Enhancing Motor Synchrony in Rhythmic Dyadic Tasks through Portable Elbow Exoskeletons

Abstract

Synchrony is a cornerstone for the successful physical interaction between humans while cooperating or competing towards a goal and is achieved by correct and smooth information exchange between subjects. Recently, Human-Robot- Human (HRH) interaction arose as an emerging paradigm for improving motor control in collaborative and dyadic movement tasks. Among the robotic solutions explored for agent coupling, exoskeletons represent powerful tools for exerting torque and force feedback at the joint level. In this work, two identical torque-controlled elbow exoskeletons were used in the context of dyadic interaction, to provide haptic feedback and improve synchrony between two individuals performing a tapping task. Each exoskeleton is lightweight and compact, with a total weight of 0.8 kg on the arm and a volume of 360x80x80 𝒎𝒎𝟑. Bench tests to verify the performance of closed-loop torque control showed a residual torque below 0.2 Nm when the reference torque was set to null, and a bandwidth higher than 6 Hz, thus achieving adequate performance for applications in HRH scenarios. During human subjects’ experiments, the root-mean-squared error between the two users’ joint trajectories was 50% lower when users received haptic feedback compared to the condition without feedback; similarly, the relative phase error was lower than 60%. The results of this study suggest that exoskeletons can be used to enhance synchrony in HRH interactions, which could potentially be useful in rehabilitation training, collaborative industrial operations or sport and music learning.