Study on a narrowband concentration of vibration modes for a magnetostrictive vibration power generation device

Abstract

Expanding degrees of freedom in vibration systems is an effective way to improve the power generation efficiency of energy-harvesting devices from the vibrating source, since the system becomes responsive for a wide frequency range due to the appearance of multiple resonant peaks. A magnetostrictive-type vibration energy harvester that uses an iron-gallium alloy (Galfenol) has received much attention in recent years. Deformation of the cantilever yields a flux change due to tensile or compression stress, and the flux variation leads to the generation of voltage on the wound coils. This energy harvesting technology has advantages over conventional types with respect to the compactness and efficiency, and it is extremely robust and has low electrical impedance. In this study, the differential evolution (DE), known as a kind of global optimization techniques, was introduced for the parameter design of the harvester that comprised a folded beam structure with a concentrated mass at the beam end. Using DE, we numerically explored the best combination of the folded beam dimension that minimized the bandwidth between the first and second natural frequency of the harvester. The proposed design has led the device more responsive to the narrowband disturbances.