CN109632945A - A kind of noise-reduction method suitable for Pulsed eddy current testing signal - Google Patents

A kind of noise-reduction method suitable for Pulsed eddy current testing signal Download PDF

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Publication number
CN109632945A
CN109632945A CN201910052547.9A CN201910052547A CN109632945A CN 109632945 A CN109632945 A CN 109632945A CN 201910052547 A CN201910052547 A CN 201910052547A CN 109632945 A CN109632945 A CN 109632945A
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imf
signal
eddy current
noise
component
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王强
曹腾飞
宋俊俊
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China Jiliang University
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China Jiliang University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/72—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables
    • G01N27/82—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws
    • G01N27/90—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws using eddy currents
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/72—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H17/00—Networks using digital techniques
    • H03H17/02—Frequency selective networks
    • H03H17/0201—Wave digital filters
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H17/00—Networks using digital techniques
    • H03H17/02—Frequency selective networks
    • H03H17/0219—Compensation of undesirable effects, e.g. quantisation noise, overflow
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H17/00—Networks using digital techniques
    • H03H17/02—Frequency selective networks
    • H03H17/0202—Two or more dimensional filters; Filters for complex signals
    • H03H2017/0207—Median filters

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  • Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Computer Hardware Design (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mathematical Physics (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)

Abstract

The invention discloses a kind of noise-reduction methods suitable for Pulsed eddy current testing signal, comprising the following steps: decomposes to obtain multiple IMF components using EEMD；The association relationship of each IMF component and original signal is acquired using mutual information method；The IMF component for being less than Average Mutual value to association relationship carries out information extraction；Reconstruction signal is to obtain the signal after noise reduction.The present invention is based on EEMD, efficiently solve EMD bring modal overlap；For the wide band feature of impulse eddy current signal, noise is filtered out using mutual information method and accounts for leading IMF component, median filter process then is carried out to this part IMF, last reconstruction signal has accomplished good de-noising on the basis of being sufficiently reserved original signal.

Description

A kind of noise-reduction method suitable for Pulsed eddy current testing signal
Technical field
The present invention relates to field of non destructive testing, and in particular to a kind of noise-reduction method suitable for Pulsed eddy current testing signal.
Background technique
Pulsed eddy current testing is a new branch of eddy detection technology, it is will excitation on the basis of EDDY CURRENT Signal is adjusted to rectangular pulse pulse by sine wave and is got, since its pumping signal is rectangular pulse, so having wide spectrum The characteristics of ingredient, allow to penetrate the clad on bearing device surface, realizes the on-line checking for not removing clad, therefore Bearing device detection field is widely used.
For the noise reduction of this non-stationary signal of Pulsed eddy current testing signal, wavelet transformation is a kind of common method, but Its noise reduction effect is often depending on the selection of wavelet basis and threshold value, lacks adaptivity.Chinese patent (publication number: CN 108802175A) disclose a kind of Pulsed eddy current testing signal de-noising method based on EMD.This method believes Pulsed eddy current testing Number EMD decomposition is carried out, IMF is screened using cross-correlation coefficient, and details is carried out to the IMF that filters out using 3 σ rules and is mentioned It takes, the disadvantages of the method are as follows being based on EMD, be easy to cause modal overlap problem, and can only be filtered out using cross-correlation coefficient low The IMF component of rank high frequency is not strong to the broadband signal applicability of Pulsed eddy current testing.
Set empirical mode decomposition (Ensemble Empirical Mode Decomposition, EEMD) is for warp The deficiency for testing mode decomposition (Empirical Mode Decomposition, EMD) method, proposes a kind of noise auxiliary data Analysis method, it solves the problems, such as the modal overlap of EMD.Using EEMD to being needed in the treatment process of Pulsed eddy current testing signal It is screened, previous screening technique to the intrinsic mode function (Intrinsic Mode Function, IMF) generated is decomposed It is the cross-correlation coefficient for asking each IMF and original signal, IMF when then obtaining minimum value with first cross-correlation coefficient is boundary Point is rejected or is handled to the lower order high frequency IMF before separation, then is reconstructed to obtain the signal after de-noising to signal. The characteristics of for Pulsed eddy current testing signal due to its wide spectrum, actual signal are possibly comprised in each rank IMF, so with mutually Related coefficient is less applicable in screen.
For mutual information (Mutual Information, MI) from the concept amplification of entropy, it represents two stochastic variables Between the information content that provides mutually, whether can be seen that from its numerical value has the power of relationship and relationship between two variables, Association relationship be can use to judge the power of each IMF Yu original signal relationship, thus to screen to IMF.
Summary of the invention
The purpose of the present invention is to solve deficiency existing for existing method, i.e., the problem of above-mentioned " applicability is not strong ", mention For a kind of noise-reduction method suitable for Pulsed eddy current testing signal, realize to the effective noise reduction of Pulsed eddy current testing signal.
In order to achieve the above object, the present invention decomposes to obtain multiple IMF to Pulsed eddy current testing signal progress EEMD first, The association relationship between each IMF component and original signal is acquired, and acquires Average Mutual value MI and further the value of information is lower than The component of MI carries out median filter process, and component of the association relationship higher than MI is then not processed, is finally reconstructed, obtains to signal Signal after to noise reduction, the technical solution of proposed adoption is as follows to realize the present invention:
(1) EEMD is carried out to noise-containing Pulsed eddy current testing signal x (t) to decompose to obtain:
Wherein imfiIndicate that i-th of IMF component, r (t) are to decompose discrepance.
(2) each imf is calculatediAssociation relationship between x (t):
I(x,imfi)=H (imfi)-H(imfi|x)
Wherein H (imfi) be i-th of IMF unconditional entropy, H (imfi| it x) is condition of i-th of IMF under the conditions of knowing x Entropy；
(3) it is averaging association relationship MI:
This part IMF component by association relationship less than MI regards as noisy component；
(4) median filter process is carried out to this part IMF filtered out；
(5) processed IMF component and remaining IMF component and decomposition discrepance are reconstructed, obtain by reconstruction signal Signal after noise reductionThen x'(t) be noise reduction after signal.
The present invention has the following advantages compared with prior art:
1. the present invention is decomposed using EEMD, is decomposed compared to EMD, efficiently solve the problems, such as modal overlap；
2. the present invention carries out the screening of IMF component using mutual information method, it is more suitable for Pulsed eddy current testing signal wide-band The characteristics of, can Effective selection go out the noisy IMF of each frequency range；
3. the present invention carries out median filtering to the IMF component filtered out, compared to the method for directly removing noisy IMF, protect More detailed information are stayed.
Detailed description of the invention
Fig. 1 illustrates flow diagram of the invention；
Fig. 2 is the waveform diagram of original signal；
Fig. 3 is each IMF component that arrives and the waveform diagram of decomposing discrepance of the original signal after EEMD is decomposed；
Fig. 4 is the waveform diagram of the IMF component that filters out after median filtering；
Fig. 5 is the waveform diagram of signal after noise reduction.
Specific embodiment
Technical method of the invention is specifically described below with reference to example and Figure of description:
A kind of noise-reduction method suitable for Pulsed eddy current testing signal, as shown in Figure 1, specifically includes the following steps:
(1) impulse eddy current signal is obtained, is examined here in matlab with bump wave plus noise come analogue simulation impulse eddy current Signal is surveyed, as shown in Figure 2.
(2) EEMD decomposition is carried out to the signal of acquisition, as shown in figure 3, being decomposed into 8 layers of IMF component and a decomposition remnants ?.
(3) mutual trust between 8 IMF components and original signal is calculated separately out using mutual information calculation formula given above Breath value and Average Mutual value are as shown in table 1:
1 association relationship table of table
(4) the 1st, 2,5, the 7 layer of IMF that association relationship is less than Average Mutual value is considered as noisy component, to this part IMF Median filter process is carried out, this four layers of IMF components after processing are as shown in Figure 4.
(5) reconstruction signal by processed four layers of IMF component and the four layers of IMF component not processed and decomposes remaining Item is reconstructed, and the signal after obtained de-noising is as shown in Figure 5.
What has been described above is only an embodiment of the present invention, and the common sense such as well known specific method or characteristic are not made herein in scheme Excessive description.It should be pointed out that under the premise of not departing from the present invention, can also be carried out for those skilled in the art Several improvement, these also should be considered as protection scope of the present invention, these all will not influence the effect and patent that the present invention is implemented Practicability.This application claims protection scope should be subject to the content of claim, the specific embodiment in specification Equal records can be used for explaining the content of claim.

Claims (2)

1. a kind of noise-reduction method suitable for Pulsed eddy current testing signal, which is characterized in that method includes the following steps:
(1) EEMD is carried out to noise-containing Pulsed eddy current testing signal x (t) to decompose to obtain:
Wherein imfiIndicate that i-th of IMF component, r (t) are to decompose discrepance；
(2) each imf is calculatediAssociation relationship between x (t):
I(x,imfi)=H (imfi)-H(imfi|x)
Wherein H (imfi) be i-th of IMF unconditional entropy, H (imfi| it x) is condition of i-th each IMF under the conditions of knowing x value Entropy；
(3) it is averaging association relationship MI:
This part IMF component by association relationship less than MI regards as noisy component；
(4) median filter process is carried out to this part IMF filtered out；
(5) processed IMF component and remaining IMF component and decomposition discrepance are reconstructed, obtain noise reduction by reconstruction signal Signal afterwardsThen x'(t) be noise reduction after signal.
2. the noise-reduction method according to claim 1 suitable for Pulsed eddy current testing signal, which is characterized in that the step (1), (2), (3), (4) carry out EEMD decomposition to impulse eddy current signal, using mutual information method screen IMF and to this part IMF Carry out median filtering.
CN201910052547.9A 2019-01-21 2019-01-21 A kind of noise-reduction method suitable for Pulsed eddy current testing signal Pending CN109632945A (en)

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CN112129830A (en) * 2020-09-02 2020-12-25 中国人民解放军空军工程大学航空机务士官学校 Aircraft metal structure burn detection method based on eddy current conductivity

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CN108982657A (en) * 2018-06-08 2018-12-11 南京航空航天大学 A kind of ferrimagnet yield strength method for parameter estimation based on impulse eddy current
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CN112129830A (en) * 2020-09-02 2020-12-25 中国人民解放军空军工程大学航空机务士官学校 Aircraft metal structure burn detection method based on eddy current conductivity
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Application publication date: 20190416