CN112902821A - Method for measuring lay length on line and evaluating health state of steel wire rope according to lay length - Google Patents
Method for measuring lay length on line and evaluating health state of steel wire rope according to lay length Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 171
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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
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Abstract
本发明公开了一种在线测量捻距并依此评估钢丝绳健康状态的方法，先安装旋转编码器并初始化，再多次采集钢丝绳的漏磁信号，并通过漏磁信号获取钢丝绳在自检模式和评估模式下的捻距函数，完成钢丝绳捻距的在线测量，最后计算捻距函数变化的特征值，并以此评估钢丝绳当前健康状态，这样在线监测钢丝绳的捻距变化情况，提高钢丝绳使用的安全水平。
The invention discloses a method for measuring the lay length on-line and evaluating the health state of the steel wire rope accordingly. First, a rotary encoder is installed and initialized, then the magnetic flux leakage signal of the steel wire rope is collected for many times, and the self-checking mode and The lay length function in the evaluation mode, completes the online measurement of the lay length of the wire rope, and finally calculates the eigenvalues of the change of the lay length function, and then evaluates the current health status of the wire rope, so as to monitor the change of the lay length of the wire rope online and improve the safety of the use of the wire rope. Level.
Description
Technical Field
The invention belongs to the technical field of wire rope lay length measurement, and particularly relates to a method for measuring the lay length on line and evaluating the health state of a wire rope according to the lay length.
Background
The lay length is an important process parameter for manufacturing the steel wire rope and is also an important process index and detection index of the steel wire rope. When the steel wire rope is manufactured, the take-up speed is unstable, the early twist and the lay length are not uniform, and the twist and twist reduction phenomenon, lantern shape, kink, strand loosening, abrasion, corrosion, deformation and other damages are caused by the rotation of a suspended heavy object in the using process, so that the lay length of different parts of the steel wire rope can be changed. The uneven lay length of the steel wire rope and the deviation of the designed lay length can cause the uneven distribution of the stress load of the steel wire rope, and the different bearing tension of each strand in the rope can degrade the performance of the steel wire rope, greatly shorten the residual service life of the steel wire rope and cause the early scrapping of the steel wire rope.
At present, a unified standard for detecting the lay length of the steel wire rope is lacked in China. However, in the national standard of GBT 5972-. In which it is explicitly stated: the twist makes the lay length of the steel wire rope uneven, which causes excessive abrasion, and the strength of the steel wire rope is greatly reduced due to serious distortion. Provision is made for: the rejection criteria "kinked wire rope should be rejected immediately". These criteria define the necessity of detecting the lay length of the steel cord. However, the lay length is used as an important structural parameter of the steel wire rope, the change influence of the lay length is more than reflected in the deformation and damage of the steel wire rope, and the change influence influences the load distribution in the rope during bearing, so that the service life consumption of the steel wire rope is accelerated. However, the current steel wire rope nondestructive testing device mainly aims at the surface local damage and the metal cross section loss of the steel wire rope, and cannot simultaneously carry out lay length detection.
At present, the lay length of the steel wire rope is measured by manually using a vernier caliper, or the surface texture of the steel wire rope is rubbed by white paper, and the lay length measurement is realized by measuring the rubbed texture. The other means is to photograph the surface of the steel wire rope by using a camera and measure the lay length by using a machine vision-based algorithm.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a method for measuring the lay length on line and evaluating the health state of a steel wire rope according to the lay length, wherein the lay length of the steel wire rope is measured on line and automatically, and the health state of the steel wire rope is judged according to the lay length.
In order to achieve the above object, the present invention provides a method for measuring lay length on line and estimating the health status of a steel wire rope, comprising the steps of:
(1) installing a rotary encoder and initializing;
fixing the mounting position of the rotary encoder and setting the iso-spatial sampling rate f of the rotary encodersUnit sample points per meter (in/m);
(2) collecting a magnetic leakage signal of a steel wire rope self-inspection mode;
the steel wire rope is firstly operated for a whole round trip period, and M paths of Hall sensors are used for sampling at equal space sampling rate fsRepeatedly collecting leakage magnetic field signals of the self-checking mode of the space around the steel wire rope twice, and recording the leakage magnetic field signals
In the formula, the forward detection signal is represented as
The reverse detection signal is recorded as
Wherein M is 1,2, …, M represents the number of channels, N is 1,2, …, and N represents the length of the collected signal;
(3) estimating an effective lay length function according to a magnetic leakage signal of the steel wire rope self-inspection mode;
(3.1) pair
Removing trend;
using a multi-dimensional variational modal decomposition algorithm pair
Carrying out mode decomposition, wherein the dimension of the decomposition is the number of signal channels M, the number of the decomposed mode components is more than 4, removing the first component after the decomposition is finished, and then carrying out mode decomposition on the first componentSumming other components to obtain each path of detrended leakage magnetic signal, and recording as
(3.2) obtaining an optimal selection strand wave signal;
computing
Each path of characteristic value of (1) comprises a root mean square value RMS, a Kutrosis and a peak factor C;
substituting the above characteristic values into a spike intensity characterization function f (RMS, C, Kutrosis) ═ a1×RMS+a2×C-a3X Kutrosis and solved, wherein, a1、a2、a3Obtaining the characteristic function value of the strand wave intensity of each XD (m, n) for a given coefficient, and then taking the signal of the channel where the maximum value of the characteristic function value of the strand wave intensity is as the optimal strand wave signal which is recorded as the optimal strand wave signal
(3.3) windowing the optimal selection strand wave signal;
to pair
Gaussian window function with sliding window
The window length being at least ten wave lengths, i.e.
In the formula, winL represents the window length, H represents the lay length of the steel wire rope, and B represents the number of strands of the steel wire rope;
(3.4), Fourier transform;
after being respectively windowed
Fourier transform to obtainTime-frequency diagram of short-time Fourier transform, noted as
The size F × N, F is 1,2, …, F is the frequency dimension;
(3.5) calculating a redistributor;
using initial redistributors to divide the time-frequency diagrams
The first difference of the unwinding phase angle of each frequency vector, i.e.
Calculation of where unwarp [. cndot]Indicating uncoiling and indicating a phase angle;
iterative computation redistributor
J is 1,2.. J, and J is the number of compression times, and the redistributor is finally obtained after iteration is finished
(3.6) use of the redistributor pairs
Carrying out redistribution;
will be provided with
Is carried into the redistributor
To redistribute, i.e.
Thereby obtaining a high-resolution time-frequency diagram
(3.7) searching an instantaneous strand frequency function by using a greedy algorithm;
setting the length of a forward window and a backward window of a greedy algorithm for forward and backward windowing, and then setting a high-resolution time-frequency graph
Using a greedy algorithm of windowing from front to back, finding a continuously-changing instantaneous strand wave frequency function with the maximum amplitude value, and recording the function as
Solving instantaneous frequency function
First order difference of
If it is
g is given frequency jump threshold, the curve is discarded and
zero all data for this curve; then the window length in the forward and backward directions is doubled, and the greedy algorithm with the window length in the forward and backward directions is used again to search the instantaneous frequency function again
And analogizing until finding the curve meeting the condition;
(3.8) obtaining a lay length function of the steel wire rope in the forward detection process as
The unit meter per twist (m/twist), the number of strands B per twist (strand/twist), and the instantaneous strand wave frequency
Unit strand per meter (strand/m);
(3.9) similarly, according to the method in the steps (3.1) - (3.8), according to the leakage magnetic signal of the steel wire rope self-checking mode
Estimating the lay length function in reverse detection of steel wire ropes
(3.10) obtaining an effective lay length function H of a steel wire rope self-checking mode0(n)
Function of lay length
Is turned over left and right to obtain
n＝N,N-1,...1；
Will be provided with
And
making a difference, and then taking an absolute value to obtain
If epsilonH(n)＞d1In the formula, d1If the error threshold is given, the rotary encoder is not normally operated, the installation position of the rotary encoder is replaced, and the step (2) is returned; otherwise, the lay length function of the condition will be satisfied
Effective lay length function H recorded as steel wire rope self-checking mode0(n)；
(4) Acquiring a magnetic flux leakage signal of the steel wire rope in an evaluation mode;
in steelAfter the wire rope works and is used for a period of time, acquiring a magnetic flux leakage signal in a wire rope evaluation mode according to the method in the step (2), and recording the magnetic flux leakage signal as
And
i is 1,2, …, I represents the number of detections during the use of the steel wire rope;
(5) calculating a lay length function of the steel wire rope in the evaluation mode;
according to the method in the step (3), magnetic flux leakage signals under the steel wire rope evaluation mode
And
estimating a lay length function H of the steel wire rope in an evaluation modei(n)；
(6) Calculating a characteristic value of the change of the lay length function;
(6.1) calculating a lay length function H in a self-checking mode0Characteristic values of (n), including mean values
Variance (variance)
Kurtosis K0；
(6.2) calculating a lay length function H in an evaluation modeiCharacteristic values of (n), including mean values
Variance (variance)
Kurtosis Ki；
(6.3) for the steel wire rope lay length function H in the evaluation modei(n) plus a sliding window, the window length of which is longDegree being an odd number of at least 2 strand lengths, i.e.
Obtaining a windowed lay length sequence
(6.4) respectively calculating the characteristic values of the health state of the windowed twist pitch sequence, wherein the characteristic values comprise a mean value, a standard deviation, a skewness and a kurtosis; thereby obtaining a windowed mean sequence
Windowed standard deviation sequence
Windowing skewness sequence
Windowed kurtosis sequence
(7) Evaluating the health state of the steel wire rope;
(7.1) if window mean sequence variation range
And the maximum value of the absolute value of the windowed skewness sequence
In the formula, epsilon0And ε1If the positive threshold value is given, the problem of twisting and untwisting of the steel wire rope is judged to be absent;
if windowed mean sequence
In which there are successive y elements
Or there are y consecutive elements in the windowed skewness sequence
In the formula, y is more than or equal to 3 multiplied by span, the twisting problem exists in the part of the steel wire rope;
if windowed mean sequence
In which there are successive y elements
Or there are y consecutive elements in the windowed skewness sequence
The part of the steel wire rope has the problem of untwisting;
(7.2) for initial detection lay length function H0(n) and in-use lay length function Hi(n) bringing them into the pitch ripple function
Solving if the pitch ripple function
In the formula, h is a given coefficient, the uneven load distribution degree exceeds the requirement when the steel wire rope is loaded, and the lay length distribution range exceeds the allowable range;
(7.3), four windowed eigenvalue sequences: mean value
Standard deviation of
Deflection degree
And kurtosis
If a certain characteristic value sequence has mutation, the pitch mutation function consisting of first-order difference of each characteristic value sequence
In the formula, epsilon2If the threshold value is given, judging that the lay length of the steel wire rope is locally abnormal and the performance degradation trend exists;
(7.4) measuring data H for different periods of time0(n) and Hi(n) average value, calculating the average elongation of the steel wire rope lay length
In the formula, LiThe length L of the steel wire rope is measured by a rotary encoder during the ith measurement0When the self-checking mode is adopted, the length of the steel wire rope is measured by a rotary encoder; if the elongation delta > epsilon3In the formula, epsilon3If the elongation rate is the threshold value of the elongation rate of the steel wire rope, the elongation rate of the steel wire rope is considered to exceed the requirement;
the invention aims to realize the following steps:
the invention relates to a method for measuring the lay length on line and evaluating the health state of a steel wire rope according to the lay length, which comprises the steps of firstly installing a rotary encoder and initializing, then collecting magnetic leakage signals of the steel wire rope for multiple times, obtaining the lay length function of the steel wire rope in a self-checking mode and an evaluation mode through the magnetic leakage signals, completing the on-line measurement of the lay length of the steel wire rope, finally calculating the characteristic value of the change of the lay length function, and evaluating the current health state of the steel wire rope according to the characteristic value, thereby monitoring the change condition of the lay length of the steel wire rope on line and.
Meanwhile, the method for measuring the lay length on line and evaluating the health state of the steel wire rope further has the following beneficial effects:
(1) the invention can measure the lay length of the steel wire rope with high precision and no damage only by the self characteristic of the magnetic leakage signal, realizes the online measurement of the lay length of the steel wire rope, does not change the hardware structure of the traditional steel wire rope local defect detector, does not increase the cost, does not change the device and has the characteristic of low cost;
(2) the invention is not influenced by vibration noise between the steel wire rope and the detector and the defect noise of the steel wire rope, accurately measures the lay length of the steel wire rope, resists the strong interference of the defect noise and the vibration noise, and has good accuracy and stability;
(3) the method can automatically eliminate the unstable working data of the rotary encoder, can detect the abnormal and worsening trend of the lay length of each part of the steel wire rope, and simultaneously realizes the analysis and prejudgment of the local and global health states of the steel wire rope.
Drawings
FIG. 1 is a flow chart of a method of the present invention for measuring lay length on-line and assessing the health of a steel cord accordingly;
FIG. 2 is a schematic diagram of a steel wire rope magnetic flux leakage signal measuring device;
FIG. 3 is a schematic view of a rotary encoder installation;
FIG. 4 is a schematic diagram of a leakage flux signal of a steel wire rope;
fig. 5 is a schematic illustration of the lay length and strand spacing of a steel cord.
Detailed Description
The following description of the embodiments of the present invention is provided in order to better understand the present invention for those skilled in the art with reference to the accompanying drawings. It is to be expressly noted that in the following description, a detailed description of known functions and designs will be omitted when it may obscure the subject matter of the present invention.
Examples
Fig. 1 is a flow chart of a method for on-line measuring lay length and estimating the health of a steel wire rope according to the invention.
In this embodiment, as shown in fig. 2, the measuring device for estimating a wire breakage of a steel wire rope according to the present invention includes a magnetic loop composed of a permanent magnet, a magnetic yoke, and a steel wire rope, and M ═ 20 hall sensors located in the middle of a detecting instrument are annularly arranged around the axis of the steel wire rope at equal angles. As shown in fig. 1, the method for online measuring the lay length by the leakage magnetic signal and accordingly evaluating the health state of the steel wire rope comprises the following steps:
s1, installing a rotary encoder and initializing;
fixing the mounting position of the rotary encoder and setting the iso-spatial sampling rate f of the rotary encodersUnit sample points per meter (in/m);
in this embodiment, the installation position of the rotary encoder directly affects the accuracy of the isometric sampling pulse, as shown in fig. 3, under the condition that the conditions allow, the rotary encoder is preferentially installed on the steel wire rope head sheave, the main guide wheel or the fixed pulley, such as the installation positions 1 and 2 of the rotary encoder, so as to ensure the accuracy of the isometric sampling; if the conditions do not allow, the cable is installed on the steel cable, as in position 3. Attention must be paid to pure rolling between a friction wheel for driving the rotary encoder and a steel wire rope, and relative sliding is avoided, so that the accuracy of displacement information is guaranteed, and accurate equal-space sampling pulses are output.
S2, collecting a magnetic flux leakage signal of the steel wire rope self-checking mode;
the steel wire rope is firstly operated for a whole round trip period, and 20 paths of Hall sensors are used for sampling at an equal space sampling rate fsRepeatedly collecting leakage magnetic field signals of the self-checking mode of the space around the steel wire rope twice, and recording the leakage magnetic field signals
In the formula, the forward detection signal is represented as
The reverse detection signal is recorded as
Wherein M is 1,2, …, M represents the number of channels, N is 1,2, …, and N represents the length of the collected signal;
s3, estimating an effective lay length function according to the magnetic leakage signal of the steel wire rope self-checking mode;
s3.1, pair
Removing trend;
as shown in fig. 4, the data is the magnetic flux leakage signal data of a certain wire rope portion, wherein the ordinate is the output voltage of the hall sensor, and the abscissa is the detection distance. In the figure, one of 20 leakage magnetic signals has obvious nonlinear trend terms. Therefore, the magnetic leakage signal needs to be subjected to detrending processing, and the specific process is as follows:
using a multi-dimensional variational modal decomposition algorithm pair
Carrying out mode decomposition, wherein the dimension of the decomposition is the number of signal channels M, the number of the decomposed mode components is more than 4, removing the first term component after the decomposition is finished, summing other term components to obtain each path of trend-removed leakage magnetic signals, and recording the trend-removed leakage magnetic signals as the leakage magnetic signals
S3.2, obtaining an optimal selection strand wave signal;
computing
Each path of characteristic value of (1) comprises a root mean square value RMS, a Kutrosis and a peak factor C;
substituting the above characteristic values into a spike intensity characterization function f (RMS, C, Kutrosis) ═ a1×RMS+a2×C-a3X Kutrosis and solved, wherein, a1、a2、a3Obtaining the characteristic function value of the strand wave intensity of each XD (m, n) for a given coefficient, and then taking the signal of the channel where the maximum value of the characteristic function value of the strand wave intensity is as the optimal strand wave signal which is recorded as the optimal strand wave signal
S3.3, windowing the optimal selection strand wave signal;
to pair
Gaussian window function with sliding window
The window length being at least ten wave lengths, i.e.
In the formula, winL represents the window length, H represents the lay length of the steel wire rope, and B represents the number of strands of the steel wire rope;
s3.4, Fourier transform;
after being respectively windowed
Performing Fourier transform to obtain a time-frequency diagram of short-time Fourier transform, and recording the time-frequency diagram as
The size F × N, F is 1,2, …, F is the frequency dimension;
s3.5, calculating a redistributor;
using initial redistributors to divide the time-frequency diagrams
The first difference of the unwinding phase angle of each frequency vector, i.e.
Calculation of where unwarp [. cndot]Indicating uncoiling and indicating a phase angle;
iterative computation redistributor
J is the number of compression, generally, J is 7, and the redistributor is finally obtained after the iteration is completed
S3.6, using heavy distributor pairs
Carrying out redistribution;
will be provided with
Is carried into the redistributor
To redistribute, i.e.
Thereby obtaining a high-resolution time-frequency diagram
S3.7, searching an instantaneous strand wave frequency function by using a greedy algorithm;
setting the length of a forward window and a backward window of a greedy algorithm for forward and backward windowing, and then setting a high-resolution time-frequency graph
Using a greedy algorithm of windowing from front to back, finding a continuously-changing instantaneous strand wave frequency function with the maximum amplitude value, and recording the function as
K is 1,2, …, M is the total number of instantaneous strand wave frequency functions; solving instantaneous frequency function
First order difference of
If it is
g is given frequency jump threshold, the curve is discarded and
zero all data for this curve; then the length of the window in the front-back direction is doubled, and the greedy calculation of adding the window in the front-back direction is used againMethod for re-searching instantaneous frequency function
And analogizing until finding the curve meeting the condition;
s3.8, obtaining a lay length function of the steel wire rope during forward detection as
The unit meter per twist (m/twist), the number of strands B per twist (strand/twist), and the instantaneous strand wave frequency
Unit strand per meter (strand/m);
in this embodiment, the strand pitch is the reciprocal of the instantaneous strand wave frequency, and the lay length is the product of the number of strands of the steel cord and the strand pitch, as shown in fig. 5, the number of strands of the steel cord is 6, and the lay length is 6 times the strand gap.
S3.9, and similarly, according to the method of the steps S3.1 to S3.8, according to the magnetic leakage signal of the steel wire rope self-checking mode
Estimating the lay length function in reverse detection of steel wire ropes
S3.10, obtaining an effective lay length function H of a steel wire rope self-checking mode0(n)；
Function of lay length
Is turned over left and right to obtain
n＝N,N-1,...1；
Will be provided with
And
making a difference, and then taking an absolute value to obtain
If epsilonH(n)＞d1In the formula, d1If the error threshold is set, indicating that the rotary encoder is not working properly, the mounting position of the rotary encoder is changed, and the process returns to step S2; otherwise, the lay length function of the condition will be satisfied
Effective lay length function H recorded as steel wire rope self-checking mode0(n)；
In the step, the same steel wire rope is repeatedly measured twice in a reciprocating way, the relative error of repeated measurement is judged, the accuracy and the stability of the measurement result are ensured, and the influence of improper operation or abnormal work of a rotary encoder is eliminated; in this step, it should be noted that the starting point and the ending point of the two measurements need to be the same.
S4, acquiring a steel wire rope magnetic flux leakage signal in an evaluation mode;
after the steel wire rope works and uses for a period of time, acquiring a magnetic flux leakage signal under the steel wire rope evaluation mode according to the method in the step S2, and recording the magnetic flux leakage signal as
And
i is 1,2, …, I represents the number of detections during the use of the steel wire rope;
in this embodiment, after the steel wire rope works for a period of time, two modes of off-line detection and on-line detection can be adopted, wherein the off-line detection comprises: setting fixed time periods according to related production safety requirements, running the steel wire rope to and fro in the whole process every fixed time period, and acquiring and recording whole-process data, such as a shutdown acquisition signal every week for fixed time; online detection: in the using process of the steel wire rope, whether the steel wire rope has the condition of the sudden change of the lay length or the uneven load distribution is judged according to the collected signals, if the health state of the steel wire rope is deteriorated, the detection times are increased, the detection time interval is reduced, or the magnetic flux leakage signals of the steel wire rope are continuously collected, and the lay length characteristics and the load distribution of the steel wire rope are detected on line and analyzed synchronously.
S5, calculating a lay length function of the steel wire rope in the evaluation mode;
according to the method of step S3, the leakage flux signal is evaluated according to the steel wire rope under the mode
And
estimating a lay length function H of the steel wire rope in an evaluation modei(n)；
S6, calculating a characteristic value of the change of the lay length function;
s6.1, calculating a lay length function H in a self-checking mode0Characteristic values of (n), including mean values
Variance (variance)
Kurtosis K0；
S6.2, calculating a lay length function H in an evaluation modeiCharacteristic values of (n), including mean values
Variance (variance)
Kurtosis Ki；
S6.3, evaluating the function H of the lay length of the steel wire rope in the modei(n) plus a sliding window having a window length of at least an odd number of 2 beam lengths, i.e.
To obtain aWindow lay length sequence
S6.4, respectively calculating the characteristic values of the health state of the windowed twist pitch sequence, wherein the characteristic values comprise a mean value, a standard deviation, a skewness and a kurtosis; thereby obtaining a windowed mean sequence
Windowed standard deviation sequence
Windowing skewness sequence
Windowed kurtosis sequence
S7, evaluating the health state of the steel wire rope;
s7.1, if window mean sequence change interval range
And the maximum value of the absolute value of the windowed skewness sequence
In the formula, epsilon0And ε1If the positive threshold value is given, the problem of twisting and untwisting of the steel wire rope is judged to be absent;
if windowed mean sequence
In which there are successive y elements
Or there are y consecutive elements in the windowed skewness sequence
In the formula, y is more than or equal to 3 multiplied by span, the twisting problem exists in the part of the steel wire rope;
if windowed mean sequence
In which there are successive y elements
Or there are y consecutive elements in the windowed skewness sequence
The part of the steel wire rope has the problem of untwisting;
however, the higher the twisting and detwisting degree is, the more the steel wire rope lay length deviates from the normal designed lay length, the more uneven the distribution of the stress load of the steel wire rope is, and the accelerated consumption of the residual service life of the steel wire rope is;
s7.2, for initial detection of lay length function H0(n) and healthy State lay Length function Hi(n) bringing them into the pitch ripple function
Solving if the pitch ripple function
In the formula, h is a given coefficient, the distribution range of the lay length of the steel wire rope is considered to exceed the allowable range, and the uneven degree of load distribution during bearing exceeds the requirement;
the higher the fluctuation degree of the lay length of the steel wire rope, the more uneven the stress of each part of the steel wire rope during bearing, and the earlier scrapping of the steel wire rope can be caused;
s7.3, four windowing characteristic value sequences: mean value
Standard deviation of
Deflection degree
And kurtosis
If a certain characteristic value sequence has mutation, the pitch mutation function consisting of first-order difference of each characteristic value sequence
In the formula, epsilon2If the threshold value is given, judging that the lay length of the steel wire rope is locally abnormal and the performance degradation trend exists;
the local sudden change of the lay length of the steel wire rope means that the steel wire rope has local damage such as lantern shape, kink, strand looseness, corrosion, deformation and the like, and the specific damage type and the severity are judged according to the steel wire rope;
s7.4, detecting data H for different time periods0(n) and Hi(n) average value, calculating the average elongation of the steel wire rope lay length
In the formula, LiThe length L of the steel wire rope is measured by a rotary encoder during the ith detection0Detecting the length of the steel wire rope by a rotary encoder in a self-checking mode; if the elongation delta > epsilon3In the formula, epsilon3If the elongation rate is the threshold value of the elongation rate of the steel wire rope, the elongation rate of the steel wire rope is considered to exceed the requirement;
when the rotary encoder can output equal space pulse and detection distance information, the rotary encoder is preferentially used for measuring the length of the steel wire rope to calculate the average elongation rate of the lay length, and the average elongation rate of the lay length of the steel wire rope is checked with the average elongation rate of the lay length calculated by the mean value of the lay length function; and when the encoder is not selected to detect the distance information, calculating the average elongation of the lay length of the steel wire rope by using the mean value of the lay length function.
Although illustrative embodiments of the present invention have been described above to facilitate the understanding of the present invention by those skilled in the art, it should be understood that the present invention is not limited to the scope of the embodiments, and various changes may be made apparent to those skilled in the art as long as they are within the spirit and scope of the present invention as defined and defined by the appended claims, and all matters of the invention which utilize the inventive concepts are protected.
Claims (2)
1. A method for measuring the lay length on line and evaluating the health state of a steel wire rope according to the lay length on line is characterized by comprising the following steps:
(1) installing a rotary encoder and initializing;
fixing the mounting position of the rotary encoder and setting the iso-spatial sampling rate f of the rotary encodersUnit sampling point per meter (pieces/m);
(2) collecting a magnetic leakage signal of a steel wire rope self-inspection mode;
the steel wire rope is firstly operated for a whole round trip period, and M paths of Hall sensors are used for sampling at equal space sampling rate fsRepeatedly collecting leakage magnetic field signals of the self-checking mode of the space around the steel wire rope twice, and recording the leakage magnetic field signals
In the formula, the forward detection signal is represented as
The reverse detection signal is recorded as
Wherein M is 1,2, …, M represents the number of channels, N is 1,2, …, and N represents the length of the collected signal;
(3) estimating an effective lay length function according to a magnetic leakage signal of the steel wire rope self-inspection mode;
(3.1) pair
Removing trend;
using a multi-dimensional variational modal decomposition algorithm pair
Carrying out mode decomposition, wherein the dimension of the decomposition is the number of signal channels M, the number of the decomposed mode components is more than 4, removing the first term component after the decomposition is finished, summing other term components to obtain each path of trend-removed leakage magnetic signals, and recording the trend-removed leakage magnetic signals as the leakage magnetic signals
(3.2) obtaining an optimal selection strand wave signal;
computing
Each path of characteristic value of (1) comprises a root mean square value RMS, a Kutrosis and a peak factor C;
substituting the above characteristic values into a spike intensity characterization function f (RMS, C, Kutrosis) ═ a1×RMS+a2×C-a3X Kutrosis and solved, wherein, a1、a2、a3Obtaining the characteristic function value of the strand wave intensity of each XD (m, n) for a given coefficient, and then taking the signal of the channel where the maximum value of the characteristic function value of the strand wave intensity is as the optimal strand wave signal which is recorded as the optimal strand wave signal
(3.3) windowing the optimal selection strand wave signal;
to pair
Gaussian window function with sliding window
The window length being at least ten wave lengths, i.e.
In the formula, winL represents the window length, H represents the designed lay length of the steel wire rope, and B represents the number of strands of the steel wire rope;
(3.4), Fourier transform;
after being respectively windowed
Performing Fourier transform to obtain a time-frequency diagram of short-time Fourier transform, and recording the time-frequency diagram as
The size F × N, k is 1,2, …, F is the frequency dimension;
(3.5) calculating a redistributor;
using initial redistributors to divide the time-frequency diagrams
The first difference of the unwinding phase angle of each frequency vector, i.e.
Calculation of where unwarp [. cndot]Indicating uncoiling and indicating a phase angle;
iterative computation redistributor
J is 1,2.. J, and J is the number of compression times, and the redistributor is finally obtained after iteration is finished
(3.6) use of the redistributor pairs
Performing redistribution
Will be provided with
Is carried into the redistributor
To redistribute, i.e.
Thereby obtaining a high-resolution time-frequency diagram
(3.7) searching an instantaneous strand frequency function by using a greedy algorithm;
setting the length of a forward window and a backward window of a greedy algorithm for forward and backward windowing, and then setting a high-resolution time-frequency graph
Using a greedy algorithm of windowing from front to back, finding a continuously-changing instantaneous strand wave frequency function with the maximum amplitude value, and recording the function as
Solving instantaneous frequency function
First order difference of
If it is
g is given frequency jump threshold, the curve is discarded and
zero all data for this curve; then the window length in the forward and backward directions is doubled, and the greedy algorithm with the window length in the forward and backward directions is used again to search the instantaneous frequency function again
And analogizing until finding the curve meeting the condition;
(3.8) obtaining a lay length function of the steel wire rope in the forward detection process as
The unit meter per twist (m/twist), the number of strands B per twist (strand/twist), and the instantaneous strand wave frequency
Unit strand per meter (strand/m);
(3.9) similarly, according to the method in the steps (3.1) - (3.8), according to the leakage magnetic signal of the steel wire rope self-checking mode
Estimating the lay length function in reverse detection of steel wire ropes
(3.10) obtaining an effective lay length function H of a steel wire rope self-checking mode0(n)；
Function of lay length
Is turned over left and right to obtain
Will be provided with
And
making a difference, and then taking an absolute value to obtain
If epsilonH(n)＞d1In the formula, d1Indicating a rotation for a given error thresholdIf the encoder does not work normally, replacing the mounting position of the rotary encoder, and returning to the step (2); otherwise, the lay length function of the condition will be satisfied
Effective lay length function H recorded as steel wire rope self-checking mode0(n)；
(4) Acquiring a magnetic flux leakage signal of the steel wire rope in an evaluation mode;
after the steel wire rope works and uses for a period of time, acquiring a magnetic flux leakage signal in the steel wire rope evaluation mode according to the method in the step (2), and recording the magnetic flux leakage signal as a magnetic flux leakage signal
And
i represents the number of detections during the use of the steel wire rope;
(5) calculating a lay length function of the steel wire rope in the evaluation mode;
according to the method in the step (3), magnetic flux leakage signals under the steel wire rope evaluation mode
And
estimating a lay length function H of the steel wire rope in an evaluation modei(n)；
(6) Calculating a characteristic value of the change of the lay length function;
(6.1) calculating a lay length function H in a self-checking mode0Characteristic values of (n), including mean values
Variance (variance)
Kurtosis K0；
(6.2) evaluation of calculationLay length function H in estimation modeiCharacteristic values of (n), including mean values
Variance (variance)
Kurtosis Ki；
(6.3) for the steel wire rope lay length function H in the evaluation modei(n) plus a sliding window having a window length of at least an odd number of 2 beam lengths, i.e.
Obtaining a windowed lay length sequence
(6.4) respectively calculating the characteristic values of the health state of the windowed twist pitch sequence, wherein the characteristic values comprise a mean value, a standard deviation, a skewness and a kurtosis; thereby obtaining a windowed mean sequence
Windowed standard deviation sequence
Windowing skewness sequence
Windowed kurtosis sequence
(7) Evaluating the health state of the steel wire rope;
(7.1) if window mean sequence variation range
And the maximum value of the absolute value of the windowed skewness sequence
In the formula, epsilon0And ε1If the positive threshold value is given, the problem of twisting and untwisting of the steel wire rope is judged to be absent;
if windowed mean sequence
In which there are successive y elements
Or there are y consecutive elements in the windowed skewness sequence
In the formula, y is more than or equal to 3 multiplied by span, the twisting problem exists in the part of the steel wire rope;
if windowed mean sequence
In which there are successive y elements
Or there are y consecutive elements in the windowed skewness sequence
The part of the steel wire rope has the problem of untwisting;
(7.2) for initial detection lay length function H0(n) and in-use lay length function Hi(n) bringing them into the pitch ripple function
Solving if the pitch ripple function
Wherein h is givenThe coefficient is that the load distribution unevenness degree exceeds the requirement when the steel wire rope is loaded, and the lay length distribution range exceeds the allowable range;
(7.3), four windowed eigenvalue sequences: mean value
Standard deviation of
Deflection degree
And kurtosis
If a certain characteristic value sequence has mutation, the pitch mutation function consisting of first-order difference of each characteristic value sequence
In the formula, epsilon2If the threshold value is given, judging that the lay length of the steel wire rope is locally abnormal and the performance degradation trend exists;
(7.4) detecting data H for different time periods0(n) and Hi(n) average value, calculating the average elongation of the steel wire rope lay length
In the formula, LiThe length L of the steel wire rope is measured by a rotary encoder during the ith measurement0The length of the steel wire rope is measured by a rotary encoder in a self-checking mode; if the elongation delta > epsilon3In the formula, epsilon3And if the elongation rate is the threshold value of the elongation rate of the steel wire rope, the elongation rate of the steel wire rope is considered to exceed the requirement.
2. A method of on-line measuring lay length and assessing the health of a steel cord as claimed in claim 1, wherein the rotary encoder mounting position priorities are in the order: the steel wire rope comprises a winding drum of the steel wire rope, a head sheave, a main guide wheel and the steel wire rope.
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