A multimodal E-shaped piezoelectric energy harvester with a built-in bistability and internal resonance

The abundant and renewable vibration energy has been regarded as an alternative power source for the massive sensors of the Internet of Things, but the broadband and efficient vibration energy harvesting is still an open issue. In this paper, a broadband E-shaped bistable piezoelectric energy harvester (EBPEH) is developed by taking advantages of nonlinear and multimodal techniques. It is consisted of a steel U-shaped host beam (UHB) and a steel parasitic piezoelectric cantilever beam (PPCB). The nonlinear interaction between a tip magnet of the PPCB with the UHB cause a built-in bistability of the harvester, eliminating the need of any external magnet and leading to a compact structure. By appropriately designing multimodal frequencies of two beams, a 1:2 internal resonance phenomenon in the first response frequency band occurs, and an overlapping of them above a low excitation amplitude threshold cause a triple bandwidth enhancement from 6 Hz to 18.5 Hz. Attributed to the nonlinear hardening phenomenon, the peak voltage and the RMS peak power can reach 56.1 V and 786.8 mu W under the 0.5 g up sweep excitation, respectively. It is proved that the proposed EBPEH has the ability to harvest wideband and low frequency vibration energy.