Closed-loop neuromuscular electrical stimulation using feedforward-feedback control and textile electrodes to...

Area of Science:

• Biomedical Engineering
• Rehabilitation Technology
• Neuroprosthetics

Background:

• Transcutaneous neuromuscular electrical stimulation (NMES) is used in physical rehabilitation and brain-computer interfaces for movement restoration in paralyzed individuals.
• Variable muscle responses to NMES can cause significant fluctuations in grasp force over time.
• Developing methods to regulate individual finger forces is crucial for functional movement in paralyzed limbs.

Purpose of the Study:

• To develop and assess closed-loop control methods for regulating individual finger forces.
• To integrate these methods with custom textile-based electrodes into a lightweight, wearable device.
• To evaluate the device's effectiveness in paralyzed study participants.

Main Methods:

• A textile-based electrode sleeve was co-developed by the study team and Myant, Corp.
• A feedforward-feedback control structure was designed and implemented for precise finger force maintenance.
• The system was evaluated in three able-bodied participants and two participants with quadriplegia.

Main Results:

• Neuromuscular electrical stimulation successfully evoked individual finger movements and functional grasping.
• Closed-loop control achieved accurate steady-state performance (less than 15% error) for individual finger contact force.
• The system demonstrated a settling time of 0.67 seconds (SD = 0.42 seconds) in a participant with quadriplegia.

Conclusions:

• Textile-based electrodes are a feasible alternative to conventional electrodes for NMES applications.
• The developed closed-loop system accurately controls individual finger flexion force.
• This technology presents a viable solution for grasp force regulation in individuals with quadriplegia.