Finite element analysis and design of a magnetostrictive material based vibration energy harvester with a magnetic flux path

This work presents the development of a nonlinear 2D finite element (FE) framework for magnetostrictive material based energy harvesters of beam geometry. The FE model is developed in COMSOL Multiphysics and compared with existing literature for validation. The FE model is subsequently used to study the effect of a closed magnetic flux path, consisting of ferromagnetic components, on the harvester output. Specifically, the voltage output is obtained by performing simulations on unimorph type harvester devices with and without a closed magnetic flux path, both operating at the same natural frequency and volume of the magnetostrictive material Galfenol. The harvester design considered here consists of a magnetostrictive layer (Galfenol) bonded to a steel substrate layer, a tip mass, a pick-up coil and a magnetic flux path consisting of soft iron core and NdFeB permanent magnets. Our results demonstrate a voltage gain of around 70% for the closed flux path design. Furthermore, a proof of concept prototype of the modified flux path design is developed, tested under impulse loading, and the voltage, power output are compared with FE simulation results for validation. The simulation results match well with experimental observations at two operating frequencies for the flux path design.