A Powered Hip Exoskeleton With High Torque Density for Walking, Running, and Stair Ascent

Abstract

Powered exoskeletons need actuators that can generate substantial assistive torque and orthoses that can efficiently transfer the assistive torque to the user. Powered exoskeletons also need to be lightweight and ergonomic to minimize the negative effects wearing the exoskeleton has on the user's effort and comfort. Here we present the design, development, and validation of an autonomous powered hip exoskeleton with high torque density. The exoskeleton actuator is based on a four-bar mechanism with integrated composite springs. A compact carbon fiber frame encloses the custom actuator, doubling as the exoskeleton thigh linkage. A self-aligning mechanism is used to avoid uncomfortable spurious forces and torques on the user's limb. Custom pelvis and thigh braces are developed using composite materials to reduce weight. A custom embedded electronic system is integrated into the pelvis brace to minimize the device weight and electrical consumption. Experiments show that the proposed powered hip exoskeleton can produce high nominal torque (41.9 Nm repetitive peak torque), high backdrivability (0.16 Nm back-driving torque), high bandwidth (23.8 Hz), and high control accuracy (2.1% steady-state error). Human tests show that the proposed exoskeleton can assist in walking, running, and stairs climbing.