Design of CASIA-ARM: A novel rehabilitation robot for upper limbs

The population of disabled stroke survivors is increasing sharply over the world, and robot-assisted training has been proved to be effective to help motor relearning and alleviate the shortage of physical therapists. This paper presents the design details of a novel upper limb rehabilitation robot named CASIA-ARM, which can assist poststroke patients to perform shoulder and elbow rehabilitation training in the horizontal plane, and provide both force and visual feedback to the patient: 1) A five-bar closed-chain structure is designed to realize a stiff and low-inertial mechanism. Workspace and singularity analysis is given, which guarantees that the workspace is large enough for upper limb moving and no singularity in the workspace. 2) Cable transmission, motor current controller and impedance control method guarantee the transparent and compliant interaction between the human and the robot. 3) Implementation examples of passive training based on position control and active training based on impedance control are presented in detail. 4) In order to evaluate the robot´s applicability and performance, examples of trajectory tracking and active reaching tasks are used in this study, and the preliminary test results are also given (tracking error: 0.86±0:42 mm, force control error: 1.41±0.79 N in the X direction, and 1.22±0.91 N in the Y direction).