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 AUTOMATICALLY CONTROLLING 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 portion of railway track. In particular, the invention relates to a method for automating the calculation of ballast volume from data originating from 3D point clouds of the portion of track and the surrounding terrain, for example acquired by LiDAR. Technological background

[0002] Railway ballast is a layer of stones and / or gravel spread along the path of a railway track and on which the railway sleepers and rails are placed. The ballast has the particular objective of maintaining the position of the sleepers and rails when they are subjected to mechanical stresses during the passage of railway vehicles, allows the transfer and distribution of these mechanical stresses towards the ground, facilitates the drainage of rainwater on the track, etc.

[0003] Despite its high resistance to mechanical and environmental constraints over time, ballast must be subject to regular checks to ensure that its main functions are maintained for safety reasons, and possibly to plan its replacement. Ballast checks include, in particular, checking its volume, which consists partly of verifying the conformity of the ballast profile according 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 control is generally visual and carried out by human maintenance operators according to experts (without any particular measuring tool). It is therefore subject to variations in precision depending on the operator's perception, his degree of expertise, his physical condition, his degree of attention and the environmental conditions (access to the analysis area) and climatic conditions (fog, rain, etc.) of the visual control. This control also requires a significant number of human resources and considerable organization for the supervision of kilometers of track (need for training, load plan, etc.)

[0005] Furthermore, ballast maintenance requires knowledge of the volumes to be recovered in the event of a ballast volume exceeding the expected standards (excess ballast), or added in the event of a ballast volume below the expected standards (lack of ballast).

[0006] While the control and maintenance currently carried out provide good results in terms of safety, the cost of this maintenance remains high due to the lack of an effective solution for estimating the volume of ballast on each section of track a priori. In particular, the absence of a detailed assessment of existing ballast volumes pushes the maintainer to favor ballasting operations (adding ballast) rather than leveling operations (recovery of surplus ballast). This approach, although a priori implemented with a view to safety (to limit the constraints in the sleepers), leads to an additional cost in terms of raw material (supply and addition of ballast) but also implies new constraints on the railway platform (additional mass of ballast) thus leading to accelerated degradation and the need for new ballast orders to fill the platform defects.

[0007] A more precise knowledge of the ballast volume on a section of railway track could also facilitate ballast renewal work by providing a better understanding of the volume of old ballast to be removed and the volume of new ballast to be delivered to the site. Currently, ballast volume measurements are carried out retrospectively by analyzing the quantities of ballast extracted by the work 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 automatically controlling the ballast volume of at least one portion of railway track.

[0010] The invention also aims to provide, in at least one embodiment, such a method, system and computer program product making it possible to automatically evaluate 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 making it possible to automatically evaluate the volume of ballast in order to evaluate a possible surplus or lack of ballast on a portion of track.

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

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

[0014] The method according to the invention therefore allows automation of the control of the volume of the ballast on a portion of railway track, using data from 3D point clouds of said portion and the surrounding terrain. The determination of the volume is carried out by comparison with a theoretical profile associated with the predetermined ballast profile standards, these standards being able to be regulatory standards defined by the region or country in which the portion of railway track is located, and / or professional standards for example linked to current practice in the company responsible for the installation of the portion of railway track or linked to specific calculations of mechanical / environmental and / or geological constraints on this portion of railway track.

[0015] The portion of railway track corresponds to a part of a railway line for which the ballast volume is controlled, for example for maintenance or replacement. The railway line can be single (a single track and two lines of rail) or double (two tracks and four lines of rail), or include more tracks. The length of the railway track controlled depends on the technical constraints for taking the point cloud, the maximum size of the point cloud size, the length of track that is planned to be controlled, etc. The length of track controlled during an implementation of the method can thus extend from several tens of meters for a specific control to several tens or even hundreds of kilometers of railway track for a general and recurring control of an extended railway network.

[0016] A priori knowledge of the volume makes it possible to simplify the distribution chain for the renewal of the ballast, in particular to simplify the ordering of the ballast, its delivery, the organization of the stocks of ballast placed on the ground for the purpose works (carried out using ballast pits).

[0017] A priori knowledge of the volume and comparison with 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 portion of road studied.

[0019] The point cloud data can also be pre-processed to convert it into an easily usable and geometrically reliable format, for example a LAS or LAZ format (compressed LAS format). Pre-processing 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 portion of track by a LiDAR, and / or by a step of photogrammetry from photographic images of each portion of track.

[0021] According to this aspect of the invention, the use of a LiDAR makes it possible in particular to obtain point clouds with significant precision for the generation of a precise digital terrain model, while photogrammetry makes it possible in particular to work from photographic images which 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 the obtaining of images by driving directly on the portion of railway track which is to be the subject of the ballast volume control. The device mounted on the railway vehicle is thus 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 may be an ESV type track monitoring machine, which makes it possible to acquire a significant linear length of railway track in one 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 carried by a backpack, by taking aerial photographic images, etc.

[0025] Advantageously and according to the invention, the step of extracting the rail lines comprises a sub-step of identifying the points associated with each rail in the point cloud, and a sub-step 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 as part of the same rail line of the railway track, thus 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 comprises a sub-step of converting the point cloud into vertices forming the vertices of faces, preferably triangular, said faces being representative of the surface of the ground and of the elements of the railway track placed on the ground.

[0028] Advantageously and according to the invention, the method comprises a step of detecting the foot of the bench along at least one rail line in the digital terrain model, the foot 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 over 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 pitch, each vertical strip comprising a part of the vertices, - a sub-step of determining, for each vertical strip of the section, the point whose altitude value is the lowest, - a sub-step 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 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 smoothing sub-step, for all the cuts, of the base of the bench over the entire section of track.

[0029] According to this aspect of the invention, the detection of the foot of the bench is an optional step making it possible to better characterize the general shape of the ballast bench, and in particular making it possible to simplify the calculation of the conformity of the ballast volume with respect to the theoretical profile by limiting the number of data to be processed. The digital terrain model being extended to the entire ground surface around the portion of railway track, the determination of the foot of the bench makes it possible to eliminate data that is not relevant to the control of the ballast volume by reducing the study window to the ballast bench without processing the useless data relating to the rest of the ground surface of the digital terrain model.

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

[0031] To limit the number of points to be processed, the method may advantageously comprise a step of filtering the data from the digital terrain model which are close to the rail line studied, which is the rail line located on the side of the bench in the case of a double track, and of filtering the data from the digital terrain model which are far from the rail line and clearly outside the ballast bench. For example, the points less than 50cm from the rail line and more than 5m 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, a linear interpolation can make it possible to add calculated points in the set of points of 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 the regulatory standards can vary depending on the type of sleeper and the type of profile of the ballast bench, and is therefore taken into account in the control of the ballast volume by the creation of a theoretical profile appropriate to the portion of track controlled.

[0035] Advantageously and according to the invention, the method comprises a step of receiving data representative of predetermined ballast profile standards, data representative of the type of sleeper and the type of profile of the ballast bench from a centralized database grouping these data for a set of railway tracks of which the portion of railway track forms part.

[0036] According to this aspect of the invention, a centralized database can allow the recovery of the data necessary for the creation of the theoretical profile. An example of such a database is the ARMEN database in France allowing this data to be recovered over a major part of the French railway network.

[0037] Advantageously and according to the invention, the method comprises a step of detecting the foot of the bench along at least one rail line in the digital terrain model, the foot 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 line of rail, so as to obtain a plurality of cuts distributed over the length of the line of rail, 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 pitch, each vertical strip comprising a part of the vertices, - a sub-step of determining, for each vertical strip of the section, the point whose altitude value is the lowest, - a sub-step 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 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 smoothing sub-step, for all the cuts, of the base of the bench over the entire section of track.

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

[0039] According to this aspect of the invention, the bench leg makes it possible in this context to filter irrelevant data in order to limit the number of data to be processed.

[0040] Advantageously and according to the invention, the sub-step of determining each theoretical profile comprises the determination of 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 to 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 sub-step 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, - 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 real ballast point, - a sub-step 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 lack of ballast at this grid point, - a sub-step of adding a set of calculated differences corresponding to a plurality of points of the grid, so as to obtain a volume of

[0043]

[0044]

[0045]

[0046]

[0047] total ballast on the railway section. According to this aspect of the invention, this step makes it possible to precisely control the volume of ballast over the entire surface around the portion of railway track, at each point of the grid and more generally over a part of the surface or the entire surface to be controlled by adding the volumes calculated over a plurality of points of the grid. The method can thus make it possible to obtain, for example, an estimate of the volume of ballast, its surplus or its shortage per kilometer of railway track for control over long distances. 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 higher than the altitude of the associated grid point of all the 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 the theoretical profiles, - a sub-step for detecting compliance 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. The invention also relates to a system for automatically controlling the ballast volume of at least one portion of railway track, the ballast being extended around the railway track in the form of a bench supported by a lower track, characterized in that it comprises: - a module for 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 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 data representative of predetermined ballast profile standards, - a module for calculating the conformity of the ballast volume in relation to the theoretical profile. The technical effects and advantages of the method according to the invention apply mutatis mutandis to the system according to the invention. The processing unit of the system according to the invention comprises for example a computing device which must be understood in the 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 the text, the term module refers to a software element, a subset of a software program, which can be compiled separately, either for independent use or to be assembled with other modules of a program, or a hardware element, or a combination of a hardware element and a software subroutine. Such a hardware element may comprise an application-specific integrated circuit (better known by the acronym ASIC for the English term Application-Specific Integrated Circuit) or a programmable logic circuit (better known by the acronym FPGA for the English term Field-Programmable Gate Array) or a specialized microprocessor circuit (better known by the acronym DSP for the English term Digital Signal Processor) or any equivalent hardware or any combination of the aforementioned hardware. Generally speaking, a module is therefore an element (software and / or hardware) which makes it possible to perform 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 automatically controlling the ballast volume of at least one portion of railway track, the ballast being extended around the railway track in the form of a bench supported by a lower track, said computer program product being characterized in that it comprises program code instructions for executing, when said computer program product is executed on a computer, steps of a method comprising: - a step 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 of extracting the rail lines of the track to be studied from the point cloud, - a step of creating 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 data representative of predetermined ballast profile standards, - a step of calculating the conformity of the ballast volume in relation 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 a module or a plurality of 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 method according to the invention. List of figures

[0055] Other aims, characteristics and advantages of the invention will appear on reading the following description given solely for non-limiting purposes and which refers to the appended figures in which: • [Fig.l] is a schematic sectional view of a portion of railway track, • [Fig.2] is a schematic view of an automatic control process of the ballast volume according to one embodiment of the invention, • [Fig. 3] is a schematic sectional view of a portion of railway track as represented in a digital terrain model as created during the execution of an automatic ballast volume control method according to one embodiment of the invention, • [Fig.4] is a schematic sectional view of a portion of railway track in which ballast dimension parameters are visible, • [Fig.5] is a schematic perspective view of a digital terrain model as created during the execution of an automatic ballast volume control method according to one embodiment of the invention, • [Fig.6] is a schematic sectional view of a portion of railway track in which ballast dimension parameters and theoretical profiles are visible as created during the execution of an automatic ballast volume control method 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 the figures.

[0059] [Fig.l] schematically illustrates in section a portion 10 of railway track. The portion 10 of railway track comprises two traffic lanes, a first traffic lane 12a formed of two rails 14a and 14b, and a second traffic lane 12b formed of two rails 16a and 16b. The rails 14a and 14b of the first lane 12a traffic are carried by a sleeper 18a and the rails 16a and 16b of the second traffic track 12b are carried by a sleeper 18b.

[0060] The railway track also comprises ballast, arranged in the form of a ballast bench 20 supporting and surrounding the sleepers 18a and 18b of the portion of railway track; The name bench refers to the particular shape forming a trapezoidal cross-section when it is placed on the track. The ballast is, in a known manner, formed of layers of stones and / or gravel and in particular allows the sleepers and rails to be held 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 ballast support surface and the geographical area in which the railway track is located, in particular for reasons of ease of local supply in view of the quantity required. The ballast bench 20 is supported by a lower track 22 formed for example in this embodiment of an underlayer 24 and a shaping layer 26.The portion of railway track may include other elements, for example a longitudinal drainage device 27.

[0061] The ballast bench 20 is notably characterized 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] [Fig. 2] schematically illustrates a method for automatically controlling the ballast volume of at least one portion of railway track, according to one embodiment of the invention. In particular, the method can be applied to a portion of railway track as described with reference to [Fig. 1].

[0063] The method 100 comprises in particular 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. The point clouds may be acquired in particular by track monitoring vehicles (ESV) which are equipped with LiDAR and which travel the railway track of which the portion of railway track to be monitored is part. These point clouds are thus representative of the state of the track at the given time when the capture was carried out. The point clouds contain the topographical and geometric characteristics of the various elements of the track such as the ballast, the rails, the platforms, the catenary poles, etc. These data are also preferably geolocated with an accuracy of the order of a few centimeters, 5 centimeters on average.The point cloud can also be obtained by a photogrammetry step from photographic images of each section of track.

[0064] The method 100 may also then comprise a step 112 of preprocessing each point cloud. This step makes it possible to make the point cloud more usable and geometrically reliable, for example by converting the point cloud data into a LAS (.las) or LAZ (.laz) format, and for example by combining several point clouds into a single point cloud.

[0065] The method 100 then comprises a step 114 of extracting the rail lines of the track to be studied from the point cloud. This step 114 comprises in particular a sub-step 114a of identifying the points associated with each rail in the point cloud, and a sub-step 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 rail lines of each of the tracks present in a point cloud. This information is finally presented in the form of a number of polylines equal to the number of tracks in the cloud, distinguishing the right line and the left line. The coordinates of the vertices relating to the rails can then be used as references to carry out geometric calculations to manipulate the points of the cloud.

[0067] The method 100 then comprises a step 116 of creating a digital terrain model of the portion of railway track and its surroundings from the point cloud, possibly after preprocessing. This step 116 comprises a sub-step 116a of converting the point cloud into vertices forming the summits of polygonal faces, preferably triangular, said polygonal faces being representative of the surface of the ground and of the elements of the railway track placed on the ground.

[0068] The digital terrain model, also known by its abbreviation MNT or in English digital terrain model (DTM), takes into account only the geometry of the elements on the ground, therefore including the ballast, and thus represents the surface of the ground in the form of a mesh of triangles. This data format makes it easier to study the volumetric of the ballast.

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

[0070] Step 118 of detecting the bench foot comprises in particular a sub-step 118a of cutting along a plane perpendicular to a rail line, so as to obtain a plurality of cuts distributed over 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 for example obtained by recovering the points located five meters on either side of the rail extraction 14a, then by filtering the points of the cut more than five meters and less than fifty cm from the rail line 14a on the side where the foot 28a of the bench is located, so as to reduce the number of points to be processed.

[0071] Step 118 of detecting the foot of the bench then comprises a sub-step 118b of dividing each section 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 visible in [Fig.3].

[0072] Step 118 of detecting the foot of the bench then comprises a sub-step 118c of determining, for each vertical strip 30 of the section, the point whose altitude value is the lowest. If no point is detected in the vertical strip, a value can be assigned to it, for example (-1;-1). If the first lowest points are negative coordinates, detection of the foot of the bench may not be possible and the method 110 continues to the next step without knowledge of the foot of the bench.

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

[0074] Step 118 of detecting the foot of the bench then comprises a sub-step 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. In particular, the step generally makes it possible to detect two flat profiles, a first flat profile 32a at the rail and a second flat profile 32b after the foot of the bench, separated by the slope profile 34.

[0075] Sub-step 118d comprises in particular: - a path through 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 pitch. - once out of the first flat profile, we iterate at the slope profile level until we re-identify a flat profile. - if three consecutive points have a flat profile, we consider that the bench foot has been found.

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

[0077] Step 118 of detecting the foot of the bench then comprises a sub-step 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 comprises a sub-step 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 for bench foot detection, either from sections or directly on the complete digital terrain model.

[0080] The method 100 then comprises 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 visible 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 carried out using data representative of the type of sleeper and the type of profile of the ballast bench. To do this, the method comprises a step 122 of receiving data representative of predetermined ballast profile standards, data representative of the type of sleeper and the type of profile of the ballast bench from a centralized database grouping these data for a set of railway tracks of which the portion of railway track is part. This centralized database is for example a database making an inventory of the various current characteristics of the elements of the track over its entire length, and detailing the types of ballast profiles, materials of the rails and sleepers on each of the homogeneous sections resulting from maintenance and regeneration work. In this system, the ballast profiles and the types of sleepers are mainly used.

[0082] There are many types of sleepers: Concrete Bibloc, Monobloc, Wood, Metallic, 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 points.

[0083] The ballast profile can also be of different types, for example three types of profiles: full 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] [Fig.4] schematically illustrates in section a portion of railway track as represented in a digital terrain model, showing these different points. Taking into account the bearing (the inclination between the left rail line and the right rail line), these points are calculated with the standards in force for each profile.

[0085] Step 120 of creating at least one theoretical profile thus comprises a sub-step 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 comprises a sub-step 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 comprises 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 all the high points and predetermined inclination parameters of the theoretical surface as a function of the standard data. In particular, two theoretical profiles can be created, by varying the inclination parameters w and z corresponding respectively to the height of the slope and to the width of the slope, 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 comprise a sub-step 120d of deleting, on the theoretical surface, points associated with an altitude lower than the altitude of the base of the bench and points whose distance from the rail line is greater than the distance between the rail line and the base of the bench. The low point C thus corresponds to a point on the profile whose altitude is equal to the base of the bench and at a distance from the rail line lower than the base of the bench. The profile is thus corrected with the base of the bench. The altitude of point C of the theoretical profiles cannot be lower than the altitude of the base of the bench and not further from the tracks than the base of the bench in order to have an equivalent study surface on the real and the theoretical.

[0089] The theoretical profiles generated point by point from the rail extraction will make it possible to generate the mesh of the 3D geometry of the theoretical ballast bench profiles using mainly Delaunay triangulation. This mesh can thus be included in the digital terrain model to obtain a model such as visible in [Fig.5] illustrating in perspective a digital terrain model 200 as created during the execution of an automatic ballast volume control method according to an embodiment of the invention.

[0090] On the model are visible the surface 202 of the ground, the lines 14 of rail, the lines 28 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 method 100 then comprises 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 comprises a sub-step 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 of calculating the conformity of the ballast volume then comprises a sub-step 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 real ballast point. Preferably, this step comprises a search for the closest point in the discretized DTM data located less than 20 cm away.

[0094] This step 124 of calculating the conformity of the ballast volume then comprises a sub-step 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 this grid point,

[0095] This step 124 of calculating the conformity of the ballast volume then comprises a sub-step 124d of adding a set of calculated differences corresponding to a plurality of points of the grid, so as to obtain a total ballast volume on the portion of railway track. Preferably, this sub-step comprises, 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 have volumes per kilometer point.

[0096] In particular, step 124 of calculating the conformity of the ballast volume comprises: - a sub-step 124e for detecting excess ballast if the altitude of the actual ballast point is higher than the altitude of the associated grid point of all the 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 the theoretical profiles, - a sub-step 124g 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.

[0097] For example, in the described embodiment, for the ballast quantity 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] illustrating sche matically in section a portion of railway track in which are visible parameters of ballast dimension and theoretical profiles as created during the execution of a method for automatic control of the ballast volume according to an embodiment of the invention. The ballast profile 40 is here between the first theoretical profile 36a and the second theoretical profile 36b.

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

[0099] Further, in this embodiment: - if the sum of the ballast volumes calculated between the DTM 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 DTM data of the volumes 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 excess ballast.

[0100] Thus, the estimation of the ballast cross-section requires knowledge of the ballast profile. LiDAR data provides topographic information before renovation work, an automatic extraction of ballast profiles from this data is carried out. The measured profile is compared to the standard profile to estimate the excess ballast. Ideally, this excess should be removed before renewal work and recycled in order to optimize the efficiency of the ballast renewal machine.

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

Claims

Claims

1. Method for automatically controlling the ballast volume of at least one portion of railway track (12a, 12b), the ballast being extended around the railway track in the form of a bench (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 portion 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 ballast,• a step (124) of calculating the conformity of the ballast volume with respect to the theoretical profile.,

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

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

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

5. Method for controlling the ballast volume according to one of claims 1 to 4, characterized in that the step (116) of creating the digital terrain model comprises a sub-step (116a) of converting the cloud of vertex points forming the vertices of faces, preferably triangular, said faces being representative of the ground surface and the elements of the railway track placed on the ground.

6. Method for controlling the ballast volume according to one of claims 1 to 5, characterized in that it comprises a step (118) of detecting the foot of the bench along at least one rail line in the digital terrain model, the foot 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 (118a) of cutting along a plane perpendicular to a rail line, so as to obtain a plurality of cuts distributed over the length of the rail line, each cut comprising a plurality of vertices of the digital terrain model, • a sub-step (118b) of dividing each cut into vertical strips according to a predetermined pitch, each vertical strip comprising a portion of the vertices, • a sub-step (118c) of determining, for each vertical strip of the cut, the point whose altitude value is the lowest,• a sub-step (118d) of detecting, from all the 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 sub-step (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, • a sub-step (118f) of smoothing, for all the sections, the foot of the bench over the entire portion of track.,

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

9. Method for controlling the ballast volume according to one of claims 1 to 7, characterized in that the step (120) of creating at least one theoretical profile comprises: • a sub-step (120a) of determining a set of starting points of the bench, at the level of at least one sleeper carrying the rail, the points being distributed along the portion of railway track, • a sub-step (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 the standard data.

10. Control method according to a combination of claims 6 and 9, characterized in that the step (120) of creating at least one theoretical profile further comprises a sub-step (120d) of deleting, on the theoretical surface, points associated with an altitude lower than the altitude of the base of the bench and points whose distance from the rail line is greater than the distance between the rail line and the base of the bench.

11. Method for controlling the ballast volume according to claim 9, characterized in that the sub-step (120c) of determining each theoretical profile comprises the determination of at least two theoretical profiles, by generating two theoretical surfaces each having different predetermined inclination parameters.

12. Method for controlling the ballast volume according to one of claims 9 to 11, characterized in that the step (124) of calculating the conformity of the ballast volume relative to the theoretical profile includes: • a sub-step (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, • a sub-step (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 real ballast point, • a sub-step (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 this grid point, • a sub-step (124d) of adding a set of calculated differences corresponding to a plurality of points of the grid, so as to obtain a total ballast volume on the portion of railway track.

13. A method of controlling the ballast volume according to a combination of claims 11 and 12, characterized in that the step (124) of calculating the conformity of the ballast volume with respect to the theoretical profile comprises: • a sub-step (124e) of detecting excess ballast if the altitude of the actual ballast point is higher than the altitude of the associated grid point of all the theoretical profiles, • a sub-step (124f) of detecting a lack of ballast if the altitude of the actual ballast point is lower than the altitude of the associated grid point of the set of 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.

14. System for automatically controlling the ballast volume of at least a portion of railway track, the ballast being extended around the railway track in the form of a bench (20) supported by a lower track (22), characterized in that it comprises: • a module for 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 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 data representative of predetermined ballast profile standards, • a module for calculating the conformity of the ballast volume in relation to the theoretical profile.

15. A computer program product for automatically controlling the ballast volume of at least a portion of railway track, the ballast being extended around the railway track in the form of a bench (20) supported by a lower track (22), said computer program product being characterized in that it comprises program code instructions for executing, when said computer program product is executed on a computer, steps of a method 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 portion 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, a step (124) of calculating the conformity of the ballast volume with respect to the theoretical profile.

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