Transition from mechanical arm to human arm with CAREX: A cable driven ARm EXoskeleton (CAREX) for neural rehabilitation

Rehabilitation robotic devices have been actively explored for training patients with impaired neural functions or assisting those with weak limbs due to aging or diseases. In recent years, the authors have proposed light-weight exoskeleton designs for the upper arm, in which rigid links of the exoskeleton are replaced by lightweight cuffs attached to the moving limb segments of the human arm. Cables, driven by motors, are routed through these cuffs to move the limb segments. However, a scientific limitation of a cable driven system is that cables can only pull but not push. Previously, the authors have demonstrated by experiments with CAREX mounted on a robotic arm that it is possible to achieve forces in all directions at the wrist. The goal of this paper is to demonstrate via experiments that CAREX is able to apply similar forces at the end-effector with healthy subjects in the device. In this research, CAREX was rigidly attached to an arm orthosis which can be tightly strapped on the human arm. The cable routing points were optimized for large “tensioned” workspace of the arm for typical Activities of Daily Living (ADLs). An orientation sensor was used to measure shoulder joint angles. Experiments are presented to validate the new sensor implementation and show the performance of CAREX on healthy subjects.