SYSTEM AND METHOD FOR AUTOMATIC CONTROL OF THE BALLAST VOLUME OF A RAILWAY TRACK

Abstract

SYSTEM AND METHOD FOR AUTOMATIC CONTROL OF THE BALLAST VOLUME OF A RAILWAY TRACK The invention relates to a method for automatically controlling the ballast volume of at least one section of railway track, the ballast being spread around the railway track in the form of a berm, characterized in that it comprises a step of acquiring at least one point cloud of the section of railway track and the terrain surrounding said at least one section of railway track, a step of extracting the rails (14) of the track to be studied from the point cloud, a step of creating a digital terrain model (200) of the section of railway track from the point cloud, a step of creating at least one theoretical ballast profile (36a, 36b, 36a, 36b') from predetermined standard data, and a step of calculating the conformity of the ballast volume with respect to the theoretical profile. Figure for the abstract: Figure 5

Description

Title of the invention: SYSTEM AND METHOD FOR AUTOMATIC CONTROL OF THE BALLAST VOLUME OF A RAILWAY TRACK Technical field of the invention

[0001] The invention relates to a method, a system and a computer program product for controlling the ballast volume of a section of railway track. In particular, the invention relates to a method for automating the calculation of ballast volume from data from 3D point clouds of the section of track and the surrounding terrain, for example acquired by LiDAR. Technological background

[0002] Railway ballast is a layer of stones and / or gravel laid along the path of a railway track and on which the railway sleepers and rails are placed. The purpose of ballast is, in particular, to hold the sleepers and rails in position when they are subjected to mechanical stresses during the passage of railway vehicles, to transfer and distribute these mechanical stresses to the ground, to facilitate the drainage of rainwater from the track, etc.

[0003] Despite its high resistance to mechanical and environmental stresses over time, ballast must be regularly inspected to ensure it continues to perform its main functions for safety reasons, and to plan for its replacement if necessary. Ballast inspection includes, in particular, checking its volume, which partly involves verifying the conformity of the ballast profile to railway standards that vary depending on the country, the type of railway track, and the nature of the railway vehicles using the track.

[0004] Currently, ballast inspection is generally visual and carried out by human maintenance operators based on expert judgment (without any specific measuring tools). It is therefore subject to variations in accuracy depending on the operator's perception, level of expertise, physical condition, level of attention, and the environmental (access to the area of ​​analysis) and climatic (fog, rain, etc.) conditions of the visual inspection. This type of inspection also requires a significant number of human resources and considerable organization for the supervision of kilometers of track (need for training, workload planning, etc.).

[0005] In addition, ballast maintenance requires knowledge of the volumes to be recovered in the event of a ballast volume exceeding the planned standards (ballast surplus), or added in the event of a ballast volume below the planned standards (ballast shortage).

[0006] While current monitoring and maintenance practices provide good safety results, the cost of this maintenance remains high due to the lack of an effective method for estimating the ballast volume on each section of track beforehand. In particular, the absence of a precise assessment of existing ballast volumes leads maintenance providers to favor ballasting operations (adding ballast) over track levelling operations (removing excess ballast). This approach, although initially implemented with safety in mind (to limit stress on the sleepers), results in additional costs in terms of raw materials (supply and addition of ballast) and also imposes new stresses on the trackbed (additional ballast mass), thus leading to accelerated degradation and the need for new ballast orders to compensate for trackbed defects.

[0007] A more precise knowledge of the ballast volume on a section of railway track could further facilitate ballast renewal work by allowing a better understanding of the volume of old ballast to be removed and the volume of new ballast to be delivered to the worksite. Currently, ballast volume measurements are carried out retrospectively by analyzing the quantities of ballast extracted by construction equipment.

[0008] The inventors therefore sought a solution to overcome the drawbacks of the visual controls of the prior art. Objectives of the invention

[0009] The invention aims to provide a method, a system and a computer program product for automatic control of the ballast volume of at least a portion of railway track.

[0010] The invention also aims to provide, in at least one embodiment, such a method, system and computer program product enabling automated evaluation of the volume of ballast to be replaced during railway track ballast renewal work.

[0011] The invention also aims to provide, in at least one embodiment, such a method, system and computer program product enabling automated evaluation of the ballast volume in order to assess a possible surplus or lack of ballast on a section of track.

[0012] The invention also aims to provide, in at least one embodiment, such a method, system and computer program product enabling a reduction in control costs and facilitating the management of delivery and stock of replacement ballast. Description of the invention

[0013] To this end, the invention relates to a method for automatically controlling the ballast volume of at least one section of railway track, the ballast being spread around the railway track in the form of a berm supported by a lower track, characterized in that it comprises: - a step of acquiring at least one 3D point cloud of the section of railway track and the terrain surrounding said at least one section of railway track, - a step of extracting the rail lines of the track to be studied from the point cloud, - a step involving the creation of a digital terrain model of the section of railway track and its surroundings from the point cloud, - a step of creating at least one theoretical ballast profile from representative data of predetermined ballast profile standards, - a step of calculating the conformity of the ballast volume with respect to the theoretical profile.

[0014] The method according to the invention thus enables the automation of ballast volume control on a section of railway track, using data from 3D point clouds of said section and the surrounding terrain. The volume is determined by comparison with a theoretical profile associated with predetermined ballast profile standards. These standards may be regulatory standards defined by the region or country in which the section of railway track is located, and / or industry standards, for example, related to current practice within the company responsible for installing the section of railway track, or related to specific calculations of mechanical / environmental and / or geological constraints on this section of railway track.

[0015] The railway track section corresponds to a portion of a railway line for which the ballast volume is checked, for example, for maintenance or replacement purposes. The railway line may be single (one track and two rails) or double (two tracks and four rails), or may include more tracks. The length of the railway track checked depends on the technical constraints for acquiring the point cloud, the maximum size of the point cloud, the length of track to be checked, etc. The length of track checked during implementation of the method can thus range from several tens of meters for a specific check to several tens or even hundreds of kilometers of railway track for general and recurring checks of an extensive railway network.

[0016] Prior knowledge of the volume makes it possible to simplify the distribution chain for ballast renewal, in particular to simplify the control of the ballast, its delivery, the organization of ballast stocks placed on the ground in preparation for the work (carried out using ballast pits).

[0017] Prior knowledge of the volume and comparison to standards also makes it possible to consider ballast maintenance without requiring complete renewal.

[0018] The data from at least one point cloud are preferably geolocated to allow possible matching with other geolocated data relating to the section of road studied.

[0019] The point cloud data can also be preprocessed to convert it into an easily usable and geometrically reliable format, for example a LAS or LAZ format (compressed LAS format). Preprocessing can also consist of combining several point clouds obtained in different ways into a single file.

[0020] Advantageously and according to the invention, the point cloud is obtained by a step of scanning each section of track by a LiDAR, and / or by a photogrammetry step from photographic images of each section of track.

[0021] According to this aspect of the invention, the use of LiDAR makes it possible in particular to obtain point clouds with significant accuracy for the generation of an accurate digital terrain model, while photogrammetry makes it possible in particular to work from photographic images that are simpler to obtain.

[0022] Advantageously and according to the invention, the point cloud acquisition step is carried out by a device mounted on a railway vehicle.

[0023] According to this aspect of the invention, the use of a railway vehicle simplifies image acquisition by driving directly on the section of railway track where ballast volume control is required. The device mounted on the railway vehicle is therefore preferably a LiDAR for obtaining the point cloud by scanning, or a camera for obtaining photographic images to form the point cloud by photogrammetry. In particular, the railway vehicle can be a track monitoring vehicle of the ESV type, which makes it possible to acquire a significant length of railway track in a single pass.

[0024] According to other variants of the invention, the acquisition of the point cloud can be done with other methods, for example by a LiDAR worn by a backpack, by taking aerial photographic images, etc.

[0025] Advantageously and according to the invention, the rail line extraction step includes a substep of identifying the points associated with each rail in the point cloud, and a substep of determining polylines representing the rail lines from the points associated with each rail.

[0026] Polylines, also called polygonal lines, are a combination of segments connecting points considered to be part of the same rail line of the railway track, each representing a rail line of the portion of railway track.

[0027] Advantageously and according to the invention, the step of creating the digital terrain model includes a sub-step of converting the point cloud into vertices forming the vertices of faces, preferably triangular, said faces being representative of the ground surface and the elements of the railway track laid on the ground.

[0028] Advantageously and according to the invention, the method comprises a step of detecting the toe of the ballast bench along at least one rail in the digital terrain model, the toe of the bench corresponding to the point of intersection between a slope of the ballast bench and the track on which the ballast rests, comprising: - a sub-step of cutting along a plane perpendicular to a rail line, so as to obtain a plurality of cuts distributed along the length of the rail line, each cut comprising a plurality of vertices of the digital terrain model, - a sub-step of dividing each cut into vertical strips according to a predetermined step, each vertical strip comprising a portion of the vertices, - a sub-step of determining, for each vertical band of the cross-section, the point with the lowest altitude value, - a sub-step of detecting, from the set of points in the cross-section with the lowest altitude value, a group of said points forming a slope profile and at least one group of said points forming a flat profile, - a sub-step of determining a point forming the foot of the bench for each section as the intersection of at least one flat profile and the slope profile, - a sub-step of smoothing, for all cuts, of the bench foot over the entire section of track.

[0029] According to this aspect of the invention, detecting the toe of the ballast bench is an optional step that allows for a better characterization of the general shape of the ballast bench, and in particular simplifies the calculation of the conformity of the ballast volume with respect to the theoretical profile by limiting the amount of data to be processed. Since the digital terrain model is extended to the entire ground surface around the section of railway track, determining the toe of the ballast bench allows for the elimination of data irrelevant to the ballast volume control by reducing the study window to the ballast bench without processing unnecessary data relating to the rest of the ground surface of the digital terrain model.

[0030] The foot of the bench is determined independently for each section made on the portion of track, and all the feet of the bench are taken into account to obtain a line of foot of the bench representative of the foot of the ballast all along the portion of track.

[0031] To limit the number of points to be processed, the method may advantageously include a step of filtering the digital terrain model data that are close to the rail line being studied, which is the rail line located on the side of the berm in the case of a double track, and of filtering the digital terrain model data that are far from the rail line and clearly outside the ballast berm. For example, points less than 50 cm from the rail line and more than 5 m from the rail line are removed from the points to be studied.

[0032] If no point is present in at least one vertical band of the section, linear interpolation can be used to add calculated points to the set of points in the section.

[0033] Advantageously and according to the invention, the step of creating at least one theoretical profile is further carried out from data representative of the type of sleeper and the type of profile of the ballast bench.

[0034] According to this aspect of the invention, the ballast volume corresponding to regulatory standards can vary depending on the type of sleeper and the type of profile of the ballast bank, and is therefore taken into account in the control of the ballast volume by creating a theoretical profile appropriate to the controlled portion of track.

[0035] Advantageously and according to the invention, the method includes a step of receiving data representative of predetermined ballast profile standards, data representative of the sleeper type and the ballast bench profile type from a centralized database grouping this data for a set of railway lines of which the railway track section is a part.

[0036] According to this aspect of the invention, a centralized database can enable the retrieval of data necessary for creating the theoretical profile. An example of such a database is the ARMEN database in France, which allows this data to be retrieved for a major part of the French railway network.

[0037] Advantageously and according to the invention, the method comprises a step of detecting the toe of the ballast bench along at least one rail in the digital terrain model, the toe of the bench corresponding to the point of intersection between a slope of the ballast bench and the track on which the ballast rests, comprising: - a sub-step of cutting along a plane perpendicular to a rail line, so as to obtain a plurality of cuts distributed along the length of the rail line, each cut comprising a plurality of vertices of the digital terrain model, - a sub-step of dividing each cut into vertical strips according to a predetermined step, each vertical strip comprising a portion of the vertices, - a sub-step of determining, for each vertical band of the cross-section, the point with the lowest altitude value, - a sub-step of detecting, from the set of points in the cross-section with the lowest altitude value, a group of said points forming a slope profile and at least one group of said points forming a flat profile, - a sub-step of determining a point forming the foot of the bench for each section as the intersection of at least one flat profile and the slope profile, - a sub-step of smoothing, for all cuts, of the bench foot over the entire section of track.

[0038] Advantageously and according to the invention, the step of creating at least one theoretical profile further includes a sub-step of removing, on the theoretical surface, points associated with an altitude lower than the altitude of the foot of the bench and points whose distance to the rail line is greater than the distance between the rail line and the foot of the bench.

[0039] According to this aspect of the invention, the bench foot allows in this context to filter out irrelevant data in order to limit the number of data to be processed.

[0040] Advantageously and according to the invention, the substep of determining each theoretical profile includes determining at least two theoretical profiles, by generating two theoretical surfaces, each having different predetermined inclination parameters.

[0041] According to this aspect of the invention, these two theoretical profiles make it possible in particular to delimit an interval corresponding to the maximum acceptable ballast volume and the acceptable ballast volume.

[0042] Advantageously and according to the invention, the step of calculating the conformity of the ballast volume with respect to the theoretical profile comprises: - a discretization sub-step along a longitudinal dimension to the rail and a lateral dimension to the rail, of each theoretical profile according to predefined steps, along the section of railway track, so as to obtain a set of points forming a grid of each theoretical profile, - a sub-step of determining, for each point of the grid, the point of the digital terrain model closest to said point of the grid, called the actual ballast point, - a sub-step for calculating the difference between the altitude of the grid point and the altitude of the associated actual ballast point, said difference being representative of a surplus or a shortage of ballast at that grid point, - a substep of adding a set of calculated differences corresponding to a plurality of points on the grid, so as to obtain a total ballast volume on the section of railway track.

[0043] According to this aspect of the invention, this step makes it possible to precisely control the ballast volume over the entire surface surrounding the section of railway track, at each point of the grid, and more generally over a portion or the entire surface to be controlled by adding the volumes calculated at a plurality of points on the grid. The method can thus make it possible, for example, to obtain an estimate of the ballast volume, its surplus or deficit per kilometer of railway track for control over long distances.

[0044] Advantageously and according to the invention, the step of calculating the conformity of the ballast volume with respect to the theoretical profile comprises: - a sub-step for detecting excess ballast if the altitude of the actual ballast point is greater than the altitude of the associated grid point of all theoretical profiles, - a sub-step for detecting a lack of ballast if the altitude of the actual ballast point is lower than the altitude of the associated grid point of all theoretical profiles, - a sub-step for detecting conformity of the ballast volume if the altitude of the actual ballast point is between the altitude of the grid point associated with a first theoretical profile and the altitude of the grid point associated with a second theoretical profile.

[0045] The invention also relates to an automatic ballast volume control system for at least a section of railway track, the ballast being extended around the railway track in the form of a berm supported by a lower track, characterized in that it comprises: - a module for acquiring at least one point cloud of the section of railway track and the terrain surrounding said section of railway track, - a module for extracting the rail lines of the track to be studied from the point cloud, - a module for creating a digital terrain model of the section of railway track and its surroundings from the point cloud, - a module for creating at least one theoretical ballast profile from representative data of predetermined ballast profile standards, - a module for calculating the conformity of the ballast volume with respect to the theoretical profile.

[0046] The technical effects and advantages of the process according to the invention apply mutatis mutandis to the system according to the invention.

[0047] The processing unit of the system according to the invention includes, for example, a computer device which must be understood in a broad sense (computer, plurality of computers, virtual server on the internet, virtual server on the Cloud, virtual server on a platform, virtual server on a local infrastructure, server networks, etc.).

[0048] Throughout this text, the term "module" refers to a software element, a subset of a software program that can be compiled separately, either for independent use or for assembly with other program modules, or a hardware element, or a combination of a hardware element and a software subprogram. Such a hardware element may include an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a digital signal processor (DSP), or any equivalent hardware or combination thereof. Generally speaking, a module is therefore an element (software and / or hardware) that performs a function.

[0049] Advantageously, the automatic control system according to the invention is configured to implement the automatic control method according to the invention.

[0050] Advantageously, the automatic control method according to the invention is configured to be implemented by the automatic control system according to the invention.

[0051] The invention also relates to a computer program product for the automatic control of the ballast volume of at least a section of railway track, the ballast being spread around the railway track in the form of a berm supported by a lower track, said computer program product being characterized in that it comprises program code instructions for the execution, when said computer program product is run on a computer, of the steps of a method comprising: - a step of acquiring at least one point cloud of the section of railway track and the terrain surrounding said at least one section of railway track, - a step of extracting the rail lines of the track to be studied from the point cloud, - a step involving the creation of a digital terrain model of the section of railway track and its surroundings from the point cloud, - a step of creating at least one theoretical ballast profile from representative data of predetermined ballast profile standards, - a step of calculating the conformity of the ballast volume with respect to the theoretical profile.

[0052] Advantageously, the automatic control system according to the invention is configured to execute the automatic control computer program product according to the invention.

[0053] Advantageously, the automatic control computer program product according to the invention is configured to be executed by one or more modules of the automatic control system according to the invention.

[0054] Advantageously, the automatic control computer program product is configured to execute the steps of the automatic control process according to the invention. List of figures

[0055] Other objects, features and advantages of the invention will become apparent from the following description, given by way of non-limiting example only, and which refers to the accompanying figures in which: • Fig. 1 is a schematic cross-sectional view of a section of railway track, • Figure [Fig. 2] is a schematic view of a method for automatically controlling the ballast volume according to one embodiment of the invention. • [Fig. 3] is a schematic cross-sectional view of a section of railway track as represented in a digital terrain model as created during the execution of an automatic ballast volume control process according to an embodiment of the invention, • Figure 4 is a schematic cross-sectional view of a section of railway track in which the dimensional parameters of the ballast are visible. • Figure 5 is a schematic perspective view of a digital terrain model as created during the execution of an automatic ballast volume control process according to an embodiment of the invention. • Figure 6 is a schematic cross-sectional view of a section of railway track in which are visible the dimension parameters of the ballast and theoretical profiles as created during the execution of a process automatic control of ballast volume according to an embodiment of the invention.

[0056] Detailed description of an embodiment of the invention

[0057] In the figures, the scales and proportions are not strictly respected for the purposes of illustration and clarity.

[0058] Identical, similar or analogous elements are designated by the same references in all figures.

[0059] Figure 1 schematically illustrates in cross-section a section 10 of railway track. Section 10 of railway track comprises two running tracks: a first running track 12a formed of two rails 14a and 14b, and a second running track 12b formed of two rails 16a and 16b. The rails 14a and 14b of the first running track 12a are supported by a sleeper 18a, and the rails 16a and 16b of the second running track 12b are supported by a sleeper 18b.

[0060] The railway track also includes ballast, arranged in the form of a ballast bench 20 supporting and surrounding the sleepers 18a and 18b of the section of track. The name "bench" refers to its particular shape, forming a trapezoidal cross-section when laid on the track. The ballast is, as is known, made up of layers of stones and / or gravel and, in particular, helps to hold the sleepers and rails in position when they are subjected to mechanical stresses during the passage of railway vehicles. The materials used to form the ballast depend, in particular, on the surface area supporting the ballast and the geographical area in which the railway track is located, especially regarding the ease of local supply given the quantity required. The ballast bench 20 is supported by a lower track 22 formed, for example, in this embodiment, of a sub-layer 24 and a subgrade layer 26.The section of railway track may include other elements, for example a longitudinal drainage device 27.

[0061] The ballast bench 20 is characterized in particular by a bench foot which corresponds to the point of intersection between a slope of the ballast bench and the track on which the ballast rests. In this embodiment, the ballast bench 20 comprises a first bench foot 28a and a second foot 28b, at the intersections between the two slopes of the bench with the sub-layer 24 on which the ballast rests.

[0062] Figure 2 schematically illustrates a method for automatically controlling the ballast volume of at least one section of railway track, according to an embodiment of the invention. In particular, the method can be applied to a section of railway track as described with reference to Figure 1.

[0063] The method 100 includes, in particular, a step 110 of acquiring at least one point cloud of the railway track section and the terrain surrounding said at least one railway track section. The point clouds can, in particular, be acquired by track monitoring vehicles (TMVs) equipped with LiDAR, which travel along the railway track containing the section of track to be monitored. These point clouds are thus representative of the track condition at the given moment when the data was captured. The point clouds contain the topographic and geometric characteristics of the various track elements such as ballast, rails, platforms, catenary masts, etc. This data is also preferably geolocated with an accuracy on the order of a few centimeters, 5 centimeters on average.The point cloud can also be obtained through a photogrammetry step using photographic images of each section of track.

[0064] The method 100 can also subsequently include a preprocessing step 112 for each point cloud. This step makes the point cloud more usable and geometrically reliable, for example by converting the point cloud data into a LAS (.las) or LAZ (.laz) format, or for example by combining several point clouds into a single point cloud.

[0065] The method 100 then includes a step 114 of extracting the rail lines of the track to be studied from the point cloud. This step 114 includes in particular a substep 114a of identifying the points associated with each rail in the point cloud, and a substep 114b of determining polylines representing the rail lines from the points associated with each rail.

[0066] This extraction consists of identifying the precise position of the rails of each track present in a point cloud. This information is then presented as a number of polylines equal to the number of tracks in the cloud, distinguishing between the right and left rails. The coordinates of the vertices relative to the rails can then be used as references to perform geometric calculations to manipulate the points in the cloud.

[0067] The method 100 then includes a step 116 of creating a digital terrain model of the section of railway track and its surroundings from the point cloud, optionally after preprocessing. This step 116 includes a substep 116a of converting the point cloud into vertices forming the vertices of polygonal faces, preferably triangular, said polygonal faces being representative of the ground surface and the elements of the railway track laid on the ground.

[0068] The digital terrain model, also known by its abbreviation DTM, takes into account only the geometry of the elements on the ground, therefore including the ballast, and thus represents the ground surface in the form of a triangular mesh. This data format facilitates the volumetric study of the ballast.

[0069] The method 100 then includes an optional step 118 of detecting the toe of the ballast bench along at least one rail in the digital terrain model, the toe of the bench corresponding to the point of intersection between a slope of the ballast bench and the track on which the ballast rests. Detecting the toe of the bench makes it possible to work on the same study area between the theoretical profiles described below and the data of the digital terrain model.

[0070] Step 118 for detecting the base of the bench includes, in particular, a substep 118a of cutting along a plane perpendicular to a rail line, so as to obtain a plurality of cuts distributed along the length of the rail line, each cut comprising a plurality of vertices of the digital terrain model. An example of these cuts is shown schematically in [Fig. 3]. Each cut is obtained, for example, by retrieving the points located five meters on either side of the rail extraction 14a, and then by filtering the points of the cut that are more than five meters and less than fifty cm from the rail line 14a on the side where the base of the bench 28a is located, so as to reduce the number of points to be processed.

[0071] Step 118 of detecting the foot of the bench then includes a substep 118b of dividing each cut into vertical strips 30 according to a step of predetermined value d, for example ten centimeters, each vertical strip comprising a part of the vertices, as seen in [Fig.3].

[0072] Step 118, which detects the base of the bench, then includes a substep 118c for determining, for each vertical band 30 of the section, the point with the lowest elevation value. If no point is detected in the vertical band, a value can be assigned to it, for example (-1; -1). If the first lowest points have negative coordinates, detection of the base of the bench may not be possible, and the process 110 continues to the next step without knowledge of the base of the bench.

[0073] The coordinates of missing points can be extrapolated linearly from the points with the lowest altitude value on the adjacent bands.

[0074] Step 118, which detects the base of the bench, then includes a substep 118d for detecting, from the set of points in the cross-section with the lowest elevation value, a group of said points forming a slope profile and at least one group of said points forming a flat profile. In particular, the step generally allows for the detection of two flat profiles: a first flat profile 32a at the level of the rail and a second flat profile 32b after the base of the bench, separated by the slope profile 34.

[0075] Substep 118d includes, in particular: - a traverse of all the lowest points after interpolation as long as a flat profile is detected. Two points are considered to represent a flat profile if the difference in their altitude does not exceed one-third of the step. - once out of the first flat profile, we iterate at the level of the slope profile until we re-identify a flat profile. - if three consecutive points have a flat profile, we consider that the foot of the bench has been found.

[0076] If the bench foot detection fails, the bench foot is declared to be fifty centimeters from the rail line on the bench side with an altitude of -1 to recognize the points affected by default.

[0077] Step 118 of detecting the foot of the bench then includes a substep 118e of determining a point forming the foot of the bench for each section as the intersection of at least one flat profile and the slope profile.

[0078] Step 118 of detecting the foot of the bench then includes a substep 118f of smoothing, for all the sections, the foot of the bench over the entire portion of track detected on each section.

[0079] Alternatively, bench detection can be carried out using a learning model previously trained to detect bench foot, either from the sections or directly on the complete digital terrain model.

[0080] The process 100 then includes a step 120 of creating at least one theoretical ballast profile from data representative of predetermined ballast profile standards. Preferably, two theoretical profiles are created, as described below and shown in [Fig. 3], representing a first theoretical profile 36a and a second theoretical profile 36b. Each theoretical profile is a ballast bench profile calculated from the railway standards applied in the territory in question.

[0081] This step 120 is further performed using representative data of the sleeper type and the ballast berm profile type. To this end, the method includes a step 122 of receiving representative data of predetermined ballast profile standards, representative data of the sleeper type and the ballast berm profile type from a centralized database that compiles this data for a set of railway lines, including the section of track in question. This centralized database is, for example, a database that inventories the various current characteristics of the track elements along its entire length and details the types of ballast profiles, rail materials, and sleepers on each of the homogeneous sections resulting from maintenance and renewal work. In this system, ballast profiles and sleeper types are primarily used.

[0082] There are many types of sleepers: Concrete Bibloc, Monobloc, Wood, Metal, etc. The type of sleeper will mainly allow the definition of the different points defining the theoretical profile, called here starting points, high points and low point.

[0083] The ballast profile can also be of different types, for example three types of profiles: solid profile, reinforced profile or super reinforced profile depending on the characteristics of the track, the terrain, the curvature, the railway vehicles using it, etc.

[0084] Figure 4 schematically illustrates a cross-section of a section of railway track as represented in a digital terrain model, showing these different points. Taking into account the bearing (the inclination between the left and right rails), these points are calculated using the applicable standards for each profile.

[0085] Step 120 of creating at least one theoretical profile thus includes a substep 120a of determining a set of starting points A of the bench, at the level of at least one sleeper 18a carrying the rail 14a, the points being distributed along the portion of railway track.

[0086] Step 120 of creating at least one theoretical profile then includes a substep 120b of determining a set of high points B of the bench, the surface defined by the starting points A and the high points B forming a flat profile of the ballast bench, characterized by its dimensions X and Y. These points depend on the type of sleeper and the bench profile.

[0087] Step 120 of creating at least one theoretical profile then includes a substep 120c of determining each theoretical profile by generating a theoretical surface representative of a theoretical slope profile of the ballast bench, from the set of high points and predetermined inclination parameters of the theoretical surface as a function of standard data. In particular, two theoretical profiles can be created by varying the inclination parameters w and z corresponding respectively to the slope height and slope width, in particular: - a first profile 36a called profile 3 / 1 with a ratio z / w=3 / l, for example z = 6m and w=2m. - a second profile 36b called profile 3 / 2 with a ratio z / w=3 / 2, for example z = 6m and w=4m.

[0088] Step 120 of creating at least one theoretical profile may also include a substep 120d of removing, from the theoretical surface, points associated with an altitude lower than the elevation of the foot of the bench and points whose distance from the rail line is greater than the distance between the rail line and the foot of the bench. The low point C thus corresponds to a point on the profile whose altitude is equal to the foot of the bench and whose distance from the rail line is less than the foot of the bench. The profile is thus corrected with the foot of the bench. The altitude of point C of the theoretical profiles cannot be lower than the altitude of the foot of the bench and cannot be further from the tracks than the foot of the bench in order to have an equivalent study area on the real and theoretical.

[0089] The theoretical profiles generated point by point from rail extraction will allow the generation of the 3D geometry mesh of the theoretical ballast bench profiles, primarily using Delaunay triangulation. This mesh can then be included in the digital terrain model to obtain a model such as that shown in [Fig. 5], illustrating in perspective a digital terrain model as created during the execution of an automatic ballast volume control process according to an embodiment of the invention.

[0090] On the model are visible the surface 202 of the terrain, the 14 rail lines, the 28 lines formed by the set of bench feet on each side of the ballast, the first theoretical profiles 36a and 36a' on each side of the ballast and the second profiles 36b and 36b' on each side of the ballast.

[0091] The process 100 then includes a step 124 of calculating the conformity of the ballast volume with respect to the theoretical profile.

[0092] This step 124 of calculating the conformity of the ballast volume includes a substep 124a of discretization according to a longitudinal dimension to the rail line and a lateral dimension to the rail line, of each theoretical profile according to predefined steps, along the portion of railway track, so as to obtain a set of points forming a grid of each theoretical profile.

[0093] This step 124 for calculating the conformity of the ballast volume then includes a substep 124b for determining, for each point on the grid, the point in the digital terrain model closest to said point on the grid, referred to as the actual ballast point. Preferably, this step includes searching for the nearest point in the discretized DEM data located within 20 cm.

[0094] This step 124 of calculating the conformity of the ballast volume then includes a substep 124c of calculating the difference between the altitude of the grid point and the altitude of the associated actual ballast point, said difference being representative of a surplus or a lack of ballast at the level of this grid point,

[0095] This step 124 for calculating the conformity of the ballast volume then includes a substep 124d for adding a set of calculated differences corresponding to a plurality of grid points, so as to obtain a total ballast volume on the section of railway track. Preferably, this substep includes, by iterating over each rail point, a calculation of the volume meter by meter by adding the volumes of the discrete elements around the rail point to obtain volumes per kilometer point.

[0096] In particular, step 124 of the ballast volume conformity calculation includes: - a sub-step 124e for detecting excess ballast if the altitude of the actual ballast point is greater than the altitude of the associated grid point of all theoretical profiles, - a sub-step 124f for detecting a lack of ballast if the altitude of the actual ballast point is lower than the altitude of the associated grid point of all theoretical profiles, - a sub-step 124g of detecting conformity of the ballast volume if the altitude of the actual ballast point is between the altitude of the grid point associated with a first theoretical profile and the altitude of the grid point associated with a second theoretical profile.

[0097] For example, in the described embodiment, for the quantity of ballast to be compliant, the actual ballast profile must be between the theoretical profiles 3 / 1 and 3 / 2. Such a compliant profile is shown with reference to [Fig. 6], which schematically illustrates in cross-section a section of railway track in which the dimension parameters of the ballast and theoretical profiles are visible, as created during the execution of an automatic ballast volume control method according to an embodiment of the invention. The ballast profile 40 is here situated between the first theoretical profile 36a and the second theoretical profile 36b.

[0098] The theoretical 3 / 2 profile will thus provide the minimum possible ballast, and the theoretical 3 / 1 profile will provide the maximum. Beyond the 3 / 1 profile, there will be a surplus of ballast, and below the 3 / 2 profile, there will be a ballast deficit.

[0099] Furthermore, in this embodiment: - If the sum of the ballast volumes calculated between the DEM data, profile 3 / 1 and profile 3 / 2 is negative for both profiles, there is a deficit; - If the sum of the ballast volumes calculated between the DEM data for profile 3 / 1 is negative but positive for 3 / 2, the quantity of ballast is satisfactory. - if the sum of the ballast volumes calculated for the two profiles is positive, there is a surplus of ballast.

[0100] Thus, estimating the ballast cross-section requires knowledge of the ballast profile. LiDAR data provides topographic information prior to the renovation work, and ballast profiles are automatically extracted from this data. The measured profile is compared to the standard profile to estimate the excess ballast. Ideally, this excess should be removed before the renewal work and recycled to optimize the efficiency of the ballast renewal machine.

[0101] The invention is not limited to the embodiments described. In particular, the generated data (Digital Terrain Models and rail extraction) can also be generated in different ways; the digital terrain model can be used for the detection of elements such as ballast by pre-trained machine learning or deep learning methods.

Claims

1. Demands Method for automatically controlling the ballast volume of at least one section of railway track (12a, 12b), the ballast being extended around the railway track in the form of a berm (20) supported by a lower track (22), characterized in that it comprises: a step (110) of acquiring at least one point cloud of the portion of railway track and the terrain surrounding said at least one portion of railway track, a step (114) of extracting the rail lines (14) of the track to be studied from the point cloud, a step (116) of creating a digital terrain model (200) of the section of railway track and its surroundings from the point cloud, a step (120) of creating at least one theoretical ballast profile (36a, 36b, 36a', 36b') from data representative of predetermined ballast profile standards, comprising: • a sub-step (120a) of determining a set of starting points for the berm, at the level of at least one sleeper carrying the rail, the points being distributed along the section of railway track, • a substep (120b) of determining a set of high points of the bench, the surface defined by the starting points and the high points forming a flat profile of the ballast bench, • a sub-step (120c) of determining each theoretical profile by generating a theoretical surface representative of a theoretical slope profile of the ballast bench, from the set of high points and predetermined inclination parameters of the theoretical surface as a function of standard data, • a step (124) of calculating the conformity of the ballast volume with respect to the theoretical profile.

2. Method for controlling ballast volume according to claim 1, characterized in that the point cloud is obtained by a step of scanning each section of track by a LiDAR, and / or by a photogrammetry step from photographic images of each section of track.

3. A method for controlling the ballast volume according to any one of claims 1 or 2, characterized in that the point cloud acquisition step (110) is carried out by a device mounted on a railway vehicle.

4. A method for controlling the ballast volume according to any one of claims 1 to 3, characterized in that the step (114) of extracting the rail lines comprises a substep (114a) of identifying the points associated with each rail in the point cloud, and a substep (114b) of determining polylines representing the rail lines from the points associated with each rail.

5. Method for controlling the ballast volume according to any one of claims 1 to 4, characterized in that the step (116) of creating the digital terrain model includes a substep (116a) of converting the point cloud into vertices forming the vertices of faces, preferably triangular, said faces being representative of the ground surface and the railway track elements laid on the ground.

6. A method for controlling the ballast volume according to any one of claims 1 to 5, characterized in that it comprises a step (118) for detecting the toe of the bench along at least one rail in the digital terrain model, the toe of the bench corresponding to the point of intersection between a slope of the ballast bench and the track on which the ballast rests, comprising: • a substep (118a) of cutting along a plane perpendicular to a rail, so as to obtain a plurality of cuts distributed over the length of the rail, each cut comprising a plurality of vertices of the digital terrain model, • a substep (118b) of dividing each section into vertical strips according to a predetermined step, each vertical strip comprising a part of the vertices, • a substep (118c) of determining, for each vertical strip of the section, the point whose altitude value is the lowest, • a substep (118d) of detecting, from the set of points of the section whose altitude value is the lowest, a group of said points of the set forming a slope profile and at least one group of said points forming a flat profile, • a substep (118e) of determining a point forming the foot of the bench for each section as intersection of at least one flat profile and the slope profile, • a substep (118f) of smoothing, for all the sections, the foot of the bench over the whole portion of track.

7. Method for controlling the ballast volume according to any one of claims 1 to 6, characterized in that the step (120) of creating at least one theoretical profile is further carried out from data representative of the type of sleeper and the type of profile of the ballast bench.

8. Method for controlling ballast volume according to claim 7, characterized in that it comprises a step (122) of receiving data representative of predetermined ballast profile standards, data representative of sleeper type and ballast bench profile type from a centralized database grouping this data for a set of railway lines of which the railway track portion is a part.

9. A control method according to a combination of claims 1 and 6, characterized in that the step (120) of creating at least one theoretical profile further comprises a substep (120d) of removing, on the theoretical surface, points associated with an altitude lower than the altitude of the foot of the bench and points whose distance to the rail line is greater than the distance between the rail line and the foot of the bench.

10. Method for controlling ballast volume according to any one of claims 1 to 9, characterized in that the substep (120c) of determining each theoretical profile includes the determination of at least two theoretical profiles, by generating two theoretical surfaces each having different predetermined inclination parameters.

11. A method for controlling the ballast volume according to any one of claims 1 to 10, characterized in that the step (124) of calculating the conformity of the ballast volume with respect to the theoretical profile comprises: • a substep (124a) of discretization along a longitudinal dimension to the rail and a lateral dimension to the rail, of each theoretical profile at predefined intervals, along the section of railway track, so as to obtain a set of points forming a grid of each theoretical profile, • a substep (124b) of determining, for each point of the grid, the point of the digital terrain model closest to said point of the grid, called the actual ballast point, • a substep (124c) of calculating the difference between the altitude of the point of the grid and the altitude of the associated actual ballast point,said difference being representative of a surplus or a shortage of ballast at that point on the grid, • a substep (124d) of adding a set of calculated differences corresponding to a plurality of points on the grid, so as to obtain a total ballast volume on the section of railway track.

12. A method for controlling the ballast volume according to a combination of claims 10 and 11, characterized in that step (124) of calculating the conformity of the ballast volume with respect to the theoretical profile comprises: • a substep (124e) of detecting a ballast surplus if the altitude of the actual ballast point is greater than the altitude of the associated grid point of all the theoretical profiles,

13. • a substep (1241) for detecting a lack of ballast if the altitude of the actual ballast point is lower than the altitude of the associated grid point of all theoretical profiles, • a substep (124g) of detecting conformity of ballast volume if the altitude of the actual ballast point is between the altitude of the grid point associated with a first theoretical profile and the altitude of the grid point associated with a second theoretical profile. Automatic ballast volume control system for at least a section of railway track, the ballast being extended around the railway track in the form of a berm (20) supported by a lower track (22), characterized in that it comprises: • an acquisition module for at least one point cloud of the section of railway track and the terrain surrounding said section of railway track, • a module for extracting the rail lines of the track to be studied from the point cloud, • a module for creating a digital terrain model of the section of railway track and its surroundings from the point cloud, • a module for creating at least one theoretical ballast profile from representative data of predetermined ballast profile standards, said creation module being configured to: • the determination of a set of starting points for the berm, at the level of at least one sleeper carrying the rail, the points being distributed along the section of railway track, • a determination of a set of high points of the bench, the surface defined by the starting points and the high points forming a flat profile of the ballast bench, • a determination of each theoretical profile by generating a theoretical surface representative of a theoretical slope profile of the ballast bench, from all the high points

14. and predetermined parameters for the inclination of the theoretical surface based on standard data, • a module for calculating the conformity of the ballast volume with respect to the theoretical profile. A computer program product for the automatic control of the ballast volume of at least one portion of railway track, the ballast being spread around the railway track in the form of a berm (20) supported by a lower track (22), said computer program product being characterized in that it comprises program code instructions for the execution, when said computer program product is executed on a computer, of the steps of a process comprising: • a step (110) of acquiring at least one point cloud of the portion of railway track and the terrain surrounding said at least one portion of railway track, • a step (114) of extracting the rail lines of the track to be studied from the point cloud, • a step (116) of creating a digital terrain model of the section of railway track and its surroundings from the point cloud, • a step (120) of creating at least one theoretical ballast profile from data representative of predetermined ballast profile standards, comprising: • a sub-step (120a) of determining a set of starting points for the berm, at the level of at least one sleeper carrying the rail, the points being distributed along the section of railway track, • a substep (120b) of determining a set of high points of the bench, the surface defined by the starting points and the high points forming a flat profile of the ballast bench, • a sub-step (120c) of determining each theoretical profile by generating a surface theoretical representative of a theoretical slope profile of the ballast bench, based on all high points and predetermined parameters of the theoretical surface inclination according to standard data, a step (124) of calculating the conformity of the ballast volume with respect to the theoretical profile.

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