Parametric Design and Optimization of a Knee-Joint Biomechanical Energy Harvester to Maximize Power Generation With Minimal Metabolic Cost

Abstract

Reliable supplies of electric energy for the electrical devices carried by field workers is important for work and survival, while the hand-crank generator commonly used is toilsome. Using knee-joint biomechanical energy harvesters to harness dissipated biomechanical energy and generate electric power is an ingenious way to solve this problem. However, the lack of a parametric design method for the harvesters has caused power generation with large bioenergy consumption. In this work, we proposed an optimal design method for the parameters of the critical harvester components, including the generator, gearbox, and load resistor. Power generation and the total metabolic cost of the harvesting (TCOH) were set as the optimization objectives, and the equations to calculate both objectives were established. The optimal electric parameters of the generator were obtained by deduction and analysis of the equations, and the gear rate of the gearbox and resistance of the load resistor were optimized by a dynamic programming. Prototypes built with the optimized component parameters were tested in walking experiments. The prototypes can generate 6.16±1.47 W electric power with 11.9 W metabolic cost during 5 km/h walking. More generated power with much less metabolic cost was achieved compared with other knee-joint harvesters.