CN110208364B - Steel wire rope defect positioning method without position sensor - Google Patents
Steel wire rope defect positioning method without position sensor Download PDFInfo
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- CN110208364B CN110208364B CN201910633704.5A CN201910633704A CN110208364B CN 110208364 B CN110208364 B CN 110208364B CN 201910633704 A CN201910633704 A CN 201910633704A CN 110208364 B CN110208364 B CN 110208364B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/004—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring coordinates of points
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/02—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/14—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring distance or clearance between spaced objects or spaced apertures
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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
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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
- G01N27/83—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws by investigating stray magnetic fields
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Abstract
The invention provides a method for positioning defects of a steel wire rope without a position sensor, which comprises the following steps: s1, performing isochronous sampling on the magnetic detection sensor to obtain a strand wave waveform related to the running speed of the steel wire rope; s2, processing the wave form of the strand to obtain the instantaneous frequency information of the strand of each isochronous sampling point; s3, processing the instantaneous frequency information of the strand wave according to the wire strand distance to obtain the speed information of each isochronous sampling point; and S4, converting each isochronous sampling point to a corresponding distance position on the steel wire rope by combining the isochronous sampling frequency and the speed information of the sampling point, and realizing the positioning of the defect sampling signal point on the steel wire rope. The invention has the beneficial effects that: the isochronal sampling signals are converted into specific distance information on the steel wire rope, and compared with the traditional coding wheel equidistant sampling positioning, the accuracy of steel wire rope distance measurement and defect positioning is greatly improved.
Description
Technical Field
The invention relates to a method for positioning defects of a steel wire rope, in particular to a method for positioning defects of a steel wire rope without a position sensor.
Background
In nondestructive testing of steel wire ropes, equidistant sampling is often used to locate the defect signals. At present, equidistant sampling is realized by a multi-purpose coding wheel, and the coding wheel needs to be tightly attached to a steel wire rope. The nondestructive testing probe drives the coding wheel to slide when in operation, and equidistant sampling signals are generated through the coding wheel. When the coding wheel is in contact operation with the steel wire rope, idling is easy to occur, and when the coding wheel is tightly attached to the steel wire rope, the pulley is easy to be blocked. Because the coding wheel is in contact type sampling, abrasion is easy to cause, and the precision of the coding wheel is reduced due to overlong time, thereby influencing the positioning precision.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a method for positioning the defects of a steel wire rope without a position sensor.
The invention provides a method for positioning defects of a steel wire rope without a position sensor, which comprises the following steps:
s1, performing isochronous sampling on the magnetic detection sensor to obtain a strand wave waveform related to the running speed of the steel wire rope;
s2, processing the wave form of the strand to obtain the instantaneous frequency information of the strand of each isochronous sampling point;
s3, processing the strand instantaneous frequency information of the strand according to the wire strand distance to obtain the speed information of each isochronous sampling point;
and S4, converting each isochronous sampling point to a corresponding distance position on the steel wire rope by combining the isochronous sampling frequency and the speed information of the sampling point, and realizing the positioning of the defect sampling signal point on the steel wire rope.
As a further improvement of the present invention, in step S2, a WVD-Viterbi time-frequency analysis is applied to the waveform of the strand wave to obtain the instantaneous frequency information of the strand wave at each isochronous sampling point.
As a further improvement of the present invention, in step S3, the instantaneous frequency information of the strand is converted into velocity information based on the wire strand pitch length and the isochronous sampling frequency.
As a further improvement of the present invention, in step S4, the displacement of the wire rope at each time is obtained according to the speed information and the sampling time, the isochronous sampling point where the defect is located is determined, and the physical position of the defect on the wire rope is determined according to the displacement.
As a further improvement of the present invention, in step S1, the sampled signal of the magnetic detection sensor is sampled isochronously and stored, and noise and dc components in the sampled signal are filtered out by using a butterworth digital filter and a method of subtracting the mean value of signal segments.
As a further improvement of the invention, between the step S1 and the step S2, the step S10 is carried out to judge whether the joint defect exists, if so, the EEMD processing is carried out to filter out the defect signal, and then the step S2 is carried out, and if not, the step S2 is carried out.
As a further improvement of the present invention, in step S10, it is determined whether or not a joint defect signal is present in the application using the waveform amplitude information.
As a further improvement of the present invention, in step S10, the defect signal is rejected using EEMD, which includes the following processes:
1) EEMD decomposition is carried out on the defect signal section;
2) determining the wavelet to be selected by using a correlation coefficient formula;
3) the wavelets are synthesized into a new waveform to replace the original defect signal segment.
As a further improvement of the present invention, in step S1, selecting a magnetic detection sensor signal in one or more paths of steel wire rope nondestructive testing devices to perform isochronous sampling with a sampling frequency fs, performing digital signal processing on the sampling result, filtering noise by a butterworth filter, subtracting the average value of the whole sampling from the signal to obtain a sampling signal without a dc component, after the processing is completed, equally dividing the sampling result into waveforms by using sampling windows, and determining the amplitude range of the burst signal, wherein the division principle is that the number of burst cycles in each sampling window needs to meet the precision requirement of the WVD-Viterbi time-frequency analysis, and determining whether a joint defect signal exists in each sampling window, the determination method is as follows:
1) calculating an extreme point of the signal in the window;
2) making a difference between every two adjacent extreme points, and recording the difference value;
3) comparing the maximum difference with a normal strand wave range, and if the maximum difference is more than two times of the normal strand wave range, judging that xx defect signals exist;
4) EEMD decomposition is carried out on the joint defect signal, and decomposed sub-waveforms are selected according to the formula xx to replace original waveforms.
As a further improvement of the present invention, in step S2, performing WVD conversion on each sampling window to obtain a time-frequency distribution graph of the waveform, extracting a frequency-time variation curve in the time-frequency distribution graph by using a Viterbi algorithm, and transforming the curve of each time-frequency windowThe lines are combined together according to the time relationship to form a time-frequency curve of the complete sampling signal; in step S4, the wire strand pitch is X, and the instantaneous frequency for the ith isochronous sampling point is f i And solving the distance from the ith sampling point to the starting point of the steel wire rope as follows:
the invention has the beneficial effects that: through the scheme, the equal-time sampling signals are converted into the specific distance information on the steel wire rope, and compared with the traditional equidistant sampling positioning of the encoding wheel, the precision of the distance measurement and the defect positioning of the steel wire rope is greatly improved.
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Fig. 1 is a flow chart of a method for positioning a defect of a steel wire rope without a position sensor according to the present invention.
Detailed Description
The invention is further described with reference to the following description and embodiments in conjunction with the accompanying drawings.
As shown in fig. 1, in the method for positioning the defect of the steel wire rope without the position sensor, a magnetic detection sensor is subjected to isochronous sampling to obtain a strand wave signal related to the running speed of the steel wire rope; performing WVD-Viterbi time-frequency analysis on the strand wave signal to obtain the strand wave instantaneous frequency information of each isochronous sampling point; converting instantaneous frequency information of strand waves into speed information according to the length of the distance of the steel wire strands and the isochronous sampling frequency; obtaining the displacement of the steel wire rope at each moment according to the speed information and the sampling time; determining the isochronous sampling point where the defect is located, and determining the physical position of the defect on the steel wire rope according to the displacement information; and for the mutated defect signals, the EEMD method is adopted to eliminate the defect waveforms, so that the influence of the defect signals on the estimation of the strand wave frequency is avoided, and the distance measurement of the steel wire rope is realized.
Wigner-Ville Distribution (WVD), also known as Wigner spectrum analysis, is a quadratic time-frequency representation for non-stationary signal processing, whose principle is to perform fourier transform on the autocorrelation function of the signal. And extracting energy peak values on a time axis from the result of the WVD distribution to obtain a time-frequency change curve of the signal, namely obtaining an instantaneous frequency value at each moment.
Ensemble Empirical Mode Decomposition (EEMD) is an Empirical-based signal Decomposition method, and its core algorithm is an Empirical Mode Decomposition (EEMD). EMD is a form that decomposes a waveform into a series of connotative modal components and residuals. Compared with wavelet decomposition and Fourier decomposition, the method has the characteristic that a basis function does not need to be selected. EEMD is based on EMD, adding white noise to input signal, EMD decomposing for several times, and averaging all the decomposition results to obtain final output result. EEMD overcomes the modal aliasing problem of EMD.
The Viterbi Algorithm (Viterbi Algorithm) is commonly used for image processing and signal decoding and is a dynamic programming Algorithm that finds the optimal path between two states. This method requires that the object to be used must satisfy a first order markov model. In the invention, the method is used for extracting frequency information in the WVD distribution, namely, the optimal frequency value at the current moment is obtained when the instantaneous frequency value at the last moment is known.
The WVD-Viterbi algorithm is a Viterbi algorithm optimized Wigner distribution, and compared with a Wigner distribution obtained by direct peak extraction, the method has higher noise resistance and better instantaneous frequency estimation accuracy.
In the nondestructive testing of the steel wire rope in the magnetic testing mode, because the winding mode of the steel wire rope strand is special, a sinusoidal periodic signal, also called a strand wave signal, is reflected in the magnetic testing sensor. The change of the running speed of the steel wire rope nondestructive testing probe on the steel wire rope can cause the stretching or contraction phenomenon of the strand wave in the magnetic detection sensor, and the change of the strand wave can be reflected as the frequency change in an isochronous sampling system. The method for positioning the defects of the steel wire rope without the position sensor performs isochronous sampling on signals in a magnetic detection sensor in a steel wire rope nondestructive testing flaw detector, realizes conversion between isochronous sampling points and physical positions of the isochronous sampling points, and achieves a distance measurement effect.
The invention adopts a magnetic detection method for nondestructive detection of the steel wire rope, namely, the steel wire rope is applied with electromagnetic excitation, and the main magnetic flux or magnetic flux leakage at the defect part of the steel wire rope is different from that at the normal part, so that the defect can be detected by a magnetic detection sensor.
And selecting signals of a magnetic detection sensor in one or more paths of steel wire rope nondestructive testing devices to perform isochronous sampling, wherein the sampling frequency is fs.
And (3) carrying out digital signal processing on the sampling result, filtering noise by using a Butterworth filter, and subtracting the average value of the whole sampling from the signal to obtain a sampling signal without a direct current component.
After the processing is finished, the waveform of the equal-time sampling result is divided by using a sampling window, and the amplitude range of the strand wave signal is determined. The division principle is that the number of the strand wave periods in each sampling window needs to meet the precision requirement of WVD-Viterbi time frequency analysis.
Judging whether a joint defect signal exists in each sampling window, wherein the judging method comprises the following steps:
1) calculating an extreme point of the signal in the window;
2) making a difference between every two adjacent extreme points, and recording the difference value;
3) comparing the maximum difference with a normal strand wave range, and if the maximum difference is more than two times of the normal strand wave range, judging that xx defect signals exist;
4) EEMD decomposition is carried out on the joint defect signal, and decomposed sub-waveforms are selected according to the formula xx to replace original waveforms.
And performing WVD conversion on each sampling window to obtain a time-frequency distribution diagram of the waveform, extracting a frequency-time variation curve in the time-frequency distribution diagram by using a Viterbi algorithm, and combining the curves of the time-frequency windows together according to a time relation to form a time-frequency curve of the complete sampling signal.
The wire strand pitch is X and the instantaneous frequency for the ith isochronous sampling point is f i And the distance from the ith sampling point to the starting point of the steel wire rope can be obtained as follows:
according to the method for positioning the defect of the steel wire rope without the position sensor, provided by the invention, the isochronous sampling signal is converted into the specific distance information on the steel wire rope, and compared with the traditional equidistant sampling positioning of the encoding wheel, the precision of steel wire rope distance measurement and defect positioning is greatly improved; processing a signal of a magnetic detection sensor to obtain instantaneous frequency information of a strand wave, then obtaining displacement information of each sampling point through conversion, and further determining a physical coordinate of each sampling point; the accuracy of frequency estimation is improved by adopting a WVD and Viterbi combined algorithm; by adopting isochronous sampling, no information is lost on a time axis; and the EEMD method is used for eliminating joint tangent signals, so that the influence of defect signals with large energy on data processing is avoided. The existing conditions are utilized, and the accuracy of distance measurement and positioning is greatly improved. The method adopts an off-line working mode, and is suitable for occasions where the flaw detection result of the steel wire rope does not need to be obtained immediately or non-contact sampling is required.
The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, numerous simple deductions or substitutions may be made without departing from the spirit of the invention, which shall be deemed to belong to the scope of the invention.
Claims (9)
1. A method for positioning defects of a steel wire rope without a position sensor is characterized by comprising the following steps:
s1, performing isochronous sampling on the magnetic detection sensor to obtain a strand wave waveform related to the running speed of the steel wire rope;
s2, processing the wave form of the strand to obtain the instantaneous frequency information of the strand of each isochronous sampling point;
s3, processing the instantaneous frequency information of the strand wave according to the wire strand distance to obtain the speed information of each isochronous sampling point;
s4, converting each isochronous sampling point to a corresponding distance position on the steel wire rope by combining the isochronous sampling frequency and the speed information of the sampling point, and realizing the positioning of the defect sampling signal point on the steel wire rope;
in step S1, selecting a magnetic detection sensor signal in one or more paths of steel wire rope nondestructive testing devices to perform isochronous sampling with a sampling frequency fs, performing digital signal processing on the sampling result, filtering noise by a butterworth filter, subtracting the average value of the whole sampling from the signal to obtain a sampling signal without a direct current component, after the processing is completed, segmenting the waveform of the isochronous sampling result by using a sampling window, and determining the amplitude range of a strand wave signal, wherein the segmentation principle is that the number of strand wave cycles in each sampling window needs to meet the precision requirement of the viterbi algorithm optimized wiener distribution time-frequency analysis, and judging whether a joint defect signal exists in each sampling window, and the judgment method comprises the following steps:
1) calculating an extreme point of the signal in the window;
2) making a difference between every two adjacent extreme points, and recording the difference value;
3) comparing the maximum difference with the normal strand wave range, and if the maximum difference is more than twice the normal strand wave range, judging as a joint defect signal;
4) and performing ensemble empirical mode decomposition on the joint defect signals, and selecting decomposed sub-waveforms to replace original waveforms according to a correlation coefficient formula.
2. The method for positioning the defect of the steel wire rope without the position sensor according to claim 1, wherein the method comprises the following steps: in step S2, the viterbi-algorithm-optimized time-frequency analysis of the wiggle waveform is used to obtain the instantaneous frequency information of the wiggle at each isochronous sampling point.
3. The method for positioning the defect of the steel wire rope without the position sensor according to claim 2, wherein the method comprises the following steps: in step S3, the instantaneous strand frequency information of the strand is converted into velocity information based on the wire strand pitch length and the isochronous sampling frequency.
4. The method for locating the defect of the steel wire rope without the position sensor according to claim 3, wherein the method comprises the following steps: in step S4, the displacement of the wire rope at each time is obtained according to the speed information and the sampling time, the isochronous sampling point where the defect is located is determined, and the physical position of the defect on the wire rope is determined according to the displacement.
5. The method for positioning the defect of the steel wire rope without the position sensor according to claim 1, wherein the method comprises the following steps: in step S1, the sampled signal of the magnetic detection sensor is sampled isochronously and stored, and noise and dc components in the sampled signal are filtered out by using a butterworth digital filter and a method of subtracting the mean value of signal segments.
6. The method for locating the defect of the steel wire rope without the position sensor according to claim 1, wherein the method comprises the following steps: between step S1 and step S2, step S10 is performed to determine whether there is a splice defect, and if so, ensemble empirical mode decomposition processing is performed to filter out a defect signal, and the process then proceeds to step S2, and if not, the process proceeds to step S2.
7. The method for locating the defect of the steel wire rope without the position sensor according to claim 6, wherein the method comprises the following steps: in step S10, it is determined whether or not there is a joint defect signal in use using the waveform amplitude information.
8. The method for locating the defect of the steel wire rope without the position sensor according to claim 6, wherein the method comprises the following steps: in step S10, the defect signals are removed by using ensemble empirical mode decomposition, which includes the following steps:
1) performing ensemble empirical mode decomposition on the defect signal segment;
2) determining the wavelet to be selected by using a correlation coefficient formula;
3) the wavelets are synthesized into a new waveform to replace the original defect signal segment.
9. The method for positioning the defect of the steel wire rope without the position sensor according to claim 1, wherein the method comprises the following steps: in step S2, a wigner distribution transform is performed on each sampling window to obtain a time-frequency distribution map of the waveformExtracting a frequency-time variation curve in the time-frequency distribution graph by using a Viterbi algorithm, and combining the curves of all the time-frequency windows together according to a time relationship to form a time-frequency curve of a complete sampling signal; in step S4, the wire strand pitch is X, and the instantaneous frequency for the ith isochronous sampling point is f i And solving the distance from the ith sampling point to the starting point of the steel wire rope as follows:
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