Mechanical design of RiceWrist-S: A forearm-wrist exoskeleton for stroke and spinal cord injury rehabilitation

Robotic rehabilitation of individuals with neurological lesions from stroke or spinal cord injuries is promising in that robots can provide intensive therapy and enable quantitative and objective assessment of motor impairment. Robotic devices for the upper extremity have primarily focused on the proximal joints, with only a few devices designed specifically for forearm and wrist rehabilitation, which is critical for the restoration of independence in activities of daily living. Previous robotic systems have neglected degrees-of-freedom at the wrist, or have offered limited range of motion or torque output capability. In this paper, we present the kinematic design of a serial mechanism, the RiceWrist-S, for forearm and wrist rehabilitation, and compare its range of motion and torque output capabilities to a previously reported parallel mechanism and to requirements developed from assessment of daily activities. The RiceWrist-S design meets or exceeds targets for range of motion and torque in all degrees of freedom.