A device for detecting surface defects and straightness of large-diameter welded pipes

Abstract

The present invention provides a large-diameter welded pipe surface defect and straightness detection device, comprising a bracket, a first camera, a second camera, and an image processing system. The bracket is provided with a through-hole through which the welded pipe passes. Multiple groups of first cameras are evenly distributed circumferentially on one side of the bracket, with the imaging ends of the first cameras all facing the center of the through-hole. At least three groups of second cameras are evenly spaced on the bracket along the direction of movement of the welded pipe. The first and second cameras are electrically connected to the image processing system, which is used to process data collected by the first and second cameras to identify surface defects of the welded pipe and calculate the straightness of the welded pipe. The advantage of the present invention is that the detection device solves the problem that existing equipment cannot simultaneously detect surface defects and straightness of welded pipes. It can complete the simultaneous detection of surface defects and straightness of welded pipes in a short period of time, greatly improving detection efficiency.

Description

Technical Field

[0001] The invention relates to the field of large-diameter welded pipe production and testing equipment, and in particular to a large-diameter welded pipe surface defect and straightness detection device. Background Art

[0002] Large-diameter welded pipes are increasingly used in modern manufacturing, particularly in the oil, gas, chemical, and power industries. These sectors place extremely high demands on the quality of welded pipes, particularly in terms of pressure resistance, corrosion resistance, and structural stability. Therefore, ensuring the surface quality and accurate straightness of welded pipes has become a critical aspect of the production process.

[0003] Welded pipes are prone to various surface defects during production, especially during the welding phase. These defects not only affect the pipe's aesthetics but can also degrade its mechanical properties, increasing safety risks during use. Common surface defects include porosity, inclusions, incomplete welds, cracks, and rust. These defects are often closely related to a variety of factors, including raw material quality, welding process parameters, welding environment, and post-processing.

[0004] In addition to surface defects, straightness is also a critical quality indicator for welded pipes. Straightness refers to the degree of curvature along the length of the pipe, affecting the pipe's docking accuracy and structural stability during installation and operation. Unsatisfactory straightness can reduce fluid delivery efficiency within the piping system and even lead to safety hazards such as leaks. Therefore, straightness testing of welded pipes is crucial.

[0005] While existing inspection technologies have made some progress in detecting surface defects and straightness in welded pipes, many shortcomings remain. Traditional inspection methods typically rely on manual visual inspection or simple measuring instruments, resulting in low efficiency and poor accuracy. Furthermore, existing equipment is often unable to simultaneously detect both surface defects and straightness in welded pipes. This is because most traditional inspection methods focus on a single aspect and lack comprehensive functionality. While some equipment can perform visual inspection or laser ranging for surface defects, technical limitations prevent them from effectively integrating both inspection tasks simultaneously. This results in the inability to obtain comprehensive quality information in real time during the welded pipe production process, increasing the risk of subsequent inspection and rework. Therefore, there is an urgent need for a new type of equipment that can simultaneously meet the detection needs for both surface defects and straightness in welded pipes. Summary of the Invention

[0006] The technical problem to be solved by the present invention is how to simultaneously meet the detection requirements of surface defects and straightness of welded pipes.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0008] A device for detecting surface defects and straightness of large-diameter welded pipes includes a bracket, a first camera, a second camera, and an image processing system. The bracket is provided with a through-hole through which the welded pipe passes. Multiple groups of first cameras are circumferentially distributed on one side of the bracket, with the imaging ends of the first cameras all facing the center of the through-hole. At least three groups of second cameras are evenly spaced on the bracket along the direction of movement of the welded pipe. The first and second cameras are electrically connected to the image processing system. The welded pipe passes through the first and second cameras in sequence, and complete circular screw hole data and multiple equally spaced arc profile data of the welded pipe at the same moment are obtained respectively. The image processing system is used to process the data collected by the first and second cameras to identify surface defects of the welded pipe and calculate the straightness of the welded pipe.

[0009] The image processing system calculates the straightness of the welded pipe as follows:

[0010] The process of confirming the weld point: fit an ellipse based on the complete circle contour data, take three adjacent contour points of the ellipse, calculate the distance from the middle contour point to the line connecting the other two contour points, traverse all contour points and obtain the contour point with the maximum value of max_dist among all distances, which is the weld point;

[0011] The process of eliminating errors caused by the natural rotation of the welded pipe is as follows: Based on the angular positions θ1 and θ2 of the weld points of the complete circle at two different times t1 and t2, the rotation angle θ = θ1-θ2 is obtained; the contour of the complete circle at time t1 is rotated by an angle θ so that the welds of the complete circles at time t1 and time t2 are at the same angular position; then, a nearest neighbor search is performed on the complete circle at time t1 and the arc at time t2; the optimal transformation matrix from the source point cloud to the target point cloud is solved based on the found nearest neighbor point cloud; the calculated transformation matrix is ​​applied to the complete circle at time t1, and a complete circle is obtained to replace the arc at time t2; finally, this operation is repeated for all complete circles, thereby eliminating the error caused by the natural rotation of the welded pipe as it advances;

[0012] Eliminating the jitter error of the welded pipe: Assume that the complete circle contour data obtained from the six arc contour data at two different times t1 and t2 based on the steps of eliminating the error caused by the natural rotation of the welded pipe are: complete circle contours c1, c2, c3 at time t1, and complete circle contours c4, c5, c6 at time t2, where c2 and c4 are at the same position of the welded pipe, and c3 and c5 are also at the same position of the welded pipe. The transformation matrices between the corresponding circle contours are calculated as m_24 and m_35. The transformation matrices m_24 and m_35 are weighted averaged to obtain a new matrix m_combined, which is then applied to c6 to obtain c_final, which is closer to the state of c6 at time t1. Finally, repeat this operation for all replaced complete circles to obtain a contour set c_finals.

[0013] The process of straightness calculation: According to the contour set c_finals, the straightness of the welded pipe at any position in 360° is calculated.

[0014] Furthermore, the specific calculation process of the weld point confirmation step is as follows: first, an ellipse fitting operation is performed on each complete circle contour in the XOZ plane to obtain the center coordinates o(x o ,z o ), further through the formula Find each contour point p(x i ,z i ) on the circle; then, take the contour point p and two points p with a distance n to the left and right of point p l ,p r , where n is equal to 1 / 2 of the number of contour points occupied by the weld, find the distance from point p to p l and p r Line L pl,pr The distance dist; where L pl,pr The general equation of a straight line is: Ax+Bz+C=0, each point p(x i ,z i ) to the straight line L pl,pr The distance is: Finally, all contour points are traversed to obtain the contour point with the maximum value of max_dist among all distances, which is the weld point.

[0015] This detection device solves the problem that existing equipment cannot simultaneously detect surface defects and straightness of welded pipes. It can complete the simultaneous detection of surface defects and straightness of welded pipes in a short time, greatly improving the detection efficiency. Compared with traditional manual detection and step-by-step detection, the overall detection time is greatly shortened.

[0016] Furthermore, in the step of eliminating the error caused by the natural rotation of the welded pipe, the optimal transformation matrix formula from the source point cloud to the target point cloud is: Where R is the rotation matrix, p′ i is the target point cloud, p i is the source point cloud and N is the number of points.

[0017] Furthermore, the calculation process of the straightness calculation step is as follows: all the contours are obtained by scanning in the XOZ plane, and the end point connection method is used to calculate, taking a1 and a N The line connecting the two points is taken as the baseline L, and then the distances from all the remaining contour points to the baseline L are calculated. The maximum distance is taken as the straightness of the angle, and the position of the point with the maximum distance is recorded.

[0018] Furthermore, the bracket includes a first bracket, a second bracket, a connecting shaft and a fixed frame. The first bracket and the second bracket are connected by multiple connecting shafts. The through hole coaxially penetrates the first bracket and the second bracket. A fixed frame is fixed between the first bracket and the second bracket along the movement direction of the welding pipe. Multiple groups of second cameras are fixed on the fixed frame, and the first camera is set on the first bracket.

[0019] Furthermore, a profile frame is fixed on both the first bracket and the second bracket.

[0020] Furthermore, the first camera is arranged on the first bracket via a fixing seat.

[0021] Furthermore, the fixing seat is a retractable fixing seat, so that the first camera can be retracted along the movement direction of the welding pipe.

[0022] Furthermore, the first bracket is provided with a mounting hole for mounting the fixing seat.

[0023] The advantages of the present invention are:

[0024] This detection device solves the problem that existing equipment cannot simultaneously detect surface defects and straightness of welded pipes. It can complete the simultaneous detection of surface defects and straightness of welded pipes in a short time, greatly improving the detection efficiency. Compared with traditional manual detection and step-by-step detection, the overall detection time is greatly shortened.

[0025] Automatic calculation by the image processing system can effectively reduce the impact of human factors on the inspection results and improve the accuracy of inspection; automatic identification and marking of defect types avoids missed inspections and false inspections that may be caused by manual inspection, ensuring the reliability of welded pipe quality.

[0026] In addition, the detection device also has real-time online detection capabilities, which can promptly detect any abnormal conditions in the production process and quickly feedback to production management personnel, thereby reducing the influx of unqualified products, reducing rework and scrap rates, and further saving production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the structure of an embodiment of the present invention;

[0028] Figure 2 A schematic diagram of a partial structure of an embodiment of the present invention;

[0029] Figure 3 This is a front view of the first bracket according to an embodiment of the present invention;

[0030] Figure 4 This is a flowchart of a method for calculating the straightness of a welded pipe according to an embodiment of the present invention;

[0031] Figure 5Schematic diagram of the process of eliminating the natural rotation of the welded pipe in an embodiment of the present invention;

[0032] Figure 6 Schematic diagram of eliminating weld pipe vibration in an embodiment of the present invention. DETAILED DESCRIPTION

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with 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. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0034] See Figures 1 to 3 This embodiment describes a device for detecting surface defects and straightness of a large-diameter welded pipe, including a bracket 1, a first camera 2, a second camera 3, and an image processing system (not shown).

[0035] The bracket 1 includes a first bracket 11, a second bracket 12, a connecting shaft 13, a fixing frame 14, and a profile frame 15. The first bracket 11 and the second bracket 12 are connected by multiple connecting shafts 13. The first bracket and the second bracket are provided with through holes 101 for the welding pipe 4 to pass through. The fixing frame 14 is fixed between the first bracket 11 and the second bracket 12 along the movement direction of the welding pipe 4. The profile frame 15 is fixed to the first bracket 11 and the second bracket 12 along the circumference. In the embodiment, the first bracket 11 and the second bracket 12 are both aluminum alloy plates.

[0036] Multiple sets of first cameras 2 are evenly distributed circumferentially on one side of the first bracket 11, with the imaging ends of the first cameras 2 facing the center of the through-hole 101, enabling the first cameras 2 to capture subtle surface defects on the welded pipe 4. It should be noted that the number of first cameras 2 is determined by the aperture of the welded pipe 4. A larger aperture requires a greater number of first cameras 2. In this embodiment, there are twelve sets of first cameras 2.

[0037] Specifically, the first bracket 11 is provided with mounting holes 111 corresponding to the number and positions of the first cameras 2. Each group of first cameras 2 is set on the mounting hole 111 through a fixing seat 5. The fixing seat 5 is a retractable fixing seat, so that the first camera 2 can be retracted along the movement direction of the welding pipe 4. In this embodiment, the fixing seat 5 is set as a retractable fixing seat, which can ensure that the camera end of each group of first cameras 2 is on the same plane, and the position of the first camera 2 is calibrated; through the setting of the mounting hole 111, not only the retractable movement of the first camera 2 on the fixing seat 5 is facilitated, but also the weight is reduced.

[0038] A plurality of groups of second cameras 3 are fixed on the fixing frame 14 at equal intervals along the moving direction of the welded pipe 4 , so that the second cameras 3 can monitor the straightness of the welded pipe 4 in real time.

[0039] The first camera 2 and the second camera 3 are both electrically connected to the image processing system, and the image processing system is used to process the images captured by the first camera 2 and the second camera 3, identify surface defects of the welded pipe, and calculate the straightness of the welded pipe.

[0040] The operating principle of this embodiment is as follows: a welded pipe 4 on the production line is placed through a through-hole 101 and moves along its length, passing through a first camera 2 and a second camera 3 in sequence. The first camera 2 scans the surface of the welded pipe 4 in real time, capturing subtle surface defects. The acquired three-dimensional point cloud data is transmitted to an image processing system for analysis. An image processing algorithm automatically identifies and classifies surface defects on the welded pipe 4. Simultaneously, the second camera 3 captures the geometric shape of the welded pipe 4 in real time. The first and second cameras 2 and 3 respectively obtain data on the complete circular screw hole and the contours of multiple equally spaced arcs on the welded pipe 4 at the same moment. The image processing system then calculates the straightness data of the welded pipe 4 to determine whether the quality of the welded pipe 4 meets the requirements.

[0041] In this embodiment, the detection device solves the problem that existing equipment cannot simultaneously detect surface defects and straightness of welded pipes. It can complete the simultaneous detection of surface defects and straightness of welded pipes in a short time, greatly improving the detection efficiency. Compared with traditional manual detection and step-by-step detection, the overall detection time is greatly shortened.

[0042] Automatic calculation by the image processing system can effectively reduce the impact of human factors on the inspection results and improve the accuracy of inspection; automatic identification and marking of defect types avoids missed inspections and false inspections that may be caused by manual inspection, ensuring the reliability of welded pipe quality.

[0043] In addition, the detection device also has real-time online detection capabilities, which can promptly detect any abnormal conditions in the production process and quickly feedback to production management personnel, thereby reducing the influx of unqualified products, reducing rework and scrap rates, and further saving production costs.

[0044] The specific process of calculating the straightness of the welded pipe by the image processing system is as follows:

[0045] Step 1: Confirm the weld point. The welded pipe is made of a rectangular steel plate rolled into a tube. The weld is welded firmly. The weld is obvious and higher than the surface of the pipe. This step locates the angle of the weld on the pipe based on the complete circle profile data. Specifically, since the cross section of the welded pipe cannot meet the perfect circle standard, an ellipse is first fitted to each complete circle profile in the XOZ plane to obtain the center coordinates o(x o ,zo ), further through the formula Find each contour point p(x i ,z i ) on the circle. Then, take the contour point p and two points p with a distance n to the left and right of point p. l ,p r , where n is equal to 1 / 2 of the number of contour points occupied by the weld, find the distance from point p to p l and p r Line L pl,pr The distance dist. Among them, L pl,pr The general equation of a straight line is: Ax+Bz+C=0, each point p(x i ,z i ) to the straight line L pl,pr The distance is: Since the weld point is higher than the weld pipe surface, all contour points are traversed to obtain the contour point with the maximum value of max_dist among all distances, which is the weld point.

[0046] Step 2: Eliminate the error caused by the natural rotation of the welded pipe. Based on the weld position in step 1, eliminate the error caused by the natural rotation of the steel pipe when it moves forward.

[0047] Step 2.1: If Figure 4 As shown, the steel pipe rotates irregularly clockwise or counterclockwise when it moves forward ( Figure 5 According to step 1, the angular positions θ1 and θ2 of the complete circular weld points at two different times t1 and t2 can be obtained, and then the rotation angle θ = θ1-θ2 can be obtained.

[0048] Step 2.2: Based on the value of θ obtained in step 2.1, rotate the full circle contour at time t1 by an angle of θ so that the weld seams of the full circles at time t1 and time t2 are at the same angular position. Then, perform a nearest neighbor search on the full circle at time t1 and the arc at time t2. Based on the nearest neighbor point cloud found, minimize the error in the formula to solve the optimal transformation matrix from the source point cloud to the target point cloud. The formula is: Where R is the rotation matrix, p′ i is the target point cloud, p i is the source point cloud, N is the number of points, and the calculated transformation matrix is ​​applied to the complete circle at time t1 to obtain a complete circle to replace the arc at time t2. The complete circle at time t2 is used to fill the arc at time t3, and so on. Finally, this operation is repeated for all complete circles, thereby eliminating the error caused by the natural rotation of the steel pipe when it moves forward.

[0049] Step 3: Eliminate the vibration error of the welded pipe. According to step 2, all the complete circle profile data after eliminating the rotation error is obtained, and the error effect caused by the vibration of the steel pipe during forward movement is further eliminated.

[0050] Step 3.1: From step 2.2, we can see that the original steel pipe arc data is replaced with complete circle data, such as Figure 6 As shown, assuming that there are complete circular contours c1, c2, and c3 at time t1, and complete circular contours c4, c5, and c6 at time t2, since c2 and c4 are the original contour data obtained at the same position of the welded pipe, there is only a relative change in the spatial position. Similarly, c3 and c5 are also a corresponding set of circular contours (in this embodiment, at least three arcs are required to eliminate jitter, and only equal spacing can ensure the correspondence between c2 and c4, and c3 and c5). The transformation matrix between the corresponding circular contours is calculated using the least squares method as m_24 and m_35.

[0051] Step 3.2: Perform a weighted average of the transformation matrices m_24 and m_35 with a weight of 0.5 to obtain a new matrix m_combined. Then apply this to c6 to obtain c_final, which is closer to the state of c6 at time t1. Finally, repeat this operation for all the replaced complete circles to obtain a contour set c_finals, thereby eliminating the jitter error caused by the steel pipe moving forward.

[0052] Step 4: Straightness calculation step. According to the contour set c_finals obtained in step 3.2, calculate the straightness of any position of the whole tube 360°. It is known that all contours are obtained by scanning in the XOZ plane. The present invention uses the end point connection method to calculate. For example, to calculate the straightness in the 90° direction, you can specify a point a in all contours with an x ​​coordinate of 0 and a z coordinate greater than 0. i (i=1,2,...,N), take a1 and a N The line connecting the two points is used as the reference line L. The distances from all remaining contour points to the reference line L are then calculated. The maximum distance is taken as the straightness of that angle, and the position of the point with the maximum distance is recorded. Similarly, the straightness of any position in the entire 360° tube can be calculated.

[0053] Based on the original data of the complete circular profile and three equally spaced arc profiles in the forward direction, this embodiment uses a self-developed algorithm to locate the weld position and eliminates the influence of the natural rotation and jitter of the steel pipe when it is conveyed on the roller on the measurement of straightness. It can accurately realize the dynamic measurement of the straightness of large-diameter welded pipes at any position of 360°; this embodiment solves the shortcomings of manual visual and manual wire drawing methods of measuring straightness, saves a lot of manpower, material and financial resources, and improves the efficiency and accuracy of measurement results.

[0054] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A device for detecting surface defects and straightness of large-diameter welded pipes, characterized in that: The system comprises a bracket, a first camera, a second camera, and an image processing system. The bracket is provided with a through-hole through which the welding pipe passes. Multiple groups of first cameras are evenly distributed circumferentially on one side of the bracket. The imaging ends of the first cameras are all set toward the center of the through-hole. At least three groups of second cameras are evenly spaced on the bracket along the movement direction of the welding pipe. The first camera and the second camera are electrically connected to the image processing system. The welding pipe passes through the first camera and the second camera in sequence, and complete circular screw hole data and multiple equally spaced circular arc profile data of the welding pipe at the same moment are respectively obtained. The image processing system is used to process the data collected by the first camera and the second camera to identify surface defects of the welding pipe and calculate the straightness of the welding pipe. The image processing system calculates the straightness of the welded pipe as follows: The process of confirming the weld point: fit an ellipse based on the complete circle contour data, take three adjacent contour points of the ellipse, calculate the distance from the middle contour point to the line connecting the other two contour points, traverse all contour points and obtain the contour point with the maximum value of max_dist among all distances, which is the weld point; The process of eliminating errors caused by the natural rotation of the welded pipe is as follows: Based on the angular positions θ1 and θ2 of the weld points of the complete circle at two different times t1 and t2, the rotation angle θ = θ1-θ2 is obtained; the contour of the complete circle at time t1 is rotated by an angle θ so that the welds of the complete circles at time t1 and time t2 are at the same angular position; then, a nearest neighbor search is performed on the complete circle at time t1 and the arc at time t2; the optimal transformation matrix from the source point cloud to the target point cloud is solved based on the found nearest neighbor point cloud; the calculated transformation matrix is ​​applied to the complete circle at time t1, and a complete circle is obtained to replace the arc at time t2; finally, this operation is repeated for all complete circles, thereby eliminating the error caused by the natural rotation of the welded pipe as it advances; Eliminating the jitter error of the welded pipe: Assume that the complete circle contour data obtained from the six arc contour data at two different times t1 and t2 based on the steps of eliminating the error caused by the natural rotation of the welded pipe are: complete circle contours c1, c2, c3 at time t1, and complete circle contours c4, c5, c6 at time t2, where c2 and c4 are at the same position of the welded pipe, and c3 and c5 are also at the same position of the welded pipe. The transformation matrices between the corresponding circle contours are calculated as m_24 and m_35. The transformation matrices m_24 and m_35 are weighted averaged to obtain a new matrix m_combined, which is then applied to c6 to obtain c_final, which is closer to the state of c6 at time t1. Finally, repeat this operation for all replaced complete circles to obtain a contour set c_finals. The process of straightness calculation: According to the contour set c_finals, the straightness of the welded pipe at any position in 360° is calculated.

2. A large diameter welded pipe surface defect and straightness detection device according to claim 1, characterized in that: The specific calculation process of the weld point confirmation step is as follows: first, an ellipse fitting operation is performed on each complete circle contour in the XOZ plane to obtain the center coordinates o(x o ,z o ), further through the formula Find each The angle value of each contour point p(xi,zi) on the circle is calculated. Then, take the contour point p and two points pl and pr with an interval of n to the left and right of point p, where n is equal to 1 / 2 of the number of contour points occupied by the weld, and calculate the distance dist from point p to the line connecting pl and pr, Lpl,pr. ​​The general equation of the line Lpl,pr is: Ax+Bz+C=0. The distance from each point p(xi,zi) to the line Lpl,pr is: Finally, all contour points are traversed to obtain the contour point with the maximum value of max_dist among all distances, which is the weld point.

3. A large diameter welded pipe surface defect and straightness detection device according to claim 1, characterized in that: In the step of eliminating the error caused by the natural rotation of the welded pipe, the optimal transformation matrix from the source point cloud to the target point cloud is solved. The formula is: Where R is the rotation matrix, p i is the target point cloud, p i is the source point cloud and N is the number of points.

4. A large diameter welded pipe surface defect and straightness detection device according to any one of claims 1 to 3, characterized in that: The calculation process of the straightness calculation step is as follows: it is known that all contours are obtained by scanning in the XOZ plane, and the end point connection method is used for calculation. The line connecting points a1 and aN is taken as the baseline L, and then the distance from all remaining contour points to the baseline L is calculated. The maximum distance is taken as the straightness of the angle, and the position of the point with the maximum distance is recorded.

5. The large diameter welded pipe surface defect and straightness detection device according to claim 1, characterized in that: The bracket includes a first bracket, a second bracket, a connecting shaft and a fixing frame. The first bracket and the second bracket are connected by multiple connecting shafts. The through hole coaxially penetrates the first bracket and the second bracket. A fixing frame is fixed between the first bracket and the second bracket along the movement direction of the welding pipe. Multiple groups of second cameras are fixed on the fixing frame. The first camera is set on the first bracket.

6. A large diameter welded pipe surface defect and straightness detection device according to claim 5, characterized in that: A profile frame is fixed on both the first bracket and the second bracket.

7. The device for detecting surface defects and straightness of a large-diameter welded pipe according to claim 5, characterized in that: The first camera is arranged on the first bracket via a fixing seat.

8. The device for detecting surface defects and straightness of a large-diameter welded pipe according to claim 7, characterized in that: The fixing seat is a retractable fixing seat, so that the first camera can be retracted along the moving direction of the welding pipe.

9. The device for detecting surface defects and straightness of a large-diameter welded pipe according to claim 8, characterized in that: The first bracket is provided with a mounting hole for mounting the fixing seat.

Images