A nonlinear multi-stable electromagnetic energy harvester with segmented moving magnet configuration

Magnetic-levitation-based energy harvesters can exhibit both strong softening and hardening nonlinearities, enabling an extended operational bandwidth. By introducing stationary magnets at center positions and tailoring the poling directions, bistable or tristable potential profiles can be systematically realized. These multi-stable configurations facilitate large-amplitude oscillations, thereby enhancing the voltage output generated via electromechanical transduction. However, previous studies have considered each magnetic interaction configuration separately, without analyzing or comparing their energy harvesting performance based on critical system parameters, such as identifying the specific excitation conditions under which each configuration performs optimally. Furthermore, the dynamic behavior in many of these studies is assessed solely through voltage measurements, without direct quantification of oscillation amplitude. In this study, we investigate how the restoring forces induced by attractive and repulsive magnetic interactions influence the system dynamics. Theoretical analysis is conducted to characterize the restoring force behavior associated with each configuration. Finite element method (FEM) simulations are performed to model the restoring forces, and the theoretical predictions are validated through static loading experiments. Electromagnetic prototypes implementing both repulsive and attractive configurations are fabricated and experimentally tested. The results demonstrate distinct multi-stable characteristics. Specifically, under identical conditions in which all system parameters are fixed except for the poling direction of a moving sub-magnet, the repulsive configuration is more effective for energy harvesting at low acceleration levels (less than 1 g), while the attractive configuration performs better at higher acceleration levels (greater than 1 g).