Abstract:
Manipulating mechanical energy intelligently,
passive exoskeletons can improve the energy efficiency of cyclic
human motions. Aiming to reduce the energy cost of knee
moment during stair ascent, this paper presents a concept of
brake-torque support activated when the knee moment is
required in the opposite direction to the angular velocity of the
knee joint. Integrating an electromagnetic brake to a crossing
four-bar knee joint with a compact design, the passive knee
exoskeleton enables the polycentric knee center of rotation
covering the wide range of knee angle during stair ascent. For
preliminary validation, the surface electromyography (EMG)
of rectus femoris (RF) and biceps femoris (BF) were studied on
a healthy male volunteer wearing the exoskeleton on his right
leg. The reduction of peak muscle activity is observed as the
brake torque is applied during knee extension while the knee
flexion moment is required.
