An ultra-low frequency ball-impacted potential-variable nonlinear energy harvester

Abstract

Efficient energy harvesting for ultra-low frequency vibrations remains a large challenge. An ultra-low frequency ball-impacted potential-variable nonlinear energy harvester (abbreviated as BPNEH) is proposed in this work to provide a new solution for the challenge. Upon excitation, a horizontal beam, which is magnetically coupled to a vertical one, vibrates back and forth with large amplitudes through ball-impacts, along with a variable potential energy due to the vibration of the coupled vertical one. A prototype of the proposed BPNEH is fabricated to demonstrate the effective contribution of both the ball-impact and the variable potential energy under an ultra-low frequency excitation. Compared to a conventional potential-variable nonlinear energy harvester (abbreviated as PNEH), the RMS voltage of the proposed BPNEH is increased by 78.4 % in 1–8 Hz, along with a sub-peak that appears to the left side of the main peak. This new finding of a double peak phenomenon is further observed and clarified by a theoretical model, where the output voltage of the proposed BPNEH is increased by 209.6 % in 1–10 Hz. In addition, the main factors affecting the sub-peak in the observed double peak phenomenon are also considered and discussed with respect to harvesting more energy. The proposed BPNEH along with the double peak phenomenon is believed to be applicable to ultra-low frequency scenes, especially with large amplitudes, of engineering fields such as wearable devices, structural health monitoring systems, etc.