Method for extracting corrosion depth distribution based on three-dimensional point cloud and related device

Abstract

The embodiment of the application provides a kind of based on three-dimensional point cloud's corrosion depth distribution extraction method and related device, method includes: first, the three-dimensional point cloud data of the outer surface of the steel wire to be measured is obtained, and curved steel wire is converted to straight coordinate system, the radial distance and ring angle of each surface point are calculated;Then segmented point cloud is carried out according to preset interval along axial direction, in each segment, based on the median and median absolute deviation of outer deviation, threshold is set, the abnormal point located outside the cross section fitting circle is removed, and the real point in the corrosion pit is retained;Then, the uncorroded section at both ends is set as reference section, the radius sequence is fitted, and the median value is taken as global reference radius;Finally, for the retained real point, the absolute corrosion depth is calculated, and the corrosion depth distribution probability density diagram and two-dimensional heat map are output, the interference problem of scanning noise, registration error and outside fly point to corrosion depth statistics can be solved, and the data purity and result reliability of corrosion depth calculation are significantly improved.

Description

Technical Field

[0001] This application relates to the field of image processing technology, specifically to a method and related apparatus for extracting corrosion depth distribution based on three-dimensional point clouds. Background Technology

[0002] Currently, 3D scanning technology has been widely applied in the field of corrosion damage assessment of steel wires in bridge cables. By acquiring 3D point cloud data of the outer surface of the steel wire through laser scanning, the geometric morphology of corrosion pits can be further extracted, and evaluation indicators such as pit depth and corrosion area can be calculated based on the point cloud coordinates. Existing methods typically use the centroid of the point cloud or the fitted axis as a reference to calculate the radial distance from each surface point to the reference center, and then compare it with the baseline radius of the uncorroded area to obtain the corrosion depth distribution.

[0003] However, since the steel wires in service generally have natural curvature, the point cloud obtained by 3D scanning is accompanied by axis offset and cross-sectional coordinate system disorder. In addition, noise and external anomalies are easily generated during the scanning process. Existing corrosion depth distribution extraction methods are difficult to adapt to the geometric reference offset characteristics of point clouds under bending conditions, and cannot effectively remove external false anomalies and retain real corrosion pit data. As a result, corrosion depth calculation has obvious deviations and low reliability of results. Summary of the Invention

[0004] This application provides a method and related apparatus for extracting corrosion depth distribution based on three-dimensional point clouds, which can solve the problems of interference from scanning noise, registration error and outer flying points on corrosion depth statistics, and significantly improve the data purity and result reliability of corrosion depth calculation.

[0005] A first aspect of this application provides a method for extracting corrosion depth distribution based on three-dimensional point clouds, the method comprising: Acquire three-dimensional point cloud data of the outer surface of the steel wire to be tested; The three-dimensional point cloud data is straightened by axis straightening, and the three-dimensional point cloud of the bent steel wire is transformed into the straightened coordinate system, so that the center line of the straightened steel wire extends along the straight line direction, and the straightened coordinate system is obtained. In the straightened coordinate system, with the center line as the reference axis, calculate the radial distance and circumferential angle of each surface point; The point cloud is segmented along the axis of the straightened coordinate system at a preset interval to obtain multiple local analysis segments; In each of the aforementioned local analysis sections, outlier points located outside the cross-sectional fitting circle are removed, while true points within the corrosion pits are retained. Determine the global baseline radius based on the uncorroded segment; For the actual points within the retained corrosion pits, the absolute corrosion depth is calculated based on the corresponding radial distance and the global reference radius, and the corrosion depth distribution information is output.

[0006] In one possible implementation, the point cloud is segmented along the axis of the straightened coordinate system at preset intervals to obtain multiple local analysis segments, including: The straightened point cloud is divided into multiple local analysis sections according to the preset axial spacing; Remove local analysis sections with insufficient data points.

[0007] In one possible implementation, In each of the aforementioned local analysis sections, outlier points located outside the fitted circle of the cross-section are removed, while true points within the corrosion pits are retained. This includes: Calculate the outward deviation of each surface point relative to the radius of the fitted circle of its local analysis segment; For each local analysis segment, the points located outside the cross-sectional fitting circle are counted, and the median of the external deviation is calculated as the overall level of external deviation. Calculate the absolute deviation of the out-of-range point from the median, and use it as the range of fluctuation; Based on the overall level and fluctuation range of the external deviation, a threshold is set to determine the actual point within the corrosion pit.

[0008] In one possible implementation, The step of setting a threshold based on the overall level and fluctuation range of the external deviation to determine the true points within the corrosion pit includes: Points located outside the cross-section fitting circle and whose outward deviation exceeds the threshold are identified as outliers and removed. The points inside the cross-sectional fitting circle and the points outside the cross-sectional fitting circle but whose outward deviation does not exceed the threshold are collected to obtain the true points inside the corrosion pit.

[0009] In one possible implementation, determining the global reference radius based on the uncorroded segment includes: The uneroded segments at both ends of the point cloud are set as reference segments. The reference segments are finely sliced, and a reference radius is fitted to each slice to obtain a radius sequence. The median of the radius sequence is used as the global baseline radius.

[0010] In one possible implementation, In the calculation of the absolute corrosion depth for the retained actual points within the corrosion pits, based on the corresponding radial distance and the global reference radius, the formula for calculating the absolute corrosion depth is as follows: In the formula, For the first The radial distance from each point to the reference center of the cross section The uncorroded reference radius, This represents the absolute corrosion depth.

[0011] In one possible implementation, the output corrosion depth distribution information includes: The absolute corrosion depth of all the real points within the retained corrosion pits is statistically analyzed, and a corrosion depth distribution probability density map is generated and output. The statistical results of corrosion depth based on axial position and circumferential angle are organized into a two-dimensional matrix, and a two-dimensional heat map of corrosion depth is generated and output through color mapping.

[0012] This example provides a method for extracting corrosion depth distribution based on 3D point clouds. First, 3D point cloud data of the outer surface of the steel wire to be tested is acquired and straightened along its axis. The bent steel wire is then transformed to a straightened coordinate system, and the radial distance and circumferential angle of each surface point are calculated using the straightened centerline as the reference axis. Next, the point cloud is segmented along the axial direction at preset intervals. In each segment, a threshold is set based on the median of the external offset and the absolute deviation of the median. Outliers located outside the fitted circle of the cross-section are removed, and true points within the corrosion pits are retained. Then, the uncorroded sections at both ends are set as reference sections. A radius sequence is obtained through fine slicing and fitting, and the median is taken as the global reference radius. Finally, for the retained true points, the absolute corrosion depth is calculated based on the difference between the radial distance and the global reference radius, and a corrosion depth distribution probability density map and a 2D heat map are output. Compared with existing technologies, this invention has the following advantages: 1. By calculating the external deviation of surface points relative to the radius of the fitted circle in each analysis segment, and setting an adaptive threshold based on the median and median absolute deviation of the external deviation, only outlier points located outside the fitted circle of the cross section and whose deviation exceeds the threshold are removed, while the corrosion pit bottom points inside the fitted circle of the cross section are completely retained. This solves the problem of interference from scanning noise, registration error and external flying points on corrosion depth statistics, and significantly improves the data purity and result reliability of corrosion depth calculation.

[0013] 2. By setting the uncorroded sections at both ends of the steel wire as reference sections, finely slicing the reference sections and fitting the radii of each slice, and then using the median of the radius sequence as the global reference radius, the problem of single-point or single-section reference radii being easily affected by local morphological fluctuations is avoided, making the reference radius statistically robust, thereby ensuring the accuracy and consistency of the calculation of the absolute corrosion depth at each point within the corroded section.

[0014] 3. By outputting the probability density map of corrosion depth distribution and the two-dimensional heat map, the absolute corrosion depth calculated point by point is visualized in multiple dimensions along the depth range, axial position and circumferential angle. This not only reflects the overall statistical distribution characteristics of corrosion depth intuitively, but also accurately identifies the spatial non-uniformity of corrosion along the length and circumference of the steel wire, providing reliable data support for the evaluation of corrosion degree of bridge cable steel wire and the location of local pitting corrosion.

[0015] A second aspect of this application provides a corrosion depth distribution extraction system based on three-dimensional point clouds, the system comprising: The first module is used to acquire three-dimensional point cloud data of the outer surface of the steel wire to be tested; The second module is used to straighten the axis of the three-dimensional point cloud data, transforming the three-dimensional point cloud of the bent steel wire into the straightened coordinate system, so that the center line of the straightened steel wire extends along the straight line direction, and the straightened coordinate system is obtained. The third module is used to calculate the radial distance and circumferential angle of each surface point in the straightened coordinate system, with the center line as the reference axis. The fourth module is used to segment the point cloud along the axis of the straightened coordinate system at preset intervals to obtain multiple local analysis segments; The fifth module is used to remove abnormal points located outside the cross-sectional fitting circle in each of the local analysis sections, and retain the true points inside the corrosion pits. The sixth module is used to determine the global baseline radius based on the uncorroded segment; The seventh module is used to calculate the absolute corrosion depth for the real points within the retained corrosion pits based on the corresponding radial distance and the global reference radius, and output corrosion depth distribution information.

[0016] A third aspect of this application provides a terminal including a processor, an input device, an output device, and a memory, wherein the processor, input device, output device, and memory are interconnected, wherein the memory is used to store a computer program, the computer program including program instructions, and the processor is configured to invoke the program instructions to execute the step instructions as described in the three-dimensional point cloud-based erosion depth distribution extraction method in the first aspect of this application.

[0017] A fourth aspect of this application provides a computer-readable storage medium storing a computer program for electronic data interchange, wherein the computer program causes a computer to perform some or all of the steps described in the corrosion depth distribution extraction method based on three-dimensional point clouds in the first aspect of this application.

[0018] A fifth aspect of this application provides a computer program product, comprising a non-transitory computer-readable storage medium storing a computer program operable to cause a computer to perform some or all of the steps described in the erosion depth distribution extraction method based on three-dimensional point clouds in the first aspect of this application. The computer program product may be a software installation package. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application 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 this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This application provides a flowchart illustrating a method for extracting corrosion depth distribution based on three-dimensional point clouds in an embodiment of the present application. Figure 2 This application provides a schematic diagram of corrosion depth distribution density for an embodiment of a corrosion depth distribution extraction method based on three-dimensional point clouds. Figure 3 This application provides a two-dimensional thermodynamic diagram of corrosion depth based on a three-dimensional point cloud-based corrosion depth distribution extraction method. Figure 4 This application provides a schematic diagram of the overall structure of a corrosion depth distribution extraction system based on three-dimensional point clouds. Figure 5 This application provides a schematic diagram of the structure of a terminal. Figure label: Module 1-1, Module 2-2, Module 3-3, Module 4-4, Module 5-5, Module 6-6, Module 7-7. Detailed Implementation

[0021] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0023] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments.

[0024] The corrosion depth distribution extraction method based on 3D point clouds is applied to a corrosion depth distribution extraction system based on 3D point clouds. Figure 1 A schematic diagram of the overall process for extracting corrosion depth distribution based on 3D point clouds is shown. Figure 1 As shown, it includes: S1. Obtain the three-dimensional point cloud data of the outer surface of the steel wire to be tested.

[0025] The process involves obtaining rusted steel wire samples with uncorroded reference sections, cleaning the wire surface with a neutral rust remover to remove loose rust, mud, and other adhering substances, followed by rinsing and drying to avoid damaging the true corrosion morphology. The dried wire is then fixed to a support fixture, and 3D point cloud data of the outer surface is collected using a 3D scanning device. The STL format file output from the scan is converted to a PLY format point cloud file, with the coordinate unit uniformly set to millimeters. The original point cloud is uniformly sampled, and if the point cloud is too dense, downsampling is performed to suppress noise while preserving the geometric details of the corrosion pits, ultimately obtaining a complete 3D point cloud set of the outer surface.

[0026] S2. The three-dimensional point cloud data is straightened by converting the three-dimensional point cloud of the bent steel wire to the straightened coordinate system, so that the center line of the straightened steel wire extends along the straight line direction, and the straightened coordinate system is obtained.

[0027] The process involves calculating the centroid and covariance matrix based on the acquired 3D point cloud, determining the initial axis and reference origin through eigenvalue decomposition, then coarsely slicing along the initial axis, projecting the point set within the slice onto a 2D plane, and obtaining the 3D cross-sectional center point through circle fitting and outlier removal, arranging them to form a discrete point set for the steel wire centerline; smoothing and arc length parameterization are performed on the centerline, generating local analysis segment positions according to the arc length step, and constructing a stable cross-sectional coordinate system through tangent vector normalization and parallel movement transmission; mapping the bent steel wire point cloud to this unified coordinate system, so that the centerline of the straightened steel wire extends along the straight line direction, completing the axis straightening and obtaining the straightened coordinate system.

[0028] S3. In the straightened coordinate system, with the center line as the reference axis, calculate the radial distance and circumferential angle of each surface point.

[0029] In the coordinate system after eliminating the curvature of the wire axis, the centerline of the wire lies in the x-axis direction, and for any point... Its distance from the center line is: In the formula, The distance from the point to the center of the steel wire. Let be the position of the point on the circumference of the cross section.

[0030] S4. Divide the point cloud into segments along the axis of the straightened coordinate system at preset intervals to obtain multiple local analysis segments.

[0031] Step S4 includes the following sub-steps: S401. Divide the straightened point cloud into multiple local analysis sections according to the preset axial spacing; S402. Eliminate local analysis sections with insufficient points.

[0032] In order to preserve the variation characteristics of the corrosion morphology of the steel wire surface along the length direction, and to provide an axial analysis unit for subsequent local anomaly point removal, reference radius establishment and two-dimensional heat map generation, the point cloud is segmented along the axial direction in the straightened coordinate system at a preset interval.

[0033] Furthermore, each segment corresponding to a local analysis section along the length of the steel wire can be considered as an approximate cross-sectional zone. Segments with insufficient data points can be skipped or merged to avoid excessive fluctuations in subsequent statistical results due to an insufficient number of local data points.

[0034] S5. In each of the local analysis sections, remove the abnormal points located outside the cross-sectional fitting circle and retain the true points inside the corrosion pits.

[0035] Step S5 includes the following sub-steps: S501. Calculate the external deviation of each surface point relative to the radius of the fitted circle of its local analysis segment.

[0036] In actual point cloud scanning, in addition to real surface points, some outliers may appear outside the corrosion pits. Examples include isolated flying points caused by scanning noise; spurious points on the outer surface due to registration errors; and extreme out-of-range points caused by uneven local sampling. These outliers will cause unrealistic spikes in the subsequent heatmap. For corrosion pits, the pit bottom point is precisely the most important information. Therefore, unlike the previous method of finding the center of a circle in coarse slices, points that are "smaller inwards" cannot be removed as outliers. Only those outliers on the outer surface that are much larger than the fitted reference radius should be removed, while all pit bottom points should be retained.

[0037] The program first calculates the fitted radius of each point relative to the reference. external bias : In the formula, The radius of the circle obtained by fitting a two-dimensional point set of a local analysis section cross section to a circle.

[0038] S502. For each of the local analysis segments, count the points located outside the cross-sectional fitting circle, and calculate the median of the external deviation as the overall level of external deviation.

[0039] After segmenting the point cloud and obtaining the deviation of the surface points within each segment relative to the fitted cross-section circle, it is necessary to further determine which points located outside the fitted cross-section circle represent actual surface undulations and which are abnormal outliers. This is because in actual scanning data, slight local surface protrusions, fitting errors, and normal measurement fluctuations can all cause some points to be slightly outside the fitted cross-section circle. Directly removing these points could easily lead to the accidental deletion of true surface information.

[0040] This step first involves calculating the overall outward deviation level for all points located outside the fitted circle of the cross-section. By calculating the median outward deviation level of this type of point, a benchmark can be provided for subsequent outlier identification.

[0041] The purpose of this step is not to directly delete points, but to first establish an overall distribution benchmark for external deviation points in the current segment, so that subsequent anomaly point identification has local adaptability, rather than using a fixed threshold for simple judgment.

[0042] S503. Calculate the absolute deviation of the outer deviation point from the median of the median, and use it as the fluctuation range.

[0043] After obtaining the overall out-skew level of the out-skew points, it is further necessary to determine the degree of dispersion of these points relative to the median out-skew level. This fluctuation range reflects the concentration or dispersion of the "normal out-skew points" in the current segment and is an important basis for subsequently establishing the out-of-point discrimination threshold.

[0044] Furthermore, the median absolute deviation is used as a representation of the fluctuation range. Compared with the ordinary mean or standard deviation, the median absolute deviation is less sensitive to a small number of extreme outliers, making it more suitable for processing scanned point cloud data with noise and local anomalies. This method can more stably reflect the normal fluctuation level of most outliers within the current segment, without being significantly skewed by a few extreme outliers.

[0045] S504. Set a threshold based on the overall level and fluctuation range of the external deviation to determine the actual point within the corrosion pit.

[0046] Step S504 includes the following sub-steps: S5041. Points located outside the cross-section fitting circle and whose outward deviation exceeds the threshold are identified as abnormal points and removed.

[0047] Once the overall external deviation level and fluctuation range of the external deviation point are obtained, anomaly judgment can be made for points located outside the cross-sectional fitting circle within the current segment.

[0048] This step only identifies anomalies at points outside the cross-sectional fitting circle; points inside the cross-sectional fitting circle are not subject to this rejection process. This one-sided anomaly identification method effectively removes external anomalies caused by scanning noise, registration errors, etc., while avoiding misclassifying real corrosion pits as outliers.

[0049] S5042. The points inside the cross-section fitting circle and the points outside the cross-section fitting circle but whose outward deviation does not exceed the threshold are collected to obtain the true points inside the corrosion pit.

[0050] S6. Determine the global reference radius based on the uncorroded segment.

[0051] Step S6 includes the following sub-steps: S601. Set the uncorroded segments at both ends of the point cloud as reference segments, perform fine slicing on the reference segments, fit a reference radius to each slice, and obtain a radius sequence.

[0052] S602. Use the median of the radius sequence as the global reference radius.

[0053] Specifically, after standardizing the length of the steel wire analysis segment, the uncorroded sections at both ends are set as reference segments. The program performs fine-slicing of the reference segments, fitting a reference radius to each slice, and then summing them into a radius sequence. Finally, median statistics are performed on these radii to obtain the global baseline radius. .

[0054] S7. For the retained true points within the corrosion pits, calculate the absolute corrosion depth based on the corresponding radial distance and the global reference radius, and output the corrosion depth distribution information.

[0055] The formula for calculating the absolute corrosion depth is as follows: In the formula, For the first The radial distance from each point to the reference center of the cross section The uncorroded reference radius, This represents the absolute corrosion depth.

[0056] If a point happens to be located near the uncorroded outer surface, then Approaching 0; if a point is located at the bottom of a corrosion pit, then Smaller The value will be even larger; if noise causes a point to be further out than the reference outer surface, the value will become negative, and in this case, it will be truncated to 0 to avoid an unreasonable "negative corrosion depth".

[0057] Furthermore, output corrosion depth distribution information, such as Figure 2 and Figure 3 As shown, Figure 2 A schematic diagram of corrosion depth distribution density is shown in a corrosion depth distribution extraction method based on three-dimensional point clouds. Figure 3 A two-dimensional thermodynamic diagram of corrosion depth is shown, illustrating a method for extracting corrosion depth distribution based on three-dimensional point clouds; including: S701. Calculate the absolute corrosion depth of all the real points in the retained corrosion pits, and generate and output the corrosion depth distribution probability density map.

[0058] The absolute corrosion depth of each sampling point was extracted, and a probability density distribution map of the absolute corrosion depth was generated. The horizontal axis represents the absolute corrosion depth, and the vertical axis represents the probability density, used to characterize the density of data occurrences within different corrosion depth ranges. This distribution result can be used to characterize the overall discrete characteristics and depth concentration range of corrosion damage, providing a data foundation for subsequent evaluation of steel wire corrosion and statistical modeling of corrosion parameters.

[0059] S702. Organize the statistical results of corrosion depth based on axial position and circumferential angle into a two-dimensional matrix, and generate and output a two-dimensional heat map of corrosion depth through color mapping.

[0060] The three-dimensional morphological data of the corroded section of the steel wire were unfolded along the axial direction and the circumference of the circular cross-section to construct a two-dimensional distribution map of corrosion depth. The horizontal axis represents the axial length of the corroded section; the vertical axis represents the circumferential angle of the cross-section; and the color scale on the right indicates the corrosion depth at the corresponding location. Different colors in the map represent the spatial variation characteristics of corrosion depth, with a color change from dark blue to red indicating a gradual increase in corrosion degree. This unfolded map visually reflects the non-uniform distribution of corrosion damage along the axial and circumferential directions of the steel wire, thus providing a basis for corrosion pit identification, localization of the deepest corrosion area, and subsequent quantitative analysis of corrosion morphology parameters.

[0061] First, the program summarizes and statistically analyzes the absolute corrosion depth of all the actual points within the corrosion pits retained in the analysis segment, and outputs a probability density map of the corrosion depth distribution. This map reflects the overall distribution of corrosion depth of all surface points, and can be used to determine the main range of corrosion depth on the steel wire surface, whether deep corrosion points account for a high proportion, and whether the overall corrosion degree is relatively shallow or deep.

[0062] Secondly, the program organizes the statistical results of corrosion depth in both axial and circumferential directions into a two-dimensional matrix, and outputs a two-dimensional corrosion depth heatmap using color mapping. This heatmap is used to display the spatial distribution characteristics of corrosion depth on the steel wire surface in the length and circumferential directions, and can intuitively identify areas of concentrated corrosion, the distribution range of pitting corrosion, and its degree of non-uniformity.

[0063] This example provides a method for extracting corrosion depth distribution based on 3D point clouds. First, 3D point cloud data of the outer surface of the steel wire to be tested is acquired and straightened along its axis. The bent steel wire is then transformed to a straightened coordinate system, and the radial distance and circumferential angle of each surface point are calculated using the straightened centerline as the reference axis. Next, the point cloud is segmented along the axial direction at preset intervals. In each segment, a threshold is set based on the median of the external offset and the absolute deviation of the median. Outliers located outside the fitted circle of the cross-section are removed, and true points within the corrosion pits are retained. Then, the uncorroded sections at both ends are set as reference sections. A radius sequence is obtained through fine slicing and fitting, and the median is taken as the global reference radius. Finally, for the retained true points, the absolute corrosion depth is calculated based on the difference between the radial distance and the global reference radius, and a corrosion depth distribution probability density map and a 2D heat map are output. Compared with existing technologies, this invention has the following advantages: 1. By calculating the external deviation of surface points relative to the radius of the fitted circle in each analysis segment, and setting an adaptive threshold based on the median and median absolute deviation of the external deviation, only outlier points located outside the fitted circle of the cross section and whose deviation exceeds the threshold are removed, while the corrosion pit bottom points inside the fitted circle of the cross section are completely retained. This solves the problem of interference from scanning noise, registration error and external flying points on corrosion depth statistics, and significantly improves the data purity and result reliability of corrosion depth calculation.

[0064] 2. By setting the uncorroded sections at both ends of the steel wire as reference sections, finely slicing the reference sections and fitting the radii of each slice, and then using the median of the radius sequence as the global reference radius, the problem of single-point or single-section reference radii being easily affected by local morphological fluctuations is avoided, making the reference radius statistically robust, thereby ensuring the accuracy and consistency of the calculation of the absolute corrosion depth at each point within the corroded section.

[0065] 3. By outputting the probability density map of corrosion depth distribution and the two-dimensional heat map, the absolute corrosion depth calculated point by point is visualized in multiple dimensions along the depth range, axial position and circumferential angle. This not only reflects the overall statistical distribution characteristics of corrosion depth intuitively, but also accurately identifies the spatial non-uniformity of corrosion along the length and circumference of the steel wire, providing reliable data support for the evaluation of corrosion degree of bridge cable steel wire and the location of local pitting corrosion.

[0066] For those consistent with the above, please refer to Figure 4 , Figure 4This application provides a schematic diagram of a corrosion depth distribution extraction system based on three-dimensional point clouds, as illustrated in this embodiment. Figure 4 As shown, the system includes: The first module 1 is used to acquire three-dimensional point cloud data of the outer surface of the steel wire to be tested.

[0067] The second module 2 is used to straighten the axis of the three-dimensional point cloud data, transforming the three-dimensional point cloud of the bent steel wire into the straightened coordinate system, so that the center line of the straightened steel wire extends along the straight line direction, and the straightened coordinate system is obtained.

[0068] The third module 3 is used to calculate the radial distance and circumferential angle of each surface point in the straightened coordinate system, with the center line as the reference axis.

[0069] Module 4 is used to segment the point cloud along the axis of the straightened coordinate system at a preset interval to obtain multiple local analysis segments.

[0070] The fifth module 5 is used to remove abnormal points located outside the cross-sectional fitting circle in each of the local analysis sections, and retain the true points inside the corrosion pits.

[0071] Module 6 is used to determine the global baseline radius based on the uncorroded segment.

[0072] Module 7 is used to calculate the absolute corrosion depth for the real points within the retained corrosion pits based on the corresponding radial distance and the global reference radius, and output corrosion depth distribution information.

[0073] For examples consistent with the above embodiments, please refer to... Figure 5 , Figure 5 A schematic diagram of a terminal structure provided in an embodiment of this application is shown in the figure. It includes a processor, an input device, an output device, and a memory. The processor, input device, output device, and memory are interconnected. The memory is used to store a computer program, which includes program instructions. The processor is configured to call the program instructions. The program includes instructions for performing the following steps. Acquire three-dimensional point cloud data of the outer surface of the steel wire to be tested; The three-dimensional point cloud data is straightened by axis straightening, and the three-dimensional point cloud of the bent steel wire is transformed into the straightened coordinate system, so that the center line of the straightened steel wire extends along the straight line direction, and the straightened coordinate system is obtained. In the straightened coordinate system, with the center line as the reference axis, calculate the radial distance and circumferential angle of each surface point; The point cloud is segmented along the axis of the straightened coordinate system at a preset interval to obtain multiple local analysis segments; In each of the aforementioned local analysis sections, outlier points located outside the cross-sectional fitting circle are removed, while true points within the corrosion pits are retained. Determine the global baseline radius based on the uncorroded segment; For the actual points within the retained corrosion pits, the absolute corrosion depth is calculated based on the corresponding radial distance and the global reference radius, and the corrosion depth distribution information is output.

[0074] The above mainly describes the solutions of the embodiments of this application from the perspective of the method execution process. It is understood that, in order to achieve the above functions, the terminal includes the corresponding hardware structure and / or software modules for executing each function. Those skilled in the art should readily recognize that, in conjunction with the units and algorithm steps of the various examples described in the embodiments provided herein, this application can be implemented in hardware or a combination of hardware and computer software. Whether a function is executed in hardware or by computer software driving hardware depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0075] This application embodiment can divide the terminal into functional units according to the above method example. For example, each function can be divided into a separate functional unit, or two or more functions can be integrated into one processing unit. The integrated unit can be implemented in hardware or as a software functional unit. It should be noted that the unit division in this application embodiment is illustrative and only represents one logical functional division. In actual implementation, there may be other division methods.

[0076] This application also provides a computer storage medium storing a computer program for electronic data interchange, which causes a computer to perform some or all of the steps of any of the three-dimensional point cloud-based corrosion depth distribution extraction methods described in the above method embodiments.

[0077] This application also provides a computer program product, which includes a non-transitory computer-readable storage medium storing a computer program that causes a computer to perform some or all of the steps of any of the three-dimensional point cloud-based erosion depth distribution extraction methods described in the above method embodiments.

[0078] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to this application. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to this application.

[0079] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0080] In the several embodiments provided in this application, it should be understood that the disclosed apparatus can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, 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 or other forms.

[0081] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0082] Furthermore, the functional units in the various embodiments of the application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software program module.

[0083] If the integrated unit is implemented as a software program module and sold or used as an independent product, it can be stored in a computer-readable storage device (CMD). Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a memory and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned memory includes various media capable of storing program code, such as USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks.

[0084] Those skilled in the art will understand that all or part of the steps in the various methods of the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage device, which may include: a flash drive, a read-only memory, a random access memory, a magnetic disk, or an optical disk, etc.

[0085] The embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for extracting corrosion depth distribution based on three-dimensional point clouds, characterized in that, include: Acquire three-dimensional point cloud data of the outer surface of the steel wire under test with an uncorroded reference section; The three-dimensional point cloud data is straightened by axis straightening, and the three-dimensional point cloud of the bent steel wire is transformed into the straightened coordinate system, so that the center line of the straightened steel wire extends along the straight line direction, and the straightened coordinate system is obtained. In the straightened coordinate system, with the center line as the reference axis, calculate the radial distance and circumferential angle of each surface point; The point cloud is segmented along the axis of the straightened coordinate system at a preset interval to obtain multiple local analysis segments; In each of the aforementioned local analysis sections, outlier points located outside the cross-sectional fitting circle are removed, while true points within the corrosion pits are retained. Determine the global baseline radius based on the uncorroded segment; For the actual points within the retained corrosion pits, the absolute corrosion depth is calculated based on the corresponding radial distance and the global reference radius, and the corrosion depth distribution information is output. The process of straightening the axis of the three-dimensional point cloud data, transforming the three-dimensional point cloud of the bent steel wire into a straightened coordinate system, so that the centerline of the straightened steel wire extends along a straight direction, and obtaining the straightened coordinate system, includes: The centroid and covariance matrix are calculated based on the acquired 3D point cloud set. The initial axis and reference origin are determined through eigenvalue decomposition. Then, coarse slicing is performed along the initial axis. The point set within the slice is projected onto a 2D plane and the center point of the 3D section is obtained through circle fitting and outlier removal. These points are arranged to form a discrete point set of the steel wire centerline. The centerline is smoothed and parameterized with arc length. Local analysis segment positions are generated according to the arc length step. A stable section coordinate system is constructed through tangent vector normalization and parallel movement transmission. The point cloud of the bent steel wire is mapped to this coordinate system so that the centerline of the straightened steel wire extends along the straight line direction, completing the straightening of the axis and obtaining the straightened coordinate system.

2. The method for extracting corrosion depth distribution based on three-dimensional point clouds according to claim 1, characterized in that, The point cloud is segmented along the axis of the straightened coordinate system at preset intervals to obtain multiple local analysis segments, including: The straightened point cloud is divided into multiple local analysis sections according to the preset axial spacing; Remove local analysis sections with insufficient data points.

3. The method for extracting corrosion depth distribution based on three-dimensional point clouds according to claim 1, characterized in that, In each of the aforementioned local analysis sections, outlier points located outside the fitted circle of the cross-section are removed, while true points within the corrosion pits are retained. This includes: Calculate the outward deviation of each surface point relative to the radius of the fitted circle of its local analysis segment; For each of the local analysis segments, the points located outside the cross-sectional fitting circle are counted, and the median of the external deviation is calculated as the overall level of external deviation. Calculate the absolute deviation of the out-of-range point from the median, and use it as the range of fluctuation; The threshold is set based on the overall level and fluctuation range of the external deviation to determine the actual points within the corrosion pit.

4. The corrosion depth distribution extraction method based on three-dimensional point clouds according to claim 3, characterized in that, The step of setting a threshold based on the overall level and fluctuation range of the external deviation to determine the true points within the corrosion pit includes: Points located outside the cross-section fitting circle and whose outward deviation exceeds the threshold are identified as outliers and removed. The points inside the cross-sectional fitting circle and the points outside the cross-sectional fitting circle but whose outward deviation does not exceed the threshold are collected to obtain the true points inside the corrosion pit.

5. The method for extracting corrosion depth distribution based on three-dimensional point clouds according to claim 1, characterized in that, The determination of the global reference radius based on the uncorroded segment includes: The uneroded segments at both ends of the point cloud are set as reference segments. The reference segments are finely sliced, and a reference radius is fitted to each slice to obtain a radius sequence. The median of the radius sequence is used as the global baseline radius.

6. The method for extracting corrosion depth distribution based on three-dimensional point clouds according to claim 1, characterized in that, In the calculation of the absolute corrosion depth for the retained actual points within the corrosion pits, based on the corresponding radial distance and the global reference radius, the formula for calculating the absolute corrosion depth is as follows: In the formula, For the first The radial distance from each point to the reference center of the cross section The uncorroded reference radius, This represents the absolute corrosion depth.

7. The method for extracting corrosion depth distribution based on three-dimensional point clouds according to claim 1, characterized in that, The output corrosion depth distribution information includes: The absolute corrosion depth of all the real points within the retained corrosion pits is statistically analyzed, and a corrosion depth distribution probability density map is generated and output. The statistical results of corrosion depth based on axial position and circumferential angle are organized into a two-dimensional matrix, and a two-dimensional heat map of corrosion depth is generated and output through color mapping.

8. A corrosion depth distribution extraction system based on three-dimensional point clouds, characterized in that, include: The first module is used to acquire three-dimensional point cloud data of the outer surface of the steel wire under test with an uncorroded reference section. The second module is used to straighten the axis of the three-dimensional point cloud data, transforming the three-dimensional point cloud of the bent steel wire into the straightened coordinate system, so that the center line of the straightened steel wire extends along the straight line direction, and the straightened coordinate system is obtained. The third module is used to calculate the radial distance and circumferential angle of each surface point in the straightened coordinate system, with the center line as the reference axis; The fourth module is used to segment the point cloud along the axis of the straightened coordinate system at preset intervals to obtain multiple local analysis segments; The fifth module is used to remove abnormal points located outside the cross-sectional fitting circle in each of the local analysis sections, and retain the true points inside the corrosion pits. The sixth module is used to determine the global baseline radius based on the uncorroded segment; The seventh module is used to calculate the absolute corrosion depth for the real points within the retained corrosion pits based on the corresponding radial distance and the global reference radius, and output corrosion depth distribution information. The process of straightening the axis of the three-dimensional point cloud data, transforming the three-dimensional point cloud of the bent steel wire into a straightened coordinate system, so that the centerline of the straightened steel wire extends along a straight direction, and obtaining the straightened coordinate system, includes: The centroid and covariance matrix are calculated based on the acquired 3D point cloud set. The initial axis and reference origin are determined through eigenvalue decomposition. Then, coarse slicing is performed along the initial axis. The point set within the slice is projected onto a 2D plane and the center point of the 3D section is obtained through circle fitting and outlier removal. These points are arranged to form a discrete point set of the steel wire centerline. The centerline is smoothed and parameterized with arc length. Local analysis segment positions are generated according to the arc length step. A stable section coordinate system is constructed through tangent vector normalization and parallel movement transmission. The point cloud of the bent steel wire is mapped to this coordinate system so that the centerline of the straightened steel wire extends along the straight line direction, completing the straightening of the axis and obtaining the straightened coordinate system.

9. A terminal, characterized in that, The device includes a processor, an input device, an output device, and a memory, which are interconnected. The memory stores a computer program, which includes program instructions. The processor is configured to invoke the program instructions to execute the corrosion depth distribution extraction method based on three-dimensional point clouds as described in any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, the computer program including program instructions, which, when executed by a processor, cause the processor to perform the corrosion depth distribution extraction method based on any one of claims 1-7.

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