Method for detecting height and width of circumferential weld of linear section of pipeline

Abstract

The invention relates to a pipeline linear segment circumferential weld height and width detection method. The method comprises the following steps of obtaining point clouds of a pipeline weld and linear segments in front of and behind the weld; fitting the small cylinders section by section by taking the welding seam design width as the step length; iteratively fusing adjacent cylindrical sections with similar radiuses, and segmenting a straight line section and a welding seam coarse positioning section; calculating the distance from the point cloud of the welding seam coarse positioning section to the cylindrical axis of the linear section to obtain accurate welding seam positioning; calculating the difference value between the maximum value of the distance from the welding seam point cloud to the pipeline axis and the pipeline radius to obtain the welding seam height; and projecting the welding seam point cloud to the pipeline axis to obtain a new projection point cloud, and calculating the maximum value of the distance between the points of the projection point cloud to obtain the welding seam width. According to the invention, the detection of the height and width of the circumferential weld of the linear pipeline can be realized, and a new way for the automatic detection of the height and width of the circumferential weld of the linear pipeline is provided.

Description

Technical Field

[0001] The invention relates to automatic detection, in particular to a method for detecting the height and width of a circumferential weld of a straight-line segment of a pipeline, which is used to realize automatic detection of the height and width of a circumferential weld of a straight-line segment pipeline. Background Art

[0002] As the main transmission medium for gases and liquids, pipelines are widely used in the aerospace field due to their advantages such as light weight and high toughness. They are an important part of aircraft engine transmission systems.

[0003] The connection and assembly between different pipelines are achieved through welding. In order to obtain high-quality welded pipelines and improve the level of welding automation, the detection of weld quality is a key link. The welding quality mainly depends on several aspects such as weld formation, weld organization performance, and weld mechanical properties. Among them, the appearance of the weld, that is, the width and height, are important indicators for measuring welding quality and are closely related to the quality of the weld. If the weld is too wide, it means that the current heat condition at the weld is relatively serious. The increase in grain structure caused by the heat deformation of the weld will cause the mechanical properties of the weld to decrease, and then cause the weld to deform; if the weld is too narrow, it means that the current weld and the parent material area of ​​the weld are not well fused, which will cause stress concentration at the unfused part of the weld, resulting in cracks, undercuts and other surface weld defects, which directly affect the bearing strength of the weld. If the weld excess is too large, it will increase the amount of weld grinding, thereby reducing welding production efficiency; if the excess is too small, it will reduce the mechanical properties of the weld.

[0004] Since the three-dimensional shape of actual pipelines is relatively complex, at this stage, general-sized enterprises still use traditional measuring tools combined with manual visual inspection to inspect the appearance quality of pipeline welds. Some institutions have conducted some relevant research on the automated identification and detection of pipeline welds. For example: 1) A digital positioning device and positioning method for pipeline welds, which are used to locate welds between sections in the pipeline. When locating the welds, the digital positioning device is placed at the weld to be located, and a GPS device is built in and turned on to record the position data of the welds. However, this method is not accurate enough and has a high cost; 2) A weld gap measurement device, which uses a taper measuring device to enter the weld gap in the melt pipeline for contact measurement. This contact measurement has a low degree of automation; 3) An improved pipeline weld automatic detection algorithm, which determines the main direction of the pipeline by calculating the gradient-direction histogram of the pipeline image, enhances the characteristics of the weld by HSV color space conversion, and realizes weld positioning by template matching, but only realizes the image positioning of the weld from a two-dimensional perspective, and cannot provide a three-dimensional measurement; 4) Weld surface quality detection based on structured light, which uses a random sampling consistency algorithm to fit the plane to segment the weld point cloud, uses the principal component analysis algorithm to obtain the main direction of the weld point cloud, obtains the weld contour line by point cloud slicing, and analyzes the weld surface quality in combination with the slope. This method cannot calculate the width and height of the weld. Summary of the invention

[0005] In view of the defects in the above-mentioned prior art and the existing practical needs, the present invention provides a method for detecting the height and width of the circumferential weld of a straight segment of a pipeline, which collects images of welded pipelines with welds from multiple angles; obtains point clouds of the pipeline welds and the straight segments before and after the welds; fits small cylinders segment by segment with the weld design width as the step size; iteratively fuses adjacent cylindrical segments of the same radius to separate the straight segment and the weld coarse positioning segment; calculates the distance from the point cloud of the weld coarse positioning segment to the cylinder axis of the straight segment to obtain the precise positioning of the weld; calculates the difference between the maximum value of the distance from the weld point cloud to the pipeline axis and the pipeline radius to obtain the weld height; projects the weld point cloud to the pipeline axis to obtain a new point cloud, calculates the maximum distance between the points of the new point cloud, and obtains the weld width.

[0006] The technical solution adopted by the present invention to achieve the above-mentioned purpose is:

[0007] A method for detecting the height and width of a circumferential weld of a pipeline straight segment is used for detecting the weld positioning after welding two known straight pipeline segments; the method comprises the following steps:

[0008] Collect images of welded pipelines with welds from multiple angles and fuse them into original point clouds; preliminarily estimate candidate areas of weld circumferential point clouds based on weld design parameters;

[0009] Taking the weld design width as the step length, the candidate area of ​​the weld circumferential point cloud is axially cut into sections, and each section of the small cylinder is fitted one by one to obtain the radius and axis of the cylinder;

[0010] Iteratively merge adjacent cylindrical segments to segment the weld rough positioning segment and the two straight line segments A and B on both sides of the segment;

[0011] The two straight pipelines are further fitted into a fused pipeline passing through the weld, and the distance from the point cloud of the rough positioning segment of the weld to the axis of the fused pipeline is calculated to obtain the precise point cloud P of the weld;

[0012] Calculate the distance from the precise point cloud of the weld to the axis of the fused pipeline, and take the difference between the maximum distance and the radius of the fused pipeline as the weld height; project the precise point cloud of the weld onto the axis of the fused pipeline to obtain the projected point cloud P1, and calculate the span of the projected point cloud on the axis as the weld width, so as to finally identify the weld on the welding pipeline.

[0013] The multi-angle acquisition of the welding pipeline image with the weld is to evenly arrange a number of positioning points around the weld pipeline, use multiple cameras to simultaneously shoot the weld images of the corresponding angles at the respective positioning points, or use a single camera to shoot the weld images of the corresponding angles at the positioning points one by one; or control the welding pipeline to self-rotate a single camera at a preset position with the axial direction as the center to show different angles, so that it can shoot and obtain the weld images at multiple angles.

[0014] The fusion into the original point cloud is to fuse the local weld images collected from multiple angles, and filter out abnormal points and interfering noise points through filtering and denoising to obtain a welding pipeline point cloud with a weld and a circumferential integrity.

[0015] The weld seam design parameter is the weld seam design width d required by the welding process.

[0016] The candidate area of ​​the weld point cloud is preliminarily estimated based on the welding parameters, including: taking the weld design width d required by the process as a reference, defining several multiples N×d of the weld design width d as an integer N>9 to further identify the axial span of the weld, and narrowing the point cloud range to obtain the candidate area of ​​the weld circumferential point cloud.

[0017] The iterative fusion of adjacent cylindrical segments to segment the weld rough positioning segment and two straight line segments A and B on both sides thereof includes:

[0018] If the radius difference and axis misalignment of adjacent cylindrical segments meet the error threshold, the point cloud data of adjacent cylindrical segments are fused to generate a new cylindrical segment and obtain a new radius and axis.

[0019] The above process is repeated iteratively to traverse all small cylinders, and finally three new cylinder segments are generated;

[0020] The cylindrical section with the largest radius and the largest angle between its axis and other axes is used as the rough positioning section of the weld, and the other two cylindrical sections are used as the straight pipelines A and B on both sides of the rough positioning section of the weld.

[0021] The two straight pipe sections A and B are further fitted into a fused cylindrical section passing through the weld, and the distance from the point cloud of the weld rough positioning section to the axis of the fused cylindrical section is calculated to achieve accurate positioning of the weld, including:

[0022] The point clouds of the cylindrical segments A and B before and after the rough positioning segment of the weld are fused, and the cylindrical equation is fitted to obtain the axis L and radius R of the fused cylindrical segment;

[0023] The distance h from any point cloud in the rough positioning segment of the weld to the axis of the fused cylindrical segment is calculated. If the difference between h and R is greater than the threshold, it is considered to be the weld point cloud P, and the precise positioning of the weld is obtained.

[0024] The span is the maximum value of the distance between any two points in the weld point cloud P and the projection point cloud P1.

[0025] The present invention has the following beneficial effects and advantages:

[0026] The method of the present invention provides a method for detecting the circumferential weld height and width of a straight segment pipeline. By combining the design model parameters, small cylinders are fitted segment by segment in the pipeline point cloud with the weld design width as the step size and iterative analysis is performed, thereby realizing integration with the pipeline design information. This method is applicable to pipelines of different diameters, can realize accurate positioning of welds, and can realize high-precision positioning and identification of weld width and height. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a flow chart of the method of the present invention;

[0028] Figure 2 Schematic diagram of weld width calculation according to the method of the present invention. DETAILED DESCRIPTION

[0029] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation method of the present invention is described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the invention, so the present invention is not limited by the specific implementation disclosed below.

[0030] like Figure 1 FIG. 1 is a flow chart of a method for detecting the height and width of a circumferential weld of a pipeline straight segment according to the present invention, comprising the following steps:

[0031] Capture images of welded pipelines with welds from multiple angles;

[0032] Obtain the point cloud of the pipeline weld and the straight line segments before and after the weld;

[0033] Enter the design model template;

[0034] Fit the small cylinder segment by segment with the weld design width as the step length;

[0035] Iteratively merge adjacent cylindrical segments of the same radius to segment straight line segments and weld rough positioning segments;

[0036] Calculate the distance from the weld rough positioning segment point cloud to the straight segment cylinder axis to achieve accurate weld positioning;

[0037] Calculate the difference between the maximum value of the distance from the weld point cloud to the pipeline axis and the pipeline radius to obtain the weld height;

[0038] The weld point cloud is projected onto the pipeline axis to obtain a new point cloud, and the maximum distance between the points of the new point cloud is calculated to obtain the weld width.

[0039] like Figure 2 As shown, Figure 2The schematic diagram of the weld width calculation method of the present invention is as follows: Figure 2 The following are some key steps to explain in detail:

[0040] Step 1. Collect images of welded pipelines with welds from multiple angles and fuse them into original point clouds;

[0041] Point cloud data can be collected in the following three ways: arrange 6 positioning points around the weld pipeline, use 6 cameras to simultaneously shoot weld images of corresponding angles, or use a single camera to shoot weld images of corresponding angles at 6 positioning points one by one; or control the weld pipeline to rotate around the axis and show different angles to a single camera at a preset position, so that it can shoot and obtain weld images from multiple angles. In this example, line structured light is used as the light source to illuminate the weld part of the weld pipeline, and the camera is a laser scanning camera.

[0042] The local point clouds at various angles are fused into the initial point cloud using the ICP point cloud registration method, and the abnormal points and interfering noise points are filtered out through filtering and denoising to obtain a clean original point cloud.

[0043] Step 2. Obtain the original point cloud of the pipeline weld and the straight line segments before and after the weld, including:

[0044] Obtain a complete circumferential point cloud with a distance of not less than 4 times the weld width d before and after the weld of the straight section of the pipeline. If the theoretical design width of the weld is 5mm, then in addition to the weld design width d, a point cloud at least 20mm long should be retained before and after, that is, a point cloud with a length of at least 45mm and a width should be retained as the candidate weld area.

[0045] Step 3. Enter the design model template, including:

[0046] The method of the present invention is a calculation and identification performed in a computer three-dimensional model software, so it is necessary to input relevant design model parameters of the pipeline weld, including the diameters of the front and rear straight segments A and B, and the design width d and height of the weld.

[0047] Step 4. Fit the small cylinder segment by segment with the weld design width as the step length, including:

[0048] In the weld candidate area, at the starting position of the input point cloud, with the weld design width d as the step length, the candidate area point cloud is divided into multiple circumferential small point clouds with a length of the weld design width d, and each circumferential small point cloud is fitted with a small cylinder to obtain the corresponding radius and axis.

[0049] Step 5. Iteratively merge adjacent cylindrical segments of the same radius to segment straight line segments and weld rough positioning segments, including:

[0050] In the weld candidate area, starting from the small cylindrical segment at the starting position, moving towards the small cylindrical segment at the end, the radius and axis of the two adjacent small cylindrical segments are analyzed and compared in sequence. When the radius difference is less than 0.1mm and the axis misalignment is less than 0.05 degrees, it is considered to be the same cylinder, that is, the two point clouds are fused and a new cylinder is generated by fitting. The above process is iterated until the cylindrical point cloud cannot be fused, and the cylinder is fitted again to obtain the radius and axis. The cylindrical segment with the largest radius and the largest angle between the axis direction and other axes is the weld area, that is, the weld rough positioning segment.

[0051] It should be noted that the threshold of 0.1mm radius difference in step 5 is obtained by comprehensively considering the weld design height (greater than 0.5mm), thermal deformation caused by welding and the accuracy of the input point cloud. When the input point cloud accuracy is higher or the weld design height is higher, this threshold can be further relaxed; when the weld design height is lower, this threshold can be reduced accordingly.

[0052] Step 6. Calculate the distance from the weld rough positioning segment point cloud to the straight line segment cylinder axis to achieve accurate weld positioning, including:

[0053] The cylindrical point clouds before and after the rough positioning section of the weld are fused, and the cylinder equation is fitted to obtain the pipeline axis L and radius R. The distance h from the point cloud of the rough positioning section of the weld to the pipeline axis is calculated, and the difference between h and R is calculated. When the difference is greater than 0.25mm, it is considered to be the precise point cloud P of the weld. At this point, the precise positioning of the weld is obtained.

[0054] It should be noted that the threshold of the difference greater than 0.25 mm in step 5 is a threshold value obtained by comprehensively considering the weld design height (greater than 0.5 mm), point cloud accuracy and the theoretical height of the weld edge (the weld is an arch with the edge lower than the middle).

[0055] Step 7. Calculate the difference between the maximum value of the distance from the weld precise point cloud P to the fusion pipeline axis and the pipeline radius to obtain the weld height, including:

[0056] The precise weld point cloud P and pipeline axis L obtained in step 6 are traversed to calculate the maximum distance from the precise weld point cloud P to the fused pipeline axis L, and the difference is calculated with the pipeline radius to obtain the weld height.

[0057] It should be noted that since the input point cloud in step 1 is a point cloud that has been filtered and denoised, the maximum value in step 7 will not be obviously unreasonable, such as being greater than 10 times the design height.

[0058] Step 8. Project the weld point cloud P to the fusion pipeline axis to obtain a new point cloud P1, calculate the maximum distance between the points of the new point cloud P1, and obtain the weld width, including:

[0059] The weld point cloud P and the fused pipeline axis L obtained in step 6 are projected onto the fused pipeline axis L to obtain a new point set P1. The interior of P1 is traversed to calculate the distance between any two points to obtain the maximum distance, that is, the weld width.

[0060] In summary, the method of the present invention provides a method for detecting the height and width of the circumferential weld of a straight segment of a pipeline. It is combined with pipeline design information, is not limited by pipe diameter and material, can be applied to situations where the front and rear pipe diameters change, and can accurately locate the weld position by analyzing the three-dimensional point cloud. It has high efficiency and high precision, and is suitable for use in scenarios where there is a need to detect the height and width of the weld of a straight segment pipeline.

[0061] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for detecting the height and width of a circumferential weld of a pipeline straight section, characterized in that: Used for detecting the weld position after welding two known straight pipe sections; the method comprises the following steps: Collect images of welded pipelines with welds from multiple angles and fuse them into original point clouds; preliminarily estimate candidate areas of weld circumferential point clouds based on weld design parameters; Taking the weld design width as the step length, the candidate area of ​​the weld circumferential point cloud is axially cut into sections, and each section of the small cylinder is fitted one by one to obtain the radius and axis of the cylinder; Iteratively merge adjacent cylindrical segments to segment the weld rough positioning segment and the two straight line segments A and B on both sides of the segment; The two straight pipelines are further fitted into a fused pipeline passing through the weld, and the distance from the point cloud of the rough positioning segment of the weld to the axis of the fused pipeline is calculated to obtain the precise point cloud P of the weld; Calculate the distance from the precise point cloud of the weld to the axis of the fused pipeline, and take the difference between the maximum distance and the radius of the fused pipeline as the weld height; project the precise point cloud of the weld onto the axis of the fused pipeline to obtain the projected point cloud P1, and calculate the span of the projected point cloud on the axis as the weld width, so as to finally identify the weld on the welding pipeline.

2. A method for detecting the height and width of a circumferential weld of a pipeline straight section according to claim 1, characterized in that: The multi-angle acquisition of the welding pipeline image with the weld is to evenly arrange a number of positioning points around the weld pipeline, use multiple cameras to simultaneously shoot the weld images of the corresponding angles at the respective positioning points, or use a single camera to shoot the weld images of the corresponding angles at the positioning points one by one; or control the welding pipeline to self-rotate a single camera at a preset position with the axial direction as the center to show different angles, so that it can shoot and obtain the weld images at multiple angles.

3. A method for detecting the height and width of a circumferential weld of a pipeline straight section according to claim 1, characterized in that: The fusion into the original point cloud is to fuse the local weld images collected from multiple angles, and filter out abnormal points and interfering noise points through filtering and denoising to obtain a welding pipeline point cloud with a weld and a circumferential integrity.

4. A method for detecting the height and width of a circumferential weld of a pipeline straight section according to claim 1, characterized in that: The weld seam design parameter is the weld seam design width d required by the welding process.

5. A method for detecting the height and width of a circumferential weld of a pipeline straight section according to claim 1, characterized in that: The candidate area of ​​the weld point cloud is preliminarily estimated based on the welding parameters, including: taking the weld design width d required by the process as a reference, defining several multiples N×d of the weld design width d as an integer N>9 to further identify the axial span of the weld, and narrowing the point cloud range to obtain the candidate area of ​​the weld circumferential point cloud.

6. A method for detecting the height and width of a circumferential weld of a pipeline straight section according to claim 1, characterized in that: The iterative fusion of adjacent cylindrical segments to segment the weld rough positioning segment and two straight line segments A and B on both sides thereof includes: If the radius difference and axis misalignment of adjacent cylindrical segments meet the error threshold, the point cloud data of adjacent cylindrical segments are fused to generate a new cylindrical segment and obtain a new radius and axis. The above process is repeated iteratively to traverse all small cylinders, and finally three new cylinder segments are generated; The cylindrical section with the largest radius and the largest angle between its axis and other axes is used as the rough positioning section of the weld, and the other two cylindrical sections are used as the straight pipelines A and B on both sides of the rough positioning section of the weld.

7. A method for detecting the height and width of a circumferential weld of a pipeline straight section according to claim 1, characterized in that: The two straight pipe sections A and B are further fitted into a fused cylindrical section passing through the weld, and the distance from the point cloud of the weld rough positioning section to the axis of the fused cylindrical section is calculated to achieve accurate positioning of the weld, including: The point clouds of the cylindrical segments A and B before and after the rough positioning segment of the weld are fused, and the cylindrical equation is fitted to obtain the axis L and radius R of the fused cylindrical segment; The distance h from any point cloud in the rough positioning segment of the weld to the axis of the fused cylindrical segment is calculated. If the difference between h and R is greater than the threshold, it is considered to be the weld point cloud P, and the precise positioning of the weld is obtained.

8. The method for detecting the height and width of the circumferential weld of a straight segment pipeline according to claim 1, characterized in that: The span is the maximum value of the distance between any two points in the weld point cloud P and the projection point cloud P1.

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