The Study Of Surface Electromyography Signal Sensitivity Based On Muscle Activity Segment Detection

In the muscle forces are divided into static contraction and dynamic contraction.In the process of muscle fatigue with static contraction,the conduction velocity will decrease and shift the frequency spectrum to low frequency.For static contraction,the whole contraction process is basically constant,and the surface electromyogram signal can be calculated according to the fixed length segment to calculate the relevant parameters.While in the dynamic contraction,the muscle force is constantly changing.Just like the dynamic elbow flexion and extension in life,in the process of muscle dynamic contraction fatigue,there are also changes in muscle shape,electrode position,movement difference in dynamic contraction.These changes will affect the rule of characteristic parameters,which makes it difficult to evaluate the fatigue effectiveness of muscle.To explore muscle fatigue,this paper carries out the analysis of muscle fatigue.Firstly,the time-axis partition method of muscle dynamic contraction is analyzed to analyze the time-domain and frequency-domain myoelectric characteristic parameters for fatigue degree.Then,the contraction-region partition method is proposed.The purpose of this method is to detect muscle fatigue according to the poor sensitivity of the time-axis partition method.The innovation of this method is that the shape of the muscle,the position of the electrode and the standard of movement are taken into account in the dynamic contraction of the muscle.The above change will affect the rule characteristic parameters.Therefore,the time-axis partition method is not used as the basis for dividing electromyoelectric data,but the contraction-region partition method.The method is to use single parameter(double parameters)combined with single threshold(double thresholds)to obtain the starting point and the final point of the contraction-region of surface myoelectric signal to distinguish the dynamic and static contraction regions.The sensitivity of muscle fatigue is characterized by the sensitivity fluctuation ratio(SVR)in the dynamic contraction region of muscles.The results show that the sensitivity of the contraction-region partition method to fatigue response is higher than the time-axis partition method.This method can better characterize the process of muscle fatigue.This method amplifies the fine characteristic information of surface electromyography in detecting muscle fatigue.Furthermore,Aiming at the high lost detection rate of traditional methods on continuous segmentation surface electromyography signals and the problem of manually setting threshold,integrated electromyography and adaptive threshold is proposed to detect muscle contraction region.The innovations are to solve the traditional parameters waveform fluctuated,the poor smoothness,the double threshold value manually setting in advance,the traditional method of measuring each subjects to manually set the threshold.The traditional parameters includes subband spectrum entropy value,cepstrum value,energy value,zero crossing rate value,fractal dimension value and so on.Through comparison and analysis,it is proved that the mistake rate of detecting muscle contraction area based on integrated EMG and adaptive threshold is lower.The smoothness of the parameter waveform is better,the change regularity is better,the fluctuation is less.At the same time,the problem of manual setting double threshold is solved,and it is self-adaptive.In addition,duing to its adaptive,it is applicable and practical for different subjects.It is different from traditional methods to reset the threshold manually for each subject.Finally,the rehabilitation evaluation system was designed based on time-domain,frequency-domain and parameter model analysis methods.The experimental results show that the system has a better effect of rehabilitation evaluation and further improves the application value.