A Pendulum-Type Tunable Multidirectional Piezoelectric Vibration Energy Harvester: Design, Fabrication, and Experiment

Harvesting energy from environmental vibrations using piezoelectric mechanism has attracted much attention for powering wireless sensors over the past decades. To enhance the environmental adaptability of energy harvesters, a pendulum-type tunable multidirectional piezoelectric vibration energy harvester (PTM-PVEH) is proposed in this article. The PTM-PVEH consists of piezo-cantilevers and a multidirectional pendulum (MDP) which can oscillate in any direction and pluck the piezo-cantilever to only yield unidirectional compressive stress. Theoretical analysis and experimental test were performed to validate working parameters and structural parameters that influenced the power generation capabilities of PTM-PVEH. The results showed that PTM-PVEH was capable of harvesting omnidirectional vibration energy. Also, the resonant frequency of PTM-PVEH could be tuned from 15 to 11.5 Hz by adjusting the proof mass and the torsion radius to adapt to low-frequency environmental vibrations. Moreover, at arbitrary horizontal excitation angles, the maximum power fluctuation of PTM-PVEH was only 7%, which demonstrated that PTM-PVEH had good multidirectional consistency. Additionally, the optimum output power of PTM-PVEH could reach 4.73 mW with the load resistance of 400 k $\Omega $ at 11.5 Hz under the maximum excitation acceleration of 2 g. Furthermore, PTM-PVEH could light 100 LEDs as well as power a temperature sensor and a transmitter module continuously.