A novel two degree of freedom single magnet bistable energy harvester based on internal resonance

Up to now, many nonlinear techniques such as bistable structure have been used to harvest vibration energy from the environment to achieve a wide response bandwidth. However, most bistable harvesters require two opposing magnets to form the potential energy function, which limits the miniaturization of the harvesters. In this paper, a two-degree-of-freedom U-shaped single magnet bistable energy harvester (SMBEH) based on the internal resonance technique is proposed. The harvester consists of a U-shaped beam, a magnet and a tip mass. The governing equations of the system are derived and the output performance of the harvester is obtained through numerical simulation and experiments which are in good agreement. The proposed SMBEH can achieve low frequency energy harvesting by utilizing a 1:2 internal resonance. When the excitation amplitude is equal to 0.4 g, the SMBEH can produce a significant output in two frequency ranges from 7 Hz to 7.7 Hz and 11.7 Hz to 15.73 Hz, which broaden the output frequency band. In the end, the output performance of SMBEH at different resistances and the charging performance were verified, respectively.