Enhanced vibration energy harvesting of magnetically coupled piezoelectric cantilever beam with double-point stopper

Piezoelectric fragility is concerned with low broadband and large amplitude vibration for energy harvesting in human motion, vehicles, wave energy, etc. The design of the stopper is helpful for the protection and broadband of the piezoelectric vibration energy harvester (PVEH), but the output is limited due to uneven stress distribution and collision energy loss. This paper proposes a U-shaped mass PVEH with double-point stopper and magnetic coupling. The stress homogenization method of the cantilever beam is achieved by converting the collision energy into bending moment by double-point stopper, which effectively improves the electromechanical coupling coefficient of the structure. Thus, the double-point stopper enables 1.5 times saturation displacement within allowable PZT stress. The experimental performance is carried out that PVEH with double-point stopper and magnetic coupling has double higher power output of 10.2 mW than single-point stopper at the excitation level of 0.6 g. The stopper collision and the magnetic coupling broaden the high and low frequency response of the PVEH system jointly. It has voltage output beyond 40 V with broadband of 8–15.6 Hz under 1 g acceleration in test. This work has a good potential in the occasions of the big mass, stopper protection and magnetic coupling design for low frequency, broadband and large amplitude of PVEH.