An electromagnetic wearable 3-DoF resonance human body motion energy harvester using ferrofluid as a lubricant

Abstract

Wearable Energy harvester offers clean and continuous power for wearable sensors or devices, which can play an important role in the health monitoring, motion track and so on. In this study, we investigated a small electromagnetic resonance wearable kinetic energy harvester. A permanent magnet (PM) which was tied with two springs is forming a 3-degree-of-freedom (3-DoF) vibrator and is put in a box. Ferrofluid was adopted which is adsorbed at the pole of PM and makes the PM away from the surface of the box which decreased the friction significantly. Coils are placed on the outside surface and the electric energy is generated when the PM is vibration. It can be used to harvest kinetic energy of human and offer continuous power. The effect of ferrofluid was simulated and analyzed which indicated that the ferrofluid can keep the PM contactless even under 10 times gravity acceleration. A prototype was developed and tested under different loading conditions. Resistance load experiments results indicated that the proposed harvester can generate 0.75mW average power when walking and 1.4mW when running. An energy storage circuit which can transfer the generated alternating power to 5V direct current was developed to store the electrical power into capacitor. Energy storage experiments results indicated that the average storage power when walking and running are 20.8µW and 35.2µW, respectively. The developed harvester can be placed on the shoe and used to offer continuous

Wearable Biomechanical Energy Harvesting Technologies

“…Typically, an axially magnetized permanent magnet oscillating inside a cylindrical coil along the axis of the coil is used [32,35,37,39]; in other cases, the permanent magnet oscillating radially at the end of the coil is used [36,38]. The oscillation evoked by human motions is maintained by using mechanical spring [36], magnetic spring [32,35,39], or both [37]. Some energy harvesters use human joint motion directly for achieving relative movement between a permanent magnet and a coil [33,38].…”

“…Energy harvesting principles for mechanical kinetic energy include piezoelectric [10][11][12][13][14][15][16][17][18][19][20][21], triboelectric [22][23][24][25][26][27][28][29][30][31], and electromagnetic energy harvesting [1,[32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48], as shown in Figure 1. Electromagnetic generators can be categorized into two types, namely inertial induction [32][33][34][35][36][37][38][39] and gear-and-generator [1,…”

Research on the Axial Magnetic Levitation Force Acting on the Ring Magnet Suspended in Magnetic Fluid : Considering a Radial Eccentricity

“…Later in the book titled "ferrohydrodynamic", Rosensweig gave a detailed description on the particular magnetic levitation force (selfsuspension buoyancy) by means of magnetic fluid stress tensor [3]. Up to now, this property of magnetic fluid has been exploited in many innovative devices, such as dampers [4][5][6], sensors [7][8][9][10][11], actuators [12][13][14], bearings [15,16], micromechanical system [17][18][19] and so on.…”

Minimising the effects of manufacturing uncertainties in MEMS Energy harvesters

“…In our environment, there are a variety of ambient energy sources such as solar, temperature, wind and vibration. Converting waste ambient energy into small amounts of electrical energy can power many useful low energy consuming Micro Electro Mechanical systems (MEMS) in different applications ranging from wireless sensor networks to medical implants [1][2][3][4][5].…”