Enhanced Broadband Performance of Magnetically Coupled 2-DOF Bistable Energy Harvester with Secondary Intrawell Resonances

This study investigates possible routes to high-energy orbit motion (HEOM) from which high electrical power can be generated in a magnetically coupled bistable energy harvester (MCBEH) with two degrees of freedom (DOFs). By examining the frequency responses of the 2-DOF MCBEH, four main routes to HEOM are found to originate from two primary and two secondary intrawell resonances. For conventional BEHs (CBEHs), only primary resonance has been considered important in the design process, because secondary resonances can hardly initiate HEOM. However, for the 2-DOF MCBEH, it is observed that the secondary resonances also form the separate frequency bands of the HEOM for energy harvesting. Furthermore, with the increase of the excitation intensity, the secondary resonances tend to bridge the gap between the frequency bands for the two primary resonances, significantly enhancing the operating frequency bandwidth (up to 200% with respect to the CBEH used in this study). The enhanced broadband performance of the 2-DOF MCBEH is theoretically and experimentally evaluated and discussed in comparison with the CBEH.