Method and system for constructing polyhedron units for holographic simulation of irregular ballast particles

Abstract

The present invention provides a method and system for constructing polyhedral units of holographically simulated irregular ballast particles, which belongs to the technical field of railway ballasted track design. The method obtains three-dimensional images of ballast particles through holographic recording and wavefront reconstruction of holographic photography, obtains the three-dimensional geometric body of the ballast particles, and realizes high-fidelity restoration of the three-dimensional contour of the ballast particles. The virtual ballast particle three-dimensional projection platform and edge detection algorithm are used to extract the two-dimensional geometric outline of the ballast particles in each projection plane. Based on the parallel line rule, feature points for constructing polygons of various orders are selected or updated. The "plane reconstruction-spatial fusion" method is used to construct polyhedral units of various orders by finding the intersection of spatial geometric bodies. The random point sequence probability method is proposed to calculate the volume of polyhedral units of various orders, and the order of polyhedral units used for discrete element modeling is determined by volume similarity, thereby improving the simulation accuracy of the polyhedral units and realizing refined modeling of ballast particles of various shapes.

Description

Technical Field

[0001] The present invention relates to the technical field of railway ballasted track design, and in particular to a polyhedron unit construction method and system for holographically simulating irregular ballast particles. Background Art

[0002] The ballast track bed is a layered structure composed of compacted, angular, and variegated crushed stone ballast of a defined size and gradation. The shape and gradation of the ballast particles within the ballast bed are crucial for accurate ballast simulation and inter-particle force transmission. To realistically simulate the complex morphology of ballast particles, most studies have employed laser scanning and dual-plane mirror methods to obtain the three-dimensional contours of ballast particles. However, in practice, the laser scanning method requires multiple rotations and placements of the ballast particles, resulting in a time-consuming scanning process. The dual-plane mirror method also suffers from a complex algorithm for reconstructing the 3D contours of ballast particles, resulting in low efficiency.

[0003] In addition, most existing ballast particle simulations are based on the complex contours obtained by laser scanning or double-plane mirror methods, and are simulated with the help of combined spherical units (clumps). In essence, the contact between ballast particles in this simulation method is point contact between spheres, which cannot truly reflect the complex angular characteristics of ballast particles and the angular contact, angular contact and surface contact characteristics between flat ballast particles. In addition, when simulating ballast particles with combined spherical units (clumps), dozens of spherical units of different sizes are required for just one angular feature, which significantly increases the calculation time and cost of the ballasted track numerical model. Ballast particles are obtained by crushing natural blocks of various shapes, and their particle geometry is closer to a polyhedron with distinct angular features. Therefore, there are major defects in using combined spherical units (clumps) for simulation.

[0004] The three-view method and the plane mirror method are commonly used to generate polyhedral ballast particles, but both have shortcomings. For example, when using the three-view method to generate polyhedral ballast particles, the camera used to capture the three views requires three-dimensional calibration, which is complex to install and operate. While the dual-plane mirror method overcomes the shortcomings of the three-view method in camera calibration, the resulting 3D geometric model has a large number of points, edges, and faces on the surface, making it unsuitable for direct discrete element method calculations. Summary of the Invention

[0005] The object of the present invention is to provide a method and system for constructing polyhedron units for holographically simulating irregular ballast particles, so as to solve at least one technical problem existing in the above-mentioned background technology.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] In one aspect, the present invention provides a method for constructing polyhedral units for holographically simulating irregular ballast particles, comprising:

[0008] Obtain three-dimensional images of ballast particles through holographic recording and wavefront reconstruction using holographic imaging;

[0009] Using image processing technology to process the three-dimensional image of ballast particles to obtain the three-dimensional geometry of the ballast particles;

[0010] The virtual ballast particle 3D projection platform and edge detection algorithm are used to extract the 2D geometric outline of the ballast particle in each projection plane of the 3D geometric body of the ballast particle;

[0011] According to the principle that the two-dimensional ballast contour point is farthest from the coordinate axis, the first-order feature points are selected to construct the first-order quadrilateral, and the first-order polyhedral ballast particles are generated using the proposed "plane reconstruction-space fusion" method.

[0012] Update the feature points used to construct second-order and higher-order polygons according to the parallel line rule, and generate multi-order polyhedral ballast particle units by combining the "plane reconstruction-spatial fusion" method;

[0013] The volume of each order of polyhedral unit is obtained according to the random point sequence probability method, and the order of the polyhedral unit of the simulated ballast particles is determined by calculating the volume similarity between the two particles and the real ballast particles.

[0014] Preferably, obtaining a three-dimensional image of ballast particles by holographic recording and wavefront reconstruction using a holographic imaging method includes:

[0015] A typical ballast particle is selected and placed on the holographic photography platform; the laser, beam splitter, reflector, and beam expander are adjusted and calibrated, and photosensitive film is prepared; the light emitted by the laser is split into two beams by the beam splitter, recorded as object light and reference light respectively; the object light is projected onto the ballast particle via reflector II and beam expander I, and then reflected or transmitted by the ballast particle before being projected onto the photosensitive film; the reference light is directly projected onto the photosensitive film after passing through reflector I and beam expander II; the object light and reference light separated by the beam splitter are superimposed on each other, forming interference fringes on the photosensitive film; after development and fixing, a hologram of the ballast particle is obtained;

[0016] Using the principle of diffraction, a reproduced light beam with exactly the same wavelength and propagation direction as the reference light is used to illuminate the ballast particle hologram. The virtual image and real image of the original ballast particle can be seen along the direction of the original ballast particle shooting.

[0017] Preferably, the three-dimensional geometry of the ballast particles is obtained by means of image processing technology, including:

[0018] By using image processing and spatial geometry reconstruction algorithms, the three-dimensional contour spatial point information of the saved ballast particle real image is extracted; the three-dimensional point information is converted into a spatial three-dimensional ballast particle solid unit composed of triangular faces.

[0019] Preferably, the two-dimensional geometric outline of the ballast particles in each projection plane is extracted using a virtual ballast particle three-dimensional projection platform and an edge detection algorithm, including:

[0020] Taking the mass center of the virtual ballast particle as the coordinate origin, a spatial rectangular coordinate system is established;

[0021] Using the virtual ballast particle 3D projection platform, the generated ballast particle 3D geometric body is projected on each plane of the spatial rectangular coordinate system to obtain the top view, front view and side view respectively;

[0022] Each projection image is processed into a binary image through image preprocessing, and then processed using an edge detection algorithm to obtain a smooth two-dimensional ballast particle contour.

[0023] Preferably, first-order feature points are selected based on the principle that the two-dimensional ballast contour points are farthest from the coordinate axis, a first-order quadrilateral is constructed, and a "plane reconstruction-space fusion" method is used to generate first-order polyhedral ballast particles, including:

[0024] In the two-dimensional contour map of ballast particles obtained on each projection surface, find the four characteristic points farthest from the coordinate axis on the closed contour line along the coordinate axis, and record them as the first-order point sets 1-P1 = {a1, a2, a3, a4}, 1-P2 = {b1, b2, b3, b4} and 1-P3 = {c1, c2, c3, c4} respectively;

[0025] Connect the coordinate points in the three point sets end to end in a counterclockwise direction to reconstruct three first-order quadrilaterals, denoted as 1-S1, 1-S2, and 1-S3;

[0026] Three first-order quadrilaterals are stretched along their respective normal directions to obtain three first-order prisms, which are denoted as 1-V1, 1-V2 and 1-V3 respectively; then the first-order polyhedral ballast particle B1 is obtained according to the method of finding the intersection of spatial geometric bodies: B1 = 1-V1∩1-V2∩1-V3.

[0027] Preferably, the parallel line rule is used to update and construct the feature points of second-order and higher polygons, and combined with the "plane reconstruction-spatial fusion" method to generate multi-order polyhedral ballast particle units, including:

[0028] The process of extending the feature points by the parallel line rule: draw four parallel lines L1, L2, L3, and L4 parallel to the first-order quadrilateral 1-S1, respectively. 11 、L 12 、L 13 、L 14 ; L 11 、L 12 、L 13 、L 14It slowly moves in the direction away from the center of mass and intersects with the contour of the ballast particles; when the parallel line L 11 , L 12 , L 13 , L 14 When the distance d0 from the local convex boundary of the ballast particle contour on the projection surface is the largest, stop translation and record the coordinates of the feature points; based on the first-order point set, add coordinate points a5, a6, a7, and a8 to obtain the second-order point set 2-P1 = {a1, a2, a3, a4, a5, a6, a7, a8}; among them, only the intersection points of the parallel lines with d0 greater than 5% of the ballast particle size and the 2D ballast contour are updated. When the number of intersection points is greater than or equal to 2, update and add them according to 2 intersection points, and it is necessary to ensure that the intersection distance is greater than 5% of the ballast particle size; based on the second-order point set, add coordinate points a9, a10, a111, a12, a3, a4, a5, a6, a7, a8 10 、a 11 , we get the third-order point set 3-P1={a1,a2,a3,a4,a5,a6,a7,a8,a9,a 10 ,a 11};

[0029] Generation of second-order and higher polyhedral ballast units: The coordinate points in the three second-order point sets are connected end to end in a counterclockwise direction to reconstruct three second-order polygons, which are recorded as 2-S1, 2-S2 and 2-S3; the three second-order polygons are stretched along their respective normal directions to obtain three second-order prisms, which are recorded as 2-V1, 2-V2 and 2-V3 respectively; then, the second-order polyhedral ballast particles B2 are obtained by finding the intersection of spatial geometric bodies.

[0030] Preferably, the volume of each order of polyhedral unit is obtained by using the random point sequence probability method, and the order of the polyhedral unit of the simulated ballast particle is determined by calculating the volume similarity between the real ballast particle and the volume, including:

[0031] The volume of real ballast particles and polyhedral units of various orders is calculated using the random point sequence probability method: an external bounding box is generated outside the real ballast particles. The boundary of the external bounding box is determined by the maximum and minimum coordinates of the ballast particles in the three coordinate axes in the spatial rectangular coordinate system. The length of the external bounding box is recorded as L, the width is recorded as B, and the height is recorded as H. The volume of the external bounding box V 盒 The calculation formula is: V 盒 = L × B × H; enter a number of random points with low variance distribution in the external bounding box; determine whether the random points are located inside, on the contour line, or outside the 3D contour of the ballast particle; count the number of random points located inside, on the contour line, and outside the 3D contour of the ballast particle, and record them as N1, N2, and N3 respectively; then calculate the volume of the actual ballast particle VB j :

[0032]

[0033] Volume similarity calculation to obtain the order of ballast particles with a volume similarity greater than 90%: by calculating the ratio of the volume of each order polyhedral ballast particle unit to the volume of the real ballast particle, the volume similarity of polyhedral ballast particles of any order can be obtained:

[0034]

[0035] Where, ρ ij is the volume similarity of the i-th order polyhedral ballast particle unit corresponding to the j-th real ballast particle; VB i is the volume of the i-th order polyhedral ballast particle unit corresponding to the j-th real ballast particle;

[0036] Considering the calculation accuracy of the discrete element model of the granular roadbed, the polyhedral ballast particle unit with a volume similarity of 90% is taken as the optimal polyhedral unit for simulating the ballast particle morphology.

[0037] In a second aspect, the present invention provides a polyhedron unit construction system for holographically simulating irregular ballast particles, comprising:

[0038] An acquisition module, used for acquiring a three-dimensional image of ballast particles by holographic recording and wavefront reconstruction using a holographic imaging method;

[0039] A three-dimensional processing module is used to process the three-dimensional image of the ballast particles using image processing technology to obtain the three-dimensional geometry of the ballast particles;

[0040] An extraction module is used to extract the two-dimensional geometric profile of the ballast particles in each projection plane of the three-dimensional geometric body of the ballast particles using a virtual ballast particle three-dimensional projection platform and an edge detection algorithm;

[0041] The first construction module is used to select first-order feature points based on the principle that the two-dimensional ballast contour points are farthest from the coordinate axis, construct first-order quadrilaterals, and generate first-order polyhedral ballast particles using the proposed "plane reconstruction-spatial fusion" method;

[0042] The second construction module is used to update the feature points used to construct second-order and higher-order polygons according to the parallel line rule, and generate multi-order polyhedral ballast particle units in combination with the "plane reconstruction-spatial fusion" method;

[0043] The calculation module is used to obtain the volume of each order of polyhedral units according to the random point sequence probability method, and determine the order of the polyhedral units of the simulated ballast particles by calculating the volume similarity between the units and the real ballast particles.

[0044] In a third aspect, the present invention provides a non-transitory computer-readable storage medium for storing computer instructions. When the computer instructions are executed by a processor, the method for constructing polyhedral units of holographically simulated irregular ballast particles as described above is implemented.

[0045] In a fourth aspect, the present invention provides a computer program product, comprising a computer program, which, when executed on one or more processors, is used to implement the method for constructing polyhedral units of holographically simulated irregular ballast particles as described above.

[0046] In a fifth aspect, the present invention provides an electronic device comprising: a processor, a memory, and a computer program; wherein the processor is connected to the memory, and the computer program is stored in the memory. When the electronic device is running, the processor executes the computer program stored in the memory so that the electronic device executes instructions for implementing the polyhedral unit construction method of holographic simulation of irregular ballast particles as described above.

[0047] The beneficial effects of the present invention are as follows: three-dimensional images of ballast particles are obtained through holographic recording and wavefront reconstruction of the holographic imaging method, and the three-dimensional geometric body of the ballast particles is obtained with the help of image processing technology, thereby achieving high-fidelity restoration of the three-dimensional contour of the ballast particles; the two-dimensional geometric outline of the ballast particles in each projection plane is extracted using a virtual ballast particle three-dimensional projection platform and an edge detection algorithm, and then the feature points used to construct polygons of various orders are selected or updated with the help of the proposed parallel line rule, and the "plane reconstruction-space fusion" method is used to construct polyhedral units of various orders by finding the intersection of spatial geometric bodies to simulate real ballast particles; it is proposed to use the random point sequence probability method to calculate the volume of polyhedral units of various orders, and the order of the polyhedral units used for discrete element modeling is determined by the volume similarity, thereby achieving refined modeling of ballast particles of various shapes, improving the simulation accuracy of the polyhedral units, and providing strong support for the design and analysis of railway ballasted tracks.

[0048] Additional advantages of the present invention will be more clearly given in the following description or learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0050] Figure 1 This is a flow chart for constructing a polyhedral ballast particle unit according to an embodiment of the present invention.

[0051] Figure 2 Schematic diagram of the process of acquiring the three-dimensional profile hologram of ballast particles according to an embodiment of the present invention.

[0052] Figure 3 Schematic diagram of the process of reconstructing the three-dimensional contour wavefront of ballast particles according to an embodiment of the present invention.

[0053] Figure 4 Schematic diagram of the 3D geometric modeling process of ballast particles according to an embodiment of the present invention, wherein (a) is a holographic image of a ballast particle, and (b) is a 3D geometric body of the ballast particle.

[0054] Figure 5 This is a structural diagram of the three-dimensional projection platform for virtual ballast particles according to an embodiment of the present invention.

[0055] Figure 6 Schematic diagram of first-order feature point selection and plane reconstruction according to an embodiment of the present invention, where (a) is the first-order feature points of the front view of a quadrilateral, (b) is the first-order feature points of the side view of a quadrilateral, and (c) is the first-order feature points of the top view of a quadrilateral.

[0056] Figure 7 Schematic diagram of the process of generating first-order polyhedral ballast particles according to an embodiment of the present invention.

[0057] Figure 8 Schematic diagram of multi-order feature point selection and parallel line rule according to an embodiment of the present invention.

[0058] Figure 9 Schematic diagram of the process of generating second-order polyhedral ballast particles according to an embodiment of the present invention.

[0059] Figure 10 Schematic diagram of the volume calculation process using the random point sequence probability method according to an embodiment of the present invention.

[0060] Figure 11 Schematic diagram of the relationship between the volume similarity of polyhedral ballast particles and the order of polyhedral ballast particles according to an embodiment of the present invention.

[0061] Figure 12 Schematic diagram of different polyhedral ballast particle samples with a volume similarity exceeding 90% according to an embodiment of the present invention.

[0062] Wherein: 1-laser; 2-beam splitter; 3-reflector I; 4-reflector II; 5-beam expander lens I; 6-beam expander lens II; 7-actual ballast particle; 8-photographic film; 9-object light; 10-reference light; 11-laser beam; 12-hologram of ballast particle; 13-viewing angle; 14-virtual image of ballast particle; 15-real image of ballast particle. DETAILED DESCRIPTION

[0063] The embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention and are not to be construed as limiting the present invention.

[0064] Those skilled in the art will understand that unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which this invention belongs.

[0065] It should also be understood that terms, such as those defined in commonly used dictionaries, should be understood to have a meaning consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless as defined herein.

[0066] Those skilled in the art will appreciate that, unless otherwise stated, the singular forms "a," "an," "said," and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the stated features, integers, steps, operations, elements, and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, and / or groups thereof.

[0067] In the description of this specification, reference to the terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art may combine and integrate different embodiments or examples described in this specification, as well as features of different embodiments or examples, unless otherwise inconsistent.

[0068] To facilitate understanding of the present invention, the present invention is further explained below with reference to specific embodiments in conjunction with the accompanying drawings. However, the specific embodiments do not constitute a limitation on the embodiments of the present invention.

[0069] Those skilled in the art should understand that the drawings are merely schematic diagrams of embodiments, and the components in the drawings are not necessarily necessary for implementing the present invention.

[0070] Example 1

[0071] In this embodiment 1, a polyhedron unit construction system for holographically simulating irregular ballast particles is provided, comprising:

[0072] An acquisition module, used for acquiring a three-dimensional image of ballast particles by holographic recording and wavefront reconstruction using a holographic imaging method;

[0073] A three-dimensional processing module is used to process the three-dimensional image of the ballast particles using image processing technology to obtain the three-dimensional geometry of the ballast particles;

[0074] An extraction module is used to extract the two-dimensional geometric profile of the ballast particles in each projection plane of the three-dimensional geometric body of the ballast particles using a virtual ballast particle three-dimensional projection platform and an edge detection algorithm;

[0075] The first construction module is used to select first-order feature points based on the principle that the two-dimensional ballast contour points are farthest from the coordinate axis, construct first-order quadrilaterals, and generate first-order polyhedral ballast particles using the proposed "plane reconstruction-spatial fusion" method;

[0076] The second construction module is used to update and construct the feature points of second-order and higher polygons according to the parallel line rule, and generate multi-order polyhedral ballast particle units in combination with the "plane reconstruction-spatial fusion" method;

[0077] The calculation module is used to obtain the volume of each order of polyhedral units according to the random point sequence probability method, and determine the order of the polyhedral units of the simulated ballast particles by calculating the volume similarity between the units and the real ballast particles.

[0078] In this embodiment 1, the above-mentioned system is used to implement a method for constructing polyhedron units for holographically simulating irregular ballast particles, including:

[0079] Using the acquisition module, a three-dimensional image of the ballast particles is acquired through holographic recording and wavefront reconstruction using a holographic camera method;

[0080] Using the three-dimensional processing module, the three-dimensional image of the ballast particles is processed based on image processing technology to obtain the three-dimensional geometry of the ballast particles;

[0081] The extraction module is used to extract the two-dimensional geometric outline of the ballast particles in each projection plane of the three-dimensional geometric body of the ballast particles based on the virtual ballast particle three-dimensional projection platform and edge detection algorithm;

[0082] Using the first construction module, first-order feature points are selected based on the principle that the two-dimensional ballast contour points are farthest from the coordinate axis, and first-order quadrilaterals are constructed. The proposed "plane reconstruction-spatial fusion" method is used to generate first-order polyhedral ballast particles.

[0083] The second construction module is used to update and construct the feature points of second-order and higher polygons according to the parallel line rule, and the multi-order polyhedral ballast particle units are generated by combining the "plane reconstruction-spatial fusion" method;

[0084] The calculation module is used to obtain the volume of each order of polyhedral units according to the random point sequence probability method, and the order of the polyhedral units of the simulated ballast particles is determined by calculating the volume similarity between the simulated ballast particles and the real ballast particles.

[0085] Specifically, the holographic recording and wavefront reconstruction of holographic photography are used to obtain a three-dimensional image of the ballast particles. This technology has the advantage of recording all information, including light intensity, wavelength, and phase, at each point on the ballast particle, compared to conventional two-dimensional imaging, and can reproduce a realistic three-dimensional image of the ballast particles. The main steps are as follows:

[0086] (1) Holographic recording of ballast particles (hologram)

[0087] 1) Select typical ballast particles and place them on the holographic photography platform.

[0088] 2) Adjust and calibrate the laser, beam splitter, reflector, beam expander lens, and prepare the photosensitive film.

[0089] 3) The laser light is split into two beams by a beam splitter, designated as object light and reference light. The object light is projected onto the ballast particles via reflector II and beam expander I, and then reflected or transmitted by the ballast particles before being projected onto the photographic film.

[0090] 4) The reference light is directly projected onto the photosensitive film after passing through reflector I and beam expander II.

[0091] 5) The object and reference beams, separated by the beam splitter, are superimposed, forming interference fringes on the photosensitive film. After development and fixing, a hologram of the ballast particles is obtained. This hologram records all information about the morphological characteristics of the ballast particles.

[0092] (2) Ballast particle wavefront reconstruction

[0093] 1) Using the principle of diffraction, a reproduction light beam with the same wavelength and propagation direction as the reference light is used to illuminate the ballast particle hologram.

[0094] 2) The virtual image and real image of the original ballast particles can be seen along the direction in which the ballast particles were originally photographed and saved.

[0095] Specifically, the three-dimensional geometry of ballast particles is obtained by using image processing technology, and the steps are as follows:

[0096] (1) Using image processing and spatial geometry reconstruction algorithms, the three-dimensional contour spatial point information of the saved ballast particle real image is extracted.

[0097] (2) Convert the three-dimensional point information into a spatial three-dimensional ballast particle entity unit composed of triangular faces.

[0098] The 2D geometric outlines of the ballast particles within each projection plane were extracted using a virtual 3D ballast particle projection platform and edge detection algorithm. The main steps are as follows:

[0099] (1) Establish a spatial rectangular coordinate system with the center of mass of the virtual ballast particle as the coordinate origin.

[0100] (2) Using the virtual ballast particle three-dimensional projection platform, the generated ballast particle three-dimensional geometric body is projected along the XOY plane, YOZ plane and XOZ plane to obtain the top view, front view and side view respectively.

[0101] (3) Each projection image is processed into a binary image through image preprocessing, and then the edge detection algorithm is used to obtain a smooth two-dimensional ballast particle contour.

[0102] Based on the principle that the two-dimensional ballast contour point is farthest from the coordinate axis, the first-order feature points are selected, a first-order quadrilateral is constructed, and the first-order polyhedral ballast particles are generated using the proposed "plane reconstruction-space fusion" method. The main steps are as follows:

[0103] (1) Selection of first-order feature points: In the two-dimensional contour map of ballast particles obtained on each projection surface, the four feature points farthest from the coordinate axis are found on the closed contour line along the coordinate axis, and are recorded as the first-order point sets 1-P1 = {a1, a2, a3, a4}, 1-P2 = {b1, b2, b3, b4} and 1-P3 = {c1, c2, c3, c4} respectively.

[0104] (2) First-order quadrilateral reconstruction: Connect the coordinate points in the three point sets end to end in a counterclockwise direction to reconstruct three first-order quadrilaterals, which are denoted as 1-S1, 1-S2 and 1-S3.

[0105] (3) Spatial Fusion: Three first-order quadrilaterals are stretched along their respective normals to obtain three first-order prisms (the stretching length is three times the ballast particle diameter), which are denoted as 1-V1, 1-V2, and 1-V3, respectively. The first-order polyhedral ballast particle B1 is then obtained by finding the intersection of spatial geometric bodies using the following calculation formula.

[0106] B1=1-V1∩1-V2∩1-V3 (1)

[0107] The feature points used to construct second-order and higher-order polygons are updated with the help of the parallel line rule, and the multi-order polyhedral ballast particle units are generated by combining the "plane reconstruction-spatial fusion" method. The main steps are as follows:

[0108] (1) Update the feature points using the parallel line rule and construct a multi-order point set:

[0109] Due to the difference in morphology between first-order polyhedra and real ballast particles, in the actual simulation process, we will use the parallel line rule to extend the feature points on the basis of the first-order polyhedron to construct multi-order polyhedron units, making the ballast particle simulation more realistic. The process of extending the feature points using the parallel line rule is explained using the front view as an example, as follows:

[0110] 1) First, draw four parallel lines L1, L2, L3, and L4 parallel to the first-order quadrilateral 1-S1. 11 , L 12 , L 13 , L 14 .

[0111] 2) Then L 11 , L 12 , L 13 , L 14 It slowly moves away from the center of mass and intersects with the contour of the ballast particles. 11 , L 12 , L 13 , L 14 When the distance d0 from the local convex boundary of the ballast particle contour on the projection surface is the largest, the translation is stopped and the coordinates of the feature point are recorded.

[0112] 3) Based on the first-order point set, add coordinate points a5, a6, a7, and a8 to obtain the second-order point set 2-P1 = {a1, a2, a3, a4, a5, a6, a7, a8}. Other second-order point set generation methods are similar to the foresight method. Figure 2 The update method of the order point set is similar.

[0113] 4) A third-order point set can be generated using the same method as for the second-order point set. However, it is important to note that only the intersections of parallel lines with a d0 greater than 5% of the ballast particle size and the 2D ballast contour are updated and added. Furthermore, if the number of intersections is two or more, the update is considered two points, and the spacing between the intersections must be greater than 5% of the ballast particle size.

[0114] 5) Based on the second-order point set, add coordinate points a9, a 10 、a 11 , we get the third-order point set 3-P1={a1,a2,a3,a4,a5,a6,a7,a8,a9,a 10 ,a 11 Other third-order point set generation methods and forward-looking Figure 3 The update method of the order point set is similar.

[0115] 6) Point sets of third order or higher can be updated and generated by referring to the above steps.

[0116] (2) Generation of second-order and higher polyhedral ballast units:

[0117] 1) Connect the coordinate points in the three second-order point sets in a counterclockwise direction to reconstruct three second-order polygons, which are recorded as 2-S1, 2-S2 and 2-S3.

[0118] 2) The three second-order polygons are stretched along their normal directions to obtain three second-order prisms, denoted as 2-V1, 2-V2, and 2-V3. The second-order polyhedral ballast particle B2 is then obtained by finding the intersection of spatial geometric bodies.

[0119] 3) The generation process of polyhedral ballast particle units of the second order and above can be completed by referring to the above steps.

[0120] The proposed random point sequence probability method is used to obtain the volumes of polyhedral elements of various orders. The order of the polyhedral elements of the simulated ballast particles is determined by calculating the volume similarity between the elements and the real ballast particles. The main steps are as follows:

[0121] (1) Using the random point sequence probability method to calculate the volume of real ballast particles and polyhedral units of various orders: The calculation process of the volume of real ballast particles is explained as follows:

[0122] 1) Generate an external bounding box outside the real ballast particles. The boundary of the external bounding box is determined by the maximum and minimum coordinates of the ballast particles in the three coordinate axes in the spatial rectangular coordinate system. The length of the external bounding box is recorded as L, the width is recorded as B, and the height is recorded as H. The volume of the external bounding box is V 盒 The calculation formula is as follows:

[0123] V 盒 =L×B×H(2)

[0124] 2) Place a number of random points with low variance distribution within the bounding box. The number of random points should be sufficient.

[0125] 3) Determine whether the random point is inside, on or outside the 3D contour of the ballast.

[0126] 4) Count the number of random points inside, on and outside the three-dimensional contour of the ballast particles, and record them as N1, N2 and N3 respectively.

[0127] 5) The volume of the actual ballast particles VB can be calculated using formula (3): j The volume calculation method of other polyhedrons of different orders is consistent with the volume calculation process of real ballast particles.

[0128]

[0129] (2) Volume similarity calculation, obtain the ballast particle order with a volume similarity greater than 90%:

[0130] 1) By calculating the ratio of the volume of each order polyhedral ballast particle unit to the volume of the real ballast particle, the volume similarity of polyhedral ballast particles of any order can be obtained. The specific calculation formula is as follows:

[0131]

[0132] Where, ρ ij is the volume similarity of the i-th order polyhedral ballast particle unit corresponding to the j-th real ballast particle; VB i is the volume of the i-th order polyhedral ballast particle unit corresponding to the j-th real ballast particle.

[0133] 2) Considering the computational accuracy of the discrete element model for the granular roadbed, polyhedral ballast particle elements with a volume similarity of 90% were selected as the optimal polyhedral elements for simulating the ballast particle morphology. It should be noted that, provided that the volume similarity is greater than or equal to 90%, selecting the lowest-order polyhedral element can improve modeling efficiency.

[0134] In summary, in this embodiment 1, a polyhedral unit that is highly similar to any ballast particle shape can be quickly constructed, and the accuracy of numerical calculations can be guaranteed. The holographic imaging method can quickly obtain all the information of irregular ballast particles. Even when the ballast particle image is distorted or missing, the three-dimensional image of the ballast particles can be reproduced only by fragments, and the data reliability is high. The "plane reconstruction-spatial fusion" method can accurately generate polyhedral ballast particle units of any order, providing important support for the development of ballast particle simulation technology for ballasted track bulk trackbeds.

[0135] Example 2

[0136] See also Figure 1 As shown, in this embodiment 2, a method for constructing polyhedron units for holographically simulating irregular ballast particles is provided, comprising:

[0137] Holographic recording by holography (see Figure 2 ) and wavefront reconstruction (see Figure 3 ) obtaining a three-dimensional image of ballast particles;

[0138] The three-dimensional geometry of ballast particles is obtained by image processing technology (see Figure 4 );

[0139] The 2D geometric outlines of ballast particles in each projection plane are extracted using the virtual ballast particle 3D projection platform and edge detection algorithm (see Figure 5 );

[0140] According to the principle that the two-dimensional ballast contour point is farthest from the coordinate axis, the first-order feature points are selected to construct the first-order quadrilateral, and the first-order polyhedral ballast particles are generated using the proposed "plane reconstruction-space fusion" method (see Figure 6 and Figure 7 );

[0141] The proposed parallel line rule is used to update the feature points used to construct second-order and higher polygons, and the multi-order polyhedral ballast particle units are generated by combining the “plane reconstruction-space fusion” method (see Figure 8 and Figure 9 );

[0142] The volume of each order polyhedral unit is obtained by the proposed random point sequence probability method, and the order of the polyhedral unit of the simulated ballast particles is determined by calculating the volume similarity between the real ballast particles and the real ballast particles (see Figure 10 and Figure 11 ).

[0143] In this embodiment, holographic recording is performed by holographic imaging (see Figure 2 ) and wavefront reconstruction (see Figure 3 ) to obtain a three-dimensional image of the ballast particles. The advantage of this technology is that, compared with conventional two-dimensional imaging, it can record all information such as light intensity, wavelength, and phase at each point of the ballast particle, and can reproduce a realistic three-dimensional image of the ballast particles. The main steps are as follows:

[0144] (1) Holographic recording of ballast particles (hologram)

[0145] a. Select typical ballast particles 7 and place them on the holographic photography platform.

[0146] b. Adjust the calibration laser 1, beam splitter 2, reflector I 3, reflector II 4, beam expander lens I 5, beam expander lens II 6, and prepare the photosensitive film 8.

[0147] c. The laser light is split into two beams by a beam splitter, designated object light 9 and reference light 10. Object light 9 is projected onto ballast particles 7 via reflector II 4 and beam expander I 6. After being reflected or transmitted by the ballast particles, it is then projected onto photosensitive film 8.

[0148] d. The reference light 10 is directly projected onto the photosensitive film 8 after passing through the reflector I 3 and the beam expander II 6.

[0149] e. The object light 9 and reference light 10, separated by the beam splitter 2, are superimposed, forming interference fringes on the photosensitive film 8. After development and fixing, a hologram of the ballast particles is obtained. This hologram records all information about the morphological characteristics of the ballast particles.

[0150] (2) Ballast particle wavefront reconstruction

[0151] a. Using the principle of diffraction, a reproduction light beam 11 having the same wavelength and propagation direction as the reference light 10 is used to illuminate the ballast particle hologram.

[0152] b. The virtual image 14 and the real image 15 of the original ballast particle can be seen along the direction of the original ballast particle 7 and saved.

[0153] The three-dimensional geometry of the ballast particles was obtained with the help of image processing technology (see Figure 4 ), the specific steps are as follows:

[0154] a. Using image processing and spatial geometry reconstruction algorithms, extract the three-dimensional contour spatial point information of the saved ballast particle real image.

[0155] b. Convert the three-dimensional point information into a spatial three-dimensional ballast particle entity unit composed of triangular faces.

[0156] In this embodiment, the virtual ballast particle three-dimensional projection platform and edge detection algorithm are used to extract the two-dimensional geometric outline of the ballast particles in each projection surface (see Figure 5 ), the main steps are as follows:

[0157] a. Establish a spatial rectangular coordinate system with the center of mass of the virtual ballast particle as the coordinate origin.

[0158] b. Using the virtual ballast particle 3D projection platform, the generated ballast particle 3D geometry is projected along the XOY plane, YOZ plane, and XOZ plane to obtain the top view, front view, and side view, respectively.

[0159] c. Each projection image is processed into a binary image through image preprocessing, and then processed using an edge detection algorithm to obtain a smooth two-dimensional ballast particle outline.

[0160] In this embodiment, the first-order feature points are selected based on the principle that the two-dimensional ballast contour points are farthest from the coordinate axis, a first-order quadrilateral is constructed, and the first-order polyhedral ballast particles are generated using the proposed “plane reconstruction-space fusion” method (see 6 and Figure 7 The main steps are as follows:

[0161] (1) First-order feature point selection

[0162] In the two-dimensional contour of ballast particles obtained on each projection surface, the four characteristic points farthest from the coordinate axis are found on the closed contour line along the coordinate axis, which are recorded as the first-order point sets 1-P1 = {a1, a2, a3, a4}, 1-P2 = {b1, b2, b3, b4} and 1-P3 = {c1, c2, c3, c4}, respectively. Figure 6 .

[0163] (2) First-order quadrilateral reconstruction

[0164] Connect the coordinate points in the three point sets in a counterclockwise direction to reconstruct three first-order quadrilaterals, denoted as 1-S1, 1-S2 and 1-S3, see Figure 6 .

[0165] (3) Spatial fusion

[0166] The three first-order quadrilaterals are stretched along their normal directions to obtain three first-order prisms (the stretching length is three times the ballast particle diameter), which are recorded as 1-V1, 1-V2 and 1-V3 respectively. Then, the first-order polyhedron ballast particle B1 is obtained by the intersection method of the spatial geometric body. The calculation formula is as follows. For the specific process, see Figure 7 .

[0167] B1=1-V1∩1-V2∩1-V3(1)

[0168] In this embodiment, the proposed parallel line rule is used to update the feature points used to construct second-order and higher polygons, and the multi-order polyhedral ballast particle unit is generated by combining the “plane reconstruction-space fusion” method (see Figure 8 and Figure 9 The main steps are as follows:

[0169] (1) Update feature points using the parallel line rule and construct a multi-order point set

[0170] Due to the difference between the first-order polyhedron and the actual ballast particles, in the actual simulation process, based on the first-order polyhedron, the parallel line rule is used to extend the feature points to construct a multi-order polyhedron unit, so that the ballast particle simulation is more realistic. The front view is used as an example to illustrate the process of extending the feature points using the parallel line rule (see Figure 8 ), as follows:

[0171] a. First, draw four parallel lines L1, L2, L3, and L4 parallel to the first-order quadrilateral 1-S1. 11 、L 12 、L 13 、L 14 , see Figure 8 (b).

[0172] b. Then L 11 、L 12 、L 13 、L 14 It slowly moves away from the center of mass and intersects with the contour of the ballast particles. 11 、L 12 、L 13 、L 14When the distance d0 from the local convex boundary of the ballast particle contour on the projection surface is the largest, stop translation and record the coordinates of the feature point. Figure 8 (b) and Figure 8 (c).

[0173] c. Based on the first-order point set, add coordinate points a5, a6, a7, and a8 to obtain the second-order point set 2-P1 = {a1, a2, a3, a4, a5, a6, a7, a8}, see Figure 8 (b) Other second-order point set generation methods and foresight Figure 2 The update method of the order point set is similar, see Figure 8 (e) and Figure 8 (h).

[0174] d. According to the method of generating second-order point sets, third-order point sets can be generated. However, it should be noted that only the intersection points of parallel lines with d0 greater than 5% of the ballast particle size and the 2D contour of the ballast are updated. In addition, when the number of intersection points is greater than or equal to 2, it is updated and added as 2 intersection points, and the intersection spacing must be greater than 5% of the ballast particle size. See Figure 8 (c).

[0175] e. Based on the second-order point set, add coordinate points a9, a 10 、a 11 , we get the third-order point set 3-P1={a1,a2,a3,a4,a5,a6,a7,a8,a9,a 10 ,a 11}, see Figure 8 (c) Other third-order point set generation methods and foresight Figure 3 The update method of the order point set is similar, see Figure 8 (f) and Figure 8 (i).

[0176] f. Point sets of third order or higher can be updated and generated by referring to the above steps.

[0177] (2) Generation of second-order and higher polyhedral ballast units

[0178] a. Connect the coordinate points in the three second-order point sets in a counterclockwise direction to reconstruct three second-order polygons, denoted as 2-S1, 2-S2, and 2-S3, see Figure 9 .

[0179] b. Stretching the three second-order polygons along their normal directions yields three second-order prisms, denoted as 2-V1, 2-V2, and 2-V3. Then, the second-order polyhedral ballast particle B2 is obtained by finding the intersection of spatial geometric bodies, see Figure 9 .

[0180] c. The generation process of polyhedral ballast particle units of the second order and above can be completed by referring to the above steps.

[0181] In this embodiment, the volume of each order of polyhedral unit is obtained by using the proposed random point sequence probability method, and the order of the polyhedral unit of the simulated ballast particle is determined by calculating the volume similarity between the real ballast particle and the real ballast particle (see Figure 10 and Figure 11 The main steps are as follows:

[0182] (1) Calculate the volume of real ballast particles and polyhedral units of various orders using the random point sequence probability method

[0183] The calculation process of the actual ballast particle volume is explained as follows:

[0184] a. Generate an external bounding box outside the real ballast particles. The boundary of the external bounding box is determined by the maximum and minimum coordinates of the ballast particles in the three coordinate axes in the spatial rectangular coordinate system. Figure 10 The length of the bounding box is L, the width is B, and the height is H. The volume of the bounding box is V. 盒 The calculation formula is as follows:

[0185] V 盒 =L×B×H(2)

[0186] b. Insert several random points with low variance distribution into the outer bounding box, see Figure 10 The number of random points in this process must be sufficient.

[0187] c. Determine whether the random point is inside, on or outside the 3D contour of the ballast.

[0188] d. Count the number of random points inside, on, and outside the three-dimensional contour of the ballast particle, and record them as N1, N2, and N3 respectively.

[0189] e. The volume of the actual ballast particles VB can be calculated using formula (3) j The volume calculation method of other polyhedrons of different orders is consistent with the volume calculation process of real ballast particles.

[0190]

[0191] (2) Volume similarity calculation, obtaining the ballast particle order with a volume similarity greater than 90%

[0192] a. By calculating the ratio of the volume of each order polyhedral ballast particle unit to the volume of the real ballast particle, the volume similarity of polyhedral ballast particles of any order can be obtained. Figure 11 The specific calculation formula is as follows:

[0193]

[0194] Where, ρ ij is the volume similarity of the i-th order polyhedral ballast particle unit corresponding to the j-th real ballast particle; VB i is the volume of the i-th order polyhedral ballast particle unit corresponding to the j-th real ballast particle.

[0195] b. Considering the calculation accuracy of the discrete element model of the granular roadbed, the polyhedral ballast particle unit with a volume similarity of 90% is used as the optimal polyhedral unit for simulating the ballast particle morphology. Figure 11 It should be noted that, under the premise of satisfying the volume similarity rate greater than or equal to 90%, selecting the lowest-order polyhedral element can improve modeling efficiency.

[0196] In this embodiment, a polyhedron unit with a high degree of similarity to any ballast particle shape can be quickly constructed according to the shape of the ballast particle, and the accuracy of the numerical calculation can be guaranteed. Figure 12 shown.

[0197] In summary, the polyhedral unit construction method for holographically simulating irregular ballast particles provided in an embodiment of the present invention obtains a three-dimensional image of the ballast particles through holographic recording and wavefront reconstruction using a holographic camera method, obtains the three-dimensional geometry of the ballast particles with the help of image processing technology, and achieves high-fidelity restoration of the three-dimensional contours of the ballast particles. On this basis, the two-dimensional geometric contours of the ballast particles in each projection plane are extracted using a virtual ballast particle three-dimensional projection platform and an edge detection algorithm. Based on the principle that the two-dimensional ballast contour points are farthest from the coordinate axis, first-order feature points are selected to construct first-order quadrilaterals, and the proposed "plane reconstruction-spatial fusion" method is used to generate first-order polyhedral ballast particles. Then, the feature points used to construct polygons of various orders are updated with the help of the proposed parallel line rule. Combined with the "plane reconstruction-spatial fusion" method, second-order and higher polyhedral units are constructed to simulate real ballast particles. In order to improve the simulation accuracy of polyhedral elements, the random point sequence probability method was proposed to calculate the volumes of polyhedral elements of various orders, and the order of polyhedral elements used for discrete element modeling was determined by volume similarity. This achieved refined modeling of ballast particles of various shapes, enriched the ballast particle modeling methods, and provided strong support for the design and analysis of railway ballasted tracks.

[0198] Example 3

[0199] This embodiment 3 provides a non-transitory computer-readable storage medium for storing computer instructions. When the computer instructions are executed by a processor, the method for constructing polyhedral units of holographically simulated irregular ballast particles as described above is implemented. The method includes:

[0200] Obtain three-dimensional images of ballast particles through holographic recording and wavefront reconstruction using holographic imaging;

[0201] Using image processing technology to process the three-dimensional image of ballast particles to obtain the three-dimensional geometry of the ballast particles;

[0202] The virtual ballast particle 3D projection platform and edge detection algorithm are used to extract the 2D geometric outline of the ballast particle in each projection plane of the 3D geometric body of the ballast particle;

[0203] According to the principle that the two-dimensional ballast contour point is farthest from the coordinate axis, the first-order feature points are selected to construct the first-order quadrilateral, and the first-order polyhedral ballast particles are generated using the proposed "plane reconstruction-space fusion" method.

[0204] The parallel line rule is used to update the feature points of second-order and higher polygons, and the "plane reconstruction-spatial fusion" method is combined to generate multi-order polyhedral ballast particle units;

[0205] The volume of each order of polyhedral unit is obtained according to the random point sequence probability method, and the order of the polyhedral unit of the simulated ballast particles is determined by calculating the volume similarity between the two particles and the real ballast particles.

[0206] Example 4

[0207] This embodiment 4 provides a computer program product, including a computer program. When the computer program is executed on one or more processors, the computer program is used to implement the above-mentioned method for constructing polyhedral units of holographically simulated irregular ballast particles, the method comprising:

[0208] Obtain three-dimensional images of ballast particles through holographic recording and wavefront reconstruction using holographic imaging;

[0209] Using image processing technology to process the three-dimensional image of ballast particles to obtain the three-dimensional geometry of the ballast particles;

[0210] The virtual ballast particle 3D projection platform and edge detection algorithm are used to extract the 2D geometric outline of the ballast particle in each projection plane of the 3D geometric body of the ballast particle;

[0211] According to the principle that the two-dimensional ballast contour point is farthest from the coordinate axis, the first-order feature points are selected to construct the first-order quadrilateral, and the first-order polyhedral ballast particles are generated using the proposed "plane reconstruction-space fusion" method.

[0212] The parallel line rule is used to update the feature points of second-order and higher polygons, and the multi-order polyhedral ballast particle units are generated by combining the "plane reconstruction-spatial fusion" method;

[0213] The volume of each order of polyhedral unit is obtained according to the random point sequence probability method, and the order of the polyhedral unit of the simulated ballast particles is determined by calculating the volume similarity between the two particles and the real ballast particles.

[0214] Example 5

[0215] This embodiment 5 provides an electronic device, including: a processor, a memory, and a computer program; wherein the processor is connected to the memory, and the computer program is stored in the memory. When the electronic device is running, the processor executes the computer program stored in the memory to cause the electronic device to execute instructions for implementing the above-mentioned method for constructing polyhedral units of holographically simulated irregular ballast particles, the method including:

[0216] Obtain three-dimensional images of ballast particles through holographic recording and wavefront reconstruction using holographic imaging;

[0217] Using image processing technology to process the three-dimensional image of ballast particles to obtain the three-dimensional geometry of the ballast particles;

[0218] The virtual ballast particle 3D projection platform and edge detection algorithm are used to extract the 2D geometric outline of the ballast particle in each projection plane of the 3D geometric body of the ballast particle;

[0219] According to the principle that the two-dimensional ballast contour point is farthest from the coordinate axis, the first-order feature points are selected to construct the first-order quadrilateral, and the first-order polyhedral ballast particles are generated using the proposed "plane reconstruction-space fusion" method.

[0220] The parallel line rule is used to update the feature points of second-order and higher polygons, and the multi-order polyhedral ballast particle units are generated by combining the "plane reconstruction-spatial fusion" method;

[0221] The volume of each order of polyhedral unit is obtained according to the random point sequence probability method, and the order of the polyhedral unit of the simulated ballast particles is determined by calculating the volume similarity between the two particles and the real ballast particles.

[0222] It will be understood by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0223] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0224] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0225] These computer program instructions can also be loaded onto a computer or other programmable data processing device, and a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide the functions for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0226] Although the above describes the specific embodiments of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solutions disclosed in the present invention without the need for creative work should be included in the scope of protection of the present invention.

Claims

1. A method for constructing polyhedral units for holographic simulation of irregular ballast particles, characterized in that: include: Obtain three-dimensional images of ballast particles through holographic recording and wavefront reconstruction using holographic imaging; Using image processing technology to process the three-dimensional image of ballast particles to obtain the three-dimensional geometry of the ballast particles; The virtual ballast particle 3D projection platform and edge detection algorithm are used to extract the 2D geometric outline of the ballast particle in each projection plane of the 3D geometric body of the ballast particle; According to the principle that the two-dimensional ballast contour point is farthest from the coordinate axis, the first-order feature point is selected, the first-order quadrilateral is constructed, and the first-order polyhedron ballast particles are generated using the proposed "plane reconstruction-space fusion" method; including: in the two-dimensional contour map of the ballast particles obtained on each projection surface, the four feature points farthest from the coordinate axis are found on the closed contour line along the coordinate axis direction, and are recorded as the first-order point set 1-P1 = {a1, a2, a3, a4}, 1-P2 = {b1, b2, b3, b4} and 1 -P3={c1,c2,c3,c4}; connect the coordinate points in the three point sets end to end in a counterclockwise direction to reconstruct three first-order quadrilaterals, denoted as 1-S1, 1-S2, and 1-S3; stretch the three first-order quadrilaterals along their respective normal directions to obtain three first-order prisms, denoted as 1-V1, 1-V2, and 1-V3; then, obtain the first-order polyhedral ballast particle B1 according to the method of finding the intersection of spatial geometric bodies: B1=1-V1∩1-V2∩1-V3; The parallel line rule is used to update and construct the feature points of second-order and higher polygons, and the multi-order polyhedral ballast particle units are generated by combining the "plane reconstruction-space fusion" method; the process of extending the feature points by the parallel line rule includes: making four parallel lines L1, L2, L3, and L4 parallel to the first-order quadrilateral 1-S1 side respectively. 11 , L 12 , L 13 , L 14 ; L 11 , L 12 , L 13 , L 14 It slowly moves in the direction away from the center of mass and intersects with the contour of the ballast particles; when the parallel line L 11 , L 12 , L 13 , L 14 When the distance d0 from the local convex boundary of the ballast particle contour on the projection surface is the largest, stop translation and record the coordinates of the feature points; based on the first-order point set, add coordinate points a5, a6, a7, and a8 to obtain the second-order point set 2-P1 = {a1, a2, a3, a4, a5, a6, a7, a8}; among them, only the intersection points of the parallel lines with d0 greater than 5% of the ballast particle size and the 2D ballast contour are updated. When the number of intersection points is greater than or equal to 2, update and add them according to 2 intersection points, and it is necessary to ensure that the intersection distance is greater than 5% of the ballast particle size; based on the second-order point set, add coordinate points a9, a10, a111, a12, a3, a4, a5, a6, a7, a8 10 、a 11 , we get the third-order point set 3-P1={a1,a2,a3,a4,a5,a6,a7,a8,a9,a 10 ,a 11 }; The volume of each order of polyhedral unit is obtained according to the random point sequence probability method, and the order of the polyhedral unit of the simulated ballast particles is determined by calculating the volume similarity between the two particles and the real ballast particles.

2. The method for constructing polyhedron units for holographically simulating irregular ballast particles according to claim 1, characterized in that: The 3D images of ballast particles are obtained through holographic recording and wavefront reconstruction using holographic imaging, including: A typical ballast particle is selected and placed on the holographic photography platform; the laser, beam splitter, reflector, and beam expander are adjusted and calibrated, and photosensitive film is prepared; the light emitted by the laser is split into two beams by the beam splitter, recorded as object light and reference light respectively; the object light is projected onto the ballast particle via reflector II and beam expander I, and then reflected or transmitted by the ballast particle before being projected onto the photosensitive film; the reference light is directly projected onto the photosensitive film after passing through reflector I and beam expander II; the object light and reference light separated by the beam splitter are superimposed on each other, forming interference fringes on the photosensitive film; after development and fixing, a hologram of the ballast particle is obtained; Using the principle of diffraction, a reproduced light beam with exactly the same wavelength and propagation direction as the reference light is used to illuminate the ballast particle hologram. The virtual image and real image of the original ballast particle can be seen along the direction of the original ballast particle shooting.

3. The method for constructing polyhedron units for holographically simulating irregular ballast particles according to claim 2, characterized in that: The 3D geometry of the ballast particles is obtained using image processing technology, including: By using image processing and spatial geometry reconstruction algorithms, the three-dimensional contour spatial point information of the saved ballast particle real image is extracted; the three-dimensional point information is converted into a spatial three-dimensional ballast particle solid unit composed of triangular faces.

4. The method for constructing polyhedron units for holographically simulating irregular ballast particles according to claim 2, characterized in that: The virtual ballast particle 3D projection platform and edge detection algorithm are used to extract the 2D geometric profile of the ballast particles in each projection plane, including: Taking the mass center of the virtual ballast particle as the coordinate origin, a spatial rectangular coordinate system is established; Using the virtual ballast particle 3D projection platform, the generated ballast particle 3D geometric body is projected on each plane of the spatial rectangular coordinate system to obtain the top view, front view and side view respectively; Each projection image is processed into a binary image through image preprocessing, and then processed using an edge detection algorithm to obtain a smooth two-dimensional ballast particle contour.

5. The method for constructing polyhedron units for holographically simulating irregular ballast particles according to claim 1, characterized in that: The parallel line rule is updated to construct feature points of second-order and higher-order polygons. Combined with the "plane reconstruction-spatial fusion" method, multi-order polyhedral ballast particle units are generated, including: Generation of second-order and higher polyhedral ballast units: The coordinate points in the three second-order point sets are connected end to end in a counterclockwise direction to reconstruct three second-order polygons, which are recorded as 2-S1, 2-S2 and 2-S3; the three second-order polygons are stretched along their respective normal directions to obtain three second-order prisms, which are recorded as 2-V1, 2-V2 and 2-V3 respectively; then, the second-order polyhedral ballast particles B2 are obtained by finding the intersection of spatial geometric bodies.

6. The method for constructing polyhedron units for holographically simulating irregular ballast particles according to claim 5, characterized in that: The volume of each order of polyhedral unit is obtained by using the random point sequence probability method. The order of the polyhedral unit of the simulated ballast particles is determined by calculating the volume similarity between the two orders and the real ballast particles, including: The volume of real ballast particles and polyhedral units of various orders is calculated using the random point sequence probability method: an external bounding box is generated outside the real ballast particles. The boundary of the external bounding box is determined by the maximum and minimum coordinates of the ballast particles in the three coordinate axes in the spatial rectangular coordinate system. The length of the external bounding box is recorded as L, the width is recorded as B, and the height is recorded as H. The volume of the external bounding box V 盒 The calculation formula is: V 盒 = L × B × H; enter a number of random points with low variance distribution in the external bounding box; determine whether the random points are located inside, on the contour line, or outside the 3D contour of the ballast particle; count the number of random points located inside, on the contour line, and outside the 3D contour of the ballast particle, and record them as N1, N2, and N3 respectively; then calculate the volume of the actual ballast particle VB j : Volume similarity calculation to obtain the order of ballast particles with a volume similarity greater than 90%: by calculating the ratio of the volume of each order polyhedral ballast particle unit to the volume of the real ballast particle, the volume similarity of polyhedral ballast particles of any order can be obtained: Where, ρ ij is the volume similarity of the i-th order polyhedral ballast particle unit corresponding to the j-th real ballast particle; VB i is the volume of the i-th order polyhedral ballast particle unit corresponding to the j-th real ballast particle; Considering the calculation accuracy of the discrete element model of the granular roadbed, the polyhedral ballast particle unit with a volume similarity of 90% is taken as the optimal polyhedral unit for simulating the ballast particle morphology.

7. A polyhedron unit construction system for holographically simulating irregular ballast particles based on the polyhedron unit construction method for holographically simulating irregular ballast particles according to claim 1, characterized in that: include: An acquisition module, used for acquiring a three-dimensional image of ballast particles by holographic recording and wavefront reconstruction using a holographic imaging method; A three-dimensional processing module is used to process the three-dimensional image of the ballast particles using image processing technology to obtain the three-dimensional geometry of the ballast particles; An extraction module is used to extract the two-dimensional geometric profile of the ballast particles in each projection plane of the three-dimensional geometric body of the ballast particles using a virtual ballast particle three-dimensional projection platform and an edge detection algorithm; The first construction module is used to select first-order feature points based on the principle that the two-dimensional ballast contour points are farthest from the coordinate axis, construct first-order quadrilaterals, and generate first-order polyhedral ballast particles using the proposed "plane reconstruction-spatial fusion" method; The second construction module is used to update the feature points used to construct second-order and higher-order polygons according to the parallel line rule, and to generate multi-order polyhedral ballast particle units by combining the "plane reconstruction-spatial fusion" method; The calculation module is used to obtain the volume of each order of polyhedral units according to the random point sequence probability method, and determine the order of the polyhedral units of the simulated ballast particles by calculating the volume similarity between the units and the real ballast particles.

8. A non-transitory computer-readable storage medium, characterized in that The non-transitory computer-readable storage medium is used to store computer instructions. When the computer instructions are executed by the processor, the method for constructing polyhedral units of holographically simulated irregular ballast particles according to any one of claims 1 to 6 is implemented.

9. An electronic device, characterized in that: include: A processor, a memory, and a computer program; wherein the processor is connected to the memory, the computer program is stored in the memory, and when the electronic device is running, the processor executes the computer program stored in the memory to enable the electronic device to execute instructions for implementing the polyhedral unit construction method for holographic simulation of irregular ballast particles as described in any one of claims 1 to 6.

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