Design and Characterization of Vibrotactile Feedback with Elbow Exosuit Assistance for Directional Guidance

Soft exosuits for upper-limb rehabilitation offer compliance and adaptability but lack the inherent trajectory guidance of rigid exoskeletons. Vibrotactile feedback is a promising approach to provide directional cues during movement execution. However, its effective use requires a systematic characterization of perceptual discriminability across localized haptic stimuli. This work presents the design and experimental characterization of a vibrotactile feedback system composed of eight coin vibration motors integrated into the upper-arm and forearm modules of a soft elbow exosuit. 14 participants performed vibrotactile localization tasks under different vibration parameters and assistance conditions, while perceptual accuracy and subjective metrics were recorded. Results show that haptic cues were generally distinguishable by location, with higher accuracy on the upper-arm and structured misclassifications on the forearm. In addition, exosuit assistance exerted a limited and condition-independent effect on perceptual accuracy. Subjective assessments indicated good clarity, comfort, and confidence in stimulus interpretation, without an increase in perceived workload under assistance. These findings provide design insights for the integration of vibrotactile feedback in compliant rehabilitation devices and support the use of haptic cues for intuitive guidance during rehabilitation sessions.