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

Abstract

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 estimated 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.