A simple model of our biomechanical energy harvester. The input shaft accepts the knee motion at 1:1 ratio through a simple hinge (uni-axis) knee brace. A one-way clutch on the input shaft couples the gear train with knee motion during knee extension, and decouples the gear train from knee motion during knee flexion. The gear train transfers the low speed (ωk) but high torque (τr) mechanical power into high speed (ωg) and low torque (τg) mechanical power suitable for power generation. A miniature brushless DC generator converts the mechanical energy in to electrical energy where E is the generated electrical potential, Rg is the generator terminal resistance and Rl is the external electrical load.
Li et al. Journal of NeuroEngineering and Rehabilitation 2009 6:22 doi:10.1186/1743-0003-6-22