Design, modeling and experiments of a novel biaxial-pendulum vibration energy harvester

Pendulum-based vibration energy harvesting is a promising technology to supply energy for floating buoys and small ocean vehicles. However, the energy harvester with a uniaxial pendulum requires a specific direction of vibration excitation generated by wave. This paper develops a novel biaxial-pendulum vibration energy harvester, where a hemispherical pendulum can rotate around two axes simultaneously to adapt the direction of vibration excitation. Moreover, magnets and coils are distributed on the surfaces of the pendulum and the shell respectively to achieve a compact structure. The dynamics of the energy harvester are described based on Lagrangian approach. Electromagnetic analysis in three dimensions is carried out by using finite element method to obtain the spatial magnetic field distribution of the energy harvester. The relationship between the vibration excitation and the output voltage is modeled by taking dynamics and electromagnetic analysis into account together. A small-scale prototype of the proposed energy harvester is fabricated and tested through a six degree-of-freedom motion platform. It is found that the prototype can generate electricity with peak voltage and power of 14.25 V and 2.03 W when the excitation acceleration is 0.18 g. The analytical results and the experimental results are also in good agreement with each other.