Modelling of Broadband Piezoelectric Energy Harvesters

A nonlinear magnetic coupling model for piezoelectric energy harvesting systems is proposed in this paper. For the purpose of enhancing harvesting efficiency from wide-spectrum vibrations, a magnetic coupling structure of piezoelectric cantilevers is presented. However, the nonlinear dynamic of broadband piezoelectric energy harvesters could not be adequately described due to complex nonlinear magnetic force. Furthermore, the broken frequency can not be predicted using the designed dimensionless model. In order to solve those issues, the nonlinear magnetic force is established using polynomial equation. Based on Hamilton principle and finite element theory, a nonlinear model of the standard piezoelectric cantilever with magnetic coupling is established. Frequency sweeping experiments with various excitation are carried out. The results show that the output characteristic of the proposed model is approximate to that of experimental system under the same condition, and also their broken frequency is very close.