Method for positioning ultrasonic echo time in real-time ultrasonic flaw detection of pipeline

Abstract

The invention discloses a method for positioning ultrasonic echo time in real-time ultrasonic flaw detection of a pipeline. The method comprises the following steps of: 1) acquiring an echo continuous analog signal of amplitude-time coordinates; 2) sampling and converting into echo discrete digital signals; 3) calculating the change rate of the echo discrete digital signal, and generating a change rate data set; 4) calculating the adjacent difference of the change rate data set to generate an adjacent difference data set; 5) finding out the minimum value point of the adjacent difference; 6) taking the time corresponding to the minimum value point of the adjacent difference as the echo time; echo time is accurately positioned and determined, measurement errors caused by an existing method are effectively avoided, and the measurement precision is stably and efficiently improved.

Description

Technical Field

[0001] The invention belongs to the technical field of ultrasonic flaw detection and monitoring, and in particular relates to a method for ultrasonic echo time positioning in real-time ultrasonic flaw detection of pipelines. Background Art

[0002] Ultrasonic flaw detection monitoring uses the waveform information carried by ultrasonic signals when propagating in the target to infer the target structure status. It has the advantages of non-contact, high measurement accuracy, and easy installation and maintenance.

[0003] Ultrasonic echo propagation time refers to the time interval from the ultrasonic transducer at the transmitting end transmitting the signal to the transducer at the receiving end receiving the signal. T is the true ultrasonic echo propagation time, and T' is the actual measured propagation time. Usually, the transmitted signal is a regular waveform (square wave or sine wave, etc.) with a high signal-to-noise ratio, and the sending time is easy to determine. However, due to the noise interference on the ultrasonic propagation path, the signal is not a regular waveform when it arrives. Therefore, it is difficult to locate the signal arrival time, and there will always be a certain deviation between T and T', which causes certain difficulties in measuring the ultrasonic echo propagation time.

[0004] In the prior art, the fundamental wave and the signal can be correlated to obtain the ultrasonic echo arrival time, and the fundamental wave signal used is pre-stored. In addition, there is a threshold method to determine the signal arrival time. When the amplitude of the ultrasonic echo signal exceeds the set threshold and the waveform characteristic point is detected (zero point), the echo signal is considered to have arrived. After correction, the arrival time is obtained as the arrival time corresponding to T'. The significant disadvantage of the threshold method is that due to changes in parameters such as the flow rate, temperature and pressure of the medium in the pipeline, the signal fluctuates greatly, and the noise signal superimposed on the sound wave is prone to false triggering or non-triggering, resulting in large measurement deviations.

[0005] Ultrasonic waves are displayed as sine waves in the amplitude-time coordinates, and each echo generally contains more than 2 cycles of sine waves. The conventional method of reading the position of ultrasonic echoes is to read the time of the location of its peak or trough. However, high-temperature pressure pipelines contain fluids with dynamically changing temperature, pressure, and velocity. The flow state of fluids varies at different flow rates. When the flow rate is low, the fluid particles only move in one dimension along the flow direction, which is manifested as stratified flow called laminar flow. When the flow rate is high, the fluid will have random movements in other non-flow directions, which is manifested as turbulent flow called turbulence. In real-time ultrasonic monitoring of pipelines in use, due to the influence of factors such as the coupling effect between the ultrasonic transmitter and the propagation medium, the propagation direction, and the diffusion of the sound beam, the position of each echo peak is different, which often leads to an error of 1 to 2 sine cycles, which seriously affects the application of ultrasonic waves in the field of precise measurement. Summary of the invention

[0006] The purpose of the invention is to propose a method for ultrasonic echo time positioning in real-time ultrasonic flaw detection of pipelines by analyzing echo signals.

[0007] A method for ultrasonic echo time positioning in real-time ultrasonic flaw detection of pipelines, characterized by comprising the following steps:

[0008] Step 1) obtaining an echo continuous analog signal of amplitude-time coordinates;

[0009] Step 2) converting the sampling into an echo discrete digital signal;

[0010] Step 3) calculating the rate of change of the echo discrete digital signal to generate a rate of change data set;

[0011] Step 4) calculating the adjacent differences of the change rate data set to generate an adjacent difference data set;

[0012] Step 5) Find the minimum value point of adjacent differences;

[0013] Step 6) The time corresponding to the minimum value point of the adjacent differences is taken as the echo time.

[0014] The beneficial effects of the present invention are:

[0015] Compared with the prior art, the present invention designs a method for locating ultrasonic echo time in real-time ultrasonic flaw detection of pipelines. By processing the echo signal to find the peak, the maximum value corresponds to the point where the curvature of the ultrasonic echo changes the most. This position is unique and stable, so the echo time can be accurately located and determined, which can effectively avoid the measurement errors caused by the existing methods and improve the measurement accuracy stably and efficiently. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The flowchart of the method is shown in FIG. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] A method for ultrasonic echo time positioning in real-time ultrasonic flaw detection of pipelines

[0019] It has the following steps:

[0020] 1) Obtaining the echo continuous analog signal of amplitude-time coordinates;

[0021] The ultrasonic flaw detection system includes a controller, a pulse transmitting circuit, a receiving echo circuit, and an analog sampling circuit. The controller is used to control the transmission and reception of pulse signals; the pulse transmitting circuit transmits pulse signals, the ultrasonic wave propagates in the target object, and the ultrasonic wave is reflected at the defect in the target object; the reflected echo propagates to the receiving echo circuit; the receiving echo circuit receives the reflected echo signal and sends it to the analog sampling circuit; the obtained analog electrical signal is sent to the signal conditioning circuit, and is processed by voltage division, biasing, and impedance conversion.

[0022] 2) Convert it into a discrete digital signal through a sampling circuit;

[0023] The analog signal after signal processing is sampled at high speed using an analog-to-digital conversion circuit to collect signal segments for subsequent processing. In order to accurately obtain the echo signal, 1000 discrete digital signals can be triggered to be collected after the pulse signal is transmitted within a certain time range, and the discrete digital signals can be processed subsequently.

[0024] 3) Echo signal preprocessing.

[0025] Ultrasonic echo signals are typical time domain signals. Window average filtering can eliminate burrs and smooth jitter. At the same time, this filtering method will cause the signal amplitude to decrease accordingly, eliminate high-frequency components, and reduce the echo change rate. It is necessary to reasonably select the number of points for moving average filtering. By comparison, 5-point window average filtering can be selected.

[0026] The formula is:

[0027] l[n]=(l[n-2]+l[n-1]+l[n]+l[n+1]++l[n+2]) / 5

[0028] Where l is the amplitude of the signal after filtering, and n is the sequence number in the discrete digital signal.

[0029] After 5-point window average filtering, abnormal jitter signals can be effectively eliminated, and subsequent processing can be performed based on the filtered signals.

[0030] 4) Set the echo search segment, for example, 1000 sampling points. The echo search is to find the maximum peak point. Most of the sampling points are not peak points. Processing all the sampling points will bring unnecessary redundant workload.

[0031] The sampling points are divided into N segments, N can be set to 10 as needed, and the 100 points in each segment are averaged. The averages of each segment are compared to find the maximum average. The 100 points in the segment to which the maximum average belongs are used as the echo search range. This can greatly reduce the workload of peak search calculations, improve the calculation speed, and is more suitable for processing systems with lower computing configurations.

[0032] 5) Calculate the first-order derivative signal of the echo signal within the echo search range.

[0033] The calculation formula is:

[0034] Calculate the rate of change of the amplitude between two adjacent points with respect to time: E n represents the rate of change of the amplitude at the nth point with respect to time, l n represents the amplitude at the nth point, t n Indicates the time at point n; generates the rate of change E n of the dataset.

[0035] 6) Calculate the rate of change E n The difference sequence of the data set.

[0036] Further calculate the change rate E between two adjacent points n difference sequence of , Δ n =E n+1 -E n ,,E n+1 It represents the rate of change of the amplitude at point n+1 with respect to time, E n represents the rate of change of the amplitude at the nth point with respect to time, Δ n is the adjacent difference between the two. Generate Δ n Dataset

[0037] 7) Iterate to find Δ n The minimum point

[0038] 7-1) Δ n All Δ in the dataset n The absolute values ​​of the data are summed and averaged, and the average value is used as the screening threshold;

[0039] 7-2) The absolute value of Δ is greater than the screening threshold n Data is removed from the dataset and the remaining ones form the updated Δ n Dataset, updated Δ n The data set continues to return to 7-1) calculate the average value;

[0040] 7-3) Repeat 7-1) and 7-2) until the updated Δ n The data set contains only one Δ n Data, that is, Δ n The minimum point of .

[0041] This minimum point corresponds to the peak point of the amplitude, and also corresponds to the point where the curvature of the ultrasonic echo changes the most.

[0042] 8) This Δ nThe minimum point of the first-order derivative, that is, the time corresponding to the maximum value of the first-order derivative, is taken as the echo time. Based on the echo time, it is used to calculate the spatial distance parameter of the defect in the target object represented by the ultrasonic echo.

[0043] Finally, it should be noted that the above description is only an explanation of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail, those skilled in the art can still modify the technical solutions described above or replace some of the technical features with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for ultrasonic echo time positioning in real-time ultrasonic flaw detection of pipelines, characterized in that: The steps are as follows: Step 1) obtaining an echo continuous analog signal of amplitude-time coordinates; Step 2) converting the sampling into an echo discrete digital signal; Step 3) calculating the rate of change of the echo discrete digital signal to generate a rate of change data set; Step 4) calculating the adjacent differences of the change rate data set to generate an adjacent difference data set; Step 5) Find the minimum value point of adjacent differences; Step 6) The time corresponding to the minimum value point of the adjacent differences is taken as the echo time.

2. The method for ultrasonic echo time positioning in real-time ultrasonic flaw detection of pipelines according to claim 1, characterized in that , Step 3) also includes selecting window average filtering to pre-process the echo discrete digital signal.

3. The method for ultrasonic echo time positioning in real-time ultrasonic flaw detection of pipelines according to claim 2 is characterized in that , Step 3) also includes setting echo search segments; dividing all sampling points into N segments, calculating the mean of the points in each segment, comparing the mean of each segment to find the maximum mean, and taking the points in the segment to which the maximum mean belongs as the echo search range.

4. The method for ultrasonic echo time positioning in real-time ultrasonic flaw detection of pipelines according to claim 1, characterized in that ,In step 3), calculate the rate of change of the amplitude between two adjacent points with respect to time: E n represents the rate of change of the amplitude at the nth point with respect to time, l n represents the amplitude at the nth point, t n represents the time at point n, l n+1 represents the amplitude at the n+1th point, t n+1 Indicates the time at point n+1; generates the rate of change E n of the dataset.

5. The method for ultrasonic echo time positioning in real-time ultrasonic flaw detection of pipelines according to claim 1, characterized in that , in step 4), calculate the rate of change E between two adjacent points n difference sequence, Δ n =E n+1 -E n , E n+1 It represents the rate of change of the amplitude at point n+1 with respect to time, E n represents the rate of change of the amplitude at the nth point with respect to time, Δ n is the adjacent difference between the two; generate Δ n of the dataset.

6. The method for ultrasonic echo time positioning in real-time ultrasonic flaw detection of pipelines according to claim 5, characterized in that , in step 5), Iterate to find Δ n The minimum point 5-1) Δ n All Δ in the dataset n The absolute values ​​of the data are summed and averaged, and the average value is used as the screening threshold; 5-2) The absolute value of Δ is greater than the screening threshold n Data is removed from the dataset and the remaining ones form the updated Δ n Dataset, updated Δ n The data set continues to return to 5-1) calculate the average value; 5-3) Repeat 5-1) and 5-2) until the updated Δ n The data set contains only one Δ n Data, that is, Δ n The minimum point of .

7. The method for ultrasonic echo time positioning in real-time ultrasonic flaw detection of pipelines according to claim 2, characterized in that ,Window average filter selects 5-point window average filter; The formula is: l[n]=(l[n-2]+l[n-1]+l[n]+l[n+1]++l[n+2]) / 5 Where l is the amplitude of the signal after filtering, and n is the sequence number in the discrete digital signal.

8. The method for ultrasonic echo time positioning in real-time ultrasonic flaw detection of pipelines according to claim 1, characterized in that ,In step 1), the echo receiving circuit receives the reflected echo signal and sends it to the analog sampling circuit; the obtained analog electrical signal is sent to the signal conditioning circuit and processed by voltage division, biasing and impedance conversion.

9. The method for ultrasonic echo time positioning in real-time ultrasonic flaw detection of pipelines according to claim 1, characterized in that ,In step 2), the analog signal after signal processing is subjected to high-speed digital sampling using an analog-to-digital conversion circuit.

10. The method for ultrasonic echo time positioning in real-time ultrasonic flaw detection of pipelines according to claim 9, characterized in that ,Within a certain time range, 1000 discrete digital signals are collected after the pulse signal is transmitted.

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