Reducing the resonant frequency of the vibration energy harvester with a negative stiffness magnetic spring

Low frequency vibration is ubiquitous in our daily life and production, such as vehicle vibration.In order to effectively harvest low frequency vibration energy with vibration energy harvester (VEH) , a new method to reduce the resonant frequency of a VEH was proposed. The reduction of resonant frequency of the VEH is achieved through the arc folding beams structure and the negative stiffness magnetic spring. Furthemore, the arc folding beam structure and negative stiffness magnetic spring also result in a more uniform stress distribution of the folding beam and a greater ability to withstand excitation acceleration, which results in high reliability of the VEH. Then the VEH was fabricated and tested. The experimental results indicate that introducing a negative stiffness magnetic spring can effectively reduce the resonant frequency of the VEH and increase the power output of the vibration energy harvester. After introducing a negative stiffness magnetic spring, the resonance frequency of the VEH decreased from 37.6 Hz to 28.8 Hz, a decrease of 30.6%, and the power output of the VEH increased from 5.45 mW to 7.98 mW, an increase of 46.4%. Finally, a detailed analysis of the experimental results was performed in theory using the finite element method. Theoretical analysis and experimental results are basically consistent.