Design And Study Of A Multi-stable Vibration Energy Harvester Based On Permanent Magnets

With the rapid development of Internet of Things technology and artificial intelligence technology,the market demand for wireless sensors is increasing.At present,the mainstream power supply method of wireless sensors is to use chemical batteries,which have the disadvantage of limited capacity and need to be replaced or recharged regularly.For this reason,this paper proposes two electromagnetic vibration energy harvesters for continuous power supply to wireless sensors,one of which is a multi-stable vibration energy harvester based on a square permanent magnet structure,and the other is a bistable vibration energy harvester with a toroidal coaxial permanent magnet structure.The main contents of this paper are.(1)The magnetic force models of the square permanent magnet structure and the toroidal coaxial permanent magnet structure were established,and the potential energy curves of the multi-stable vibration energy harvester based on the square permanent magnet structure and the bistable vibration energy harvester based on the toroidal coaxial permanent magnet structure were obtained by polynomial fitting,and the electromechanical coupling dynamics models of the two energy harvesters were derived.(2)The influence law of the permanent magnet structure parameters on the potential energy curve of the multi-stable vibration energy harvester based on the square permanent magnet structure is studied,and a set of structural parameters of the vibration energy harvester(bistable system)with bistable potential energy curve and a set of structural parameters of the vibration energy harvester(tri-stable system)with tri-stable potential energy curve are proposed based on the influence law.The influence law of excitation frequency and excitation acceleration amplitude on the dynamic response of the bistable system and the tri-stable system is analyzed by numerical methods.The results show that the number of steady states of the potential energy curve can be adjusted by adjusting the height and spacing of the lateral permanent magnets h.Meanwhile,the tri-stable system has a wider operating bandwidth than the bistable system,and the tri-stable system can achieve large periodic motion between traps at lower excitation acceleration amplitude.(3)The effects of the ring air gap and the ring height difference on the potential energy profile of the bistable energy harvester with a ring-shaped coaxial permanent magnet structure are investigated.The effects of excitation frequency,excitation acceleration amplitude,ring air gap and ring height difference on the dynamic response of the system are analyzed by numerical simulation under harmonic excitation,and the dynamic response of the system under narrowband random excitation is also studied.The results show that when the system is bistable,reducing the ring height difference is beneficial for the bistable energy harvester to capture the vibration energy under weak excitation,while increasing the ring air gap can expand the operating bandwidth of the bistable energy harvester;increasing the random excitation intensity under narrow-band random excitation can make the system change from monostable to bistable motion.(4)An experimental prototype of a bistable vibration energy harvester with a toroidal coaxial permanent magnet structure is built,and the corresponding data acquisition software is developed based on LabVIEW.The experimental results show that the simulation results match with the experimental results,and the proposed bistable energy harvester can effectively expand the operating bandwidth of the system and improve the acquisition performance.