Application of robotic manipulability indices to evaluate thumb performance during smartphone touch operations

Abstract

This study examined whether manipulability during smartphone thumb-based touch operations could be predicted by the following robotic manipulability indices: the volume and direction of the ‘manipulability ellipsoid’ (MEd), both of which evaluate the influence of kinematics on manipulability. Limits of the thumb's range of motion were considered in the MEd to improve predictability. Thumb postures at 25 key target locations were measured in 16 subjects. Though there was no correlation between subjective evaluation and the volume of the MEd, high correlation was obtained when motion range limits were taken into account. These limits changed the size of the MEd and improved the accuracy of the manipulability evaluation. Movement directions associated with higher performance could also be predicted. In conclusion, robotic manipulability indices with motion range limits were considered to be useful measures for quantitatively evaluating human hand operations.

Abstract

Practitioner Summary: To examine the usefulness of robotic manipulability indices for quantitatively evaluating human hand operations, they were used to assess smartphone touch operations. The effectiveness of the robotic measure was improved by incorporating human movement characteristics into the index.

Keywords::

• manipulability
• kinematics
• workspace
• human interface
• thumb

Disclosure statement

No potential conflict of interest was reported by the author.