Earable Ω (OMEGA): A Novel Clenching Interface Using Ear Canal Sensing for Human Metacarpophalangeal Joint Control by...

Area of Science:

• Biomedical Engineering
• Neuroscience
• Rehabilitation Technology

Background:

• Functional electrical stimulation (FES) requires mouth-free interfaces for individuals with spinal cord injuries.
• A novel earphone-type ear canal movement sensor system was developed for controlling the human metacarpophalangeal (MP) joint.

Purpose of the Study:

• To develop and evaluate a novel FES system for MP joint control using ear canal movement.
• To investigate the system's capability in controlling both joint angle and joint stiffness.

Main Methods:

• The FES system utilized equilibrium point and stiffness control signals (electrical agonist-antagonist ratio and sum).
• Joint angle was measured using an angle sensor.
• Joint stiffness was identified using system identification with a robot arm's external force.
• Experiments involved six and five human subjects for angle and stiffness control, respectively.

Main Results:

• Successful control of MP joint angle was achieved in three subjects, with observed hysteresis and delay.
• Control was less effective in subjects experiencing hyperextension, indicating calibration issues and joint characteristic changes.
• Joint stiffness increased with clenching amplitude in five subjects, and viscosity control was demonstrated.

Conclusions:

• The developed ear canal sensor system demonstrates potential for controlling both MP joint angle and stiffness.
• Future research will focus on simultaneous control of equilibrium point and stiffness for enhanced FES applications.