Elbow Angle Guidance System Based on Surface Haptic Sensations Elicited by Lightweight Wearable Fabric Actuator

Traditional wearable haptic devices often rely on rigid exoskeletons that can be heavy, uncomfortable, and restrictive to natural human movement. This paper investigates whether a soft, fabric-based actuator system can provide intuitive, real-time guidance for elbow joint angles without interfering with the wearer's physical activity.

The authors designed a lightweight fabric sleeve integrated with two McKibben-type artificial muscles. These muscles are pneumatically controlled to elicit surface haptic sensations on the skin near the biceps and triceps, signaling the user to flex or extend their elbow. The system uses an optical motion capture setup to track the current elbow angle and adjusts the pneumatic pressure in real time based on the difference between the current and target angles. The control algorithm incorporates Weber-Fechner’s law to map pneumatic pressure to perceived haptic intensity, ensuring that the guidance is intuitive.

In experiments with six human participants, the proposed system successfully guided users to target elbow angles with significantly lower error rates than random chance. The device was shown to be non-restrictive, as the artificial muscles did not force the elbow into position but rather provided a sensory cue that the user followed voluntarily. The results suggest that this soft, textile-based approach is a viable alternative to rigid exoskeletons for applications requiring lightweight, non-intrusive joint guidance.

This research contributes to the development of soft robotics in rehabilitation and teleoperation. By prioritizing user comfort and non-interference, the system addresses key barriers to the adoption of wearable haptic technology. The ability to guide joint movement through subtle surface sensations rather than mechanical force could lead to more user-friendly assistive devices that are easier to wear for extended periods.

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