Forefeel the Move: Investigating Proprioceptive Feedback for Communicating Imminent Motions of Body-actuating Systems

Paper Title

Forefeel the Move: Investigating Proprioceptive Feedback for Communicating Imminent Motions of Body-actuating Systems

Publication Info

• Topic area: Proprioceptive feedback for intent communication in body-actuating systems.
• Keywords: Proprioceptive feedback, body-actuating systems, motion intent, exoskeletons, haptic feedback, human-computer interaction, interpretability, mixed-initiative systems, motion guidance, adaptive feedback.

Background and Problem

• Problem / challenge: Unexpected body actuation by autonomous systems can surprise users, pose safety risks, and conflict with user intentions. Current methods lack a principled understanding of how to effectively communicate motion intent in body-actuating systems.
• Significance: Communicating motion intent can help users anticipate system actions, assess their appropriateness, and intervene if needed, preserving a sense of control and improving safety and collaboration.
• Motivation and related work: Prior work has explored visual, auditory, and haptic feedback for intent communication in robots and autonomous systems, but proprioceptive feedback—aligned with the natural movement of the body—remains underexplored. This paper addresses this gap by investigating proprioceptive cues to convey motion intent in body-actuating systems.

Solution

• Proposed approach: Proprioceptive feedback to communicate motion intent directly to the affected body part, using cues that either interrupt or augment user motion.
• Novelty:
  1. Introduction of proprioceptive feedback as a channel for conveying motion intent in body-actuating systems.
  2. Design of interpretable proprioceptive cues for three motion properties: onset, direction, and target.
  3. Implementation and evaluation of these cues in an elbow exoskeleton.
  4. Analysis of trade-offs between response time and interpretation accuracy, and exploration of user preferences and affective dimensions.
• Procedure and key techniques:
  1. Design of proprioceptive cues for one-degree-of-freedom (DoF) hinge joints, focusing on flexion and extension.
  2. Implementation of cues in an elbow exoskeleton with calibrated parameters for torque, speed, and displacement.
  3. User study with 12 participants to evaluate detection accuracy, response time, interpretation accuracy, and user preferences for each cue type.

Results

• Concrete findings:
  • All cues achieved high detection accuracy (>90%) and confidence.
  • Interruptive cues were fastest to detect (response time: 0.8–2.5 s) but less accurate for interpreting complex information (e.g., direction: 62.5% accuracy).
  • Augmenting cues (e.g., pull) were slower (response time: 1.2–3.5 s) but yielded higher interpretation accuracy (e.g., target: 83.3% accuracy).
• Advantage over baselines:
  • Proprioceptive cues offer integrated, localized feedback without requiring additional sensory channels, achieving competitive detection accuracy and response times compared to other modalities like vibrotactile or visual feedback.
• Experiments / evaluation:
  • Mixed-methods study with 12 participants using an elbow exoskeleton.
  • Tasks included detecting motion onset, interpreting direction, and interpreting target (direction + extent).
  • Quantitative metrics: detection accuracy, response time, interpretation accuracy, and confidence.
  • Qualitative insights: user preferences, perceived urgency, and affective dimensions of cues.
• Limitations and future work:
  • Limited to 1 DoF hinge joints and an elbow exoskeleton; future work should explore other body parts, systems, and DoFs.
  • Focused on three motion properties; additional properties like force or speed could be investigated.
  • Need for larger, more diverse samples and real-world contexts.
  • Potential for combining proprioceptive feedback with other modalities for enhanced communication.

Summary

This paper introduces proprioceptive feedback as a method for communicating motion intent in body-actuating systems, focusing on three properties: motion onset, direction, and target. Proprioceptive cues were implemented in an elbow exoskeleton and evaluated in a user study. Results show that interruptive cues are faster but less accurate, while augmenting cues are slower but more accurate and preferred by users. The findings highlight a trade-off between response time and interpretation accuracy, suggesting a layered design approach combining different cue types. Future work should explore adaptability, personalization, and integration with other modalities to enhance the interpretability and usability of body-actuating systems.