A method for corrosion region inversion of a drag cable based on spontaneous magnetic flux leakage energy and physical prior

Abstract

The present application relates to the technical field of bridge cable nondestructive testing, and particularly relates to a cable corrosion area inversion method based on spontaneous magnetic leakage energy and physical priori, comprising the following steps: S1: obtaining tangential magnetic induction intensity components and normal magnetic induction intensity components at each axial sampling position and each circumferential sampling angle of the cable; S2: constructing a two-dimensional original spontaneous magnetic leakage matrix with the axial position and the circumferential angle as coordinates; S3: constructing an interpolated magnetic signal matrix under a high-resolution circumferential angle grid; S4: constructing a smooth envelope energy field; S5: constructing a physical priori domain of the corrosion area; S6: constructing an edge stop function; S7: generating a converged level set contour; S8: performing a closed operation and hole filling on the converged level set contour to obtain an inversion contour of the cable corrosion area, and outputting corresponding corrosion area related parameters. The present application can realize automatic positioning, boundary extraction and size quantification of the corrosion area without external excitation.

Description

Technical Field

[0001] This invention relates to the field of non-destructive testing technology for bridge suspension cables, specifically to a method for inverting corrosion zones in suspension cables based on spontaneous leakage magnetic energy and physical priors. Background Technology

[0002] Cable-stayed bridges, suspension bridges, and tied-arch bridges are widely used in cable-stayed bridges and are key components of the structural force transmission system. Due to the long-term exposure of the cable body to vehicle loads, temperature cycling, humid and hot environments, chloride corrosion, and industrial atmospheres, problems such as sheath aging and cracking, water seepage in the anchorage zone, and internal crevice corrosion can easily lead to hidden corrosion of the steel wires within the cable. Corrosion reduces the effective load-bearing cross-section of the steel wires, degrades the material's mechanical properties, and further reduces the safety reserve of the cable.

[0003] Existing technologies for detecting cable ties include acoustic emission, guided wave, excitation magnetic flux leakage, machine vision, and spontaneous magnetic flux leakage. Acoustic emission and guided wave methods have high sensitivity to specific damage, but are easily affected by environmental noise, coupling conditions, and scattering from multi-filament structures. Machine vision mainly identifies superficial defects in the sheath and has difficulty directly obtaining the extent of internal corrosion. Excitation magnetic flux leakage methods usually require external excitation equipment, making on-site operation complex. Spontaneous magnetic flux leakage methods utilize the magnetic flux leakage anomalies formed by the Earth's magnetic field and the component's own magnetization state for detection, offering advantages such as no need for external excitation, lightweight equipment, and suitability for on-site inspections.

[0004] However, existing methods for identifying spontaneous magnetic flux leakage corrosion typically rely on one-dimensional peak values, peak-to-valley spacing, empirical thresholds, or simple two-dimensional thermograms for judgment. For suspension cables, the corrosion region exhibits non-uniformity in the axial, circumferential, and depth directions. x The component often manifests as localized clustering near the corrosion center, B z The components often exhibit a peak-valley structure near the corrosion boundary. Using only a single component or a fixed threshold is susceptible to fluctuations in the background magnetic field, sensor zero drift, noise speckle, changes in corrosion geometry, and the superposition of multiple corrosion points, leading to unstable boundary extraction of the corrosion region. While the ordinary level set method can extract continuous boundaries, its results are highly dependent on the initialization position and image gradient. Without considering the physical laws of spontaneous magnetic leakage signals, the contour can easily diffuse into the background region or stop prematurely inside the corrosion region. Thresholding connected component methods are relatively simple to calculate, but the threshold selection lacks stable adaptability to different cable diameters, corrosion locations, and corrosion degrees. Region expansion methods based on particle swarm optimization or empirical bounding boxes are prone to oversegmentation or undersegmentation.

[0005] Therefore, how to transform the deterministic physical laws in spontaneous leakage magnetic field signals into boundary extraction priors and couple them with image segmentation algorithms to achieve automatic, stable, and quantifiable inversion of the corrosion region of the suspension cable is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the shortcomings of the existing technologies, the technical problem to be solved by this invention is: how to provide a method for inverting corrosion regions of suspension cables based on spontaneous leakage magnetic energy and physical priors, utilizing the energy distribution of spontaneous leakage magnetic signals and the physical laws of tangential and normal magnetic induction intensity components to achieve automatic positioning, boundary extraction, and size quantization of corrosion regions without the need for external excitation.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A method for inverting corrosion zones in suspension cables based on spontaneous leakage magnetic energy and physical priors includes:

[0009] S1: Obtain the tangential and normal magnetic induction intensity components at each axial sampling position and each circumferential sampling angle of the suspension cable;

[0010] S2: After data correction of each tangential magnetic flux density component and each normal magnetic flux density component, and data matching of axial sampling position and circumferential sampling angle, matrix processing is performed to obtain a two-dimensional original spontaneous leakage magnetic flux matrix with axial position and circumferential angle as coordinates.

[0011] S3: Periodically interpolate and extend the original two-dimensional spontaneous leakage magnetic matrix along the circumferential direction to obtain the interpolated magnetic signal matrix under the high-resolution circumferential corner grid.

[0012] S4: Windowing and Hilbert transform the interpolated normal magnetic flux density component in the interpolated magnetic signal matrix along the axial direction, calculate the envelope energy field of the normal magnetic flux density component, and obtain the smoothed envelope energy field through smoothing.

[0013] S5: Determine the corrosion center based on the local extrema of the tangential magnetic induction intensity component, determine the corrosion axial range based on the peak and valley positions of the normal magnetic induction intensity component, determine the corrosion circumferential range based on the circumferential data distribution at the corrosion center, and construct the physical prior domain of the corrosion region.

[0014] S6: Morphologically expand the physical prior domain of the eroded region to construct a local zone of interest, and construct a weighted stopping function based on the gradient of the smooth envelope energy field;

[0015] S7: Using the expanded physical prior domain as the initial profile of the level set, the weighted stopping function is embedded into the level set evolution equation to make the level set profile converge at the erosion boundary of the smooth envelope energy field, thus obtaining the converged level set profile.

[0016] S8: Perform closing operations and hole filling on the converged horizontal set contour to obtain the inverted contour of the cable erosion area and output the corresponding erosion area related parameters.

[0017] Preferably, in step S1, a multi-channel magnetic sensor array arranged circumferentially along the cable is used to scan along the axial direction of the cable to obtain the tangential magnetic induction intensity components and normal magnetic induction intensity components at each axial sampling position and each circumferential sampling angle of the cable.

[0018] The multi-channel magnetic sensing array includes a closed arrangement along the circumference of the suspension cable. The third triaxial magnetic sensor, of which the first Circumferential sampling angle of a triaxial magnetic sensor Represented as:

[0019] ;

[0020] In the formula: This is the initial arrangement angle.

[0021] Preferably, in step S2, the formula for the two-dimensional original spontaneous leakage magnetic flux matrix is ​​expressed as:

[0022] ;

[0023] ;

[0024] In the formula: , These are the two-dimensional original spontaneous leakage magnetic flux matrices of the tangential and normal magnetic flux intensity components, respectively; coordinates The tangential magnetic induction intensity component at the location; coordinates The normal magnetic induction intensity component at that location; For the first One axial position; For the first One circumferential angle; This represents the number of axial sampling points; This represents the number of circumferential triaxial magnetic sensors.

[0025] Preferably, step S3 specifically includes the following processing steps:

[0026] S301: Constructing a high-resolution angular mesh , To set the angle increment;

[0027] S302: For the tangential magnetic flux density component in the two-dimensional original spontaneous leakage magnetic matrix and normal magnetic induction intensity component Sampling positions along each axis in a high-resolution angular grid. Periodic Akima cubic spline interpolation was applied to the circumferential data to obtain the interpolated tangential magnetic flux density components. and normal magnetic induction intensity component ;

[0028] S303: Based on the interpolated tangential magnetic flux density component and normal magnetic induction intensity component An interpolated magnetic signal matrix for the tangential and normal magnetic induction intensity components under a high-resolution circumferential grid is constructed.

[0029] Preferably, step S4 specifically includes the following processing steps:

[0030] S401: Interpolated normal magnetic flux density component in the interpolated magnetic signal matrix Apply Hanning window weighting;

[0031] The weighting coefficients of the Hanning window satisfy the following formula:

[0032] ;

[0033] In the formula: For the first Hanning window weighting coefficients for each axial sampling point; This represents the number of axial sampling points;

[0034] S402: Sampling position along the axial direction For the weighted normal magnetic induction component Perform a Hilbert transform to obtain the component of the normal magnetic induction intensity. Orthogonal normal magnetic induction components ;

[0035] S403: Based on each normal magnetic induction intensity component and the corresponding normal magnetic induction intensity component Calculate the envelope energy field;

[0036] The formula for calculating the envelope energy field is:

[0037] ;

[0038] In the formula: For the envelope energy field in coordinates The value at that location;

[0039] S404: Perform anisotropic two-dimensional Gaussian smoothing on the envelope energy field to obtain a smoothed envelope energy field.

[0040] Preferably, in step S404, the formula for the anisotropic two-dimensional Gaussian smoothed Gaussian convolution kernel is:

[0041] ;

[0042] In the formula: Use a Gaussian convolution kernel; For axially smooth dimensions; For circumferential smoothing; , These are the axial and circumferential distance variables, respectively.

[0043] Preferably, step S5 specifically includes the following processing steps:

[0044] S501: Search for the local extrema of the tangential magnetic flux density component in the two-dimensional original spontaneous leakage magnetic flux matrix or interpolated magnetic signal matrix to determine the corrosion center. ;

[0045] S502: Search for the maximum and minimum values ​​of the normal magnetic induction intensity component in the two-dimensional original spontaneous leakage magnetic flux matrix or interpolated magnetic signal matrix, and use the difference in axial coordinates corresponding to the maximum and minimum values ​​as the corrosion axial range.

[0046] S503: Cross section at the corrosion center Extract the tangential magnetic induction intensity component curve or smooth envelope energy field curve, and determine the corrosion circumferential boundary by background mean and standard deviation, maximum inter-class variance or local adaptive threshold;

[0047] S504: Based on corrosion center coordinates The axial range and circumferential boundary of corrosion are used to establish an elliptical physical prior domain for the corrosion region.

[0048] Preferably, in step S504, the formula for calculating the elliptical physical prior domain of the corrosion region is:

[0049] ;

[0050] In the formula: The elliptic physical prior domain is the region of corrosion. For any coordinate point on the image plane; The coordinates of the corrosion center; The length of the semi-axis of the elliptic physical prior domain in the axial direction is determined based on the axial range of corrosion. The length of the semi-axis of the elliptic physical prior domain in the circumferential direction is determined based on the circumferential boundary of the corrosion.

[0051] Preferably, step S6 specifically includes the following processing steps:

[0052] S601: Elliptic physical prior domain for the corroded region Slight morphological dilation is performed using structuring elements with a radius of 1 to 3 pixels, and an elliptical physical prior domain is used. The neighborhood zone is defined as the region of interest (ROI).

[0053] S602: Constructing indicator functions based on local zones of interest (ROIs) ;

[0054] Indicator Function The calculation formula is:

[0055] ;

[0056] In the formula: For any coordinate point on the image plane;

[0057] S603: Construct an edge stopping function by smoothing the gradient magnitude of the envelope energy field;

[0058] ;

[0059] In the formula: This is the edge stopping function; To smooth the gradient magnitude of the envelope energy field;

[0060] S604: Indicator function and edge stopping function Combined to form a weighted stopping function for the evolution of the level set;

[0061] The formula is expressed as:

[0062] ;

[0063] In the formula: This is a weighted stopping function; For indicator functions; Evolution weights within the region of interest (ROI); The evolution weights are those outside the region of interest (ROI).

[0064] Preferably, step S7 specifically includes the following processing steps:

[0065] S701: The morphologically expanded elliptical physical prior domain As the initial level set outline;

[0066] S702: Solve the level set evolution equation using level set functions to update the level set profile;

[0067] The formula for calculating the level set evolution equation is:

[0068] ;

[0069] ;

[0070] In the formula: For level set functions, For any coordinate point on the image plane, The number of iterations (evolution time); This is a weighted stopping function; For curvature term; For the convection term coefficient; For gradient operators;

[0071] S703: Repeat step S702 to iteratively solve the level set contour until the contour area change is less than the threshold or the maximum number of iterations is reached, and the converged level set contour is obtained.

[0072] The inversion method for corrosion regions of suspension cables based on spontaneous leakage magnetic energy and physical priors in this invention has the following advantages compared with existing technologies:

[0073] (1) Based on the tangential magnetic induction intensity component and the normal magnetic induction intensity component of the spontaneous leakage magnetic signal, this invention does not require external excitation equipment, which can reduce the weight of the actual bridge detection system and the complexity of on-site deployment. It is suitable for cable climbing robots, manual assisted inspection or mobile detection platforms.

[0074] (2) The present invention transforms the peak-valley bipolar response of the normal magnetic induction intensity component into a Hilbert envelope energy field that is more robust to sign and phase, avoiding positive and negative splits or local cancellation of the same corrosion defect in the pseudo-color image, which is beneficial to enhancing the stability and discernibility of corrosion energy clusters.

[0075] (3) The present invention uses periodic interpolation and anisotropic Gaussian smoothing to improve the circumferential resolution and two-dimensional signal-to-noise ratio while preserving the geometric features such as the axial length, circumferential width and center position of the eroded region.

[0076] (4) This invention uses the extreme values ​​of the tangential magnetic induction intensity component to determine the corrosion center, the peaks and valleys of the normal magnetic induction intensity component to determine the axial boundary, and the adaptive threshold to determine the circumferential range. Based on the physical laws of magnetic signals, it constructs the initial contour of the horizontal set and the local region of interest (ROI), which can reduce the sensitivity of the ordinary horizontal set method to the initial position and background noise, and avoid the contour from deviating from the target area.

[0077] (5) By embedding the local zone of interest into the stopping function and the evolution equation of the level set, the present invention enables the level set contour to converge smoothly and continuously along the corrosion boundary and suppress diffusion into the non-corrosion background area, thereby improving the stability of corrosion contour extraction and size quantization.

[0078] (6) The parameters related to the corrosion area output by this invention include the location of the corrosion center, the start and end coordinates of the corrosion axis, the length of the corrosion axis, the start and end angles of the corrosion circumferential direction, the range of the corrosion circumferential angle, the circumferential width calculated according to the cable radius, and the corrosion area on the unfolded coordinate plane. These parameters can be directly used as input parameters for subsequent corrosion degree prediction, cross-sectional damage modeling, and residual bearing capacity evaluation, which is conducive to realizing the integrated analysis between the cable detection signal, corrosion state, and structural performance. Attached Figure Description

[0079] To make the objectives, technical solutions, and advantages of the invention clearer, the invention will now be described in further detail with reference to the accompanying drawings, wherein:

[0080] Figure 1 This is a logic block diagram of the inversion method for corrosion regions of suspension cables based on spontaneous leakage magnetic energy and physical priors.

[0081] Figure 2 This is a logic block diagram of a multi-channel magnetic sensor array. Detailed Implementation

[0082] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but only to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0083] The following detailed explanation illustrates the specific implementation methods:

[0084] Example:

[0085] This embodiment discloses a method for inverting corrosion regions of suspension cables based on spontaneous leakage magnetic energy and physical priors.

[0086] like Figure 1 As shown, the inversion method for corrosion regions of suspension cables based on spontaneous leakage magnetic energy and physical priors includes:

[0087] S1: Obtain the tangential and normal magnetic induction intensity components at each axial sampling position and each circumferential sampling angle of the suspension cable;

[0088] S2: After data correction of each tangential magnetic flux density component and each normal magnetic flux density component, and data matching of axial sampling position and circumferential sampling angle, matrix processing is performed to obtain a two-dimensional original spontaneous leakage magnetic flux matrix with axial position and circumferential angle as coordinates.

[0089] S3: Periodically interpolate and extend the original two-dimensional spontaneous leakage magnetic matrix along the circumferential direction to obtain the interpolated magnetic signal matrix under the high-resolution circumferential corner grid.

[0090] S4: Windowing and Hilbert transform the interpolated normal magnetic flux density component in the interpolated magnetic signal matrix along the axial direction, calculate the envelope energy field of the normal magnetic flux density component, and obtain the smoothed envelope energy field through smoothing.

[0091] S5: Determine the corrosion center based on the local extrema of the tangential magnetic induction intensity component, determine the corrosion axial range based on the peak and valley positions of the normal magnetic induction intensity component, determine the corrosion circumferential range based on the circumferential data distribution at the corrosion center, and construct the physical prior domain of the corrosion region.

[0092] S6: Morphologically expand the physical prior domain of the eroded region to construct a local zone of interest, and construct a weighted stopping function based on the gradient of the smooth envelope energy field;

[0093] S7: Using the expanded physical prior domain as the initial profile of the level set, the weighted stopping function is embedded into the level set evolution equation to make the level set profile converge at the erosion boundary of the smooth envelope energy field, thus obtaining the converged level set profile.

[0094] S8: Perform closing operations and hole filling on the converged horizontal set contour to obtain the inverted contour of the cable erosion area and output the corresponding erosion area related parameters.

[0095] To better illustrate the technical solution of the present invention, this embodiment will be described in more detail through the following parts.

[0096] I. Multi-channel magnetic sensor array

[0097] like Figure 2 As shown, a multi-channel magnetic sensor array arranged circumferentially along the suspension cable is used to scan along the axial direction of the suspension cable to obtain the sampling positions of each axial direction of the suspension cable. and each circumferential sampling angle Tangential magnetic flux density component at the location and normal magnetic induction intensity component .

[0098] The number of circumferential sensors is determined based on the diameter of the cable to be tested. and will Three triaxial magnetic sensors are arranged in a closed loop along the circumference of the cable. The sensor array moves at a constant speed or in segments along the cable axis with the cable-climbing robot or other axial moving mechanism, collecting the position data for each axis. Tangential magnetic flux density component at the location and normal magnetic induction intensity component .

[0099] No. Circumferential sampling angle of a triaxial magnetic sensor Represented as:

[0100] ;

[0101] In the formula: This is the initial arrangement angle.

[0102] II. Two-dimensional original spontaneous leakage magnetic flux matrix

[0103] In the specific implementation process, data correction is performed on each tangential magnetic induction intensity component and each normal magnetic induction intensity component, including zero drift correction, scale consistency correction, and outlier removal. Outliers can be identified based on the local median deviation of adjacent axial and circumferential positions; when a sampled value deviates from the local median by more than a set threshold, it is replaced by neighborhood interpolation.

[0104] Specifically, the formula for the two-dimensional original spontaneous leakage magnetic flux matrix is ​​as follows:

[0105] ;

[0106] ;

[0107] In the formula: , These are the two-dimensional original spontaneous leakage magnetic flux matrices of the tangential and normal magnetic flux intensity components, respectively; coordinates The tangential magnetic induction intensity component at the location; coordinates The normal magnetic induction intensity component at that location; For the first One axial position; For the first One circumferential angle; This represents the number of axial sampling points; This represents the number of circumferential triaxial magnetic sensors.

[0108] III. Interpolation Magnetic Signal Matrix

[0109] In practice, due to the limited number of circumferential sensors, the circumferential resolution is insufficient when directly using the original matrix imaging.

[0110] Specifically, the processing steps for constructing the interpolated magnetic signal matrix include:

[0111] S301: Constructing a high-resolution angular mesh , To set the angle increment;

[0112] S302: For the tangential magnetic flux density component in the two-dimensional original spontaneous leakage magnetic matrix and normal magnetic induction intensity component Sampling positions along each axis in a high-resolution angular grid. Periodic Akima cubic spline interpolation was applied to the circumferential data to obtain the interpolated tangential magnetic flux density components. and normal magnetic induction intensity component ;

[0113] The interpolated tangential and normal magnetic flux density components satisfy the following formula:

[0114] ;

[0115] In the formula: This represents the tangential magnetic flux density component or the normal magnetic flux density component. , These are the magnetic flux density components at circumferential angles of 0° and 360°, respectively; is the first derivative of the magnetic flux density component along the circumferential direction;

[0116] S303: Based on the interpolated tangential magnetic flux density component and normal magnetic induction intensity component An interpolated magnetic signal matrix for the tangential and normal magnetic induction intensity components under a high-resolution circumferential grid is constructed.

[0117] IV. Envelope Energy Field

[0118] In the specific implementation process, the steps for constructing the envelope energy field include:

[0119] S401: To reduce the truncation effect at both ends of the axial scan sequence, the interpolated normal magnetic induction intensity component in the interpolated magnetic signal matrix is... Apply Hanning window weighting;

[0120] The weighting coefficients of the Hanning window satisfy the following formula:

[0121] ;

[0122] In the formula: For the first Hanning window weighting coefficients for each axial sampling point; This represents the number of axial sampling points;

[0123] S402: Sampling position along the axial direction For the weighted normal magnetic induction component Perform a Hilbert transform to obtain the component of the normal magnetic induction intensity. Orthogonal normal magnetic induction components ;

[0124] S403: Based on each normal magnetic induction intensity component and the corresponding normal magnetic induction intensity component Calculate the envelope energy field;

[0125] The formula for calculating the envelope energy field is:

[0126] ;

[0127] In the formula: For the envelope energy field in coordinates The value at that location; the envelope energy field will include the normal magnetic induction intensity component. The positive and negative peak and valley responses are unified into energy intensity responses, which is beneficial to highlight the local energy concentration in the corrosion area.

[0128] S404: Perform anisotropic two-dimensional Gaussian smoothing on the envelope energy field to obtain a smoothed envelope energy field.

[0129] Specifically, the formula for anisotropic two-dimensional Gaussian smoothed Gaussian convolution kernel is:

[0130] ;

[0131] In the formula: Use a Gaussian convolution kernel; For axially smooth dimensions; For circumferential smoothing; , These represent the axial and circumferential distance variables, respectively. For corrosion defects with longer axial lengths, σx can be appropriately increased to avoid the low-energy valley at the envelope center being misjudged as a multi-defect interval; for multi-point corrosion defects with shorter circumferential spacing, σθ can be appropriately decreased or the number of sensors can be increased to improve peak resolution.

[0132] V. Physical Prior Domain

[0133] In the specific implementation process, the steps for constructing the physical prior domain include:

[0134] S501: Search for the local extrema (or absolute extrema) of the tangential magnetic flux density component in the two-dimensional original spontaneous leakage magnetic flux matrix or interpolated magnetic signal matrix to determine the corrosion center. ; Utilizing the tangential magnetic induction intensity component The regularity of tangential magnetic flux focusing near the corrosion center is investigated, and the tangential magnetic induction intensity component is searched in the two-dimensional magnetic signal domain. The local extreme location is used to obtain the corrosion center. For sensor arrangements with differences in positive and negative directions, a different approach can also be adopted. The local extreme values ​​determine the corrosion center.

[0135] S502: Search for the maximum and minimum values ​​of the normal magnetic induction intensity component in the two-dimensional original spontaneous leakage magnetic flux matrix or interpolated magnetic signal matrix, and use the difference in axial coordinates corresponding to the maximum and minimum values ​​as the corrosion axial range.

[0136] S503: Cross section at the corrosion center Extract the tangential magnetic induction intensity component curve or smooth envelope energy field curve, and determine the corrosion circumferential boundary by background mean and standard deviation, maximum inter-class variance or local adaptive threshold;

[0137] S504: Based on corrosion center coordinates The axial range and circumferential boundary of corrosion are used to establish an elliptical physical prior domain for the corrosion region.

[0138] To ensure the level set front decelerates and eventually stops at the corrosion boundary, an edge stopping function is constructed based on the gradient magnitude G of the smooth envelope energy field. The formula for calculating the elliptical physical prior domain of the corrosion region is as follows:

[0139] ;

[0140] In the formula: The elliptic physical prior domain is the region of corrosion. For any coordinate point on the image plane; The coordinates of the corrosion center; Let be the semi-axis length of the elliptic physical prior domain along the axial direction, determined based on the axial range of corrosion. Take half of the axial range or its magnification factor; Let be the semi-axis length of the elliptic physical prior domain in the circumferential direction, determined based on the circumferential boundary of the corrosion. Take half of the circumferential range or its magnification factor. To ensure that the initial contour covers the actual eroded area, perform slight morphological dilation on ΩE using structuring elements with a radius of 1 to 3 pixels to obtain the initial inner and outer regions of the level set, and define the neighborhood of ΩE as the local region of interest (ROI).

[0141] VI. Edge Stop Function

[0142] In specific implementation, the processing steps of the edge stopping function include:

[0143] S601: To ensure that the initial contour covers the actual eroded area, the elliptical physical prior domain of the eroded area is... Slight morphological dilation is performed using structuring elements with a radius of 1 to 3 pixels, and an elliptical physical prior domain is used. The neighborhood zone is defined as the region of interest (ROI).

[0144] S602: Constructing indicator functions based on local zones of interest (ROIs) ;when When located within a local region of interest (ROI) =1, otherwise =0;

[0145] Indicator Function The calculation formula is:

[0146] ;

[0147] In the formula: For any coordinate point on the image plane;

[0148] S603: To decelerate and eventually stop the level set front at the erosion boundary, an edge stopping function is constructed based on the gradient magnitude G of the smooth envelope energy field. The edge stopping function is constructed using the gradient magnitude of the smooth envelope energy field.

[0149] ;

[0150] In the formula: This is the edge stopping function; To smooth the gradient magnitude of the envelope energy field;

[0151] S604: Indicator function and edge stopping function Combined to form a weighted stopping function for the evolution of the level set;

[0152] The formula is expressed as:

[0153] ;

[0154] In the formula: This is a weighted stopping function; For indicator functions; Evolution weights within the region of interest (ROI); The evolution weights are those outside the region of interest (ROI).

[0155] VII. Horizontal Set Outline

[0156] In the specific implementation process, the steps for updating the level set contour include:

[0157] S701: The morphologically expanded elliptical physical prior domain As the initial level set outline;

[0158] S702: Solve the level set evolution equation using level set functions to update the level set profile;

[0159] The formula for calculating the level set evolution equation is:

[0160] ;

[0161] ;

[0162] In the formula: For level set functions, For any coordinate point on the image plane, The number of iterations (evolution time); This is a weighted stopping function; For curvature term; For the convection term coefficient, Used to cause the initial contour to converge from the outside in; This is the gradient operator.

[0163] S703: Repeat step S702 to iteratively solve the level set contour until the contour area change is less than the threshold or the maximum number of iterations is reached, thus obtaining the converged level set contour. When the contour area change between two adjacent iterations is less than the set threshold, or the number of iterations reaches the set upper limit, stop the level set evolution.

[0164] During the iteration process, the curvature term keeps the contour smooth, the edge stopping function causes the contour to stop at the strong gradient boundary, and the ROI weights inhibit the contour from spreading to the background region far away from the physical prior region.

[0165] 8. Inversion profile of the corrosion zone

[0166] In the specific implementation process, the converged level set contour is subjected to closing operations and hole filling to obtain the inverted contour of the corrosion region of the suspension cable. The final output parameters related to the corrosion region include the location of the corrosion center. Corrosion axis start and end coordinates, corrosion axis length, corrosion circumferential start and end angles, corrosion circumferential angle range, circumferential width calculated based on the cable body radius, and corrosion area on the unfolded coordinate surface.

[0167] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the technical solutions. Those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A method for inverting corrosion regions of suspension cables based on spontaneous leakage magnetic energy and physical priors, characterized in that, include: S1: Obtain the tangential and normal magnetic induction intensity components at each axial sampling position and each circumferential sampling angle of the suspension cable; S2: After data correction of each tangential magnetic flux density component and each normal magnetic flux density component, and data matching of axial sampling position and circumferential sampling angle, matrix processing is performed to obtain a two-dimensional original spontaneous leakage magnetic flux matrix with axial position and circumferential angle as coordinates. S3: Periodically interpolate and extend the original two-dimensional spontaneous leakage magnetic matrix along the circumferential direction to obtain the interpolated magnetic signal matrix under the high-resolution circumferential corner grid. S4: Windowing and Hilbert transform the interpolated normal magnetic flux density component in the interpolated magnetic signal matrix along the axial direction, calculate the envelope energy field of the normal magnetic flux density component, and obtain the smoothed envelope energy field through smoothing. S5: Determine the corrosion center based on the local extrema of the tangential magnetic induction intensity component, determine the corrosion axial range based on the peak and valley positions of the normal magnetic induction intensity component, determine the corrosion circumferential range based on the circumferential data distribution at the corrosion center, and construct the physical prior domain of the corrosion region. S6: Morphologically expand the physical prior domain of the eroded region to construct a local zone of interest, and construct a weighted stopping function based on the gradient of the smooth envelope energy field; S7: Using the expanded physical prior domain as the initial profile of the level set, the weighted stopping function is embedded into the level set evolution equation to make the level set profile converge at the erosion boundary of the smooth envelope energy field, thus obtaining the converged level set profile. S8: Perform closing operations and hole filling on the converged horizontal set contour to obtain the inverted contour of the cable erosion area and output the corresponding erosion area related parameters.

2. The method for inverting corrosion regions of suspension cables based on spontaneous leakage magnetic energy and physical priors as described in claim 1, characterized in that: In step S1, a multi-channel magnetic sensor array arranged circumferentially along the cable is used to scan along the axial direction of the cable to obtain the tangential magnetic induction intensity components and normal magnetic induction intensity components at each axial sampling position and each circumferential sampling angle of the cable. The multi-channel magnetic sensing array includes a closed arrangement along the circumference of the suspension cable. The third triaxial magnetic sensor, of which the first Circumferential sampling angle of a triaxial magnetic sensor Represented as: ； In the formula: This is the initial arrangement angle.

3. The method for inverting corrosion regions of suspension cables based on spontaneous leakage magnetic energy and physical priors as described in claim 2, characterized in that: In step S2, the formula for the two-dimensional original spontaneous leakage magnetic flux matrix is ​​expressed as: ； ； In the formula: , These are the two-dimensional original spontaneous leakage magnetic flux matrices of the tangential and normal magnetic flux intensity components, respectively; coordinates The tangential magnetic induction intensity component at the location; coordinates The normal magnetic induction intensity component at that location; For the first One axial position; For the first One circumferential angle; This represents the number of axial sampling points; This represents the number of circumferential triaxial magnetic sensors.

4. The method for inverting corrosion regions of suspension cables based on spontaneous leakage magnetic energy and physical priors as described in claim 3, characterized in that: Step S3 specifically includes the following processing steps: S301: Constructing a high-resolution angular mesh , To set the angle increment; S302: For the tangential magnetic flux density component in the two-dimensional original spontaneous leakage magnetic matrix and normal magnetic induction intensity component Sampling positions along each axis in a high-resolution angular grid. Periodic Akima cubic spline interpolation was applied to the circumferential data to obtain the interpolated tangential magnetic flux density components. and normal magnetic induction intensity component ; S303: Based on the interpolated tangential magnetic flux density component and normal magnetic induction intensity component An interpolated magnetic signal matrix for the tangential and normal magnetic induction intensity components under a high-resolution circumferential grid is constructed.

5. The method for inverting corrosion regions of suspension cables based on spontaneous leakage magnetic energy and physical priors as described in claim 4, characterized in that: Step S4 specifically includes the following processing steps: S401: Interpolated normal magnetic flux density component in the interpolated magnetic signal matrix Apply Hanning window weighting; The weighting coefficients of the Hanning window satisfy the following formula: ； In the formula: For the first Hanning window weighting coefficients for each axial sampling point; This represents the number of axial sampling points; S402: Sampling position along the axial direction For the weighted normal magnetic induction component Perform a Hilbert transform to obtain the component of the normal magnetic induction intensity. Orthogonal normal magnetic induction components ; S403: Based on each normal magnetic induction intensity component and the corresponding normal magnetic induction intensity component Calculate the envelope energy field; The formula for calculating the envelope energy field is: ； In the formula: For the envelope energy field in coordinates The value at that location; S404: Perform anisotropic two-dimensional Gaussian smoothing on the envelope energy field to obtain a smoothed envelope energy field.

6. The method for inverting corrosion regions of suspension cables based on spontaneous leakage magnetic energy and physical priors as described in claim 1, characterized in that: In step S404, the formula for the anisotropic two-dimensional Gaussian smoothed Gaussian convolution kernel is: ； In the formula: Use a Gaussian convolution kernel; For axially smooth dimensions; For circumferential smoothing; , These are the axial and circumferential distance variables, respectively.

7. The method for inverting corrosion regions of suspension cables based on spontaneous leakage magnetic energy and physical priors as described in claim 5, characterized in that: Step S5 specifically includes the following processing steps: S501: Search for the local extrema of the tangential magnetic flux density component in the two-dimensional original spontaneous leakage magnetic flux matrix or interpolated magnetic signal matrix to determine the corrosion center. ; S502: Search for the maximum and minimum values ​​of the normal magnetic induction intensity component in the two-dimensional original spontaneous leakage magnetic flux matrix or interpolated magnetic signal matrix, and use the difference in axial coordinates corresponding to the maximum and minimum values ​​as the corrosion axial range. S503: Cross section at the corrosion center Extract the tangential magnetic induction intensity component curve or smooth envelope energy field curve, and determine the corrosion circumferential boundary by background mean and standard deviation, maximum inter-class variance or local adaptive threshold; S504: Based on corrosion center coordinates The axial range and circumferential boundary of corrosion are used to establish an elliptical physical prior domain for the corrosion region.

8. The method for inverting corrosion regions of suspension cables based on spontaneous leakage magnetic energy and physical priors as described in claim 1, characterized in that: In step S504, the formula for calculating the elliptical physical prior domain of the corrosion region is: ； In the formula: The elliptic physical prior domain is the region of corrosion. For any coordinate point on the image plane; The coordinates of the corrosion center; The length of the semi-axis of the elliptic physical prior domain in the axial direction is determined based on the axial range of corrosion. The length of the semi-axis of the elliptic physical prior domain in the circumferential direction is determined based on the circumferential boundary of the corrosion.

9. The method for inverting corrosion regions of suspension cables based on spontaneous leakage magnetic energy and physical priors as described in claim 1, characterized in that: Step S6 specifically includes the following processing steps: S601: Elliptic physical prior domain for the corroded region Morphological dilation is performed, and the elliptical physical prior domain is used. The neighborhood zone is defined as the region of interest (ROI). S602: Constructing indicator functions based on local zones of interest (ROIs) ; Indicator Function The calculation formula is: ； In the formula: For any coordinate point on the image plane; S603: Construct an edge stopping function by smoothing the gradient magnitude of the envelope energy field; ； In the formula: This is the edge stopping function; To smooth the gradient magnitude of the envelope energy field; S604: Indicator function and edge stopping function Combined to form a weighted stopping function for the evolution of the level set; The formula is expressed as: ； In the formula: This is a weighted stopping function; For indicator functions; Evolution weights within the region of interest (ROI); The evolution weights are those outside the region of interest (ROI).

10. The method for inverting corrosion regions of suspension cables based on spontaneous leakage magnetic energy and physical priors as described in claim 1, characterized in that: Step S7 specifically includes the following processing steps: S701: The morphologically expanded elliptical physical prior domain As the initial level set outline; S702: Solve the level set evolution equation using level set functions to update the level set profile; The formula for calculating the level set evolution equation is: ； ； In the formula: For level set functions, For any coordinate point on the image plane, This represents the number of iteration steps. This is a weighted stopping function; For curvature term; For the convection term coefficient; For gradient operators; S703: Repeat step S702 to iteratively solve the level set contour until the contour area change is less than the threshold or the maximum number of iterations is reached, and the converged level set contour is obtained.

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