CN-117233175-B - Automatic identification method for electromagnetic emission signals of concrete dam movable cracks based on cross-correlation analysis

CN117233175BCN 117233175 BCN117233175 BCN 117233175BCN-117233175-B

Abstract

An automatic identification method of electromagnetic emission signals of concrete dam movable cracks based on cross-correlation analysis comprises the steps of respectively obtaining electromagnetic radiation signals of space around a concrete dam by electromagnetic signal collecting devices at different positions at the same time to obtain N electromagnetic radiation signals, carrying out threshold judgment on the N preprocessed electromagnetic radiation signals, extracting and recording the number of the electromagnetic radiation signals exceeding an early warning threshold, judging whether the number of the electromagnetic radiation signals exceeding the early warning threshold is greater than or equal to 4, comparing the amplitude of the electromagnetic radiation signals exceeding the early warning threshold, carrying out cross-correlation analysis on marked electromagnetic radiation signals to obtain a cross-correlation function, taking the function of xcorr as the absolute value of the cross-correlation function, judging that the time corresponding to the maximum value meets a relational expression, calculating the average value Ave (p) of the electromagnetic radiation signals in a section, and obtaining the average value Ave of the electromagnetic radiation signals of the xcorr function in a defined section. The method has the advantages of high calculation speed and high recognition accuracy.

Inventors

HOU CHUNYAO
HUANG SONGLING
Ning Shaoqing
ZHANG JINGHUA
TAN DAWEN
ZHOU YI
LIU DEXIN
HU CHANGHAO
XIA FAN

Assignees

中国长江电力股份有限公司
清华大学

Dates

Publication Date: 20260505
Application Date: 20230807

Claims (9)

1. The automatic identification method of the concrete dam movable crack electromagnetic emission signal based on the cross-correlation analysis is characterized by comprising the following steps of: Step 1, electromagnetic radiation signals of the space around a concrete dam are respectively obtained by electromagnetic signal acquisition devices at different positions at the same time to obtain N electromagnetic radiation signals; step 2, preprocessing the N electromagnetic radiation signals obtained in the step 1; Step 3, threshold judgment is carried out on the N electromagnetic radiation signals preprocessed in the step 2, and the number of the electromagnetic radiation signals exceeding the early warning threshold is extracted and recorded; step 4, judging whether the number of electromagnetic radiation signals exceeding the early warning threshold is greater than or equal to 4, if so, performing step5, and if not, discarding the electromagnetic radiation signals collected in the current process, and performing step 1; Step 5, comparing the amplitude values of the electromagnetic radiation signals exceeding the early warning threshold value, arranging the electromagnetic radiation signals according to the sequence from high amplitude values to low amplitude values, and selecting four electromagnetic radiation signals with highest amplitude values as M1, M2, M3 and M4; Step 6, performing cross-correlation analysis on electromagnetic radiation signals marked as M1, M2, M3 and M4 to obtain a cross-correlation function, wherein the function of the cross-correlation function after taking absolute values is xcorr, and recording maximum values Max1, max2 and Max3 of the amplitude values of xcorr and time t1, t2 and t3 corresponding to the maximum values; Step 7, judging whether the time t1, t2 and t3 corresponding to the maximum value meet the following relation, if t1-t is less than or equal to Deltat, t2-t is less than or equal to Deltat and t3-t is less than or equal to Deltat, performing step 8, if not, discarding electromagnetic radiation signals acquired in the current process, and performing step 1; Step 8, obtaining the xcorr function in Electromagnetic radiation signals within the interval and calculating an average Ave (p) of the electromagnetic radiation signals within the interval; Step 9, obtaining the average value Ave of the electromagnetic radiation signals of the xcorr function in the defined interval, and identifying the coefficients of the electromagnetic radiation signals
2. The method for automatically identifying the electromagnetic emission signal of the movable crack of the concrete dam based on the cross-correlation analysis according to claim 1, wherein in the step 9, If R is more than or equal to 3, M1, M2, M3 and M4 are electromagnetic emission signals of the concrete dam movable cracks with large cracking degree, and the M1, M2, M3 and M4 signals are recorded and stored; If R is more than or equal to 2 and less than or equal to 3, M1, M2, M3 and M4 are electromagnetic emission signals of the movable cracks of the concrete dam with small cracking degree, and the signals of M1, M2, M3 and M4 are recorded and stored; if 0 is less than or equal to R <2 >, M1, M2, M3 and M4 are system interference or external noise, and M1, M2, M3 and M4 are abandoned.
3. The method for automatically identifying the electromagnetic emission signals of the movable cracks of the concrete dam based on the cross-correlation analysis according to claim 1, wherein in the step 1, a plurality of electromagnetic signal acquisition devices are arranged on the dam body of the concrete dam at equal intervals, the equal interval arrangement means that the longitudinal and transverse arrangement intervals of the high-speed electromagnetic signal acquisition devices on the plane of the dam body are 10m, the sampling speed of the high-speed electromagnetic signal acquisition devices is 10MHz, and the electromagnetic radiation signals are signal sequences with the duration of 40 us.
4. The automatic identification method for the concrete dam movable crack electromagnetic emission signals based on the cross-correlation analysis is characterized in that in the step 2, a band-pass filter and a comb filter are constructed to preprocess the N obtained electromagnetic radiation signals, the lower limit cut-off frequency of the band-pass filter is 10kHz, the upper limit cut-off frequency of the band-pass filter is 1MHz, and the comb filter is used for filtering noise of 50Hz and frequency multiplication thereof.
5. The method for automatically identifying the electromagnetic emission signal of the concrete dam movable crack based on the cross-correlation analysis according to claim 1, wherein in the step 3, the early warning threshold value means that the amplitude of the electromagnetic radiation signal is 100nT, and the exceeding of the early warning threshold value means that the maximum value of the absolute value of the electromagnetic radiation signal is greater than 100nT.
6. The method for automatically identifying the electromagnetic emission signal of the concrete dam movable crack based on the cross-correlation analysis according to claim 1, wherein in the step 5, the amplitude of the electromagnetic radiation signal refers to the maximum value of the absolute value of the electromagnetic radiation signal.
7. The method for automatically identifying the electromagnetic emission signal of the concrete dam movable crack based on the cross-correlation analysis according to claim 1, wherein in the step 6, the M1 electromagnetic radiation signal is used as a reference, the M1, the M2, the M1, the M3, the M1 and the M4 electromagnetic radiation signals are respectively subjected to the cross-correlation analysis, the maximum value of the amplitude of xcorr Max1, max2 and Max3 refers to the maximum value of the absolute value of each cross-correlation function after the M1, the M2, the M1, the M3, the M1 and the M4 electromagnetic radiation signals are subjected to the cross-correlation analysis, and the cross-correlation function is specifically as follows: Let the electromagnetic radiation signals of M1, M2, M3 and M4 be x1 (t), x2 (t), x3 (t), x4 (t), respectively; m1 and M2 cross correlation analysis to obtain cross correlation function M1 and M3 cross correlation analysis to obtain cross correlation function M1 and M4 cross correlation analysis to obtain cross correlation function
8. The method for automatically identifying the electromagnetic emission signal of the concrete dam movable crack based on the cross-correlation analysis according to claim 1, wherein in the step 7, t=40us, Δt=5us, and an average value Ave (p) of the electromagnetic radiation signal in the interval means that the electromagnetic radiation signal is in the interval The accumulation of xcorr function values at each time in the interval divided by the sum of sampling points in the interval; let the electromagnetic radiation signals of M1, M2, M3 and M4 be x1 (t), x2 (t), x3 (t), x4 (t); and M1 and M2 cross-correlation analysis is carried out to obtain a cross-correlation function, wherein the function after the cross-correlation function takes an absolute value is as follows: and M1 and M3 cross-correlation analysis is carried out to obtain a cross-correlation function, wherein the function after the cross-correlation function takes an absolute value is as follows: And M1 and M4 cross-correlation analysis is carried out to obtain a cross-correlation function, wherein the function after the cross-correlation function takes an absolute value is as follows:
9. The method for automatically identifying the electromagnetic emission signal of the concrete dam movable crack based on the cross-correlation analysis according to claim 1, wherein in the step 8, the interval is defined as the duration [0,2t ] of the xcorr function, and the Ave refers to the sum of the xcorr function values at each moment in the [0,2t ] interval divided by the sum of the sampling points in the interval.

Description

Automatic identification method for electromagnetic emission signals of concrete dam movable cracks based on cross-correlation analysis Technical Field The invention relates to the technical field of electromagnetic monitoring, in particular to an automatic identification method for an electromagnetic emission signal of a concrete dam movable crack based on cross-correlation analysis. Background The electromagnetic monitoring technology is widely applied to safety detection and defect evaluation of large-scale components such as bridge damage detection, coal mine detection and the like. Electromagnetic monitoring of movable cracks of a concrete dam is an important guarantee for safe and stable operation of the concrete dam, the concrete dam is often located in an area with complex stress conditions and steep mountain potential, and monitoring of the movable cracks of the concrete dam is often affected by stress changes and environmental noise, so that signal identification in the electromagnetic monitoring of the movable cracks of the concrete dam becomes difficulty and hot spot of current research, an existing electromagnetic signal identification method is complex in calculation model and long in calculation time, and concrete electromagnetic radiation signals are difficult to extract effectively. In the prior art, although the Chinese patent 'a coal-rock interface identification method' (patent number: 202110250593.7) can identify electromagnetic signals through intensity, main frequency, frequency band, duration and the like of electromagnetic radiation signals, the construction mode is too simple, and interference of suddenly-changed external interference on electromagnetic signal identification is not considered. Chinese patent 'an electromagnetic radiation data monitoring analysis method and system' (patent number: ZL 202111095842.6), although the electromagnetic radiation time sequence data can be utilized to carry out model training to obtain a fluctuation trend model of electromagnetic radiation signals so as to obtain monitoring of electromagnetic radiation data, long calculation time, low efficiency and easy parameter change caused by the change of training samples are needed to be utilized to memorize network training parameters for a long period. Disclosure of Invention In order to solve the technical problems, the invention provides an automatic identification method of electromagnetic emission signals of concrete dam movable cracks based on cross-correlation analysis, which utilizes an electromagnetic monitoring device of the concrete dam movable cracks to acquire electromagnetic radiation signals, extracts data with high electromagnetic radiation signal intensity, carries out cross-correlation analysis on the data, and selects the ratio of interval average values of cross-correlation functions as an electromagnetic emission signal identification coefficient by comparing the relations among the cross-correlation functions. The method has the advantages of high calculation speed and high recognition accuracy. The technical scheme adopted by the invention is as follows: the automatic identification method of the concrete dam movable crack electromagnetic emission signal based on the cross-correlation analysis is characterized by comprising the following steps of: Step 1, electromagnetic radiation signals of the space around a concrete dam are respectively obtained by electromagnetic signal acquisition devices at different positions at the same time to obtain N electromagnetic radiation signals; step 2, preprocessing the N electromagnetic radiation signals obtained in the step 1; Step 3, threshold judgment is carried out on the N electromagnetic radiation signals preprocessed in the step 2, and the number of the electromagnetic radiation signals exceeding the early warning threshold is extracted and recorded; step 4, judging whether the number of electromagnetic radiation signals exceeding the early warning threshold is greater than or equal to 4, if so, performing step5, and if not, discarding the electromagnetic radiation signals collected in the current process, and performing step 1; Step 5, comparing the amplitude values of the electromagnetic radiation signals exceeding the early warning threshold value, arranging the electromagnetic radiation signals according to the sequence from high amplitude values to low amplitude values, and selecting four electromagnetic radiation signals with highest amplitude values as M1, M2, M3 and M4; Step 6, performing cross-correlation analysis on electromagnetic radiation signals marked as M1, M2, M3 and M4 to obtain a cross-correlation function, wherein the function of the cross-correlation function after taking absolute values is xcorr, and recording maximum values Max1, max2 and Max3 of the amplitude values of xcorr and time t1, t2 and t3 corresponding to the maximum values; and 7, judging whether the time t1, t2 and t3 corresponding to the maximum valu