Structure design of active power-assist lower limb exoskeleton APAL robot

Active power-assist exoskeletons are becoming more prospective than follow-up types, especially for elderly and handicapped motion auxiliary. The exoskeleton is required not only to withstand load but also to actively share the weight of a human body. Active power-assist lower limb is designed to meet this expectation. The definition of “active power-assist” was suggested in this article. A unique man–machine motion mapping was derived based on the configuration matching, wherein the exoskeleton obtains the wearer’s motion data and parse out the corresponding intention. Man–machine coupling mechanisms were exquisitely configured, which rationalize the degrees of freedom of the man–machine system and facilitate force transmission for active assistant. The dynamic knees and hip joints with the integrated force servo unit were designed, which is the key to realize soft contact and cooperative movement. The prototype was developed, and three basic functions (human movement perception, force transmission, and movement cooperation) were preliminarily verified in a single leg swinging experiment. The effect of follow-up mode and active power-assist mode were quantitatively analyzed in marches-on-the-spot experiment. A 24.6% proportional reduction of the wearer foot force and smooth man–machine coordination in field experiments has demonstrated the feasibility of this structure design of active power-assist lower limb.