Three-dimensional numerical control pipe bending machine and control method thereof

Abstract

The invention relates to the technical field of metal processing, in particular to a three-dimensional numerical control pipe bending machine and a control method thereof. The method comprises the steps of firstly determining initial stress of a pipe based on pipe parameters and pipe materials; determining the residual stress of the previous section of pipe to the bending of the current section of pipe; the initial stress and the residual stress are combined to obtain the total stress borne by the pipe; when the total stress exceeds a normal stress range, the pipe is judged to be a pipe possibly having cracks; determining the elliptical long-axis direction angle of the section of the pipe with possible cracks; calculating the maximum tensile stress direction value based on the long axis direction angle of the ellipse and the bending radius deviation; obtaining an actual trend value of the crack; judging the similarity between the maximum tensile stress direction value and the actual trend value; and when the similarity exceeds the normal level, the production parameters of the pipe bending machine are adjusted. Real-time monitoring of the pipe quality in the bending process is achieved, and the real-time performance of production parameter adjustment of the pipe bending machine is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of metal processing, and in particular to a three-dimensional CNC pipe bending machine and a control method thereof. Background Art

[0002] Three-dimensional CNC pipe bending machines are core equipment in the modern pipe processing field. Leveraging advanced multi-axis CNC systems and high-precision molds, they can precisely bend metal or non-metallic pipes into shape within three dimensions according to design requirements. From automotive engine piping and complex aerospace pipe fittings to special-shaped pipes for architectural decoration, three-dimensional CNC pipe bending machines can efficiently complete complex multi-angle processing tasks. The advent of this equipment has not only significantly improved the precision and efficiency of pipe processing, but also effectively reduced the scrap rate of pipes through automated control. This type of pipe bending machine is currently widely used in industries such as high-end manufacturing and energy equipment, becoming a key force in promoting the intelligent upgrade of pipe processing technology.

[0003] The quality inspection process of traditional 3D CNC tube bending machines usually sets the inspection step after all bending operations are completed. This delayed inspection method may affect actual production efficiency because once quality problems are discovered in the finished product, the processing time and material costs invested in the early stage will be wasted.

[0004] Currently, the most common way to control 3D CNC tube bending machines is to directly inspect tube quality through machine vision and adjust production parameters when tube quality is poor. However, some tube quality issues are not caused by improper 3D CNC tube bending machine production parameters, and these cannot be used as a basis for production parameter adjustments. Therefore, directly adjusting production parameters when tube quality is poor is less accurate. Summary of the Invention

[0005] In order to solve the technical problem of low accuracy in adjusting production parameters directly when the pipe quality is poor, the purpose of the present invention is to provide a three-dimensional CNC pipe bending machine and a control method thereof. The technical solutions adopted are as follows: In a first aspect, an embodiment of the present invention provides a control method for a three-dimensional CNC pipe bender, the method comprising: Get the pipe parameters of the pipe bending machine; Determining the initial stress of the pipe based on the pipe parameters and pipe material; determining the residual stress of the previous pipe section on the bending of the current pipe section based on the distance between the bending centers of the previous and next pipe sections, the effective influence distance, and the initial stress of the previous pipe section; combining the initial stress and the residual stress to obtain the total stress to which the pipe is subjected; and determining that the pipe may have cracks when the total stress exceeds a normal stress range; For pipes that may have cracks, the ellipse major axis orientation angle is determined based on the ellipse major axis orientation angle of the previous pipe, the pipe's rotation angle, and the azimuth offset. The azimuth offset is used to characterize the degree of influence of the bending curvature on the ellipse major axis orientation angle. The maximum tensile stress direction value is calculated based on the deviation between the ellipse major axis orientation angle and the bending radius. By calibrating the camera's viewing angle error and controlling the pipe's rotation angle in real time, the actual direction of the crack is obtained; the similarity between the maximum tensile stress direction value and the actual direction value is determined; and when the similarity exceeds a normal level, the production parameters of the pipe bending machine are adjusted.

[0006] Furthermore, the determining of the initial stress of the pipe based on the pipe parameters and the pipe material includes: determining the ovality of the pipe cross section based on the pipe parameters; The initial stress of the current section of the pipe is determined by combining the ovality and the yield strength of the pipe material.

[0007] Furthermore, the determining of the ovality of the pipe cross section based on the pipe parameters includes: The pipe parameters include: bending angle, bending radius and pipe diameter of the pipe cross section; Determine the bending parameters based on the bending radius and diameter of the pipe; The ellipticity of the cross section of the tube is determined by combining the linear term with the quadratic term in combination with the bending parameters and the bending angle of the tube.

[0008] Furthermore, the determining of the initial stress of the current section of the pipe by combining the ovality and the yield strength of the pipe material includes: The product of the ovality and the yield strength of the current pipe section is used as the initial stress of the current pipe section.

[0009] Furthermore, the method of determining the residual stress of the preceding pipe section on the bending of the current pipe section based on the distance between the bending centers of the preceding and following pipe sections, the effective influence distance, and the initial stress of the preceding pipe section includes: The initial stress of the previous section of pipe is corrected by the distance between the bending centers of the current and previous sections of pipe and the effective influence distance, resulting in the residual stress of the previous section of pipe on the bending of the current section. The distance between the bending centers of the front and rear ends of the pipe is negatively correlated with the residual stress, while the effective influence distance is positively correlated with the residual stress. The effective impact distance is determined by comparing the bending radius and thickness of the previous pipe.

[0010] Furthermore, the determining of the major axis direction angle of the ellipse according to the major axis direction angle of the ellipse of the previous section of the tube, the rotation angle of the tube, and the azimuth offset includes: The pipe parameters include: bending radius and pipe outer diameter; The angular offset is determined based on the bending radius and the outer diameter of the pipe, wherein the bending radius and the angular offset are negatively correlated, and the outer diameter of the pipe and the angular offset are positively correlated. The angular offset is a standardized value. The sum of the ellipse major axis direction angle of the previous section of the pipe, the pipe rotation angle, and the azimuth offset is used as the ellipse major axis direction angle of the current section; wherein the ellipse major axis direction angle is an angle value.

[0011] Furthermore, the calculation of the maximum tensile stress direction value based on the ellipse major axis direction angle and the bending radius deviation includes: The difference between the direction angle of the major axis of the ellipse and the right angle is determined as the conversion direction value; Determine the stress deviation angle caused by the bending direction based on the bending radius; The sum of the conversion direction value and the stress offset angle is calculated as the maximum tensile stress direction value.

[0012] Furthermore, the actual direction value of the crack is obtained by calibrating the camera viewing angle error and controlling the rotation angle of the pipe in real time, including: Obtain a tube production image of a tube bending machine and determine the angle value of the crack direction in the tube production image; The angle deviation coefficient is determined by the vertical distance between the camera optical axis and the center axis of the pipe and the horizontal projection distance from the camera lens to the center axis of the pipe; Combined with the rotation angle and the angle deviation coefficient of the pipe, the angle value of the crack direction in the pipe production image is corrected to obtain the actual direction value of the crack.

[0013] Furthermore, the determining of the similarity between the maximum tensile stress direction value and the actual direction value includes: The difference between the maximum tensile stress direction value and the actual direction value is calculated, and negative correlation mapping is performed on the difference to obtain the similarity.

[0014] In a second aspect, a three-dimensional CNC pipe bender is provided, comprising a processor and a memory, wherein the processor is configured to process instructions stored in the memory to implement a monitoring process of the following modules, wherein the memory stores executable code: Data acquisition module, used to obtain pipe parameters of the pipe bending machine; The first analysis module is configured to determine the initial stress of the pipe based on the pipe parameters and the pipe material; determine the residual stress of the previous pipe section on the bending of the current pipe section based on the distance between the bending centers of the previous and next pipe sections, the effective influence distance, and the initial stress of the previous pipe section; and calculate the total stress to which the pipe is subjected by combining the initial stress and the residual stress; and determine that the pipe is likely to have cracks when the total stress exceeds a normal stress range; The second analysis module is used to determine the major axis orientation angle of the ellipse for pipes that may have cracks based on the major axis orientation angle of the ellipse in the previous section of the pipe, the pipe's rotation angle, and the azimuth offset. The azimuth offset is used to characterize the degree to which the bending curvature affects the major axis orientation angle of the ellipse. The maximum tensile stress direction value is calculated based on the deviation between the major axis orientation angle of the ellipse and the bending radius. The parameter adjustment module is used to obtain the actual direction value of the crack through camera viewing angle error calibration and real-time control of the rotation angle of the pipe; determine the similarity between the maximum tensile stress direction value and the actual direction value; and adjust the production parameters of the pipe bending machine when the similarity exceeds a normal level.

[0015] In a third aspect, an embodiment of the present invention provides a computer program product, which includes: computer program code, which, when running on a computer, enables the computer to execute the method in the above-mentioned first aspect or any possible implementation of the first aspect.

[0016] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed in a computer, the computer is caused to execute various possible implementations of the first aspect.

[0017] The embodiments of the present invention have at least the following beneficial effects: The present invention first determines the initial stress of the pipe based on the inherent characteristics of the pipe. Since the continuous bending of the pipe will produce a cumulative effect of deformation and stress during the actual operation of the pipe bending machine, it directly leads to the risk of cracking in the subsequent pipe sections to be bent. In the pipe bending production factory, the process of each pipe bending machine has the characteristics of advancing the bending step by step. Each time a section of pipe is bent, it is pushed forward, and the deformation generated during the bending process of the previous section will affect the next section. In order to accurately locate the pipe area where cracks may occur, it is necessary to start from the essence of the pipe bending process, determine the residual stress of the previous section of pipe to the bending of the current pipe, combine the participating stress and the initial stress, and obtain the total stress to which the pipe is subjected, and then determine whether the pipe is a pipe that may have cracks. The pipe that may have cracks is most likely a pipe with quality problems caused by the pipe bending operation. Subsequently, only pipes that may have cracks will be inspected and analyzed, which can timely detect cracks in the pipes and reduce time waste. Furthermore, for pipes that may have cracks, the maximum tensile stress direction value is determined, and the actual direction value of the crack is compared with the maximum tensile stress direction value. The production parameters of the pipe bending machine can be adjusted based on the similarity between the two. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions and advantages of the embodiments of the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 A flow chart of a method for controlling a three-dimensional CNC pipe bender provided by one embodiment of the present invention; Figure 2 A schematic diagram of a module of a three-dimensional CNC pipe bending machine provided by one embodiment of the present invention. DETAILED DESCRIPTION

[0020] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the following, in combination with the accompanying drawings and preferred embodiments, describes in detail a three-dimensional CNC pipe bending machine and its control method proposed in accordance with the present invention, its specific implementation method, structure, characteristics and effects.

[0021] In the following description, different references to "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, the particular features, structures, or characteristics of one or more embodiments may be combined in any suitable manner.

[0022] In the description of the embodiments of the present invention, unless otherwise specified, " / " means or, for example, A / B can mean A or B: "and / or" in the text is only a description of the association relationship of associated objects, indicating that there can be three relationships, for example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, in the description of the embodiments of the present invention, "multiple" refers to two or more than two.

[0023] In the following, the terms "first" and "second" are used for descriptive purposes only and should not be understood to imply or suggest relative importance or implicitly indicate the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features.

[0024] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0025] The embodiments of the present invention are described below with reference to the accompanying drawings. Those skilled in the art will appreciate that, with the development of technology and the emergence of new scenarios, the technical solutions provided by the embodiments of the present invention are also applicable to similar technical problems.

[0026] The embodiment of the present invention provides a specific implementation method of a three-dimensional CNC pipe bending machine and its control method. The method is suitable for a scenario in which the quality of the pipe in the bending operation of the pipe bending machine is monitored in real time based on image processing technology. In this scenario, the bending operation of the pipe bending machine is carried out simultaneously with the monitoring step, and the bending part in the pipe is detected, so that cracks in the pipe can be found in time, reducing time waste. In a pipe bending production factory, the process of each pipe bending machine has the characteristic of advancing the bending step by step. Each time a section of pipe is bent, it is pushed forward, and the deformation generated during the bending process of the previous section will affect the next section. Based on this characteristic, the pipe is identified as a pipe that may have cracks; if cracks appear in the area, the production parameters of the pipe bending machine are adjusted by analyzing the characteristics of the cracks.

[0027] The specific scheme of a three-dimensional CNC pipe bending machine and a control method thereof provided by the present invention is described in detail below with reference to the accompanying drawings.

[0028] See also Figure 1 , which shows a flowchart of a control method for a three-dimensional CNC pipe bender provided by one embodiment of the present invention, the method comprising the following steps: Step S100, obtaining the pipe parameters of the pipe bending machine.

[0029] In the production process of 3D CNC pipe bending machines, improving production efficiency is a key goal in optimizing the manufacturing process. However, traditional inspection methods often focus quality verification on the finished product stage. If cracks appear in the pipe during the second bending process, all subsequent processing steps will become ineffective, resulting in a waste of time and materials. To overcome this efficiency bottleneck, the inspection process must have real-time response capabilities, that is, trigger an immediate warning when a crack defect occurs. Based on this, combined with the process characteristics of the pipe bending machine's segmented bending process, the state of the pipe during each bending process can be finely analyzed to ensure that the defect is judged at the initiation stage.

[0030] To achieve efficient, real-time monitoring of the 3D CNC tube bender, a high-frame camera is installed directly above the bending area and in front of the conveyor belt. Its field of view is focused on the core operating area of ​​the bender head to capture images of the tube production. When the bender begins the bending process, the high-frame camera switches to high-speed shooting mode, rapidly capturing key details of the tube bending process at a high frame rate. During the intervals between tubes being pushed forward after a single bending operation, the camera automatically reduces the frame rate, minimizing data redundancy and equipment energy consumption. This ensures optimal resource utilization and maximizes monitoring efficiency while ensuring monitoring accuracy.

[0031] First, the pipe parameters of the pipe bending machine are obtained through the pipe production image. The pipe parameters include: the bending angle θ of the pipe, the bending radius R, and the pipe diameter D of the pipe cross section.

[0032] The bending angle can be used to characterize the degree of pipe deformation, and the ratio of the bending radius to the pipe diameter R / D can be used to reflect the intensity of the bending.

[0033] Step S200: Determine the initial stress of the pipe based on the pipe parameters and the pipe material; determine the residual stress of the previous pipe section on the bending of the current pipe section based on the distance between the bending centers of the previous and next pipe sections, the effective influence distance, and the initial stress of the previous pipe section; and calculate the total stress to which the pipe is subjected by combining the initial stress and the residual stress. When the total stress exceeds the normal stress range, the pipe is determined to be a pipe that may have cracks.

[0034] During the actual operation of a pipe bender, the continuous bending of the pipe will produce a cumulative effect of deformation and stress, directly leading to the risk of cracking in the subsequent pipe section to be bent. In order to accurately locate the pipe area where cracks may occur, it is necessary to proceed from the essence of the pipe bending process and circle the area where cracks may occur according to the preset parameters of the pipe bender: the degree of bending of the previous section of the pipe directly determines the degree of elliptical deformation of the pipe. The stronger the degree of bending, the higher the elliptical degree, and the stronger the stress concentration effect at the endpoint of the long axis, which in turn increases the possibility of cracking when the pipe is bent in the subsequent section. The distance between the subsequent section and the center of the previous section affects the superposition range of the stress field. If the spacing is too small, the previous residual stress will be superimposed on the current bending stress.

[0035] During pipe bending, the degree of bend in the first section is a key factor affecting the likelihood of cracks in the next section. Due to the positive correlation between bending deformation and stress concentration, the greater the degree of bend, the more pronounced the ovalization of the pipe cross-section, and the more severe the material deformation at the endpoints of the oval's major axis. This leads to increased stress concentration and a corresponding increase in internal residual stress, making cracks more likely to form in the next section of the bend due to the inability to withstand the new stress.

[0036] The ovality of the pipe section is determined in combination with the pipe parameters. Specifically, first, the bending parameter is determined based on the bending radius and the pipe diameter of the pipe. The bending parameter is the ratio of the pipe diameter to the bending radius of the pipe section. The ellipticity of the cross section of the tube is determined by combining the linear term with the quadratic term in combination with the bending parameters and the bending angle of the tube.

[0037] In some embodiments, the ovality of the tube cross section The calculation formula is: ;in, is the first fitting coefficient; is the second fitting coefficient; θ is the bending angle of the pipe; R is the bending radius; and D is the pipe diameter of the pipe cross section. In the embodiment of the present invention, the first fitting coefficient is 0.03, and the second fitting coefficient is 0.03. The implementer can adjust these two values ​​according to actual conditions.

[0038] in, Indicates that the curvature parameter Convert to the inverse of the dimensionless relative bending radius to facilitate unified calculation of different pipe diameters. The stage where the dominant deformation is small reflects the linear superposition effect of bending curvature and deformation; the quadratic term The dominant deformation stage characterizes the acceleration of nonlinear deformation. By superimposing linear and quadratic terms, when R / D or θ is small, the linear term dominates, and the ellipticity increases approximately linearly with θ. When R / D or θ is large, the quadratic term dominates, and the ellipticity increases rapidly and nonlinearly with θ. It should be noted that when the pipe cross-section is an ellipse, the major axis of the pipe cross-section is used as the pipe diameter.

[0039] During the operation of the pipe bending machine, the first bend will form a residual stress field inside the pipe, causing the pipe to ellipse. When the second bend is adjacent to the previous one, the residual stress that has not yet dissipated will be superimposed on the newly generated bending stress, causing the local stress to increase significantly. This will not only aggravate the degree of distortion of the pipe cross section, but also make the material very prone to cracks at the new bend.

[0040] Ovality is used to calculate the baseline stress of the subsequent section. This stress is the stress generated independently of the previous section during bending. During the bending process, the pipe cross-section deforms into an ellipse due to bending. The initial stress calculated based on the ovality is specifically calculated by multiplying the ovality by the yield strength of the current section of pipe. The higher the yield strength, the higher the stress generated for the same deformation.

[0041] In some embodiments, the initial stress The calculation formula is: ;in, is an empirical coefficient used to adjust the quantitative relationship between ovality and residual stress; is the ovality of the pipe section in the current segment; is the yield strength of the current pipe section.

[0042] Based on the stress effect of the previous section on the current section and the stress of the previous section itself when bending, the residual stress of the previous section on the bending of the current section is determined according to the distance between the bending centers of the front and rear sections of the pipe, the effective influence distance, and the initial stress of the previous section of the pipe. Specifically, the initial stress of the previous section of the pipe is corrected by the distance between the bending centers of the current section and the previous section of the pipe and the effective influence distance to obtain the residual stress of the previous section of the pipe on the bending of the current section of the pipe. Among them, the distance between the bending centers of the front and rear ends of the pipe is negatively correlated with the residual stress, and the effective influence distance is positively correlated with the residual stress. Among them, the effective influence distance is determined by comparing the bending radius and the thickness of the previous section of the pipe. Specifically, three times the bending radius and five times the pipe thickness are numerically compared, and the larger of the two values ​​is determined as the effective influence distance.

[0043] In some embodiments, the residual stress The calculation formula is: ;in, is the initial stress of the previous section of pipe; is the stress superposition coefficient; e is a natural constant; L is the distance between the bending center of the current section and the previous section of the pipe; It is the effective influence distance of the previous pipe section bending on the current pipe section.

[0044] The stress superposition coefficient is used to reflect the correction of material properties and process conditions on stress transfer efficiency. The better the material plasticity, the larger the stress superposition coefficient and the more significant the stress transfer. The greater the mold friction in the bending process, the smaller the stress superposition coefficient.

[0045] When the distance between the bending center of the current section and the previous section of the pipe increases, That is, as the distance between the front and rear sections increases, the influence of the residual stress of the previous section on the current section becomes smaller and smaller.

[0046] Combine the initial stress and the residual stress to obtain the total stress of the pipe. Specifically, the sum of the initial stress and the residual stress is used as the total stress of the pipe. In some embodiments, the total stress of the pipe in the current section is The calculation formula is: ;in, is the initial stress of the current segment itself; It is the residual stress of the previous section bending the current section of pipe.

[0047] Based on the total stress to which the pipe is subjected, the area that may exceed the strength of the pipe is determined. When the total stress exceeds the normal stress range, the pipe is determined to be a pipe that may have cracks. The upper limit of the normal stress range is obtained by the ratio of the yield strength ω of the pipe material to the safety factor n, wherein the lower limit of the normal stress range is 0. Therefore, the normal stress range is 0~ω / n. In the embodiment of the present invention, when the pipe is an automobile part, the safety factor has a value range of 2.5~4, and when the pipe is an aircraft engine part, the safety factor has a value range of 5~8. When the total stress exceeds the normal stress range, it is determined that the stress to which the pipe is subjected exceeds the limit that the pipe itself can withstand, and the pipe may have cracks, and the corresponding pipe is determined to be a pipe that may have cracks.

[0048] Identify pipes that may have cracks in advance. Once cracks appear, the inspection scope can be quickly narrowed based on the risk areas defined in advance. Combined with the characteristics of the cracks, the root causes of the cracks can be traced more accurately. From the perspective of cost control, accurately locating risk areas avoids the waste of resources for full-area monitoring, reduces detection costs, and shortens fault location and repair time.

[0049] Step S300: For pipes that may have cracks, determine the major axis direction angle of the ellipse based on the major axis direction angle of the previous section of the pipe, the pipe's rotation angle, and the azimuth offset. The azimuth offset is used to characterize the degree of influence of the bending curvature on the major axis direction angle of the ellipse. Calculate the maximum tensile stress direction value based on the deviation between the major axis direction angle of the ellipse and the bending radius.

[0050] Pipes that may have cracks are monitored closely. Once a real crack defect appears in an area, an analysis is carried out based on the specific characteristics of the crack: first, the direction of the maximum tensile stress is accurately calculated based on the azimuth angle of the ellipse major axis and the deviation of the bending radius; then, the actual direction of the crack is obtained through real-time control of the camera viewing angle error and the rotation angle of the pipe; finally, based on the direction of the maximum tensile stress and the actual direction of the crack, a control strategy is formed with production line parameters such as rotation angle and bending radius as the core.

[0051] During actual pipe bending, the bending machine determines whether to rotate the pipe during each operation based on product requirements. Pipe rotation directly influences the orientation of cracks. Changes in the rotation angle deflect the major axis of the elliptical cross-section of the pipe, resulting in a simultaneous shift in the direction of maximum tensile stress. Therefore, this critical factor must be taken into consideration when determining crack orientation.

[0052] Calculate the actual azimuth angle of the major axis of the ellipse of the current bending section to provide a basis for determining the direction of the maximum tensile stress. Because the cross-section of the tube changes from a circle to an ellipse during the bending process, the azimuth angle of the major axis of the ellipse directly affects the direction of the maximum tensile stress. In addition, considering that the bending curvature will cause additional offset of the major axis of the ellipse, it is necessary to correct the major axis direction angle of the ellipse of the current section in combination with the major axis direction angle of the ellipse of the previous section of the tube. In an embodiment of the present invention, the method for obtaining the major axis direction angle of the ellipse of the previous section of the tube is as follows: first obtain the image corresponding to the cross-section of the tube, which is an ellipse, and obtain the angle value between the major axis of the ellipse and the horizontal line to the right as the major axis direction angle of the ellipse of the tube. It should be noted that the major axis direction angle of the ellipse is an angle value.

[0053] The sum of the ellipse's major axis orientation angle, the tube's rotation angle, and the azimuth offset for the previous segment is used as the ellipse's major axis orientation angle for the current segment. The azimuth offset is determined based on the bend radius and the tube's outer diameter. The bend radius and the orientation offset are negatively correlated, while the tube's outer diameter and the orientation offset are positively correlated. The orientation offset is a normalized value. The orientation offset indicates the degree to which the bend curvature affects the ellipse's major axis orientation angle.

[0054] The rotation angle of the pipe is defined as the angle less than 180° formed by the pipe as the pipe direction angle, and the acute angle formed by the center line of the pipe direction angle and the horizontal line pointing to the right as the pipe rotation angle.

[0055] In some embodiments, the angular offset The calculation formula is: ;in, is a preset offset empirical value, which is 0.1~0.3 in the embodiment of the present invention. In other embodiments, the implementer can adjust the value according to actual conditions. The preset offset empirical value is used to reflect the influence of the bending curvature on the azimuth of the major axis of the ellipse; D is the pipe diameter; R is the bending radius.

[0056] The maximum tensile stress direction value is calculated based on the deviation between the major axis direction angle of the ellipse and the bending radius.

[0057] The difference between the direction angle of the major axis of the ellipse and the right angle is determined as the conversion direction value; the stress offset angle caused by the bending direction is determined according to the bending radius; when the bending direction is outward bending, the sum of the conversion direction value and the stress offset angle is calculated as the maximum tensile stress direction value; when the bending direction is inward bending, the difference between the conversion direction value and the stress offset angle is calculated as the maximum tensile stress direction value.

[0058] In some embodiments, the maximum tensile stress direction value The calculation formula is: ;in, is the major axis direction angle of the ellipse of the current segment; is the conversion direction value; is the stress deviation angle.

[0059] The stress deviation angle The calculation formula is: ;in, The greater the difference between the bending radius and three times the outer diameter of the pipe, the greater the deviation. The more there is, the more significant the stress offset will be.

[0060] Step S400: obtain the actual direction value of the crack through camera viewing angle error calibration and real-time control of the pipe rotation angle; determine the similarity between the maximum tensile stress direction value and the actual direction value; and adjust the production parameters of the pipe bending machine when the similarity exceeds a normal level.

[0061] A production image of a pipe produced by a pipe bending machine, captured by a camera. For this pipe production image, crack pixels are obtained and a straight line is fitted to the crack pixels. The angle between the fitted line and a horizontal line pointing to the right is used as the angle of the crack direction in the pipe production image. It should be noted that edge pixels in the pipe production image can be determined using the Canny or Sobel algorithms, with edge pixels other than the pipe edge being considered crack pixels.

[0062] Determine the angle of the crack orientation in the pipe production image and calibrate it to the actual orientation angle relative to the pipe's initial axis. Because pipe rotation and camera viewing angle can cause deviations between the apparent crack orientation and the actual crack orientation, the actual crack orientation is determined by calibrating the camera viewing angle error and controlling the pipe's rotation angle in real time.

[0063] Specifically, the angle value of the crack direction in the pipe production image is corrected based on the pipe's rotation angle and angle deviation coefficient to obtain the actual direction value of the crack.

[0064] In some embodiments, the actual direction of the crack The calculation formula is: ;in, is the angle value of the crack direction; is the rotation angle of the pipe; is the angle deviation coefficient caused by the camera viewing angle.

[0065] The angular deviation coefficient is obtained by the vertical distance between the camera optical axis and the central axis of the pipe and the horizontal projection distance from the camera lens to the central axis of the pipe.

[0066] Angle deviation coefficient The calculation formula is: ; Where h is the vertical distance between the camera optical axis and the center axis of the pipe; L is the horizontal projection distance from the camera lens to the center axis of the pipe; arctan is the inverse tangent function.

[0067] This angular deviation coefficient is constructed based on the camera perspective projection model. When the camera is looking directly at the pipe, that is, when the vertical distance h between the camera optical axis and the center axis of the pipe is 0, the camera's line of sight is perpendicular to the radial section of the pipe. At this time, the projection angle of the crack in the pipe production image on the plane presented by the image is consistent with the actual angle, without deviation. However, when the vertical distance between the camera optical axis and the center axis of the pipe changes, that is, when the camera is offset, the camera is not looking directly at the pipe. At this time, the line of sight is tilted, and the imaging of the radial section where the crack is located on the surface of the photosensitive element will change. The direction that was originally perpendicular to the line of sight will deviate from the projection angle on the surface of the photosensitive element under tilted observation, and the degree of angular deviation is determined by the tilted viewing angle. The geometric derivation of the radial distortion model essentially relies on polar coordinate transformation. In the ideal camera perspective projection model, pixel coordinates (x, y) correspond to polar coordinates (r, θ); where, , , is the polar angle, r is the polar diameter, the polar angle represents the angle between a point on the plane and the polar axis, and the polar diameter represents the distance from the point to the pole (origin); the theoretical basis of the angle deviation coefficient in the embodiment of the present invention is In the embodiment of the present invention, the polar axis is the positive direction of the x-axis.

[0068] By using the pipe rotation angle meter and angle deviation coefficient, it is possible to correct the angle deviation of the crack direction caused by visual inspection.

[0069] Furthermore, the similarity between the maximum tensile stress direction value and the actual direction value is determined, and when the similarity exceeds a normal level, the pipe parameters are adjusted.

[0070] Specifically, the difference between the maximum tensile stress direction value and the actual direction value is calculated, and negative correlation mapping is performed on the difference to obtain the similarity.

[0071] In some embodiments, the similarity The calculation formula is: ;in, is the actual direction of the crack; is the maximum tensile stress direction value.

[0072] In the calculation formula of similarity, Characterizes the absolute deviation between the actual crack direction and the stress direction, reflecting the "degree of consistency" between the two. The smaller the difference, the closer the crack direction is to the stress direction, and the more likely it is that the crack is caused by stress. The "theoretical maximum deviation benchmark" represents the stress-dominated crack. The maximum tensile stress direction is theoretically perpendicular to the major axis of the ellipse (i.e., the angle is 90°). The absolute deviation is converted into "similarity γ" through "1-", so that the value range of γ is directly related to the physical meaning: when When γ=0, it means that the two directions are completely perpendicular and the stress has no effect on the crack direction; when When γ→1, the two directions are highly consistent, indicating stress-dominated cracking. If the γ of a batch of pipes is generally high, such as γ>0.5 accounting for more than 70%, it can be adjusted according to actual conditions. This indicates that the proportion of stress-dominated cracks is high, and production parameters need to be adjusted to reduce stress concentration. The production parameters of the pipe bending machine include: the pipe rotation angle and bending radius.

[0073] If a batch of pipes undergoes testing and shows a high proportion of similarity γ values, this indicates a significant proportion of stress-dominated cracks within that batch. Systematic control of the pipe bending machine's production parameters is necessary to achieve a closed-loop control process, from passive crack detection to active adjustment of production parameters. Prioritize increasing the pipe's rotation angle appropriately to change the azimuth of the subsequent pipe's elliptical major axis, thereby adjusting the direction of maximum tensile stress. Simultaneously, increase the bending radius appropriately to alleviate stress concentration caused by excessive bending. After the adjustment, conduct a small trial run on the next batch of pipes, comparing and analyzing the distribution of similarity γ values ​​before and after the adjustment. If the proportion of high similarity γ values ​​decreases by 5%, the parameter adjustment is effective and can be extended to the entire batch. Otherwise, further coordinated optimization of the rotation angle and bending radius is performed until the proportion of stress-dominated cracks is within the expected range. It should be noted that a fixed increment of 5° can be used to increase the pipe's rotation angle and bending radius. In other embodiments, the preset fixed increment angle can be adjusted to meet different adjustment accuracy requirements.

[0074] See also Figure 2 , Figure 2 A schematic diagram of a module of a three-dimensional CNC pipe bender is provided for an embodiment of the present invention, including a processor and a memory. The processor is configured to process instructions stored in the memory to implement the monitoring process of the following modules. The memory stores executable code: Data acquisition module, used to obtain pipe parameters of the pipe bending machine; The first analysis module is configured to determine the initial stress of the pipe based on the pipe parameters and the pipe material; determine the residual stress of the previous pipe section on the bending of the current pipe section based on the distance between the bending centers of the previous and next pipe sections, the effective influence distance, and the initial stress of the previous pipe section; and calculate the total stress to which the pipe is subjected by combining the initial stress and the residual stress; and determine that the pipe is likely to have cracks when the total stress exceeds a normal stress range; The second analysis module is used to determine the major axis orientation angle of the ellipse for pipes that may have cracks based on the major axis orientation angle of the ellipse in the previous section of the pipe, the pipe's rotation angle, and the azimuth offset. The azimuth offset is used to characterize the degree to which the bending curvature affects the major axis orientation angle of the ellipse. The maximum tensile stress direction value is calculated based on the deviation between the major axis orientation angle of the ellipse and the bending radius. The parameter adjustment module is used to obtain the actual direction value of the crack through camera viewing angle error calibration and real-time control of the rotation angle of the pipe; determine the similarity between the maximum tensile stress direction value and the actual direction value; and adjust the production parameters of the pipe bending machine when the similarity exceeds a normal level.

[0075] Optionally, the transmission medium may be a wired link, such as but not limited to coaxial cable, optical fiber, and digital subscriber line, or a wireless link, such as but not limited to Wireless Fidelity (WIFI), Bluetooth, and mobile device network.

[0076] It should be noted that the device provided in the above embodiment is only illustrated by the division of the above functional modules. In actual applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the computer device can be divided into different functional modules to complete all or part of the functions described above.

[0077] In addition, an embodiment of the present invention also protects a device, which may include a memory and a processor, wherein the memory stores executable program code, and the processor is used to call and execute the executable program code to execute a control method for a three-dimensional CNC pipe bending machine provided by an embodiment of the present invention.

[0078] In embodiments of the present invention, the device may be divided into functional modules based on the above-described method examples. For example, these modules may correspond to individual functional modules, or two or more functions may be integrated into a single processing module. The integrated modules may be implemented in hardware. It should be noted that the module division in this embodiment is illustrative and represents only a logical functional division. In actual implementation, other division methods may be employed.

[0079] In the case of dividing each module into modules corresponding to each function, the device may further include a signal uploading module, a determination module, an adjustment module, etc. It should be noted that all relevant contents of each step involved in the above method embodiment can be referred to the functional description of the corresponding functional module and will not be repeated here.

[0080] It should be understood that the device provided in the embodiment of the present invention is used to execute the above-mentioned control method of a three-dimensional CNC pipe bender, and thus can achieve the same effect as the above-mentioned implementation method.

[0081] When an integrated unit is employed, the device may include a processing module and a storage module. When the device is applied to a device, the processing module can be used to control and manage the device's operations. The storage module can be used to support the device in executing program code, etc. The processing module can be a processor or controller that can implement or execute the various exemplary logic blocks, modules, and circuits described in conjunction with the present disclosure. The processor can also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of a digital signal processor (DSP) and a microprocessor, etc. The storage module can be a memory.

[0082] In addition, the device provided in an embodiment of the present invention may specifically be a chip, component or module, and the chip may include a connected processor and memory; wherein the memory is used to store instructions, and when the processor calls and executes the instructions, the chip can execute a control method for a three-dimensional CNC pipe bending machine provided in the above embodiment.

[0083] An embodiment of the present invention also provides a computer-readable storage medium, which stores computer program code. When the computer program code runs on a computer, the computer executes the above-mentioned related method steps to implement a control method for a three-dimensional CNC pipe bending machine provided in the above embodiment.

[0084] An embodiment of the present invention further provides a computer program product. When the computer program product is run on a computer, the computer is caused to execute the above-mentioned related steps to implement a control method for a three-dimensional CNC pipe bending machine provided in the above embodiment.

[0085] Among them, the device, computer-readable storage medium, computer program product or chip provided in the embodiments of the present invention are all used to execute the corresponding methods provided above. Therefore, the beneficial effects that can be achieved can refer to the beneficial effects in the corresponding methods provided above, and will not be repeated here. Through the description of the above implementation methods, technical personnel in the relevant field can understand that for the convenience and simplicity of description, only the division of the above-mentioned functional modules is used as an example. In actual applications, the above-mentioned functions can be distributed and completed by different functional modules as needed, that is, the internal structure of the device is divided into different functional modules to complete all or part of the functions described above. In the embodiments provided by the present invention, it should be understood that the disclosed device and method can be implemented in other ways.

[0086] The device embodiments described above are merely illustrative. For example, the division into modules or units represents only one logical functional division. Actual implementations may employ alternative divisions, such as combining or integrating multiple units or components into another device, or omitting or disabling certain features. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through an interface, or indirect coupling or communication connection between devices or units may be electrical, mechanical, or otherwise.

[0087] It should also be noted that, in this document, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or terminal device comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or terminal device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or terminal device comprising the element.

[0088] It should be noted that the order in which the embodiments of the present invention are described above is for illustrative purposes only and does not necessarily represent the superiority or inferiority of the embodiments. The processes depicted in the accompanying drawings do not necessarily require the specific order or sequential order shown to achieve the desired results. In certain embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0089] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments.

[0090] The above content is only a specific implementation method of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with this technical field can easily think of changes or replacements within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A control method for a three-dimensional CNC pipe bender, characterized in that: The method comprises the following steps: Get the pipe parameters of the pipe bending machine; Determining the initial stress of the pipe based on the pipe parameters and pipe material; determining the residual stress of the previous pipe section on the bending of the current pipe section based on the distance between the bending centers of the previous and next pipe sections, the effective influence distance, and the initial stress of the previous pipe section; combining the initial stress and the residual stress to obtain the total stress to which the pipe is subjected; and determining that the pipe may have cracks when the total stress exceeds a normal stress range; For pipes that may have cracks, the ellipse major axis orientation angle is determined based on the ellipse major axis orientation angle of the previous pipe, the pipe's rotation angle, and the azimuth offset. The azimuth offset is used to characterize the degree of influence of the bending curvature on the ellipse major axis orientation angle. The maximum tensile stress direction value is calculated based on the deviation between the ellipse major axis orientation angle and the bending radius. By calibrating the camera's viewing angle error and controlling the pipe's rotation angle in real time, the actual direction of the crack is obtained; the similarity between the maximum tensile stress direction value and the actual direction value is determined; and when the similarity exceeds a normal level, the production parameters of the pipe bending machine are adjusted.

2. The control method of the three-dimensional CNC pipe bender according to claim 1, characterized in that: The determining the initial stress of the pipe based on the pipe parameters and the pipe material includes: determining the ovality of the pipe cross section based on the pipe parameters; The initial stress of the current section of the pipe is determined by combining the ovality and the yield strength of the pipe material.

3. The control method of the three-dimensional CNC pipe bender according to claim 2, characterized in that: The determining of the ovality of the pipe cross section based on the pipe parameters includes: The pipe parameters include: bending angle, bending radius and pipe diameter of the pipe cross section; Determine the bending parameters based on the bending radius and diameter of the pipe; The ellipticity of the cross section of the tube is determined by combining the linear term with the quadratic term in combination with the bending parameters and the bending angle of the tube.

4. The control method of the three-dimensional CNC pipe bender according to claim 2, characterized in that: The determining the initial stress of the current section of the pipe by combining the ovality and the yield strength of the pipe material includes: The product of the ovality and the yield strength of the current pipe section is used as the initial stress of the current pipe section.

5. The control method of the three-dimensional CNC pipe bender according to claim 1, characterized in that: The method of determining the residual stress of the preceding pipe section on the bending of the current pipe section based on the distance between the bending centers of the preceding and following pipe sections, the effective influence distance, and the initial stress of the preceding pipe section includes: The initial stress of the previous section of pipe is corrected by the distance between the bending centers of the current and previous sections of pipe and the effective influence distance, resulting in the residual stress of the previous section of pipe on the bending of the current section. The distance between the bending centers of the front and rear ends of the pipe is negatively correlated with the residual stress, while the effective influence distance is positively correlated with the residual stress. The effective impact distance is determined by comparing the bending radius and thickness of the previous pipe.

6. The control method of the three-dimensional CNC pipe bender according to claim 1, characterized in that: The determining of the ellipse major axis direction angle according to the ellipse major axis direction angle of the previous section of the pipe, the pipe rotation angle, and the azimuth offset includes: The pipe parameters include: bending radius and pipe outer diameter; The angular offset is determined based on the bending radius and the outer diameter of the pipe, wherein the bending radius and the angular offset are negatively correlated, and the outer diameter of the pipe and the angular offset are positively correlated. The angular offset is a standardized value. The sum of the ellipse major axis direction angle of the previous section of the pipe, the pipe rotation angle, and the azimuth offset is used as the ellipse major axis direction angle of the current section; wherein the ellipse major axis direction angle is an angle value.

7. The control method of the three-dimensional CNC pipe bender according to claim 1, characterized in that: The calculation of the maximum tensile stress direction value based on the ellipse major axis direction angle and the bending radius deviation includes: The difference between the direction angle of the major axis of the ellipse and the right angle is determined as the conversion direction value; Determine the stress deviation angle caused by the bending direction based on the bending radius; The sum of the conversion direction value and the stress offset angle is calculated as the maximum tensile stress direction value.

8. The control method of the three-dimensional CNC pipe bender according to claim 1, characterized in that: The actual direction of the crack is obtained by calibrating the camera viewing angle error and controlling the rotation angle of the pipe in real time, including: Obtain a tube production image of a tube bending machine and determine the angle value of the crack direction in the tube production image; Determine the angle deviation coefficient by the vertical distance between the camera optical axis and the center axis of the pipe and the horizontal projection distance from the camera lens to the center axis of the pipe; Combined with the rotation angle and the angle deviation coefficient of the pipe, the angle value of the crack direction in the pipe production image is corrected to obtain the actual direction value of the crack.

9. The control method of the three-dimensional CNC pipe bender according to claim 1, characterized in that: The determining of the similarity between the maximum tensile stress direction value and the actual direction value includes: The difference between the maximum tensile stress direction value and the actual direction value is calculated, and negative correlation mapping is performed on the difference to obtain the similarity.

10. A three-dimensional CNC pipe bending machine, characterized in that: The system comprises a processor and a memory, wherein the processor is configured to process instructions stored in the memory to implement the monitoring process of the following modules: Data acquisition module, used to obtain pipe parameters of the pipe bending machine; A first analysis module is configured to determine the initial stress of the pipe based on the pipe parameters and the pipe material; Determine the residual stress of the preceding pipe section on the bending of the current pipe section based on the distance between the bending centers of the preceding and succeeding pipe sections, the effective influence distance, and the initial stress of the preceding pipe section; and calculate the total stress on the pipe section by combining the initial stress and the residual stress. When the total stress exceeds the normal stress range, the pipe is determined to be a pipe that may have cracks; The second analysis module is used to determine the major axis orientation angle of the ellipse for pipes that may have cracks based on the major axis orientation angle of the ellipse in the previous section of the pipe, the pipe's rotation angle, and the azimuth offset. The azimuth offset is used to characterize the degree to which the bending curvature affects the major axis orientation angle of the ellipse. The maximum tensile stress direction value is calculated based on the deviation between the major axis orientation angle of the ellipse and the bending radius. The parameter adjustment module is used to obtain the actual direction value of the crack through camera viewing angle error calibration and real-time control of the rotation angle of the pipe; determine the similarity between the maximum tensile stress direction value and the actual direction value; and adjust the production parameters of the pipe bending machine when the similarity exceeds a normal level.

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