Design of a vibration energy harvester with two close resonant frequencies

We present the design of a piezoelectric cantilever with a L-shaped proof mass and multiples electrodes allowing vibration energy harvesting at two close frequencies. Indeed, the resonant frequencies of the proposed harvester are 35.3 Hz and 53.2 Hz for the first and second bending modes, respectively. Based on a study of the strain distribution with an analytical model, we provide design guidelines for the electrodes’ configuration to maximize the electromechanical coupling coefficients $k^{2}$ of a PZT-based harvester. When the electrodes are judiciously connected, the coefficient $k^{2}$ reaches 9.3 % for the first mode and 8.1 % for the second mode, allowing 3 Hz (8.4 %) and 3.5 Hz (6.5 %) frequency bandwidths with resistive frequency tuning respectively.