Design And Research Of A Type Of Magnetically Coupled Piezoelectric Vibration Energy Harvester

The piezoelectric vibration energy harvester is a device that converts vibration energy into electrical energy to power low-power microelectronic equipment.Because of its advantages of high-power generation efficiency,low cost and environmental protection,it can replace chemical batteries in low-power electronic devices,therefore has broad application prospects in wireless sensor networks and portable electronic devices.In this thesis,we design a multi-degree-of-freedom magnetically coupled piezoelectric vibration energy harvester based on the nonlinear widening band method to address the problems of linear single-degree-of-freedom piezoelectric vibration energy harvester with narrow acquisition band and single direction,and low conversion efficiency in low-frequency,wide-band and multi-directional vibration environments,its performance is analyzed.The main contents are as follows:（1）Based on the piezoelectric vibration theory,Euler-Bernoulli beam theory and magnetic dipole model assumptions,a nonlinear electromechanical coupling model of a two-degree-of-freedom magnetically coupled piezoelectric vibration energy harvester is established,the effects of its total potential energy,magnet spacing and end mass on the output performance of the system are investigated.With a suitable magnet spacing,the structure behaves as a bistable state,and the acquisition band and output voltage of the system are significantly increased,the band width is extended by a factor of four compared with the linear structure.The results show that the nonlinear magnetism can effectively extend the acquisition band and increase the output voltage.（2）The magnetically coupled single/bidirectional vibration energy harvester is designed,its distributed parameter electromechanical coupling model is established,the influence law of each beam potential energy,magnet spacing,end mass,deflection angle,excitation amplitude and other parameters on the output voltage and frequency band width is studied,and the system dynamics of the single/bidirectional vibration energy harvester is analyzed.The results show that under the suitable magnet spacing d₂,the two short beams behave as bistable and the two long beams behave as tristable,the tristable potential barrier height is lower than that of bistable,which can collect energy in a lower excitation environment;under the specific external excitation,decreasing the end mass ratio and increasing the declination angle can extend the bandwidth;The interaction of magnetic force can stimulate the collector to prod uce chaotic motion response and make the piezoelectric vibrator cross the potential well frequently,thus improving the energy collection efficiency of the system.The bidirectional piezoelectric vibration energy collector designed in this paper can also produce vibration and output voltage under the interaction of magnetic force when only one side is excited by vibration.（3）Based on the analysis of the vibration characteristics of the railway wagon body and the electricity demand of on-board safety monitoring electronic equipment,an orthogonal structure energy harvester is designed and its structure parameters are optimized based on the actual working conditions.Finally,the power supply performance of the harvester system is analyzed using the LTC3588-1 power management circuit.The research results show that the system can output 3.6V voltage stably,the output power can reach 13mW,which meets the power demand of this low-power safety monitoring unit.