TitleEffect of Homogenous Object Stiffness on Tri-digit Grasp Properties
Publication TypeConference Paper
Year of Publication2015
Conference Name37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC2015)
Pagination6704 - 6707
AuthorsGodfrey, SB, Altobelli, A, Rossi, M, Bicchi, A
Conference Location Milano, Italy, August 25th-29th, 2015
KeywordsHaptics, Robotics
This paper presents experimental findings on how humans modulate their muscle activity while grasping objects of varying levels of compliance. We hypothesize that one of the key abilities that allows humans to successfully cope with uncertainties while grasping compliant objects is the ability to modulate muscle activity to control both grasp force and stiffness in a way that is coherent with the task. To that end, subjects were recruited to perform a grasp and lift task with a tripod-grasp device with contact surfaces of variable compliance. Subjects performed the task under four different compliance conditions while surface EMG from the main finger flexor and extensor muscles was recorded along with force and torque data at the contact points. Significant increases in the extensor muscle (the antagonist in the task) and co-contraction levels were found with increasing compliance at the contact points. These results suggest that the motor system may employ a strategy of increasing cocontraction, and thereby stiffness, to counteract the decreased stability in grasping compliant objects. Future experiments will examine the extent to which this phenomenon is also related to specific task features, such as precision versus power grasp and object weight.
This work is supported in part by the European Research Council under the Advanced Grant SoftHands “A Theory of Soft Synergies for a New Generation of Artificial Hands” no. ERC-291166 and under the EU FP7 project WEARHAP “WEARable HAPtics for Humans and Robots” no. 601165.
Refereed DesignationRefereed
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