A body hair-inspired multi-directional piezoelectric energy harvester with spatial internal resonance effect

To improve the ability of piezoelectric energy collection (PEH) devices to convert multi-directional energy sources, a body hair-inspired multi-directional broadband piezoelectric energy harvester with spatial internal resonance effect is proposed. It is constructed from a zigzag beam and a rigid pendulum. The motion of the pendulum in three orthogonal directions causes bending deformation of the fixed-end of the zigzag beam. Furthermore, the system can also achieve internal resonances in all three directions, broadening the system bandwidth. This paper presents the configuration and working principle inspired by this concept along with the dynamic equations of its electromechanical system. The resulting analytical and numerical solutions are given. The forced responses of the system at spatial internal resonance under different excitation levels were analyzed in the frequency domain. The prototype was fabricated and the experimental setup was built up to measure the output characteristics. Experimental results show that the proposed PEH device can achieve spatial multi-degree-of-freedom collection of vibration energy and provide stable and considerable voltage output levels under excitation in three orthogonal directions. Moreover, the working bandwidth of the system increases with the increase of external excitation level. The proposed PEH device exhibits high energy harvesting capability and potential application in complex excitation environments.