A kind of high-precision denoising method of local ultrasound array signal
Technical field
The present invention relates to a kind of denoising method, especially a kind of high-precision denoising method of local ultrasound array signal.
Background technique
Often there is the influence of noise when electrical equipment type local-discharge ultrasonic array detection, it is therefore necessary to calculate the denoising of signal
Method is studied.Existing Denoising Algorithm is broadly divided into two classes, and the first kind is the denoising of individual signals, as Wavelet Denoising Method, EMD are gone
Make an uproar etc., such algorithm is only preferable to the denoising effect of single channel signal, when denoising with this method to array signal
It will affect the phase difference between each array signal, to causing significant impact in the processing of subsequent array signal;Second class is
The denoising of multichannel array signal, although such method will not influence the phase difference of array signal, but such algorithm is mainly
Based on blind source separating principle, restrictive condition is relatively more, and it is unobvious to denoise effect.
Summary of the invention
Technical problem to be solved by the invention is to provide a kind of high-precision denoising method of local ultrasound array signal,
It is good that effect is removed dryness to array signal.
In order to solve the above technical problems, the technical scheme adopted by the invention is that:
A kind of high-precision denoising method of local ultrasound array signal, it is characterised in that comprise the steps of:
The array signal of multichannel: being separated into the isolated component of statistics with quick isolated component FastICA by step 1,
Autocorrelation analysis, the preliminary influence for eliminating noise are carried out to these isolated components;
Step 2: the signal in each channel is further denoised with set empirical mode decomposition algorithm EEMD;
Step 3: the signal after essence denoising is recombinated, the signal after obtaining high-precision denoising.
Further, the quick isolated component FastICA is
It sets a trap and puts source signal as S (t)=[S1(t),S2(t),…SN(t)]T, by N number of mutually independent Partial discharge signal group
At the collected array signal of sensor array is expressed as follows shown in formula:
X (t)=AS (t)+n (t) (1)
Wherein, t is time variable, and X (t) is that M ties up the received N number of array signal of sensor, i.e. X (t)=[x1 (t), x2
(t) ... xN (t)] T, A is the unknown hybrid matrix of M × N rank, and n (t) is that M ties up observation noise vector;
With the array signal X (t) observed, seek separation matrix W, to obtain the estimation signal Y (t) of source signal.
Further, the step 1 is specially
1.1 pre-processing first to array signal X (t), pretreatment mainly comprising going two steps of mean value and albefaction, is gone
Mean value makes observation signal meet zero-mean, and the correlation between each data is eliminated in albefaction, so that each component is as independent as possible;
Using the mean value of following formula removal sample:
Array signal after going mean value is X0(t), to going the data after mean value to carry out whitening processing, it may be assumed that
X ' (t)=TX0(t) (3)
Array signal after whitening processing is X ' (t), and T is linear change matrix;
The initial value of 1.2 setting separation matrix W;
1.3 building quadratic function G1, G2, so that
A1=1.5, a2=2 in formula carry out derivation to G1, G2, and obtaining derived function is g1, g2;
1.4 carry out loop iteration with Newton iteration method, and iteration formula is W ← E (xg1(WTx′))-E(g2(WTX ')) W,
Until convergence;
1.5 seek the array signal after separation, it may be assumed that Y (t)=WTX (t).
Further, the set empirical mode decomposition algorithm EEMD is
The array signal obtained after denoising with FastICA, each channel do not have correlation, go to it with single channel
It will not influence the phase difference between array signal after algorithm of making an uproar denoising;
Y ' i (t) is obtained after different white noise sequence fi (t) is added in Yi (t), empirical modal point is carried out to Y ' i (t)
Solution, obtains each rank intrinsic mode function component (IMF), at this timeWherein Ck (t) is each rank natural mode
State function component, rnIt (t) is surplus.
Further, the step 2 is specially
2.1 calculate all Local Extremums of Y ' i (t);
The envelope up and down that all maximum points and minimum point are constituted is denoted as u by 2.2 respectively0i(t) and v0i(t);
The mean value of about 2.3 envelopes isThe envelope up and down of single channel Partial discharge signal it is equal
The difference of value is H0i(t)=Yi′(t)-m0i(t);
2.4 judge H0i(t) whether meet extreme point number or zero crossing number is equal or most differences one, and by part
The average value of coenvelope line and the lower envelope line being made of local minimum that maximum is constituted is zero, if meeting conditions above,
Then H0i(t) it is natural mode of vibration component, otherwise repeats 2.1~2.3 steps, until finding first natural mode of vibration component, is denoted as C1
(t);
2.5 note r1(t)=Yi′(t)-C1(t) it is new amount to be analyzed, repeats above step and obtain second IMF
Amount ... ... and so on obtains n IMF amount, finally remains next monotonic signal rn(t), therefore single channel original signal can be with
It indicates are as follows:
Compared with prior art, the present invention having the following advantages that and effect: EEMD is decomposed and is tied with FastICA phase by the present invention
The denoising for being applied to type local-discharge ultrasonic array signal is closed, solving traditional EMD decomposition can only be to single sensor, single channel signal
The drawbacks of denoising, FastICA can only denoise roughly array signal, avoids and causes because of the interference of live noise signal
DF and location error it is too big, so that improving supersonic array signal removes dryness effect and DF and location precision.
Detailed description of the invention
Fig. 1 is that a kind of high-precision of local ultrasound array signal of the invention removes the flow chart of drying method.
Fig. 2 is FastICA disassembler reconfiguration principle figure of the invention.
Fig. 3 is EEMD decomposition process figure of the invention.
Specific embodiment
Below by embodiment, the present invention is described in further detail, following embodiment be explanation of the invention and
The invention is not limited to following embodiments.
As shown in Figure 1, a kind of high-precision denoising method of local ultrasound array signal of the invention comprising the steps of:
The array signal of multichannel: being separated into the isolated component of statistics with quick isolated component FastICA by step 1,
Autocorrelation analysis, the preliminary influence for eliminating noise are carried out to these isolated components;
Quickly isolated component FastICA is
It sets a trap and puts source signal as S (t)=[S1(t),S2(t),…SN(t)]T, by N number of mutually independent Partial discharge signal group
At the collected array signal of sensor array is expressed as follows shown in formula:
X (t)=AS (t)+n (t) (1)
Wherein, t is time variable, and X (t) is that M ties up the received N number of array signal of sensor, i.e. X (t)=[x1 (t), x2
(t) ... xN (t)] T, A is the unknown hybrid matrix of M × N rank, and n (t) is that M ties up observation noise vector;
With the array signal X (t) observed, seek separation matrix W, to obtain the estimation signal Y (t) of source signal.
It is broadly divided into following steps:
1.1 first pre-process array signal X (t), and pretreatment mainly comprising going two steps of mean value and albefaction, is gone
Mean value makes observation signal meet zero-mean, and the correlation between each data is eliminated in albefaction, so that each component is as independent as possible;
Using the mean value of following formula removal sample:
Array signal after going mean value is X0(t), to going the data after mean value to carry out whitening processing, it may be assumed that
X ' (t)=TX0(t) (3)
Array signal after whitening processing is X ' (t), and T is linear change matrix;
The initial value of 1.2 setting separation matrix W;
1.3 building quadratic function G1, G2, so that
A1=1.5, a2=2 in formula carry out derivation to G1, G2, and obtaining derived function is g1, g2;
1.4 carry out loop iteration with Newton iteration method, and iteration formula is W ← E (xg1(WTx′))-E(g2(WTX ')) W,
Until convergence;
1.5 seek the array signal after separation, it may be assumed that Y (t)=WTX (t).
Step 2: the signal in each channel is further denoised with set empirical mode decomposition algorithm EEMD;
Gathering empirical mode decomposition algorithm EEMD is
The array signal obtained after denoising with FastICA, each channel do not have correlation, go to it with single channel
It will not influence the phase difference between array signal after algorithm of making an uproar denoising;
Y ' i (t) is obtained after different white noise sequence fi (t) is added in Yi (t), empirical modal point is carried out to Y ' i (t)
Solution, obtains each rank intrinsic mode function component (IMF), at this timeWherein Ck (t) is each rank natural mode
State function component, rnIt (t) is surplus.
Specific step is as follows:
2.1 calculate all Local Extremums of Y ' i (t);
The envelope up and down that all maximum points and minimum point are constituted is denoted as u by 2.2 respectively0i(t) and v0i(t);
The mean value of about 2.3 envelopes isThe envelope up and down of single channel Partial discharge signal it is equal
The difference of value is H0i(t)=Yi′(t)-m0i(t);
2.4 judge H0i(t) whether meet extreme point number or zero crossing number is equal or most differences one, and by part
The average value of coenvelope line and the lower envelope line being made of local minimum that maximum is constituted is zero, if meeting conditions above,
Then H0i(t) it is natural mode of vibration component, otherwise repeats 2.1~2.3 steps, until finding first natural mode of vibration component, is denoted as C1
(t);
2.5 note r1(t)=Yi′(t)-C1(t) it is new amount to be analyzed, repeats above step and obtain second IMF
Amount ... ... and so on obtains n IMF amount, finally remains next monotonic signal rn(t), therefore single channel original signal can be with
It indicates are as follows:
Step 3: the signal after essence denoising is recombinated, the signal after obtaining high-precision denoising.
EEMD is decomposed the denoising combined with FastICA applied to type local-discharge ultrasonic array signal by the present invention, solves biography
The EMD of system, which is decomposed, single sensor, single channel signal denoising, FastICA can only be denoised roughly to array signal
The drawbacks of, it is too big to avoid DF and location error caused by due to the interference of live noise signal, to improve supersonic array
Signal removes dryness effect and DF and location precision.
Above content is only illustrations made for the present invention described in this specification.Technology belonging to the present invention
The technical staff in field can do various modifications or supplement or is substituted in a similar manner to described specific embodiment, only
It should belong to guarantor of the invention without departing from the content or beyond the scope defined by this claim of description of the invention
Protect range.