Shared autonomy and positive power control for powered exoskeletons

Abstract

Powered exoskeletons have been shown to significantly reduce physical workload during occupational tasks. Due to this they have great potential impact on future labor practices. However, powered exoskeleton controllers must first be developed that are able to directly assist with task objectives and truly collaborate with users. To address this need we present a shared autonomy control framework that separates the human and exoskeleton control objectives. This allows for creating a feedback-based exoskeleton controller that will help accomplish the user’s task goals rather than just assisting in specific motions. We introduce Positive Power control for the human-based controller that is designed to allow the human to directly command work that accomplishes the desired task. While a standard robotic controller can be used for the feedback-based control, we introduce ‘acceptance’ as a measure of how well the exoskeleton’s control objective matches the human’s. Both control objectives are implemented in an optimization-based Whole-Body-Control structure. Finally, we introduce a method to update the exoskeleton’s objectives to match the humans’ such that after operating for a time the exoskeleton can learn to assist the user in accomplishing their task. This framework is implemented on a 10-DoF upper-body powered exoskeleton. The results verify that the control framework works as desired and can form a basis for developing extended methods for directly improving cooperative control for powered exoskeletons.