Figure 4
Biomechanical knee energy harvester [24]. (A) The device has an aluminium chassis and generator (blue) mounted on a customized orthopedic knee brace, totalling 1.6 kg; one such brace is worn on each leg. (B) The chassis contains a gear train that converts the low velocity and high torque of the knee motion into the high velocity and low torque required for the generator operation, with a one-way clutch that allows for selective engagement of the gear train only during knee extension and no engagement during knee flexion. (C) The schematic diagram shows how a computer-controlled feedback system determines when to generate power using knee-angle feedback, measured with a potentiometer mounted on the input shaft. Generated power is dissipated in resistors. Rg, generator internal resistance; R L , output load resistance; E(t), generated voltage. (Reprinted with permission from Science Incorporated.)