Ultrasonic imaging detection method for lead-tin alloy sheath of high-voltage cable terminal

Abstract

The invention discloses an ultrasonic imaging detection method for a lead-tin alloy sheath of a high-voltage cable terminal, and particularly relates to the technical field of ultrasonic imaging detection.The method comprises the steps that deconvolution processing is conducted on received ultrasonic echo signals on the basis of wavelet transformation, the overlapped ultrasonic echo signals can be effectively separated, noise in the signals can be eliminated, and the detection accuracy is improved. After bilinear interpolation is carried out on the generated lead-tin alloy sheath ultrasonic image, binarization processing is carried out to segment the image, the defect area is calculated after segmentation is completed, and then defect position information and the defect area are sent to a high-voltage cable terminal management center, so that high-precision positioning of defects can be realized; according to the evaluation method for the ultrasonic imaging detection quality control effect, ultrasonic echo signal de-noising data, ultrasonic image data and defect detection data in an ultrasonic imaging detection task period are collected, then ultrasonic imaging detection quality indexes are calculated through a series of processing, and the ultrasonic imaging detection quality can be guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrasonic imaging detection, and more specifically, to an ultrasonic imaging detection method for a lead-tin alloy sheath of a high-voltage cable terminal. Background Art

[0002] Ultrasonic imaging detection is a visual image detection method that uses the propagation characteristics of ultrasonic waves in a medium and uses reflected or transmitted sound waves as information carriers. In recent years, ultrasonic imaging detection technology has made great progress. Compared with other imaging methods such as computer tomography, magnetic resonance imaging, infrared thermal imaging, etc., ultrasonic imaging detection has the advantages of high safety, high speed, and low cost. Therefore, it is widely used in industrial non-destructive testing and medical diagnosis.

[0003] The existing ultrasonic imaging detection system for lead-tin alloy sheath of high-voltage cable terminals analyzes the structural characteristics of high-voltage cable terminals, sets the expected emission-reflection interval time interval based on the thickness and sound velocity of the lead-tin alloy sheath, and based on this, screens the ultrasonic echo signals that are not in this time interval, then directly deconvolutes the ultrasonic echo signals through inverse filtering to generate a full-matrix ultrasonic frequency domain image, performs threshold segmentation, and calculates the area of ​​the defective area.

[0004] However, the existing system still has some problems: setting the expected emission-reflection interval time interval based on the thickness of the lead-tin alloy sheath and the speed of sound and screening the ultrasonic echo signals that are not in this time interval may cause the loss of a large number of target echo signals; directly deconvolving the ultrasonic echo signals through inverse filtering is not very effective in separating the interface echo signals and eliminating noise; and it is difficult to achieve high-precision positioning of defects by performing threshold segmentation after generating a full-matrix ultrasonic frequency domain image, which still needs further improvement. Summary of the invention

[0005] In order to overcome the above-mentioned defects of the prior art, an embodiment of the present invention provides an ultrasonic imaging detection method for a lead-tin alloy sheath of a high-voltage cable terminal to solve the problems raised in the above-mentioned background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for customizing a travel route based on big data, comprising the following steps: S1: After selecting the ultrasonic imaging detection equipment, debug and calibrate the selected equipment, and start the preparation before detection after confirming that the selected equipment is working normally; S2: After the preparatory work before the test is completed, the ultrasonic phased array probe is attached to the outer surface of the high-voltage cable terminal, and ultrasonic scanning detection is performed according to the settings to collect the pulse excitation signal emitted by the phased array ultrasonic transducer and the ultrasonic echo signal received by each array element; S3: performing deconvolution processing on the received ultrasonic echo signal to separate the overlapping ultrasonic echo signals and eliminate the noise in the signal; S4: Reconstruct and focus each set of transmit-receive data based on frequency domain imaging conditions, superimpose the obtained reconstruction results to generate axial full-matrix ultrasonic frequency domain imaging of the lead-tin alloy sheath of the high-voltage cable terminal, and generate circumferential frequency domain synthetic aperture imaging of the lead-tin alloy sheath of the high-voltage cable terminal based on the frequency domain synthetic aperture algorithm; S5: Perform bilinear interpolation on the generated ultrasonic image of the lead-tin alloy sheath and then perform binarization processing to segment the image. After the segmentation is completed, the defect area is calculated, and then the defect location information and defect area are sent to the high-voltage cable terminal management center; S6: Collecting ultrasonic echo signal denoising data, ultrasonic image data and defect detection data within the ultrasonic imaging detection task cycle; S7: Processing the collected ultrasonic echo signal denoising data to calculate the denoising effect coefficient, processing the collected ultrasonic image data to calculate the ultrasonic imaging control reliability coefficient, and processing the collected defect detection data to calculate the defect detection accuracy coefficient; S8: Calculate the average denoising effect index and the average ultrasonic imaging control reliability coefficient respectively, and then evaluate the ultrasonic imaging detection quality based on the average denoising effect index, the average ultrasonic imaging control reliability coefficient and the defect detection accuracy coefficient.

[0007] Preferably, the process of deconvolution processing of the ultrasonic echo signal in step S3 is as follows: S31. Based on signal theory, the ultrasonic echo signal y(t) received by the phased array ultrasonic transducer is expressed as: , x(t) is the ultrasonic signal before entering the high-voltage cable terminal, h(t) is the response of each process experienced by the ultrasonic echo signal when it is reflected back from the high-voltage cable terminal, and n(t) is random noise; S32, calculating the maximum value of the correlation coefficient between the ultrasonic echo signal y(t) and the commonly used wavelet basis function φ(t), and the wavelet basis function corresponding to the obtained result is the target wavelet basis function; S33, after confirming the target wavelet basis function, performing wavelet transform on the ultrasonic echo signal y(t) to obtain sub-band signals located in different frequency bands, calculating the correlation coefficients between an interface echo of the sub-band signals in different frequency bands and the other interface echoes, and then extracting the maximum value, and the interface echo signal of the frequency band sub-band signal corresponding to the maximum value of the rank correlation coefficient is used as a reference signal for Wiener filtering; S34, after Fourier transforming the reference signal, the frequency domain response H(ω) is calculated based on the Wiener filter. The specific formula is: , where X(ω), X * (ω), Y(ω), Q 2They are the Fourier transform of x(t) with respect to t, the conjugate value after the Fourier transform of x(t) with respect to t, the Fourier transform of y(t) with respect to t, and the passivation factor; S35. Perform inverse Fourier transform on the frequency domain response H(ω) to obtain a deconvolution result h(t).

[0008] Preferably, the specific steps of defect detection in step S5 are as follows: S51. Given the coordinates of the interpolation point p(x,z), retrieve the values ​​of the nearest neighbor points of p(x,z) in the negative x direction, positive x direction, negative z direction, and positive z direction in the imaging numerical matrix, respectively, denoted as q 11 (x1,z1),q 21 (x2,z1),q 12 (x1,z2),q 22 (x2, z2), when calculating the value of the interpolation point, first perform linear interpolation in the x direction to calculate the values ​​of p1(x, z1) and p2(x, z2). The specific formula is: , and then perform linear interpolation in the z direction to calculate the value of the interpolation point p (x, z). The specific formula is: ; S52, after the interpolation process is completed, a grayscale threshold is set, pixels greater than the threshold are retained, and pixels less than the threshold are deleted; S53, randomly selecting an edge point of the lead-tin alloy sheath ultrasonic image after binarization as the starting point, setting its gray value for marking, and then searching the eight neighborhoods of the starting point in order from top to bottom and from left to right according to the gray value of the mark, and after finding the next edge point, recording its coordinate value and using it as the new starting point to continue searching, repeating this process until returning to the initial starting point; S54, after obtaining the edge point coordinate set of the lead-tin alloy sheath defect area, record the number of pixels m of the entire image z and the number of pixels in the defect area m q , get the actual area A of the entire image s Then calculate the defect area A q , the specific formula is: ; S55, sending the calculated lead-tin alloy sheath defect area and defect location information to the high-voltage cable terminal management center.

[0009] Preferably, the ultrasonic echo signal denoising data collected in step S6 includes the signal-to-noise ratio and signal variance before each denoising process and the signal-to-noise ratio and signal variance after the denoising process; the ultrasonic image data collected in step S6 includes the axial resolution, time resolution and contrast resolution of each generated ultrasonic image; the defect detection data collected in step S6 includes the number of defects correctly detected, the actual number of defects, the area of ​​each defect detected and the actual area of ​​the detected defects.

[0010] Preferably, the data processing process in step S7 is as follows: S71, calculate the denoising effect coefficient X of the denoising process of the i-th ultrasonic echo signal zi , the specific formula is: , α qi , α hi , σ 2 qi , σ 2 hi They are respectively the signal-to-noise ratio of the i-th ultrasonic echo signal before denoising, the signal-to-noise ratio after denoising, the variance of the signal before denoising, and the variance of the signal after denoising; S72, calculating the ultrasonic imaging control reliability coefficient X of the generated i-th ultrasonic image ci , the specific formula is: ,β zci , β tci , β dci are the actual axial resolution, actual time resolution, and actual contrast resolution of the i-th ultrasound image, β zs , β ts , β ds They are the theoretical axial resolution, theoretical time resolution, and theoretical contrast resolution of ultrasound images, respectively. The specific calculation formulas are as follows: , D m is the pulse width, v s is the speed of sound, , f c is the sampling frequency, , I1, I2, σ e They are, in order, the average signal intensity of the defective area of ​​the ultrasonic image of the lead-tin alloy sheath, the average signal intensity of the normal area of ​​the ultrasonic image of the lead-tin alloy sheath, and the standard deviation of the noise in the normal area of ​​the ultrasonic image of the lead-tin alloy sheath; S73. Calculate the defect detection accuracy coefficient X within the ultrasonic imaging detection task cycle u , the specific formula is: , m ra 、m rz , A qi , A ciThey are the number of defects detected correctly, the actual number of defects, the area of ​​the i-th defect detected, and the actual area of ​​the i-th defect detected.

[0011] Preferably, the specific steps of evaluating the ultrasonic imaging detection quality in step S8 are as follows: S81. Calculate the average denoising effect coefficient X zr , the specific formula is: , n a is the number of times the ultrasonic echo signal is de-noised; S82. Calculate the average ultrasonic imaging control reliability coefficient X cr , the specific formula is: , n b is the number of ultrasound images generated; S83. Calculate the ultrasonic imaging detection quality index Y G , the specific formula is: ; S84, comparing the calculated ultrasound imaging detection quality index with the expected value of ultrasound imaging detection quality, if the calculated value is greater than or equal to the preset value, it is determined that the ultrasound imaging detection quality control effect within the ultrasound imaging detection task cycle meets expectations, otherwise it is determined that the ultrasound imaging detection quality control effect within the ultrasound imaging detection task cycle does not meet expectations; S85. Send the judgment result to the high voltage cable terminal management center Technical effects and advantages of the present invention: 1. The present invention performs deconvolution processing on the received ultrasonic echo signal based on wavelet transform, which can effectively separate the overlapping ultrasonic echo signals and eliminate the noise in the signal; the present invention performs bilinear interpolation on the generated ultrasonic image of the lead-tin alloy sheath and then performs binarization processing to segment the image, calculates the defect area after the segmentation is completed, and then sends the defect position information and defect area to the high-voltage cable terminal management center, which can achieve high-precision positioning of the defect.

[0012] 2. The present invention collects ultrasonic echo signal denoising data, ultrasonic image data and defect detection data within the ultrasonic imaging detection task cycle; processes the collected ultrasonic echo signal denoising data to calculate the denoising effect coefficient, processes the collected ultrasonic image data to calculate the ultrasonic imaging control reliability coefficient, and processes the collected defect detection data to calculate the defect detection accuracy coefficient; respectively calculates the average denoising effect coefficient and the average ultrasonic imaging control reliability coefficient, and evaluates the ultrasonic imaging detection quality based on the average denoising effect index, the average ultrasonic imaging control reliability coefficient and the defect detection accuracy coefficient, thereby providing an evaluation method for the quality control effect of ultrasonic imaging detection, which can determine whether the ultrasonic imaging detection scheme needs to be optimized through intuitive data, and can ensure the quality of ultrasonic imaging detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a diagram of the method steps of the present invention.

[0014] Figure 2 It is a system structure block diagram of the present invention. DETAILED DESCRIPTION

[0015] 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.

[0016] like Figure 1 The present embodiment provides an ultrasonic imaging detection method for a lead-tin alloy sheath of a high-voltage cable terminal, comprising the following steps: S1: After selecting the ultrasonic imaging detection equipment, debug and calibrate the selected equipment, and start the preparation before detection after confirming that the selected equipment is working normally; It should be specifically explained in this embodiment that the ultrasonic imaging detection equipment selected in step S1 carries a phased array ultrasonic transducer and is capable of circumferential creeping and axial translation of the high-voltage cable terminal.

[0017] It should be specifically explained in this embodiment that the preparation before detection in step S1 includes the following steps: S11, planning the ultrasound imaging scanning path and confirming the use of axial bow-shaped scanning; S12, setting ultrasonic imaging detection parameters, wherein the ultrasonic imaging detection parameters include transmit pulse width, maximum pulse repetition frequency, transmit pulse focusing delay, receive gain, receive bandwidth, receive focusing delay, ultrasonic transducer scanning radius, center frequency and bandwidth of phased array ultrasonic transducer; S13, planning the scanning motion control process: after the high-voltage cable terminal is zero-calibrated using the Hall switch, the ultrasonic imaging detection equipment is controlled to move to the zero point and the scanning parameters are input. The ultrasonic imaging detection equipment performs ultrasonic imaging detection according to the set scanning path, ultrasonic imaging detection parameters and scanning parameters. After each step of axial motion and circumferential motion is completed, the motion control board will pause the motor movement and notify the ultrasonic board to collect ultrasonic data. After the ultrasonic board completes the ultrasonic data collection at the current position, it notifies the motion control board to continue the movement. The scanning motion and ultrasonic data collection are performed alternately until the scanning is completed. The scanning parameters refer to the speed, step, total stroke and sampling frequency of the axial motion and circumferential motion; S14. Clean the dirt and grease on the surface of the high-voltage cable terminal and apply coupling agent between the surface of the high-voltage cable terminal and the ultrasonic phased array probe after the cleaning work is completed.

[0018] S2: After the preparatory work before the test is completed, the ultrasonic phased array probe is attached to the outer surface of the high-voltage cable terminal, and ultrasonic scanning detection is performed according to the settings to collect the pulse excitation signal emitted by the phased array ultrasonic transducer and the ultrasonic echo signal received by each array element; S3: performing deconvolution processing on the received ultrasonic echo signal to separate the overlapping ultrasonic echo signals and eliminate the noise in the signal; Furthermore, the process of deconvolution processing of the ultrasonic echo signal in step S3 is as follows: S31. Based on signal theory, the ultrasonic echo signal y(t) received by the phased array ultrasonic transducer is expressed as: , x(t) is the ultrasonic signal before entering the high-voltage cable terminal, h(t) is the response of each process experienced by the ultrasonic echo signal when it is reflected back from the high-voltage cable terminal, and n(t) is random noise; S32, calculating the maximum value of the correlation coefficient between the ultrasonic echo signal y(t) and the commonly used wavelet basis function φ(t), and the wavelet basis function corresponding to the obtained result is the target wavelet basis function; S33, after confirming the target wavelet basis function, performing wavelet transform on the ultrasonic echo signal y(t) to obtain sub-band signals located in different frequency bands, calculating the correlation coefficients between an interface echo of the sub-band signals in different frequency bands and the other interface echoes, and then extracting the maximum value, and the interface echo signal of the frequency band sub-band signal corresponding to the maximum value of the rank correlation coefficient is used as a reference signal for Wiener filtering; S34, after Fourier transforming the reference signal, the frequency domain response H(ω) is calculated based on the Wiener filter. The specific formula is: , where X(ω), X * (ω), Y(ω), Q 2 They are the Fourier transform of x(t) with respect to t, the conjugate value after the Fourier transform of x(t) with respect to t, the Fourier transform of y(t) with respect to t, and the passivation factor; S35. Perform inverse Fourier transform on the frequency domain response H(ω) to obtain a deconvolution result h(t).

[0019] Specifically, in this embodiment, x(t) is the result of the excitation signal after the response of the motor conversion, etc. Since the components of the first interface echo signal in the received signal are relatively simple and there is no overlap, the first interface echo signal in the received signal can be intercepted by a window function as the input signal x(t). Therefore, the reference signal of the Wiener filter in step S33 is x(t). Regarding the passivation factor, its recommended value is .

[0020] S4: Reconstruct and focus each set of transmit-receive data based on frequency domain imaging conditions, superimpose the obtained reconstruction results to generate axial full-matrix ultrasonic frequency domain imaging of the lead-tin alloy sheath of the high-voltage cable terminal, and generate circumferential frequency domain synthetic aperture imaging of the lead-tin alloy sheath of the high-voltage cable terminal based on the frequency domain synthetic aperture algorithm; It should be specifically explained in this embodiment that the specific steps of the axial full-matrix ultrasonic frequency domain imaging of the high-voltage cable terminal in step S4 are as follows: S411. It is known that the ultrasonic transducer is at z a = 0 receiving sound field P u (k x ,z a =0,ω), the sound field extrapolation formula of the laminated structure is introduced to reconstruct the frequency domain of the ultrasonic echo signal receiving sound field. The specific sound field extrapolation formula of the laminated structure is: , P u (k x ,z a ,ω) is the frequency domain expression of the reflected echo transmitted by the uth array element in the array transducer and received by all array elements after two-dimensional Fourier transformation, k x is the wave number component in the x direction, ω is the angular frequency, z a is the penetration depth of the transmitted sound wave in the circumferential direction inside the high-voltage cable terminal, α(k x ,z a ,ω) is the phase factor; S412, using the emission signal of the excited array element in the full matrix acquisition process as the boundary condition of the emission sound field and using Q u (x,z a =0,t) indicates that, and in Q u (x,z a =0,t), only the amplitude at the uth array element is 1, and the rest are 0. Then the frequency domain expression of the transmitted sound field is Q u (k x ,z a ,ω)is: , Q u (k x ,z a =0,ω) is Q u (x,z a =0,t), α * (k x ,z a ,ω) is α(k x ,z a ,ω) conjugate value; S413, the receiving sound field and the transmitting sound field are simultaneously extrapolated to any depth of the stacked structure, and focused imaging is performed through a cross-correlation operation. Then the imaging condition is: , I u (x,z a ) is the pixel point (x,z a )’s imaging amplitude; S414, reconstructing the focused imaging of each set of transmit-receive data, and superimposing these reconstruction results to obtain the final full-matrix imaging result, that is, .

[0021] It should be specifically explained in this embodiment that the specific steps of the circumferential frequency domain synthetic aperture imaging of the high-voltage cable terminal in step S4 are as follows: S421. The sound field of the ultrasonic transducer at the circumferential scanning surface of the high-voltage cable terminal is reconstructed based on the sound field reconstruction formula of the laminated cylindrical structure. The sound field reconstruction formula of the laminated cylindrical structure is: , P n (r,k za ,ω) is any point in the cylindrical structure (r,φ,z b ) of the sound pressure P n (r,φ,z b ,t) through about φ,z b ,t is the frequency domain expression after Fourier transformation, r is the straight-line distance from the central axis of the cylinder to any point, φ is the angular position of any point on the plane perpendicular to the axis of the cylinder, z b P is the axial penetration depth of the transmitted sound wave inside the high-voltage cable terminal. n (r1,k za ,ω) is the receiving sound field of the ultrasonic transducer at r=r1, the scanning radius of the ultrasonic transducer is r1, T n (r1,r,k r,l ) is the transfer function, T n (r i ,r i+1 ,k r,i ) is the transfer function; S422. If there is a scatterer on the scanning surface, at t=0, the reflected echo of the scatterer has not yet diverged and is not interfered by the echo of scatterers at other positions. Taking t=0 as the imaging condition, the reconstructed data on the cylindrical surface of the high-voltage cable terminal is , each cylindrical surface in the high-voltage cable terminal structure is reconstructed and imaged to obtain the final high-resolution ultrasonic image.

[0022] What needs to be specifically explained in this embodiment is that based on the above-mentioned imaging method, axial full-matrix ultrasonic frequency domain imaging of the lead-tin alloy sheath of the high-voltage cable terminal and circumferential frequency domain synthetic aperture imaging of the lead-tin alloy sheath of the high-voltage cable terminal can be obtained.

[0023] S5: Perform bilinear interpolation on the generated ultrasonic image of the lead-tin alloy sheath and then perform binarization processing to segment the image. After the segmentation is completed, the defect area is calculated, and then the defect location information and defect area are sent to the high-voltage cable terminal management center; Further, the specific steps of the defect detection in step S5 are as follows: S51. Given the coordinates of the interpolation point p(x,z), retrieve the values ​​of the nearest neighbor points of p(x,z) in the negative x direction, positive x direction, negative z direction, and positive z direction in the imaging numerical matrix, respectively, denoted as q 11 (x1,z1),q 21 (x2,z1),q 12 (x1,z2),q 22 (x2, z2), when calculating the value of the interpolation point, first perform linear interpolation in the x direction to calculate the values ​​of p1(x, z1) and p2(x, z2). The specific formula is: , and then perform linear interpolation in the z direction to calculate the value of the interpolation point p (x, z). The specific formula is: ; S52, after the interpolation process is completed, a grayscale threshold is set, pixels greater than the threshold are retained, and pixels less than the threshold are deleted; S53, randomly selecting an edge point of the lead-tin alloy sheath ultrasonic image after binarization as the starting point, setting its gray value for marking, and then searching the eight neighborhoods of the starting point in order from top to bottom and from left to right according to the gray value of the mark, and after finding the next edge point, recording its coordinate value and using it as the new starting point to continue searching, repeating this process until returning to the initial starting point; S54, after obtaining the edge point coordinate set of the lead-tin alloy sheath defect area, record the number of pixels m of the entire image z and the number of pixels in the defect area m q , get the actual area A of the entire image s Then calculate the defect area A q , the specific formula is: ; S55, sending the calculated lead-tin alloy sheath defect area and defect location information to the high-voltage cable terminal management center.

[0024] S6: Collecting ultrasonic echo signal denoising data, ultrasonic image data and defect detection data within the ultrasonic imaging detection task cycle; Furthermore, the ultrasonic echo signal denoising data collected in the step S6 includes the signal-to-noise ratio and signal variance before each denoising process and the signal-to-noise ratio and signal variance after the denoising process; the ultrasonic image data collected in the step S6 includes the axial resolution, time resolution and contrast resolution of each ultrasonic image generated; the defect detection data collected in the step S6 includes the number of defects correctly detected, the actual number of defects, the area of ​​each defect detected and the actual area of ​​the defects detected.

[0025] S7: Processing the collected ultrasonic echo signal denoising data to calculate the denoising effect coefficient, processing the collected ultrasonic image data to calculate the ultrasonic imaging control reliability coefficient, and processing the collected defect detection data to calculate the defect detection accuracy coefficient; Further, the data processing process in step S7 is as follows: S71, calculate the denoising effect coefficient X of the denoising process of the i-th ultrasonic echo signal zi , the specific formula is: , α qi , α hi , σ 2 qi , σ 2 hi They are respectively the signal-to-noise ratio of the i-th ultrasonic echo signal before denoising, the signal-to-noise ratio after denoising, the variance of the signal before denoising, and the variance of the signal after denoising; S72, calculating the ultrasonic imaging control reliability coefficient X of the generated i-th ultrasonic image ci , the specific formula is: ,β zci , β tci , β dci are the actual axial resolution, actual time resolution, and actual contrast resolution of the i-th ultrasound image, β zs , β ts , β ds They are the theoretical axial resolution, theoretical time resolution, and theoretical contrast resolution of ultrasound images, respectively. The specific calculation formulas are as follows: , D m is the pulse width, v s is the speed of sound, , f c is the sampling frequency, , I1, I2, σ e They are, in order, the average signal intensity of the defective area of ​​the ultrasonic image of the lead-tin alloy sheath, the average signal intensity of the normal area of ​​the ultrasonic image of the lead-tin alloy sheath, and the standard deviation of the noise in the normal area of ​​the ultrasonic image of the lead-tin alloy sheath; S73. Calculate the defect detection accuracy coefficient X within the ultrasonic imaging detection task cycleu , the specific formula is: , m ra 、m rz , A qi , A ci They are the number of defects detected correctly, the actual number of defects, the area of ​​the i-th defect detected, and the actual area of ​​the i-th defect detected.

[0026] S8: Calculate the average denoising effect index and the average ultrasonic imaging control reliability coefficient respectively, and then evaluate the ultrasonic imaging detection quality based on the average denoising effect index, the average ultrasonic imaging control reliability coefficient and the defect detection accuracy coefficient.

[0027] Furthermore, the specific steps of step S8 for evaluating the quality of ultrasonic imaging detection are as follows: S81. Calculate the average denoising effect coefficient X zr , the specific formula is: , n a is the number of times the ultrasonic echo signal is de-noised; S82. Calculate the average ultrasonic imaging control reliability coefficient X cr , the specific formula is: , n b is the number of ultrasound images generated; S83. Calculate the ultrasonic imaging detection quality index Y G , the specific formula is: ; S84, comparing the calculated ultrasound imaging detection quality index with the expected value of ultrasound imaging detection quality, if the calculated value is greater than or equal to the preset value, it is determined that the ultrasound imaging detection quality control effect within the ultrasound imaging detection task cycle meets expectations, otherwise it is determined that the ultrasound imaging detection quality control effect within the ultrasound imaging detection task cycle does not meet expectations; S85. Send the judgment result to the high-voltage cable terminal management center.

[0028] It should be specifically noted in this embodiment that the preset values ​​and expected values ​​used are selected based on actual needs and are not limited to specific values ​​here.

[0029] like Figure 2The embodiment shown provides an ultrasonic imaging detection system for the lead-tin alloy sheath of a high-voltage cable terminal, including a pre-detection preparation module, an ultrasonic scanning detection module, an ultrasonic echo signal processing module, an ultrasonic imaging module, a defect detection module, an ultrasonic imaging detection data acquisition module, an ultrasonic imaging detection data processing module, an ultrasonic imaging detection quality evaluation module and a database. The pre-detection preparation module, the ultrasonic scanning detection module, the ultrasonic echo signal processing module, the ultrasonic imaging module, the defect detection module, the ultrasonic imaging detection data acquisition module, the ultrasonic imaging detection data processing module and the ultrasonic imaging detection quality evaluation module are connected in sequence, the ultrasonic echo signal processing module and the ultrasonic imaging module are connected to the ultrasonic imaging detection data acquisition module, and all modules in the system are connected to the database.

[0030] The pre-test preparation module debugs and calibrates the selected ultrasonic imaging detection equipment after selecting it, and starts the pre-test preparation after confirming that the selected equipment is in normal working state; After the preparatory work before the detection is completed, the ultrasonic scanning detection module fits the ultrasonic phased array probe to the outer surface of the high-voltage cable terminal, performs ultrasonic scanning detection according to the settings, and collects the pulse excitation signal emitted by the phased array ultrasonic transducer and the ultrasonic echo signal received by each array element; The ultrasonic echo signal processing module performs deconvolution processing on the received ultrasonic echo signal to separate the overlapping ultrasonic echo signals and eliminate the noise in the signal; The ultrasonic imaging module reconstructs focused imaging of each set of transmission-reception data based on frequency domain imaging conditions, superimposes the obtained reconstruction results to generate axial full-matrix ultrasonic frequency domain imaging of the lead-tin alloy sheath of the high-voltage cable terminal, and generates circumferential frequency domain synthetic aperture imaging of the lead-tin alloy sheath of the high-voltage cable terminal based on the frequency domain synthetic aperture algorithm; The defect detection module performs bilinear interpolation on the generated ultrasonic image of the lead-tin alloy sheath and then performs binarization processing to segment the image, calculates the defect area after segmentation, and then sends the defect location information and defect area to the high-voltage cable terminal management center; The ultrasonic imaging detection data acquisition module is used to collect ultrasonic echo signal denoising data, ultrasonic image data and defect detection data within the ultrasonic imaging detection task cycle; The ultrasonic imaging detection data processing module processes the collected ultrasonic echo signal denoising data to calculate the denoising effect coefficient, processes the collected ultrasonic image data to calculate the ultrasonic imaging control reliability coefficient, and processes the collected defect detection data to calculate the defect detection accuracy coefficient; The ultrasonic imaging detection quality evaluation module calculates the average denoising effect index and the average ultrasonic imaging control reliability coefficient respectively, and then evaluates the ultrasonic imaging detection quality based on the average denoising effect index, the average ultrasonic imaging control reliability coefficient and the defect detection accuracy coefficient; The database is used to store data information of all modules in the system.

[0031] Finally: The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An ultrasonic imaging detection method for a lead-tin alloy sheath of a high-voltage cable terminal, characterized in that: The following steps are involved: S1: After selecting the ultrasonic imaging detection equipment, debug and calibrate the selected equipment, and start the preparation before detection after confirming that the selected equipment is working normally; S2: After the preparatory work before the test is completed, the ultrasonic phased array probe is attached to the outer surface of the high-voltage cable terminal, and ultrasonic scanning detection is performed according to the settings to collect the pulse excitation signal emitted by the phased array ultrasonic transducer and the ultrasonic echo signal received by each array element; S3: performing deconvolution processing on the received ultrasonic echo signal to separate the overlapping ultrasonic echo signals and eliminate the noise in the signal; S4: Reconstruct and focus each set of transmit-receive data based on frequency domain imaging conditions, superimpose the obtained reconstruction results to generate axial full-matrix ultrasonic frequency domain imaging of the lead-tin alloy sheath of the high-voltage cable terminal, and generate circumferential frequency domain synthetic aperture imaging of the lead-tin alloy sheath of the high-voltage cable terminal based on the frequency domain synthetic aperture algorithm; S5: Perform bilinear interpolation on the generated ultrasonic image of the lead-tin alloy sheath and then perform binarization processing to segment the image. After the segmentation is completed, the defect area is calculated, and then the defect location information and defect area are sent to the high-voltage cable terminal management center; S6: Collecting ultrasonic echo signal denoising data, ultrasonic image data and defect detection data within the ultrasonic imaging detection task cycle; S7: Processing the collected ultrasonic echo signal denoising data to calculate the denoising effect coefficient, processing the collected ultrasonic image data to calculate the ultrasonic imaging control reliability coefficient, and processing the collected defect detection data to calculate the defect detection accuracy coefficient; S8: Calculate the average denoising effect index and the average ultrasonic imaging control reliability coefficient respectively, and then evaluate the ultrasonic imaging detection quality based on the average denoising effect index, the average ultrasonic imaging control reliability coefficient and the defect detection accuracy coefficient.

2. The ultrasonic imaging detection method of the lead-tin alloy sheath of a high-voltage cable terminal according to claim 1 is characterized in that: The process of deconvolution processing of the ultrasonic echo signal in step S3 is as follows: S31. Based on signal theory, the ultrasonic echo signal y(t) received by the phased array ultrasonic transducer is expressed as: , x(t) is the ultrasonic signal before entering the high-voltage cable terminal, h(t) is the response of each process experienced by the ultrasonic echo signal when it is reflected back from the high-voltage cable terminal, and n(t) is random noise; S32, calculating the maximum value of the correlation coefficient between the ultrasonic echo signal y(t) and the commonly used wavelet basis function φ(t), and the wavelet basis function corresponding to the obtained result is the target wavelet basis function; S33, after confirming the target wavelet basis function, performing wavelet transform on the ultrasonic echo signal y(t) to obtain sub-band signals located in different frequency bands, calculating the correlation coefficients between an interface echo of the sub-band signals in different frequency bands and the other interface echoes, and then extracting the maximum value, and the interface echo signal of the frequency band sub-band signal corresponding to the maximum value of the rank correlation coefficient is used as a reference signal for Wiener filtering; S34, after Fourier transforming the reference signal, the frequency domain response H(ω) is calculated based on the Wiener filter. The specific formula is: , where X(ω), X * (ω), Y(ω), Q 2 They are the Fourier transform of x(t) with respect to t, the conjugate value after the Fourier transform of x(t) with respect to t, the Fourier transform of y(t) with respect to t, and the passivation factor; S35. Perform inverse Fourier transform on the frequency domain response H(ω) to obtain a deconvolution result h(t).

3. The ultrasonic imaging detection method of the lead-tin alloy sheath of a high-voltage cable terminal according to claim 1 is characterized in that: The specific steps of the defect detection in step S5 are as follows: S51. Given the coordinates of the interpolation point p(x,z), retrieve the values ​​of the nearest neighbor points of p(x,z) in the negative x direction, positive x direction, negative z direction, and positive z direction in the imaging numerical matrix, respectively, denoted as q 11 (x1,z1),q 21 (x2,z1),q 12 (x1,z2),q 22 (x2, z2), when calculating the value of the interpolation point, first perform linear interpolation in the x direction to calculate the values ​​of p1(x, z1) and p2(x, z2). The specific formula is: , and then perform linear interpolation in the z direction to calculate the value of the interpolation point p (x, z). The specific formula is: ; S52, after the interpolation process is completed, a grayscale threshold is set, pixels greater than the threshold are retained, and pixels less than the threshold are deleted; S53, randomly selecting an edge point of the lead-tin alloy sheath ultrasonic image after binarization as the starting point, setting its gray value for marking, and then searching the eight neighborhoods of the starting point in order from top to bottom and from left to right according to the gray value of the mark, and after finding the next edge point, recording its coordinate value and using it as the new starting point to continue searching, repeating this process until returning to the initial starting point; S54, after obtaining the edge point coordinate set of the lead-tin alloy sheath defect area, record the number of pixels m of the entire image z and the number of pixels in the defect area m q , get the actual area A of the entire image s Then calculate the defect area A q , the specific formula is: ; S55, sending the calculated lead-tin alloy sheath defect area and defect location information to the high-voltage cable terminal management center.

4. The ultrasonic imaging detection method of the lead-tin alloy sheath of a high-voltage cable terminal according to claim 1 is characterized in that: The ultrasonic echo signal denoising data collected in the step S6 includes the signal-to-noise ratio and signal variance before each denoising process and the signal-to-noise ratio and signal variance after the denoising process; the ultrasonic image data collected in the step S6 includes the axial resolution, time resolution and contrast resolution of each ultrasonic image generated; the defect detection data collected in the step S6 includes the number of defects correctly detected, the actual number of defects, the area of ​​each defect detected and the actual area of ​​the defects detected.

5. The ultrasonic imaging detection method of the lead-tin alloy sheath of a high-voltage cable terminal according to claim 1 is characterized in that: The data processing process in step S7 is as follows: S71, calculate the denoising effect coefficient X of the denoising process of the i-th ultrasonic echo signal zi , the specific formula is: , α qi , α hi , σ 2 qi , σ 2 hi They are respectively the signal-to-noise ratio of the i-th ultrasonic echo signal before denoising, the signal-to-noise ratio after denoising, the variance of the signal before denoising, and the variance of the signal after denoising; S72, calculating the ultrasonic imaging control reliability coefficient X of the generated i-th ultrasonic image ci , the specific formula is: ,β zci , β tci , β dci are the actual axial resolution, actual time resolution, and actual contrast resolution of the i-th ultrasound image, respectively. zs , β ts , β ds They are the theoretical axial resolution, theoretical time resolution, and theoretical contrast resolution of ultrasound images, respectively. The specific calculation formulas are as follows: , D m is the pulse width, v s is the speed of sound, , f c is the sampling frequency, , I1, I2, σ e They are, in order, the average signal intensity of the defective area of ​​the ultrasonic image of the lead-tin alloy sheath, the average signal intensity of the normal area of ​​the ultrasonic image of the lead-tin alloy sheath, and the standard deviation of the noise in the normal area of ​​the ultrasonic image of the lead-tin alloy sheath; S73. Calculate the defect detection accuracy coefficient X within the ultrasonic imaging detection task cycle u , the specific formula is: , m ra 、m rz , A qi , A ci They are the number of defects detected correctly, the actual number of defects, the area of ​​the i-th defect detected, and the actual area of ​​the i-th defect detected.

6. The ultrasonic imaging detection method of the lead-tin alloy sheath of a high-voltage cable terminal according to claim 1 is characterized in that: The specific steps of step S8 for evaluating the quality of ultrasonic imaging detection are as follows: S81. Calculate the average denoising effect coefficient X zr , the specific formula is: , n a is the number of times the ultrasonic echo signal is de-noised; S82. Calculate the average ultrasonic imaging control reliability coefficient X cr , the specific formula is: , n b is the number of ultrasound images generated; S83. Calculate the ultrasonic imaging detection quality index Y G , the specific formula is: ; S84, comparing the calculated ultrasound imaging detection quality index with the expected value of ultrasound imaging detection quality, if the calculated value is greater than or equal to the preset value, it is determined that the ultrasound imaging detection quality control effect within the ultrasound imaging detection task cycle meets expectations, otherwise it is determined that the ultrasound imaging detection quality control effect within the ultrasound imaging detection task cycle does not meet expectations; S85. Send the judgment result to the high-voltage cable terminal management center.

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