Planar Robotic Systems for Upper-Limb Post-Stroke Rehabilitation

Rehabilitation is the only way to promote recovery of lost function in post-stroke hemiplegic subjects, leading to independence and early reintegration into social and domestic life. In particular, upper limb rehabilitation is fundamental to regain ability in Activities of Daily Living (ADLs). Robot-aided rehabilitation is an emerging field seeking to employ leading-edge robotic systems to increase patient recovery in the rehabilitation treatment. Even though the effectiveness of robotic therapy is still being discussed, the use of robotic devices can increase therapists’ efficiency by alleviating the labor-intensive aspects of physical rehabilitation, and can produce a reduction in treatment costs. This paper presents a comparison between different planar robotic devices designed for upper-limb rehabilitation in chronic patients. A planar configuration of the workspace leads to straightforward mechanical and control system design, and allows to define very simple and understandable treatment exercises. Also, the graphical user interface becomes very intuitive for the patient, and a set of Cartesian-based measures of the patient’s performance can be defined easily. In the paper, SCARA (Selective Compliance Assembly Robot Arm) robots such as the MIT-Manus, Cartesian robots and cable-driven robots are considered and compared in terms of inertial properties and force exertion capabilities. Two cable-driven devices, designed at the Robotics Lab of the Department if Innovation In Mechanics and Management, University of Padua, Italy, are presented for the first time. The first robot employs four driven cables to produce a planar force on the end-effector, whereas the second one is based on a three-cable configuration plus a linear actuator to obtain better overall robot performance.