Method and system for detecting and characterizing geometric defects in a railway track.

Abstract

Method and system for detecting and characterizing geometric defects in a railway track. The invention relates primarily to the detection of geometric defects in a railway track, enabling the characterization of longitudinal and transverse leveling defects and the reliable and reproducible estimation of alignment and gauge defects in said railway track. Figure to be published with the abstract: Fig 2.

Description

Title of the invention: Method and system for detecting and characterizing geometric defects in a railway track. Technical field

[0001] The invention falls within the railway field and relates more specifically to the monitoring of geometric defects in railway tracks.

[0002] The invention relates more particularly to a method and a system for detecting geometric defects in a railway track, these defects being the expression of an undesirable deformation of the railway track. PRIOR ART AND DISADVANTAGES OF PRIOR ART

[0003] The geometry of railway tracks is an essential parameter for rail traffic. Indeed, the number of geometric defects in the track and especially their amplitude must be as low as possible to allow trains to run while ensuring comfort for passengers and avoiding premature damage to equipment.

[0004] The geometric defects, represented respectively in Figures 1A to 1D, are mainly of four types. The first ([Fig.lA]), the gauge, corresponds to a modification, compared to the nominal distance, of the distance between the two rails. The second ([Fig.lB]), the dressing, is a sudden change in the position of the two rails in the plane of the track over a short distance compared to the track layout. The third ([Fig.lC]), the transverse leveling, also called left, is a subsidence or a raising of one of the rails of the track over a short distance. Finally, the fourth defect ([Fig.lD]), the longitudinal leveling, is an abnormal subsidence or raising of the two rails of the track over a short distance (i.e. a distance of a few tens of meters).

[0005] It is known to directly measure the profile of a railway track using a measuring device on board a railway machine, the measuring device generally being an optical system of the laser sheet rangefinder type. The profile of each rail of the track is thus obtained, and consequently any geometric defects and their position on the track are detected.

[0006] However, it is necessary to use a railway machine dedicated to carrying out these measurements, because the installation of the optical measuring system requires prior calibration tests to be carried out which are dependent on the railway machine. In addition, the measuring means implemented must be both precise and robust, because they are often installed outside under the floor of the machine (facing the rails). Finally, the railway machine dedicated to the measurement must necessarily travel regularly all the tracks, which causes disruption to commercial train traffic.

[0007] Also known from publication FR3062141 is a system for detecting longitudinal and transverse leveling defects in railway tracks, which system is intended to be installed on railway rolling stock in commercial circulation.

[0008] However, the system described in this publication is not able to detect all of the geometric defects of the railway track, and in particular the gauge and straightening defects, in particular because the lateral trajectory of the axles is different from the lateral position of the rails. OBJECTIVE OF THE INVENTION

[0009] The invention thus aims to propose a method for detecting all of the geometry defects in the railway track without interfering with the commercial circulation of trains.

[0010] The invention also aims to propose a system for detecting geometry defects in a railway track which does not require the integration of complex and expensive measuring instruments. Statement of the invention

[0011] For this purpose, the method for detecting and characterizing geometry defects in a railway track comprising two opposite rails, implemented by a detection system installed on railway rolling stock running on said railway track, which system comprises means for measuring the vertical accelerations experienced by said rolling stock at the level of the two rails and control means connected to said acceleration measuring means, characterized in that it comprises at least the successive steps of: • Periodic acquisition of a geographical position of the rolling stock running on the railway, and of two vertical accelerations undergone by the rolling stock at two opposite measurement points located at the same transverse level; • Association for each acquisition period, of the acquired geographical position with the two corresponding vertical accelerations; • Determination for each acquired geographical position, of a pair of two vertical arrows calculated from the vertical accelerations considered; • Comparison between the pairs of arrows determined for the successive acquired geographical positions; • Determination of longitudinal and transverse leveling defects of the railway track when the difference between two consecutive pairs of arrows is greater than a determined threshold, and association of each longitudinal or transverse leveling defect with the geographical position considered; • Selection from a database of data relating to a standard railway track, which data includes the longitudinal and transverse leveling defects as well as the alignment and gauge defects of the standard railway track and the respective geographical positions of said longitudinal and transverse leveling, alignment and gauge defects on the standard track; • Characterization, from the selected database, of the statistical dependence between the longitudinal and transverse leveling defects on the one hand and the dressing and spacing defects on the other hand of the standard track; • Application of statistical dependence by conditioning to longitudinal and transverse leveling defects of the railway track, and • Estimation of track dressing and gauge defects and their respective geographical positions on the track.

[0012] The method of the invention may also include the following optional characteristics considered in isolation or according to all possible technical combinations: - The step of determining the statistical dependence is carried out by a calculation of covariance between the longitudinal and transverse leveling defects on the one hand and the dressing and spacing defects on the other hand of the standard track. - The rolling stock comprising means for measuring the transverse accelerations undergone by an axle of said rolling stock running on the railway track, the method comprises an additional step of improving the estimation of the defects in the dressing and gauge of the railway track according to the following sub-steps: • Acquisition of at least one transverse acceleration experienced by the axle of the rolling stock concurrently with the periodic acquisition of the geographical position of the rolling stock running on the railway track and the two vertical accelerations; • Determination of the lateral trajectories of the axle from the acquired transverse acceleration data; • Association of each geographical position and the two vertical accelerations acquired with the corresponding transverse acceleration laying; • Simulation of the train's behavior during the studied movement based on the estimation of the track dressing and gauge defects and the determined longitudinal and transverse leveling defects of the track; • Optimization of the estimation of track dressing and gauge defects by comparing said simulation with transverse acceleration measurements or lateral axle trajectories. - The step of characterizing statistical dependence by conditioning is also applied to transverse accelerations or lateral trajectories of the axle. - The step of determining the statistical dependence is enriched by a calculation of covariance between the longitudinal and transverse leveling defects on the one hand and the transverse accelerations or the lateral trajectories of the axle on the other hand. - The optimization step implements a cost function to compare the simulation of the dynamic behavior of the train to the transverse acceleration measurements or to the lateral trajectories of the axle. - The method includes a step of predicting the evolution of the geometry of the railway track from the determination of the longitudinal and transverse leveling defects and the estimates of the straightening and gauge defects of the railway track obtained at different times. - The method includes a step of transmitting data on transverse and longitudinal leveling defects, dressing and gauge of the railway track to a remote server.

[0013] The invention also relates to a system for detecting and characterizing geometry defects in a railway track comprising two opposite rails, capable of being installed on railway rolling stock and of implementing the method as described previously, which system comprises at least means configured to measure vertical accelerations experienced by said rolling stock at the level of the two opposite rails and control means connected to said vertical acceleration measuring means.

[0014] The detection and characterization system may also include the following optional characteristics considered in isolation or according to all possible technical combinations: - The system comprises means configured to measure transverse accelerations experienced by said rolling stock and to calculate the trajectories lateral accelerations of an axle of the railway equipment from said transverse accelerations.

[0015] The invention also relates to railway rolling stock comprising at least one body extending along a longitudinal axis and at least two axles and a system for detecting and characterizing geometry defects of a railway track as described previously.

[0016] The rolling stock may also include the following optional characteristics considered in isolation or in all possible technical combinations: - The system comprises at least one transverse accelerometer mounted on an axle, and at least two vertical accelerometers respectively mounted on two transversely opposed axle boxes. PRESENTATION OF FIGURES

[0017] Other characteristics and advantages of the invention will emerge clearly from the description given below, for information purposes only and in no way limiting, with reference to the appended figures, among which:

[0018] [Fig.lA]

[0019] [Fig.lB]

[0020] [Fig.lC]

[0021] [Fig.1D] Figures 1A to 1D each represent a particular defect in the geometry of the railway track;

[0022] [Fig.2] [Fig.2] represents a graph illustrating curves representing the defects in the dressing of a section of the railway track. DETAILED DESCRIPTION OF THE INVENTION

[0023] It is first of all specified that in the figures, the same references designate the same elements regardless of the figure in which they appear and regardless of the form of representation of these elements. Similarly, if elements are not specifically referenced in one of the figures, their references can be easily found by referring to another figure.

[0024] It is also specified that the figures essentially represent an embodiment of the subject of the invention but that there may be other embodiments which meet the definition of the invention.

[0025] The present invention relates to a method for detecting geometry defects in railway tracks. This method is implemented by a simple and inexpensive detection system, which is installed on a commercial train.

[0026] The system of the invention is intended to be installed on rolling stock of the commercial train type intended for the transport of passengers or freight. In other words, it It is not necessary to use railway rolling stock specifically dedicated to the installation of the detection system, but any commercial train can be used. Not only does this avoid the occupation of the railway by trains solely dedicated to track maintenance measurements, but also the measurements can be carried out on a large number of tracks, and the frequency of measurements on each track is simply limited by the number of commercial trains running on the railway.

[0027] In the remainder of the description, the term train will be used to define railway rolling stock, but it goes without saying that the system of the invention can be installed on any type of railway rolling stock.

[0028] The train on which the detection system of the invention is installed is put into circulation on a railway track comprising two opposite rails and of which one wishes to know the topography and determine all the geometry defects - that is to say the longitudinal and transverse leveling defects, the straightening and the gauge defects. The train, which extends along a longitudinal axis, comprises at least one body and at least two axles, each axle comprising two axle boxes arranged at its respective ends. Typically, the train comprises several bodies and therefore several axles.

[0029] According to the invention, the detection system comprises means for measuring the accelerations experienced by the various elements of the train running on the railway track. The detection system thus comprises a vertical accelerometer installed on each axle box. The system therefore comprises at least two vertical accelerometers installed at a distance from each other in a transverse direction: the two vertical accelerometers are therefore at the same transverse level, to enable two vertical accelerations experienced by the train to be measured at the level of the respective rails.

[0030] The system also includes a vertical accelerator installed on each bogie of the train, which helps in the calibration of the models used to refine the estimation of dressing and gauge defects.

[0031] The system comprises at least one transverse accelerometer installed on an axle whose axle boxes are themselves equipped with vertical accelerometers. Furthermore, the system may comprise one or two transverse - or lateral - accelerometers respectively installed on one of the train bodies and on one of the bogies.

[0032] The detection system also comprises a geographic positioning device of the GPS (for “Global Positioning System”) type, wireless communication means and control and command means typically comprising at least one processor and a memory space, which are generally integrated into the train control means.

[0033] Thus the system of the invention, which is intended to be installed on the train, comprises at least three vertical accelerometers, three transverse accelerometers, a geographic positioning device, wireless communication means and control and command means.

[0034] The method for detecting geometric defects in the railway track according to the invention will now be described.

[0035] The train is equipped with the detection system of the invention and runs on the railway track whose topography is to be known and more particularly on which geometric defects in longitudinal and transverse leveling, dressing and gauges are to be detected.

[0036] During a first step, the control means control the periodic acquisition of two vertical accelerations experienced by the train at two opposite measurement points located at the same transverse level, of a transverse acceleration experienced by the train and of a geographical position of the train. The control means then associate, for each acquisition period, the acquired geographical position with the transverse acceleration value and the pair of vertical acceleration values ​​considered.

[0037] During a second step, the control means determine, for each acquired geographical position, a pair of vertical arrows from the two vertical accelerations considered, for example with spatial filtering. The pair of vertical arrows thus determined corresponds to a vertical movement of the train above each rail of the railway, on the same transverse level.

[0038] During a third step, the control means then compare the successive pairs of vertical arrows. In other words, each pair of arrows determined from vertical accelerations acquired at a determined period is compared with the pair of arrows determined from the vertical accelerations acquired at the immediately following period. If the difference two by two between the arrows of the successive pairs is greater than a determined threshold, then the control means identify the presence of a leveling defect and associate it with the geographical position considered. Furthermore, if the threshold exceeding only concerns one of the two vertical arrows of the pair, then the control means identify a transverse leveling defect, while if the threshold exceeding concerns the two vertical arrows of the pair, then the control means identify a longitudinal leveling defect.

[0039] During a fourth step, the control means select from a database, recorded in the memory space of said control means, data corresponding to one or more standard railway tracks similar to the railway track under study on which the train runs. By similar, we mean a standard railway track whose recommended running speeds, tonnage and type of trains running on this standard railway track are equivalent to those of the railway track under study. The database includes the topography of this standard track as well as a list of all geometry defects - longitudinal and transverse leveling, dressings and gauges - and their respective geographical positions. The database also includes data on transverse accelerations and lateral trajectories of axles of known railway rolling stock running on this standard track. Lateral axle trajectories are understood to mean the transverse component of axle displacement. In the remainder of the description, the expression "axle trajectory" will simply be used to define the lateral trajectory of said axle.

[0040] There is a statistical dependence between, on the one hand, the longitudinal and transverse leveling defects and, on the other hand, the spacing and dressing defects. In particular, this statistical dependence can be determined by a covariance calculation.

[0041] Also, during the fifth step, the statistical dependence between the different geometric defects of the standard railway track is determined by a calculation of covariance between a first series of variables corresponding to the longitudinal and transverse leveling defects of the standard track and a second series of variables corresponding to the dressing and gauge defects of the standard railway track.

[0042] This statistical dependence is then applied, during a sixth step, to the vertical defects of the railway track previously determined on which the train equipped with the geometric defect detection system is running. The control means then deduce an estimate of the defects in the dressing and gauges of the railway track, as well as their respective geographical positions.

[0043] Advantageously, the fourth and fifth steps are completed by the statistical dependence with the transverse accelerations or the associated trajectories of the axle determined by double integration of the transverse accelerations which would be, in the step of constructing the statistical dependencies, measured by the system for detecting and characterizing defects in the railway track, or simulated on the standard track. These enriched dependencies are applied to estimate the dressing and gauge defects by conditioning.

[0044] During a seventh step, the control means improve the estimation of the defects in the dressing and gauges of the railway track by using the transverse acceleration measurements by the transverse accelerometers considered.

[0045] During a first sub-step, the control means carry out a simulation of the dynamic behavior of the train on the vertical defects, dressings and gauges of the railway track estimated previously, for example using a railway dynamics model - for example a railway dynamics code by rigid body - which uses as input data the estimation of the geometric defects of the railway carried out in the previous step, and also the longitudinal and transverse leveling defects determined in the third step, the layout of the railway, the speed of the train and the mechanical characteristics of the train. Regarding the "dynamic behavior of the train" on the track, the latter corresponds to the accelerations that the train undergoes, the forces that the train transmits to the track, and the forces that pass through the different suspensions of the train.

[0046] The output data of the railway dynamics model form a set of accelerations or axle trajectories. These will allow the estimation of the defects in the dressing and gauges of the railway by solving the associated inverse problem.

[0047] During a second sub-step, the data from the simulation are compared with the measurements made by the transverse accelerometers and the associated axle trajectories determined by integration. An optimization loop via a loss - or cost - function is then implemented by the control means to bring the simulation closer to the previously acquired transverse acceleration measurements and / or the associated axle trajectories. Advantageously, the optimization will be carried out with genetic algorithms, known to provide an approximate solution to this type of optimization problem in a reasonable time.

[0048] The results of the simulation and the improvement of the estimation are then sent by the control means - via the wireless communication means - to a remote server for further exploitation.

[0049] [Fig.2] illustrates a graph illustrating three curves representing the dressing defects on a portion of the railway track. The ordinate axis of the graph represents the amplitude of the dressing defects while the abscissa axis represents the curvilinear abscissa on the portion of track studied.

[0050] The first curve in thick solid line illustrates the actual dressing defects, the second curve in thin solid line represents the first estimate of the dressing defects, and the third curve in broken line represents the estimate improved by the simulation of the dressing defects. It can be seen that the implementation of the method provides an accurate estimate of the dressing defects, by the use of indirect determination methods.

[0051] Thus, the system and the detection method of the invention make it possible to determine in a precise, reliable and reproducible manner all of the geometry defects of the railway track - longitudinal and transverse leveling defects, dressing and gauge defects - without requiring a complex and costly installation, and without requiring specific railway rolling stock.

[0052] Finally, the detection method may comprise an additional step which aims to predict the evolution of the geometry of the railway track.

[0053] Indeed, the control means use improved simulations of the railway track obtained at different times to determine the evolution of the geometry of the railway track over time. Then, using a prediction model, for example a time series model, in particular an unstationary ARMA (autoregressive and moving average) model, the control means determine a prediction of the future evolution of the geometry of the railway track. This last step of the method makes it possible to predict maintenance slots for the railway track, which improves quality while controlling intervention costs.

Claims

Claims

1. Method for detecting and characterizing geometry defects of a railway track comprising two opposite rails, implemented by a detection system installed on railway rolling stock running on said railway track, which system comprises means for measuring the vertical accelerations undergone by said rolling stock at the level of the two rails and control means connected to said acceleration measuring means, characterized in that it comprises at least the successive steps of: • Periodic acquisition of a geographical position of the rolling stock running on the railway, and of two vertical accelerations undergone by the rolling stock at two opposite measurement points located at the same transverse level; • Association, for each acquisition period, of the acquired geographical position with the two corresponding vertical accelerations; • Determination, for each geographical position acquired, of a pair of two vertical arrows calculated from the vertical accelerations considered; • Comparison between the pairs of arrows determined for the successive acquired geographical positions; • Determination of longitudinal and transverse leveling defects of the railway track when the difference between two consecutive pairs of arrows is greater than a determined threshold, and association of each longitudinal or transverse leveling defect with the geographical position considered; • Selection from a database of data relating to a standard railway track, which data includes the longitudinal and transverse leveling defects as well as the alignment and gauge defects of the standard railway track and the respective geographical positions of said longitudinal and transverse leveling, alignment and gauge defects on the standard track; • Characterization, from the selected database, of the statistical dependence between the Ion-leveling defects longitudinal and transverse defects on the one hand and the dressing and gauge defects on the other hand of the standard track; • Application of statistical dependence by conditioning to the longitudinal and transverse leveling defects of the railway, and • Estimation of the dressing and gauge defects of the railway and their respective geographical positions on the railway.

2. Detection method according to the preceding claim, characterized in that the step of characterizing the statistical dependence is carried out by a calculation of covariance between the longitudinal and transverse leveling defects on the one hand and the straightening and spacing defects on the other hand of the standard track.

3. Method according to claim 1 or 2, in which the rolling stock comprises means for measuring the transverse accelerations undergone by an axle of said rolling stock running on the railway, characterized in that the method comprises an additional step of improving the estimation of the defects in the straightening and gauge of the railway according to the following sub-steps: • Acquisition of at least one transverse acceleration undergone by the axle of the rolling stock concomitantly with the periodic acquisition of the geographical position of the rolling stock running on the railway and the two vertical accelerations • Determination of the lateral trajectories of the axle from the acquired transverse acceleration data; • Association of each geographical position and the two acquired vertical accelerations with the corresponding transverse acceleration;• Simulation of the dynamic behavior of the train from the estimation of the alignment and gauge defects of the railway track and the longitudinal and transverse leveling defects of the railway track determined; • Optimization of the estimation of the alignment and gauge defects of the railway track by comparison of said simulation with the transverse acceleration measurements or; lateral axle trajectories.

4. Method according to the preceding claim, characterized in that the step of characterizing the statistical dependence by conditioning is also applied to the transverse accelerations or to the lateral trajectories of the axle.

5. Method according to claims 2 and 3 or according to claims 2 to 4, characterized in that the step of determining the statistical dependence is enriched by a calculation of covariance between the longitudinal and transverse leveling defects on the one hand and the transverse accelerations or the lateral trajectories of the axle on the other hand.

6. Method according to any one of claims 3 to 6, characterized in that the optimization step implements a cost function to compare the simulation of the dynamic behavior of the train to the transverse acceleration measurements or to the lateral trajectories of the axle.

7. Method according to any one of the preceding claims, characterized in that it comprises a step of predicting the evolution of the geometry of the railway track from the determination of the longitudinal and transverse leveling defects and the estimates of the straightening and gauge defects of the railway track obtained at different times.

8. Method according to any one of the preceding claims, characterized in that it comprises a step of transmitting data on transverse and longitudinal leveling defects, dressing and gauge of the railway track to a remote server.

9. System for detecting and characterizing geometry defects in a railway track comprising two opposite rails, capable of being installed on railway rolling stock and of implementing the method according to any one of the preceding claims, characterized in that it comprises at least means configured to measure vertical accelerations experienced by said rolling stock at the level of the two opposite rails and control means connected to said vertical acceleration measuring means.

10. System according to the preceding claim, characterized in that it comprises means configured to measure transverse accelerations undergone by said rolling stock and to calculate the trajectories lateral accelerations of an axle of the railway equipment from said transverse accelerations.

11. Railway rolling stock comprising at least one body extending along a longitudinal axis and at least two axles, characterized in that it comprises a system for detecting and characterizing geometry defects of a railway track according to claim 9 or 10.

12. Equipment according to the preceding claim, characterized in that the system comprises at least one transverse accelerometer mounted on an axle, and at least two vertical accelerometers respectively mounted on two transversely opposite axle boxes.

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