Integral admittance shaping: A unified framework for active exoskeleton control

Nagarajan, U; Aguirre-Ollinger, G; Goswami, A

Integral admittance shaping: A unified framework for active exoskeleton control

Nagarajan, U Aguirre-Ollinger, G

Goswami, A

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Publication Type:: Journal Article
Citation:: Robotics and Autonomous Systems, 2016, 75 pp. 310 - 324
Issue Date:: 2016-01-01

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Field	Value	Language
dc.contributor.author	Nagarajan, U	en_US
dc.contributor.author	Aguirre-Ollinger, G https://orcid.org/0000-0001-5377-215X	en_US
dc.contributor.author	Goswami, A	en_US
dc.date.available	2020-05-25T19:03:21Z
dc.date.issued	2016-01-01	en_US
dc.identifier.citation	Robotics and Autonomous Systems, 2016, 75 pp. 310 - 324	en_US
dc.identifier.issn	0921-8890	en_US
dc.identifier.uri	http://hdl.handle.net/10453/37489
dc.description.abstract	© 2015 Elsevier B.V. Current strategies for lower-limb exoskeleton control include motion intent estimation, which is subject to inaccuracies in muscle torque estimation as well as modeling error. Approaches that rely on the phases of a uniform gait cycle have proven effective, but lack flexibility to aid other kinds of movement. This research aims at developing a more versatile control that can assist the lower limbs independently of the movement attempted. Our control strategy is based on modifying the dynamic response of the human limbs, specifically their mechanical admittance. Increasing the admittance makes the lower limbs more responsive to any muscle torque generated by the human user. We present Integral Admittance Shaping, a unified mathematical framework for: (a) determining the desired dynamic response of the coupled system formed by the human limb and the exoskeleton, and (b) synthesizing an exoskeleton controller capable of achieving said response. The present control formulation focuses on single degree-of-freedom exoskeleton devices providing performance augmentation. The algorithm generates a desired shape for the frequency response magnitude of the integral admittance (torque-to-angle relationship) of the coupled system. Simultaneously, it generates an optimal feedback controller capable of achieving the desired response while guaranteeing coupled stability and passivity. The potential effects of the exoskeleton's assistance are motion amplification for the same joint torque, and torque reduction for the same joint motion. The robustness of the derived exoskeleton controllers to parameter uncertainties is analyzed and discussed. Results from initial trials using the controller on an experimental exoskeleton are presented as well.	en_US
dc.relation.ispartof	Robotics and Autonomous Systems	en_US
dc.relation.isbasedon	10.1016/j.robot.2015.09.015	en_US
dc.subject.classification	Industrial Engineering & Automation	en_US
dc.title	Integral admittance shaping: A unified framework for active exoskeleton control	en_US
dc.type	Journal Article
utslib.citation.volume	75	en_US
utslib.for	0801 Artificial Intelligence and Image Processing	en_US
utslib.for	0906 Electrical and Electronic Engineering	en_US
utslib.for	0913 Mechanical Engineering	en_US
pubs.embargo.period	Not known	en_US
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Engineering and Information Technology
pubs.organisational-group	/University of Technology Sydney/Faculty of Engineering and Information Technology/School of Mechanical and Mechatronic Engineering
utslib.copyright.status	open_access
pubs.publication-status	Published	en_US
pubs.volume	75	en_US

Abstract:

© 2015 Elsevier B.V. Current strategies for lower-limb exoskeleton control include motion intent estimation, which is subject to inaccuracies in muscle torque estimation as well as modeling error. Approaches that rely on the phases of a uniform gait cycle have proven effective, but lack flexibility to aid other kinds of movement. This research aims at developing a more versatile control that can assist the lower limbs independently of the movement attempted. Our control strategy is based on modifying the dynamic response of the human limbs, specifically their mechanical admittance. Increasing the admittance makes the lower limbs more responsive to any muscle torque generated by the human user. We present Integral Admittance Shaping, a unified mathematical framework for: (a) determining the desired dynamic response of the coupled system formed by the human limb and the exoskeleton, and (b) synthesizing an exoskeleton controller capable of achieving said response. The present control formulation focuses on single degree-of-freedom exoskeleton devices providing performance augmentation. The algorithm generates a desired shape for the frequency response magnitude of the integral admittance (torque-to-angle relationship) of the coupled system. Simultaneously, it generates an optimal feedback controller capable of achieving the desired response while guaranteeing coupled stability and passivity. The potential effects of the exoskeleton's assistance are motion amplification for the same joint torque, and torque reduction for the same joint motion. The robustness of the derived exoskeleton controllers to parameter uncertainties is analyzed and discussed. Results from initial trials using the controller on an experimental exoskeleton are presented as well.

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http://hdl.handle.net/10453/37489