Magnetostrictive energy harvester with adjustable-air gap for low frequency human walking

This paper presents a prototype of magnetostrictive material-based vibration energy harvester, which is used to generate electricity during human walking with high power density. According to Villari effect (inverse-magnetostrictive effect), the harvester consists of a coil-wound magnetostrictive rod. In order to improve the harvesting effect, a magnetostrictive/electromagnetic hybrid configuration with an adjustable air gap is designed. It is followed with detailed analysis of mode effects on ΔB induced by single Δσ and ΔH for optimized design. Then, the magnetic field and leakage of the harvester are analyzed, mechanical parameters of the harvester are optimally determined. Lastly, a prototype of harvester is fabricated and tested. The proposed structure has larger piezomagnetic effect than traditional harvesters, especially under the 5-10MPa compress stress (impact of human walking is set about 5-12.5MPa). Also, it has good harvesting effects in 0.01-0.1s impact vibration time, and can be safely used in up to 20MPa transient impact, which is suitable for future researches of power generating floor systems.