Micro linear generator for harvesting mechanical energy from the human gait

A type of multipolar linear permanent magnet generator (MLPMG) was developed in order to harvest human lower-limb motion energy to meet the increasing power supply needs of portable electronic devices. A large acceleration of the foot, particularly at the heel, was noted when analyzing human lower-limb motion during walking, so an energy harvester was placed on the heel. A series of MLPMGs were then designed and the static magnetic induction intensity vector diagram was obtained from each. A key parameter of MLMPG efficiency was found to be the gap between the stator and mover. Another important factor is the thickness of the mover spacers between magnet pieces. Finally, a number of experiments were conducted, which supported the conclusion that the output power of harvesters have negative relation with length of gap and thickness of spacers. It was found that a subject, walking at a speed of 5 km/h with a matched resistor load, can produce an output power of 20 mW.