Embedded Files
Overview
Overview
The twisting motion required to use a screwdriver is very hard to replicate with a humanoid prosthetic hand. The intricate coordination of multiple fingers to contact and rotate an object is impossible to achieve, meaning tools such as these must be held awkwardly in the hand and rotated either by the wrist or the user's own arm. Our twisting device greatly simplifies this, using a gear train to produce twisting motion and a removable holder to accommodate multiple types of screwdriver.
Design
Design
Schematic diagram, annotated with key components.
Real terminal device with screwdriver mounted (left) and being used to screw a cross-head screw (right).
Mechanical Design
Mechanical Design
A simple gear train is used to transmit motor rotation to screwdriver rotation.
A removable flexible TPU piece is used to hold the screwdriver in place during use.
Control
Control
Two electrodes reading muscle activity.
In one direction, tensing rotates the screwdriver at a fixed speed.
In the other direction, tensing rotates the screwdriver at a fixed speed in the opposite direction.
Testing
Testing
Experiment - Tightening Screws
Experiment - Tightening Screws
Used to test screwing performance and ease of screwdriver changeover.
Users must screw in three different types of screws.
Performance metric: completion time.
Repeated 3 times.
Results
Results
Task Performance
Task Performance
Completion time using the Twisting Device was considerably quicker (p<0.001, Mann-Whitney U test) than the humanoid hand: 278.6 seconds vs 701.2 seconds.
Participants with upper limb difference performed similarly to group results of participants without upper limb difference. Participant 1 was a bilateral amputee, and had assistance with screwdriver changes, resulting in faster completion times.
Compensatory Motion
Compensatory Motion
Significant reduction in motion of chest, upper arm, and lower arm (p<0.05, p<0.001, p<0.05, respectively, Mann-Whitney U test) during use.
Participant 1 received assistance with screwdriver changes, reducing body motion.
Task Load
Task Load
Reduction in median mental demand (MD), physical demand (PD), significant reduction in frustration (Fr, p<0.05, Mann-Whitney U test), and significant increase in perceived performance (Pe, p<0.01, Mann-Whitney U test) compared to the humanoid group.
Participant 1 received assistance with screwdriver changes, reducing task load.
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