Design and analysis of a stopper-engaged two-degrees-of-freedom nonlinear piezoelectric energy harvester

Abstract

In this paper, a stopper-engaged two-degrees-of-freedom nonlinear piezoelectric energy harvester is proposed. The proposed design consists of a cutout outer main beam and an auxiliary inner beam to achieve two close resonant frequencies. Impact-based nonlinearity is introduced to the system by adding a stopper to the end of each beam to broaden the harvesting bandwidth. By making the first two resonant frequencies close enough and introducing the nonlinearity, a broad bandwidth which connects the first two resonant frequencies can be achieved. Consequently, it is more adaptive to frequency variant environment than a conventional design. The governing equations of the electromechanical coupling system are derived based on the Euler-Bernoulli beam theory and piezoelectric constitutive equations. The mechanical stopper is modeled as a piecewise linear system. Finally, the voltage responses of the stopper-engaged piezoelectric energy harvester is numerically examined and validated with experimental results. Several settings of the gaps of the stoppers are discussed to see their impact on the performance. Overall, the simulated experimental results indicate that the broadband effect can be realized by adding two stoppers. The nonlinear effect is sufficient to improve the voltage output at the anti-resonant frequency, which is between the first two resonant frequencies, and completely connect two modes to achieve a wide bandwidth.