Knee-braced energy harvester: Reclaim energy and assist walking

In recent years, the increasing power requirement of wearable electronics and exoskeletons has made it very necessary to develop new methods of providing portable electrical power sources. In this paper, we present a knee-braced energy harvester to reclaim human kinetic energy and to assist human walking by redistributing the torque of the knee joint. The energy harvester is mounted at the knee and uses a spiral spring and generator to form a spring-damping mechanism. The spring-damping mechanism can partly replace the function of knee joint muscles during walking by reducing knee biomechanical torque and power; thus, the total metabolic energy used for walking can be reduced while electricity is generated at the same time. A prototype harvester was built to test the performance; the experimental results show that at the walking velocity of 4.2 km/h, the energy harvester can reduce the metabolic cost of walking by 3.6%, with a spring stiffness of 2 N·m/rad and an electrical damping coefficient of 0.5, and an average electrical power of 2.4 W is generated within the harvesting process.