Abstract
Exoskeletons aim to enhance human performance and reduce physical
fatigue. However, one major challenge for active exoskeletons is the
need for a power source. This demand is typically met with batteries,
which limit the operational time of the device. A novel solution to this
challenge is a design that enables the generation of electricity during
motions where the muscles work as brakes, with the energy stored and
subsequently returned to assist when the muscles act as motors. This
could lead to a fully autonomous exoskeleton. To achieve this goal, a
knee exoskeleton design with a direct drive and a novel electronic board
was designed and manufactured to capture the energy generated by the
wearerâ\euro™s movements and convert it into electrical energy. The
harvested energy is stored in a power bank, and, later, the motion is
used to power the exoskeleton motor. Further, the device has torque
control and can change the assistive profile and magnitude as needed for
different assistance scenarios. Sit-to-stand (STS) motion was chosen as
a test case for the exoskeleton device. It was found that, during rising
(from sit to stand), the exoskeleton provided up to 7.6 Nm and harvested
9.4 J. During lowering (from stand to sit, (it provided up to 10 Nm and
was able to return 6.8 J of the harvested energy. Therefore, the cycle
efficiency of the exoskeleton system (return divided by harvesting) is
72.3%. The results show that this technology has the potential to
revolutionize exoskeletons and reduce the need for external energy
sources.