Braking device monitoring system, and corresponding method

Abstract

Braking Device Monitoring System and Corresponding Method. The invention relates to a monitoring system (1) for a braking device of a railway vehicle, the braking device comprising at least one brake pad, wherein the system comprises: - a marker (2) intended to be positioned on or near the brake pad, - a portable image acquisition device (4), configured to be handled by an operator and to acquire one or more images of the pad with the marker positioned on or near it, the portable image acquisition device also being configured to provide said image(s) to an image processing means (8) configured to estimate at least one value for the thickness of the pad from said image(s). The invention also relates to a corresponding monitoring method. Figure for the abstract: Fig. 1.

Description

Title of the invention: Monitoring system for a braking device, and corresponding method. Technical field

[0001] The present invention relates to the field of vehicle braking, and more particularly to the monitoring of vehicle braking components. More specifically, the invention relates to the monitoring of braking components in railway vehicles. Previous technique

[0002] The braking system is one of the safety components of any vehicle in general. In the specific case of railway vehicles, each wagon or carriage is equipped with brakes to allow for more efficient and rapid slowing and stopping of the train. Such brakes, like the brakes of any other vehicle, wear out and can malfunction in various ways. Brake failure can have numerous consequences, ranging from a damaged wheel to a derailment or a collision.

[0003] It is known to monitor the components, particularly pneumatic and / or mechanical, of the braking system of railway vehicles. Monitoring of mechanical components is generally carried out via manual inspection of the braking system by maintenance personnel, which is time-consuming and expensive. Furthermore, such monitoring is not always centralized, so the inspection history, in the absence of any detected fault, is not necessarily kept or recorded together.

[0004] In the railway sector, a wheel is generally a steel object with various identifiable parts, notably a tread on which the wheel, and therefore the railway vehicle, rests on a rail. A braking assembly comprises a brake shoe, or brake pad, and a brake shoe holder, or shoe carrier, which are held together by a wave spring (or wrench). The spring allows the shoe to be removed when it becomes too worn. The braking assembly is attached to a device or mechanism that can move the shoe into contact with the wheel's tread. This contact causes energy dissipation from the wheel and thus slows the train.

[0005] However, contact and friction also cause wear on the sole, which will ultimately lead to its replacement.

[0006] It is known to perform brake inspections during routine inspections, which requires the rail vehicle to be at a complete stop and an operator to visually inspect the brakes. If the operator has any doubt as to the condition of the brake shoe, A metal ruler can be used to determine if the remaining thickness on the sole is sufficient for its continued use.

[0007] Document DE 10 2008 011 288 describes a device for monitoring the thickness of a brake shoe in a vehicle's braking system, the brake lining interacting with a friction element such as a brake disc. The shoe is equipped with at least one passive transponder from an RFID system. When a defined wear limit of the shoe is reached, the passive transponder is modified and / or destroyed by contact with the friction element such that the transponder, after being read by an RFID system, produces a signal that is modified compared to the expected signal or does not send a signal at all.

[0008] US Patent 2013 / 083188 relates to a system for evaluating a component of a vehicle, such as a rail vehicle's undercarriage. An imaging component can acquire image data for a target area of ​​the vehicle in which at least part of the component is visible. The target area can be illuminated by a lighting device that is, for example, horizontally offset from the imaging device to highlight the three-dimensional structure in the target area by creating shadows in the image data. A set of points corresponding to the component can be identified in the image data using the shadows. A measurement for at least one attribute of the component can be calculated from the set of points.

[0009] Document EP 3 597 495 relates to a method for monitoring a braking system of a railway vehicle, the braking system comprising at least one brake shoe acting on a tread. The method comprises, via a computerized braking system monitoring device, the steps of recording an image comprising the braking system of the railway vehicle with a sensor system, determining the position of the brake shoe on said image, and determining the wear status of the brake shoe from said image.

[0010] However, such devices are not always simple to implement, which limits their use. Furthermore, such devices and methods known in the prior art are not always reliable and effective in assessing the condition of a railway vehicle's braking system. Description of the invention

[0011] The present invention aims to solve the various technical problems stated above. In particular, the present invention aims to provide a monitoring system that facilitates the determination of the wear condition of a braking device. Furthermore, the present invention aims to provide a monitoring system that allows to improve knowledge of the wear condition of a braking device, and in particular the wear condition of a brake shoe.

[0012] Thus, according to one aspect, a monitoring system for a braking device of a railway vehicle is proposed, the braking device comprising at least one braking shoe. The system comprises: - a reference point, for example an optical target, intended to, or even configured to, be positioned on or near the braking surface, - a portable image acquisition device, configured to be handled by an operator and to acquire one or more images of the sole, including the thickness of the sole, with the marker positioned on or near it.

[0013] The portable image acquisition device is also configured to provide said image(s) to an image processing means configured to estimate at least one thickness value, preferably a plurality of thickness values ​​such as a discrete thickness distribution, of the sole from said image(s).

[0014] Thanks to the combination of the marker and the image processing means, it becomes possible to reliably determine the wear condition of the braking device, even when using a portable image acquisition device. Thus, even in the event of parallax or misalignment during image capture by the operator, the system according to the present invention is capable of correcting the resulting distortion in the image, in order to reliably determine the condition of the braking device. It therefore becomes possible to easily move and transport the monitoring system, so that the required measurements can be carried out quickly and efficiently.

[0015] Preferably, the portable image acquisition device is included in, or is formed by, a smartphone, a tablet or any other portable electronic device configured to connect to the internet.

[0016] The portable device of the system according to the present invention also features The advantage lies in its ability to be integrated into a connected electronic device, such as a smartphone or tablet. Since these types of electronic devices are widespread in society, this makes the monitoring system easier, more intuitive, and faster for the operator to use.

[0017] Furthermore, such a monitoring system can also be quickly and easily deployed within a company or a network of partners, simply by providing the reference point and possibly corresponding software or an application. This ease of deployment and use can, in particular, allow for a greater number of measurements and thus improved monitoring of the various braking devices.

[0018] Preferably, the image processing means is configured to identify the marker on the image(s), to identify at least one distinctive element of the marker on the image(s), for example a specific geometric shape or a plurality of points delimiting a specific geometric shape, and to identify at least partially the outline of the thickness of the sole on the image(s).

[0019] As previously stated, the monitoring system is capable of determining the thickness of the brake pad, even when the image(s) were taken with parallax or any other misalignment with respect to the braking device. To this end, the processing means of the system according to the invention is configured to identify and determine distinctive features of the reference mark, and to identify at least a portion of the pad's contour. Identifying both the reference mark, whose actual dimensions are known, and at least a portion of the pad, makes it possible to deduce an actual dimension of the pad by comparison with one or more dimensions of the reference mark. It is also possible to modify the image(s) to correct or compensate for the distortion introduced by the operator during the shooting process, before identifying and determining distinctive features of the pad.

[0020] Preferably, the image of the sole taken by the portable image acquisition device comprises a plurality of pixels having two sides of the same dimension, and the image processing means is configured to modify data of said image so that the sides of a pixel, preferably of each pixel, correspond to the same real length, or distance.

[0021] The image processing means is thus configured to rectify the image taken by the operator, based on the geometry of the reference frame appearing on it, so that the pixel dimensions correspond to the same actual length. Such image rectification makes it possible, in particular, to take into account any parallax during image capture, and the distance between the portable device and the reference frame. This processing step can be performed at the beginning of image processing, on the entire image, before any measurement of the sole thickness but after identification of the reference frame on the image, or it can be performed at the end of image processing, on the coordinates of the pixels forming the principal edges of the sole.In other words, such a correction can be applied to the entire image, or only to the pixels used to estimate the thickness of the sole, or only to the thickness values ​​obtained from the image taken by the portable acquisition device.

[0022] Preferably, the image processing means is configured to modify said image with mathematical processing and / or with an artificial intelligence-based model, and optionally to analyze said image, for example to identify the marker and / or at least one distinctive contour element of the marker and / or at least a part of the contour of the sole thickness.

[0023] The correction performed by the image processing method amounts to applying a transformation matrix that modifies the image so that the The geometry of the coordinate system visible in the image corresponds to its known real geometry. Such a transformation matrix can be performed using mathematical processing, and / or using an artificial intelligence-based model.

[0024] Preferably, the image processing means is configured to determine a minimum value, and possibly a maximum value, of the sole thickness from said image or images.

[0025] Since the processing means is configured to determine at least a portion of the sole's contour, it is possible to perform several thickness calculations on said portion of the sole's contour. It is then possible to obtain a plurality of values, which may, in particular, highlight a homogeneity of wear on the sole, or conversely, a heterogeneity of wear indicating a fault in the adjustment or assembly of the braking system.

[0026] Preferably, the system also includes a means for identifying a brake shoe of a railway vehicle configured to provide identification elements for said brake shoe, and the system is also configured to store, in combination with the identification elements for said brake shoe, said or said brake shoe thickness values, for example one or more thickness values ​​estimated by said system at different dates.

[0027] In order to maintain a history of the thickness values ​​of monitored, unreplaced track soles, the monitoring system may also include a means of identifying the monitored sole, so that it can be easily retrieved. The identification means may be a means of capturing information related to the sole, such as a wagon number, the positioning of the various soles on that wagon, etc. Such an identification means allows, when the thickness of a sole exceeds the predetermined replacement value, the retention of the measured values ​​and their association, where applicable, with previously measured values. It is then possible to determine the wear history of a sole and, if necessary, adjust its replacement frequency, for example, if faster-than-expected wear is detected.

[0028] Preferably, the image processing means is installed in the portable image acquisition device, or is separate from the portable image acquisition device, for example is installed on a remote server, for example decentralized.

[0029] In order to process the images taken by the operator, the surveillance system may include a processing means installed in the portable device, making it autonomous and eliminating the need for a connection for data transmission. However, such an embodiment will consume more resources of the portable device, whether in terms of energy (battery) or computing power. Alternatively, a remote processing means may be provided, for example On a server: in this case, the portable device transmits the images taken by the operator to the remote processing device, thus limiting the processing performed by the portable device. Furthermore, the data processed by the remote server can then be stored directly and centrally after it is obtained.

[0030] Preferably, the marker comprises a first zone of a first color and a second zone of a second color, the first color mainly reflecting wavelengths close to 800nm ​​and the second color mainly reflecting wavelengths close to 400nm.

[0031] To improve the identification of the coordinate system and its known geometric characteristics on the image(s) taken by the operator, the coordinate system comprises two zones configured to facilitate the detection of their interface. Advantageously, the two zones are provided with distinct colors, ideally close to the colors used in color detection systems commonly employed in electronic devices. Such a choice of colors makes it easier and more precise to distinguish them, regardless of the lighting conditions, leading to a better understanding of the coordinate system's characteristics on the image(s) taken by the operator.

[0032] Preferably, the portable image acquisition device is configured to acquire one or more images of an exposed face of said sole, and the marker is intended or configured to be positioned in the same plane, or substantially parallel and / or near a plane in which said exposed face of the sole extends.

[0033] Positioning the reference mark in a plane identical to, or very close to, and / or substantially parallel to, that of the exposed face of the sole allows for a more reliable estimate of the sole's thickness, closer to the exact value. Indeed, by processing the image taken by the portable device from the reference mark visible on it, the applied processing provides better results for elements located in a plane identical to, or very close to, and substantially parallel to that of the reference mark.

[0034] According to another aspect, a method for monitoring a braking device of a railway vehicle is also proposed, the braking device comprising at least one braking shoe, comprising: - a step involving the positioning of a reference point, for example an optical target, on or near the braking surface, - an image acquisition step by an operator using a portable image acquisition device, to acquire one or more images of the sole, including the thickness of the sole, with the marker positioned on it or nearby, - a processing step of said image(s) to estimate at least one value of the thickness of the sole from said image(s).

[0035] Preferably, the image processing step includes a step of identifying the marker and / or at least one distinctive element of the marker contour on the image or images, for example a specific geometric shape or a plurality of points delimiting a specific geometric shape, optionally a step of straightening the image, and a step of identifying at least partially the contour of the sole thickness on the image or images.

[0036] Preferably, the processing step of said image(s) includes a step of determining a minimum value, and possibly a maximum value, of the thickness of the sole from said image(s).

[0037] Preferably, the method also includes a step of identifying the sole of the braking device of a railway vehicle, allowing to obtain identification elements of said sole, and the method also includes a step of memorizing, in combination with the identification elements of said sole, said or said thickness values ​​of the sole, for example one or more thickness values ​​estimated at different dates. Brief description of the drawings

[0038] [Fig-1] Fig. 1 is a schematic representation of a monitoring system according to the present invention;

[0039] [Fig.2] Fig.2 schematically represents an example of an image of a braking device, taken by the portable device of the system illustrated in Fig.1;

[0040] [Fig.3] The [Fig.3] illustrates the image of the [Fig.2], processed by a processing means in order to compensate for distortion and to identify the corners of the coordinate system;

[0041] [Fig.4] The [Fig.4] illustrates the image of the [Fig.3] in which part of the outline of the sole has been identified;

[0042] [Fig. 5] [Fig. 5] illustrates the image of [Fig. 4] in which several sole thickness values ​​have been determined; and

[0043] [Fig.6] The [Fig.6] is a flowchart of the process implemented by a monitoring system according to the present invention. Description of the implementation methods

[0044] Figure 1 represents a monitoring system 1 according to the present invention. The monitoring system 1 comprises an optical marker 2, for example an optical target, and a portable image acquisition device 4, configured to take images of a braking device with the marker 2. The monitoring system 1 may also include a remote server 6 receiving the images taken by the portable device 4, in order to process and / or store and / or make them available.

[0045] The reference mark 2 is used to allow estimation of the lengths of the elements visible on the images taken by the portable device 4, and possibly to allow image processing in order to correct defects related to the angle of image capture by the portable device 4.

[0046] For this purpose, the marker 2 may include one or more graduations, for example two graduations perpendicular to each other, or may have predefined dimensions which are known by the monitoring system.

[0047] Alternatively, or in addition, the frame 2 may comprise a first zone 2a and a second zone 2b, which are separated by an interface extending in two directions in space, and preferably with known dimensions. The first and second zones 2a, 2b are chosen so as to exhibit a significant contrast with each other when photographed, in order to determine precisely and easily the position of the interface separating said two zones 2a, 2b. Thus, the first zone may comprise, or even be entirely covered by, a first color reflecting mainly wavelengths close to 800 nm, for example red, and the second zone may comprise, or even be entirely covered by, a second color reflecting mainly wavelengths close to 400 nm, for example blue.The choice of such different and widely spaced colours in the visible spectrum allows for better contrast between the two areas in the images taken by the portable device 4. In particular, the choice of two colours commonly used for colour detection in electronic devices (RGB system: red-green-blue) also improves the contrast of the images made by the portable device 4, and therefore allows for better determination of the position of the interface, and thus its length, between the two areas 2a, 2b.

[0048] Such a choice facilitates the analysis of the image by a processing means, regardless of the lighting of the image in particular.

[0049] Thus, the marker 2 can be in the form of a red rectangle, with a blue outline on the periphery of the red rectangle.

[0050] The marker 2 can also be configured so that it can be easily positioned on a braking device. For example, the marker 2 can be magnetic, or have an adhesive contact surface, to allow the operator to easily position it on the braking device and remove it from it.

[0051] The monitoring system 1 also includes a portable image acquisition device 4. The portable device 4 is configured to take images and to store and / or transmit them. The portable device 4 may therefore include a camera, preferably digital, and a screen enabling the operator to view the field before image capture and / or the images captured.

[0052] The portable device 4 may also include an identification means 7, for example, a means for entering information such as the number of the railway vehicle being examined (wagon or car), the bogie being examined (front or rear), the wheel being examined (wheel number), and the position of the braking device relative to the wheel (left or right). The identification means 7 may be a set of fields to be completed using a keyboard or by selecting from a drop-down menu, or a generic illustration of a railway vehicle with representations of braking devices to be selected for entry. In particular, for known wagons, the data relating to the braking devices may be retrieved and pre-filled once the wagon number has been entered by the operator.

[0053] Once the braking device identification data has been entered and the image(s) taken, the information can then be stored on the portable device 4, possibly after processing, or transmitted to the remote server 6, possibly after processing and / or for further processing. The portable device 4 therefore advantageously includes a means of transmitting information to the remote server 6, for example via an internet connection, such as a Wi-Fi connection or a mobile connection (3G, 4G, etc.). In order to limit the use of the portable device 4's resources, the identification data and the images taken of the braking device can be transmitted to the remote server 6 without specific processing, in particular without implementing the image processing steps detailed below.In this case, image processing is carried out at the remote server 6, for example by an image processing means 8, and the data is also stored at the remote server 6, for example in a memory 10. However, it is understood that the image processing means 8 and the memory 10 can also be provided in the portable device 4.

[0054] The portable device 4 may thus comprise or be formed by a portable electronic device such as a smartphone, tablet, or other similar product. The portable device 4 of the monitoring system 1 may therefore be a portable electronic device such as a smartphone, tablet, or other similar product, with corresponding software, or an application, enabling the implementation of the method according to the invention. Such an embodiment then makes it possible to deploy the monitoring system 1 quickly and easily within a company or a network of companies, by providing the application to be downloaded onto the electronic device of the various operators required to perform the method, and by supplying them with the corresponding identifier 2.

[0055] The processing means 8 allows the images to be processed in such a way as to allow the measurement of a dimension, preferably the thickness, of an organ of the device braking, particularly the sole. The different treatment stages will be explained below, in relation to figures 2 to 5.

[0056] Figures 2 to 5 show different views of a braking device 12, before, during, and after processing by the monitoring system 1 according to the present invention. The braking device 12 comprises a brake shoe, or shoe holder, 14 movably mounted on a railway vehicle bogie, and a brake shoe 16 removably mounted on the brake shoe 14, notably by means of a wave spring. The removable mounting of the brake shoe 16 on the brake shoe 14 is intended to allow for easy replacement of the latter when it becomes too worn. The brake shoe 16 is integral with the brake shoe 14 such that the movement of the brake shoe 14 towards the tread 18 of a wheel 20 of the bogie also causes the movement of the brake shoe 16 towards the tread 18, and thus friction between the two.

[0057] Figure 2 illustrates an example of an image taken by an operator with the portable image acquisition device 4 described above. Prior to taking the image, the operator positioned the marker 2 on the braking device 12 to be monitored, for example by magnetizing it onto the jaw 14.

[0058] During image acquisition, the operator was able to introduce parallax between the image axis and the perpendicular to the photographed surfaces (brake shoe flank 16, brake shoe flank 14, reference point 2), i.e., the direction parallel to the axis of the wheel axle 20. Such parallax therefore leads to a distortion of the shape of the photographed surfaces, with a vanishing point that is not located on the normal to the photographed surfaces. The distorted elements visible in the image of [Fig. 2] thus appear distorted compared to reality. For example, due to the distortion, reference point 2 may appear in [Fig. 2] as a parallelogram or as a trapezoid.

[0059] In order to allow a reliable determination of lengths, in this case of thicknesses, the image processing means 8 is configured to distort the images in such a way as to allow measurements to be taken.

[0060] Figure 3 represents a first step in processing the image illustrated in Figure 2, carried out in particular by the image processing means 8. In Figure 3, the processing means 8 is configured to identify characteristic points of the frame 2, in this case the four corners PO, PI, P2, P3 of the rectangular interface separating the first zone 2a and the second zone 2b. Such detection of the frame 2, and of characteristic points of the frame 2, can be carried out by the processing means 8, by mathematical processing and / or by means of an artificial intelligence-based model, whether trained or not.

[0061] Since the geometry of the frame 2 is known by the processing means 8, the latter can then modify the image so that the characteristic points of the frame 2 identified in [Fig. 2] correspond to the known geometric shape of the frame 2, in this case a rectangle. Such a modification of the image, or rectification, makes it possible to limit the effects of the parallax present during the image capture and to obtain a "rectified" image for which the parallax would be zero, that is to say, for which the image axis is parallel to the axis of the axle of the wheel 20. The processed elements visible in the image of [Fig. 3] have therefore been rectified. In the rectified image, the square pixels then have sides corresponding to the same actual length.

[0062] In the described case, such rectification is performed at the beginning of image processing, on all or part of the image. However, it is also possible to determine, in pixels, the different thickness(es) of the sole from the original image taken by the portable acquisition device, and then perform the rectification at the end of image processing, on the thickness values ​​thus obtained. It is nevertheless important to note that, in this latter case, the determination of the different thickness(es) of the sole can only be made on the values ​​obtained after rectification, and not on the original image.

[0063] Once the reference frame 2 visible on the image has been rectified, it is then possible to determine a real dimension corresponding to the size of the image pixels. Such a dimension can be determined from the known dimensions of the reference frame 2, or from the graduations visible on the frame, if applicable. This correspondence thus eliminates the need to consider the distance between the portable device 4 and the reference frame 2 during image acquisition. It is then possible to determine the length of the various elements visible on the image of [Fig. 3], in the plane or near the plane in which the reference frame 2 extends.

[0064] In [Fig. 4], the processing means 8 then determines the contours of the sole of braking element 16, and more specifically the main edges 16a, 16b, the spacing of which corresponds to the thickness of the braking surface to be measured. Such detection may include determining the complete contour of the braking surface 16 before identifying the main edges, and / or may include determining the corners of the braking surface 16 to allow for the identification of the main edges subsequently, and / or even the direct determination of said main edges.

[0065] Such determinations of edges or contours or corners of the braking sole 16 can in particular be carried out using a processing means 8 comprising mathematical processing and / or a model based on artificial intelligence and configured to analyze an image. The processing means 8 can thus include a machine learning-based model, in particular trained or automatic.

[0066] As illustrated in [Fig. 5], once the edges of the brake pad 16 are identified, the processing means 8 then determines different values ​​for the thickness of said brake pad 16, i.e., different lengths of segments 18a, 18b, 18c perpendicular to the two edges. All the different values ​​can be recorded, or only the minimum and maximum values ​​can be recorded by the memory 10, along with the identification elements of said braking device 12. Similarly, the image with the different lengths mentioned therein can also be stored, so as to know both the value and the position of each measurement taken on the image by the processing means 8.

[0067] Figure 6 illustrates a flowchart of the monitoring process 20 according to the present invention.

[0068] In a first step 22, the marker 2 is positioned on the braking device 12, preferably on the jaw 14 of the braking device 12.

[0069] In a second step 24, one or more images are taken of the braking device 16 and of the marker 2, with a portable device.

[0070] In a third step 26, the frame 2 and its outline are identified on the image taken by the portable device, for example using mathematical processing and / or a model based on artificial intelligence. Then, in a fourth step 28, the image is rectified so that the frame 2 represented on it has the same geometric shape as the known shape of the frame 2.

[0071] In a fifth step 30, the two main edges of the brake pad 16 are identified on the rectified image, for example using mathematical processing and / or an artificial intelligence-based model.

[0072] Finally, in a sixth step 32, several spacing values ​​are determined for the two main edges of the braking pad 16, corresponding to different thickness values.

[0073] Thus, thanks to the reference point and the processing method, it becomes possible to reliably and efficiently determine different values ​​for the thickness of a brake pad photographed by an operator with a handheld device, correcting for any parallax and eliminating the influence of the distance between the handheld device and the brake pad. Image capture can then be carried out with fewer constraints and with any type of electronic device equipped with an image capture capability, including a smartphone, which simplifies its use by the operator and also its deployment within a company. Finally, by facilitating image capture, and therefore measurement, it becomes possible to multiply the measurements and therefore to retrieve a larger amount of data that can be centralized to allow a statistical analysis of brake pad wear.

Claims

Demands

1. A monitoring system (1) for a braking device (12) of a railway vehicle, the braking device (12) comprising at least one braking pad (16), wherein the system (1) comprises: - a marker (2), for example an optical target, intended to be positioned on or near the braking pad (16), - a portable image acquisition device (4), configured to be handled by an operator and to acquire one or more images of the pad (16), in particular of the thickness of the pad, with the marker (2) positioned on or near it, the portable image acquisition device (4) also being configured to provide said image(s) to an image processing means (8) configured to estimate at least one thickness value, preferably a plurality of thickness values ​​such as a discrete distribution of thicknesses, of the pad (16) from said image(s).

2. System (1) according to claim 1, wherein the image processing means (8) is configured to identify the marker (2) on the image(s), to identify at least one distinctive feature of the marker (2) on the image(s), for example a specific geometric shape or a plurality of points delimiting a specific geometric shape, and to identify at least partially the outline of the thickness of the sole (16) on the image(s).

3. System (1) according to claim 1 or 2, wherein the image processing means (8) is configured to determine a minimum value, and optionally a maximum value, of the thickness of the sole (16) from said image or images.

4. A system (1) according to any one of the preceding claims, further comprising a means for identifying a brake shoe of a braking device (12) of a railway vehicle configured to provide identification elements for said brake shoe (16), and wherein the system (1) is also configured to store, in combination with the identification elements for said brake shoe, said or said brake shoe thickness values, for example a or several thickness values ​​estimated by said system (1) at different dates.

5. System (1) according to any one of the preceding claims, wherein the image processing means (8) is installed in the portable image acquisition device (4), or is separate from the portable image acquisition device (4), for example is installed on a remote server (6), for example decentralized.

6. System (1) according to any one of the preceding claims, wherein the marker (2) comprises a first zone (2a) of a first color and a second zone (2b) of a second color, the first color mainly reflecting wavelengths close to 800nm ​​and the second color mainly reflecting wavelengths close to 400nm.

7. Method (20) of monitoring a braking device (12) of a railway vehicle, the braking device (12) comprising at least one braking shoe (16), comprising: - a step (22) of positioning a marker (2), for example an optical target, on or near the braking shoe (16), - a step (24) of image acquisition by an operator using a portable image acquisition device, to acquire one or more images of the shoe, in particular of the thickness of the shoe, with the marker (2) positioned on or near it, - a step of processing said image(s) to estimate at least one value of the thickness of the shoe from said image(s).

8. A method (20) according to claim 7, wherein the image processing step includes a step (26) of identifying the marker (2) and / or at least one distinctive feature of the marker contour on the image(s), for example a specific geometric shape or a plurality of points delimiting a specific geometric shape, optionally a step (28) of straightening the image, and a step (30) of identifying at least partially the contour of the sole thickness on the image(s).

9. A method (20) according to claim 7 or 8, wherein the image processing step (or steps) comprises a step (32) for determining a minimum value, and optionally a value maximum, of the thickness of the sole from said image(s).

10. A method (20) according to any one of claims 7 to 9, further comprising a step of identifying the sole of the braking device of a railway vehicle, enabling the obtaining of identification elements of said sole, and wherein the method also comprises a step of storing, in combination with the identification elements of said sole, said or said thickness values ​​of the sole, for example one or more thickness values ​​estimated at different dates.

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