FES-Induced Torque Prediction with Evoked EMG Sensing for Muscle Fatigue Tracking

Qin Zhang (1, 2) , Mitsuhiro Hayashibe (1) , Philippe Fraisse (1) , David Guiraud (1, 2)

1 DEMAR - Artificial movement and gait restoration
2 LIRMM - Laboratoire d'Informatique de Robotique et de Microélectronique de Montpellier

This study investigates a torque estimation method for muscle fatigue tracking, using stimulus evoked electromyography (eEMG) in the context of a functional electrical stimulation (FES) rehabilitation system. Although FES is able to effectively restore motor function in spinal cord injured (SCI) individuals, its application is inevitably restricted by muscle fatigue. In addition, the sensory feedback indicating fatigue is missing in such patients. Therefore, torque estimation is essential to provide feedback or feedforward signal for adaptive FES control. In this work, a fatigue-inducing protocol is conducted on five SCI subjects via transcutaneous electrodes under isometric condition, and eEMG signals are collected by surface electrodes. A myoelectrical mechanical muscle model based on the Hammerstein structure with eEMG as model input is employed to capture muscle contraction dynamics. It is demonstrated that the correlation between eEMG and torque is time-varying during muscle fatigue. Compared to conventional fixed-parameter models, the adaptedparameter model shows better torque prediction performance in fatiguing muscles. It motivates us to use a Kalman filter with forgetting factor for estimating the time-varying parameters and for tracking muscle fatigue. The assessment with experimental data reveals that the identified eEMG-to-torque model properly predicts fatiguing muscle behavior. Furthermore, the performance of the time-varying parameter estimation is efficient, suggesting that real-time tracking is feasible with a Kalman filter and driven by eEMG sensing in the application of FES.

Mots clés: Torque Prediction; Muscle Fatigue Tracking; Kalman Filter with Forgetting Factor; Functional Electrical Stimulation (FES).; Functional Electrical Stimulation (FES); Evoked Electromyography (eEMG)

Domaines: Biomécanique [physics.med-ph]; Biomécanique [physics.med-ph]; Robotique [cs.RO]; Ingénierie biomédicale

Qin Zhang, Mitsuhiro Hayashibe, Philippe Fraisse, David Guiraud. FES-Induced Torque Prediction with Evoked EMG Sensing for Muscle Fatigue Tracking. IEEE/ASME Transactions on Mechatronics, 2011, 16(5), pp.816 - 826. ⟨10.1109/TMECH.2011.2160809⟩. ⟨lirmm-00604670⟩