CLEVERarm: A Lightweight and Compact Exoskeleton for Upper-Limb Rehabilitation

This letter presents the electromechanical design, system architecture, baseline control development, and the preliminary evaluation of a novel upper-limb exoskeleton, named CLEVERarm. The developed system can support the motions of inner shoulder, glenohumeral joint, elbow and wrist's pronation/supination and flexion/extension. Enhanced portability, design robustness, and ergonomic performance are chosen as the pillars of the design. These qualities are selected due to their importance for enabling exoskeletons' use outside the clinical and research setting. CLEVERarm's links are manufactured using carbonfiber-reinforced 3D-printed plastic to achieve a lightweight and compact design. For design robustness, minimizing maintenance requirements are taken into account in the selection and placement of actuation, sensing and controller components. Finally to realize an ergonomic interaction, inner shoulder motions are supported by a back-drivable motorized design, controlled by an impedance controller. This architecture enables accommodating natural variations in scapulohumeral rhythm among users. The performance of the developed exoskeleton is evaluated using experiments involving healthy subjects. It is shown that despite its lightweight, CLEVERarm is structurally stiff and supports a large subset of the healthy range of motion. Additionally, experimental results confirming the performance of the baseline controller are presented.