Enhancing Motor Synchrony in Rhythmic Dyadic Tasks through Portable Elbow Exoskeletons
Emanuele Peperoni, Stefano Laszlo Capitani, Lorenzo Grazi, Michele Francesco Penna, Lorenzo Amato, Filippo Dell'Agnello, Andrea Baldoni, Domenico Formica, Marc Leman, Nicola Vitiello, Simona Crea, Emilio Trigili
AI summary
Problem
Human-human synchronization in dyadic tasks typically relies on visual or auditory cues, leaving a gap in portable, joint-level haptic coupling mechanisms for Human-Robot-Human interaction.
Approach
Two identical, lightweight series-elastic actuator elbow exoskeletons were used to render bidirectional or unidirectional torque feedback during a visually and acoustically isolated rhythmic tapping task.
Key results
- Bench-tested residual torque below 0.2 Nm and bandwidth exceeding 6 Hz
- 50% reduction in joint trajectory error with haptic feedback
- Relative phase error maintained below 60% during dyadic interaction
- Validated bidirectional and unidirectional haptic coupling paradigms
Why it matters
This portable haptic interface enables precise motor synchronization without sensory cues, advancing applications in rehabilitation, collaborative tasks, and skill training.
Abstract
Synchrony is a cornerstone for the successful physical interaction between humans while cooperating or competing to- wards a goal and is achieved by correct and smooth information ex- change between subjects. Recently, Human-Robot-Human (HRH) interaction arose as an emerging paradigm for improving motor control in collaborative and dyadic motor tasks. Among the robotic solutions explored for agent coupling, exoskeletons are powerful tools for exerting torque and force feedback at the joint level. In this work, two identical torque-controlled elbow exoskeletons were used in dyadic interaction, to provide haptic feedback and improve synchrony between two individuals performing a tapping task. Each exoskeleton is lightweight and compact, weighing 0.8 kg on the arm. 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 zero, and a bandwidth higher than 6 Hz, thus achieving adequate performance for applications in HRH scenarios. In 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; the relative phase error was lower than 60%. The results of this study suggest that exoskeletons can enhance synchrony in HRH interactions, being potentially useful in rehabilitation train- ing, collaborative industrial tasks or sport and music learning.