Thread vanishing point positioning method, system, device and storage medium

Abstract

The present application belongs to the technical field of pipe detection, and provides a thread vanishing point positioning method, system, device and storage medium, wherein the method comprises: acquiring a thread image, extracting an initial contour curve and performing digital processing, acquiring thread parameters based on the processed curve, and then calculating the vanishing point position. The method of the present application discards or reduces manual measurement, completes thread data acquisition and analysis through automation technology, processes data digitally and performs real-time operation, obtains the thread error of the pipe and the standard part, greatly reduces the uncertainty of manual operation, significantly improves the detection stability and accuracy; at the same time, it fully considers the influence of the taper error on the position of the vanishing point, and makes adaptive compensation correction according to different working conditions, effectively solves the problem of systematic deviation between the detection results and the actual situation of the traditional positioning method, and meets the high-precision requirement of oil casing thread detection.

Description

Technical Field

[0001] The present invention belongs to the technical field of pipe fitting detection, and particularly relates to a method, system, device and storage medium for locating the thread vanishing point. Background Art

[0002] In oil and gas exploration operations, the connection reliability of pipe threads has a direct impact on the safety and efficiency of operations in various links such as drilling, well completion and production. Among them, the thread vanishing point is one of the important parameters for evaluating the quality of thread processing. The so-called thread vanishing point refers to the position where the thread tail terminates on the pipe surface, that is, the end point where the thread profile gradually disappears. Its positioning accuracy directly affects the sealing performance, tensile strength and fatigue resistance of the thread. Once the position of the thread vanishing point does not meet the standard requirements, it will cause problems such as improper thread fitting, and then lead to leakage, and in severe cases, even safety accidents such as pipe string fracture may occur.

[0003] Currently, for the detection of the thread vanishing point of oil casing threads, it mainly relies on the following two types of methods:

[0004] The first type is to use mechanical measuring tools to obtain the distance parameter corresponding to the vanishing point through manual measurement. When the measurement result meets the requirements of API Spec 5B (Specification for Threading, Gauging and Thread Inspection of Casing, Tubing, and Line Pipe Threads), it is determined that the thread vanishing point parameter is qualified. However, this detection method has obvious deficiencies. Not only is the detection efficiency low, but the measurement result is also easily affected by the subjective factors of the operator, and it is difficult to ensure the detection stability and accuracy.

[0005] The second type is to use optical non-contact measurement means,借助机器视觉等相关技术,通过对采集到的图像进行处理,提取螺纹的轮廓特征,进而计算得出螺纹消失点的位置。相较于机械式人工测量方法,该光学非接触式测量方法具备非接触、高效率的显著优势,在实际检测中应用更为广泛。但是,在实际加工过程中,由于设备长时间使用出现磨损,或者加工工艺存在偏差等因素,会导致管材螺纹的锥度产生误差。而螺纹锥度误差会直接改变螺纹轴向尺寸与径向尺寸之间的对应关系,影响测量的准确性。

[0006] It seems there is some garbled text in ID=17. Please check and correct it so that I can provide a more accurate translation for that part. The translated text for the rest is as above.For example, patent CN113610926A discloses a camera calibration method based on the orthogonality of vanishing points. This method takes multiple calibration images of a plane plate containing two sets of orthogonal parallel straight lines as input, and sequentially calculates the two sets of orthogonal vanishing points in each image, solves for the principal points based on multiple sets of vanishing points, removes images with poor positions based on a distance threshold, and calculates the focal length. Finally, it obtains the camera's extrinsic parameters and distortion coefficients based on the focal length. It does not require a specific calibration template, feature point matching, or 3D spatial point coordinates. However, this application does not solve the problem of taper error in threaded pipes.

[0007] Therefore, existing technologies have not yet established a dynamic correction model that can correlate taper error with vanishing point position, and cannot effectively compensate for the impact of taper error. This results in a systematic deviation between the final detection results and the actual situation, making it difficult to meet the high-precision detection requirements of oil casing. Summary of the Invention

[0008] To address the problems in the background art, this invention proposes a method, system, device, and storage medium for locating the disappearance point of a thread.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] The method for locating the vanishing point of a thread includes the following steps:

[0011] Obtain an image of the thread of the pipe fitting under test;

[0012] The initial thread profile curve is extracted from the image of the thread, and the initial thread profile curve is digitized to obtain the digitized thread profile curve.

[0013] The thread parameters of the pipe fitting under test are obtained based on the thread profile curve after digital processing.

[0014] The location of the thread vanishing point is calculated based on the thread parameters of the pipe fitting under test.

[0015] Further, acquiring an image of the thread on the surface of the pipe fitting to be tested includes the following steps:

[0016] The shooting path is set based on the pipe to be tested, and the light source is set along the shooting path;

[0017] The thread of the pipe under test is photographed at set angles along the shooting path to obtain the thread image of the pipe under test.

[0018] Furthermore, the thread parameters include maximum critical diameter, minimum critical diameter, ellipticity, taper, and thread height.

[0019] Furthermore, the thread parameters of the pipe fitting under test are obtained based on the digitally processed thread profile curve, including the following steps:

[0020] The maximum and minimum top diameters of the pipe fitting under test are obtained based on the thread profile curve after digital processing.

[0021] Calculate the difference between the maximum and minimum top diameters to obtain the actual ellipticity of the pipe fitting under test;

[0022] Calculate the change in the pitch diameter of the thread along the axial direction, and combine this with the fixed thread spacing to calculate the taper of the pipe fitting under test.

[0023] Extract the coordinate data of the thread crest and thread root, perform linear fitting on both using the least squares method, and calculate the difference between the intercepts of the two fitted lines to obtain the thread height.

[0024] Furthermore, the location of the thread vanishing point is calculated based on the thread parameters of the pipe fitting under test, including the following steps:

[0025] When the actual ellipticity of the pipe fitting under test is less than or equal to the set value, the position compensation amount of the thread vanishing point is calculated, and the position of the thread vanishing point is calculated based on the compensation amount.

[0026] When the actual ellipticity of the pipe fitting under test is greater than the set value, the thread of the fitting under test is a black-top thread, and the position of the thread vanishing point is calculated based on the starting position of the black-top thread.

[0027] Furthermore, when the actual ellipticity of the pipe fitting under test is less than or equal to a set value, the position of the thread vanishing point satisfies:

[0028] ;

[0029] ;

[0030] ;

[0031] In the formula, L actual This indicates the actual distance from the pipe end of the pipe fitting under test to the point where the thread disappears. L V It is the distance from the pipe end to the point where the thread disappears under ideal conditions; L thread It is the distance from the pipe end to the last complete thread. H The tooth profile height of the first incomplete thread; β This refers to the retraction angle; α The thread taper angle; Indicates the positional compensation amount at the point where the thread disappears; T actual Indicates the actual ellipticity; T std Indicates the theoretical ellipticity.

[0032] Furthermore, when the actual ellipticity of the pipe fitting under test is greater than the set value, the position of the thread vanishing point satisfies:

[0033] ;

[0034] In the formula, L actual This indicates the actual distance from the pipe end of the pipe fitting under test to the point where the thread disappears. T actual Indicates the actual ellipticity; T std Indicates theoretical ellipticity; L black This indicates the length from the end of the pipe fitting under test to the starting position of the black top thread.

[0035] Furthermore, after calculating the location of the thread vanishing point based on the thread parameters of the pipe fitting under test, the following steps are also included:

[0036] The position of the thread vanishing point of the pipe fitting under test is compared with the position of the thread vanishing point of the standard pipe fitting. If the difference between the two is within the preset range, the pipe fitting under test is qualified; otherwise, it is unqualified.

[0037] A thread vanishing point positioning system, comprising:

[0038] Image acquisition unit, used to acquire images of the threads of the pipe fitting under test;

[0039] The contour extraction unit is used to extract the initial thread contour curve from the image of the thread and to digitize the initial thread contour curve to obtain the digitized thread contour curve.

[0040] The parameter calculation unit is used to obtain the thread parameters of the pipe fitting under test based on the digitally processed thread profile curve; the thread parameters include the maximum critical diameter, minimum critical diameter, ellipticity, taper, and tooth height.

[0041] The positioning unit is used to calculate the position of the thread vanishing point based on the thread parameters of the pipe fitting under test.

[0042] Furthermore, it also includes an analysis unit, which is used to compare the position of the thread vanishing point of the pipe fitting under test with the position of the thread vanishing point of the standard pipe fitting. If the difference between the two is within a preset range, the pipe fitting under test is determined to be qualified; otherwise, the pipe fitting under test is determined to be unqualified.

[0043] An electronic device, comprising:

[0044] Memory, used to store computer programs;

[0045] The processor, when executing a computer program stored in memory, implements the above-mentioned thread vanishing point positioning method.

[0046] A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the above-described thread vanishing point positioning method.

[0047] The beneficial effects of this invention are:

[0048] 1. For the thread inspection of the pipe fittings to be tested, the thread vanishing point positioning method of the present invention eliminates or reduces the manual measurement mode in each process, completes the acquisition and analysis of thread data through automation technology, processes the data in a digital way, and calculates the thread error of the pipe fitting to be tested relative to the standard pipe fitting in real time, which greatly reduces the uncertainty of manual operation and significantly enhances the stability and accuracy of the test results.

[0049] 2. The thread vanishing point positioning method of the present invention fully considers the influence of taper error on the position of the thread vanishing point, and adaptively compensates and corrects the position of the thread vanishing point for different working conditions (or "actual scenarios" or "application situations"), effectively solving the technical problem of systematic deviation between the detection results and the actual situation in traditional positioning methods, and ultimately meeting the high-precision requirements of oil casing for thread detection.

[0050] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description and the drawings. Attached Figure Description

[0051] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0052] Figure 1 A flowchart of the thread vanishing point positioning method of the present invention is shown;

[0053] Figure 2 A device diagram of the image acquisition unit of the present invention is shown;

[0054] Figure 3 A block diagram of the thread vanishing point positioning system of the present invention is shown.

[0055] In the diagram: 1. Industrial CCD camera; 2. Roller bracket; 3. Camera bracket; 4. Interactive processing system; 5. Central control console. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0057] like Figure 1 As shown, a method for locating the vanishing point of a thread is disclosed, including the following steps:

[0058] S1: Obtain an image of the thread of the pipe fitting to be tested.

[0059] S2: Extract the initial thread profile curve from the thread image and digitize the initial thread profile curve to obtain the digitized thread profile curve.

[0060] S3: Based on the digitally processed thread profile curve, the thread parameters of the pipe fitting to be tested are obtained. These parameters mainly include the maximum critical diameter, minimum critical diameter, ellipticity, taper, and tooth height.

[0061] S4: Calculate the location of the thread vanishing point based on the thread parameters of the pipe fitting under test.

[0062] S5: Compare the position of the thread vanishing point of the pipe fitting to be tested with the position of the thread vanishing point of the standard pipe fitting. If the difference between the two is within the preset range, the pipe fitting to be tested is qualified; otherwise, it is unqualified.

[0063] It should be noted that the pipe fittings to be tested in S1-S5 can be oil casing, and the location of the thread vanishing point of this pipeline is being detected. For oil casing, the location of the thread vanishing point is at the end of the incomplete thread section. The distance from the pipe end is the sum of the length of the complete thread section and the length of the incomplete thread section. The complete thread section is the thread portion with both the crest and root intact. The thread profile height of the incomplete thread section gradually decreases until it reaches zero. The specific length is determined by the manufacturing process. The location where the thread profile height is zero is the thread vanishing point.

[0064] It should be further explained that the location of the thread vanishing point is mainly affected by the taper and ellipticity of the oil casing. When the ellipticity is too large, the cutting depth of the thread crest will be uneven due to the change in the pipe diameter during the rotational machining process, resulting in some thread crests not being completely cut, forming a black-top thread. According to industry standards and experimental data, the ellipticity of the trapezoidal thread is usually required to not exceed 0.4% of the outer diameter of the pipe body. When the ellipticity exceeds this threshold, a black-top thread may appear. In this case, the thread vanishing point is located at the position of the black-top thread closest to the pipe end face. The specific calculation process will be explained in detail below with reference to the attached diagram.

[0065] For example, S1 includes the following steps:

[0066] S101: Set the shooting path based on the pipe to be tested, and set the light source along the shooting path.

[0067] S102: Take pictures of the thread of the pipe to be tested at intervals of set angles (e.g., 60°) along the shooting path to obtain the thread image of the pipe to be tested.

[0068] To achieve the steps in S1, Figure 2 Optional equipment is provided, employing an industrial CCD camera 1. CCD stands for Charge Coupled Device, and the camera boasts a 5-megapixel resolution, enabling precise acquisition of thread images of the tested pipe fittings (such as oil casing). It is equipped with a ring-shaped LED (Light-Emitting Diode) light source and a coaxial light source, creating a uniform and shadow-free lighting environment, effectively eliminating glare interference from the thread surface. The light source brightness is adjustable within the range of 0~10000 lux. Furthermore, an optical adjustment mechanism consisting of a rotatable pipe roller support 2 and a movable camera support 3 enables multi-angle, high-resolution imaging, thus meticulously capturing the details of the thread contour. An interactive processing system 4 is also included, used for digital processing, compensation, and output of the acquired images. A central control panel 5 allows for one-button start or stop of each device and setting of various system parameters.

[0069] For example, to perform S2, the following method can be used: the acquired image is digitized using digital image digitization technology, the initial thread profile curve is extracted from it, and background interference and surface defects are removed simultaneously; then, sub-pixel level edge detection is used to further accurately locate and generate an initial profile point set; finally, the least squares method is used to fit these point sets to obtain a smooth and continuous thread profile curve (the digitized thread profile curve).

[0070] For example, when digitizing an image of an oil casing thread, the thread region is first separated from the original image containing oil stains and scratches using threshold segmentation and region growing techniques, removing interference from the background of the pipe outer wall and surface pits. Then, the Zernike subpixel edge detection algorithm is used to obtain a set of thread edge points with an accuracy of 0.1 pixels. These point sets are then substituted into the least squares fitting model to finally obtain a smooth thread profile curve with an error of less than 0.02 mm, laying the foundation for subsequent parameter measurements.

[0071] For example, S3 includes the following steps:

[0072] S301: Obtain the maximum and minimum critical diameters of the pipe fitting under test based on the digitally processed thread profile curve. S302: Calculate the difference between the maximum and minimum critical diameters to obtain the actual ellipticity of the pipe fitting under test. S303: Calculate the axial variation of the thread pitch diameter and, combined with the fixed thread spacing, calculate the taper of the pipe fitting under test. S304: Extract the coordinate data of the thread crest and root, perform linear fitting using the least squares method on both, and calculate the difference in intercepts between the two fitted lines to obtain the thread height.

[0073] For example, S3 can adopt Figure 2 An industrial CCD camera 1 is used to capture images. The pipe is rotated by a roller bracket 2, and an image of the thread is acquired every 60°. Simultaneously, the industrial CCD camera 1 digitizes the images to obtain the thread profile. At this point, the thread tip diameter can be calculated from the three thread profiles acquired at the same location on the complete thread segment. The acquisition positions are as follows: Figure 3 As shown. Based on the calculated top diameter data and the rate of change of top diameter, the positions of the major and minor axes of the pipe are determined, and then the data of the maximum and minimum top diameters are determined. The actual ellipticity is obtained by calculating the difference between the two.

[0074] In addition, the taper is defined as the change in the thread pitch diameter per unit length. Therefore, it is calculated by calculating the change in the thread pitch diameter along the axial direction, combined with the fixed spacing length.

[0075] For example, S4 includes the following steps:

[0076] S401: When the actual ellipticity of the pipe fitting under test is less than or equal to the set value (e.g., 0.4% of the outer diameter of the pipe fitting under test), calculate the position compensation amount of the thread vanishing point, and calculate the position of the thread vanishing point based on the compensation amount.

[0077] S402: When the actual ellipticity of the pipe fitting under test is greater than the set value, the thread of the fitting under test is a black-top thread, and the position of the thread vanishing point is calculated based on the starting position of the black-top thread.

[0078] In the case of S401, under ideal conditions (ellipticity meets the standard, taper conforms to API Spec 5B), the distance from the pipe end to the thread vanishing point is located at the end of the thread tail, i.e., the full thread length plus the incomplete thread length. The full thread length can be obtained by fitting the crest line of the full thread segment using the least squares method. In thread machining, the lathe begins to retract from the incomplete thread, and the thread height gradually decreases until it disappears. Therefore, the ideal distance from the pipe end to the vanishing point is shown in Equation 1:

[0079] (1)

[0080] In the formula, L V It is the distance from the pipe end to the point where the thread disappears under ideal conditions; L thread It is the distance from the pipe end to the last complete thread. H The tooth profile height of the first incomplete thread; β This refers to the retraction angle; α The taper angle of the thread.

[0081] Due to the actual taper and standard taper The difference between them will cause the axial position of the vanishing point to change, so it is necessary to compensate for the error caused by the taper change, as shown in Equation 2:

[0082] (2)

[0083] In the formula, L actual This indicates the actual distance from the pipe end of the pipe fitting under test to the point where the thread disappears. Indicates the positional compensation amount at the point where the thread disappears; T actual Indicates the actual ellipticity; T std Indicates the theoretical ellipticity.

[0084] Combining Equations 1 and 2, when the actual taper is greater than the standard taper, the vanishing point will shift away from the pipe end of the tested fitting, thus obtaining the actual distance from the pipe end to the thread vanishing point. L actual See Equation 3:

[0085] (3)

[0086] When there is a black-top thread in S402, the thread vanishing point is located when the ellipticity is large. Due to insufficient cutting depth at the tooth tip, a black-top thread is generated. At the same time, the black-top area will expand from both sides of the short axis, which shortens the effective thread length visible on the entire circumference. At this time, the thread vanishing point is located at the position of the black-top thread closest to the end face of the pipe fitting under test.

[0087] In the above process, the parameter calculation unit has located the major and minor axes of the pipe fitting under test. At this time, the image acquisition unit of the central control console 5 rotates the pipe fitting under test to a position with the minor axis facing upwards and acquires the thread image at this location. Due to the black-top thread, there will be a large deviation in the tooth profile height in the complete thread segment. The API Spec 5B standard specifies that the tooth profile height deviation is ±0.025mm. At this time, the parameter calculation unit fits the profile tooth crest straight line using the least squares method and iteratively calculates the tooth profile height deviation between adjacent teeth. The position where the deviation of the complete thread segment is greater than 0.025mm and closest to the pipe end is the starting point of the black-top thread. Therefore, when the actual ellipticity of the pipe fitting under test is greater than the set value, the position of the thread vanishing point is as shown in Equation 4:

[0088] (4)

[0089] In the formula, L actual This indicates the actual distance from the pipe end of the pipe fitting under test to the point where the thread disappears. T actual Indicates the actual ellipticity; T std Indicates theoretical ellipticity; L black This indicates the length from the end of the pipe fitting under test to the starting position of the black top thread.

[0090] For example, in S5:

[0091] After the compensation process is completed, the final calculation result of "the position of the thread vanishing point" obtained in S4 can be output to the system interactive interface. The standard value of "the position of the thread vanishing point" of the corresponding specification of casing thread in APISpec5B standard can be automatically retrieved for real-time comparison. Based on the preset range, it is determined whether the corresponding specification of oil casing thread is qualified, and the automatic judgment and result display are completed.

[0092] Meanwhile, in S5, key parameters such as ellipticity threshold and taper alarm value can be flexibly adjusted according to the actual processing capacity and process requirements of the pipe manufacturing plant. In response to dynamic changes in on-site working conditions (such as differences in sleeve material, changes in processing equipment status, etc.), the above-mentioned set parameters can be updated in real time to ensure that the thread vanishing point positioning and qualification judgment results always adapt to actual production needs.

[0093] like Figure 3As shown, it is a thread vanishing point positioning system, including an image acquisition unit (specifically configured Figure 2 equipment), a contour extraction unit, a parameter calculation unit, a positioning unit, and an analysis unit. Among them, the image acquisition unit is used to obtain the image of the thread of the pipe fitting to be measured; the contour extraction unit is used to extract the initial thread contour curve from the image of the thread, and perform digital processing on the initial thread contour curve to obtain the digitally processed thread contour curve; the parameter calculation unit is used to obtain the thread parameters of the pipe fitting to be measured based on the digitally processed thread contour curve; the thread parameters include the maximum major diameter, the minimum major diameter, the ovality, the taper, and the thread profile height; the positioning unit is used to calculate the position of the thread vanishing point based on the thread parameters of the pipe fitting to be measured. The analysis unit is used to compare the position of the thread vanishing point of the pipe fitting to be measured with the position of the thread vanishing point of the standard pipe fitting. If the difference between the two is within the preset range, it is determined that the pipe fitting to be measured is qualified; otherwise, it is determined that the pipe fitting to be measured is unqualified.

[0094] It should be noted that the system embodiment and the method embodiment of the present invention are basically corresponding in the core technical logic. Therefore, the relevant technical details and implementation descriptions of the two can be referred to the corresponding parts in the method embodiment, and will not be repeated here. Regarding the division of each unit and module in the thread vanishing point positioning system, it is only defined based on the functional logic, and is not limited to the above division method. As long as the corresponding functions defined by the present invention can be realized, any division form that conforms to the technical essence should fall within the protection scope of the present invention; in addition, the specific naming of each unit is only for the convenience of mutual distinction and does not constitute a limitation on the protection scope of the present invention.

[0095] To intuitively and detailedly present the actual application process and implementation details of the thread vanishing point positioning method and system proposed by the present invention, the following will combine the attached drawings Figures 1 to 3 , taking the buttress thread of casing pipes with a nominal diameter of 139.7 mm and a nominal diameter of 244.48 mm as typical application objects, comprehensively illustrate the specific operation process of thread vanishing point positioning as follows:

[0096] 1) For the buttress thread of casing pipes with a nominal diameter of 139.7 mm

[0097] Select the nominal major diameter of the buttress thread of casing pipes to be 139.70 mm, the maximum major diameter calculated by the image acquisition unit and the parameter calculation unit to be 139.77 mm, the minimum major diameter to be 139.65 mm, and the ovality to be 0.12 mm; the standard taper is 62.5 mm / m (the taper angle is 3.58°), and the measured taper is 63.7 mm / m (the taper angle is 3.65°); the axial distance from the pipe end to the last complete thread of the thread is 46.76 mm; the thread profile height of the first incomplete thread is 1.56 mm; the relief angle is set to 5.40°, and the calculation steps are as follows:

[0098] Ideal vanishing point distance:

[0099] =46.76+1.56 / sin(5.40-3.65°)=97.84mm;

[0100] Add taper compensation:

[0101] =97.84×0.0192=1.88mm;

[0102] Actual vanishing point distance:

[0103] =97.84 + 1.88 = 99.72 mm;

[0104] According to API Spec 5B, the total length from the end of the 139.7mm trapezoidal sleeve to the vanishing point is 97.16mm. The vanishing point length meets the standard, and the vanishing point length of the trapezoidal sleeve is deemed acceptable.

[0105] 2) Taking a trapezoidal sleeve thread with a nominal diameter of 244.48 mm as an example

[0106] The nominal top diameter is 244.48 mm. The maximum top diameter calculated by the image acquisition module and parameter calculation module of this patent is 244.55 mm, the minimum top diameter is 244.38 mm, and the ellipticity is 0.17 mm. The standard taper is 62.5 mm / m (taper angle is 3.58°), and the measured taper is 64.1 mm / m (taper angle is 3.67°). The axial distance from the pipe end to the last complete thread is 64.24 mm. The tooth profile height of the first incomplete thread is 1.57 mm. The retraction angle is set to 5.40°. The calculation steps are as follows:

[0107] Ideal vanishing point distance:

[0108] =64.24+1.57 / sin(5.40-3.67°)=116.24mm;

[0109] Add taper compensation:

[0110] =116.24×0.0256=2.98mm;

[0111] Actual vanishing point distance:

[0112] =116.24 + 2.98 = 119.22 mm;

[0113] According to API Spec 5B, the total length from the end of the 244.48mm trapezoidal sleeve to the vanishing point is 114.62mm. The vanishing point length meets the standard, and the vanishing point length of the trapezoidal sleeve is deemed acceptable.

[0114] An electronic device, comprising:

[0115] Memory, used to store computer programs;

[0116] The processor, when executing a computer program stored in memory, implements the above-mentioned thread vanishing point positioning method.

[0117] It should be noted that the memory may include random access memory (RAM) or non-volatile memory, such as at least one disk storage device.

[0118] The processors mentioned above can be general-purpose processors, including central processing units (CPUs), network processors (NPs), etc.; they can also be digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.

[0119] A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the above-described thread vanishing point positioning method.

[0120] It should be noted that the computer-readable storage medium may be included in the device / apparatus described in the above embodiments; or it may exist independently and not assembled into the device / apparatus. The computer-readable storage medium carries one or more programs, which, when executed, implement a thread vanishing point positioning method according to an embodiment of the present invention.

[0121] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for locating the vanishing point of a thread, characterized in that, Includes the following steps: Obtain an image of the thread of the pipe fitting under test; The initial thread profile curve is extracted from the image of the thread, and the initial thread profile curve is digitized to obtain the digitized thread profile curve. The thread parameters of the pipe fitting under test are obtained based on the digitally processed thread profile curve. The thread parameters include the maximum critical diameter, minimum critical diameter, ellipticity, taper, and tooth height. The location of the thread vanishing point is calculated based on the thread parameters of the pipe fitting under test, including: When the actual ellipticity of the pipe fitting under test is less than or equal to the set value, the position compensation amount of the thread vanishing point is calculated, and the position of the thread vanishing point is calculated based on the compensation amount. When the actual ellipticity of the pipe fitting under test is greater than the set value, the thread of the fitting under test is a black-top thread, and the position of the thread vanishing point is calculated based on the starting position of the black-top thread.

2. The thread vanishing point positioning method according to claim 1, characterized in that, To obtain a thread image of the surface of the pipe fitting under test, the following steps are included: The shooting path is set based on the pipe to be tested, and the light source is set along the shooting path; The thread of the pipe under test is photographed at set angles along the shooting path to obtain the thread image of the pipe under test.

3. The thread vanishing point positioning method according to claim 1, characterized in that, The thread parameters of the pipe fitting under test are obtained based on the digitally processed thread profile curve, including the following steps: The maximum and minimum top diameters of the pipe fitting under test are obtained based on the thread profile curve after digital processing. Calculate the difference between the maximum and minimum top diameters to obtain the actual ellipticity of the pipe fitting under test; Calculate the change in the pitch diameter of the thread along the axial direction, and combine this with the fixed thread spacing to calculate the taper of the pipe fitting under test. Extract the coordinate data of the thread crest and thread root, perform linear fitting on both using the least squares method, and calculate the difference between the intercepts of the two fitted lines to obtain the thread height.

4. The thread vanishing point positioning method according to claim 1, characterized in that, When the actual ellipticity of the pipe fitting under test is less than or equal to the set value, the position of the thread vanishing point satisfies the following: ； ； ； In the formula, L actual This indicates the actual distance from the pipe end of the pipe fitting under test to the point where the thread disappears. L V It is the distance from the pipe end to the point where the thread disappears under ideal conditions; L thread It is the distance from the pipe end to the last complete thread. H The tooth profile height of the first incomplete thread; β This refers to the retraction angle; α The thread taper angle; Indicates the positional compensation amount at the point where the thread disappears; T actual Indicates the actual ellipticity; T std Indicates the theoretical ellipticity.

5. The thread vanishing point positioning method according to claim 1, characterized in that, When the actual ellipticity of the pipe fitting under test is greater than the set value, the position of the thread vanishing point satisfies the following: ； In the formula, L actual This indicates the actual distance from the pipe end of the pipe fitting under test to the point where the thread disappears. T actual Indicates the actual ellipticity; T std Indicates theoretical ellipticity; L black This indicates the length from the end of the pipe fitting under test to the starting position of the black top thread.

6. The thread vanishing point positioning method according to any one of claims 1-5, characterized in that, After calculating the location of the thread vanishing point based on the thread parameters of the pipe fitting under test, the following steps are also included: The position of the thread vanishing point of the pipe fitting under test is compared with the position of the thread vanishing point of the standard pipe fitting. If the difference between the two is within the preset range, the pipe fitting under test is qualified; otherwise, it is unqualified.

7. A thread vanishing point positioning system, characterized in that, include: Image acquisition unit, used to acquire images of the threads of the pipe fitting under test; The contour extraction unit is used to extract the initial thread contour curve from the image of the thread and to digitize the initial thread contour curve to obtain the digitized thread contour curve. The parameter calculation unit is used to obtain the thread parameters of the pipe fitting under test based on the digitally processed thread profile curve; the thread parameters include the maximum critical diameter, minimum critical diameter, ellipticity, taper, and tooth height. The positioning unit, used to calculate the position of the thread vanishing point based on the thread parameters of the pipe fitting under test, includes: When the actual ellipticity of the pipe fitting under test is less than or equal to the set value, the position compensation amount of the thread vanishing point is calculated, and the position of the thread vanishing point is calculated based on the compensation amount. When the actual ellipticity of the pipe fitting under test is greater than the set value, the thread of the fitting under test is a black-top thread, and the position of the thread vanishing point is calculated based on the starting position of the black-top thread.

8. The thread vanishing point positioning system according to claim 7, characterized in that, It also includes an analysis unit, which is used to compare the position of the thread vanishing point of the pipe fitting under test with the position of the thread vanishing point of the standard pipe fitting. If the difference between the two is within a preset range, the pipe fitting under test is determined to be qualified; otherwise, the pipe fitting under test is determined to be unqualified.

9. An electronic device, characterized in that, include: Memory, used to store computer programs; A processor, when executing a computer program stored in a memory, implements the thread vanishing point positioning method according to any one of claims 1-6.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the thread vanishing point positioning method according to any one of claims 1-6.

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