Real-time estimation of FES-induced joint torque with evoked EMG Application to spinal cord injured patients

Journal of NeuroEngineering and Rehabilitation, 2016 · DOI: 10.1186/s12984-016-0169-y · Published: June 14, 2016

Spinal Cord Injury Rehabilitation Biomedical

Simple Explanation

Functional electrical stimulation (FES) is a neuroprosthetic technique used to restore motor function in spinal cord injured (SCI) patients by delivering electrical pulses to paralyzed muscles. The electrical pulses induce muscle activity, which can be characterized by electromyography (EMG) signals. These signals can be used to predict the resulting joint torque. This paper proposes a wireless portable stimulator used for estimating/predicting joint torque based on real time processing of eEMG.

Study Duration

Not specified

Participants

3 able-bodied subjects and 3 SCI patients

Evidence Level

Not specified

Key Findings

1
Both Kalman filter and RNN approaches show clinically feasible results on estimation/prediction of joint torque with eEMG signals only.
2
RNN requires less computational requirement.
3
The prediction results of the 6 subjects are better with NARX-RNN than with Kalman filter.

Research Summary

This paper presents a real-time FES-induced torque estimation system using a wireless portable stimulator. Kalman filter and RNN are used online to identify and predict torque output based on eEMG recordings. Experiment validation on able-bodied subjects and SCI patients shows the promising performance of the proposed real-time FES system.

Practical Implications

Personalized Evaluation

The system allows for personalized quantitative evaluation of muscle response under FES, useful for clinical diagnostics.

Closed-Loop FES Control

The system can be used for the implementation of real-time closed-loop FES torque control.

Improved Portability

Getting rid of torque sensors will improve portability and mobility of ambulatory autonomous closed loop FES system.

Study Limitations

1
Estimators are needed to offer more patient-specific adjustment on SCI patients than on healthy ones.
2
The study focuses on isometric conditions, and non-isometric cases require measuring moment arm and estimating muscle force-length-velocity relation.
3
The system is targeted for early-middle fatigue stage.

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