Design and Construction of Magnetostrictive Harvester for Gait Monitoring of Human Actives

In this paper, we presented a new structure of a magnetostrictive energy harvester, which has a short-time impact piezomagnetic effect and can generate electricity during human walking. The harvester utilizes the hybrid magnetostrictive/electromagnetic effect, which helps to enhance its piezomagnetic effect in TbDyFe Alloy (magnetostrictive material). Also, an air gap is designed to improve its harvesting effect, which exhibits a larger numerical variation of magnetic field and impact stress, helping to generate more electricity. A prototype of a magnetostrictive harvester with a basic magnetic field and suitable air gap is configured, and its harvesting effect is calculated. The distribution nephogram of magnetization is analyzed, the magnetic density in the TbdyFe Alloy are calculated, and the optimized length of the air gap is determined. Then, we fabricated a prototype of the harvester, its harvesting effects are tested and calculated. The proposed structure shows a larger induced voltage for impact situations, which can generate up to 0.5-8V peak value for different impact vibrations. Also, the presented harvester can be safely used in the situation of low-frequency human walking (about 600N with 7.6MPa stress) and faster human running (about 1850N with 23.6MPa transient impact), which is suitable to be used for the application of gait monitoring systems.

I. Introduction

The energy of walking is one of the most popular human activities in our daily life. We can design the microsensor to monitor the gait behavior, and use it to assess the health status of human Actives. Also, we can design smart energy harvesters to generate electricity, which is a benefit to the application of self-powered devices ^[1]–[3]. The focus of this paper is to try to design a smart energy harvester, which can harvest the power of human walking, and its signal of induced voltage can be used for the gait monitoring of human activities ^[4]–[5].