Modeling and performance evaluation of a bi-stable electromagnetic energy harvester with tri-magnet levitation structure

A novel tri-magnet levitation bi-stable electromagnetic energy harvester (BEEH) is proposed in this work. The bi-stable nonlinear mechanism is realized by using the single-sided bipolarity of the ring magnet. To balance the asymmetric bi-stable potential wells caused by the self-weight of the levitating magnet, how the potential energy varies when the size of the top magnet changes is investigated. The results show that enhancing the attraction of the top magnet can balance the self-weight of the levitating magnet. Furthermore, for the structure with determined magnet dimensions, the spacing and depth of the two potential wells can be adjusted by changing the spacing of the two ring magnets. In experiments, the output performance of the device with different ring magnet spacing is investigated to confirm that this device has a tunable operating bandwidth and that a wider bandwidth requires the partial sacrifice of output power. The results show that the present device exhibits a frequency bandwidth of 6.25-9.5 Hz and generates a peak power of 6.02 mW under 9.5 Hz and 0.5 g, implying the esti-mated normalized power density of about 891W/(m3g2). A performance comparison between the proposed BEEH and other multi-stable magnetic levitating harvesters proves that the former is more suitable for microdevices.

Automated summary

A novel tri-magnet levitation bi-stable electromagnetic energy harvester is proposed, using a single-sided bipolar ring magnet to realize the bi-stable nonlinear mechanism. The potential energy variation is investigated to balance the asymmetric potential wells caused by the self-weight of the levitating magnet. Experimental results show that the device has a tunable operating bandwidth and a wider bandwidth requires sacrificing output power.