NL2035850B1 - Improved wheel detector device with background field compensation - Google Patents
Improved wheel detector device with background field compensation Download PDFInfo
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- NL2035850B1 NL2035850B1 NL2035850A NL2035850A NL2035850B1 NL 2035850 B1 NL2035850 B1 NL 2035850B1 NL 2035850 A NL2035850 A NL 2035850A NL 2035850 A NL2035850 A NL 2035850A NL 2035850 B1 NL2035850 B1 NL 2035850B1
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- 238000000034 method Methods 0.000 claims abstract description 14
- 238000004891 communication Methods 0.000 claims abstract description 7
- 238000004590 computer program Methods 0.000 claims abstract description 4
- 238000001514 detection method Methods 0.000 claims description 81
- 238000012360 testing method Methods 0.000 claims description 54
- 230000004907 flux Effects 0.000 claims description 16
- 230000000694 effects Effects 0.000 claims description 3
- 230000005415 magnetization Effects 0.000 claims description 2
- 239000000758 substrate Substances 0.000 claims 1
- 238000005259 measurement Methods 0.000 description 8
- SEWHDNLIHDBVDZ-UHFFFAOYSA-N 1,2,3-trichloro-4-(2-chlorophenyl)benzene Chemical compound ClC1=C(Cl)C(Cl)=CC=C1C1=CC=CC=C1Cl SEWHDNLIHDBVDZ-UHFFFAOYSA-N 0.000 description 3
- 230000000875 corresponding effect Effects 0.000 description 3
- 230000003137 locomotive effect Effects 0.000 description 3
- 230000035945 sensitivity Effects 0.000 description 3
- 238000012935 Averaging Methods 0.000 description 2
- 230000005355 Hall effect Effects 0.000 description 2
- 230000001133 acceleration Effects 0.000 description 2
- 230000002411 adverse Effects 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- QVFWZNCVPCJQOP-UHFFFAOYSA-N chloralodol Chemical compound CC(O)(C)CC(C)OC(O)C(Cl)(Cl)Cl QVFWZNCVPCJQOP-UHFFFAOYSA-N 0.000 description 1
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- 238000006731 degradation reaction Methods 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 238000013213 extrapolation Methods 0.000 description 1
- 230000005426 magnetic field effect Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B61—RAILWAYS
- B61L—GUIDING RAILWAY TRAFFIC; ENSURING THE SAFETY OF RAILWAY TRAFFIC
- B61L1/00—Devices along the route controlled by interaction with the vehicle or train
- B61L1/16—Devices for counting axles; Devices for counting vehicles
- B61L1/163—Detection devices
- B61L1/165—Electrical
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- Engineering & Computer Science (AREA)
- Automation & Control Theory (AREA)
- Mechanical Engineering (AREA)
- Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
Abstract
Device, method and computer program product for detecting a wheel on a rail track. The device is placed on or near a lateral side of the rail track and comprises: one magnet for providing a magnetic field; a first sensing unit for sensing a first magnetic field value of the provided magnetic field; a second sensing unit for sensing a second magnetic field value, at least one processor in communication with the first sensing unit and the second sensing unit, wherein the at least one processor is configured to obtain the first magnetic field value from the first sensing unit, obtain 10 the second magnetic value from the second sensing unit, calculate a background compensated magnetic field value on the basis of the first and second magnetic field values, detect the passing of a wheel on the rail track near the device on the basis thereof. Figure 3a
Description
Improved wheel detector device with background field compensation
The present invention relates to an improved wheel detector device with background field compensation, a method for detecting a train wheel with background field compensation and a computer program product for detecting a train wheel with background field compensation.
In many applications concerning rail tracks, such as in rail transport with trains, it is beneficial to obtain information on the whereabouts of train vehicles. Many marshalling yards, especially those without electrified systems, lack safety systems.
Detection of wheels on a rail track using e.g. a Hall effect device is shown for instance in
US 4,524,932 A. Here the Hall effect device is to be placed in a pole-to-pole hole drilled through a permanent magnet to create a magnetic flux null in order to avoid saturating the Hall element. The detector is configured to detect the passing of railroad car wheels along the track by the change in the flux level from the permanent magnet. With this single apparatus, it is impossible to detect in which direction a passing train is going.
Patent documents US 2007/0001059 Al and WO 2017/045888 Al are further examples of where multiple sensors are used to determine a direction and speed of train vehicles.
Patent document EP 1 362 759 A1 describes also a train wheel sensor comprising a first coil that generates an alternating magnetic field and a second coil of equal area that is axially aligned to the first coil to produce two alternating magnetic fields in opposite direction in order to evaluate the presence and movement direction of the train wheel.
Patent document US 2010/235123 A1 concerns an example of a method of locating a wheel of a rail vehicle.
In a previous patent application WO202/004800, the present Applicant has described a method and device for detecting a direction of motion of a wheel on a rail track, comprising least one magnet for providing a magnetic field; a magnetic field sensor for sensing a magnetic field value indicative for a flux density, or a change in the flux density, of the provided magnetic field; at least one processor in communication with the magnetic field sensor, wherein the at least one processor is configured to: obtain a plurality of the magnetic field values for respective times from the magnetic field sensor; and to analyse the obtained plurality of magnetic field values such that a direction of motion of a wheel passing the device is obtained.
Yet, the change of magnetic field sensed by the magnetic field sensor of such prior art devices may not always accurately represent the passing of a wheel due to other external influences that are also affecting the magnetic field in the vicinity of the rail track. For example, when using permanent magnets to provide a magnetic field, temperature may affect the magnetic field value provided by the magnets. It has also been observed that some trains contain large coils creating de or low frequency parasitic magnetic fields. Such de or low frequency magnetic field may also derive from the circulation of current in or around the rail track, and/or may be created by Villar effect. Any one of these other external influences contribute to a background magnetic field which may affect the detection of the wheel using a magnetic field sensor.
In the context of the present application, the term “perturbation” is preferably used to describe a (desired) magnetic influence created by a wheel passing. The term “anomaly” is preferably used to describe a magnetic influence created by a de or low frequency coil passing. The term “offset” is preferably used to describe a pseudo-stationary influence created for example by temperature. Any influence affecting a normal magnetic field at the magnetic field sensor may be more generally referred as a disturbance, wherein the normal magnetic field is a magnetic field in a predefined reference situation without train passing. The term ‘measurement error component’ is preferably used to refer to a component of the sensed signal which is not related to the perturbations created when a wheel is passing. This measurement error component may be associated to a ‘background magnetic field’ due the sum of the normal magnetic field and all disturbances affecting the magnetic field sensor except the perturbations created by a wheel passing.
It is an object among objects of the present patent disclosure to address the above limitations and further improve the detection of a wheel on a rail track.
An object, next to other objects, is met by a device according to claim 1. The device is for detecting a wheel on a rail track and is configured to be placed on or near a lateral side of the rail track. The device comprises: - at least one magnet for providing a magnetic field; - a first magnetic field sensing unit for sensing a first magnetic field value indicative for a flux density, or a change in the flux density, of the provided magnetic field; - a second magnetic field sensing unit for sensing a second magnetic field value indicative of a background magnetic field component, - Atleast one processor in communication with the first magnetic field sensing unit and the second magnetic field sensing unit, wherein the at least one processor is configured to: - obtain the first magnetic field value from the first magnetic field sensing unit, - obtain the second magnetic value from the second magnetic field effect sensing unit, - calculate a background compensated magnetic field value on the basis of the first magnetic field value and the second magnetic field value, - detect the passing of a wheel on the rail track above the device on the basis of the calculated background compensated magnetic field value.
In this way, the accuracy of the detection can be improved, since the detection may be based on a corrected magnetic field value in which a background magnetic field component has been compensated. Typically when a wheel passes nearby the magnet, the wheel acts as a magnetic shunt or magnetic field altering element disturbing the magnetic field of the magnet. The term “background” is in that sense to be understood as the setting in which the sensing of the passing of a wheel is realised, ie. when at least one or more phenomena altering the magnetic field provided by the magnet, other than the wheel passing the device, are considered. The background magnetic field component is then indicative of a change in the flux density of the provided magnetic field due to one or more external influences other than the passing of the wheel above the device. The background magnetic field component may be seen as creating a measurement error component which has to be filtered out of the first magnetic field value. Such a measurement error component may include among others a basic component (normal magnetic field at the magnetic field sensor).a pseudo-stationary offset component (influence of temperature for example) and an impulse component for anomalies affecting the magnetic field provided by the magnet (passing of a dc field for example). By sensing a magnetic field value indicative of the background magnetic field component, the one or more external influences potentially adversely affecting the detection of the wheel may then be taken into account and compensated/removed to increase the accuracy of the detection of a wheel.
Although arranged for detecting the passing of a wheel, the device could be arranged for the detection of other events in general, where the events may be identified by a disturbance of the magnetic field provided by the magnet. The principle of the detection device described here is therefore not limited to detecting of the passing of a wheel insofar as the concept of a device with background field compensation as disclosed here may also be declined accordingly for other types of detection devices, for instance for devices for the detection of the removal, the displacement or degradation of the device with respect to the rail track. In particular the second sensor may be used to distinguish false detections of events due to a disturbance in the environment affecting both sensors (like temperature) from true detections of events (like the removal of the device from the rail track). The baseline magnetic field value on the first sensor may for example be used to determine a distance to the track with an accuracy sufficient to detect device removal. The secondary sensor may be not affected by track distance/removal. However, just as for wheel detection, in case of removal detection, the background field removal may remain important since without background field compensation any fluctuation may be mistaken for a device removal event.
According to a preferred embodiment, the second magnetic field sensing unit is arranged at a distance from the first magnetic field sensing unit. In this way, the second magnetic field value may contain different data about how the provided magnetic field is affected by the environment (external influences) than the first magnetic field value. In particular, when the first magnetic field sensing unit is arranged at a first location where the influence of the passing of a wheel near
(above) the device is significant on the first magnetic field value, it is possible by placing a second sensing unit at a second location in which the influence of the passing of a wheel is less significant to distinguish how other influences than the passing of the wheel may have atfected the first magnetic field value. The second sensing unit may then serve to observe via the second magnetic field value a background field magnetic component attributed to one or more external influences other than the passing of the wheel above the device.
According to a preferred embodiment, the first magnetic field sensing unit is disposed closer than the second magnetic field sensing unit from a wheel that is to be detected along a first direction intersecting 1n use with said wheel. In this way, the influences affected by the distance to the wheel may be compensated.
According to a preferred embodiment, the device is configured to be placed near a lateral side of the rail track. In this way, the device may be able to be installed either in between the rail tracks or outside of the rail tracks entirely to detect the passing of a massive portion of the wheel (flange on the inner side for instance, other part of the wheel when on the outside).
According to a preferred embodiment, in use the first magnetic field sensing unit is disposed closer to the lateral side of the rail track than the second magnetic field sensing unit. In this way, the influence of the passing of the wheel on the second magnetic field value may be reduced compared to the influence of the passing of the wheel on the first magnetic field value. As a side note, any influence emanating from the rail track will be less present in the first magnetic field value than the influence of the passing wheel, and by extension such an influence will be even less present in the second magnetic field value. Typically, the first and second sensing units may be at distance of each other between 1 and 10 cm, preferably between 3 and 7 cm, for instance at a distance of 5 cm. In comparison the distance between the first sensing unit and the undercarriage of a train may be between 50 to 130 cm, preferably between 80 to 110 cm, more preferably 100 cm.
According to a preferred embodiment in use the first magnetic field sensing unit and the second magnetic field sensing unit are arranged along a direction perpendicular to the lateral side of the rail. In this way, the first and the second magnetic field sensing unit mostly will be affected differently by the passing of a wheel while being equally affected by any influence constant along the direction perpendicular to the lateral side of the rail. This means that any influence affecting similarly the magnetic field along the direction perpendicular to the lateral side of the rail will be equally present in the first and second magnetic field value and may then be compensated by the device to improve the accuracy of the detection of the passing of a wheel. Typically a dc or low frequency magnetic field created by a coil in the undercarriage of the train will affect both the first and the second magnetic tield sensing units under the train substantially in the same manner. The second magnetic value would then undergo variations indicative of the passage of that coil while the tirst magnetic value would undergo variations indicative of both the passage of the coil and the passage of a wheel. Based on both the first and the second magnetic field value it is then possible to a calculate a background compensated magnetic field value undergoing variations indicative of the passage of a wheel only with greater accuracy than the first magnetic field value alone. 5 According to a preferred embodiment, in use the first magnetic field sensing unit and the second magnetic field sensing unit are in an horizontal plane at the height of a head of the track. In this way, the first magnetic field sensing unit and the second magnetic field sensing unit may detect the passing of a flange of the wheel, which is typically a massive element of the wheel {effective thus for wheel detection). Detecting a flange improves the reliability of the detection.
According to a preferred embodiment, the device is configured to be placed on a lateral side of the rail track. In this way, it may be ensured that the device stays below the head of the track rail which is preferred for safety and reliability reasons.
According to a preferred embodiment, in use the first magnetic field sensing unit is disposed closer to the head of the rail track than the second magnetic field sensing unit. In this way, the influence of the passing of the wheel on the second magnetic field value may be reduced compared to the influence of the passing of the wheel on the first magnetic field value.
According to a preferred embodiment, in use the first magnetic field sensing unit and the second magnetic field sensing unit are arranged along a vertical direction. In this way, the first and the second magnetic field sensing unit mostly will be affected differently by the passing of a wheel while being equally affected by any influence constant along the vertical direction. This means that any influence affecting similarly the magnetic field along the vertical direction will be equally present in the first and second magnetic tield value and may then be compensated by the device to improve the accuracy of the detection of the passing of a wheel. Note that for influences varying with the distance to the wheel, it is yet also possible to compensate these by taking the distance between the sensing units into account. Typically a dc or low frequency magnetic field created by a coil in the undercarriage of the train will affect mostly the first and in a smaller measure also the second magnetic field sensing units. The second magnetic value would then still undergo variations indicative of the passage of that coil while the first magnetic value would undergo variations indicative of both the passage of the coil and the passage of a wheel. Based on both the first and the second magnetic field value, and the known distance between the sensing units, it is then possible to a calculate a background compensated magnetic field value undergoing variations indicative of the passage of a wheel only with greater accuracy than the first magnetic field value alone. Typically, the first and second sensing units may be separated by a distance of the same order as the distance between the second sensing unit and the wheel, while the distance between the first sensor, respectively the second sensor, and a coil may be in the order of tens of times the distance between the sensing units. This means that a difference between the first and the second magnetic field values may compensate most of the anomalies generated by coils. Typically, the first and second sensing units may be at distance of each other between 1 and 10 em, preferably between 3 and 7 cm, for instance at a distance of 5 cm. In comparison, the distance between the first sensing unit and the undercarriage of a train (carrying a coil) may be between 50 to 130 cm, preferably between 80 to 110 cm, more preferably 100 cm.
According to a preferred embodiment, in use the first magnetic field sensing unit and the second magnetic field sensing unit are in a vertical plane at a lateral distance from the rail track matching the lateral position of a flange of a wheel. In this way, the first magnetic field sensing unit and the second magnetic field sensing unit may detect the passing of a flange of the wheel, which is typically a massive element of the wheel and thus easy to detect. Detecting a flange improves the reliability of the detection.
According to a preferred embodiment, the distance between the first magnetic field sensing unit and the second magnetic field sensing unit is selected to optimize the signal to noise ratio of the background compensated magnetic field value. By optimizing the signal to noise ratio, a higher accuracy of detection may be achieved, which is of importance in view of norms regarding the numbers of counting errors. For instance the norm EN50617-2 sets a margin of 1 false wheel detection for 10 millions of wheels passing the measuring point. By optimizing the SNR (Signal to
Noise Ratio), the high accuracy required by the norms may thus be achieved.
According to a preferred embodiment, the first magnetic field sensing unit and the second magnetic field sensing unit operate substantially synchronously. In this way, the first and second magnetic values are intrinsically correlated to the same moment in time and thus may be used to create a more accurate magnetic field value at that moment for detecting the passing of a wheel.
According to a preferred embodiment, the processor is configured to subtract the second magnetic field value from the first magnetic field value to obtain the background compensated magnetic field value. In this way. the background compensated magnetic field value may no longer contain the influence of at least one or more external phenomena other than the passing of a wheel.
In addition, a weight may be added to weight the subtraction of the second magnetic value to the first magnetic value. The weight may then for instance be calculated in view of calibration discrepancies between the sensors, and its addition may be regarded as a recalibration measure. In particular the processor may be configured to subtract a component of the second magnetic field value sensed along a sensing direction from a corresponding component of the first magnetic field value (sensed along the same direction) to obtain the background compensated magnetic field value. In this way, for one sensing direction at least, a background compensated magnetic field value without influences of at least one or more external phenomena other than the passing of a wheel may be obtained.
According to a preferred embodiment, each magnetic field sensing unit comprises one or more magnetic field sensors. A single magnetic field sensor may be sufficient in some circumstances while in others to meet safety requirements and/or norms, at least two sensors may be mandatory and/or preferred. The use of at least two sensors may allow error detection and correction methods and/or majority voting control methods.
According to a preferred embodiment, the one or more magnetic field sensors senses two components of the magnetic field in a first and second perpendicular sensing direction, wherein the first sensing direction is substantially parallel to a top side of the device, the top side being opposite a base of the device and configured to be positioned at least partially parallel with the ground when the device is placed on or near the rail track, wherein the first sensing direction is further substantially parallel to a lateral side of the device, the lateral side is arranged to be facing the lateral side of the rail, wherein the second sensing direction is substantially perpendicular to the lateral side of the device. In this way, two components of the magnetic field (Bx, Bz) may be monitored. Alternatively, according to another embodiment in which the device is configured to be positioned at least partially below the wheel when the device is placed on or near the rail track with a mounting side configured for placing the device on the lateral side of the rail, the first sensing direction is substantially perpendicular to the top side of the device and substantially parallel to a mounting side of the device, wherein the mounting side is configured for placing the device on the lateral side of the rail and the second sensing direction is substantially parallel to the mounting side of the device and substantially parallel to the top side of the device. In this way, two components of the magnetic field (Bx, By) may be monitored.
According to a preferred embodiment, the first magnetic field sensing unit and the second magnetic field sensing unit are mounted on a single PCB, wherein the PCB in use is preferably mounted parallel to the ground and perpendicular to the lateral side of the rail track. In this way, a compact and practical arrangement is offered for holding the first and second magnetic field sensing units. It is further noted that such an orientation may be preferred with regards to magnetic fields induced in the rail track and emanating from the surface of the rail. Alternatively, according to another embodiment in which the device is configured to be positioned at least partially below the wheel when the device is placed on or near the rail track with a mounting side configured for placing the device on the lateral side of the rail, the PCB may be mounted vertically with respect to the ground and optionally perpendicular to the lateral side of the rail track.
According to a preferred embodiment, the first magnetic field sensing unit and the second magnetic field sensing unit are mounted at opposite ends of the PCB. In this way, the whole surface of the PCB may be used. The distance between the first and second magnetic field sensing units may determine the dimension of the PCB.
According to a preferred embodiment, the first and second magnetic field sensing units further each comprise a testing coil for creating a test magnetic field. In this way, the reliability of the device may be improved without affecting the accuracy of the detection of the wheel. Indeed, typically adding a test magnetic field would decrease the accuracy of the detection of the wheel, yet by combining two sensing units equally affected by such test magnetic fields, the test magnetic field can be entirely compensated and be eliminated from the background compensated magnetic field value.
According to a preferred embodiment, the testing coils are electrically connected in series with each other. In this way, the testing coils will be powered at the same time, ensuring that identical and synchronous test magnetic fields will be applied to the corresponding first and second magnetic field values. This results in the background compensated magnetic field value being decorrelated from the test function.
According to a preferred embodiment, the background magnetic field component is variable over time based on any or more of the following: temperature, a passing dc or low frequency magnetic field associated with the passage of a train, a dc or low frequency magnetic field created by the circulation of current in or around the rail track, a dc or low frequency magnetic field created by Villari effect, the temporary or permanent magnetization of the rail track by any external influence.
According to another aspect of the disclosure, a method of detecting a wheel on a rail track is provided. The method is carried in a device placed on or near a lateral side of the rail track and comprising a magnetic field source for providing a magnetic field, a first and a second magnetic field sensing unit, and a processor in communication with first and second magnetic field sensing units, the method comprising the at least one processor performing the steps of: a. obtaining a first magnetic field value from the first magnetic field sensing unit indicative for a flux density, or a change in the flux density. of the provided magnetic field, b. obtaining a second magnetic field value from the second magnetic field sensing unit indicative of a background magnetic field component, c. calculating a background compensated magnetic field value on the basis of the first magnetic field value and the second magnetic field value, d. detecting the passing of a wheel on the rail track on the basis of the background compensated magnetic field value.
In this way, the accuracy of the detection of a wheel is improved since the first magnetic value obtained by the first magnetic field sensing unit may be compensated to take into account a background magnetic field component representative of a measurement error, obtained by the second magnetic field sensing unit.
According to another aspect of the disclosure, a computer program product is provided comprising computer-executable instructions for performing the method of the previous aspect, when the program is run on the device according to any one of the previous embodiments of a device.
This and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing currently preferred embodiments of the invention, wherein: - Figure 1 is a schematic side view of an embodiment of the device according to the present disclosure positioned on a lateral side of a rail carrying a rail vehicle; - Figures 2a and 2b are schematic views in perspective of respectively a first and a second embodiment of the device according to the present disclosure; - Figures 3a and 3b are side and partial section views in a longitudinal direction of the rail as indicated in Fig. 1 of respectively the first and the second embodiment of the device according to the present disclosure; - Figures 4a and 4b are schematic views of a lateral side of the rail showing the device of
Figs.1-3b for the respective first and second embodiment and showing a rail vehicle wheel in several positions compared to the device; - Figure 5 is a scheme of a part of the device housing electronics to an embodiment of the present disclosure; - Figure 6 is a schematic top view of part of a PCB part of an embodiment of the device according to the present disclosure; - Figure 7a is an array of plots showing the first and the second magnetic value according to the x direction according to an example of an embodiment of the present disclosure when an
ICM train is moving above the device, and Figure 7b shows a plot of the associated background compensated magnetic field value along the x direction; - Figure 8 shows a scatter plot of the time values of Figure 7a of both the first and the second sensing unit.
As shown in Fig. 1, a device 1 for detecting a direction of motion of a wheel on a rail track is placed on an inner lateral side of a rail 2 (also referred to further as rail track) over which a locomotive 3 is passing. The locomotive 3 is an example of a rail vehicle. The rail 2 has typically a cross section profile comprising a foot, a web extending vertically with two lateral side surfaces 30 and a head with an horizontal surface 31.
Under the locomotive 3, elements 6 creating magnetic anomalies in the form of a dc or low frequency magnetic field may be arranged. An example of such elements 6 may be so called traction coils used for instance in old trains such as ICM trains, still used on the Dutch Railway system. The device 1 is configured to be placed on or near a lateral inner side of the rail track 2.
The location of the device in use may indeed vary and two embodiments will now be discussed.
According to a first embodiment illustrated in Figures 2a. 3a and 4a, the device 1 may be arranged with a top side 26 substantially aligned with the horizontal surface 31 of the rail 2 and with a sensing side 28 oriented parallel with the lateral side 30 of the rail track and at a distance thereof.
The device 1 of the first embodiment is thus meant in use to sense the passing of a wheel from a lateral position with respect to the passing wheel. It is noted that Figure 2a shows a variation of said first embodiment with a pluggable battery 44 while Figure 3a shows another variation with a battery 44 integrated in the device 1. Yet the battery aspect is unrelated to the detection aspect and said Figures 2a. 3a and 4a should be understood as related to the same embodiment regarding the location of the device 1 in use with respect to the rail 2.
According to a second embodiment illustrated in Figures 2b, 3b and 4b, the device 1 may be arranged with a top side 26 at least below the rail track 2 and with a mounting side 28 abutting onto the lateral side 30 of the rail track 2. The device 1 of the second embodiment is thus meant in use to sense the passing of a wheel from a below position with respect to the passing wheel.
In both embodiments, similar elements will be given similar reference numbers.
The device 1 comprises in both embodiments a first magnet 12 and a second magnet 14.
These magnets 12 and 14 act as magnetic field source for providing a magnetic field. It is noted that other arrangements of one or more magnets may be used alternatively. The device 1 further comprises a first magnetic field sensor 18 for sensing a first magnetic field value indicative for a flux density, or a change in the flux density, of the magnetic field provided by the magnets. The device 1 further comprises a second magnetic field sensor 20 for sensing a second magnetic field value from the second magnetic field sensing unit indicative of a background magnetic field component. The background magnetic field component is representative of a measurement error affecting the first magnetic field value. The sensors 18 and 20 may each be capable of sensing at least two, preferably three, components of a magnetic flux among the three x, y, z directions.
The sensors 18 and 20 may be placed in a housing 16, which further contains the electronic parts of the device 1, preferably in a waterproof manner. The device 1 further comprises at least one processor 40 in communication with the first magnetic field sensor 18 and the second magnetic field sensor 20 (see Fig. 6a, 6b). In addition, the device 1 may comprise a battery 44, which is an example of power storage means, an acceleration sensor 42, which is an example of a motion sensor, and a wireless interface 48 (see Fig.5). The battery 44 may be housed inside the housing 16 (Figure 3a for instance) or alternatively may be pluggable into the housing 16 (see Figure 2a for instance). Although the device 1 could alternatively or additionally comprise a wired interface, a wireless interface is preferred due to the ease of implementation. The wireless interface 48 preferably connects via a LoRa network or a GSM network. The device 1 in addition comprises a storage unit 46, configured to store instructions for the processor 40 to execute. These instructions may take the form of firmware.
In the device 1, the first magnet 12 and second magnet 14 are distanced from each other by afirst distance e + f (see Figs. 4a and 4b), wherein the magnetic field sensor 18 is positioned such that it is capable of sensing the magnetic field originating of both the first 12 and the second 14 magnet.
As shown in the respective Figs. 3 and 4 of the two embodiments, the device 1 comprises a base 24 and a top side 26 opposite the base 24. The device 1 further comprises a first lateral side 28 extending parallel to a lateral side 30 of the rail track 2. Opposite the first lateral side 28, the device 1 comprises a second lateral side 29. In the first embodiment of figures 2a, 3a and 4a, the first lateral side 28 of the device 1 is at a distance from the lateral side 30 of the rail track 2 and is acting as sensing side. In the second embodiment of figures 2b, 3b, 4b, the first lateral side 28 is abutting against the lateral side 30 of the rail track 2 and is acting as mounting side for mounting the device onto the lateral side 30 of the rail 2.
In the first embodiment of figures 2a, 3a, 4a, the first 12 and second 14 magnets are oriented substantially perpendicular to the first lateral side 28, wherein magnetic pole directions of the first 12 and second 14 magnets are substantially perpendicular to the first lateral side 28 (that is horizontal in use). In the second embodiment of figures 2b, 3b, 4b, the first 12 and second 14 magnets are oriented substantially perpendicular to the top side 26, wherein magnetic pole directions of the first 12 and second 14 magnets are substantially perpendicular to the top side 26 (that is vertical in use). It is noted that the polarities of the first magnet 12 and the second magnet 14 are typically inverted with respect to each other. Yet, the orientation of the first 12 and second 14 magnets can also be different.
When using the x, y z axis referential illustrated in the Figures with respect to the rail 2 (and the device 1 when in use), an x axis will be referred to as extending in a longitudinal direction, i.e. along the longitudinal direction of the rail 2, a z axis will be referred to as extending in a lateral direction, i.e. perpendicular to the lateral side 30 of the rail 2, and a y axis will be referred to as extending in a vertical direction, ie, perpendicular to the horizontal surface 31 of the head of the rail 2.
The magnetic field sensor 18 is preferably positioned at substantially equal respective longitudinal distances e and f (in the x-direction) from the first and second magnets. In the shown embodiment, the sensor 18 is positioned at a vertical distance d (in the y-direction) from the magnets 12, 14. However more generally, the first and second sensors 18 and 20 are placed on a symmetry plane between the magnets 12 and 14. This is done in particular because on that symmetry plane, a component of the magnetic field in one measurement direction is the same for both magnets, as is explained in further detail below. It is noted further that both the first sensor and the magnets 12 and 14 should preferably be placed as close to the rail track as possible, such that the distance d may also be chosen to be zero.
In figure 3a, the second magnetic field sensing unit 20 may be arranged at a longitudinal distance a (in the x-direction) from the first magnetic field sensor 18. The first magnetic field sensor 18 may be arranged closer to the lateral side 28 than the second magnetic field sensor 20.
The first magnetic field sensor 18 and the second magnetic field sensor 20 may be aligned along a direction A. The direction A may be a lateral direction, extending in use perpendicular to the lateral side 30 of the rail 2. This means, in use, the first magnetic field sensor 18 may be disposed closer to the lateral side 30 of the rail track 2 than the second magnetic field sensor 20. In use, the sensors 18 and 20 may thus be aligned laterally along the direction A perpendicular to the lateral side 30 of the rail 2. In use, the sensors 18 and 20 may be configured for sensing the Bx and Bz components of the magnetic field.
For sensors sensing from the lateral side of the track like in Figures 2a, 3a, 4a, the first and second sensors 18 and 20 may be arranged relative to the magnets according to at least one or more of the following principles, a) both the first sensor and the magnet(s) should preferably be placed as close to the rail track as possible in a lateral direction, b) both sensors, respectively both magnet(s), should preferably be placed in a plane parallel to the ground, and preferably at the height of the top of the rail track to intersect in with at least a portion of a passing wheel, c) the first and second sensors should preferably be placed on a symmetry plane between the magnets (in order to get symmetric signals). This symmetry plane may be an yz plane in between the magnets 12, 14.
It is further noted that if the device is placed inside the track (in between rails} , the device may be arranged to detect a passing massive flange 5 of a wheel 4. If the device is placed on the outer side of the track, the vertical alignment may be adapted to detect a massive part on the outer side of a wheel 4.
In figure 3b, the second magnetic field sensing unit 20 may be arranged at a vertical distance a (in the y-direction) from the first magnetic field sensor 18. The first magnetic field sensor 18 may be arranged closer to the head of the rail (and thus a passing wheel) than the second magnetic field sensor 20. The first magnetic field sensor 18 and the second magnetic field sensor 20 may be aligned along a direction A. The direction A may in this embodiment be a vertical direction, extending in use perpendicular to the ground. This means, in use, the first magnetic field sensor 18 may be disposed closer to the top surface 31 of the rail track 2 than the second magnetic field sensor 20. In use, the sensors 18 and 20 may thus be aligned vertically along the direction A one above the other. In use, the sensors 18 and 20 may be configured for the sensing Bx and By components of the magnetic field.
For sensors sensing from the underside of the rail head like in Figures 2b, 3b, 4b, the first and second sensors 18 and 20 may be arranged relative to the magnets according to at least one or more of the following principles.: a) both the first sensor 18 and the magnet(s) 12, 14 should preferably be placed as close to the rail head as possible in a vertical direction, b) both the sensors 18 and the magnet(s) 12, 14 should preferably be placed in a plane perpendicular to the ground, and preferably at a lateral distance from the rail 2 matching the lateral position of a flange 5 of a wheel 4 (under the flange), c) the first and second sensors 18 and 20 should preferably be placed on a symmetry plane between the magnets 12, 14 (in order to get symmetric signals). This symmetry plane may be a yz plane in between the magnets 12, 14.
In Figure 4a, when the centre C of the flange 5 is right above the direction A, the direction
A and the lowest point L of a flange 5 are at a vertical distance h from each other along the vertical y axis. The first magnetic field sensor 18 may further in use be arranged at a lateral distance b from the flange 5 of a wheel 4 when measured along the direction A and at a lateral distance c from the lateral side 31 of the rail 2 when measured along the lateral direction z.
In Figure 4b, when the centre C of the flange 5 is aligned with the direction A, the first sensor 18 and the lowest point L of a flange 5 are above each other and at a vertical distance h from each other along the vertical y axis. The first magnetic field sensor 18 may further in use be at a lateral distance c from the lateral side 31 of the rail 2 when measured along the lateral direction (z axis).
In the first embodiment, the direction A may be vertically aligned so as to intersect in with atleast a portion of the flange 5 of a passing wheel. In other words, in use the direction A may be in an horizontal plane at least above the point L. In the second embodiment, the direction A may be laterally aligned such that the sensors 18 and 20 are under the flange 5 of a passing wheel. In other words, in use the direction A may be in a vertical plane passing through L.
The processor 40 obtains a plurality of the first magnetic field values for respective times from the first magnetic field sensor 18 and a plurality of the second magnetic field values for respective times from the second magnetic field sensor 20. The first magnetic field sensor 18 and the second magnetic field sensor 20 may in particular operate substantially synchronously to obtained paired first and second magnetic field values. The sample time difference between the sensors may preferably be substantially smaller than the sample interval. The processor 40 then calculates a background compensated magnetic field value on the basis of the first magnetic field value and the second magnetic field value, and further detects the passing of a wheel on the rail track above the device on the basis of the calculated background compensated magnetic field value. The detection of the passing of the wheel is based on the principle explained in the already cited prior art of the applicant WO202/004800, which is hereby included by reference. It is noted that although described without reference to axes, the magnetic field values referred to may be decomposed in axes components.
In essence, when a wheel passes nearby the at least one magnet, the wheel acts as a magnetic shunt, or magnetic field blocking or altering element. In other words, the magnetic field lines generated by the at least one magnet are short circuited. As the wheel passes, the magnetic field component will first decrease or increase (depending on the position of the sensor and from which side the wheel is approaching relative to the sensor) and then resp. increase or decrease.
These two different possibilities respectively indicate respective directions of motion of the wheel.
In addition, due to the presence of the magnet in the vicinity of the sensor, and the device being placeable in the vicinity of the wheel passing location along the rail, the device provides a non-uniform magnetic field in and around the device, such that even the direction of motion of symmetrical (in the direction of motion) objects such as a wheel can be detected. For these latter objects, their directions of motion would not be detectable for instance in a uniform magnetic field such as the Earth magnetic field at the Earth's surface.
Calculating the background compensated magnetic field value may comprise subtracting the second magnetic field value from the first magnetic field value to obtain the background compensated magnetic field value. It is noted that a weighted subtraction may also be envisaged.
This aspect of weighted subtraction will be later described in combination with test coils.
Figure 5 1s a scheme of a part of the device housing electronics to an embodiment of the present disclosure. The housing 16 may house the processor 40, the battery 44, the acceleration sensor 42, the wireless interface 48 and the storage unit 46, configured to store instructions for the processor 40 to execute. Some of these elements may for instance be placed on a Printed Circuit
Board (PCB) as illustrated further in Figures 6a and 6b.
Figure 6 shows a schematic top view of an embodiment of a Printed Circuit Board. Figure 6a shows a printed circuit board 41 on which the magnetic field sensors 18 and 20, the processor 40, the wireless interface 48 comprising an antenna circuit are placed. The first and second magnetic field sensors 18, 20 may be arranged on the same side of the PCB 41 and at two opposite edges 41a and 41b of the (typically rectangular) printed circuit board 41. The first and second magnetic field sensors may aligned along a direction B, which in use is to be aligned with the direction A of Figures 3a and 3B perpendicular to the lateral side 30 of the rail 2. The antenna circuit 48 may be arranged at another edge of the PCB 41.
In addition, test coils 50 and 55 may be added respectively in the proximity of the first magnetic field sensor 18 and of the second magnetic field sensor. The test coil 50, resp. 55, may be arranged to generate a test magnetic field that the first magnetic field sensor 18, resp. 20, is able to detect when operating properly. By operating over time, preferably periodically, the test coil to create a time varying test field and verifying that the expected change in the sensed magnetic field is indeed detected. the status of operation of the magnetic field sensor may be monitored. The monitoring may happen during normal operation of the device by superimposing the test field to the magnetic field provided by the magnets.
Each test coil 50, 55 may be arranged to create magnetic lines having a 45 degrees orientation with respect to a sensing direction of its respective magnetic field sensor 18, 20. In this way, the test field may influence the magnetic values sensed by the sensor in all axes x, y and z in the same manner. The magnetic field sensors 18, 20 may sense two components of the magnetic field in a first and second perpendicular sensing direction.
The test coils 50, 55 may be identical and may be electrically connected in series such that they are powered simultaneously and receive identical current. In this way, their generated magnetic fields may be identical. The processor 40 may control via control signals when the test coils 50, resp. 55, are powered, respectively unpowered in order to create the time varying test field. In an embodiment, the current through the test coils may further be reversed to double the range of testing. The test coils 50, 55 may be located precisely in the same manner with respect to their respective magnetic field sensor 18, 20. In this way, the same test field may be generated by each test coil and may have the same influence on its respective sensor, such that the testing field may become part of the background magnetic field component compensated later by the processor.
The testing may then become transparent to the detection of a wheel.
On the other hand, the identical positioning between a test coil and a respective sensor for all sensors allows as well to compare the sensitivity of the sensors (in uT/LSB, micro Tesla per
Least Significant Bit) and if necessary, recalibrate the sensors. In case of inconsistencies between the measured values representing the test fields, the sensors may be recalibrated with respect to each other.
In an embodiment, the test coils may for instance generate periodic series of pulses, The test coils, as previously mentioned, may be oriented with respect to their magnetic field sensors such that their magnetic tields at the position of sensing make an angle of 45 degrees, to influence the magnetic components on all axes equally. Yet any angle between 30 and 60 degrees may also be selected based on circumstances. From the first magnetic values of the first sensor and data related to the control signals of the test coils, an amplitude al of the pulses associated with the test field may then be obtained. For instance, averaging the samples taken when the coils are powered and averaging the samples when the coils are respectively unpowered and then subtracting these average results may allow obtaining such an amplitude of the pulses. Similarly, from the second magnetic values of the second sensor, an amplitude a2 of the pulses associated with the test field may then be obtained. Then the amplitudes al and a2 may be compared to a minimum threshold level to verify if the sensors effectively work. A gain factor may further be calculated as the ratio of the amplitudes (G= al/a2). This may be performed for each axis to obtain three gain factors, one per axis, (Gx, Gy, Gz). The gain factors may then later be used in the further data processing. For instance, the gain factors may be used taken into account when calculating the background compensated magnetic field. In particular the background compensated magnetic fields for the different axes, Bx, By, Bz, may be calculated using the following formulas:
Bx = Bxl - Gx*Bx2
By = Byl - Gy*By2
Bz = Bz1 - Gz*Bz2.
In this way, differences in sensitivity between two magnetic field sensors may be accounted for. Differences in sensitivity between magnetic field sensors may be caused by different factors, including production, different calibrations settings, different manufacturers and non-linear responses. The test coils allow thus a self-test function operating as a continuous calibration function.
In addition, because the detection of a wheel is based on the difference between the first magnetic field value and the second magnetic field value, it is then possible to select for the magnetic test field a magnetic field value having a value significantly high(er) than in a prior art situation with a single magnetic field sensor. In particular the magnetic test field value may have a value well above a general noise level. Such a high magnetic test value is then easy to detect and renders a test operation robust. The use of test coils in combination with two sensors may thus improve the robustness and accuracy of the detection and the robustness of the test in a synergetic manner. The disadvantages of the testing in terms of disturbance of the detection may be compensated by the two sensor approach, while the accuracy of the sensing may be further increased by using the testing field to recalibrate the sensors.
It 1s noted that the principle of using a test coil during operation of the device may yet also be decorrelated to the principle of compensating background magnetic field component using a second sensor. By powering the test coil following a predetermined pattern, it may be possible to separate the test field from the first magnetic value, such that the testing may also become transparent to the detection of a wheel using a single magnetic field sensor. For instance, the test field may follow a predetermined pattern, with a predetermined frequency and/or a predetermined amplitude.
According to another embodiment (not represented). an additional set of magnetic field sensors may be provided. These additional third and fourth magnetic tield sensors may be used as redundant magnetic field sensors in addition to the first and second magnetic field sensors 18 and 20. The third and fourth magnetic field sensors may be located with respect to each other on the printed circuit board in a similar manner as the first and second magnetic field sensors 18 and 20.
The third and fourth magnetic field sensors 18, 20 may be arranged on the other side of the PCB 41 and at two opposite edges 41a and 41b of the (typically rectangular) printed circuit board 41.
Additional test coils may also be arranged with the third and fourth magnetic field sensors. The third magnetic field sensor and the fourth magnetic field sensor may be aligned along the same direction B along which the first and second magnetic field sensors 18, 20 are aligned but on the other side of the PCB.
To illustrate the operation of the processor, reference is made to Figures 7a and 7b showing an example of data obtained and processed by the processor 40 of a wheel detection device applied for detecting the passage of wheels of a train containing a coil creating a passing dc or low frequency magnetic field (anomaly). In Figure 7a, x1 counts and x2 counts are represented. The x1 counts amount to first magnetic values (preferably of at least one component of the field along one axis, for example the x axis) from the first magnetic field sensor 18, while the x2 counts amount to the second magnetic values (preferably of the at least same one component of the field, i.e. along the same axis) from the second magnetic field sensor 20. By counts are meant LSB (Least
Significant Bit) of the measured data from the sensors. A count is in that sense related to a value in
Tesla depending on sensor settings and scaling of data in the data transport. A count amounts approximatively to 300 pT. The plot of the x1 counts shows high peaks 71 occurring at a frequency Ta and high valleys 72, 73, 74 and 75 occurring at a frequency Tb. The peaks 71 are indicative of the passage of a coil generating an anomaly above the device, while each valley 72-75 represents the detection of a single wheel above the device. In the plot as shown, each pair of two valleys corresponds to the passage one bogie. It is noted that the maximum amplitude of the valleys varies due to variations in diameter and materials of the wheels, as well as due to variations in distances and height of passage. In addition, it is noted that an anomaly creating valleys rather than peaks would equally be compensated by a device according to the invention, such that the examples of Figures 7a and 7b should not be constructed as limitative for that aspect.
Figure 7b represents a plot of the difference between the x1 counts and the x2 counts, and thus of the difference between the first and the second magnetic field value which represents a magnetic value in which the magnetic influences affecting equally the first and the second sensors have been compensated. The background magnetic field component represents indeed a measurement error affecting the detection of the wheel. As can be seen in Figure 7b, the obtained waveform by subtracting the x1 counts and the x2 counts still contains peaks 81 and valleys 82-85, yet the relative amplitude of the peaks compared to the valleys has been greatly reduced.
Considering that for the purpose of detecting a wheel, the large valleys 72-75 in the x1 counts represent the signal to be detected, it is clear that the corresponding valleys 82-85 are more important than the remaining “noise” component in the final signal (x1-x2). The distance between the first and the second magnetic field sensors 18 and 20 determines the SNR (signal to noise ratio). The smaller the distance, the smaller the amplitude of the valleys 82-85 used for detecting a wheel and the smaller the amplitude of the peaks 81. The distance may then be chosen to optimize the reduction of the amplitude of the valleys (signal) versus the reduction of the amplitude of the noise (peaks). In practice, it has been seen that an optimized distance allows keeping 70% of the signal while keeping only 10% of the noise. As a side note, it is here noted that the term “noise” was used above in the context of signal treatment in line with the notion of SNR.
Figure 8 shows a scatter plot of the time values of Figure 7a of both the first and the second sensing unit. By extrapolation, two lines 91 and 92 may be extracted from that scatter plot.
Line 91 is oriented at 45 degrees and represents thus influences affecting in the same manner the first and the second sensor. Line 92 is oriented along another direction and illustrates the influence due to the passing of the wheel affecting differently the first and the second sensor. The scatter plot confirms thus that the second sensor may be used to identify a background magnetic field representing phenomena altering the magnetic field other than the wheel passing the device.
Whilst the principles of the invention have been set out above in connection with specific embodiments, it is understood that this description is merely made by way of example and not as a limitation of the scope of protection which is determined by the appended claims.
Claims (24)
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL2035850A NL2035850B1 (en) | 2023-09-21 | 2023-09-21 | Improved wheel detector device with background field compensation |
| PCT/EP2024/076658 WO2025062040A1 (en) | 2023-09-21 | 2024-09-23 | Improved wheel detector device with background field compensation |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL2035850A NL2035850B1 (en) | 2023-09-21 | 2023-09-21 | Improved wheel detector device with background field compensation |
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| Publication Number | Publication Date |
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| NL2035850B1 true NL2035850B1 (en) | 2025-03-28 |
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| Application Number | Title | Priority Date | Filing Date |
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| NL2035850A NL2035850B1 (en) | 2023-09-21 | 2023-09-21 | Improved wheel detector device with background field compensation |
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| NL (1) | NL2035850B1 (en) |
| WO (1) | WO2025062040A1 (en) |
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| DE1169491B (en) * | 1959-06-04 | 1964-05-06 | Tech Pour L Ind Nouvelle S A I | Axle count pulse generator in railway systems |
| US4524932A (en) | 1982-12-30 | 1985-06-25 | American Standard Inc. | Railroad car wheel detector using hall effect element |
| DE19959233A1 (en) * | 1999-12-08 | 2001-06-21 | Tiefenbach Gmbh | High-integrity inductive sensor detecting metal parts and e.g. revealing occupied rail track section, has additional testing coil enabling periodic proof testing of sensor coil |
| WO2002004800A1 (en) | 2000-07-11 | 2002-01-17 | Robert Bosch Gmbh | Method and device for error detection and diagnosis in a knock sensor |
| EP1362759A1 (en) | 2002-05-08 | 2003-11-19 | Siemens Aktiengesellschaft | Magnetic wheel sensor |
| US20070001059A1 (en) | 2005-07-01 | 2007-01-04 | Portec, Rail Products Ltd. | Railway wheel sensor |
| US20100235123A1 (en) | 2009-03-11 | 2010-09-16 | General Electric Company | System and method for correcting signal polarities and detection thresholds in a rail vehicle inspection system |
| WO2017045888A1 (en) | 2015-09-14 | 2017-03-23 | Thales Deutschland Gmbh | Method for determining the speed of a rail-bound vehicle |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102007023475B4 (en) * | 2007-05-15 | 2009-07-09 | Siemens Ag | wheel sensor |
| KR101898269B1 (en) | 2018-06-28 | 2018-09-12 | 마이크로맥스 영농조합법인 | ferment treat apparatus of organic wastes |
| NL2023451B1 (en) | 2019-07-05 | 2021-02-02 | Build Connected B V | Device for detecting a wheel on a rail track |
-
2023
- 2023-09-21 NL NL2035850A patent/NL2035850B1/en active
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|---|---|---|---|---|
| DE1016295B (en) * | 1952-11-14 | 1957-09-26 | Lorenz C Ag | Magnetic track device |
| DE1169491B (en) * | 1959-06-04 | 1964-05-06 | Tech Pour L Ind Nouvelle S A I | Axle count pulse generator in railway systems |
| US4524932A (en) | 1982-12-30 | 1985-06-25 | American Standard Inc. | Railroad car wheel detector using hall effect element |
| DE19959233A1 (en) * | 1999-12-08 | 2001-06-21 | Tiefenbach Gmbh | High-integrity inductive sensor detecting metal parts and e.g. revealing occupied rail track section, has additional testing coil enabling periodic proof testing of sensor coil |
| WO2002004800A1 (en) | 2000-07-11 | 2002-01-17 | Robert Bosch Gmbh | Method and device for error detection and diagnosis in a knock sensor |
| EP1362759A1 (en) | 2002-05-08 | 2003-11-19 | Siemens Aktiengesellschaft | Magnetic wheel sensor |
| US20070001059A1 (en) | 2005-07-01 | 2007-01-04 | Portec, Rail Products Ltd. | Railway wheel sensor |
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|---|---|
| WO2025062040A1 (en) | 2025-03-27 |
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