Design of smart harvester for capturing energy from human ankle dorsiflexion to reduce user effort

Abstract

Scavenging energy from human motion is a potential way to meet the increasing requirement of electrical power supply for portable electronics. However, since the conventional energy harvesters may collect both positive and negative work, the users have to pay extra effort. This work aims at developing a smart energy harvester to identify and capture the negative work of human ankle motion. During normal walking, only dorsiflexion of ankle joint at stance phase performs negative work. Thus, one-way clutch is employed to filter ankle plantarflexion and mechanical contact switch array is used to disconnect resistance load, avoiding capturing positive work when ankle dorsiflexion is at swing phase. With the oneway clutch and mechanical contact switch array, the energy harvester can effectively target negative work as energy scavenged without consuming electrical energy. The energy harvester is designed based on proposed principles. It is also modeled to predict the output power, efficiency and assistive torque. The simulation results show that the energy harvester can provide enough power for portable electronics and it is helpful in reducing ankle moment.