A one-degree-of-freedom assistive exoskeleton with inertia compensation: the effects on the agility of leg swing motion

Sage Publications - Professional Engineering Publishing Ltd.
Publication Type:
Journal Article
Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine, 2011, 225 (3), pp. 228 - 245
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Many of the current implementations of exoskeletons for the lower extremities are conceived to either augment the userâs load-carrying capabilities or reduce muscle activation during walking. Comparatively little research has been conducted on enabling an exoskeleton to increase the agility of lower-limb movements. One obstacle in this regard is the inertia of the exoskeletonâs mechanism, which tends to reduce the natural frequency of the human limbs. A control method is presented that produces an approximate compensation of the inertia of an exoskeletonâs mechanism. The controller was tested on a statically mounted, single-degree-offreedom (DOF) exoskeleton that assists knee flexion and extension. Test subjects performed multiple series of leg-swing movements in the context of a computer-based, sprint-like task. A large initial acceleration of the leg was needed for the subjects to track a virtual target on a computer screen. The uncompensated inertia of the exoskeleton mechanism slowed down the transient response of the subjectsâ limb, in comparison with trials performed without the exoskeleton. The subsequent use of emulated inertia compensation on the exoskeleton allowed the subjects to improve their transient response for the same task.
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