Rotational Vibration Energy Harvesting Enhancement with the Combinations of Centrifugal Effect, Gravity Effect and Bi-stable Restoring Effect

Abstract

Bi-stable piezoelectric-magnetic-elastic energy harvester (BPEH) has been widely investigated to improve the harvesting performance of low-frequency vibration energy. The centrifugal effect, gravity effect and bi-stable restoring effect and their combinations on the BPEH's potential wells and dynamic behaviors in rotational motions are completely different from those in low-frequency ambient vibrations, and they have not yet been well explored. This article presents a rotational bi-stable piezoelectric-magnetic-elastic energy harvester (R-BPEH) to enhance the rotational vibration energy harvesting with the combinations of the centrifugal effect, gravity effect and bi-stable restoring effect. A theoretical model considering the centrifugal effect, gravity effect and bi-stable restoring effect was established to describe the dynamic response behaviors of the R-BPEH. The centrifugal effect caused by the centrifugal force, gravity effect induced by the gravity of tip magnet, bi-stable restoring effect induced by the nonlinear magnetic force and their combinations on the potential energy wells, dynamic performance and power generation are theoretically explored under different system parameters, such as magnetic distance, rotating radius and rotational speed, etc. The results show that the centrifugal hardening stiffness induced by the centrifugal force of the R-BPEH can increase the oscillating frequency and harvesting voltage in high rotational speed range, but narrows the working bandwidth of inter-well motion; The gravity component in transverse direction generates additional periodical excitation force on the R-BPEH to produce high energy generations, the gravity component in axial direction softens the centrifugal hardening effect to enhance the energy generation in low rotational speed range. In addition, their combination leads to the appearances of asymmetric potential wells which further enhance the dynamic and electrical performances of the R-BPEH. Experiments are conducted to show good agreement with the theoretical results. The maximum harvested voltage and power generation of the R-BPEH achieves 2.5 V and 0.59 µW when the rotational speed ranges from 150 rpm to 540 rpm.