Comparison of vibration energy harvesters with fixed and unfixed magnetic springs

Electromagnetic energy harvesting is an effective approach to absorb vibration energy and supply electrical power to small-scale electronic devices. Magnetic spring mechanism is usually utilised in energy harvesters due to its high reliability. The conventional magnetic spring consists of two fixed magnets on the two sides of a levitated magnet. To obtain better performance, this Letter proposes an electromagnetic energy harvester where the top magnet of the magnetic spring is unfixed in comparison with the fixed type. Prototypes with the two different configurations are fabricated and an experimental setup is developed to implement comparative investigation. The results show that the power generation capability and the frequency range of the energy harvester are significantly improved by using the unfixed magnetic spring.