System and method for diagnosing abnormal bending of railway rails, in particular at the junctions between railway rails

Abstract

A system (1) for diagnosing the operating conditions of a joint (J) between steel rails (R1, R2) is described, comprising: a frame (2) configured to be mounted on a railway vehicle at a wheel (W) of the railway vehicle; a first distance sensor (4) and a second distance sensor (6) mounted on the frame (2) and arranged so as to be located on opposite sides of the wheel (W) of the railway vehicle, each of the first distance sensor (4) and the second distance sensor (6) being configured to detect a first distance and a second distance, respectively, between the frame (2) and the top of the steel rails (R1, R2); a third distance sensor (8) mounted on the frame (2) and configured to detect a third distance of the frame (2) with respect to a journal box (10) associated with the wheel (W) of the railway vehicle.

Description

Technical Field

[0001] This invention relates to the diagnosis of railway facilities. More specifically, this invention was developed with reference to the diagnosis of railway rails. Background Technology

[0002] Railway lines have numerous joints between adjacent rails, ensuring the geometric and structural continuity of the railway. Whether achieved by welding or bolting to the joint plates of the rail web, the joints between rails have traditionally been the weakest points in the track.

[0003] Gradual damage and failure of joints typically occur due to rail bending caused by the weight exerted by railway vehicle wheels. If the rail is not well supported by ballast at this point, the vertical load will cause localized bending, resulting in fatigue. In the long run, fatigue can lead to fracture of the joint plate or weld (especially if there are manufacturing defects in the component). The same phenomenon can occur along the continuous rail (i.e., the section outside the joint) in cases of localized lack of support, and the risk of failure increases if cracks are already present for any other reason.

[0004] Without questioning the usefulness of dedicated diagnostic vehicles, it is clear that diagnostics performed by such vehicles have the significant drawback of being discontinuous and, generally, insufficient frequency to detect very rapid degradation: railway vehicles dedicated to diagnostics occupy track spaces on the inspected line, negatively impacting overall railway traffic flow; furthermore, these vehicles may possess characteristics (e.g., weight per axle) that are incomparable to those of railway vehicles normally operating on the line. In the latter case, the diagnostics may be affected by the diagnostic vehicle itself: with a significantly lower weight per axle than normal railway vehicles, rail bending as the vehicle passes may be dangerously underestimated.

[0005] Purpose of the invention

[0006] The purpose of this invention is to solve the aforementioned technical problems. Specifically, the purpose of this invention is to diagnose in advance and continuously whether there is degradation at the joints in the track or anywhere else where local fatigue stress (due to bending on the vertical plane) may occur, so as to be able to take action before dangerous situations occur. Summary of the Invention

[0007] The object of the present invention is achieved by systems and methods having the features set forth in the appended claims, which are integral parts of the technical disclosure provided herein in relation to the present invention. Attached Figure Description

[0008] The invention will now be described with reference to the accompanying drawings, which are provided by way of non-limiting example only, and in which:

[0009] Figure 1 Diagnostic systems according to various embodiments of the present invention are illustrated schematically, and

[0010] Figure 2 , 3A 3B illustrates various aspects of the diagnostic method according to the present invention.

[0011] The Cartesian reference frame shown in the figure is labeled with the longitudinal direction - X-axis, the transverse direction - Y-axis, and the vertical direction - Z-axis. Detailed Implementation

[0012] Figure 1 Reference 1 in the text typically refers to a system used to diagnose abnormal bending of railway rails. Figure 1 System 1 is schematically shown on a pair of rails R1 and R2, which are connected at joint J, which in this example consists of a bolt plate. Rails R1 and R2 form part of the railway track, are mounted on sleepers C, and are supported by railway ballast BL.

[0013] It can be observed that although the figure shows a joint between rails achieved through bolted plates W, the same method applies to welded joints, and even to continuous rails, if there is a discontinuity in the support provided by the ballast BL to the sleeper C. Therefore, joint J must be understood as representing a possible inspection area of ​​the rail.

[0014] For the sake of brevity, the following description will refer only to the diagnostic case of joint J bending, as it should be understood that it can also be applied to continuous rails without joints. System 1 is typically configured to be mounted on railway vehicles, regardless of their type: freight cars, passenger cars, locomotives, as long as they have axles with sufficient load capacity. Diagnostic system 1 includes a substantially rigid frame 2, which serves as a reference for all measurements performed by system 1. Frame 2 can be the frame of the bogie on which system 1 is mounted, or it can be an auxiliary frame that can be mounted on the bogie frame or under the body of the railway vehicle itself. Frame 2 can also correspond to the frame of the railway vehicle, particularly in the case of two-axle vehicles.

[0015] In a preferred embodiment, frame 2 extends from one side of the railway vehicle to the other, that is, it essentially covers the entire gauge between the rails. In other embodiments, frame 2 may extend laterally along a portion of the gauge and have a dual construction (two frames 2, each frame associated with each wheel of the wheelset). As will become more apparent below, the advantage of having frame 2 extend from one side of the gauge to the other is that only one inertial platform is used in the middle of frame 2, rather than two separate inertial platforms above each rail R1, R2.

[0016] In various embodiments, system 1 includes a set of sensors, which may vary depending on different embodiments of the diagnostic method according to the invention.

[0017] In an embodiment with complete equipment, system 1 includes:

[0018] - A first distance sensor 4, preferably a non-contact sensor (in any case, a contact sensor can also be used: it can be an LVDT transducer or other displacement sensor performing the same function), is configured to detect the distance a from the top (upper edge) of the rail R1 to the frame 2, particularly relative to the position occupied by the sensor on the frame 2. The distance a is measured along the vertical direction Z; in the diagnostic method according to the invention, the absolute value of the distance can be considered, or preferably, the change in distance a relative to a value detectable when the railway vehicle is stationary on a continuous and well-maintained track segment (i.e., the track segment bends under vehicle load corresponding to the designed measurement).

[0019] - A second distance sensor 6, preferably a non-contact sensor (a contact sensor can be used in any case), is configured to detect the distance b from the top (upper edge) of the rail R2 to the frame 2, particularly relative to the sensor's position on the frame 2. The distance b is measured along the vertical direction Z; in the diagnostic method according to the invention, the absolute value of the distance can be considered, or preferably, the change in distance a relative to a value detectable when the railway vehicle is stationary on a continuous and well-maintained track segment (i.e., the track segment bends under vehicle load corresponding to the designed measurement).

[0020] Furthermore, it must be noted that when the wheel W, which applies a load to the rail, is on joint J or at a weak point in the rail's curvature, distance sensor 6 is arranged on the opposite side of joint J relative to sensor 4: in other words, when the wheel applies a load to frame 2 and bends it, sensors 4 and 6 (unlike wheel B, which obviously cannot apply force) are positioned on frame 2 to span joint J or the weak point.

[0021] - A third distance sensor 8, preferably a non-contact sensor (a contact sensor can be used in any case: it can be an LVDT converter or other displacement sensor performing the same function), is configured to detect the distance f from frame 2 to journal box 10, which engages with the wheel W of the railway vehicle on which system 1 is mounted. Clearly, since journal box 10 and wheel W maintain their relative positions under all conditions (otherwise, the wheelset would break), the detected distance f from journal box corresponds to the detected position of wheel W relative to the center of frame 2, after subtracting a fixed value corresponding to the dimension of journal box relative to the center of wheel W. It will be apparent from the following description that what is detected is the change in the relative position between wheel W and frame 2 between the following conditions: i) the railway vehicle is stationary on a continuous track segment in good condition (i.e., bending occurs within design specifications – the position is represented by the ideal profile R_ID of the rail sequence R1, R2), and ii) wheel W applies load to joint J or rails R1, R2 without ballast support.

[0022] Alternatively, if a separate frame 2 exists, an inertial platform 12 can be provided to system 1 mounted on frame 2, or in general, an inertial platform 12 can be provided for each frame element constituting frame 2. The inertial platform 8 provides the trajectory of the frame 2 on which it is mounted and is capable of defining a spatial reference line 2R corresponding to the ideal reference trajectory of frame 2 in space. It must be noted that the inertial platform 8 can be mounted at virtually any location on frame 2: the locations shown must be understood as merely exemplary, as algorithms for managing the different relative positions of sensors and inertial platforms are known.

[0023] Alternatively, again, the system 1 may be provided with a first vertical accelerometer 14 (and thus adapted to detect acceleration along the vertical direction Z) and a second vertical accelerometer 16 (and thus adapted to detect acceleration along the vertical direction Z) respectively mounted at the locations of sensor 4 and sensor 6. In some embodiments, accelerometers 14 and 16 may replace the inertial platform 12 at a slightly lower cost (but certainly without the additional performance that the inertial platform 8 can provide).

[0024] Other components of System 1 include:

[0025] - Positioning unit 18, preferably comprising an odometer with millimeter resolution or higher. Positioning unit 18 is capable of identifying all measurements performed by system 1, i.e., associating the measurements with the moment of acquisition detected by the odometer (in time and / or space). In this regard, various methods for associating values ​​detected by the odometer with geographic (e.g., GPS) coordinates to kilometer markers existing in the network are known and widely used; furthermore, the odometer (and generally, positioning unit 18) is configured to trigger the equidistant acquisition of data from sensors 4, 6, and 8, and to trigger a spatial reference for data from inertial platform 8 and accelerometers 14, 16, even if the latter are acquired at a constant temporal (rather than spatial) frequency.

[0026] Alternatively, an automated system 20 for identifying connector J can also be envisioned. This system can be implemented using any known technology, such as automatic image recognition.

[0027] In any case, it must be observed that, although locating the joint is important, the preferred embodiment of the diagnostic method according to the invention envisions keeping system 1 continuously active as if the joint J were ubiquitous. The presence of a rail joint or weak point is detected when the following conditions are met. This could also occur due to rail failure or the presence of a bending weak point that could lead to fatigue failure, and of course, it could occur anywhere: therefore, regardless of the implementation and / or presence of the automatic system 20, system 1 is preferably always active, and not just active when the joint is known to be present.

[0028] In any case, it can be pointed out in general that the automatic system 20 for identifying connector J is useful for the following:

[0029] - Inspect defective joints, broken rails, and weak points.

[0030] - Monitor all joints, including those in good condition, and generate reports (if useful); obviously, a perfect joint is equivalent to a continuous rail, so it cannot be identified by its defects.

[0031] By way of non-limiting example only, the table below identifies some preferred embodiments of System 1, which differ from each other in configuration. The first row of the table indicates reference numerals corresponding to the sensors or components described above, and the following rows indicate the respective embodiments. The presence of the character "X" indicates the presence of a sensor or component.

[0032] First embodiment (preferred) X X X X Second embodiment (deflection only) X X X Third embodiment (simplified inertia) X X X X X

[0033] The measurement uncertainty of sensors 4, 6, and 8 is sub-millimeter (preferably 0.1 mm). The required measurement uncertainty also depends on the quality of the rail being inspected and the required safety margin.

[0034] The quality of the inertial platform 12 and the accelerometers 14 and 16, particularly regarding the signal-to-noise ratio and drift, as well as temperature stability, depends on the desired sensitivity for preventative diagnostics and the minimum speed of operation. Generally, sensors suitable for performing integration for at least 10 seconds without incurring errors exceeding a fraction of a millimeter are preferred.

[0035] Signals from sensors 4, 6, and 8 are preferably sampled at least once every 125 mm, even if they can be operated at a slightly lower sampling rate (i.e., at longer intervals). In any case, if sampling is performed every 25 mm or less, the measurement will be more reliable in order to accurately detect the moment when the load is concentrated at the weakest point of the rail, and thus produce the maximum difference between the data acquired by sensors 4 and 6 (without load) and sensor 8, which detects the effect of the load.

[0036] For known reasons, signals from inertial platforms or accelerometers are sampled in time and then resampled in space within the computation sequence. More frequent sampling also allows noise to be filtered out of the signal, even when using sensors with low noise levels.

[0037] As shown in the previous table, the operation of system 1 according to the first embodiment of the present invention will now be described. The second and third embodiments are configured as substantially more economical versions of the first embodiment, and therefore they cannot perform all the determinations and derivations of the first embodiment.

[0038] refer to Figure 3A For each operating cycle of System 1, distance sensors 4, 6, and 8 are set to zero, meaning their zero reference is established, which may be equal to the reference distance value, and are repeatedly set to zero during maintenance. They are set to zero on straight track segments in good condition and of good quality (in terms of structure and geometry).

[0039] Setting it to zero involves assigning an additional value δ4, δ6, δ8 (offset value - sum or subtraction) to each sensor, such that the readings a, b, f of sensors 4, 6, and 8 are identical to each other; for each sensor 4, 6, and 8, such readings always refer to the upper edge of rails R1 and R2. The term "upper edge" refers to the highest point at the top of the rail; for the sake of brevity, the term "edge" will be used frequently in the following text.

[0040] One possibility lies in determining offset values ​​δ4, δ6, and δ8 such that all readings a, b, and f equal zero; however, another possibility lies in—referencing Figure 3A—Determine the offset values ​​δ4, δ6, and δ8 relative to the reference line 2R, such that their algebraic sum and readings a, b, and f are identical. Thus, a corresponding number of offset values ​​are obtained, which will always be algebraically added to the values ​​measured by each sensor to provide a correct output; under this assumption, in the following description, the distance data mentioned and the readings from sensors 4, 6, and 8 will always be offset-corrected readings determined in this way. Furthermore, the use of offset values ​​δ4, δ6, and δ8 allows the readings a, b, and f to be used as references for diagnostic activities on the rail provided by this invention: offset calibration can be defined in practice under fault-free conditions (a zero reference for the readings, regardless of whether offset calibration is achieved by setting the resulting signal to zero): if the rail or joint J does not experience significant bending under the load of wheel W, the readings of system 1 will always not produce significant differences from the values ​​at the positioning alignment points P1 (distance a), P2 (distance b), and P3 (distance f). Each point P i (In the current case, i = 1, 2, 3) points corresponding to the edges (tops) of rails R1 and R2, at which the corresponding distances a, b, f are detected. Conversely, if a significant bending phenomenon occurs, a deviation from the reference condition will be observed, which System 1 can then diagnose quickly and easily: see the following description for more details.

[0041] All inertial sensors (platform 12 and accelerometers 14, 16) are calibrated using known techniques. Readings a, b, f provide the distance between the frame and rails R1, R2: the inertial platform 12 (and accelerometers 14, 16, which integrate the signal in time) is suitable for detecting the trajectory of frame 2, but does not know its position relative to the rails: by referencing readings a, b, f to the trajectory of frame 2 detected by inertial platform 12 with the aid of offset values ​​δ4, δ6, δ8, the shape of rails R1, R2 in the vertical plane can be detected immediately.

[0042] All embodiments of System 1 and common elements of the diagnostic method according to the invention include continuous equidistant detection of the vertical distances a, b, f of each of the sensors 4, 6, 8 relative to the upper edges of rails R1 and R2.

[0043] refer to Figure 1 , Figure 2 and Figure 3B When a railway vehicle travels at speed V along rails R1 and R2 and passes through joint J, a series of distances h are obtained for each sensor 4, 6, and 8. i (That is, as mentioned above, the distances a, b, and f are corrected based on the calculated offset values). Simultaneously, data from the inertial platform 12 is acquired, and this data is processed in real time according to a known algorithm to obtain the measured values ​​a, b, and f, and the relevant distance h.i The position and orientation of frame 2 in 3D space at the same point. Figure 3B In the diagram, distances a, b, and f are associated with vertices (i.e., a', b', and f') to highlight that they were detected on a sagling rail due to curvature. The algorithm used to correlate the data from the inertial platform with the data acquired by sensors 4, 6, and 8 is known in itself and will not be described in detail further.

[0044] By processing the above data, four continuous functions were obtained (the variable X is the distance covered along the track including rails R1 and R2):

[0045] - Ga = f(X) The vertical geometry of the rail (plane XZ), calculated by inertial platform 12 and sensor 4 (distance a, with correction; the role of the inertial platform has been described above, including creating a longitudinal reference, represented by line 2R).

[0046] - Gb=f(X) The vertical geometry of the rail (plane XZ), calculated by inertial platform 12 and sensor 6 (distance b, with correction; the role of the inertial platform has been described above, including creating a longitudinal reference, represented by line 2R).

[0047] - Gf = f(X) The vertical geometry of the rail (plane XZ), calculated by the inertial platform 12 and sensor 8 (distance f, with correction; the role of the inertial platform has been described above, including creating a longitudinal reference, represented by line 2R).

[0048] - F = f(X) is the deflection calculated based on the three values ​​of the correction distances a, b, and f. Essentially, it represents a line drawn through a point P on the upper edge of the rail. i The straight line corresponds to the readings of distances a and b (P1 and P2 in the figure; i=1, 2). Then, examine the point P on the upper edge of the rail defined by distance f (P3 in the figure; i=3). i How much has the line been displaced? This displacement will be referred to as "deflection" F below.

[0049] The (vertical) geometry of the rail derived from the above function is preferably calculated based on a rail length (or wavelength) that is much shorter than conventional measurements, particularly as small as 50 cm, or even smaller.

[0050] This means that this method differs from traditional measurements, both in terms of more frequent spatial sampling and in the filters used to extract shortwave measurements. Furthermore, it must be observed that, by using known algorithms and because frame 2 is rigid, the geometry of the orbit at three different points on the vehicle can be calculated via a single inertial platform 12 (if frame 2 comprises a single element, of course).

[0051] Then, determine the point P where the value of function F exceeds the threshold. i This threshold typically depends on the type of track and traffic (however, it is at most on the order of millimeters, approximately 1 to 3 mm).

[0052] In the region of joint J (this also applies to welded joints or continuous rail lengths), the functions Ga, Gb, and Gf are essentially the same under normal conditions, i.e., under the bending conditions of joint J or the rail, which correspond to the design requirements.

[0053] Therefore, for the maximum value of the modulus of the difference (Gf-Ga), (Gf-Gb), and (Gb-Ga), at least a first (warning) threshold and a second (warning) threshold are defined, which are calculated over a length of approximately two meters or longer across joint J (or, in general, along the rail segment being inspected).

[0054] The differences (Gf-Ga) and (Gf-Gb) represent the amount of rail sag under the load applied by wheel W. Excessive sag is a cause of alarms, especially when the mounting points of sensors 4 and 6, used to measure distances a and b, on frame 2 are close to the arrangement of sensor 8, used to measure distance f.

[0055] The difference (Gb-Ga) should generally be close to zero, excluding measurement error and very small hysteresis, which also depends on the speed of the railway vehicle. If the difference (Gb-Ga) exceeds the corresponding threshold, this indicates hysteretic (hysteresis) behavior, and exceeding the given limit itself is the cause of an alarm.

[0056] Subsequently, at the moment when the maximum value of function f is detected, that is, when the curvature is maximum at joint J or at a point on the track being inspected, distances a, b, and f are calculated.

[0057] Referring to Figure 3, the values ​​m, α1, and α2 can be measured using the system 1 and diagnostic method according to the present invention, i.e.:

[0058] -m: The maximum deflection of joint J under load (i.e., the maximum value of function F).

[0059] -α1: The displacement angle of rail R1 (or rail segment) relative to the reference profile R_ID. In this example, this displacement angle is the line connecting the points on the upper edge of the railway identified by a and b. Therefore, it is one of the acute angles at the base of the triangle defined by points P1(a), P2(b), and P3(f).

[0060] -α2: The displacement angle of rail R2 relative to the reference profile R_ID. In this example, this displacement angle is the line connecting points P1 and P2 on the upper edge of the rail, defined at distances a and b. Therefore, this is another acute angle at the base of the triangle defined by points P1(a), P2(b), and P3(f).

[0061] These values ​​are calculated based on known trigonometric functions, which are not explained here for the sake of brevity.

[0062] Therefore, a potential critical condition is determined to exist in joint J (or typically at the point being inspected) if one or more of the following conditions are met:

[0063] i)m > m0

[0064] ii) α1 > α1_0

[0065] iii) α2 > α2_0

[0066] iv)α1 + α2 > α12_0

[0067] Where m0, α1_0, α2_0, and α12_0 are the threshold values ​​of parameters m, α1, α2, and α1+α2, respectively.

[0068] Basically, due to System 1 and the diagnostic method according to the invention, excessive bending of the rail under load is considered defective, especially if it occurs along a short inspection length and therefore has a high curvature, thus leading to significant fatigue of the material.

[0069] With regard to the second and third preferred embodiments shown in the table above, the following considerations apply:

[0070] Second embodiment: Deflection only

[0071] Since there are no inertial sensors (inertial platform 12 and / or accelerometers 14, 16), the functions Ga, Gb, and Gf cannot be calculated. However, thanks to distance sensors 4, 6, 8 and their calibration, the values ​​m, α1, and α2 can be determined, which are themselves an important diagnostic tool.

[0072] Third embodiment: Simplified inertia

[0073] In this embodiment of System 1, since there is no inertial platform, it is impossible to operate in the three dimensions of space; therefore, System 1 can only operate based on coordinates in the plane XZ using vertical accelerometers 14 and 16. The movement of frame 2 in the plane XZ is calculated by double integration of the signals from accelerometers 14 and 16 over time, thereby obtaining all functions Ga, Gb, Gf, and F that can be calculated using the system according to the first embodiment, although with slightly higher errors than in the first embodiment. The parameters m and α1eα2 are also calculated.

[0074] Obviously, in this case, it is crucial that sensors 4 and 6 are positioned at the correct distance from wheel W, and that all sensors are highly accurate: because the angle is measured by a “short” segment, small errors in a, f, and b will result in rotational errors in the segment, which in turn will result in rotational errors in the angle measurement.

[0075] In summary, all embodiments of the present invention define a method for diagnosing bending at a weak point in a joint J or continuous rail between rails R1 and R2 by means of a system 1 installed on a railway vehicle, wherein the method includes:

[0076] - A railway vehicle (in the diagram, V represents the longitudinal speed of the vehicle) travels along the track to pass through an inspection area (J, or a continuous rail area where ballast subsidence exists). The track consists of a pair of continuous rails or rails interrupted by joint J, and each rail can be inspected through system 1.

[0077] - During the movement of railway vehicles, a first distance a at a first point P1, a second distance b at a second point P2, and a third distance f at a third point P3 are detected, where the first, second, and third points P1, P2, and P3 are located on the top of the rail.

[0078] - Determine the graph with vertices at the first, second, and third points P1, P2, and P3.

[0079] - Determine the value of a first angle α1 defined between the edge (P1-P2) connecting the first point and the second point of the graph and the edge (P1-P3) connecting the first point and the third point of the graph, and the value of a second angle α2 defined between the edge connecting the first point and the second point (P1-P2) of the graph and the edge connecting the second point and the third point (P2-P3) of the graph.

[0080] - Determine the fourth distance value m between the third point P3 and the edge (P1-P2) connecting the first point and the second point of the figure.

[0081] - Compare the values ​​of the first angle α1, the second angle α2, and the fourth distance value m with their respective thresholds m_0, α1_0, and α2_0.

[0082] Of the three vertical distance measurements performed by sensors 4, 6, and 8, one (f) was performed under the load transmitted by the track wheel W, while the others were performed at approximately 50 and 100 cm distances on both sides (upstream and downstream in the longitudinal direction X) relative to the axis of wheel W, i.e., relative to the point of acquisition of distance f. The measurements on both sides were performed ideally without contact, without any apparent vertical load, using any available technology.

[0083] Those skilled in the art will understand that, with the system according to the invention, it is possible to address the problems of the prior art by pre-emptively and continuously diagnosing the presence of degradation conditions in the joints J between rails or in continuous rails poorly supported by ballast BL, thereby taking action before dangerous situations arise. It is not even necessary to resort to diagnostic vehicles, as the system 1 can be installed on railway vehicles commonly used for passenger or freight services along railway lines, thus gaining the further advantage of measuring under actual load conditions on the track, which may not always be reproducible by dedicated railway vehicles. The wheels W of the railway vehicle themselves serve as measuring elements, as the wheels directly apply vertical loads to rails R1, R2 at the joints J or at weak points in the rails. Once the weak point is located, regardless of its nature, calculations are performed and inferences are drawn as described above. The proposed method offers the further advantage of being suitable for installation on vehicles where no one performs diagnostic activities. Generally, the only requirement for the method according to the invention relates to the weight per axle of the vehicle-borne system 1, which must be close to the weight of commercially operating vehicles in order to apply the same loads on the track as those that these commercial vehicles would bear during normal operation.

[0084] Of course, implementation details and embodiments may vary considerably with respect to what has been described and illustrated without departing from the scope of the invention as defined by the appended claims.

Claims

1. A system (1) for diagnosing the bending of railway rails (R1, R2, J), comprising: - A frame (2), which is configured to be mounted on the railway vehicle at the wheel (W) of the railway vehicle. - A first distance sensor (4) and a second distance sensor (6) are mounted on the frame (2) and arranged on opposite sides of the wheels (W) of the railway vehicle. Each of the first distance sensor (4) and the second distance sensor (6) is configured to detect a first distance and a second distance between the top of the frame (2) and the top of the rails (R1, R2), respectively. - A third distance sensor (8) is mounted on the frame (2) and configured to detect a third distance of the frame (2) relative to the journal box (10) associated with the wheel (W) of the railway vehicle.

2. The system (1) according to claim 1, comprising at least one additional sensor (12, 14, 16) configured to determine the spatial trajectory of the frame (2) relative to the top of the rails (R1, R2) based on the first distance (a), the second distance (b) and the third distance (f).

3. The system (1) according to claim 2, wherein the at least one additional sensor comprises at least one inertial sensor (12, 14, 16) mounted on the frame (2).

4. The system (1) according to claim 3, wherein the at least one inertial sensor includes a first accelerometer (14) and a second accelerometer (16) mounted on the frame (2), each of the first accelerometer (14) and the second accelerometer (16) being an accelerometer configured to detect vertical acceleration.

5. The system (1) according to claim 4, wherein the first accelerometer (14) is mounted on the frame (2) corresponding to the first distance sensor (4), and wherein the second accelerometer (16) is mounted on the frame (2) corresponding to the second distance sensor (6).

6. The system (1) according to claim 3, wherein the at least one inertial sensor comprises an inertial platform mounted on the frame (2).

7. The system (1) according to any one of the preceding claims further includes a positioning unit (18) configured for a spatial reference of the distance detected by at least one distance sensor (4, 6, 8).

8. A method for diagnosing the bending of railway rails (R1, R2) on railway vehicles using the system (1) according to any one of the preceding claims, the method comprising: - To make the railway vehicle travel along the rails to pass through the inspection area (J). - During the movement of the railway vehicle, the first distance (a) at a first point (P1), the second distance (b) at a second point (P2), and the third distance (f) at a third point (P3) are detected, where the first, second, and third points (P1, P2, P3) are located on the top of the rail. - Identify the graph that has vertices at the first, second, and third points (P1, P2, P3). - Determine the value of a first angle (α1) defined between the edge (P1-P2) connecting the first point and the second point of the figure and the edge (P1-P3) connecting the first point and the third point of the figure, and the value of a second angle (α2) defined between the edge (P1-P2) connecting the first point and the second point of the figure and the edge (P2-P3) connecting the second point and the third point of the figure. - Determine the fourth distance value (m) between the third point (P3) and the edge (P1-P2) connecting the first point and the second point of the figure. - Compare the values ​​of the first angle (α1), the second angle (α2), and the fourth distance value (m) with their respective thresholds (m_0, α1_0, α2_0).

9. The method of claim 8, further comprising correcting the values ​​of the first distance (a, Ga), the second distance (b, Gb), and the third distance (f, Gf) based on the displacement of the frame (2) relative to the rail determined by at least one inertial sensor (12, 14, 16), and determining: - The first difference (Ga-Gb) between the corrected value of the first distance and the corrected value of the second distance. - The second difference (Ga-Gf) between the corrected value of the first distance and the corrected value of the third distance. - The third difference (Gb-Gf) between the corrected value of the second distance and the corrected value of the third distance.

10. The method of claim 8 further comprises comparing the first difference (Ga-Gb), the second difference (Ga-Gf), and the third difference (Gb-Gf) with their respective thresholds.

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