Transparency Evaluation of SIDE Exoskeleton: A Preliminary Study for Haptic VR Training

Application of wearable robotic devices in training programs is gaining more and more interest. In the last few years, several training devices based on haptic and audiovisual stimuli have been developed to enhance training by stimulating proprioception. Transparency of these devices is a key parameter for the evaluation of their performance. In this study, we present the results of a transparency study of SIDE, a fully wearable 4-degree-of-freedom exoskeleton that provides haptic feedback to shoulder and elbow. The study examines transparency both kinematically and with respect to muscle activations using inertial sensors and surface electromyography, respectively. The study involved seven healthy subjects, who were asked to perform simple movements with their shoulder and elbow in two conditions (with and without an exoskeleton) and with three different masses. Our analysis, conducted using a repeated-measures ANOVA test, revealed that from a kinematic perspective, there were no observable differences between conditions. However, our findings showed greater muscle activation, especially for the anterior, middle, and posterior deltoids and the biceps brachii, when the exoskeleton was in use. At the conclusion of the experiment, subjective opinions of the participants were collected, revealing that they had not perceived any difference between the conditions. The results underscore the importance of a comprehensive evaluation of the transparency of these devices, coupling muscle activation and kinematic analysis of exoskeleton-human interaction.