Abstract: This paper proposes a novel magnet-coupled variable-potential-well bi-stable flutter energy harvester to enhance energy harvesting performance in low air speed regions. The bi-stable configuration under the action of the external magnetic field is designed and the variable-potential-well technique realized using the nonlinear magnetic force and the motion of external magnet with elastic support. The energy harvesting performance is enhanced and its mechanism revealed. The governing equation of the magnet-coupled flutter energy harvester is established. The bi-stable configuration is theoretically analyzed according to the nonlinear magnetic dipole model and the stability theory. The dynamic responses of the energy harvester are numerically simulated. The results show that the bi-stable configuration transforms the supercritical flutter behavior of the non-magnet-coupled system into subcritical flutter one. Therefore, the cut-in air speed of the limit cycle oscillation can be reduced by more than 50%, significantly broadening the effective air speed range for energy harvesting. The influence of the magnet separation distance and magnetic dipole moment on the flutter energy harvesting performance is investigated. Based on the variable-potential-well technique, the separation distance and the corresponding potential well are adaptively adjusted, enabling easier undertaking of the inter-well vibration by the system. Therefore, the beneficial enhancements of the air speed range and output power are simultaneously realized, providing a new design approach for energy harvesting application in low speed air flow.

Key words: aeroelasticity, piezoelectric energy harvesting, bi-stable, potential well, nonlinear