Design of a robotic device for assessment and rehabilitation of hand sensory function

This paper presents the design and implementation of the Robotic Sensory Trainer, a robotic interface for assessment and therapy of hand sensory function. The device can provide three types of well controlled stimuli: (i) angular displacement at the metacarpophalangeal (MCP) joint using a remote-center-of-motion double-parallelogram structure, (ii) vibration stimuli at the fingertip, proximal phalange and palm, and (iii) pressure at the fingertip, while recording position, interaction force and feedback from the user over a touch screen. These stimuli offer a novel platform to investigate sensory perception in healthy subjects and patients with sensory impairments, with the potential to assess deficits and actively train detection of specific sensory cues in a standardized manner. A preliminary study with eight healthy subjects demonstrates the feasibility of using the Robotic Sensory Trainer to assess the sensory perception threshold in MCP angular position. An average just noticeable difference (JND) in the MCP joint angle of 2.46° (14.47%) was found, which is in agreement with previous perception studies.