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Grip Amplifier: A Residual Force Control Strategy to Support Pinch Grip with a Minimalistic Hand Exoskeleton
Quentin Sanders, Joan Lobo-Prat, and David Reinkensmeyer
(University of California at Irvine, USA)
WIP Poster C2
Publisher's Version
Abstract: Hand exoskeletons could potentially improve hand use after a stroke or other conditions that weaken the hand, but are typically obtrusive, and it is still unclear how to provide intuitive control. Here, we propose and pilot test with unimpaired subjects a grip force control strategy suitable for a minimalistic hand exoskeleton. The strategy is based on three experimental observations seen in studies conducted in our lab with unimpaired individuals and stroke survivors. First, using only a pinch grip, unimpaired people can achieve a substantial level of clinical hand function. Second, people with severe hand impairment after stroke have a surprisingly well-preserved ability to control isometric finger flexion force. Third, force generation is highly correlated between fingers after a stroke. These observations suggest the strategy of measuring the isometric flexion force produced by digits 3-5 (middle-pinky finger) against the palm to control the force of an exoskeleton assisting in pinch grip, while preserving haptic input. We implemented this “residual force control” strategy using the FINGER exoskeleton and found that unimpaired subjects could intuitively use this strategy to pick up an object and learn to amplify their grip force with this strategy. We are preparing to test this “grip amplifier” with people with stroke.


Time stamp: 2019-03-23T20:19:50+01:00