Design And Optimization Of Electromagnetic Vibration Energy Harvester And Application In Wireless Sensor Network

With the continuous development of the Internet of Things,the number of deployments of the global IOT terminal devices continues to increase.For tens of thousands of terminal equipment,how to solve the problem of energy supply has attracted more and more attention.Among many renewable energy sources,vibration energy is ubiquitous and not restricted by the environment.Thus,vibration energy can be converted into electrical energy through vibration energy harvester to supply long term power to various terminal devices.Compared with piezoelectric,capacitive（electrostatic）and magnetostrictive vibration energy harvesters,electromagnetic vibration energy harvesters are simple in structure,do not require external power supplies,and can be used in various harsh environments.However,electromagnetic vibration energy harvesting technology still has many challenges:1.The power density of the harvester is limited by the size of the permanent magnet and the coil;2.When not working at the resonance frequency,the output voltage of the harvester drops rapidly;3.Need to design a power management circuit for the harvester to converter AC voltage to DC voltage with energy storage and voltage regulation.In response to the above challenges,this research conducted in this work are as followings:（1）Based on literature review,a nonlinear electromagnetic vibration energy harvester has been developed for low frequency vibration energy harvesting.The harvester uses a magnetic spring with a resonant frequency of 6.3Hz;（2）Propose a set of modeling scheme by deploying ANSYS Maxwell simulation and MATLAB calculation.A time domain model has been developed for the electromagnetic vibration harvester,and has been applied to evaluate the harvester’s performance.This scheme can help optimize the harvester and save the optimization cycle.Compared with the actual output of the generator,the modeling error is less than 9%;（3）Use the proposed modeling methodology to study the impact of the size and number of magnets in the suspension block,the thickness of ferromagnetic disc,the size and the position of the coil on the output characteristics of the harvester.When the acceleration amplitude is 2.2m/s²,the vibration frequency is 9.9Hz and the load is 330Ohm,the peak-to-peak output voltage of the optimized triple-magnet harvester is 19.1%higher than that of the double magnet harvester,and the normalized power density can reach 12665μWcm^-3g^-2;（4）According to the output characteristics of the optimized energy harvester,combined with the power required by the wireless sensor node,a complete power management solution has been developed.The power management circuit consists of four blocks,a full-bridge rectifier,a DC-DC voltage stabilizing circuit,a multi-stage energy storage circuit,and an energy storage management unit.The associated software and hardware design of Zig Bee node have been completed using CC2530 microcomputer along with RSSI to realize the wireless ranging measurement.Combining the power management circuit,wireless node and the energy harvester,a self-powered wireless module has been demonstrated for ranging measurement.This module can be used for fleet monitoring,coal miner positioning,cattle and herd monitoring and positioning,etc.