The Flicking Device

Overview

Flicking is an inherently social action; used in games around the world such as Subbuteo, Shove Ha'penny, and Carrom. With a humanoid prosthesis, building and releasing mechanical energy is very hard to achieve without manually pulling and releasing each finger. Our flicking device replaces one finger of the OLYMPIC hand, and uses a ratchet-release mechanism to produce flicking motion of varying strengths.

Design

Schematic diagram, annotated with key components.

Real terminal device drawing and releasing the striker.

Mechanical Design

Motor rotation is use to wind and draw the striker.
Motor rotation in the opposite direction winds the release carriage.

Control

Two electrodes reading muscle activity.
In one direction, tensing draws the striker continuously.
In the other direction, tensing releases the striker.

Testing

Experiment - Flicking Discs

Used to test flicking accuracy.
Users must flick a disc at a series of target discs.
Performance metric: disc hit rate.
Repeated 5 times at 7 target locations.

Results

Task Performance

Target hit rate using the Flicking Device was significantly higher (p<0.001, Mann-Whitney U test) than the humanoid hand: 0.650 vs 0.429.

Participants with upper limb difference performed similarly to group results of participants without upper limb difference. Participant 1 outperformed all other participants, likening the task to a game they had played many times in their youth.

Compensatory Motion

Significant (p<0.001, Mann-Whitney U test) reduction in motion of chest, upper arm, and lower arm during use - 42.7% less than the control group.

Task Load

Reduction in median mental demand (MD), physical demand (PD), significant (p<0.05, Mann-Whitney U test) reduction in frustration (Fr), and significant (p<0.05, Mann-Whitney U test) increase in perceived performance (Pe) compared to the humanoid group.

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