CN107632064B - Method for suppressing eddy current detection interference signal - Google Patents
Method for suppressing eddy current detection interference signal Download PDFInfo
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- CN107632064B CN107632064B CN201710744208.8A CN201710744208A CN107632064B CN 107632064 B CN107632064 B CN 107632064B CN 201710744208 A CN201710744208 A CN 201710744208A CN 107632064 B CN107632064 B CN 107632064B
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Abstract
The invention discloses an eddy current detection interference signal suppression method, which is based on the characteristic that the frequency bandwidth of an interference signal in eddy current detection is greater than that of a defect signal, and adopts two channels and two band-pass filtering methods to effectively filter the interference signal in a detection signal and reduce the influence of the interference signal on the defect signal to the minimum.
Description
Technical Field
The invention relates to a nondestructive testing method, in particular to a method for suppressing an eddy current testing interference signal.
Background
The eddy current detection method is a material quality detection method commonly used in the metallurgical industry, wherein the eddy current automatic flaw detection system is widely applied, one important index for measuring the performance of the eddy current automatic flaw detection system is the leakage and false alarm rate, the repeatability of the equipment for detecting the same defect is reflected, and the important index is related to the performance of each part of the equipment (including a flaw detection instrument, a probe, a flaw detection host and a transmission device), the running uniformity of a sample tube and the equipment and the like, particularly related to external environment interference factors and is a comprehensive index. If the signal-to-noise ratio of the detection instrument is low, the interference signals cannot be effectively distinguished and eliminated, false alarm is easy to occur, and the leakage and false alarm rate of the equipment is high. Therefore, the false missing rate of the device is reduced to the minimum (equal to 0), which only starts from various aspects such as instruments, probes, main machines, mechanical transmission and the like, wherein the signal to noise ratio of the detection device is improved, various interference factors are eliminated, and particularly, in the instrument, a certain digital signal processing method can be adopted to eliminate various random interference signals mixed in the detection signals even under the condition that various interference factors cannot be avoided. In the automatic eddy current inspection system for the pipe and the bar, frequently encountered interference signals are vibration (caused by small diameter and soft rigidity of the bar) generated in the transmission process, impact vibration and the like generated when the bar meets an obstacle, and the vibration interference signals are superposed with a defect signal vector, so that the defect signal is difficult to distinguish from the defect signal vector, and the false alarm of the inspection equipment is caused.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides an eddy current detection interference signal suppression method, which is used for filtering an interference signal in a detection signal by adopting two channels and two band-pass filtering methods based on the characteristic that the frequency bandwidth of the interference signal in eddy current detection is greater than that of a defect signal.
The technical scheme adopted by the invention for solving the technical problems is as follows: an eddy current test interference signal suppression method is characterized in that: based on the characteristic that the frequency bandwidth of the interference signal is larger than that of the defect signal in the eddy current detection, the method adopts two channels and two band-pass filtering methods and comprises the following steps,
a. the detection signal acquired by the eddy current detection sensor is amplified and subjected to analog-to-digital conversion, the detection signal at the moment comprises a defect signal and an interference signal, and the defect signal and the interference signal cannot be distinguished and identified; then the detection signal passes through two band-pass digital filters through two channels respectively; the two band-pass digital filters respectively adopt band-pass with different ranges for filtering, wherein the band-pass range of one band-pass digital filter covers the superposed region of the defect signal frequency band and the interference signal frequency band, namely the band-pass digital filter enables the superposed signal of the defect signal and the interference signal within the defect signal frequency band range to pass; the band-pass range of the other band-pass digital filter is outside the frequency band of the eddy current detection defect signal and inside the frequency band of the interference signal, namely the band-pass digital filter only allows the interference signal to pass;
b. performing vector operation on the signals subjected to the two band-pass digital filters, namely subtracting the other interference signal subjected to the band-pass digital filtering from the superposed signal of the defect signal subjected to the band-pass digital filtering and the interference signal in the frequency band range of the defect signal; the main body of the detection signal after the vector operation is a defect signal, namely most of interference signals are subtracted through the vector operation, and the residual interference signals do not influence the identification of the defect signal.
The method for suppressing the interference signal in the eddy current detection has the advantages that the method for suppressing the interference signal in the eddy current detection effectively filters the interference signal in the detection signal by adopting two channels and two band-pass filtering methods based on the characteristic that the frequency bandwidth of the interference signal in the eddy current detection is larger than that of the defect signal, and the influence of the interference signal on the defect signal is reduced to the minimum.
The present invention will be described in further detail with reference to examples, but the method for suppressing an eddy current test interference signal according to the present invention is not limited to the examples.
Drawings
The invention will be further elucidated with reference to an embodiment in the drawing.
Fig. 1 is a schematic diagram of two channels and two bandpass filtering methods according to an embodiment of the present invention.
Fig. 2 is a schematic diagram of detection signals before and after interference suppression according to an embodiment of the present invention.
In the figure, s1 is a defect signal band, s2 is an interference signal band, s is a superimposed region of the defect signal band and the interference signal band, e is a defect signal, and i is an interference signal.
Detailed Description
In an embodiment, as shown in fig. 1 and fig. 2, a method for suppressing an eddy current test interference signal is characterized in that: based on the characteristic that the width of an interference signal frequency band S2 is larger than the width of a defect signal frequency band S1 in eddy current detection, the method adopts two channels and two band-pass filtering methods and comprises the following steps,
a. amplifying and performing analog-to-digital conversion on a detection signal acquired by the eddy current detection sensor, wherein the detection signal at the moment comprises a defect signal E and an interference signal I, and the defect signal E and the interference signal I cannot be distinguished and identified; then the detection signal passes through two band-pass digital filters through two channels respectively; the two band-pass digital filters respectively adopt band-pass with different ranges for filtering, wherein the band-pass range of one band-pass digital filter covers the superposed region S of the defect signal frequency band S1 and the interference signal frequency band S2, namely the band-pass digital filter enables the superposed signal of the defect signal E and the interference signal I within the defect signal frequency band S1 to pass; the band-pass range of the other band-pass digital filter is outside the eddy current detection defect signal band S1 and inside the interference signal band S2, namely, the band-pass digital filter only allows the interference signal I to pass through;
b. performing vector operation on the signals subjected to the two band-pass digital filters, namely subtracting the interference signal I subjected to the other band-pass digital filtering from the superimposed signal of the defect signal E subjected to the band-pass digital filtering and the interference signal I in the range of the defect signal frequency band S1; the main body of the detection signal after the vector operation is a defect signal E, namely most of interference signals I are subtracted through the vector operation, and the residual interference signals I do not influence the identification of the defect signal E.
The above embodiments are only used to further illustrate the method for suppressing the interference signal of eddy current test of the present invention, but the present invention is not limited to the embodiments, and any simple modification, equivalent change and modification made to the above embodiments according to the technical spirit of the present invention fall within the protection scope of the technical solution of the present invention.
Claims (1)
1. An eddy current test interference signal suppression method is characterized in that: based on the characteristic that the frequency bandwidth of the interference signal is larger than that of the defect signal in the eddy current detection, the method adopts two channels and two band-pass filtering methods and comprises the following steps,
a. the detection signal acquired by the eddy current detection sensor is amplified and subjected to analog-to-digital conversion, the detection signal at the moment comprises a defect signal and an interference signal, and the defect signal and the interference signal cannot be distinguished and identified; then the detection signal passes through two band-pass digital filters through two channels respectively; the two band-pass digital filters respectively adopt band-pass with different ranges for filtering, wherein the band-pass range of one band-pass digital filter covers the superposed region of the defect signal frequency band and the interference signal frequency band, namely the band-pass digital filter enables the superposed signal of the defect signal and the interference signal within the defect signal frequency band range to pass; the band-pass range of the other band-pass digital filter is outside the frequency band of the eddy current detection defect signal and inside the frequency band of the interference signal, namely the band-pass digital filter only allows the interference signal to pass;
b. performing vector operation on the signals subjected to the two band-pass digital filters, namely subtracting the other interference signal subjected to the band-pass digital filtering from the superposed signal of the defect signal subjected to the band-pass digital filtering and the interference signal in the frequency band range of the defect signal; the main body of the detection signal after the vector operation is a defect signal, namely most of interference signals are subtracted through the vector operation, and the residual interference signals do not influence the identification of the defect signal.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| GB1475517A (en) * | 1974-06-27 | 1977-06-01 | British Steel Corp | Detection of surface defects in elongate metallic members |
| CN201229197Y (en) * | 2008-06-20 | 2009-04-29 | 宝山钢铁股份有限公司 | Filter arrangement for vortex flow sensor detecting system |
| CN102147429B (en) * | 2011-02-28 | 2013-04-24 | 中国科学院国家天文台 | Broadband microwave power meter and interference signal filtering method |
| JP5983556B2 (en) * | 2012-11-28 | 2016-08-31 | Ｊｆｅスチール株式会社 | Leakage magnetic flux type inspection apparatus and inspection method |
| CN103973612A (en) * | 2013-01-25 | 2014-08-06 | 华为技术有限公司 | Near field reflection self-interference signal offset method and device |
| CN106789777B (en) * | 2015-11-19 | 2019-11-29 | 北京科技大学 | Wear digital interference elimination, bypassing method and the device in steel number energy simultaneous interpretation system |
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