Energy harvesting from human motion - exploiting swing and shock excitations

K. Ylli, D. Hoffmann, A. Willmann, P. Becker, B. Folkmer and Y. Manoli (Institute of Micromachining and Information Technology)

CHALLENGE - Energy harvesting for body-worn or body-attached applications has seen a significant amount of research interest as it can potentially provide the solution for powering modern low-power sensor systems and increase the mobility and independence of the user. However, the key bottleneck of this technology is the power supply. The use of energy harvesting techniques offers a way of supplying sensor systems without the need for batteries and maintenance. In this work, the development and characterization of two inductive energy harvesters are developed, which exploit different characteristics of the human gait.

SOLUTION - A multi-coil topology harvester is presented which uses the swing motion of the foot. The second device is a shock type harvester which is driven into resonance upon heel strike. Both devices were modeled and designed with the key constraint of device height in mind, in order to facilitate the integration into the shoe sole. The devices were characterized under different motion speeds and with two test subjects on a treadmill. In order to meet the requirement of a reduced device height while generating the maximum power output, the magnet-in-channel model was optimized using the optimization software modeFRONTIER. The built-in multi-objective genetic algorithm MOGA-II was used.








BENEFITS - Although based on different physical principles, both devices show similarities in the patterns of the power outputs. In conclusion, the highest average power output of 4.13mW was measured on ground at a motion speed of 5kmh−1 for the shock type harvester, while the highest measured average power of the swing-type harvester was 0.84mW at a motion speed of 6 kmh−1 on a treadmill.