Hand Grip Force Enhancer Based on sEMG- Triggered Functional Electrical Stimulation

Stroke patients in the later stages of rehabilitation are always trapped in insufficient grip output, which brings obstacles to their daily manipulations. In order to improve not only the level of grip strength but also active participation of patients, an sEMG-triggered functional electrical stimulation(FES) system was designed. In this paper, hand grip force(HGF) plays a role of bridge to connect sEMG with FES. A Morlet wavelet transform based model was used for predicting the active HGF by sEMG signals, and the complex nonlinear relationship between electrical stimulation parameters and FES-induced HGF is represented as a fitted curve defined by means of experimental measurements. Four healthy subjects participated in the experiment to validate the proposed method. Two-channel sEMG signals captured from the flexor digitorum superficialis(FDS) and extensor digitorum(ED) were used to estimate HGF. The average result revealed the proposed estimation model had a excellent performance(NRMSE <; 0.092, ). When the trigger command was generated, FES was applied to the FDS and the effect of boosting of HGF is obvious. The study demonstrated its potential for grip force recovery training or as an auxiliary device for stroke patients.