A Subject-Driven Arm Exoskeleton to Support Daily Life Activities

In the field of assistive technologies, the possibility to maximally exploit the residual capabilities of the user to increase the independence of persons with disabilities is a really promising approach. This prospective was the starting point of the European project MUNDUS that developed a customizable and modular system for recovering direct interaction capabilities of severely motor impaired people based on arm reaching and hand functions. The present work provides a quantitative evaluation of the simplest configuration of the MUNDUS system on three neurological patients. The apparatus consisted of a lightweight passive arm exoskeleton for weight relief, equipped with electromagnetic brakes for locking each degree of freedom. The user could autonomously activate and deactivate the brakes through a pre-defined contraction of a muscle of the contralateral arm. The subjects tested the system in a 3-day session. Each day, they were asked to execute four tasks: drinking, touching the left shoulder, touching the left hand, and pressing a button. A group of healthy volunteers were also involved in the trials to define normality ranges. Smoothness and straightness of the wrist trajectories were assessed. The usability of the system was also evaluated using the System Usability Scale (SUS). All subject were able to execute all the required tasks and to autonomously control the brakes from the first day, suggesting that no training was needed to learn how to use the system. In terms of performance over days, one subject’s trajectories were more rectilinear and more smooth after the first day, one subject worsened some kinematic parameters on the third day and one subject did not show any significant differences. In terms of usability, all subjects showed a good satisfaction with the system (SUS > 90/100) and would like to use the system in their daily life.