Human body daily behavior myoelectricity feature selection approach based on feature class separability index
Technical field
The invention belongs to feature extraction fields, are related to a kind of human body daily behavior myoelectricity based on feature class separability index
Feature selection approach.
Background technique
EMG is the superposition of moving cell action potential over time and space in numerous muscle fibres.SEMG is superficial muscular
Comprehensive effect of the electric discharge behavior in skin surface on EMG and nerve cord.It can be divided into commonly used in the feature extracting method of EMG signal
Time domain approach, frequency domain method, time-frequency domain method.Time Domain Analysis is most species, the most common method, this is because time domain
Method is only based on signal amplitude, and algorithm is simple, and the complexity of feature extraction is small.Arief et al. [33] divides from time domain
Average absolute value (Mean Absolute Value, MAV), variance (Variance, VAR), Wilson's amplitude are analysed
(Willison Amplitude, WAMP), waveform length (Waveform Length, WL) and zero passage points (Zero
Crossing, ZC), it is intended to finding can make that feature complexity is minimum, dimension is less, the optimal method of separability, grind to be subsequent
Offer technical support is provided.Frequency domain method is mainly to be obtained by power spectral density, such as average frequency, median frequency etc..In EMG
In, frequency domain character is commonly used in the detection of muscular fatigue.Such as Song Haiyan is by extracting frequency of average power (Mean Power
Frequency, MPF), it show that its characteristic value is consistent with the subjective assessment of human-body fatigue, can be used for predicting fatigue.Time-frequency domain method
It is the combined method of time and frequency, the change frequency information at different time position can be characterized, provided largely about analysis
The non-stationary information of signal.Wavelet transformation (Wavelet Transform, WT) is the common method in time-frequency domain, is suitable for table
Show the short pulse in high-frequency signal or the long-time signal of speed variation.Wavelet package transforms (Wavelet Packet
Transform, WPT) be WT extension, can effectively eliminate high-frequency noise.However, WT is still very poor in high band, WPT lacks
Translation invariant property.Therefore, Xing et al. proposes a kind of new solution, using wavelet packet component energy construction feature to
Amount.Activity consciousness, especially daily routines monitoring and fall detection, as a basic subdomains of behavior perception, to needs
The daily routines of the elderly and weak person of help play an important role.If active health can be carried out according to patient muscle's motion intention
Refreshment is practiced, and the rehabilitation efficacy of patient can be improved.
Summary of the invention
In view of the deficiencies of the prior art, the present invention proposes a kind of human body daily behaviors based on feature class separability index
Myoelectricity feature selection approach.
The present invention studies the feature extraction of surface electromyogram signal and feature selecting, it is therefore an objective to determine surface myoelectric
Best features of the signal in number of storage tanks produced per day monitoring and fall detection.Firstly, acquire human body lower limbs activity in gastrocnemius,
Then this four road surfaces electromyography signal of tibialis anterior, vastus medials, musculus vastus lateralis calculates being averaged for 10 kinds of every road electromyography signals of extraction
Amplitude, variance, Wilson's amplitude, autoregressive coefficient, median frequency, frequency of average power, wavelet energy coefficient, wavelet-packet energy
Coefficient, fuzzy entropy, totally 10 myoelectricity features form myoelectricity feature pool to arrangement entropy, dynamic to static state movement, gait movement, static conversion
The three categories of work calculate separately respective feature class separability index (the Feature Class of 10 electromyography signal features
Separability index), select feature class separability index quiet higher than 0.6 myoelectricity feature composition from myoelectricity feature pool
State acts myoelectricity feature group, and myoelectricity feature composition gait of the feature class separability index higher than 0.5 acts myoelectricity feature group, feature
Myoelectricity feature composition static conversion of the class separability index higher than 0.2 acts myoelectricity feature group.
In order to achieve the goal above, the method for the present invention mainly comprises the steps that
It is total that step (1) acquires human body gastrocnemius, tibialis anterior, vastus medials, musculus vastus lateralis when human body does daily behavior movement
4 tunnel electromyography signals;Daily behavior movement includes static movement, gait movement, static conversion movement, static state movement includes station, sit,
It squats, lie;Gait movement includes that level land is walked, goes upstairs, goes downstairs, runs;Static conversion movement include station-seat, seat-stand, stand-
It squats, crouching-is stood, sat-lie, lie-and sits;
Step (2) extracts every road electromyography signal x that sample number is NiAverage amplitude MA,
Variance VAR,Wilson's amplitude WAMP,U (x) indicates rank
Jump function, and T is threshold value;Autoregressive coefficient AR;Median frequency MF,fiAnd hiRespectively frequency and frequency spectrum is strong
Degree;Frequency of average power MPF,P(fi) be basic point signal power spectrum;Wavelet energy coefficient EWT,FjIt is the coefficient of wavelet energy, K is jth layer decomposition coefficient, Wj,kIt is the kth of jth layer decomposition coefficient
A coefficient;Wavelet-packet energy coefficient EWP;Fuzzy entropy FE,WhereinM defines the dimension of data, DijIt is the similarity of two samples, r is DijMiddle finger
The width of number function, referred to as average similarity;Entropy PE is arranged,N refers to sample points, totally 10
A myoelectricity feature forms myoelectricity feature pool;
Step (3) refers to the static respective feature class separability of 10 electromyography signal features for acting calculating step 2 extraction
Mark selects myoelectricity feature composition static movement myoelectricity feature group of the feature class separability index J higher than 0.6;
Step (4) acts the respective feature class separability of 10 electromyography signal features that calculating step 2 is extracted to gait and refers to
Mark selects myoelectricity feature composition gait of the feature class separability index index J higher than 0.5 to act myoelectricity feature group;
Step (5), which acts the respective feature class of 10 electromyography signal features that calculating step 2 is extracted to static conversion, to be divided
Property index, select feature class separability index index J higher than 0.2 myoelectricity feature composition static conversion act myoelectricity feature group;
The feature class separability index of the electromyography signal feature specifically calculates as follows:
Equipped with electromyography signal training sample feature vector x1,x2,...xK, wherein KiIt is a to belong to classification ωi, i.e. KiFor the i-th class
Sample number, be denoted as Xi=x1 i,x2 i,...xKi i, i=1,2,3...C, C are total class number, and K is total number of samples,
Remember ωiThe myoelectricity mean vector of class is mi, have
The mean vector for remembering all class myoelectricity features is m, is had
Discrete matrix S between the respective class of electromyography signal featureBWith discrete matrix S in classW, formula is as follows:
Then tr (S is calculatedB),tr(Sw) respectively indicate matrix SBAnd SwMark, feature class separability index J obtains by following formula
It arrives:
The present invention has a characteristic that compared with the feature selecting algorithm of existing many electromyography signals
Since the present invention is extracted 10 kinds of features, if all using this 10 kinds of features to the movement of every class, it is multiple to will lead to algorithm
Miscellaneous degree increases significantly, and increases operation time.It can be utilized to greatest extent using this method of feature class separability index
Each feature not will cause the waste or redundancy of characteristic information, reduces dimension, greatly reduces the complexity of algorithm, make to classify
Effect is more preferable.
Detailed description of the invention
Fig. 1 is implementation flow chart of the invention;
Fig. 2 is the initial surface electromyography signal figure of 4 road signals of some daily behaviors;
Fig. 3 is the feature class separability index value of 15 kinds of features;
Fig. 4 is feature class separability index value and the calculating time of 15 kinds of features.
Specific embodiment
Elaborate with reference to the accompanying drawing to the embodiment of the present invention: the present embodiment before being with technical solution of the present invention
It puts and is implemented, the detailed implementation method and specific operation process are given, but protection scope of the present invention is not limited to down
The embodiment stated.
As shown in Figure 1, the present embodiment includes the following steps:
Step 1 acquires human body gastrocnemius, tibialis anterior, vastus medials, musculus vastus lateralis totally 4 when human body does daily behavior movement
Road electromyography signal;Daily behavior movement includes static movement, gait movement, static conversion movement, static state movement includes station, sit,
It squats, lie;Gait movement includes that level land is walked, goes upstairs, goes downstairs, runs;Static conversion movement include station-seat, seat-stand, stand-
It squats, crouching-is stood, sat-lie, lie-and sits.As shown in Figure 2, it is shown that the original electromyography signal of several behavior acts.
Step 2 extracts the average amplitude MA of every road electromyography signal, variance VAR, Wilson's amplitude WAMP, autoregressive coefficient
AR, median frequency MF, frequency of average power MPF, wavelet energy coefficient EWT, wavelet-packet energy coefficient EWP, fuzzy entropy FE, arrangement
Entropy PE, totally 10 myoelectricity features form myoelectricity feature pool;
Step 3 calculates separately the 10 of step 2 extraction to the three categories of static movement, gait movement, static conversion movement
Discrete matrix S between the class of a electromyography signal featureBWith discrete matrix S in classW, then calculate separately feature class separability index
Step 4 selects myoelectricity feature composition of the feature class separability index J higher than 0.6 static dynamic from myoelectricity feature pool
Make myoelectricity feature group, myoelectricity feature composition gait of the feature class separability index J higher than 0.5 acts myoelectricity feature group, feature class
Myoelectricity feature composition static conversion of the separability index J higher than 0.2 acts myoelectricity feature group.
Fig. 3 shows the feature class separability index value of the EMG feature set of 15 seed types of three experiment bodies.Higher spy
Sign class separability index means corresponding characteristic high separation.WAMP feature is come previous position, followed by MA, EWT
And EWP.IAV, ARCU and FE feature are worst.Fig. 3 also shows do not have in the feature class separability index value of electromyogram feature
There is significant individual difference.Spearman coefficient of rank correlation average value shows spearman between individual close to 0.98 between subject
Grade difference is little.This result shows that, even for a small number of subjects, the main result of this research is still complete, for every
A individual subjects, sample size are very big.In addition, in terms of the inherent feature of electromyography signal, handicapped person and without between handicapped person
It is not significantly different.
Fig. 4 shows the feature class separability index value of every kind of characteristic type and calculates time, the spy of every kind of characteristic type
It is all average for levying class separability index value and calculating time.The result shows that can divide well although some characteristic types have
Property, but the separability value of some characteristic types (such as EWT and EWP) is got well than many other features, but it is very long to calculate the time.
10 kinds of features of table act static conversion, the separability index of gait movement and the ADLs comprising tumble movement
Different characteristic extracting mode, which acts on different types of movement, might have the classifying quality of great disparity.In addition, single
Feature, the one side feature of electromyography signal can only be utilized, such as single MA only apply to the difference in magnitude feature of EMG.For energy
The information sufficiently provided with electromyography signal, this project propose: in conjunction with identifying the different classes of middle higher feature of separability index,
Consider dimension factor simultaneously, forms suitable feature set.The higher MA of separability index in static conversion movement is such as combined,
WAMP, FE, EWT composition characteristic group, and it is called the feature set suitable for static conversion classification, it is abbreviated as Static-Convert
Feature group;It is suitable for the feature of gait classification in conjunction with separability index higher VAR, WAMP, EWP, MA composition in gait movement
Collection, is abbreviated as Gait-Move feature group;In conjunction with the higher MA of feature class separability index value, WAMP, VAR and EWT group in ADLs
At the feature set for being suitable for classifying to ADLs, it is abbreviated as ADL-Act feature group.