Research On Impact-based Electromagnetic Vibration Energy Harvesters

Micro energy harvester converting ambient energy into electric energy has the advantages of small size,long life,maintenance-free and non-pollution.As a battery replacement,it has broad application prospects in wireless sensor networks and implantable micro-systems.Therefore,it is of great significance to study impact-based electromagnetic vibration energy harvester for low frequency,wideband and weak features of environmental vibration.Based on the electromagnetic vibration energy harvester developed by our research group in the early stage,we optimized the structure of the harvester and improved the power density and long-term stability.Finally,the developed electromagnetic vibration energy harvester successfully driven a wireless sensor node for medium and long distance communication.In addition,to apply some scenarios of higher requirements about volume,an explored impact-based micro-electromagnetic vibration energy harvester is designed,fabricated and measured.The main work is as follows:(1)Based on the existing electromagnetic vibration energy harvester of the group,this paper proposed a technical scheme adding mild steel on the outside of the magnet to improve the output performance of the harvester.Then,ANSYS and MATLAB software are used to analyze the influence of mild steel and array on the output performance of the harvester.Finally,the optimization of the applied electromagnetic vibration energy harvester was completed.In addition,to apply some scenarios of higher requirements about volume,a structure of an impact-based micro-electromagnetic vibration energy harvester is presented.(2)The design of the applied and micro electromagnetic vibration energy harvester is completed by using SolidWorks software.By modifying the fixing method of the spring,the stability of the applied electromagnetic vibration energy harvester is improved.Finally,the prototypes of the two harvesters are fabricated.(3)Two prototypes are measured.The experimental results show the maximum power density of the prototype of the applied harvester is 304?W/cm~3,which is 18.7%higher than that of the previous device developed under base excitation with the amplitude of 0.3 g at 8.3 Hz.The result verifies the effectiveness of the proposed scheme adding mild steel for increasing the output performance.The power bandwidth is 15.7%or 1.3 Hz.Under base excitation with the amplitude of 1 g at 14 Hz,output power and power density of the micro-electromagnetic harvester are 2.5?W and 6.3?W/cm~3 respectively,which is equivalent to the performance of the MEMS electromagnetic vibration energy harvester reported in the literature.(4)A medium and long-range wireless temperature and humidity sensor node is designed based on the applied harvester.Under the base excitation with the amplitude of0.3 g at 8.3 Hz,the time is 22.1 s for completing data acquisition,transmission and reception,and the communication distance is approximately 210 m.