肌电调制结合迭代学习控制的足下垂FES系统

FES system for foot drop based on EMG modulation combined with iterative learning control

足下垂是指由于神经控制功能障碍导致踝关节无法产生背屈以致足尖上抬不完全或不能的现象。功能性电刺激(FES)作为纠正足下垂步态的治疗方法,通过低频脉冲刺激胫骨前肌引起肌肉收缩,使踝关节产生背屈动作,达到矫正足下垂的目的。本文提出了基于肌电(EMG)调制和迭代学习控制(ILC)的FES输出强度调制方法,利用小腿角速度信号通过动态BP神经网络预测健康步态胫骨前肌肌电信号,以脚尖俯仰角作为反馈信号通过ILC输出参考肌电信号,与神经网络预测的肌电信号加权平均得到修正后的肌电信号,最后利用肌肉激活特性调制FES输出。实验表明开环肌电调制模式下的脚尖俯仰角仅有17°左右,而在闭环调制模式下,脚尖俯仰角最大角度达到了21°左右。本文设计的FES控制系统可以帮助足下垂患者进行康复训练。

Foot drop is the phenomenon that ankle joint cannot produce dorsiflexion and the toe lifting is incomplete or impossible due to nerve control dysfunction.The functional electrical stimulation(FES)is used as a treatment method to correct foot drop gait,which uses low-frequency pulse to stimulate tibialis anterior to cause muscle contraction and dorsiflexion of ankle joint.The FES output intensity modulation method based on EMG modulation and iterative learning control(ILC)is proposed in this article.The angular velocity signal of the lower leg is used to predict the EMG of tibialis anterior in healthy gait through the dynamic BP neural network,and the toe pitch is used as feedback signal to output the reference EMG through ILC.The reference EMG and the EMG predicted by neural network are weighted-average to obtain the modified EMG.Finally,the FES output is modulated by the muscle activation characteristics.The experimental results show that the toe pitch angle in open-loop EMG modulation mode is only about 17°.Through the closed-loop modulation mode,the maximum toe pitch angle is about 21°.By analyzing experimental data.It can be concluded that the system can help patients with foot drop to carry out rehabilitation training.