METHOD FOR MONITORING A RAILWAY TRACK AND MONITORING UNIT FOR MONITORING A RAILWAY TRACK

Abstract

A method for monitoring a railway track may include: detecting a first monitoring signal by a distributed acoustic sensor at an initial position while a rail vehicle passes the initial position, the distributed acoustic sensor being arranged along the track; detecting a second monitoring signal by the distributed acoustic sensor at least one predefined position along the track while a rail vehicle passes the predefined position; and comparing the first and second monitoring signals with each other. The first monitoring signal includes features that each relate to one axle of the rail vehicle passing the initial position. The second monitoring signal includes features that each relate to one axle of the rail vehicle passing the predefined position. The comparing includes counting the features relating to axles of the respective passing rail vehicle for the first and second monitoring signals. Furthermore, a monitoring unit may monitor a railway track.

Claims

1. A method for monitoring a railway track, the method comprising: detecting a first monitoring signal by a distributed acoustic sensor at an initial position while a rail vehicle passes the initial position, wherein the distributed acoustic sensor is arranged along the track; detecting a second monitoring signal by the distributed acoustic sensor at least one predefined position along the track while a rail vehicle passes the predefined position; and comparing the first monitoring signal and the second monitoring signal with each other, wherein: the first monitoring signal comprises features that each relate to one axle of the rail vehicle passing the initial position and the second monitoring signal comprises features that each relate to one axle of the rail vehicle passing the predefined position; and comparing the first monitoring signal and the second monitoring signal with each other comprises counting the features relating to axles of the respective passing rail vehicle for the first monitoring signal and the second monitoring signal.

2. The method for monitoring a railway track according to claim 1, wherein comparing the first monitoring signal and the second monitoring signal with each other further comprises calculating a correlation between the first monitoring signal and the second monitoring signal.

3. The method for monitoring a railway track according to claim 1, wherein at the initial position the integrity of the rail vehicle passing the initial position is given.

4. The method for monitoring a railway track according to claim 1, wherein the integrity of the rail vehicle passing the initial position is confirmed by personnel of the respective rail vehicle or by an external device.

5. The method for monitoring a railway track according to claim 3, wherein the integrity of the rail vehicle passing the initial position is confirmed for the case that the first monitoring signal comprises the same number of features that each relate to one axle of the rail vehicle passing the initial position as a previous monitoring signal for which the integrity of the rail vehicle passing the position, where the previous monitoring signal is detected, is confirmed by personnel of the respective rail vehicle or by an external device.

6. The method for monitoring a railway track according to claim 1, wherein the distributed acoustic sensor comprises an optical fibre arranged along the track and the monitoring signals are backscattered signals of an input signal which is provided to the optical fibre.

7. The method for monitoring a railway track according to claim 1, wherein the position of a rail vehicle moving on the track is provided.

8. The method for monitoring a railway track according to claim 1, wherein a confirmation signal is provided if the first monitoring signal and the second monitoring signal relate to the same number of axles of the respective passing rail vehicle.

9. The method for monitoring a railway track according to claim 1, wherein a confirmation signal is provided if the first monitoring signal and the second monitoring signal have at least a predefined level of correlation.

10. The method for monitoring a railway track according to claim 1, wherein the at least one predefined position is determined by carrying out a correlation analysis for monitoring signals detected at a plurality of positions along the track during the passage of a rail vehicle with the first monitoring signal, wherein a position along the track is a predefined position if the monitoring signal at the respective position has at least a predefined correlation coefficient with the first monitoring signal.

11. The method for monitoring a railway track according to claim 1, wherein at the predefined position the rail has a defect or an irregularity.

12. The method for monitoring a railway track according to claim 1, wherein the second monitoring signal has an amplitude that is above a predefined threshold and monitoring signals detected during the passage of a rail vehicle at positions different from the at least one predefined position have an amplitude that is below the predefined threshold.

13. The method for monitoring a railway track according to claim 1, wherein the method is carried out for a plurality of predefined positions.

14. A monitoring unit for monitoring a railway track, the monitoring unit comprising: an input that is connected to a distributed acoustic sensor being arranged along the track; a detection unit that is configured to receive monitoring signals that are detected by the distributed acoustic sensor; and a comparison unit that is configured to compare a first monitoring signal detected by the distributed acoustic sensor at an initial position while a rail vehicle passes the initial position and a second monitoring signal detected by the distributed acoustic sensor at least one predefined position along the track while a rail vehicle passes the predefined position with each other, wherein: the first monitoring signal comprises features that each relate to one axle of the rail vehicle passing the initial position, and the second monitoring signal comprises features that each relate to one axle of the rail vehicle passing the predefined position; and comparing the first monitoring signal and the second monitoring signal with each other comprises counting the features relating to axles of the respective passing rail vehicle for the first monitoring signal and the second monitoring signal.

15. The monitoring unit according to claim 14, wherein the monitoring unit further comprises an output at which a confirmation signal is provided for the case that the first monitoring signal and the second monitoring signal relate to the same number of axles.

Description

[0041] With FIG. 1 an exemplary embodiment of the method for monitoring a railway track is described.

[0042] FIG. 2 shows monitoring signals for monitoring a railway track.

[0043] FIGS. 3 and 4 show exemplary embodiments of the monitoring unit for monitoring a railway track.

[0044] FIG. 5 shows an exemplary embodiment of the monitoring unit with a distributed acoustic sensor.

[0045] With FIG. 1 the steps of an exemplary embodiment of the method for monitoring a railway track 29 are described. In a first step S1 of the method a first monitoring signal M1 is detected by a distributed acoustic sensor 20 at an initial position 21 while a rail vehicle passes the initial position 21. The distributed acoustic sensor 20 is arranged along the track 29. The first monitoring signal M1 comprises features 23 that each relate to one axle of the rail vehicle passing the initial position 21. In a second step S2 of the method a second monitoring signal M2 is detected by the distributed acoustic sensor 20 at least one predefined position 22 along the track 29 while a rail vehicle passes the predefined position 22. The second monitoring signal M2 comprises features 23 that each relate to one axle of the rail vehicle passing the predefined position 22. In a third step S3 of the method the first monitoring signal M1 and the second monitoring signal M2 are compared with each other. Comparing the first monitoring signal M1 and the second monitoring signal M2 with each other comprises counting the features 23 relating to axles of the respective passing rail vehicle for the first monitoring signal M1 and the second monitoring signal M2. At the initial position 21 the integrity of the rail vehicle passing the initial position 21 is given. For example, the integrity of the rail vehicle passing the initial position 21 is confirmed by personnel of the respective rail vehicle or by an external device. Alternatively, the integrity of the rail vehicle passing the initial position 21 can be confirmed for the case that the first monitoring signal M1 comprises the same number of features 23 that each relate to one axle of the rail vehicle passing the initial position 21 as a previous monitoring signal for which the integrity of the rail vehicle passing the position, where the previous monitoring signal is detected, is confirmed by personnel of the respective rail vehicle or by an external device.

[0046] In an optional fourth step S4 a correlation is calculated between the first monitoring signal M1 and the second monitoring signal M2. The correlation can for example be a cross correlation. The calculation of the correlation between the first monitoring signal M1 and the second monitoring signal M2 is a further possibility to monitor the integrity of the rail vehicle at the predefined position 22.

[0047] In an optional fifth step S5 a confirmation signal is provided if the first monitoring signal M1 and the second monitoring signal M2 relate to the same number of axles of the respective passing rail vehicle. It is further possible that a confirmation signal is provided if the first monitoring signal M1 and the second monitoring signal M2 have at least a predefined level of correlation.

[0048] The at least one predefined position 22 is determined by carrying out a correlation analysis for monitoring signals detected at a plurality of positions along the track 29 during the passage of a rail vehicle with the first monitoring signal M1, wherein a position along the track 29 is a predefined position 22 if the monitoring signal at the respective position has at least a predefined correlation coefficient with the first monitoring signal M1. For example, at the predefined position 22 the rail has a defect or an irregularity. Thus, the second monitoring signal M2 can have an amplitude that is above a predefined threshold and monitoring signals detected during the passage of a rail vehicle at positions different from the at least one predefined position 22 have an amplitude that is below the predefined threshold.

[0049] The method can be carried out for a plurality of predefined positions 22.

[0050] In addition, the method enables to provide the position of a rail vehicle moving on the track 29.

[0051] In FIG. 2 monitoring signals for monitoring a railway track 29 are shown. On the x-axis the distance along the railway track 29 is plotted in arbitrary units. The y-axis the time is plotted in arbitrary units along the arrow, this means from top to bottom. The third axis is not shown in this two-dimensional representation, however, the lines shown in the diagram are monitoring signals detected by the distributed acoustic sensor 20 arranged along the railway track 29. The five lines represent the signal that is detected by the distributed acoustic sensor 20 along a distance of the railway track 29 over a certain period of time. The five lines only schematically represent the shape of the signal. Under normal conditions nearly no distinct features can be discriminated in the monitoring signals. It can only be discriminated that the amplitude of the monitoring signals is increased at the positions where a rail vehicle moves for the time where the rail vehicle moves at these positions. This means, for the white areas in the diagram the amplitude of the monitoring signals is not increased. Between the five lines the amplitude of the monitoring signals is increased as well. Thus, the movement of a rail vehicle is represented by an area of increased amplitude of the monitoring signals in this diagram.

[0052] The diagram in FIG. 2 further shows an initial position 21 and three predefined positions 22. For these four positions the monitoring signals have pronounced features 23. The initial position 21 is the position that the rail vehicle passes at first out of these four positions. At the initial position 21 the rail can have an irregularity or any other feature that leads to localized vibrations in the moment when a wheel of a rail vehicle passes the initial position 21. At the initial position 21 the first monitoring signal M1 is detected. The first monitoring signal M1 comprises five features 23 that can be distinguished from each other. Each of the five features 23 relates to one axle of the rail vehicle passing the initial position 21. Thus, by counting the features 23 in the first monitoring signal M1 the number of axles of the rail vehicle passing the initial position 21 can be determined. At the initial position 21 the integrity of the rail vehicle is given.

[0053] After passing the initial position 21 the moving rail vehicle passes the three predefined positions 22. Also at the predefined positions 22 the rail can have an irregularity or any other feature that leads to localized vibrations in the moment when a wheel of a rail vehicle passes the respective predefined position 22. At the predefined positions 22 second monitoring signals M2 are detected. Each second monitoring signal M2 comprises five features 23 that can be distinguished from each other. Each of the five features 23 relates to one axle of the rail vehicle passing the respective predefined position 22. Thus, by counting the features 23 in the second monitoring signal M2 the number of axles of the rail vehicle passing the respective predefined position 22 can be determined. Alternatively, the space between two passing axles can be regarded as a feature 23. In this way, the number of axles of the rail vehicle passing the respective predefined position 22 can be determined as well.

[0054] In the example of FIG. 2 the rail vehicle has the same number of axles at the initial position 21 and the three predefined positions 22. Therefore, for the three predefined positions 22 the integrity of the rail vehicle is confirmed.

[0055] FIG. 3 shows an exemplary embodiment of the monitoring unit 24 for monitoring a railway track 29. The monitoring unit 24 comprises an input 25 that is connected to a distributed acoustic sensor 20 being arranged along the track 29. The monitoring unit 24 further comprises a detection unit 26 that is configured to receive monitoring signals that are detected by the distributed acoustic sensor 20. The detection unit 26 is connected to the input 25. The monitoring unit 24 further comprises a comparison unit 27 that is configured to compare the first monitoring signal M1 and the second monitoring signal M2 with each other. The comparison unit 27 is connected to the detection unit 26. The monitoring unit 24 further comprises an output 28 at which a confirmation signal is provided for the case that the first monitoring signal M1 and the second monitoring signal M2 relate to the same number of axles. The comparison unit 27 is connected to the output 28.

[0056] FIG. 4 shows another exemplary embodiment of the monitoring unit 24. The only difference to the setup shown in FIG. 3 is that the monitoring unit 24 comprises the distributed acoustic sensor 20 or at least a part of the distributed acoustic sensor 20.

[0057] FIG. 5 shows an exemplary embodiment of the monitoring unit 24 with the distributed acoustic sensor 20. The monitoring unit 24 is connected to the distributed acoustic sensor 20. The distributed acoustic sensor 20 comprises an optical fibre 30 that is arranged along the track 29. Therefore, the monitoring signals are backscattered signals of an input signal which is provided to the optical fibre 30.

REFERENCE NUMERALS

[0058] 20: distributed acoustic sensor [0059] 21: initial position [0060] 22: predefined position [0061] 23: feature [0062] 24: monitoring unit [0063] 25: input [0064] 26: detection unit [0065] 27: comparison unit [0066] 28: output [0067] 29: railway track [0068] 30: optical fibre [0069] M1: first monitoring signal [0070] M2: second monitoring signal [0071] S1-S5: steps