Rationale, implementation and evaluation of assistive strategies for an active back-support exoskeleton

Stefano Toxiri, Axel S. Koopman, Maria Lazzaroni, Jesús Ortiz, Valerie Power, Michiel P. de Looze, Leonard O'Sullivan, Darwin G. Caldwell

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

Active exoskeletons are potentially more effective and versatile than passive ones, but designing them poses a number of additional challenges. An important open challenge in the field is associated to the assistive strategy, by which the actuation forces are modulated to the user's needs during the physical activity. This paper addresses this challenge on an active exoskeleton prototype aimed at reducing compressive low-back loads, associated to risk of musculoskeletal injury during manual material handling (i.e., repeatedly lifting objects). An analysis of the biomechanics of the physical task reveals two key factors that determine low-back loads. For each factor, a suitable control strategy for the exoskeleton is implemented. The first strategy is based on user posture and modulates the assistance to support the wearer's own upper body. The second one adapts to the mass of the lifted object and is a practical implementation of electromyographic control. A third strategy is devised as a generalized combination of the first two. With these strategies, the proposed exoskeleton can quickly adjust to different task conditions (which makes it versatile compared to using multiple, task-specific, devices) as well as to individual preference (which promotes user acceptance). Additionally, the presented implementation is potentially applicable to more powerful exoskeletons, capable of generating larger forces. The different strategies are implemented on the exoskeleton and tested on 11 participants in an experiment reproducing the lifting task. The resulting data highlights that the strategies modulate the assistance as intended by design, i.e., they effectively adjust the commanded assistive torque during operation based on user posture and external mass. The experiment also provides evidence of significant reduction in muscular activity at the lumbar spine (around 30%) associated to using the exoskeleton. The reduction is well in line with previous literature and may be associated to lower risk of injury.

LanguageEnglish
Article number53
Pages1-14
Number of pages14
JournalFrontiers in Robotics and AI
Volume5
Issue numberMAY
DOIs
Publication statusPublished - 25 May 2018

Fingerprint

Biomechanics
Materials handling
Torque
Experiments

Keywords

  • Electromyography
  • Exoskeleton
  • Manual material handling
  • Myocontrol
  • Powered
  • Strategy

VU Research Profile

  • Human Health and Life Sciences

Cite this

Toxiri, Stefano ; Koopman, Axel S. ; Lazzaroni, Maria ; Ortiz, Jesús ; Power, Valerie ; de Looze, Michiel P. ; O'Sullivan, Leonard ; Caldwell, Darwin G. / Rationale, implementation and evaluation of assistive strategies for an active back-support exoskeleton. In: Frontiers in Robotics and AI. 2018 ; Vol. 5, No. MAY. pp. 1-14.
@article{f87f17949f0b40888841702c0a16bf02,
title = "Rationale, implementation and evaluation of assistive strategies for an active back-support exoskeleton",
abstract = "Active exoskeletons are potentially more effective and versatile than passive ones, but designing them poses a number of additional challenges. An important open challenge in the field is associated to the assistive strategy, by which the actuation forces are modulated to the user's needs during the physical activity. This paper addresses this challenge on an active exoskeleton prototype aimed at reducing compressive low-back loads, associated to risk of musculoskeletal injury during manual material handling (i.e., repeatedly lifting objects). An analysis of the biomechanics of the physical task reveals two key factors that determine low-back loads. For each factor, a suitable control strategy for the exoskeleton is implemented. The first strategy is based on user posture and modulates the assistance to support the wearer's own upper body. The second one adapts to the mass of the lifted object and is a practical implementation of electromyographic control. A third strategy is devised as a generalized combination of the first two. With these strategies, the proposed exoskeleton can quickly adjust to different task conditions (which makes it versatile compared to using multiple, task-specific, devices) as well as to individual preference (which promotes user acceptance). Additionally, the presented implementation is potentially applicable to more powerful exoskeletons, capable of generating larger forces. The different strategies are implemented on the exoskeleton and tested on 11 participants in an experiment reproducing the lifting task. The resulting data highlights that the strategies modulate the assistance as intended by design, i.e., they effectively adjust the commanded assistive torque during operation based on user posture and external mass. The experiment also provides evidence of significant reduction in muscular activity at the lumbar spine (around 30{\%}) associated to using the exoskeleton. The reduction is well in line with previous literature and may be associated to lower risk of injury.",
keywords = "Electromyography, Exoskeleton, Manual material handling, Myocontrol, Powered, Strategy",
author = "Stefano Toxiri and Koopman, {Axel S.} and Maria Lazzaroni and Jes{\'u}s Ortiz and Valerie Power and {de Looze}, {Michiel P.} and Leonard O'Sullivan and Caldwell, {Darwin G.}",
year = "2018",
month = "5",
day = "25",
doi = "10.3389/frobt.2018.00053",
language = "English",
volume = "5",
pages = "1--14",
journal = "Frontiers in Robotics and AI",
issn = "2296-9144",
publisher = "Frontiers Media",
number = "MAY",

}

Rationale, implementation and evaluation of assistive strategies for an active back-support exoskeleton. / Toxiri, Stefano; Koopman, Axel S.; Lazzaroni, Maria; Ortiz, Jesús; Power, Valerie; de Looze, Michiel P.; O'Sullivan, Leonard; Caldwell, Darwin G.

In: Frontiers in Robotics and AI, Vol. 5, No. MAY, 53, 25.05.2018, p. 1-14.

Research output: Contribution to JournalArticleAcademicpeer-review

TY - JOUR

T1 - Rationale, implementation and evaluation of assistive strategies for an active back-support exoskeleton

AU - Toxiri, Stefano

AU - Koopman, Axel S.

AU - Lazzaroni, Maria

AU - Ortiz, Jesús

AU - Power, Valerie

AU - de Looze, Michiel P.

AU - O'Sullivan, Leonard

AU - Caldwell, Darwin G.

PY - 2018/5/25

Y1 - 2018/5/25

N2 - Active exoskeletons are potentially more effective and versatile than passive ones, but designing them poses a number of additional challenges. An important open challenge in the field is associated to the assistive strategy, by which the actuation forces are modulated to the user's needs during the physical activity. This paper addresses this challenge on an active exoskeleton prototype aimed at reducing compressive low-back loads, associated to risk of musculoskeletal injury during manual material handling (i.e., repeatedly lifting objects). An analysis of the biomechanics of the physical task reveals two key factors that determine low-back loads. For each factor, a suitable control strategy for the exoskeleton is implemented. The first strategy is based on user posture and modulates the assistance to support the wearer's own upper body. The second one adapts to the mass of the lifted object and is a practical implementation of electromyographic control. A third strategy is devised as a generalized combination of the first two. With these strategies, the proposed exoskeleton can quickly adjust to different task conditions (which makes it versatile compared to using multiple, task-specific, devices) as well as to individual preference (which promotes user acceptance). Additionally, the presented implementation is potentially applicable to more powerful exoskeletons, capable of generating larger forces. The different strategies are implemented on the exoskeleton and tested on 11 participants in an experiment reproducing the lifting task. The resulting data highlights that the strategies modulate the assistance as intended by design, i.e., they effectively adjust the commanded assistive torque during operation based on user posture and external mass. The experiment also provides evidence of significant reduction in muscular activity at the lumbar spine (around 30%) associated to using the exoskeleton. The reduction is well in line with previous literature and may be associated to lower risk of injury.

AB - Active exoskeletons are potentially more effective and versatile than passive ones, but designing them poses a number of additional challenges. An important open challenge in the field is associated to the assistive strategy, by which the actuation forces are modulated to the user's needs during the physical activity. This paper addresses this challenge on an active exoskeleton prototype aimed at reducing compressive low-back loads, associated to risk of musculoskeletal injury during manual material handling (i.e., repeatedly lifting objects). An analysis of the biomechanics of the physical task reveals two key factors that determine low-back loads. For each factor, a suitable control strategy for the exoskeleton is implemented. The first strategy is based on user posture and modulates the assistance to support the wearer's own upper body. The second one adapts to the mass of the lifted object and is a practical implementation of electromyographic control. A third strategy is devised as a generalized combination of the first two. With these strategies, the proposed exoskeleton can quickly adjust to different task conditions (which makes it versatile compared to using multiple, task-specific, devices) as well as to individual preference (which promotes user acceptance). Additionally, the presented implementation is potentially applicable to more powerful exoskeletons, capable of generating larger forces. The different strategies are implemented on the exoskeleton and tested on 11 participants in an experiment reproducing the lifting task. The resulting data highlights that the strategies modulate the assistance as intended by design, i.e., they effectively adjust the commanded assistive torque during operation based on user posture and external mass. The experiment also provides evidence of significant reduction in muscular activity at the lumbar spine (around 30%) associated to using the exoskeleton. The reduction is well in line with previous literature and may be associated to lower risk of injury.

KW - Electromyography

KW - Exoskeleton

KW - Manual material handling

KW - Myocontrol

KW - Powered

KW - Strategy

UR - http://www.scopus.com/inward/record.url?scp=85050115665&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85050115665&partnerID=8YFLogxK

U2 - 10.3389/frobt.2018.00053

DO - 10.3389/frobt.2018.00053

M3 - Article

VL - 5

SP - 1

EP - 14

JO - Frontiers in Robotics and AI

T2 - Frontiers in Robotics and AI

JF - Frontiers in Robotics and AI

SN - 2296-9144

IS - MAY

M1 - 53

ER -