A dynamic inventory method for coal storage volume of closed coal yard

Abstract

The application discloses a closed coal yard coal storage volume dynamic inventory method, and relates to the technical field of data processing, and comprises the following steps: obtaining three-dimensional point cloud data of a coal pile in a coal yard to construct a triangular subdivision grid of a coal pile surface; analyzing the change of the normal vector included angle of adjacent triangular surfaces in the triangular subdivision grid of the coal pile surface, and identifying the sharp ridge line of the rest angle; connecting and aggregating the sharp ridge line of the rest angle to obtain a ridge line region, and reconstructing the triangular surface of the triangular subdivision grid of the coal pile surface to obtain a plurality of blunted grids; extracting the geometric skeleton of the normal deviation connected region of each blunted grid based on the rest angle, and screening the optimal blunted grid; and calculating the current coal pile volume based on the optimal blunted grid, and combining the previous inventory volume to obtain the dynamic change amount of the coal storage volume, so that the problem that the local form of the grid surface is suddenly changed and the calculation error of the coal pile volume is caused due to the existence of the sharp ridge line of the rest angle of the coal pile, and the accurate dynamic inventory of the coal storage volume is difficult to realize is solved.

Description

Technical Field

[0001] This invention relates to the field of data processing technology, and more specifically, to a method for dynamic inventory of coal storage volume in a closed coal yard. Background Technology

[0002] Coal storage volume inventory is a crucial aspect of closed-loop coal yard operation and management. It typically involves acquiring spatial morphology data of the coal pile and performing 3D reconstruction of the pile surface to calculate the current volume occupied by the coal pile, thereby enabling coal quantity statistics, inventory management, and analysis of coal inflow and outflow. In existing technologies, constructing a triangular mesh of the coal pile surface based on 3D point cloud data is a commonly used spatial reconstruction method. This method, by converting discrete point clouds into continuous triangular patch structures, can effectively represent the spatial undulations of the coal pile surface and provides a data foundation for subsequent volume calculations based on the mesh model.

[0003] However, during the natural accumulation of coal piles in enclosed coal yards, the coal, under the influence of gravity, forms a stable accumulation boundary with an angle of repose, known as the angle of repose region. Due to factors such as local accumulation transitions, coal impacts, and disturbances during coal extraction, the surface triangulation mesh constructed from 3D point clouds easily forms sharp ridge structures in the angle of repose region. These sharp ridges cause abrupt changes in the normal direction between adjacent triangular faces, making the mesh surface unable to continuously represent the actual accumulation morphology of the coal pile. When performing volume calculations based on this type of mesh, local spatial height estimation biases easily occur near the sharp ridges, causing a difference between the volume cells corresponding to the discrete triangular faces and the actual spatial area occupied by the coal pile. As the area of ​​the sharp ridge region expands, this type of error gradually accumulates, leading to a deviation between the final calculated coal storage volume and the actual coal storage quantity. Furthermore, because the coal pile morphology changes continuously within different inventory periods, a fixed mesh processing method is difficult to adapt to the dynamic changes in the angle of repose region, further limiting the accuracy of dynamic inventory of coal storage volume in enclosed coal yards.

[0004] To address the above problems, this invention proposes a solution. Summary of the Invention

[0005] To overcome the aforementioned deficiencies of the prior art, embodiments of the present invention provide a method for dynamic inventory of coal storage volume in a closed coal yard. This method analyzes the changes in the normals of adjacent triangular faces in the triangular mesh on the surface of the coal pile to identify sharp edges of the angle of repose. It then performs connectivity aggregation, triangular face reconstruction, and optimal passivation mesh selection based on geometric skeleton features on the sharp edge regions. This solves the problem that the presence of sharp edges in the angle of repose region of the coal pile causes abrupt changes in the local morphology of the mesh surface and results in errors in the calculation of the coal pile volume, making it difficult to achieve accurate dynamic inventory of coal storage volume.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for dynamic inventory of coal storage volume in a closed coal yard includes the following steps: acquiring three-dimensional point cloud data of the coal pile within the coal yard, and constructing a triangular mesh on the surface of the coal pile based on the three-dimensional point cloud data; analyzing the changes in the angle between the normal vectors of adjacent triangular faces in the triangular mesh on the surface of the coal pile, and identifying sharp edges of the angle of repose based on the analysis results; connecting and aggregating the sharp edges of the angle of repose to obtain edge regions, and reconstructing triangular facets of the triangular mesh on the surface of the coal pile based on the edge regions to obtain several blunted meshes; extracting the geometric skeleton of the connected region of the normal deviation of each blunted mesh based on the angle of repose, and selecting the optimal blunted mesh based on the total length of the geometric skeleton; calculating the current coal pile volume based on the optimal blunted mesh, and obtaining the dynamic change in coal storage volume by combining it with the previous inventory volume.

[0007] In a preferred embodiment, a triangulated mesh for the coal pile surface is constructed based on 3D point cloud data. Specifically, this involves: constructing a coal yard spatial coordinate system and extracting the spatial coordinates of all point clouds from the 3D point cloud data based on the coal yard spatial coordinate system; calculating the spatial coverage of all point clouds on the horizontal plane and dividing the 3D point cloud data into several cubic voxels according to their spatial location based on the spatial coverage; extracting a subset of point clouds within each cubic voxel and performing plane fitting to obtain the fitting plane and fitting residual for each cubic voxel; selecting the cubic voxel with the smallest fitting residual as the seed voxel and expanding outward layer by layer from the fitting plane of the seed voxel; calculating the angle between the fitting plane of adjacent cubic voxels and the current expansion plane, and including adjacent cubic voxels with an angle less than a preset angle threshold in the current expansion plane; repeating the expansion process until no new cubic voxels meet the inclusion criteria; using the 3D point cloud data within all included cubic voxels as the vertex set and triangulating the vertex set to obtain the triangulated mesh for the coal pile surface.

[0008] In a preferred embodiment, the variation of the included angle of the normal vectors of adjacent triangular faces in the triangular mesh of the coal pile surface is analyzed. Specifically, the unit normal vectors of all triangular faces adjacent to each vertex of the triangular mesh of the coal pile surface are obtained, and the average value of all unit normal vectors is calculated as the vertex normal vector of the vertex. The vertex normal vectors of the two endpoints of each common edge in the triangular mesh of the coal pile surface are obtained respectively, and the first included angle value between the vertex normal vectors of the two endpoints is calculated. All common edges are traversed in sequence, and the first included angle value of each common edge is arranged into an included angle sequence according to the arrangement order of the common edges. All local maxima points are marked in the included angle sequence, and the common edges corresponding to the local maxima points are selected as candidate edge edges.

[0009] In a preferred embodiment, the sharp edge of the angle of repose is identified based on the analysis results, specifically as follows: starting from each candidate edge, the adjacent common edges with continuously decreasing angle values ​​to the edge vector of the current candidate edge are traced along the triangular mesh of the coal pile surface to both sides; the traced adjacent common edges are connected to form edge trajectory segments; the straightness of each edge trajectory segment is checked, and the edge trajectory segments are deleted according to the check results to obtain the remaining edge trajectory segments; the remaining edge trajectory segments are taken as the sharp edge of the angle of repose.

[0010] In a preferred embodiment, the sharp edges of the resting angle are connected and aggregated to obtain an edge region. Specifically, the sharp edges of the resting angle are grouped according to their spatial distribution, and the spatial distance between the endpoints of every two sharp edges of the resting angle is calculated. Two sharp edges of the resting angle whose endpoint spatial distance is less than a preset distance threshold are marked as adjacent edges, and a connecting edge is established between the endpoints of the adjacent edges. All sharp edges of the resting angle belonging to the same connected domain are aggregated into an edge region using the connecting edge as a link.

[0011] In a preferred embodiment, the triangular facets of the coal pile surface triangulation grid are reconstructed based on the edge regions to obtain several blunted grids. Specifically, the indices of all triangular faces traversed by the sharp edges of the repose angle contained in each edge region in the coal pile surface triangulation grid are extracted sequentially; based on the indices, all traversed triangular faces are separated from the coal pile surface triangulation grid to obtain an edge region covered grid; the triangular faces in the edge region covered grid are simplified by edge folding to obtain simplified triangular faces; the simplified triangular faces are spliced ​​with the unseparated triangular faces in the coal pile surface triangulation grid to obtain an initial reconstructed grid; using the edge regions as boundary constraints, the triangular facets are re-divided along the boundary lines of the edge regions in the initial reconstructed grid to obtain several blunted grids.

[0012] In a preferred embodiment, the geometric skeleton of the connected region with normal deviation for each passivated mesh is extracted based on the angle of repose, specifically as follows: Calculate the normal deviation angle between the unit normal vector and the vertical unit vector of each triangular face in each passivated mesh, and identify the deviated triangular faces based on the normal deviation angle; perform spatial connectivity clustering on the triangular faces of all deviated triangular faces in the same passivated mesh, and cluster the deviated triangular faces that are connected to each other through a common edge into the same normal deviation connected region; extract the vertex coordinates of all triangular faces in each normal deviation connected region, and construct the region boundary of the normal deviation connected region based on the vertex coordinates; remove the boundary vertices layer by layer inward along the region boundary until the remaining vertices form a centerline structure with a single pixel width; The centerline structure is used as the geometric skeleton of the connected region of the normal deviation.

[0013] In a preferred embodiment, the optimal passivation mesh is selected based on the total length of the geometric skeleton. Specifically, the following steps are taken: All geometric skeletons corresponding to each passivation mesh are read sequentially, and the number of path segments and the length of each path segment in each geometric skeleton are counted. The number of path segments in all geometric skeletons within the same passivation mesh is summed to obtain the total number of path segments in that passivation mesh, and the lengths of each path segment in all geometric skeletons within the same passivation mesh are summed to obtain the total length of the geometric skeleton of that passivation mesh. The total length of the geometric skeletons of all passivation meshes is normalized to obtain the normalized total length of each passivation mesh, and the total number of path segments in each passivation mesh is normalized to obtain the normalized number of path segments in each passivation mesh. The product of the normalized total length and the normalized number of path segments for each passivation mesh is calculated to obtain the comprehensive evaluation value of each passivation mesh, and the passivation mesh with the largest comprehensive evaluation value is selected as the optimal passivation mesh.

[0014] In a preferred embodiment, the current coal pile volume is calculated based on the optimal passivation grid, and the dynamic change in coal storage volume is obtained by combining the previous inventory volume. Specifically, the following steps are taken: the coordinates of the three vertices of all triangular faces in the optimal passivation grid are obtained, and the height of the reference plane at the bottom of the coal pile in the coal yard spatial coordinate system is determined; the area and center point coordinates of the triangular faces are calculated based on the coordinates of the three vertices of the triangular faces, and the center point coordinates are projected onto the reference plane at the bottom of the coal pile to obtain the projection point coordinates; a tetrahedron is constructed using the coordinates of the three vertices of the triangular faces and the projection point coordinates, and the directed volume of the tetrahedron is calculated; all triangular faces in the optimal passivation grid are traversed, and the absolute value of the directed volume corresponding to each tetrahedron is accumulated to obtain the current coal pile volume; the previous inventory volume record is read, the difference between the current coal pile volume and the previous inventory volume is calculated, and the difference is used as the dynamic change in coal storage volume.

[0015] The technical effects and advantages of the present invention, a method for dynamic inventory of coal storage volume in a closed coal yard: This invention achieves a digital representation of the actual spatial morphology of coal piles by acquiring three-dimensional point cloud data of coal piles in a coal yard and constructing a triangular mesh on the coal pile surface. By analyzing the changes in the angle between the normal vectors of adjacent triangular faces in the triangular mesh, the location of sharp edges caused by changes in the repose angle region is accurately identified, thus avoiding the problem of traditional methods failing to locate areas of abrupt local morphological changes. By connecting and aggregating the identified sharp edges of the repose angle to form edge regions, and reconstructing the original triangular mesh based on these edge regions, a blunted mesh is generated, which makes the surface changes of the sharp edge regions continuous and reduces the impact of local mesh abrupt changes on the volume calculation results. Furthermore, based on the repose angle features, the geometric skeleton of the connected regions of the normal deviation in each blunted mesh is extracted, and the optimal blunted mesh that can more accurately maintain the natural accumulation morphology of the coal pile is selected based on the total length of the geometric skeleton, improving the matching degree between the mesh reconstruction results and the actual coal pile surface. Finally, the current coal pile volume is calculated based on the optimal blunted mesh, and the dynamic change in coal storage volume is obtained by combining it with the historical inventory volume, realizing continuous monitoring of changes in coal pile reserves. Therefore, this invention solves the problem that the sharp edges in the angle of repose region of the coal pile cause abrupt changes in the local morphology of the grid surface and lead to errors in the calculation of the coal pile volume, making it difficult to achieve accurate dynamic inventory of coal storage volume. This is achieved by identifying, regionalizing, optimizing the grid passivation, and dynamically calculating the volume. This improves the accuracy and stability of coal storage volume inventory in closed coal yards. Attached Figure Description

[0016] Figure 1 This is a schematic flowchart of a method for dynamic inventory of coal storage volume in a closed coal yard according to the present invention. Detailed Implementation

[0017] 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 embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] Example 1, Figure 1 This invention provides a method for dynamic inventory of coal storage volume in a closed coal yard, comprising the following steps: S1, acquire three-dimensional point cloud data of coal piles in the coal yard, and construct a triangulated mesh on the surface of the coal pile based on the three-dimensional point cloud data; In this embodiment, a triangulated mesh is constructed on the surface of the coal pile based on three-dimensional point cloud data, specifically as follows: Construct a spatial coordinate system for the coal yard, and extract the spatial coordinates of all point clouds from the 3D point cloud data based on the spatial coordinate system for the coal yard; Calculate the spatial coverage of the entire point cloud on the horizontal plane, and divide the 3D point cloud data into several cubic voxel blocks according to the spatial location based on the spatial coverage. Extract the point cloud subset inside each cubic voxel block and perform plane fitting to obtain the fitting plane and fitting residual for each cubic voxel block; The cube voxel block with the smallest fitting residual is selected as the seed voxel block, and the fitting plane of the seed voxel block is used as the starting plane to expand outward layer by layer. Calculate the angle between the fitting plane of adjacent cubic voxels and the current expansion plane in turn, and include adjacent cubic voxels with an angle less than a preset angle threshold into the current expansion plane; The expansion process is repeated until no new cubic voxels meet the inclusion criteria. The 3D point cloud data inside all included cubic voxels are used as the vertex set, and the vertex set is triangulated to obtain the triangulated mesh of the coal pile surface.

[0019] It should be noted that the 3D point cloud data of coal piles within a coal yard refers to a set of discrete spatial sampling points used to describe the external spatial morphology of the coal pile. Each point cloud data point corresponds to a spatial location on the surface of the coal pile, and its spatial coordinate information reflects the actual location of that point within the coal yard space. The 3D point cloud data includes a large number of spatial points distributed along the surface of the coal pile. Each spatial point contains at least horizontal position information and vertical height information. The horizontal position information is used to determine the point's location within the coal yard's planar area, while the height information represents the height variation of the corresponding point on the coal pile surface. Since the surface of the coal pile is not a regular geometric curved surface, and there are morphological changes such as slope inclination, accumulation edges, and local undulations at different locations, the 3D point cloud data can preserve the spatial undulation characteristics of the coal pile surface in the form of discrete points, providing basic data for subsequent construction of a triangulated mesh of the coal pile surface.

[0020] Furthermore, a unified spatial coordinate system for the coal yard is established based on the actual spatial layout within the enclosed coal yard. The length direction of the coal yard is taken as the first horizontal direction, the width direction as the second horizontal direction, and the direction perpendicular to the coal yard floor as the height direction. The origin of the coordinate system is set at a pre-set fixed reference position within the coal yard. This reference position can be a corner point of the coal yard's bottom boundary, an equipment installation reference point, or a manually set measurement reference point, ensuring the same spatial reference is used across different inventory cycles. After establishing the coal yard spatial coordinate system, coordinate transformation is performed on each discrete point in the 3D point cloud data, converting the original coordinates of the point cloud data to the coal yard spatial coordinate system, so that each point cloud point corresponds to a position coordinate under a unified spatial reference. Specifically, the origin offset relationship between the point cloud data acquisition coordinates and the coal yard spatial coordinates is first determined. Then, the spatial orientation of the point cloud points is adjusted according to the directional deflection relationship between the two coordinate systems, ultimately obtaining the 3D coordinate position of each point cloud point in the coal yard spatial coordinate system. After completing the coordinate transformation, the spatial coordinates of all point cloud points are read sequentially, and a point cloud coordinate set is established according to the point cloud point number.

[0021] Secondly, the horizontal coordinates of all point cloud points are read in the coal yard spatial coordinate system, and the maximum and minimum position values ​​of all point cloud points in the length and width directions are calculated. The coverage length of the coal pile in this direction is determined based on the difference between the maximum and minimum position values ​​in the length direction, and the coverage width of the coal pile in this direction is determined based on the difference between the maximum and minimum position values ​​in the width direction, thus obtaining the spatial coverage range of all point cloud data on the horizontal plane. Then, a three-dimensional rule-based region is established based on the above spatial coverage range, dividing the space where the coal pile is located into multiple cubic voxel blocks of the same size. Specifically, the side length of the voxel block is first determined based on the point cloud density of the coal pile. The side length of the voxel block is obtained by counting the number of point clouds per unit area, sorting the number of point clouds from smallest to largest, and selecting the point cloud density in the middle position as the reference density. Based on this reference density, the minimum spatial size that can contain no less than a preset number of point clouds is determined, where the preset number is set to 30-100 points to ensure that each voxel block has a sufficient number of point clouds for subsequent planar fitting. Once the side length of the voxel block is determined, the boundary of the spatial coverage area in the coal yard spatial coordinate system is used as the starting position for division. The area is divided at equal intervals along the length, width, and height directions according to the side length of the voxel block, thus forming multiple cubic voxel blocks covering the entire coal pile area. Each cubic voxel block corresponds to a defined spatial range, and the voxel block to which each point cloud point belongs is determined based on the point cloud point coordinates. Point cloud points within the same spatial range are assigned to the corresponding voxel block.

[0022] Furthermore, based on the spatial boundary conditions corresponding to each cubic voxel block, all point cloud points are spatially filtered, and all point cloud points whose spatial coordinates fall within the range of a certain cubic voxel are extracted to form a point cloud subset corresponding to that cubic voxel block. For each point cloud subset, it is determined whether the number of points inside it meets the plane fitting requirements. When the number of points inside a voxel block is less than a preset number, the voxel block is marked as an invalid voxel block and is not included in subsequent expansion calculations. The minimum number of points in the plane fitting requirements is determined based on the plane stability fitting requirements and is set to no less than 30 points. For point cloud subsets that meet the conditions, a spatial plane fitting method is used to determine the overall spatial trend of the point cloud inside the voxel block. In specific processing, all point cloud points inside the voxel block are used as the fitting object, and a spatial plane that minimizes the overall deviation of all point cloud points is determined based on the positional relationship of each point cloud point. This spatial plane is then used as the fitting plane corresponding to the voxel block. After obtaining the fitted plane, the spatial distance between each point cloud point within the voxel block and the fitted plane is calculated, and the deviation of all point cloud points from the fitted plane is statistically analyzed. The deviation distances of all point cloud points are accumulated to obtain the fitting residual corresponding to the voxel block. The smaller the fitting residual, the closer the point cloud inside the voxel block is to the same plane, indicating that the slope change of the coal pile surface in this area is more continuous, making it more suitable as the starting area for subsequent surface area expansion.

[0023] Furthermore, the fitting residuals corresponding to all valid cubic voxel blocks are sorted in ascending order, and the cubic voxel block with the smallest fitting residual is selected as the seed voxel block. When multiple voxel blocks have the same fitting residual, the number of point clouds inside each voxel block is compared, and the voxel block with the largest number of point clouds is selected as the seed voxel block to ensure that the starting region has more complete surface information. After determining the seed voxel block, the fitting plane corresponding to the seed voxel block is used as the initial expansion plane, and the spatial position of the seed voxel block is used as the expansion starting point. Subsequently, other voxel blocks with spatial adjacency to the seed voxel block are searched around it, and the voxel blocks that are in direct contact with the current expansion region are selected as adjacent voxel blocks to be judged.

[0024] It should be noted that spatial adjacency is determined by whether voxel blocks share a face, an edge, or a vertex, with voxel blocks sharing a face being preferred as the expansion targets. Once the adjacent voxel blocks to be judged are determined, a planar consistency judgment is performed on each adjacent voxel block. Voxel blocks that meet the conditions are added to the current expansion region, and the expansion range is updated using the newly added voxel blocks to expand layer by layer to the outside of the coal pile surface.

[0025] In each expansion process, the direction of the expansion plane corresponding to the current expansion area is first obtained, and the direction of the fitted plane corresponding to each adjacent voxel block to be judged is also obtained. Since the fitted planes all have a definite spatial tilt direction, the difference in direction between the two planes is used to determine whether adjacent voxel blocks belong to the same continuous surface region. Specifically, the angle between the two planes is calculated based on their spatial directions. This angle is used to represent the change in the surface tilt of the adjacent voxel blocks. When the angle between the fitted plane corresponding to the adjacent voxel block and the current expansion plane is small, it indicates that the surface change of the coal pile at that location is continuous, and the voxel block can be considered to belong to the current coal pile surface region; conversely, it indicates that there is a significant slope change at that location, and it is not included in the current expansion area.

[0026] It should be noted that the preset angle threshold is determined based on the continuity requirements of the coal pile surface. Specifically, it is obtained by selecting multiple coal pile surface areas under normal stacking conditions as sample areas, statistically analyzing the surface tilt changes at adjacent locations within these sample areas, sorting all statistical results from smallest to largest, and selecting the angle value corresponding to the 95% of positions after sorting as the initial threshold. This threshold is then adjusted according to the inventory accuracy requirements of a closed coal yard, limiting the final threshold to the range of 5°–15°. When the angle between the fitted plane of an adjacent voxel block and the current extended plane is less than this preset angle threshold, the adjacent voxel block is included in the current extended region, and the extended plane corresponding to the extended region is recalculated.

[0027] After completing one voxel block expansion, the adjacent voxel blocks at the current expansion region boundary are reacquired, and new adjacent voxel blocks are detected one by one according to the fitting plane angle judgment method described above. Voxel blocks that meet the angle condition are added to the current expansion region; voxel blocks that do not meet the condition remain unadded. Subsequently, the current expansion region is updated based on the newly added voxel blocks, and the search for adjacent voxel blocks at the updated expansion boundary continues.

[0028] Finally, when, during a certain expansion process, all adjacent voxel blocks at the boundary locations fail to meet the preset angle condition, meaning no new voxel block can be added to the current expansion region, the expansion process stops. At this point, all 3D point cloud data contained within the cube voxel blocks already included in the expansion region are summarized, and duplicate point clouds and abnormal point clouds that are significantly deviated from the coal pile surface are removed to obtain a vertex set used to characterize the coal pile surface. Subsequently, this vertex set is spatially triangulated, and triangular connections are established based on the spatial proximity between point clouds, so that adjacent spatial points form continuous triangular patches. In the specific triangulation process, point cloud points with close spatial distances and continuous angle changes are connected first to avoid forming incorrect connections across the coal pile edge. Finally, a triangulation mesh of the coal pile surface composed of multiple triangular patches is obtained, which can reflect the spatial morphology of the current coal pile surface.

[0029] S2 analyzes the variation of the angle between the normal vectors of adjacent triangular faces in the triangular mesh of the coal pile surface, and identifies sharp edges of the angle of repose based on the analysis results; In this embodiment, the variation of the angle between the normal vectors of adjacent triangular faces in the triangular mesh of the coal pile surface is analyzed, specifically as follows: Obtain the unit normal vectors of all triangular faces adjacent to each vertex of the triangulated mesh on the coal pile surface, and calculate the average of all unit normal vectors as the vertex normal vector of the vertex. Obtain the vertex normal vectors of the two endpoints of each common edge in the triangulated mesh on the surface of the coal pile, and calculate the first angle between the vertex normal vectors of the two endpoints. Iterate through all common edges in sequence, and form an angle sequence by arranging the first included angle value of each common edge in the order of the common edges; Mark all local maxima in the angle sequence, and take the common edge corresponding to the local maxima as the candidate edge.

[0030] It should be noted that after obtaining the triangulated mesh of the coal pile surface, since each triangular facet can only represent the surface tilt direction within a local area of ​​the coal pile, it is first necessary to determine the overall surface change direction near each grid vertex in order to subsequently determine the slope change of the coal pile surface at different locations. Specifically, the process first iterates through all vertices in the triangulated mesh of the coal pile surface and, based on the connection relationship between the triangular facets and vertices, finds all triangular faces directly connected to each vertex. A direct connection relationship means that if the three vertices of a triangular facet contain the current target vertex, then that triangular facet is considered to belong to the set of adjacent triangular faces corresponding to that vertex. For each triangular facet, the spatial orientation of the triangular facet is determined based on the spatial coordinates of its three vertices, and the unit normal vector of the triangular facet is determined based on the spatial orientation.

[0031] After obtaining the unit normal vectors of all adjacent triangular faces corresponding to a vertex, these unit normal vectors are subjected to direction synthesis processing. The local direction information of multiple adjacent triangular faces is combined into the overall surface direction at the vertex position, resulting in the vertex normal vector. When a vertex is connected to a small number of triangular faces, it is easily affected by local point cloud perturbations. Therefore, before calculation, it is necessary to determine whether the number of adjacent triangular faces corresponding to the vertex meets the statistical requirements. If the number of adjacent triangular faces is less than 3, the vertex is considered to be at the mesh boundary and does not participate in subsequent edge detection; if the number of adjacent triangular faces is 3 or more, the vertex normal vector corresponding to the vertex is retained.

[0032] After calculating all vertex normals, it is necessary to further analyze the directional changes at different locations on the coal pile surface. Specifically, this involves first traversing all common edges in the triangulated mesh of the coal pile surface. A common edge is a mesh edge that connects two adjacent triangular faces. For each common edge, the two endpoints are read, and the vertex normals corresponding to those endpoints are obtained. Since the triangular faces on either side of a common edge typically represent adjacent areas on the coal pile surface, the changes in the vertex normals at the two endpoints of the common edge can reflect the degree of morphological change on the coal pile surface at that location.

[0033] Subsequently, the direction difference of the vertex normal vectors corresponding to the two endpoints of the common edge is judged, the angle between the two vertex normal vectors is calculated, and the angle is taken as the first angle value corresponding to the common edge.

[0034] It should be noted that the larger the first included angle value, the more obvious the change in the tilt direction of the coal pile surface at both ends of the common edge; the smaller the first included angle value, the more continuous the change in the coal pile surface in that area. Since the normal direction change in the normal slope area is usually small during the natural accumulation of coal piles, while significant abrupt changes in direction are likely to occur at the intersection of the angles of repose, the location of possible slope turning points can be preliminarily screened by calculating the first included angle value corresponding to the common edge.

[0035] After obtaining the first included angle value corresponding to each common edge, all first included angle values ​​need to be organized according to the spatial connection relationship of the grid to determine the trend of included angle changes. Specifically, all common edges are read sequentially according to the traversal order of the triangulated grid on the coal pile surface, and the first included angle value corresponding to each common edge is read simultaneously, establishing a correspondence between the common edge number and the first included angle value. Since the common edges themselves have spatial positional relationships, a random arrangement is not used during the sorting process; instead, the arrangement order is determined based on the connection relationship between the common edges. Specifically, firstly, any common edge is selected as the starting edge, and then the next common edge adjacent to the current common edge is visited step by step along the connection direction of adjacent triangular faces, so that common edges with continuous spatial positional relationships are arranged sequentially, forming an edge sequence unfolding along the coal pile surface. After arranging in the above order, the first included angle values ​​corresponding to all common edges are combined sequentially to form an included angle sequence. This included angle sequence can reflect the normal change process of the coal pile surface along the spatial unfolding direction, where the included angle value changes less in continuous and gentle areas, while the positions with edges usually show localized changes in included angle values ​​with sudden increases.

[0036] Furthermore, each first included angle value in the included angle sequence is read sequentially, and the relationship between the current first included angle value and the first included angle values ​​corresponding to its preceding and following positions is compared. When the first included angle value corresponding to a certain common edge is simultaneously greater than the first included angle values ​​corresponding to both the preceding and following common edges, it is considered that the position corresponds to a local maximum point in the included angle sequence. Considering the measurement errors in the point cloud on the coal pile surface and the small-scale disturbances caused by local particle accumulation, relying solely on local maxima can easily generate a large number of false edges. Therefore, additional included angle filtering conditions are set. Specifically, the first included angle values ​​corresponding to all local maxima are statistically analyzed, and all local maxima are sorted according to their numerical values. The included angle values ​​located in the 90% to 95% range after sorting are selected as the initial filtering threshold, and adjusted according to the range of the coal pile's angle of repose, with the final threshold set in the range of 15° to 30°.

[0037] When the first included angle value corresponding to the local maximum is greater than the preset included angle screening threshold, it is considered that there is a significant directional change on the coal pile surface on both sides of the common edge, and the common edge is marked as a candidate edge. When the first included angle value does not reach the preset threshold, it is considered that the position belongs to the normal slope transition area and is not considered as a candidate edge. Through the above processing, common edges with obvious normal change characteristics can be screened from the triangulated mesh of the coal pile surface, so that subsequent continuous tracking along the candidate edge can be performed to identify the actual sharp edges of repose.

[0038] In this embodiment, the sharp edges of the angle of repose are identified based on the analysis results, specifically as follows: Starting from each candidate edge, trace the adjacent common edges that have continuously decreasing angle values ​​with the current candidate edge vector along the triangulation grid of the coal pile surface to both sides; Connect the adjacent common edges obtained from the tracking to form an edge trajectory segment; Perform a straightness check on each edge trajectory segment, and delete the edge trajectory segments based on the check results to obtain the remaining edge trajectory segments; The remaining edge trajectory segment is taken as the sharp edge of the angle of repose.

[0039] It should be noted that each candidate edge is selected sequentially, and the spatial coordinates of its two endpoints are obtained. The direction vector corresponding to the candidate edge is determined based on the spatial relationship between the two endpoints. Subsequently, using the candidate edge as the starting position, adjacent common edges connected to the candidate edge are searched in the triangulated mesh of the coal pile surface. Since a true sharp angle edge usually exhibits a continuous broken line structure along the coal pile surface, it is necessary to determine the changing relationship between adjacent common edges and the current edge direction during the tracking process. Specifically, the triangular face regions connected to both sides of the candidate edge are first determined. In each side region, candidate extension edges with common endpoints to the current common edge are searched, and the angle between each candidate extension edge and the current edge direction is calculated.

[0040] When the angle between an adjacent common edge and the current edge direction is less than the angle value corresponding to the previous tracking process, it is considered that the adjacent common edge continues to extend along the current edge direction, and the adjacent common edge is taken as the next edge candidate edge, and tracking continues outward; when the angle corresponding to the adjacent common edge no longer decreases, or the angle change exceeds the preset range, the extension in that direction stops.

[0041] It should be noted that the preset range of change used to determine the continuous decrease in the included angle is determined based on the dispersion of the grid on the coal pile surface. Specifically, it is obtained by selecting multiple normal coal pile surface areas, statistically analyzing the angle changes along continuous common edges, sorting the changes in the included angle of adjacent common edges from smallest to largest, selecting the change corresponding to the 95th percentile position as the maximum allowable change, and limiting this change to the range of 2° to 8°. When the change in the direction of adjacent common edges is less than this range, the change in that direction is considered to be a continuous extension.

[0042] After continuously tracking both directions of the candidate edge, the common edges that satisfy the condition of continuous directional change need to be connected to form an edge trajectory that can describe the local abrupt change region on the coal pile surface. Specifically, the common edge numbers and corresponding spatial relationships included in each expansion process are first recorded according to the tracking order, and then arranged according to the connection order between the common edges. Subsequently, adjacent common edges are connected sequentially according to their endpoint connections, so that multiple discrete common edges form a continuous spatial polygonal structure. Specifically, when two common edges have a common endpoint and the latter common edge is a continuous edge extending from the former common edge, the two common edges are considered to belong to the same edge trajectory. For cases with multiple branch directions, the continuity in each branch direction is calculated, and the path with the smallest change in directional angle and the longest continuous length is selected as the main edge trajectory. After connection, the spatial polygonal line composed of multiple continuous common edges is taken as an edge trajectory segment. Each edge trajectory segment corresponds to a position on the coal pile surface where a repose angle boundary may exist, and it includes the trajectory start point, trajectory end point, and information on all the common edges traversed in between.

[0043] It should be noted that due to the random accumulation texture, local unevenness, and point cloud sampling errors on the coal pile surface, some edge trajectory segments formed by connecting candidate edge edges may not be true repose angle boundaries, but rather pseudo-trajectories generated by local anomalies. Therefore, it is necessary to perform a straightness check on each edge trajectory segment to determine whether it possesses the continuous extension characteristics that a sharp repose angle edge should have.

[0044] In the specific processing, the spatial coordinates of all common edge endpoints in a certain edge trajectory segment are first read and arranged in the trajectory connection order to form a trajectory point set. Then, the overall extension direction of the edge trajectory segment is determined based on the starting and ending points of the trajectory, and the positional deviation of all intermediate points in the trajectory from this extension direction is judged. When the trajectory segment belongs to a sharp edge with a true angle of repose, its spatial shape usually appears as an approximately continuous straight line or a slowly changing curve; therefore, the deviation of the trajectory points relative to the overall extension direction is small. When the trajectory segment is formed by random noise, the distribution of its trajectory points has no obvious direction, and the deviation is large. In the specific verification process, the maximum deviation distance of all trajectory points in the trajectory segment relative to the overall extension direction is first calculated, then the average value of all deviation distances is calculated, and the straightness of the trajectory segment is judged based on both. When the ratio of the maximum deviation distance to the total length of the trajectory segment is less than a preset ratio threshold, the trajectory segment is considered to meet the straightness requirement.

[0045] It should be noted that the preset proportion threshold is determined based on the actual shape of the coal pile's angle of repose edge. Specifically, the threshold is obtained by collecting multiple coal pile edge samples under different stacking conditions, statistically analyzing the deviation proportions of manually labeled valid edge trajectories, and using the proportions corresponding to 95% of the valid edges in the statistical results as the maximum allowable proportion, set between 3% and 8%. Edge trajectory segments that meet the straightness requirement are retained; edge trajectory segments that do not meet the straightness requirement are considered to lack continuous angle of repose boundary characteristics and are removed from the candidate results.

[0046] After verifying the straightness of all edge trajectory segments, the retained edge trajectory segments are used as the final identified sharp repose angle edges. Specifically, after the aforementioned processing, the retained edge trajectory segments simultaneously satisfy the following conditions: there is a significant change in normal direction at their corresponding positions, their spatial extension direction is continuous, and their trajectory shape satisfies the boundary characteristics formed by the natural accumulation of coal piles. Therefore, this type of edge trajectory segment can effectively characterize the sharp boundary region formed by the intersection of slopes with different repose angles on the surface of the coal pile. In subsequent processing, each sharp repose angle edge is treated as an independent spatial feature object, and its set of common edges, endpoint coordinates, and spatial extension direction information are retained to further determine the spatial connection relationship between different sharp edges.

[0047] S3, connect and aggregate the sharp edges of the angle of repose to obtain the edge region, and reconstruct the triangular facets of the triangular mesh on the coal pile surface based on the edge region to obtain several passivated meshes;

[0048] In this embodiment, the sharp edges of the angle of repose are connected and aggregated to obtain the edge region, specifically: The sharp edges of the angle of rest are grouped according to their spatial distribution, and the spatial distance between the endpoints of every two sharp edges of the angle of rest is calculated. Two sharp edges of the resting angle with an endpoint spatial distance less than a preset distance threshold are marked as adjacent edges, and a connecting edge is established between the endpoints of the adjacent edges; By using connecting edges as links, all sharp edges of resting angles belonging to the same connected domain are aggregated into a single edge region.

[0049] It should be noted that after obtaining multiple sharp edges of the angle of repose, since there may be multiple sharp boundary regions formed by different accumulation processes on the surface of the coal pile, it is necessary to further analyze the spatial proximity relationship between each sharp edge of the angle of repose in order to determine the set of edges belonging to the same continuous region.

[0050] In the specific processing, the spatial position information corresponding to each sharp angle of repose is first read, including the coordinates of the starting and ending points of the edge, as well as the spatial positions of all common edges traversed by the edge. Then, the sharp angles of repose are initially grouped according to their distribution on the coal pile surface.

[0051] Grouping is based on spatial location distribution. Specifically, the triangular mesh of the coal pile surface is divided into multiple spatially adjacent regions. The triangular region containing each sharp angle of repose edge is determined, and sharp angles of repose edges located within the same or adjacent spatial regions are grouped into the same set to be analyzed. This method reduces the scope of spatial distance calculations and avoids invalidating the analysis of edges that are far apart and have no connection.

[0052] After initial grouping, the spatial distance between the endpoints of any two sharp edges of rest within the same set to be analyzed is calculated. Specifically, the starting and ending endpoints of the first sharp edge of rest are obtained, and then the starting and ending endpoints of the second sharp edge of rest are obtained. The spatial distance between the four sets of endpoint combinations is calculated, and the minimum distance is selected as the endpoint distance between the two sharp edges of rest.

[0053] Furthermore, the minimum spatial distance between the endpoints of each pair of sharp angles of repose is compared with a preset distance threshold. When the spatial distance between the endpoints of two sharp angles of repose is less than the preset distance threshold, the two edges are considered to be in adjacent positions on the coal pile surface, and they may belong to the same continuous boundary region. Therefore, the two sharp angles of repose are marked as adjacent edges.

[0054] It should be noted that the preset distance threshold is used to limit the maximum connection range between edges, and its acquisition method is determined based on the spatial resolution of the triangulated mesh on the coal pile surface. Specifically, firstly, the side lengths of all triangular faces are counted, and all side lengths are arranged in ascending order. The side length in the middle position is selected as the average side length of the mesh. Then, based on the edge connection requirements, 2 to 5 times the average side length is used as the initial distance threshold range. When the 3D point cloud density changes, causing the mesh side length to change, this distance threshold is adjusted synchronously to ensure that the edge connection scale remains consistent across different inventory cycles.

[0055] After identifying adjacent edges, a connecting edge is established between the two adjacent edges. Specifically, this is done by identifying the closest pair of endpoints between the two edges, using these two endpoints as the endpoints of the connecting edge, and establishing a spatial connection between them. Through this connecting edge, multiple originally independent sharp-angled edges can be transformed into a spatial structure with a connection relationship, providing a foundation for subsequent aggregation of connected regions.

[0056] After establishing the connecting edges between adjacent edges, it is necessary to further determine the regions to which sharp edges with different angles of repose belong based on the connection relationship between the edges.

[0057] In the specific processing, each sharp edge of the resting angle is treated as an independent node, and the connecting edges are used as the association between nodes. Based on the connection relationship, a connectivity analysis is performed on all sharp edges of the resting angle.

[0058] First, select any unprocessed sharp angle edge as the starting edge. Read all adjacent edges directly connected to this edge, and continue searching for other edges connected to these adjacent edges until no new connectable edges exist. Then, group all sharp angle edges that can be mutually accessed in the above process into the same connected set.

[0059] Since there are no connecting edges that satisfy the distance condition between different connected sets, they are considered to belong to different spatial regions and are stored separately. After traversing all edges, each connected set corresponds to an edge region. Each edge region contains multiple spatially continuous sharp edges with rest angles, and retains the spatial position, connection relationship, and boundary information of all edges within the region.

[0060] Through the above aggregation process, the scattered sharp edges of the resting angle can be merged according to their actual spatial connection relationship, so that multiple edge segments in the same stacking boundary area can form a complete region representation, avoiding the problem of local reconstruction discontinuity caused by only processing a single edge in the subsequent mesh reconstruction process.

[0061] Since the sharp edges of the repose angle on the surface of a coal pile are usually formed by the intersection of different slopes during the coal pile's accumulation, their spatial form is not a single isolated line segment, but may appear as an irregular boundary composed of multiple continuous line segments. Therefore, this step does not simply merge them according to the number of edges, but establishes connections based on the spatial distance between the endpoints of the edges, and determines the actual spatially related areas through connectivity judgment.

[0062] When a certain ridge region contains multiple ridges with sharp angles of repose, it indicates that there is a continuous slope change boundary on the surface of the corresponding coal pile in that region; when a certain ridge with a sharp angle of repose cannot be connected with other ridges, it is saved as a separate ridge region.

[0063] In this embodiment, triangular facet reconstruction is performed on the triangular mesh of the coal pile surface based on the edge region to obtain several passivated meshes, specifically: Extract the indices of all triangular faces that the sharp edges of the repose angle contained in each edge region pass through in the triangular mesh of the coal pile surface; Based on the index, all the triangular faces that have passed through are separated from the triangular mesh of the coal pile surface to obtain the edge region coverage mesh. The triangular faces in the mesh covering the edge region are simplified by edge folding to obtain the simplified triangular faces. The simplified triangular face after edge folding is spliced ​​with the triangular face that was not separated in the triangular mesh of the coal pile surface to obtain the initial reconstructed mesh. Using the edge region as the boundary constraint, the triangular facets are re-divided along the boundary line of the edge region in the initial reconstructed mesh, resulting in several blunted meshes.

[0064] It should be noted that after obtaining multiple edge regions, since the sharp edge of the repose angle only represents the local sharp change position on the coal pile surface, and the actual mesh reconstruction needs to process the complete triangular facet region containing the edge region, it is first necessary to determine the coverage of each edge region in the triangulation mesh of the original coal pile surface.

[0065] In the specific processing, all the sharp edges of repose corresponding to each edge region are read sequentially, and the set of common edges contained in each sharp edge of repose is obtained. Since the sharp edges of repose are composed of multiple continuous common edges, and each common edge belongs to two adjacent triangular faces in the triangulation mesh of the coal pile surface, all the triangular faces that the edge passes through can be determined according to the topological connection relationship between the common edges and the triangular faces.

[0066] Specifically, firstly, the first common edge in a certain angle of repose is read. Based on the index information of the common edge in the triangulation mesh, the two triangular faces adjacent to the common edge are found and their numbers are recorded. Then, all the common edges contained in the angle of repose are traversed in turn, and the adjacent triangular face numbers corresponding to each common edge are added to the triangular face index set corresponding to the current edge.

[0067] When the same triangle face is accessed by multiple shared edges, only one index record is retained to avoid duplicate retrieval. After retrieving the index of the triangle face corresponding to a sharp angle of repose, the process continues to process other sharp angles of repose within the same edge region, ultimately obtaining the index of all covered triangle faces corresponding to that edge region.

[0068] Furthermore, after obtaining the set of triangular face indices corresponding to each edge region, these triangular faces need to be extracted from the original triangulation mesh of the coal pile surface to form local processing objects for areas with sharp angles of repose. Specifically, the process begins by reading all triangular face indices corresponding to a given edge region, and then locating the corresponding triangular face in the original triangulation mesh of the coal pile surface based on these indices. For each located triangular face, its three vertex numbers, three vertex spatial coordinates, and connection relationships with adjacent triangular faces are extracted. All triangular faces belonging to the current edge region are then aggregated and stored to form an edge region covering mesh.

[0069] After processing all the edge regions, the original coal pile surface triangulation mesh was divided into two parts: one part was the edge region covering mesh, used for local passivation; the other part was the stable region mesh that was not separated, used for subsequent splicing with the reconstructed region. Because there are many small triangular facets near the sharp edges of the repose angle, directly re-dividing the mesh could easily lead to an excessive number of meshes in the reconstructed region, affecting the efficiency of subsequent volume calculations. Therefore, it is necessary to appropriately simplify the edge region covering mesh.

[0070] In practice, all grid edges in the edge region's covered mesh are inspected, and the folding cost for each edge is calculated. The folding cost measures the impact on the original coal pile surface morphology after deleting an edge and merging its two endpoints. After identifying the edge to be processed, grid edges with lower folding costs are prioritized for folding. The folding process involves merging the two endpoints of the edge to be folded into a new vertex and readjusting the connection relationships of the triangular faces connected to that edge, reconnecting the multiple triangular faces originally distributed around the edge. After each edge folding operation, the updated mesh structure is re-inspected, and grid edges that meet the conditions are selected for folding until the preset simplification ratio is reached.

[0071] The simplification ratio is determined based on the number of triangular faces in the grid covering the edge region. Specifically, this ratio is obtained by statistically analyzing the changes in the number of triangular faces in the edge region across multiple coal pile surface reconstruction samples. The goal is to ensure that the reconstructed grid retains its angle of repose boundary shape, and the ratio of the number of triangular faces retained after simplification to the original number is determined to be between 40% and 70%. The edge folding process is stopped when this ratio is reached.

[0072] Furthermore, after simplifying the edge region covering mesh, the processed local mesh needs to be re-embedded into the original coal pile surface triangulation mesh to restore the complete coal pile surface structure. Specifically, the simplified edge region covering mesh after edge folding is first read, and the vertex information at the mesh boundary is obtained; then, the triangular face information of the unseparated regions in the original coal pile surface triangulation mesh is read. Since the edge region covering mesh only replaces a local area in the original mesh, the boundary vertices between the two regions must be consistent during the splicing process. Specifically, spatial position matching is performed between the simplified mesh boundary vertices and the corresponding boundary vertices of the unseparated mesh. When the spatial distance between two boundary vertices is less than a preset matching distance, the two vertices are considered the same connection point.

[0073] It should be noted that the boundary matching distance is determined based on the average side length of the original mesh. Specifically, it is obtained by statistically analyzing all side lengths of the original triangulated mesh and calculating the average side length, then using 20% ​​to 50% of the average side length as the boundary matching distance. After boundary matching is completed, the simplified edge region mesh is merged and connected with the unseparated region mesh to form the initial reconstructed mesh covering the entire coal pile surface.

[0074] Furthermore, the boundary line of each edge region is read and used as a fixed constraint boundary in the re-meshing process. Subsequently, in the initial reconstructed mesh, triangular connections located inside the edge regions that do not meet the smooth connection requirements are deleted, and triangular connections are re-established based on the spatial positions between boundary vertices. During the re-meshing process, the new triangular facet connection method is determined according to the following rules: boundary vertices with closer spatial distances are connected first, while limiting the range of side length variations of newly generated triangular faces to maintain a continuous transition between adjacent triangular faces.

[0075] The constraint on the variation of triangular facet side lengths is determined based on the statistical results of the original mesh side lengths. Specifically, the average side length of all triangular faces in the initial reconstructed mesh is calculated, and the side lengths of newly generated triangular faces are restricted to within 0.5 to 2 times the average side length, preferably within 0.8 to 1.5 times, to avoid generating excessively large or small triangular faces. After re-meshing, each local mesh after edge region passivation is considered a passivated mesh. The passivated mesh adjusts the connection method of triangular faces near sharp edges, transforming the coal pile surface from an abrupt structure to a continuous transition structure while preserving the overall spatial morphology of the coal pile. This provides a processing basis for subsequent optimal passivated mesh selection based on the angle of repose and volume calculation.

[0076] S4. Extract the geometric skeleton of the connected region of the normal deviation of each passivation mesh based on the angle of repose, and select the optimal passivation mesh according to the total length of the geometric skeleton. In this embodiment, the geometric skeleton of the connected region of the normal deviation of each passivation mesh is extracted based on the angle of repose, and the optimal passivation mesh is selected according to the total length of the geometric skeleton. Specifically: Calculate the normal deviation angle between the unit normal vector and the vertical unit vector of each triangular face in each passivated mesh, and identify the deviated triangular face based on the normal deviation angle; Spatial connectivity clustering is performed on all deviation triangles within the same passivated mesh, and deviation triangles that are connected to each other through a common edge are clustered into the same normal deviation connected region. Extract the vertex coordinates of all triangular faces in each normal deviation connected region, and construct the region boundary of the normal deviation connected region based on the vertex coordinates; Remove boundary vertices layer by layer inward along the region boundary until the remaining vertices form a centerline structure with a single pixel width; The centerline structure is used as the geometric skeleton of the connected region of the normal deviation.

[0077] It should be noted that after obtaining several passivation grids, due to the reconstruction results of different sharp edge regions on the coal pile surface corresponding to different passivation grids, and the fact that the stable slope area that meets the angle of repose condition usually has an inclination direction close to a fixed range during the actual coal pile accumulation process, it is necessary to further determine the inclination change of the triangular face in each passivation grid relative to the vertical direction in order to determine the degree to which each passivation grid maintains the natural accumulation morphology of the coal pile.

[0078] In the specific processing, firstly, all triangular faces in each passivated mesh are read sequentially, and the spatial coordinates of the three vertices of each triangular face are obtained. The spatial orientation of the triangular face is determined based on the spatial relationship of the three vertices, and the unit normal vector of the triangular face is further determined. Subsequently, the unit normal vector of each triangular face is compared with a preset vertical direction to obtain the normal deviation angle of the triangular face. The vertical direction is the height direction in the coal yard spatial coordinate system, which is used to represent the natural stacking direction of the coal pile under the action of gravity.

[0079] Furthermore, the distribution of normal deviation angles of all triangular faces within the same passivated grid is statistically analyzed and sorted according to angle magnitude. Then, the angle value at the 95th percentile after sorting is selected as the initial deviation judgment reference value, and further corrected based on the coal pile's angle of repose range, ultimately limiting the final normal deviation angle threshold to the range of 10°–25°. When the normal deviation angle of a triangular face is greater than the preset normal deviation angle threshold, it is considered that there is a significant directional deviation at the corresponding position of the triangular face, and the triangular face is marked as a deviation triangular face. When the normal deviation angle is less than or equal to the threshold, the triangular face is considered to belong to the normal transition region and is not considered a deviation triangular face.

[0080] After obtaining all deviation triangles in each passivated mesh, adjacency relationships between the deviation triangles are established. For any two deviation triangles, if they share a common edge, they are considered spatially directly connected and an adjacency relationship is established. Subsequently, each deviation triangle is treated as an independent node, and a region search is performed based on the connection relationships of the common edges between them. Specifically, starting from any unprocessed deviation triangle, other deviation triangles directly connected to that triangle are searched, and this search continues to expand to find other deviation triangles connected to newly added deviation triangles until no new connectable deviation triangles exist. All mutually connected deviation triangles are grouped into the same normal deviation connected region. After completing one region division, the same process is repeated for unprocessed deviation triangles until all deviation triangles have been divided into regions.

[0081] After obtaining multiple connected regions with normal deviations, the vertex information of all deviation triangles within these regions is read. Since adjacent triangles share common vertices, duplicate vertices are removed during the reading process, retaining only unique sets of spatial vertices. Subsequently, the outer boundary of the connected region with normal deviations is determined based on the spatial distribution of all vertices. Specifically, firstly, the vertices of the region are projected onto the horizontal plane in the coal yard spatial coordinate system, converting the vertices in three-dimensional space into planar position points. Then, following the principle of point cloud perimeter connection, boundary connection paths that can enclose all region vertices are sequentially searched, starting from the outermost vertex, to form a closed region boundary. After determining the two-dimensional boundary, the original three-dimensional coordinates corresponding to the boundary vertices are remapped back to the coal pile surface space, obtaining the three-dimensional boundary of the connected region with normal deviations.

[0082] Furthermore, after obtaining the boundary of the normal deviation connected region, a vertex network is established for all vertices inside the normal deviation connected region according to the spatial connection relationship, and the network is shrunk layer by layer starting from the outermost boundary vertex of the region.

[0083] First, identify the vertices located on the outer boundary of the region and determine the connection relationship between each boundary vertex and the vertices inside the region. For boundary vertices that meet the deletion criteria, remove them from the current vertex set, while preserving the connection relationships between the remaining vertices.

[0084] The conditions for deleting boundary vertices include: (1) Deleting this vertex does not change the overall connectivity of the region; (2) Deletion will not cause the region to generate multiple independent branches; (3) This vertex does not belong to the key turning point of the region.

[0085] After completing one round of boundary vertex deletion, a new region boundary is determined, and the next round of internal contraction continues.

[0086] Through multiple iterations, the region gradually shrinks from the outside in. The shrinkage process stops when only one continuous path remains within the region, and there are no more boundary vertices on either side of this path that can be deleted.

[0087] At this point, the remaining vertices and their connections form a centerline structure with a width of one pixel. This centerline structure reflects the main spatial extension direction of the normal deviation region. The stopping condition is determined based on the width of the remaining vertices. When the number of remaining vertices in any cross-sectional direction of the region is less than or equal to one, the single-pixel width requirement is considered met.

[0088] After the region is shrunk layer by layer, the remaining centerline structure is used as the geometric skeleton of the corresponding normal deviation connected region. Specifically, the geometric skeleton consists of continuously arranged central vertices and path segments connecting them, its spatial location being within the original normal deviation connected region, reflecting the overall extension direction and structural length of that region. For each normal deviation connected region, its corresponding geometric skeleton information is saved, including the skeleton node positions, the connections between nodes, and the skeleton path length. Since different passivation meshes may correspond to different degrees of sharp region elimination effects, the number, shape, and geometric skeleton length of the formed normal deviation regions differ. Subsequently, by statistically analyzing the length characteristics of all geometric skeletons corresponding to each passivation mesh, the preservation of the coal pile's angle of repose structure by different passivation meshes can be evaluated, and the optimal passivation mesh can be further selected.

[0089] In this embodiment, the optimal passivation mesh is selected based on the total length of the geometric skeleton, specifically as follows: Read all the geometric skeletons corresponding to each passivated mesh in sequence, and count the number of path segments contained in each geometric skeleton and the path length of each path segment respectively; The total number of path segments in the passivated mesh is obtained by summing the number of path segments in all geometric skeletons within the same passivated mesh, and the total length of the geometric skeleton in the passivated mesh is obtained by summing the lengths of each path segment in all geometric skeletons within the same passivated mesh. The total length of the geometric skeleton of all passivated meshes is normalized to obtain the normalized total length of each passivated mesh. At the same time, the total number of path segments of each passivated mesh is normalized to obtain the normalized number of path segments of each passivated mesh. Calculate the product of the normalized total length and the number of normalized path segments for each passivation grid to obtain the comprehensive evaluation value of each passivation grid, and select the passivation grid with the largest comprehensive evaluation value as the optimal passivation grid.

[0090] It should be noted that after obtaining the geometric skeleton of multiple normal deviation connected regions corresponding to each passivation grid, since different passivation grids are reconstructed for sharp edge regions with different angles of repose, their degree of preservation of the original coal pile accumulation shape varies. Therefore, it is necessary to evaluate each passivation grid by analyzing the distribution of the geometric skeleton.

[0091] In the specific processing, the complete geometric skeleton information corresponding to each passivated mesh is first read sequentially. The geometric skeleton information includes the positions of skeleton nodes, the connection relationships between nodes, and the path segment information formed by the node connections. Here, a path segment refers to the connection between any two adjacent skeleton nodes in the geometric skeleton, used to represent the local extension direction of the geometric skeleton. For a given passivated mesh, the geometric skeleton corresponding to all normal deviation connected regions within that passivated mesh is traversed first, and the number of path segments contained in each geometric skeleton is counted. Specifically, the count is performed based on the connection relationships between skeleton nodes; for each valid node connection, a corresponding path segment is generated, and the total number of path segments contained in that geometric skeleton is accumulated.

[0092] Subsequently, for each path segment, the spatial coordinates of the skeleton nodes at both ends of the path segment are read, and the actual length of the path segment is determined based on the spatial relationship between the two nodes. After completing the length statistics of all path segments within a single geometric skeleton, the other geometric skeletons in the passivated mesh are processed to finally obtain the number of path segments and the length of each path segment for each geometric skeleton within the passivated mesh.

[0093] Furthermore, after obtaining the number and length of path segments corresponding to a single geometric skeleton, it is necessary to further evaluate the structural characteristics of the region corresponding to each passivated mesh from an overall perspective.

[0094] In specific processing, for any passivated mesh, the geometric skeleton corresponding to all normal deviation connected regions within the passivated mesh is read, and the number of path segments contained in all geometric skeletons is accumulated.

[0095] For example, if a passivated mesh contains multiple normal deviation connected regions, then the number of geometric skeleton path segments corresponding to each normal deviation connected region is read, and the total number of path segments is summed to obtain the total number of path segments corresponding to the passivated mesh.

[0096] Subsequently, the path segment lengths contained in all geometric skeletons within the same passivated mesh are accumulated. Specifically, the lengths of all path segments in each geometric skeleton are read sequentially, and the lengths of all path segments belonging to the same passivated mesh are summed to obtain the total length of the geometric skeleton corresponding to that passivated mesh.

[0097] The total length of the geometric skeleton represents the overall extent of the directional deviation region within the passivated grid. When the passivated grid can maintain a good continuous change in the coal pile's angle of repose, its internal normal deviation region is usually small, and the total length of the geometric skeleton is small; when the passivated grid still has significant surface orientation anomalies, its corresponding geometric skeleton extension range is large.

[0098] The total number of path segments is used to supplement the reflection of the complexity of the normal deviation region. When multiple short-distance deviation regions exist simultaneously, it may not be accurate to distinguish them based on the total length alone. Therefore, combining the number of path segments can further improve the accuracy of the evaluation.

[0099] Furthermore, since the number and spatial range of the normal deviation regions corresponding to different passivation meshes are different, the numerical ranges of the total length of the geometric skeleton and the total number of path segments are different and cannot be directly compared. Therefore, it is necessary to unify the scale processing of the above two evaluation parameters.

[0100] In the specific processing, firstly, the total length of the geometric skeleton corresponding to all passivated meshes is read, and the maximum and minimum values ​​are determined. Then, based on the range between the maximum and minimum values, the total length of the geometric skeleton corresponding to each passivated mesh is converted into a normalized total length within a uniform numerical range.

[0101] Similarly, the total number of path segments corresponding to all passivated meshes is read, and the maximum and minimum values ​​of the total number of path segments are determined. The total number of path segments corresponding to each passivated mesh is then converted into a normalized number of path segments in the same way. Specifically, when the maximum and minimum values ​​of a certain evaluation parameter are the same across all passivated meshes, it indicates that there is no difference in that parameter among different passivated meshes. In this case, the normalized result corresponding to that parameter is uniformly set to a preset fixed value, preferably 1, to avoid calculation anomalies due to a zero denominator. Through normalization, the geometric skeleton length characteristics and path segment quantity characteristics of different passivated meshes are converted to the same evaluation scale, thus enabling subsequent comprehensive comparisons.

[0102] After obtaining the normalized total length and the number of normalized path segments corresponding to each passivation grid, it is necessary to evaluate the ability of different passivation grids to maintain the surface structure of the coal pile based on the two parameters.

[0103] In the specific processing, the normalized total length and the number of normalized path segments corresponding to each passivated grid are read separately, and the two normalized parameters are combined to calculate the comprehensive evaluation value corresponding to the passivated grid.

[0104] The comprehensive evaluation value considers both the overall extension of the normal deviation region and the complexity of the regional structure. A larger comprehensive evaluation value corresponds to a longer normal deviation region or more skeletal branch structures within a passivation grid; conversely, a smaller comprehensive evaluation value corresponds to a passivation grid that makes the directional changes on the coal pile surface more continuous and reduces abnormal deviation regions. After calculating the comprehensive evaluation values ​​for all passivation grids, all comprehensive evaluation values ​​are compared, and the passivation grid with the largest comprehensive evaluation value is selected as the optimal passivation grid.

[0105] The reason for selecting the passivated grid with the highest comprehensive evaluation value is that different passivated grids are all reconstructed from sharp edge regions with different angles of repose. The passivated grid with the highest comprehensive evaluation value indicates that it retains the most complete normal deviation skeleton features, which can more accurately reflect the slope change law under the natural stacking state of the coal pile. Therefore, it is suitable as the basis for subsequent coal pile volume calculation.

[0106] S5 calculates the current coal pile volume based on the optimal passivation grid and obtains the dynamic change in coal storage volume by combining it with the previous inventory volume.

[0107] In this embodiment, the current coal pile volume is calculated based on the optimal passivation grid, and the dynamic change in coal storage volume is obtained by combining it with the previous inventory volume. Specifically: Obtain the coordinates of the three vertices of all triangular faces in the optimal passivation mesh, and determine the height of the reference plane at the bottom of the coal pile in the coal yard spatial coordinate system; Calculate the area and center point coordinates of the triangular face based on the coordinates of its three vertices, and then project the center point coordinates onto the reference plane at the bottom of the coal pile to obtain the coordinates of the projected point. Construct a tetrahedron using the coordinates of the three vertices and the projection point of the triangular face, and calculate the directed volume of the tetrahedron; The current coal pile volume is obtained by traversing all triangular faces in the optimal passivation mesh and accumulating the absolute value of the directed volume corresponding to each tetrahedron. Read the previous inventory volume record, calculate the difference between the current coal pile volume and the previous inventory volume, and use the difference as the dynamic change in coal storage volume.

[0108] In this embodiment, the formula for calculating the directed volume of a tetrahedron is as follows:

[0109] in, This represents the absolute value of the directed volume of the tetrahedron corresponding to the current triangular face. To represent the first vertex of the current triangular face, its spatial coordinates are three-dimensional coordinates in the coal yard spatial coordinate system; To represent the second vertex of the current triangular face, its spatial coordinates are three-dimensional coordinates in the coal yard spatial coordinate system; To represent the third vertex of the current triangular face, its spatial coordinates are three-dimensional coordinates in the coal yard spatial coordinate system; To represent the projection point of the center point of the current triangular face after being vertically projected along the height direction of the coal yard onto the reference plane of the bottom of the coal pile, its horizontal position is consistent with the center point of the triangular face, and its height coordinate is equal to the height value of the reference plane of the bottom of the coal pile. For the second vertex of the triangle Pointing to the first vertex Spatial direction vector; For the third vertex of the triangle Pointing to the first vertex Spatial direction vector; To represent the projection point Pointing to the first vertex The spatial direction vector.

[0110] It should be noted that after obtaining the optimal passivation grid, since the optimal passivation grid has completed the smoothing of the sharp edge areas on the surface of the coal pile, it can more accurately represent the current external spatial morphology of the coal pile. Therefore, the volume calculation is performed based on this grid.

[0111] In the specific processing, firstly, all triangular facet information in the optimal passivation mesh is read, and then the three vertex numbers and corresponding spatial coordinates of each triangular facet are obtained sequentially. These spatial coordinates are all located in the previously established coal yard spatial coordinate system, including the length, width, and height positions of the coal pile. Subsequently, the height value of the coal pile bottom reference plane in the coal yard spatial coordinate system is determined. The coal pile bottom reference plane represents the bottom reference position of the actual coal pile accumulation area and serves as the reference boundary when calculating the spatial volume occupied by the coal pile.

[0112] It should be noted that the specific determination method is as follows: First, the bottom surface point cloud data of the coal yard under no-load conditions is read, and the height information of all bottom surface reference points is extracted; then, the heights of all bottom surface reference points are sorted, and abnormal height points caused by factors such as equipment foundations and ground debris are removed. The abnormal point removal method is as follows: all height values ​​are arranged in ascending order, and height values ​​in the first 5% and last 5% ranges are deleted. Then, the remaining height values ​​are statistically analyzed, and the average height is taken as the height value of the bottom surface reference plane of the coal pile.

[0113] When independent bottom surface measurement data is unavailable, the reference height of the bottom surface is determined based on the ground point cloud data of the uncovered area surrounding the coal pile. Specifically, ground point cloud data within a certain distance outside the coal pile's coverage area is extracted, and the point cloud height in this area is processed by removing outliers as described above to obtain the reference plane height of the coal pile's bottom surface.

[0114] Furthermore, after determining the height of the reference plane at the bottom of the coal pile, it is necessary to establish a corresponding spatial volume element for each triangular facet in the optimal passivation mesh. Specifically, the spatial coordinates of the three vertices of a given triangular facet are first read, and the spatial geometric range corresponding to that facet is determined based on the spatial relationship between the three vertices. For calculating the area of ​​the triangular facet, the lengths of the three sides between the three vertices are first determined, and then the actual surface area occupied by the facet is calculated based on the spatial relationship between the three sides. Subsequently, the center position of the facet is determined. Specifically, the coordinates of the three vertices in the length, width, and height directions are calculated together to obtain the spatial coordinates of the center point of the facet. This center point represents the average position of the current triangular facet in space.

[0115] After obtaining the coordinates of the center point of the triangular facet, project the center point vertically along the height direction of the coal yard onto the reference plane at the bottom of the coal pile. The specific projection method is as follows: Keeping the position of the center point unchanged in the horizontal direction, only its height coordinates are adjusted to the height value of the reference plane at the bottom of the coal pile, thereby obtaining the corresponding projection point coordinates.

[0116] Furthermore, after obtaining the three vertices of the triangular face and its central projection point, the three vertices of the triangular face are used as the three spatial vertices of the tetrahedron, and the projection point of the center point of the triangular face onto the bottom reference plane is used as the fourth vertex. These four spatial points together form a tetrahedral structure. Since the triangular facets on the coal pile surface are all located above the bottom reference plane, this tetrahedron can represent the spatial occupancy range of the area corresponding to the current triangular facet from the coal pile surface to the bottom surface.

[0117] Subsequently, the volume of each tetrahedron is calculated. In the specific calculation process, the spatial orientation of the tetrahedron is determined based on the positional relationship between the four vertices, and the oriented volume corresponding to that tetrahedron is calculated.

[0118] The oriented volume reflects the orientation of the tetrahedron's vertices. When the order of the triangular face vertices is consistent, the calculated directions of each tetrahedron remain consistent. However, when the orientation of the vertices of the local triangular faces is reversed, negative values ​​may occur. Therefore, in subsequent accumulation processes, it is necessary to process the volume according to its orientation, converting negative directional volumes into volumes that occupy the corresponding space.

[0119] After calculating the volume of the tetrahedron corresponding to a single triangular face, it is necessary to traverse all triangular faces in the optimal passivated mesh to obtain the spatial volume corresponding to the entire coal pile.

[0120] In specific processing, each triangle is read sequentially according to its index order in the optimal passivation mesh, and the following process is repeated: First, obtain the coordinates of the three vertices of the current triangle; Secondly, determine the projection point of the base surface based on the current center point of the triangle; Next, construct the corresponding tetrahedron based on the three vertices and the projection point, and calculate the directed volume of the tetrahedron. Finally, the oriented volume of the tetrahedron is converted into an absolute volume value and accumulated in the current coal pile volume calculation result.

[0121] After all the triangular faces have completed the above calculations, the current overall volume of the coal pile is obtained by accumulating all the local tetrahedral volumes.

[0122] During the accumulation process, to avoid redundant calculations due to overlapping projection regions of adjacent triangular faces, it is necessary to ensure that all triangular faces in the optimal passivated mesh have no intersecting connections. Since the aforementioned triangulation process has already ensured that each triangular face is connected only through a common edge, there is no overlapping coverage of the spatial region corresponding to each tetrahedron.

[0123] Furthermore, after obtaining the coal pile volume corresponding to the current inventory cycle, it is necessary to analyze the changes in coal storage in the coal yard by combining historical inventory results. Specifically, this involves first reading the coal pile volume data saved during the previous inventory process and obtaining the corresponding inventory time information. Then, the currently calculated coal pile volume is compared with the volume from the previous inventory.

[0124] Specifically, the difference between the two inventory volumes is calculated. When the current coal pile volume is greater than the previous inventory volume, it indicates that the amount of coal in the coal yard has increased, and the difference represents the newly added coal storage volume; when the current coal pile volume is less than the previous inventory volume, it indicates that there is a coal removal process in the coal yard, and the difference represents a decrease in the coal storage volume.

[0125] To avoid misinterpreting small-scale volume fluctuations caused by measurement errors as changes in coal storage, a volume change judgment threshold can be set. This threshold is determined based on historical stable inventory results: coal pile volume data is collected continuously for no less than 50 times. After confirming that there are no coal feeding or taking operations during the period, the range of change between two consecutive volume calculations is statistically analyzed, and the maximum change is used as the volume error threshold. When the current volume change is less than this threshold, it is considered a measurement fluctuation and not output as a dynamic change in coal storage. Finally, the effective difference between the current volume after error judgment and the previous volume is used as the dynamic change in coal storage volume to reflect the change in coal storage over time within the enclosed coal yard.

[0126] Through the above steps, a coal pile volume inventory process based on 3D point cloud, surface mesh reconstruction, and dynamic difference calculation is realized. Compared with directly using the original point cloud to calculate the volume, it can reduce the surface error caused by sharp edges of the angle of repose and improve the accuracy of dynamic inventory of coal storage volume in closed coal yards.

[0127] The above formulas are all dimensionless calculations. The formulas are derived from software simulations based on a large amount of collected data to obtain the most recent real-world results. The preset parameters in the formulas are set by those skilled in the art according to the actual situation.

[0128] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, in the form of a computer program product.

[0129] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software 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.

[0130] In addition, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0131] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0132] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for dynamic inventory of coal storage volume in a closed coal yard, characterized in that, Includes the following steps: Acquire 3D point cloud data of coal piles in the coal yard, and construct a triangulated mesh on the surface of the coal piles based on the 3D point cloud data; The variation of the angle between the normal vectors of adjacent triangular faces in the triangular mesh of the coal pile surface is analyzed, and sharp edges of the angle of repose are identified based on the analysis results. The sharp edges of the angle of repose are connected and aggregated to obtain the edge region. Based on the edge region, the triangular mesh of the coal pile surface is reconstructed by triangular facets to obtain several blunted meshes. The geometric skeleton of the connected region with normal deviation for each passivated mesh is extracted based on the angle of repose, and the optimal passivated mesh is selected based on the total length of the geometric skeleton. The current coal pile volume is calculated based on the optimal passivated grid, and the dynamic change in coal storage volume is obtained by combining the previous inventory volume.

2. The method for dynamic inventory of coal storage volume in a closed coal yard according to claim 1, characterized in that, The construction of the triangular mesh on the coal pile surface based on 3D point cloud data is specifically as follows: Construct a spatial coordinate system for the coal yard, and extract the spatial coordinates of all point clouds from the 3D point cloud data based on the spatial coordinate system for the coal yard; Calculate the spatial coverage of the entire point cloud on the horizontal plane, and divide the 3D point cloud data into several cubic voxel blocks according to the spatial location based on the spatial coverage. Extract the point cloud subset inside each cubic voxel block and perform plane fitting to obtain the fitting plane and fitting residual for each cubic voxel block; The cube voxel block with the smallest fitting residual is selected as the seed voxel block, and the fitting plane of the seed voxel block is used as the starting plane to expand outward layer by layer. Calculate the angle between the fitting plane of adjacent cubic voxels and the current expansion plane in turn, and include adjacent cubic voxels with an angle less than a preset angle threshold into the current expansion plane; The expansion process is repeated until no new cubic voxels meet the inclusion criteria. The 3D point cloud data inside all included cubic voxels are used as the vertex set, and the vertex set is triangulated to obtain the triangulated mesh of the coal pile surface.

3. The method for dynamic inventory of coal storage volume in a closed coal yard according to claim 1, characterized in that, The analysis of the variation of the angle between the normal vectors of adjacent triangular faces in the triangular mesh of the coal pile surface is as follows: Obtain the unit normal vectors of all triangular faces adjacent to each vertex of the triangulated mesh on the coal pile surface, and calculate the average of all unit normal vectors as the vertex normal vector of the vertex. Obtain the vertex normal vectors of the two endpoints of each common edge in the triangulated mesh on the surface of the coal pile, and calculate the first angle between the vertex normal vectors of the two endpoints. Iterate through all common edges in sequence, and form an angle sequence by arranging the first included angle value of each common edge in the order of the common edges; Mark all local maxima in the angle sequence, and take the common edge corresponding to the local maxima as the candidate edge.

4. The method for dynamic inventory of coal storage volume in a closed coal yard according to claim 3, characterized in that, The identification of sharp edges of the angle of repose based on the analysis results specifically includes: Starting from each candidate edge, trace the adjacent common edges that have continuously decreasing angle values ​​with the current candidate edge vector along the triangulation grid of the coal pile surface to both sides; Connect the adjacent common edges obtained from the tracking to form an edge trajectory segment; Perform a straightness check on each edge trajectory segment, and delete the edge trajectory segments based on the check results to obtain the remaining edge trajectory segments; The remaining edge trajectory segment is taken as the sharp edge of the angle of repose.

5. The method for dynamic inventory of coal storage volume in a closed coal yard according to claim 1, characterized in that, The process of connecting and aggregating the sharp edges of the resting angle to obtain the edge region is as follows: The sharp edges of the angle of rest are grouped according to their spatial distribution, and the spatial distance between the endpoints of every two sharp edges of the angle of rest is calculated. Two sharp edges of the resting angle with an endpoint spatial distance less than a preset distance threshold are marked as adjacent edges, and a connecting edge is established between the endpoints of the adjacent edges; By using connecting edges as links, all sharp edges of resting angles belonging to the same connected domain are aggregated into a single edge region.

6. The method for dynamic inventory of coal storage volume in a closed coal yard according to claim 5, characterized in that, The method of reconstructing triangular facets from the triangular mesh of the coal pile surface based on the edge region yields several passivated meshes, specifically: Extract the indices of all triangular faces that the sharp edges of the repose angle contained in each edge region pass through in the triangular mesh of the coal pile surface; Based on the index, all the triangular faces that have passed through are separated from the triangular mesh of the coal pile surface to obtain the edge region coverage mesh. The triangular faces in the mesh covering the edge region are simplified by edge folding to obtain the simplified triangular faces. The simplified triangular face after edge folding is spliced ​​with the triangular face that was not separated in the triangular mesh of the coal pile surface to obtain the initial reconstructed mesh. Using the edge region as the boundary constraint, the triangular facets are re-divided along the boundary line of the edge region in the initial reconstructed mesh, resulting in several blunted meshes.

7. The method for dynamic inventory of coal storage volume in a closed coal yard according to claim 1, characterized in that, The geometric skeleton of the connected region with normal deviation for each passivated mesh extracted based on the angle of repose is specifically as follows: Calculate the normal deviation angle between the unit normal vector and the vertical unit vector of each triangular face in each passivated mesh, and identify the deviated triangular face based on the normal deviation angle; Spatial connectivity clustering is performed on all deviation triangles within the same passivated mesh, and deviation triangles that are connected to each other through a common edge are clustered into the same normal deviation connected region. Extract the vertex coordinates of all triangular faces in each normal deviation connected region, and construct the region boundary of the normal deviation connected region based on the vertex coordinates; Remove boundary vertices layer by layer inward along the region boundary until the remaining vertices form a centerline structure with a single pixel width; The centerline structure is used as the geometric skeleton of the connected region of the normal deviation.

8. The method for dynamic inventory of coal storage volume in a closed coal yard according to claim 1, characterized in that, The process of selecting the optimal passivation mesh based on the total length of the geometric skeleton is as follows: Read all the geometric skeletons corresponding to each passivated mesh in sequence, and count the number of path segments contained in each geometric skeleton and the path length of each path segment respectively; The total number of path segments in the passivated mesh is obtained by summing the number of path segments in all geometric skeletons within the same passivated mesh, and the total length of the geometric skeleton in the passivated mesh is obtained by summing the lengths of each path segment in all geometric skeletons within the same passivated mesh. The total length of the geometric skeleton of all passivated meshes is normalized to obtain the normalized total length of each passivated mesh. At the same time, the total number of path segments of each passivated mesh is normalized to obtain the normalized number of path segments of each passivated mesh. Calculate the product of the normalized total length and the number of normalized path segments for each passivation grid to obtain the comprehensive evaluation value of each passivation grid, and select the passivation grid with the largest comprehensive evaluation value as the optimal passivation grid.

9. The method for dynamic inventory of coal storage volume in a closed coal yard according to claim 1, characterized in that, The calculation of the current coal pile volume based on the optimal passivated grid, combined with the previous inventory volume, yields the dynamic change in coal storage volume, specifically as follows: Obtain the coordinates of the three vertices of all triangular faces in the optimal passivation mesh, and determine the height of the reference plane at the bottom of the coal pile in the coal yard spatial coordinate system; Calculate the area and center point coordinates of the triangular face based on the coordinates of its three vertices, and then project the center point coordinates onto the reference plane at the bottom of the coal pile to obtain the coordinates of the projected point. Construct a tetrahedron using the coordinates of the three vertices and the projection point of the triangular face, and calculate the directed volume of the tetrahedron; The current coal pile volume is obtained by traversing all triangular faces in the optimal passivation mesh and accumulating the absolute value of the directed volume corresponding to each tetrahedron. Read the previous inventory volume record, calculate the difference between the current coal pile volume and the previous inventory volume, and use the difference as the dynamic change in coal storage volume.

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