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Improving Muscle Force Distribution Model Using Reflex Excitation: Toward a Model-Based Exoskeleton Torque

Mojtaba Rayati, Rezvan Nasiri, Majid Nili Ahmadabadi

    IEEE Transactions on Neural Systems and Rehabilitation Engineering : a Publication of the IEEE Engineering in Medicine and Biology Society
    |April 4, 2023
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    Summary
    This summary is machine-generated.

    This study introduces an improved neuromuscular model that accounts for reflex excitation, better explaining biological torque limitations in exoskeleton assistance. The model enhances exoskeleton torque optimization by minimizing metabolic rate.

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    Area of Science:

    • Biomechanics
    • Neuroscience
    • Robotics

    Background:

    • Existing models inadequately explain the discrepancy between biological torque and optimized assistive torque.
    • Reflex excitation, a nonvoluntary neuromuscular mechanism, is often overlooked in torque distribution models.

    Purpose of the Study:

    • To improve existing muscle force distribution models by incorporating reflex excitation.
    • To develop a framework for optimizing exoskeleton torque profiles based on metabolic rate minimization.
    • To test the hypothesis that reflexive excitation significantly restricts biological torque compensation.

    Main Methods:

    • Utilized passive and active ankle exoskeleton datasets for model validation.
    • Identified model parameters, specifically reflex gains, using passive exoskeleton data.
    • Optimized exoskeleton torque profiles using the validated model for active exoskeleton experiments.

    Main Results:

    • The improved model explains 58% of uncompensable biological torque, a significant increase from the 17% explained by existing models.
    • This finding supports the hypothesis that nonvoluntary reflex excitation plays a crucial role in limiting biological torque compensation.
    • The model also shows potential for characterizing co-activation in antagonistic muscles.

    Conclusions:

    • Reflex excitation is a critical factor in understanding biological torque limitations during exoskeleton use.
    • The proposed model offers a more accurate representation of the neuromuscular system for exoskeleton torque optimization.
    • Further research is needed to explain the remaining 16% of uncompensable torque.