Electret vibration energy harvesters with symmetrically configured curved-beam hinges

For vibration energy harvesters, broadband power spectral characteristics are often desirable. One way of achieving broadband spectrum is to employ curved-beam hinges, utilizing their nonlinear spring characteristics. In our previous study, electret-based vibration energy harvesters employing curved-beam hinges were investigated via numerical analysis based on stochastic differential equations and colored-noise inputs. It showed that the harvesters with curved-beam hinges can produce higher power than the ones with ordinary straight beams when the external acceleration is between 0.02g and 0.05g. It was also learned that the straight-beam device, a Duffing oscillator, performs better than the curved-beam device, a Duffing-Holmes oscillator, at higher acceleration (>= 0.1g\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\ge 0.1g$$\end{document}). Since the energy harvesting efficiency is one of the most important performance indicators, continuous search for novel configurations with improved efficiency is needed. For that purpose, a symmetric configuration of curved-beam hinges (a Duffing oscillator) is proposed in this work, in contrast to the previously reported one with an asymmetric configuration (a Duffing-Holmes oscillator). This study shows, via numerical analysis, that the symmetric configuration can produce higher (up to 7.3% more) power outputs for the external acceleration magnitude higher than 0.1g, when compared to an asymmetric configuration. The study results also show that it can produce higher power outputs (up to 4.5 times) than the harvesters employing ordinary straight-beam hinges.