is used to analyze the magnetic frequency-modulated hybrid piezoelectric electromagnetic energy harvesting device.By using the method of sequential coupling,harmonic response analysis and transient response analysis of piezoelectric part and electromagnetic part are carried out respectively,and the power frequency response curves of the piezoelectric and electromagnetic power generation part before and after the coupling are obtained.The simulation results show that the output of the hybrid piezoelectric electromagnetic energy harvesting device is not a single superposition of the output from the piezoelectric and electromagnetism power generation part,and there is a coupling between the two parts,which is consistent with the theoretical model.At the same time,the influence of structural parameters such as the center distance of the magnet on power generation performance is also simulated,which is consistent with the numerical calculation results.Subsequently,the experimental scheme of the research on the power generation performance of the hybrid piezoelectric electromagnetic energy harvesting device is determined,and the experimental platform is established.Power generation characteristics from the aspects of the structure with and without frequency modulation effect,single piezoelectric and electromagnetic energy harvesting as well as complete magnetic frequencymodulated hybrid piezoelectric electromagnetic energy harvesting structure are studied and the influence of structural parameters on the device are discussed.The results show that when the magnet center distance are determined form 36-46 mm,the bandwidth of the novel magnetic frequency-modulated hybrid piezoelectric electromagnetic energy harvesting device is broadened by 4Hz when compared to the energy harvesting device without the magnetic frequency-modulated under part under an acceleration of 0.2g.The results show that the magnetic frequency-modulated part can achieve the goal of broadening working bandwidth and lowing the resonant zone.In addition,magnetic frequency-modulated hybrid piezoelectric electromagnetic energy harvesting device improves energy harvesting efficiency by solveing the problem of single generation frequency.Based on theoretical modeling,simulation analysis and experiments,this paper proposes and studies a wideband,high efficiency and environment adaptable magnetic frequencymodulated hybrid piezoelectric electromagnetic energy harvesting device,which provides a theoretical reference for the vibration energy collection of small electronic components. |
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