Method and system for dynamically measuring straightness of large-diameter welded pipe

Abstract

The invention provides a method and system for dynamically measuring the straightness of a large-diameter welded pipe, and the method comprises the steps: carrying out the welding line positioning on the basis of the obtained data of a complete circular contour and three sections of equidistant arc contours in the advancing direction, then carrying out the rotation and transformation of the data of the complete circular contour and the arc contours, and obtaining the straightness of the large-diameter welded pipe. Therefore, the error influence on the measurement result caused by natural rotation and shaking of the steel pipe when the steel pipe is conveyed on the roller way can be eliminated, and meanwhile, the straightness of any 360-degree position of the whole pipe can be accurately measured.

Description

Technical Field

[0001] The invention relates to the technical field of welded pipe production detection, in particular to a method and a system for dynamically measuring the straightness of a large-diameter welded pipe. Background Art

[0002] Large-diameter welded pipes are one of the important products of steel enterprises. They are mainly used for long-distance continuous transportation of oil, natural gas and other products, and are mostly used in areas with complex and dangerous environmental conditions. With the increasing demand for oil and natural gas and the increasing pressure of pipeline transportation, the development trend of pipeline welded pipes towards large diameter, thick wall and high strength has become a trend. For welded pipe products, straightness is one of the important indicators to measure the quality of welded pipes. Large-diameter welded pipes will bend and deform during the forming, welding process and temperature changes, resulting in increased straightness errors and failure to meet the requirements for the use of welded pipes.

[0003] At present, there are few methods for measuring the straightness of large-diameter welded pipes in China. Most of them adopt manual measurement methods, using manual visual inspection to intuitively judge the degree of bending, and combining offline sampling methods to perform contact measurements such as manual wire drawing method and three-coordinate measurement method. Manual measurement has many problems, such as randomness, large errors, and long measurement time. Therefore, some steel companies have begun to adopt mechanical welded pipe straightness detection devices. For example, Chinese patent specification CN101769726A discloses an online detection device for the straightness of welded pipe ends, including: detection equipment, detection arm, base and base. The detection equipment includes: rolling bearings, wedge blocks, detection frames, rotary encoders, counterweights and sensors, and uses multi-laser displacement sensors to obtain welded pipe cross-section information, construct a virtual reference straight line in welded pipe space and use it to judge the straightness of the welded pipe. The device can replace manual visual inspection methods and is an online detection device that realizes automatic detection of the straightness of welded pipe ends of different specifications. Although this technology solves the problem of straightness detection of welded pipe ends, it does not eliminate the errors caused by the jitter and rotation of the welded pipe during movement in the measurement results, resulting in insufficient measurement accuracy. In addition, the device is complex to implement and is not easy to implement in the actual production environment of a steel plant, and it is impossible to dynamically and continuously measure the straightness of the entire welded pipe. Summary of the invention

[0004] The technical problem to be solved by the present invention is how to eliminate the error influence on the measurement result caused by the natural rotation and shaking of the welded pipe when it is transmitted on the roller, and at the same time accurately measure the straightness of any position of the whole pipe in 360°.

[0005] The present invention solves the above technical problems through the following technical means:

[0006] A method for dynamically measuring the straightness of a large-diameter welded pipe, wherein the welded pipe passes through a full-circle detection unit and a plurality of equally spaced arc profile detection units in sequence, and obtains complete circular screw hole data and a plurality of equally spaced arc profile data of the welded pipe at the same time; the method comprises the following steps:

[0007] Steps for 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 to obtain the contour point with the maximum value of max_dist among all distances, which is the weld point;

[0008] Steps to eliminate the error caused by natural rotation of the welded pipe: according to 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, and then the complete circle at time t1 and the arc at time t2 are searched for the nearest neighbor, and the optimal transformation matrix from the source point cloud to the target point cloud is solved based on the nearest neighbor point cloud found, 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; finally, the operation is repeated for all complete circles, thereby eliminating the error caused by the natural rotation of the welded pipe when it moves forward;

[0009] Steps for eliminating the jitter error of the welded pipe: Assume that the complete circle contour data obtained based on the steps of eliminating the error caused by the natural rotation of the welded pipe at two different times t1 and t2 are: complete circle contours c1, c2, c3 at time t1, complete circle contours c4, c5, c6 at time t2, where c2 and c4 are at the same position of the welded pipe, c3 and c5 are also at the same position of the welded pipe, and the transformation matrices between the corresponding circle contours are calculated to be m_24 and m_35, and 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, the operation is repeated for all the replaced complete circles to obtain a contour set c_finals;

[0010] Steps for calculating straightness: Calculate the straightness of the welded pipe at any position within 360° according to the contour set c_finals.

[0011] 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 ,zi ) on the circle; then, take the contour point p and two points p with an interval of 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 Connection L pl,pr The distance dist; where L pl,pr The general formula of the straight line equation 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.

[0012] Furthermore, in the step of eliminating the error caused by the natural rotation of the welded pipe, the optimal transformation matrix formula for solving 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.

[0013] Furthermore, the calculation process of the straightness calculation step is as follows: Knowing that all contours are obtained by scanning in the XOZ plane, the end point connection method is used to calculate, and a1 and a N The line connecting the two points is taken as the reference line L, and then the distances from all the remaining contour points to the reference line 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.

[0014] The present invention also provides a system for dynamically measuring the straightness of a large-diameter welded pipe, comprising:

[0015] Detection module: including a full circle detection unit and multiple equally spaced arc profile detection units that the welded pipe passes through in sequence, to obtain the complete circle screw hole data and multiple equally spaced arc profile data of the welded pipe at the same time;

[0016] Weld point confirmation module: fit an ellipse according to 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 to obtain the contour point with the maximum value of max_dist among all distances, which is the weld point;

[0017] Module for eliminating the error caused by natural rotation of welded pipe: according to 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, and then the complete circle at time t1 and the arc at time t2 are searched for the nearest neighbor, and the optimal transformation matrix from the source point cloud to the target point cloud is solved based on the nearest neighbor point cloud found, 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; finally, the operation is repeated for all complete circles, thereby eliminating the error caused by the natural rotation of the welded pipe when it moves forward;

[0018] Eliminating welding pipe jitter error module: Assume that the complete circle contour data obtained based on the steps of eliminating the error caused by natural rotation of the welding pipe at two different times t1 and t2 are: complete circle contours c1, c2, c3 at time t1, complete circle contours c4, c5, c6 at time t2, where c2 and c4 are at the same position of the welding pipe, c3 and c5 are also at the same position of the welding pipe, and the transformation matrices between the corresponding circle contours are calculated to be 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, the operation is repeated for all the replaced complete circles to obtain a contour set c_finals.

[0019] Straightness calculation module: Calculate the straightness of the welded pipe at any position of 360° based on the contour set c_finals.

[0020] Furthermore, the specific calculation process of the weld point confirmation module 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 an interval of 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 Connection L pl,pr The distance dist; where L pl,pr The general formula of the straight line equation 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.

[0021] Furthermore, in the module for eliminating the error caused by natural rotation of the welded pipe, the optimal transformation matrix formula for solving 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.

[0022] Furthermore, the calculation process of the straightness calculation module 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, and a1 and a N The line connecting the two points is taken as the reference line L, and then the distances from all the remaining contour points to the reference line 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.

[0023] The present invention also provides a processing device, comprising at least one processor and at least one memory communicatively connected to the processor, wherein: the memory stores program instructions executable by the processor, and the processor can execute the above method by calling the program instructions.

[0024] The present invention also provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer instructions, and the computer instructions enable the computer to execute the above method.

[0025] The advantages of the present invention are:

[0026] The present invention locates the weld position by using a self-developed algorithm based on the original data of the complete circular profile and three equally spaced arc profiles in the forward direction, and eliminates the influence of the natural rotation and jitter of the steel pipe on the measurement of straightness when it is transmitted on the roller table, and can accurately realize the dynamic measurement of the straightness of large-diameter welded pipes at any position of 360°; the present invention solves the shortcomings of manual visual and manual wire drawing methods for measuring straightness, saves a lot of manpower, material and financial resources, and improves the efficiency and accuracy of the measurement results. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A flowchart of a method according to an embodiment of the present invention;

[0028] Figure 2 Schematic diagram of the process of eliminating the natural rotation of the welded pipe in an embodiment of the present invention;

[0029] Figure 3 It is a schematic diagram of eliminating the vibration of the welding pipe in an embodiment of the present invention. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] This embodiment describes a method for dynamically measuring the straightness of a large-diameter welded pipe. The welded pipe of this embodiment passes through a full-circle detection unit and multiple equally spaced arc profile detection units in sequence to obtain the full-circle screw hole data and multiple equally spaced arc profile data of the welded pipe at the same time; Figure 1 As shown, the method comprises the following steps:

[0032] Step 1: Weld point confirmation step. The welded pipe is made of a rectangular steel plate rolled into a tube, and the joint is welded solidly. The weld is obvious and higher than the surface of the welded pipe. This step locates the angle position of the weld on the welded pipe based on the complete circle contour data. Specifically, since the cross section of the welded pipe cannot meet the perfect circle standard, firstly, 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 Connection L pl,pr The distance dist. Among them, L pl,pr The general formula of the straight line equation 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 surface of the welded pipe, 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.

[0033] Step 2: Eliminate the error caused by the natural rotation of the welded pipe. Based on the location of the weld in step 1, eliminate the error caused by the natural rotation of the steel pipe when it moves forward.

[0034] Step 2.1: Figure 1As shown in the figure, the steel pipe rotates irregularly clockwise or counterclockwise when it moves forward ( Figure 2 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.

[0035] Step 2.2: According to the value of θ obtained in step 2.1, rotate the contour of the complete circle at time t1 by an angle of θ so that the welds of the complete circles at time t1 and time t2 are at the same angle. Then, perform a nearest neighbor search on the complete 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 complete the arc at time t3, and so on. Finally, the operation is repeated for all complete circles, thereby eliminating the error caused by the natural rotation of the steel pipe when it moves forward.

[0036] Step 3: Eliminate the jitter error of the welded pipe. According to step 2, all the complete circle profile data after eliminating the rotation error are obtained, and the error effect caused by the jitter of the steel pipe when it moves forward is further eliminated.

[0037] 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 3 As shown, assuming that there are complete circular contours c1, c2, c3 at time t1, and complete circular contours c4, c5, 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 3 arcs are required to eliminate jitter, and only equal spacing can ensure the correspondence between c2 and c4, c3 and c5). The transformation matrix between the corresponding circular contours is calculated using the least squares method as m_24, m_35.

[0038] Step 3.2: Perform weighted averaging on the transformation matrices m_24 and m_35 with the weight set to 0.5 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, thereby eliminating the jitter error caused by the steel pipe moving forward.

[0039] Step 4: Straightness calculation step. According to the contour set c_finals obtained in step 3.2, the straightness of any position of the whole tube 360° is calculated. It is known that all contours are obtained by scanning in the XOZ plane. The present invention uses the end point connection method for calculation. For example, to calculate the straightness in the 90° direction, the point a in all contours with an x ​​coordinate of 0 and a z coordinate greater than 0 can be specified. i (i=1,2,...,N), take a1 and a N The line connecting the two points is taken as the reference line L, and then the distances from all the remaining contour points to the reference line 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. Similarly, the straightness of any position of the entire tube 360° can be calculated.

[0040] Based on the original data of the complete circular contour and three equally spaced arc contours 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 table on the measurement of straightness, and 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 for measuring straightness, saves a lot of manpower, material and financial resources, and improves the efficiency and accuracy of the measurement results.

[0041] 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 the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. 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 embodiments of the present invention.

Claims

1. A method for dynamically measuring the straightness of a large-diameter welded pipe, characterized in that: The welded pipe passes through a full circle detection unit and a plurality of equally spaced arc profile detection units in sequence, and obtains complete circular screw hole data and a plurality of equally spaced arc profile data of the welded pipe at the same time; the method comprises the following steps: Steps for 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 to obtain the contour point with the maximum value of max_dist among all distances, which is the weld point; Steps to eliminate the error caused by natural rotation of the welded pipe: according to 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, and then the complete circle at time t1 and the arc at time t2 are searched for the nearest neighbor, and the optimal transformation matrix from the source point cloud to the target point cloud is solved based on the nearest neighbor point cloud found, 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; finally, the operation is repeated for all complete circles, thereby eliminating the error caused by the natural rotation of the welded pipe when it moves forward; Steps for eliminating the jitter error of the welded pipe: Assume that the complete circle contour data obtained based on the steps of eliminating the error caused by the natural rotation of the welded pipe at two different times t1 and t2 are: complete circle contours c1, c2, c3 at time t1, complete circle contours c4, c5, c6 at time t2, where c2 and c4 are at the same position of the welded pipe, c3 and c5 are also at the same position of the welded pipe, and the transformation matrices between the corresponding circle contours are calculated to be m_24 and m_35, and 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, the operation is repeated for all the replaced complete circles to obtain a contour set c_finals; Steps for calculating straightness: Calculate the straightness of the welded pipe at any position within 360° according to the contour set c_finals.

2. The method for dynamically measuring the straightness of a large-diameter welded pipe 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 contour point p(x i ,z i ) on the circle; then, take the contour point p and two points p with an interval of 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 Connection L pl,pr The distance dist; where L pl,pr The general formula of the straight line equation 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.

3. The method for dynamically measuring the straightness of a large-diameter welded pipe 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 formula for solving 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.

4. The method for dynamically measuring the straightness of a large-diameter welded pipe according to any one of claims 1 to 3, characterized in that: The calculation process of the straightness calculation step is as follows: All contours are obtained by scanning in the XOZ plane, and the end point connection method is used for calculation, and a1 and a N The line connecting the two points is taken as the reference line L, and then the distances from all the remaining contour points to the reference line 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.

5. A system for dynamically measuring the straightness of large-diameter welded pipes, characterized in that: include: Detection module: including a full circle detection unit and multiple equally spaced arc profile detection units that the welded pipe passes through in sequence, to obtain the complete circle screw hole data and multiple equally spaced arc profile data of the welded pipe at the same time; Weld point confirmation module: fit an ellipse according to 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 to obtain the contour point with the maximum value of max_dist among all distances, which is the weld point; Module for eliminating the error caused by natural rotation of welded pipe: according to 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, and then the complete circle at time t1 and the arc at time t2 are searched for the nearest neighbor, and the optimal transformation matrix from the source point cloud to the target point cloud is solved based on the nearest neighbor point cloud found, 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; finally, the operation is repeated for all complete circles, thereby eliminating the error caused by the natural rotation of the welded pipe when it moves forward; Eliminating welding pipe jitter error module: Assume that the complete circle contour data obtained based on the steps of eliminating the error caused by natural rotation of the welding pipe at two different times t1 and t2 are: complete circle contours c1, c2, c3 at time t1, complete circle contours c4, c5, c6 at time t2, where c2 and c4 are at the same position of the welding pipe, c3 and c5 are also at the same position of the welding pipe, and the transformation matrices between the corresponding circle contours are calculated to be 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, the operation is repeated for all the replaced complete circles to obtain a contour set c_finals. Straightness calculation module: Calculate the straightness of the welded pipe at any position of 360° based on the contour set c_finals.

6. The system for dynamically measuring the straightness of large-diameter welded pipes according to claim 5, characterized in that: The specific calculation process of the weld point confirmation module 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 an interval of 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 Connection L pl,pr The distance dist; where L pl,pr The general formula of the straight line equation 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.

7. The system for dynamically measuring the straightness of a large-diameter welded pipe according to claim 5, characterized in that: In the module for eliminating the error caused by natural rotation of the welded pipe, the optimal transformation matrix formula for solving 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.

8. The system for dynamically measuring the straightness of a large-diameter welded pipe according to any one of claims 5 to 7, characterized in that: The calculation process of the straightness calculation module is as follows: All contours are obtained by scanning in the XOZ plane, and the end point connection method is used for calculation. N The line connecting the two points is taken as the reference line L, and then the distances from all the remaining contour points to the reference line 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.

9. A processing device, characterized in that: It comprises at least one processor and at least one memory in communication with the processor, wherein the memory stores program instructions executable by the processor, and the processor calls the program instructions to execute any method according to claims 1 to 4.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer instructions, and the computer instructions enable the computer to execute the method according to any one of claims 1 to 4.

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