Design and numerical investigation of an ultra-wide bandwidth rolling magnet bistable electromagnetic harvester

To realize broadband energy harvesting at low-frequency excitation, this paper proposes a rolling magnet bistable electromagnetic harvester (RM-BEH) which utilizes the rolling motion of a magnetically levitated magnet. The dynamic model of the RM-BEH is established, based on which the output of the RM-BEH is predicted through electromagnetic induction combined with finite element analysis. By calculating the parameter region for monostable and bistable configurations, the broadband response characteristics of a bistable system with shallower potential wells are investigated. Results show that the RM-BEH could achieve interwell oscillation in the frequency range between 5.8 Hz and 22 Hz under sweep frequency excitation with a level of 0.5 g. Under constant frequency excitation, multiple vibrational patterns of the RM-BEH are presented and examined. To identify the multiple solutions, harmonic balance method results are presented, indicating that high-energy orbit oscillation can be achieved with appropriate initial conditions. Furthermore, the response of RM-BEH under Gaussian white noise and human motion excitations is considered and results indicate that the RM-BEH could travel across the potential wells easily to generate large output. In general, the broadband response characteristic under harmonic excitation and considerable output under human motion excitation demonstrate the excellent application foreground of the RM-BEH.