Robotically adjustable kinematics in a wrist-driven orthosis eases grasping across tasks

TL;DR

This study demonstrates that robotic assistance enabling flexible wrist postures in a wrist-driven orthosis improves grasping ease, versatility, and user comfort for individuals with spinal cord injury, potentially enhancing long-term device adoption.

Contribution

It introduces a robotic motor assistance approach that allows adaptable wrist postures, reducing task difficulty and increasing natural movement in assistive grasping devices.

Findings

Robotic assistance reduces perceived exertion during grasping.

Flexible wrist postures improve task versatility.

Enhanced user comfort promotes device usability.

Abstract

Without finger function, people with C5-7 spinal cord injury (SCI) regularly utilize wrist extension to passively close the fingers and thumb together for grasping. Wearable assistive grasping devices often focus on this familiar wrist-driven technique to provide additional support and amplify grasp force. Despite recent research advances in modernizing these tools, people with SCI often abandon such wearable assistive devices in the long term. We suspect that the wrist constraints imposed by such devices generate undesirable reach and grasp kinematics. Here we show that using continuous robotic motor assistance to give users more adaptability in their wrist posture prior to wrist-driven grasping reduces task difficulty and perceived exertion. Our results demonstrate that more free wrist mobility allows users to select comfortable and natural postures depending on task needs, which improves the versatility of the assistive grasping device for easier use across different hand poses in the arm's workspace. This behavior holds the potential to improve ease of use and desirability of future device designs through new modes of combining both body-power and robotic automation.