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Key insights into hand biomechanics: Human grip stiffness can be decoupled from force by cocontraction and predicted from electromyography

Höppner, Hannes and Stillfried, Georg and Große-Dunker, Maximilian and Bayer, Justin and van der Smagt, Patrick (2016) Key insights into hand biomechanics: Human grip stiffness can be decoupled from force by cocontraction and predicted from electromyography. Frontiers in Neurorobotics, 11. Frontiers Media S.A.. doi: 10.3389/fnbot.2017.00017. ISSN 1662-5218.

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Official URL: http://journal.frontiersin.org/article/10.3389/fnbot.2017.00017/


We investigate the relation between grip force and grip stiffness for the human hand with and without voluntary cocontraction. Apart from gaining biomechanical insight, this issue is particularly relevant for variable-stiffness robotic systems, which can independently control the two parameters, but for which no clear methods exist to design or efficiently exploit them. Subjects were asked in one task to produce different levels of force, and stiffness was measured. As expected, this task reveals a linear coupling between force and stiffness. In a second task, subjects were then asked to additionally decouple stiffness from force at these force levels by using cocontraction. We measured the electromyogram from relevant groups of muscles and analyzed the possibility to predict stiffness and force. Optical tracking was used for avoiding wrist movements. We found that subjects were able to decouple grip stiffness from force when using cocontraction on average by about 20% of the maximum measured stiffness over all force levels, while this ability increased with the applied force. This result contradicts the force–stiffness behavior of most variable-stiffness actuators. Moreover, we found the thumb to be on average twice as stiff as the index finger and discovered that intrinsic hand muscles predominate our prediction of stiffness, but not of force. EMG activity and grip force allowed to explain 72 ± 12% of the measured variance in stiffness by simple linear regression, while only 33 ± 18% variance in force. Conclusively the high signal-to-noise ratio and the high correlation to stiffness of these muscles allow for a robust and reliable regression of stiffness, which can be used to continuously teleoperate compliance of modern robotic hands.

Item URL in elib:https://elib.dlr.de/110122/
Document Type:Article
Title:Key insights into hand biomechanics: Human grip stiffness can be decoupled from force by cocontraction and predicted from electromyography
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Date:21 December 2016
Journal or Publication Title:Frontiers in Neurorobotics
Refereed publication:Yes
Open Access:Yes
Gold Open Access:Yes
In ISI Web of Science:Yes
Publisher:Frontiers Media S.A.
Keywords:Grip Stiffness, grip force, intrinsic hand muscles, Interosseus muscles, Electromyography, Co-contraction, soft robotics, Variable-Stiffness Actuators, Robotic hand-design
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space System Technology
DLR - Research area:Raumfahrt
DLR - Program:R SY - Space System Technology
DLR - Research theme (Project):R - Vorhaben Weiterentwicklung Robotik - Mechatronik und Dynamik (old)
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Robotics and Mechatronics (since 2013) > Mechatronic Components and Systems
Institute of Robotics and Mechatronics (since 2013) > Cognitive Robotics
Deposited By: Höppner, Hannes
Deposited On:04 Jan 2017 10:35
Last Modified:27 Nov 2023 14:07

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