Real-time closed-loop FES control of muscle activation with evoked EMG feedback

Abstract

Functional electrical stimulation (FES) is a useful technique for restoring motor functions for spinal cord injured (SCI) patients. Muscle contractions can be artificially driven through delivery of electrical pulses to impaired muscles, and the electrical activity of contracted muscles under stimulus recorded by electromyography (EMG) is called M-wave. The FES-induced muscle activation which is represented by evoked EMG recordings can indicate the muscle state. Accurate control of muscle activation level by FES is the preliminary step for achieving more complicated FES control tasks. This paper proposes a real-time FES system for control of muscle activation by online modulating pulse width of stimulus. The excitation muscle dynamics is modelled by Hammerstain system with stimulus pulse width and eEMG as input and output respectively. The model predictive control strategy is adopted to compute the pulse width command sent to the Vivaltis wireless stimulator. Four reference muscle activation patterns are provided to test and validate the real-time closed-loop FES control system. Realtime control results on one able-bodied subject show promising control performances.

sEMG Bias-Driven Functional Electrical Stimulation System for Upper-Limb Stroke Rehabilitation

“…That is to say, the EMG signals from the unaffected forearm were used as reference to evaluate the mirror symmetric muscle in the affected side forearm. Thus, different from the closed-loop FES studied in [28], [38], [39], which concentrated on the FES control strategies based on the FES-induced EMG rather than sensing the patients' neuromuscular pathological state, the FES in this study was driven by the EMG bias, so that it could not only avoid the unnecessary stimulation on the unaffected nerves and muscles to reduce the sufferings of users but also alleviate muscle fatigue compared to the cycling fixed intensity FES used in clinical. Furthermore, the designed system had advantages of wireless communication, multiple channels, portable size and real-time capability.…”

Advances in neuroprosthetic management of foot drop: a review

“…With this information, it modulates the pulse width to follow a desired trajectory and the eEMG model is updated. The system was tested on able-bodied subjects and SCI patients, and the results verify its feasibility and efficiency [75][76][77][78].…”

Evoked Electromyographically Controlled Electrical Stimulation

“…This facilitates the prediction of the muscle response and then the system can respond to time-variant muscle state changes toward muscle-response-aware FES control. It was further implemented combined with a wireless portable stimulator (Toussaint et al, 2010 ) to achieve real-time FES control (Li et al, 2015 ).…”

“…A real-time implementation of the predictive model controller for online control of muscle activation is as follows (Li et al, 2015 ): The reference muscle activation trajectory is prepared before beginning estimation and control; Trapezoidal shape pulse width stimulation at different amplitude levels is tested while recording the eEMG to personalize the model regarding the relationship between the pulse width and MAV of eEMG via Kalman filter; After the identification phase ends, the FES system goes into control mode. The stimulator is driven by a predictive controller to modulate the pulse width to track the desired muscle activation trajectory while the stimulation-to-eEMG model is being updated to correspond to the time-variant properties.…”