A three-dimensional CNC pipe bending machine and its control method

Abstract

This invention relates to the field of metal processing technology, specifically to a three-dimensional CNC pipe bending machine and its control method. The method first determines the initial stress of the pipe based on pipe parameters and material; then determines the residual stress caused by the bending of the previous pipe section onto the current pipe section; combining the initial and residual stresses, the total stress on the pipe is obtained; when the total stress exceeds the normal stress range, the pipe is determined to be potentially cracked; for pipes potentially cracked, the elliptical major axis direction angle of the pipe cross-section is determined; based on the deviation between the elliptical major axis direction angle and the bending radius, the maximum tensile stress direction value is calculated; the actual crack direction value is obtained; the similarity between the maximum tensile stress direction value and the actual direction value is judged; when the similarity exceeds the normal level, the production parameters of the pipe bending machine are adjusted. This invention achieves real-time monitoring of the pipe material quality during the bending process, improving the real-time performance of adjusting the production parameters of the pipe bending machine.

Description

Technical Field

[0001] This invention relates to the field of metal processing technology, specifically to a three-dimensional CNC pipe bending machine and its control method. Background Technology

[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 and shape metal or non-metal pipes in three-dimensional space according to design requirements. From automotive engine piping and complex aerospace components to irregularly shaped pipes for building decoration, three-dimensional CNC pipe bending machines can efficiently complete complex multi-angle processing tasks. The emergence of this equipment has not only significantly improved the accuracy and efficiency of pipe processing but also effectively reduced the scrap rate through automated control. These types of pipe bending machines are currently widely used in high-end manufacturing, energy equipment, and other industries, becoming a key force driving the intelligent upgrading of pipe processing technology.

[0003] The quality inspection process of traditional three-dimensional CNC pipe bending machines usually sets the inspection steps after all bending operations are completed. This delayed inspection method may affect the actual production efficiency, because once a quality problem is found in the finished product, the processing time and material costs invested in the early stage will be wasted.

[0004] Currently, the common method for controlling 3D CNC pipe bending machines is to directly use machine vision to inspect the quality of the pipes. When the pipe quality is poor, production parameters are adjusted. However, some pipe quality problems are not caused by improper production parameters of the 3D CNC pipe bending machine, and these parameters cannot be used as the basis for adjusting production parameters. Therefore, directly adjusting production parameters when the pipe quality is poor has a low accuracy problem. Summary of the Invention

[0005] To address the issue of low accuracy in directly adjusting production parameters when pipe quality is poor, this invention aims to provide a three-dimensional CNC pipe bending machine and its control method. The specific technical solution adopted is as follows:

[0006] In a first aspect, embodiments of the present invention provide a control method for a three-dimensional CNC pipe bending machine, the method comprising:

[0007] Obtain the pipe parameters for the pipe bending machine;

[0008] Based on the pipe parameters and pipe material, the initial stress of the pipe is determined; based on the distance between the bending centers of the two pipe sections, the effective influence distance, and the initial stress of the preceding pipe section, the residual stress of the preceding pipe section on the bending of the current pipe section is determined; combining the initial stress and the residual stress, the total stress on the pipe is obtained; when the total stress exceeds the normal stress range, the pipe is determined to be a pipe that may have cracks.

[0009] For pipes that may have cracks, the direction angle of the major axis of the ellipse is determined based on the direction angle of the major axis of the previous section of the pipe, the rotation angle of the pipe, and the azimuth offset. The direction angle offset is used to characterize the degree of influence of the bending curvature on the direction angle of the major axis of the ellipse. The maximum tensile stress direction value is calculated based on the deviation between the direction angle of the major axis of the ellipse and the bending radius.

[0010] 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; when the similarity exceeds the normal level, the production parameters of the pipe bending machine are adjusted.

[0011] Further, determining the initial stress of the pipe based on the pipe parameters and pipe material includes:

[0012] The ellipticity of the pipe cross-section is determined based on the pipe parameters.

[0013] Based on the ellipticity and the yield strength of the pipe material, the initial stress of the current pipe section is determined.

[0014] Further, determining the ellipticity of the pipe cross-section based on the pipe parameters includes:

[0015] The pipe parameters include: bending angle, bending radius, and pipe diameter of the pipe cross-section;

[0016] Determine the bending parameters based on the bending radius and diameter of the pipe;

[0017] The ellipticity of the pipe cross-section is determined by combining linear and quadratic terms with the bending parameters and bending angle of the pipe.

[0018] Furthermore, determining the initial stress of the current pipe section by combining the ellipticity and the yield strength of the pipe material includes:

[0019] The product of the ellipticity and the yield strength of the current pipe section is used as the initial stress of the current pipe section.

[0020] Further, 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 two pipe sections, the effective influence distance, and the initial stress of the previous pipe section includes:

[0021] By using the distance between the bending centers of the current segment and the previous segment of pipe and the effective influence distance, the initial stress of the previous segment of pipe is corrected, and the residual stress of the previous segment of pipe on the bending of the current segment of pipe is obtained; among them, the distance between the bending centers of the two ends of the pipe is negatively correlated with the residual stress, and the effective influence distance is positively correlated with the residual stress.

[0022] The effective influence distance is determined by comparing the bending radius and thickness of the preceding pipe section.

[0023] Further, determining the major axis direction angle of the ellipse based on the major axis direction angle of the preceding pipe segment, the rotation angle of the pipe, and the azimuth offset includes:

[0024] The pipe parameters include: bending radius and outer diameter of the pipe;

[0025] The directional angle offset is determined based on the bending radius and the outer diameter of the pipe. The bending radius and the directional angle offset are negatively correlated, while the outer diameter of the pipe and the directional angle offset are positively correlated. The directional angle offset is a value after standardization.

[0026] The elliptical major axis direction angle of the previous segment of the pipe, the rotation angle of the pipe, and the azimuth offset are used as the elliptical major axis direction angle of the current segment; where the elliptical major axis direction angle is an angle value.

[0027] Furthermore, the calculation of the maximum tensile stress direction value based on the deviation between the major axis direction angle and the bending radius of the ellipse includes:

[0028] The difference between the direction angle of the major axis of the ellipse and the right angle is determined as the direction conversion value;

[0029] The stress offset angle caused by the bending direction is determined based on the bending radius;

[0030] The sum of the transformation direction value and the stress offset angle is calculated as the maximum tensile stress direction value.

[0031] Furthermore, the process of obtaining the actual crack trajectory value through camera viewpoint error calibration and real-time control of the pipe's rotation angle includes:

[0032] Obtain the pipe production image from the pipe bending machine and determine the angle value of the crack direction in the pipe production image;

[0033] The angle deviation coefficient is determined by the vertical distance between the camera's optical axis and the pipe's central axis, and the horizontal projection distance from the camera lens to the pipe's central axis.

[0034] By combining the rotation angle and 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.

[0035] Furthermore, determining the similarity between the maximum tensile stress direction value and the actual direction value includes:

[0036] Calculate the difference between the maximum tensile stress direction value and the actual direction value, and perform a negative correlation mapping on the difference value to obtain the similarity.

[0037] Secondly, a three-dimensional CNC pipe bending machine is provided, including a processor and a memory. The processor is used to process instructions stored in the memory to implement the monitoring process of the following modules. The memory stores executable code:

[0038] The data acquisition module is used to acquire the pipe parameters of the pipe bending machine;

[0039] The first analysis module is used to determine the initial stress of the pipe based on the pipe parameters and 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 two pipe sections, the effective influence distance, and the initial stress of the previous pipe section; combine the initial stress and the residual stress to obtain the total stress on the pipe; when the total stress exceeds the normal stress range, the pipe is determined to be a pipe that may have cracks.

[0040] The second analysis module is used to determine the elliptical major axis direction angle for pipes that may have cracks, based on the elliptical major axis direction angle of the previous section of pipe, the rotation angle of the pipe, and the azimuth offset. The azimuth offset is used to characterize the degree of influence of the bending curvature on the elliptical major axis direction angle. The maximum tensile stress direction value is calculated based on the deviation between the elliptical major axis direction angle and the bending radius.

[0041] The parameter adjustment module is used to obtain the actual direction value of the crack by calibrating the camera's viewing angle error and controlling the rotation angle of the pipe in real time; to determine the similarity between the maximum tensile stress direction value and the actual direction value; and to adjust the production parameters of the pipe bending machine when the similarity exceeds the normal level.

[0042] Thirdly, embodiments of the present invention provide a computer program product comprising: computer program code, which, when run on a computer, causes the computer to perform the method described in the first aspect or any possible implementation thereof.

[0043] Fourthly, embodiments of the present invention provide a computer-readable storage medium having a computer program stored thereon, which, when executed in a computer, causes the computer to perform the various possible implementations of the first aspect.

[0044] The embodiments of the present invention have at least the following beneficial effects:

[0045] This invention first determines the initial stress of the pipe based on its inherent properties. During the actual operation of a pipe bending machine, continuous bending of the pipe generates a cumulative effect of deformation and stress, directly leading to the risk of cracking in subsequent pipe sections. In pipe bending production plants, each pipe bending machine operates on a segment-by-segment bending process, pushing forward after each segment is bent. The deformation generated during the previous bending process affects the next segment. To accurately locate potential crack areas, it is necessary to determine the residual stress of the previous segment on the current bending process, combining the participating stress and initial stress to obtain the total stress on the pipe. This allows for the determination of whether the pipe is likely to crack, indicating that the potential crack is likely due to quality issues arising during the bending process. Subsequent testing and analysis will only target pipes that may have cracks, enabling timely detection of cracks and reducing wasted time. Furthermore, for pipes that may have cracks, the direction of the maximum tensile stress will be determined, and the actual direction of the crack will be compared with the direction of the maximum tensile stress. The similarity between the two will be used to adjust the production parameters of the pipe bending machine. Attached Figure Description

[0046] To more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 A flowchart illustrating a control method for a three-dimensional CNC pipe bending machine according to an embodiment of the present invention;

[0048] Figure 2 This is a schematic diagram of a three-dimensional CNC pipe bending machine provided in one embodiment of the present invention. Detailed Implementation

[0049] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a three-dimensional CNC pipe bending machine and its control method proposed according to the present invention.

[0050] In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments may be combined in any suitable form.

[0051] In the description of the embodiments of the present invention, unless otherwise stated, " / " means "or". For example, A / B can mean A or B. The "and / or" in the text is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone. In addition, in the description of the embodiments of the present invention, "multiple" means two or more.

[0052] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as implying or suggesting relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0053] Unless otherwise defined, 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 pertains.

[0054] The embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art will recognize that, with technological advancements and the emergence of new scenarios, the technical solutions provided by the embodiments of the present invention are also applicable to similar technical problems.

[0055] This invention provides a specific implementation method for a three-dimensional CNC pipe bending machine and its control method. This method is applicable to scenarios where the quality of pipes during bending operations is monitored in real time using image processing technology. In this scenario, the bending operation and monitoring steps are performed simultaneously, allowing for the detection of bent sections in the pipe. This enables timely detection of cracks and reduces wasted time. In pipe bending production plants, each pipe bending machine operates on a segment-by-segment bending process. After completing one segment of pipe bending, it is pushed forward, and the deformation generated during the previous segment affects the next segment. Based on this characteristic, pipes potentially prone to cracking are identified. If a crack appears in this area, the production parameters of the pipe bending machine are adjusted by analyzing the characteristics of the crack.

[0056] The following description, in conjunction with the accompanying drawings, details the specific scheme of a three-dimensional CNC pipe bending machine and its control method provided by the present invention.

[0057] Please see Figure 1 The diagram illustrates a flowchart of a control method for a three-dimensional CNC pipe bending machine according to an embodiment of the present invention. The method includes the following steps:

[0058] Step S100: Obtain the pipe parameters of the pipe bending machine.

[0059] In the production process of 3D CNC pipe bending machines, improving production efficiency is a key objective in optimizing the manufacturing process. However, traditional inspection methods often concentrate quality verification at the finished product stage. If a crack appears in the pipe during the second bending process, all subsequent processing steps become wasted time, resulting in a waste of time and materials. To overcome this efficiency bottleneck, the inspection process needs to have real-time response capabilities, that is, to trigger an early warning immediately when a crack defect occurs. Based on this, the state of the pipe during each bending process can be analyzed in detail, taking into account the segmented bending characteristics of the pipe bending machine, to ensure that the defect is identified at the initial stage.

[0060] To achieve efficient real-time monitoring of the 3D CNC pipe bending machine, high-frame-rate cameras are installed directly above the bending operation area and in front of the conveyor belt. Their shooting angles are aimed at the core operating area of ​​the bending machine head, capturing images of the pipe production process. When the bending machine starts its bending operation, the high-frame-rate cameras switch to high-speed shooting mode to quickly capture key details of the pipe bending process at a high frame rate. During the intervals between the completion of a single bending operation and the forward movement of the pipe, the cameras automatically reduce the shooting frame rate to minimize data redundancy and equipment energy consumption. This ensures monitoring accuracy while maximizing resource utilization and monitoring efficiency.

[0061] First, the pipe parameters of the pipe bending machine are obtained through the pipe production image. These parameters include the pipe bending angle θ, bending radius R, and pipe diameter D of the pipe cross-section.

[0062] 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.

[0063] Step S200: Based on the pipe parameters and pipe material, determine the initial stress of the pipe; based on the distance between the bending centers of the two pipe sections, the effective influence distance, and the initial stress of the previous pipe section, determine the residual stress of the previous pipe section on the bending of the current pipe section; combine the initial stress and the residual stress to obtain the total stress on the pipe; when the total stress exceeds the normal stress range, determine that the pipe is a pipe that may have cracks.

[0064] In the actual operation of a pipe bending machine, continuous bending of the pipe will produce a cumulative effect of deformation and stress, directly leading to the risk of cracking in subsequent pipe sections. To accurately locate potential crack areas, it is necessary to start from the essence of the pipe bending process and delineate the areas prone to cracking based on the preset parameters in the pipe bending machine: the degree of bending of the preceding pipe section directly determines the degree of elliptical deformation of the pipe. The stronger the bending, the higher the ellipticity, and the stronger the stress concentration effect at the major axis endpoint, thus increasing the possibility of cracking when bending the subsequent pipe section; the distance between the subsequent section and the center of the preceding bend affects the superposition range of the stress field; too small a distance will cause the residual stress from the previous section to superimpose with the current bending stress.

[0065] In pipe bending operations, the degree of bending in the first section is a key factor affecting the likelihood of cracks appearing in the next section of the pipe. Based on the positive correlation between bending deformation and stress concentration, the greater the degree of bending, the more pronounced the ellipticization of the pipe cross-section, and the more severe the tensile deformation of the material at the endpoints of the major axis of the ellipse. This leads to increased stress concentration, and the internal residual stress also increases accordingly, making it more susceptible to cracking in the subsequent bending section due to the inability to withstand the new stress.

[0066] Based on the pipe parameters, the ellipticity of the pipe cross-section is determined. Specifically: First, the bending parameters are determined based on the pipe's bending radius and diameter; these bending parameters are the ratio of the pipe's diameter to its bending radius.

[0067] The ellipticity of the pipe cross-section is determined by combining linear and quadratic terms with the bending parameters and bending angle of the pipe.

[0068] In some embodiments, the ellipticity of the pipe cross-section The calculation formula is:

[0069] ;in, The first fitting coefficient; θ is the second fitting coefficient; R is the bending angle of the pipe; D is the bending radius; and D is the pipe diameter of the pipe cross-section. In this embodiment of the invention, the first fitting coefficient is 0.03 and the second fitting coefficient is 0.03. These two values ​​can be adjusted by the implementer according to the actual situation.

[0070] in, This indicates that the curvature parameter Converted to the dimensionless reciprocal of the relative bending radius, facilitating standardized calculations for different pipe diameters. Linear term. The stage with relatively small dominant deformation reflects the linear superposition effect of bending curvature and deformation; quadratic term The stage with the largest dominant deformation is characterized by the acceleration process of nonlinear deformation. 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.

[0071] During the operation of a pipe bending machine, the previous bend creates a residual stress field inside the pipe, causing elliptical deformation. When a subsequent bend occurs immediately after the previous one, the remaining residual stress combines with the newly generated bending stress, significantly increasing the local stress. This not only exacerbates the distortion of the pipe's cross-section but also makes the material highly susceptible to cracking at the new bend.

[0072] The ellipticity is used to calculate the reference stress of the subsequent segment. This stress is the stress independently generated by the bending of the subsequent segment without considering the influence of the previous segment. During the pipe bending process, the pipe cross-section will form an ellipse due to bending deformation. Therefore, the initial stress calculated based on the ellipticity is specifically: the product of the ellipticity and the yield strength of the current segment of the pipe is used as the initial stress of the current segment of the pipe. The greater the yield strength, the higher the stress generated under the same deformation.

[0073] In some embodiments, the initial stress The calculation formula is: ;in, These are empirical coefficients used to adjust the quantitative relationship between ellipticity and residual stress; The ellipticity of the current pipe section cross-section; This represents the yield strength of the current section of pipe.

[0074] Based on the stress exerted by the previous segment on the current segment, and taking the stress of the previous segment during bending as a foundation, the residual stress of the previous segment on the current segment's bending is determined according to the distance between the bending centers of the two segments, the effective influence distance, and the initial stress of the previous segment. Specifically, the initial stress of the previous segment is corrected by the distance between the bending centers of the current and previous segments and the effective influence distance to obtain the residual stress of the previous segment on the current segment's bending. The distance between the bending centers of the two segments is negatively correlated with the residual stress, while the effective influence distance is positively correlated with the residual stress. The effective influence distance is determined by comparing the bending radius and thickness of the previous segment. Specifically, three times the bending radius and five times the thickness are compared, and the larger of the two values ​​is determined as the effective influence distance.

[0075] In some embodiments, residual stress The calculation formula is: ;in, This represents the initial stress of the preceding section of pipe; is the stress superposition coefficient; e is the natural constant; L is the distance between the bending centers of the current segment and the previous segment of the pipe; This represents the effective distance of the previous section of pipe bending on the current section of pipe.

[0076] The stress superposition coefficient is used to reflect the correction of stress transfer efficiency by material properties and process conditions. The better the plasticity of the material, the larger the stress superposition coefficient, and the more significant the stress transfer. In the bending process, the greater the friction of the die, the smaller the stress superposition coefficient.

[0077] When the distance between the bending centers of the current segment and the previous segment of the pipe increases, The effect of residual stress in the previous segment on the current segment decreases as the distance between the two segments increases.

[0078] The total stress on the pipe is obtained by combining the initial stress and the residual stress. Specifically, the sum of the initial stress and the residual stress is used as the total stress on the pipe. In some embodiments, the total stress on the current segment of the pipe is... The calculation formula is: ;in, This represents the initial stress of the current segment itself; This represents the residual stress caused by the previous section bending the current section of the pipe.

[0079] Based on the total stress experienced by the pipe, areas potentially exceeding the pipe's strength are identified. When the total stress exceeds the normal stress range, the pipe is deemed potentially prone to cracking. The upper limit of the normal stress range is determined as the ratio of the pipe material's yield strength ω to the safety factor n, where the lower limit is 0. Therefore, the normal stress range is 0 to ω / n. In this embodiment, when the pipe is an automotive part, the safety factor ranges from 2.5 to 4; when the pipe is an aero-engine part, the safety factor ranges from 5 to 8. When the total stress exceeds the normal stress range, the stress experienced by the pipe exceeds its own withstand limit, potentially causing cracks, and the corresponding pipe is deemed potentially prone to cracking.

[0080] By identifying potentially cracked pipes in advance, the scope of investigation can be quickly narrowed down once a crack appears, based on the previously defined risk area. Combined with the characteristics of the crack, the root cause of the crack can be traced more accurately. From a cost control perspective, accurately locating risk areas avoids the waste of resources in full-area monitoring, reduces detection costs, and shortens the time for fault location and repair.

[0081] Step S300: For pipes that may have cracks, determine the direction angle of the major axis of the ellipse based on the direction angle of the major axis of the previous section of the pipe, the rotation angle of the pipe, and the azimuth offset; wherein, the direction angle offset is used to characterize the degree of influence of the bending curvature on the direction angle of the major axis of the ellipse; and calculate the direction value of the maximum tensile stress based on the deviation between the direction angle of the major axis of the ellipse and the bending radius.

[0082] Pipes that may have cracks are subject to key monitoring. Once a real crack defect appears in a region, an analysis is conducted based on the specific characteristics of the crack: First, the direction of the maximum tensile stress is accurately calculated based on the deviation of the major axis azimuth of the ellipse and the bending radius; then, the actual direction of the crack is obtained through camera perspective error calibration and real-time control of the pipe rotation angle; 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.

[0083] In actual pipe bending production, the pipe bending machine determines whether to rotate the pipe during each operation based on product requirements. Pipe rotation directly affects the crack's orientation; changes in the rotation angle cause a shift in the major axis of the pipe's cross-section, resulting in a simultaneous change in the direction of maximum tensile stress. Therefore, this crucial factor must be considered when determining crack orientation.

[0084] Calculating the actual azimuth angle of the major axis of the current bending segment provides a basis for determining the direction of the maximum tensile stress. Because the pipe cross-section changes from circular to elliptical during bending, and the azimuth angle of the major axis directly affects the direction of the maximum tensile stress. Furthermore, considering that the bending curvature will cause an additional offset to the major axis of the ellipse, it is necessary to combine the azimuth angle of the previous segment of the pipe to correct the azimuth angle of the current segment. In this embodiment of the invention, the method for obtaining the azimuth angle of the previous segment of the pipe is as follows: First, obtain the image corresponding to the pipe cross-section, which is elliptical. Obtain the angle between the major axis of the ellipse and the horizontal line pointing to the right, as the azimuth angle of the pipe's major axis. It should be noted that the azimuth angle is a single angle value.

[0085] The elliptical major axis orientation angle of the previous pipe segment, the pipe's rotation angle, and the azimuth offset are used as the elliptical major axis orientation angle of the current segment. The azimuth offset is determined based on the bending radius and the pipe's outer diameter. The bending radius and the orientation angle offset are negatively correlated, while the pipe's outer diameter and the orientation angle offset are positively correlated. The orientation angle offset is a standardized value. The orientation angle offset characterizes the degree of influence of the bending curvature on the elliptical major axis orientation angle.

[0086] The rotation angle of the pipe is defined as follows: the angle formed by the pipes that is less than 180° is taken as the pipe orientation angle, and the acute angle formed by the center line of the pipe orientation angle and the horizontal line to the right is taken as the pipe rotation angle.

[0087] In some embodiments, the direction angle offset The calculation formula is: ;in, The preset offset empirical value is set to 0.1~0.3 in this embodiment of the invention. In other embodiments, the implementer may adjust the value according to the actual situation. The preset offset empirical value is used to reflect the degree of influence of the curvature on the azimuth of the major axis of the ellipse; D is the diameter of the pipe; R is the bending radius.

[0088] The maximum tensile stress direction value is calculated based on the deviation between the major axis direction angle and the bending radius of the ellipse.

[0089] The difference between the direction angle of the major axis of the ellipse and the right angle is determined as the transformation direction value; the stress offset angle caused by the bending direction is determined according to the bending radius; when the bending direction is outward, the sum of the transformation direction value and the stress offset angle is calculated as the maximum tensile stress direction value; when the bending direction is inward, the difference between the transformation direction value and the stress offset angle is calculated as the maximum tensile stress direction value.

[0090] In some embodiments, the maximum tensile stress direction value The calculation formula is: ;in, This is the direction angle of the major axis of the ellipse in the current segment; This is the value for changing the direction; This is the stress offset angle.

[0091] The stress offset angle The calculation formula is: ;in, These are empirical values ​​and can be adjusted by the implementer based on actual conditions. The greater the difference between the bending radius and three times the outer diameter of the pipe, the greater the deviation. And the deviation of the bending radius from... The more [stress] present, the more pronounced the stress shift becomes.

[0092] Step S400: By calibrating the camera's viewing angle error and controlling the pipe's rotation angle in real time, the actual direction value of the crack is obtained; the similarity between the maximum tensile stress direction value and the actual direction value is determined; when the similarity exceeds the normal level, the production parameters of the pipe bending machine are adjusted.

[0093] The images captured by the camera show the pipes produced by the pipe bending machine. For each pipe production image, crack pixels are identified. A straight line is fitted to these crack pixels, and the angle between the fitted line and a horizontal line pointing to the right is used as the angle of the crack's 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 algorithm, and these edge pixels (excluding the pipe edges) can be considered as crack pixels.

[0094] The angle value of the crack direction in the pipe production image is determined and calibrated to the actual direction angle relative to the initial axis of the pipe. Because pipe rotation and camera shooting angle can cause deviations between the crack's apparent direction and its actual direction, the actual direction value of the crack is obtained by calibrating the camera's viewing angle error and controlling the pipe's rotation angle in real time.

[0095] Specifically: by combining the rotation angle of the pipe and the angle deviation coefficient, the angle value of the crack direction in the pipe production image is corrected to obtain the actual direction value of the crack.

[0096] In some embodiments, the actual direction value of the crack The calculation formula is: ;in, The angle value for the direction of the crack; The rotation angle of the pipe; This is the angle deviation coefficient caused by the camera's perspective.

[0097] 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.

[0098] Angular deviation coefficient The calculation formula is: Where h is the vertical distance between the camera's optical axis and the pipe's central axis; L is the horizontal projection distance from the camera lens to the pipe's central axis; and arctan is the arctangent function.

[0099] The 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 perpendicular distance h between the camera's optical axis and the pipe's central axis 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's production image onto the plane presented in the image is consistent with the actual angle, with no deviation. However, when the perpendicular distance between the camera's optical axis and the pipe's central axis changes, that is, when the camera shifts, and the camera is no longer looking directly at the pipe, the line of sight is tilted. In this case, the image of the radial section where the crack is located on the surface of the photosensitive element will change. The direction 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... , , Let r be the polar angle and r be the polar radius. The polar angle represents the angle between a point on a plane and the polar axis, and the polar radius represents the distance from the point to the pole (origin). In this embodiment of the invention, the theoretical basis for the angle deviation coefficient is... In this embodiment of the invention, the polar axis is the positive x-axis direction.

[0100] By using a pipe rotation angle meter and an angle deviation coefficient, the angle deviation of crack direction caused by vision was corrected.

[0101] Furthermore, the similarity between the maximum tensile stress direction value and the actual direction value is determined, and the pipe parameters are adjusted when the similarity exceeds the normal level.

[0102] Specifically: calculate the difference between the maximum tensile stress direction value and the actual direction value, and perform a negative correlation mapping on the difference value to obtain the similarity.

[0103] In some embodiments, similarity The calculation formula is: ;in, This represents the actual direction of the crack. This represents the value in the direction of the maximum tensile stress.

[0104] In the formula for calculating similarity, The absolute deviation between the actual crack direction and the stress direction reflects 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 caused by stress. The "theoretical maximum deviation benchmark" represents the stress-dominant crack, where the direction of maximum tensile stress is theoretically perpendicular to the major axis of the ellipse (i.e., the angle is 90°). The absolute deviation is converted into "similarity γ" using "1-", directly linking the range of γ's values ​​to its 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, it indicates that the two directions are highly consistent, and stress-dominant cracks are generated. If the γ of a certain batch of pipes is generally high, such as γ>0.5 accounting for more than 70%, it can be adjusted according to the actual situation. This indicates that the proportion of stress-dominant cracks is high, and the production parameters need to be adjusted to reduce stress concentration. The production parameters of the pipe bending machine include: the rotation angle of the pipe and the bending radius.

[0105] If a batch of pipes shows a high proportion of similarity γ values ​​during testing, it indicates that stress-dominated cracks are predominant in that batch. In this case, systematic control of the pipe bending machine's production parameters is necessary to achieve a closed-loop control from passive crack detection to active adjustment of production parameters: Firstly, moderately increase the pipe's rotation angle to change the azimuth of the subsequent pipe's major axis, thereby adjusting the direction of maximum tensile stress; simultaneously, appropriately increase the bending radius to alleviate stress concentration caused by excessive bending. After adjustment, conduct a small-batch trial production of the next batch of pipes, comparing and analyzing the distribution of similarity γ values ​​before and after 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 production; otherwise, further optimize the rotation angle and bending radius until the proportion of stress-dominated cracks is controlled within the expected range. It should be noted that a preset fixed increase angle of 5° can be used to increase the pipe's rotation angle and bending radius. In other embodiments, the implementer can adjust the preset fixed increase angle according to different adjustment accuracy requirements.

[0106] Please see Figure 2 , Figure 2 This invention provides a schematic diagram of a three-dimensional CNC pipe bending machine, including a processor and a memory. The processor processes instructions stored in the memory to implement the monitoring process of the following module. The memory stores executable code:

[0107] The data acquisition module is used to acquire the pipe parameters of the pipe bending machine;

[0108] The first analysis module is used to determine the initial stress of the pipe based on the pipe parameters and 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 two pipe sections, the effective influence distance, and the initial stress of the previous pipe section; combine the initial stress and the residual stress to obtain the total stress on the pipe; when the total stress exceeds the normal stress range, the pipe is determined to be a pipe that may have cracks.

[0109] The second analysis module is used to determine the elliptical major axis direction angle for pipes that may have cracks, based on the elliptical major axis direction angle of the previous section of pipe, the rotation angle of the pipe, and the azimuth offset. The azimuth offset is used to characterize the degree of influence of the bending curvature on the elliptical major axis direction angle. The maximum tensile stress direction value is calculated based on the deviation between the elliptical major axis direction angle and the bending radius.

[0110] The parameter adjustment module is used to obtain the actual direction value of the crack by calibrating the camera's viewing angle error and controlling the rotation angle of the pipe in real time; to determine the similarity between the maximum tensile stress direction value and the actual direction value; and to adjust the production parameters of the pipe bending machine when the similarity exceeds the normal level.

[0111] Alternatively, the transmission medium may be a wired link, such as, but not limited to, coaxial cable, fiber optic cable and digital subscriber line, or a wireless link, such as, but not limited to, wireless Fidelity (WIFI), Bluetooth and mobile device networks.

[0112] It should be noted that the device provided in the above embodiments is only an example of 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.

[0113] Furthermore, embodiments of the present invention also protect an apparatus that 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 in embodiments of the present invention.

[0114] In this embodiment of the invention, the device can be divided into functional modules according to the above method example. For example, each module can correspond to a separate function, or two or more functions can be integrated into one processing module. The integrated module can be implemented in hardware. It should be noted that the module division in this embodiment is illustrative and is only a logical functional division. In actual implementation, there may be other division methods.

[0115] When each module is divided according to its function, the device may also include a signal uploading module, a determination module, and an adjustment module. It should be noted that all relevant content of each step involved in the above method embodiments can be referenced from the functional descriptions of the corresponding functional modules, and will not be repeated here.

[0116] It should be understood that the device provided in this embodiment of the invention is used to execute the control method of a three-dimensional CNC pipe bending machine described above, and therefore can achieve the same effect as the above implementation method.

[0117] When using integrated units, the device may include a processing module and a storage module. When 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 may be a processor or a controller, which can implement or execute various exemplary logic blocks, modules, and circuits as described in this disclosure. The processor may also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of Digital Signal Processing (DSP) and a microprocessor, etc., and the storage module may be a memory.

[0118] In addition, the device provided in the embodiments of the present invention may specifically be a chip, component or module. The chip may include a connected processor and a memory. The memory is used to store instructions. When the processor calls and executes the instructions, the chip can execute the control method of a three-dimensional CNC pipe bending machine provided in the above embodiments.

[0119] This invention also provides a computer-readable storage medium storing computer program code. When the computer program code is run on a computer, the computer executes the aforementioned method steps to implement the control method for a three-dimensional CNC pipe bending machine provided in the above embodiments.

[0120] This invention also provides a computer program product that, when run on a computer, causes the computer to perform the aforementioned steps to implement the control method for a three-dimensional CNC pipe bending machine provided in the above embodiments.

[0121] In this invention, the apparatus, computer-readable storage medium, computer program product, or chip provided in the embodiments are all used to execute the corresponding methods described above. Therefore, the beneficial effects they achieve can be referred to the beneficial effects in the corresponding methods described above, and will not be repeated here. Through the above description of the embodiments, those skilled in the art will understand that, for the sake of convenience and brevity, only the division of the above functional modules is used as an example. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above. In the embodiments provided by this invention, it should be understood that the disclosed apparatus and method can be implemented in other ways.

[0122] The device embodiments described above are merely illustrative. For example, the division of modules or units is only a logical functional division. In actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another device, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0123] It should also be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes said element.

[0124] It should be noted that the order of the above embodiments of the present invention is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. The processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0125] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0126] The above content is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the protection scope of the present invention.

Claims

1. A control method for a three-dimensional CNC pipe bending machine, characterized in that, The method includes the following steps: Obtain the pipe parameters for the pipe bending machine; Based on the pipe parameters and pipe material, the initial stress of the pipe is determined; based on the distance between the bending centers of the two pipe sections, the effective influence distance, and the initial stress of the preceding pipe section, the residual stress of the preceding pipe section on the bending of the current pipe section is determined; combining the initial stress and the residual stress, the total stress on the pipe is obtained; when the total stress exceeds the normal stress range, the pipe is determined to be a pipe that may have cracks. For pipes that may have cracks, the direction angle of the major axis of the ellipse is determined based on the direction angle of the major axis of the previous section of the pipe, the rotation angle of the pipe, and the azimuth offset. The direction angle offset is used to characterize the degree of influence of the bending curvature on the direction angle of the major axis of the ellipse. The maximum tensile stress direction value is calculated based on the deviation between the direction angle of the major axis of the ellipse 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; when the similarity exceeds the normal level, the production parameters of the pipe bending machine are adjusted.

2. The control method for a three-dimensional CNC pipe bending machine according to claim 1, characterized in that, Determining the initial stress of the pipe based on the pipe parameters and pipe material includes: The ellipticity of the pipe cross-section is determined based on the pipe parameters. Based on the ellipticity and the yield strength of the pipe material, the initial stress of the current pipe section is determined.

3. The control method for a three-dimensional CNC pipe bending machine according to claim 2, characterized in that, Determining the ellipticity 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 pipe cross-section is determined by combining linear and quadratic terms with the bending parameters and bending angle of the pipe.

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

5. The control method for a three-dimensional CNC pipe bending machine according to claim 1, characterized in that, The determination of the residual stress exerted by the preceding pipe segment on the current pipe segment during bending, based on the distance between the bending centers of the two pipe segments, the effective influence distance, and the initial stress of the preceding pipe segment, includes: By using the distance between the bending centers of the current segment and the previous segment of pipe and the effective influence distance, the initial stress of the previous segment of pipe is corrected, and the residual stress of the previous segment of pipe on the bending of the current segment of pipe is obtained; among them, the distance between the bending centers of the two ends of the pipe is negatively correlated with the residual stress, and the effective influence distance is positively correlated with the residual stress. The effective influence distance is determined by comparing the bending radius and thickness of the preceding pipe section.

6. The control method for a three-dimensional CNC pipe bending machine according to claim 1, characterized in that, The determination of the major axis direction angle of the ellipse based on the major axis direction angle of the preceding pipe segment, the rotation angle of the pipe, and the azimuth offset includes: The pipe parameters include: bending radius and outer diameter of the pipe; The directional angle offset is determined based on the bending radius and the outer diameter of the pipe. The bending radius and the directional angle offset are negatively correlated, while the outer diameter of the pipe and the directional angle offset are positively correlated. The directional angle offset is a value after standardization. The elliptical major axis direction angle of the previous segment of the pipe, the rotation angle of the pipe, and the azimuth offset are used as the elliptical major axis direction angle of the current segment; where the elliptical major axis direction angle is an angle value.

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

8. The control method for a three-dimensional CNC pipe bending machine according to claim 1, characterized in that, The method of obtaining the actual crack direction value through camera viewpoint error calibration and real-time control of pipe rotation angle includes: Obtain the pipe production image from the pipe bending machine and determine the angle value of the crack direction in the pipe production image; The angle deviation coefficient is determined by the vertical distance between the camera's optical axis and the pipe's central axis, and the horizontal projection distance from the camera lens to the pipe's central axis. By combining the rotation angle and 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 for a three-dimensional CNC pipe bending machine according to claim 1, characterized in that, The determination of the similarity between the maximum tensile stress direction value and the actual direction value includes: Calculate the difference between the maximum tensile stress direction value and the actual direction value, and perform a negative correlation mapping on the difference value to obtain the similarity.

10. A three-dimensional CNC pipe bending machine, characterized in that, Includes a processor and a memory, the processor being used to process instructions stored in the memory to implement the monitoring process of the following modules: The data acquisition module is used to acquire the pipe parameters of the pipe bending machine; The first analysis module is used to determine the initial stress of the pipe based on the pipe parameters and pipe material; Based on the distance between the bending centers of the two pipe sections, the effective influence distance, and the initial stress of the preceding pipe section, the residual stress of the preceding pipe section on the bending of the current pipe section is determined; combining the initial stress and the residual stress, the total stress on the pipe is obtained. 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 elliptical major axis direction angle for pipes that may have cracks, based on the elliptical major axis direction angle of the previous section of pipe, the rotation angle of the pipe, and the azimuth offset. The azimuth offset is used to characterize the degree of influence of the bending curvature on the elliptical major axis direction angle. The maximum tensile stress direction value is calculated based on the deviation between the elliptical major axis direction angle and the bending radius. The parameter adjustment module is used to obtain the actual direction value of the crack by calibrating the camera's viewing angle error and controlling the rotation angle of the pipe in real time; to determine the similarity between the maximum tensile stress direction value and the actual direction value; and to adjust the production parameters of the pipe bending machine when the similarity exceeds the normal level.

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