Load resistance optimization of magnetically coupled two-degree-of-freedom bistable energy harvesters considering third-harmonic distortion in forced oscillation

Abstract

This thesis proposes a new technique for optimizing load resistances of vibration-based energy harvesters considering third-harmonic distortion in response. It is observed that for a magnetically coupled two-degree-of-freedom bistable energy harvester, the second beam has the third-order sinusoidal component in interwell motion due to mechanical nonlinearity. Because impedance matching, the most well-known technique for designing load resistances, assumes the system is linear, a new method considering this third-harmonic distortion is conceived to overcome the inherent limitation of the matched resistances. As a result, especially at the highest excitation frequency within the range of interwell motion, which is 17.5 Hz, the root-mean-square power of the second beam is improved by 1.6 times compared to the matched output. Moreover, it is identified that optimizing resistances at 17.5 Hz is a well-informed decision for enhanced broadband performance. Although only the third-harmonic distortion is considered in this study, the optimization process has a promising potential to be utilized whenever any higher-order harmonics emerge in nonlinear energy harvesters.