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  4. Feedback control of arm movements using Neuro-Muscular Electrical Stimulation (NMES) combined with a lockable, passive exoskeleton for gravity compensation

Feedback control of arm movements using Neuro-Muscular Electrical Stimulation (NMES) combined with a lockable, passive exoskeleton for gravity compensation

Frontiers in Neuroscience, 2014 · DOI: 10.3389/fnins.2014.00262 · Published: September 2, 2014

Assistive TechnologyNeurologyBiomedical

Simple Explanation

This study focuses on developing a feedback control system for Neuro-Muscular Electrical Stimulation (NMES) to help people with severe arm and shoulder weakness perform reaching movements. The system uses NMES to stimulate the deltoids and biceps, combined with a passive exoskeleton that supports the arm and can be locked in place. An eye-tracking system allows the user to select target positions, and a computer system controls the NMES to move the arm to the desired location.

Study Duration
Not specified
Participants
Five healthy subjects (three female and two male), aged 29–40 years
Evidence Level
Not specified

Key Findings

  • 1
    The control system was able to perform a drinking task in all five healthy subjects, who remained passive during the movements.
  • 2
    The average hand positioning error was less than five centimeters.
  • 3
    The average time to complete the drinking task was 71 seconds.

Research Summary

This study presents a feedback-controlled arm neuroprosthesis for individuals with limited arm and shoulder function, combining NMES with a passive exoskeleton for gravity compensation. The system uses an eye-tracking interface for target selection and a real-time controller to manage NMES and exoskeleton locking, enabling sequential joint angle control. Validation with healthy subjects performing a drinking task demonstrated successful task completion with reasonable accuracy and time, suggesting potential for assisting daily life activities.

Practical Implications

Assistive Technology

The developed system could provide a means for individuals with high-level spinal cord injuries to regain some independence in performing daily life activities.

NMES Control

The feedback control strategy offers a robust and adaptable method for managing NMES, compensating for muscle fatigue and individual variability.

Hybrid Exoskeleton Systems

The integration of NMES with a passive exoskeleton demonstrates a promising approach for reducing the demands on muscle stimulation and improving functional outcomes.

Study Limitations

  • 1
    Limited braking torque of the exoskeleton can cause unwanted slipping.
  • 2
    Elbow extension and shoulder flexion are only gravity-induced.
  • 3
    System movements are not very physiological or time optimal.

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