Logan High School InvenTeam
La Crosse, Wisconsin
2018-2019
The Logan High School InvenTeam invented an energy harvesting system to extend the battery life for vacuum socket units in above and below knee prostheses. By harvesting heel strike energy while walking, the system extends operating battery life beyond the current 24 hours. The invention is mounted by a prosthetic outfitter within the natural contour of the prosthetic foot and lower leg, requiring no prosthetic modification. The user will notice minimal to no change in the feel or use of the modified prosthetic. The system device weighs 376 grams with a total volume of 491 cm3. Current is generated using heel strike deflections with durations of 10-100 msec with 88 N of force. Energy harvesting is done using two spring coupled fast responding coreless rotor DC motors, which generate from 12 to 18 V and 25 to 100 mA. Rectification and charge storage in a capacitor array, subsequent power conversion, and regulation with a charge controller for the battery completes the power system. A Bluetooth™ communication link allows the user to monitor the energy storage system using a compatible cell phone and app.
