Axle counting method and axle counting system

Abstract

An axle counting method for rail-mounted vehicles having the following method steps: • producing an electromagnetic transmission signal (TX) with a frequency, by a frequency source (1), • transmitting the electromagnetic transmission signal by means of a transmission device (2) of an electromagnetic rail contact element, • detecting the electromagnetic transmission signal as first reception signal (R.X1) and second reception signal (RX2) by means of two spaced-apart receiving units (4a, 4b) of the rail contact element, • transmitting the reception signals (RX1, RX2), • producing an evaluation signal (RX1b-RX2b) within a signal processing unit (10), is characterised in that, to generate the transmission signal, a single transmission unit is used, and in that the reception signals received by the two receiving units originate from the same transmission signal.

Description

[0001] - 1 - 21.02.2023

[0002] Applicant:

[0003] GTS Germany GmbH

[0004] Thalesplatz 1

[0005] 71254 Ditzingen

[0006] Germany

[0007] Representative:

[0008] Kohler Schmid Möbus Patent Attorneys

[0009] partnership limited by shares

[0010] Gropiusplatz 10

[0011] 70563 Stuttgart

[0012] Germany

[0013] Axle counting method and axle counting system

[0014] Background of the invention

[0015] The invention relates to an axle counting method for rail-bound vehicles with the following method steps:

[0016] • Generating an electromagnetic transmission signal with a frequency by a frequency source,

[0017] • Emission of the electromagnetic transmission signal by means of a transmission device of an electromagnetic rail contact element, • Detection of the electromagnetic transmission signal as a first reception signal and second reception signal (by means of two spaced-apart reception units of the rail contact element,

[0018] • Transmission of the received signals, and

[0019] • Generation of an evaluation signal within a signal processing unit.

[0020] The invention further relates to an axle counting system.

[0021] GTS Deutschland GmbH SP13476PCT An axle counting method is known, for example, from EP 2 899 093 Bl.

[0022] Axle counters are used for track clearance detection.

[0023] Axes detected by rail contact elements.

[0024] Axle counting devices and methods are used in railway signaling technology to detect the number of passing axles of a train. The information thus obtained is processed by one of the evaluation devices to determine whether track sections are clear or occupied. The sensor elements used for this purpose generally comprise a transmitting device and a receiving device, which are mounted on opposite sides of a rail. The receiving devices generate a magnetic field that is disturbed when a passing axle is detected. This disturbance is detected as a wheel pulse. The sensor elements form a so-called "rail contact element."

[0025] Conventional axle counters with electromagnetic sensors are sensitive when the wheels are close to the sensor or pass it very slowly. External interference, such as traction return currents or radiated fields from power units at the axle counter's operating frequency, can lead to incorrect axle counting. This is particularly problematic in station areas, where it is very likely that wheels will stop near the axle counting sensor or pass it very slowly. This can result in faulty axle counting sections and subsequent delays.

[0026] In principle, the problem could be solved by pattern recognition that could distinguish between wheel and drive return currents. However, such solutions would be very complex.

[0027] EP 2 899 093 B1 discloses a method for operating an axle counting system using redundant axle counting points (rail contact element and evaluation electronics) and an individual selection of axle counting points for each axle counting point position, independent of the selection at other axle counting point positions. The provided redundancy allows faults to be detected. For this purpose, two transmitting devices are used for each counting point, which transmit signals at different frequencies (28 kHz, 30 kHz). Using different frequencies is intended to generate two independent channels to prevent crosstalk. However, a redundant design of the axle counting points requires high material costs.

[0028] Object of the invention

[0029] The object of the invention is to propose an axle counting method with which external disturbances from wheel signals can be distinguished in a simple and cost-effective manner.

[0030] Description of the invention

[0031] This object is achieved according to the invention by a method according to claim 1 and an axle counting system according to claim 7

[0032] In the axle counting method according to the invention, a single transmitting unit is used to generate the transmitted signal. According to the invention, the received signals received by the two receiving units originate from the same transmitted signal.

[0033] By using a single transmitter unit, possible external interference is always reflected in the same way on both received signals, as well as a reduced occupancy of the frequencies in the band.

[0034] Detecting the same transmission signal using two spatially separated receiving units results in two received signals. When a wheel passes between the transmitting device and the two receiving units, the influence of the passing wheel on the transmission signal is offset in time, i.e., detected with a time delay, due to the spatial separation of the two receiving units. External signals not related to the transmission signal, however, are received equally by both receiving units, as both receivers receive signals on the same frequency. In this way, signals caused by external interference can be distinguished from wheel signals (i.e., signals caused by passing wheels through the rail contact element). A redundant design of the rail contact elements is unnecessary. The signal processing unit processes the received signals so that they can be interpreted / evaluated by an evaluation logic.The evaluation logic compares evaluation signals with a threshold value and interprets exceeding the threshold value as an axis crossing.

[0035] The two adjacent receiving units, preferably coils, form a receiving device in the form of a double sensor.

[0036] Preferably, the evaluation signals from the two spatially separated receiving units are evaluated in phase-inverted fashion, which allows for error detection in the transmission of the received signals as well as error correction for interference. Phase-inverted evaluation can be implemented by the type of evaluation (e.g., subtraction of the two received signals), by signal processing, or by phase inversion (i.e., a phase shift of 180°) prior to signal processing. Phase-inverted evaluation can detect unwanted mutual influences between the two received signals (crosstalk).

[0037] For this purpose, a particularly preferred variant of the method according to the invention provides for the phase inversion of one of the received signals to be generated prior to transmission of the received signals. This creates two independent channels, even though the two received signals have the same frequency. In this way, crosstalk can be reliably detected. This is particularly advantageous on critical routes where the transmission cable can easily be damaged, increasing the risk of crosstalk. A "critical route" is understood to be a route or a section of a route over which the signal is to be transmitted, where crosstalk is likely to occur if no countermeasures are taken. Such routes particularly relate to connections between the frequency source and the transmitting device, between the transmitting device and the receiving units, and between the receiving units and the signal processing components.In a preferred variant of the method according to the invention, the transmission of the electromagnetic reception signals (AC signals) therefore takes place via such a critical path.

[0038] Preferably, phase inversion occurs before the transmission of the received signals by connecting the receiving units with opposite polarity. For this purpose, the receiving units are connected to the input of the signal processing unit with opposite polarity (cross-wire configuration).

[0039] In a special process variant, the phase inversion is canceled after the transmission of the received signals, in particular by phase-synchronous rectification to the same transmitted signal. Whether or not the phase inversion is canceled depends on how the signals are further processed, in particular whether the received signals are subsequently subtracted from one another or added to one another. In the latter case, no phase inversion cancellation is necessary. The rectification occurs regardless of the channel over which the received signals were transmitted.

[0040] Alternatively, phase inversion can also be generated using software.

[0041] Preferably, phase-inverted synchronization signals are generated and used for synchronous rectification, particularly square-wave signals phase-shifted by 180°. In phase-synchronous rectification, the phase positions of the synchronization signals are compared with the phase positions of the received signals. The synchronization process, followed by low-pass filtering, results in a constant signal without interference (i.e., without a passing wheel or external interference).

[0042] If interference occurs, the field lines of the magnetic field generated by the transmitting unit passing through the receiving units are deflected, which can lead to a phase shift or even signal inversion of the received signal during the interference period. Low-pass filtering "removes" the transmitted frequency, allowing the evaluation of the different receivers, each spatially influenced differently by the wheel. The synchronization process and low-pass filtering result in a signal for each receiving unit that deviates from the constant signal during the respective interference period.

[0043] In the event of unwanted electromagnetic interference, both receiving units are generally affected during the same period. In the event of wheel interference due to a passing train, the receiving units are affected with a time delay. Rectification of the received signals allows for subsequent calculation of the difference between the two received signals. Preferably, a differential signal of the two synchronized received signals is generated in the signal processing unit as the evaluation signal.

[0044] In the case of unwanted electromagnetic interference, the differential signal is a constant signal, specifically a zero line. In the case of wheel interference due to a passing train, the time-delayed interference results in a non-zero differential signal.

[0045] The differential signal is preferably generated using the rectified received signals. Alternatively, the non-rectified signals could also be used and subsequently rectified.

[0046] If an inversion takes place before the transmission of the received signals to the signal processing unit, the difference signal can be generated by adding the inverted received signals or by canceling the inversion and then subtracting the no longer inverted received signals.

[0047] If no inversion occurs before the transmission of the received signals, the difference signal is generated by subtracting the two received signals. In the latter variant, non-inverted received signals are initially generated by connecting the receiving units with the same polarity. The non-inverted received signals are then transmitted to the signal processing unit for further processing.

[0048] The invention also relates to an axle counting system for carrying out a method described above, the axle counting system comprising:

[0049] • an electromagnetic rail contact element with an electromagnetic transmitting device and two spaced-apart electromagnetic receiving units, a frequency source for generating a transmitting signal for the electromagnetic transmitting device, wherein the frequency source is electrically connected to the transmitting device of the rail contact element, an evaluation circuit for determining an axle passage with a signal processing unit for generating an evaluation signal from the two received signals.

[0050] According to the invention, the transmitting device has a single transmitting unit.

[0051] During operation, the rail contact element is attached to a rail of a track and comprises a transmitter that generates an alternating electromagnetic field and two receiver units that detect the alternating electromagnetic field. The evaluation circuit detects the change in the alternating electromagnetic field generated by a wheel rolling past on the rail in the receiver signals by generating an evaluation signal from the two received signals. The evaluation signal is compared with a threshold value. If the threshold value is exceeded, it is interpreted as an axle crossing and fed as a counting pulse to a track vacancy detection system.

[0052] An evaluation logic can be provided to evaluate the evaluation signal.

[0053] A particularly preferred embodiment provides that the receiving units of the rail contact element are connected to the evaluation circuit with different polarizations. This causes a phase inversion of one of the received signals, so that the two received signals can be transmitted independently of each other to the signal processing unit.

[0054] A further preferred embodiment provides for a synchronization device for canceling the predetermined phase shift of the received signals, which is electrically connected between the receiving units and the signal processing unit. This allows a previously performed phase inversion to be reversed.

[0055] Preferably, the frequency source is configured to generate a synchronization signal and an inverted synchronization signal and is signal-connected to the synchronization device. The phase inversion is reversed by comparing the phase position of the synchronization signals with the phase positions of the corresponding received signals.

[0056] The signal evaluation device preferably comprises a differential signal device. The differential signal device serves to eliminate external interference. Furthermore, it is advantageous if the signal evaluation device comprises a comparator. The comparator compares an analog (possibly processed) received signal with a value below a fixed switching threshold and serves to detect when a wheel is positioned exactly between the two receiving units, since this could be compensated for in the differential signal.

[0057] Preferably, the synchronization device comprises rectifiers.

[0058] It can also be advantageous to have low-pass filters between the synchronization device and the signal processing unit. These low-pass filters serve to eliminate higher frequencies (preferably above 130 Hz) that are definitely not attributable to wheel influences.

[0059] Further advantages of the invention will become apparent from the description and the drawings. Likewise, the above-mentioned and further-described features can be used individually or in combination in any desired manner. The embodiments shown and described are not intended to be exhaustive, but rather are exemplary in nature for describing the invention.

[0060] Detailed description of the invention and drawing

[0061] Fig. 1 shows a schematic representation of the components and the method steps of a simple embodiment of the axle counting system according to the invention.

[0062] Fig. 2 shows a schematic representation of the components and the method steps of a further embodiment of the axle counting system according to the invention with additional activation detection and low-pass filtering.

[0063] Fig. 3 shows a schematic representation of the components and the method steps of a particularly preferred embodiment of the axle counting system with phase inversion according to the invention.

[0064] Fig. 4 shows the interconnection of the receiving units from Fig. 3. Fig. 5 shows the signal processing and evaluation of received signals with wheel detection and external interference without phase inversion according to Figure 2.

[0065] Figure 1 shows a simple variant of the method according to the invention and the components of the axle counting system according to the invention. A frequency source 1 serves to generate a frequency for a transmitting device with a transmitting unit 2. The transmitting unit 2 is arranged on a rail 3 and transmits a transmitted signal TX. From the transmitting unit 2, the electromagnetic field of the transmitted signal TX propagates around the rail 3 and is received by two spatially separated receiving units 4a, 4b of a receiving device. The transmitting unit 2 and the receiving units 4a, 4b form a rail contact arrangement 12. The first receiving unit 4a receives the transmitted signal TX in the form of a first received signal RX1, and the second receiving unit 4b receives the transmitted signal TX in the form of a second received signal RX2. In the method according to the invention, the transmitting device 2 comprises only a single transmitting unit 2. The 1st receiving unit 4a therefore receives on the same frequency as the 2nd.Receiving unit 4b. This allows both receive signals to be synchronized with the same transmit signal.

[0066] The transmitting unit 2 is preferably located centrally between the receiving units 4a, 4b, and can preferably be arranged on the side of the rail 3 opposite the receiving units 4a, 4b. The two receiving units 4a, 4b are spatially separated from one another along the longitudinal extent of the rail 3. In this way, the first received signal RX1 received by the first receiving unit 4a is influenced by a passing wheel at a different time than the second received signal RX2 received by the second receiving unit 4b.

[0067] In addition to the transmission signal TX, the frequency source 1 also generates synchronization signals TXs+, TXs-, which are in phase or phase-inverted to the transmission signal TX. The synchronization signals are preferably square-wave signals. The signal processing of the two reception signals RX1, RX2 is carried out via two independent channels and, in particular, includes in-phase rectification. For this purpose, the synchronization signals TXS+, TXs- are passed as reference signals to synchronous rectifiers 5a, 5b. The rectifiers 5a, 5b form the input rectifiers of the signal processing unit 10. The signal processing unit 10 further comprises a differential signal generation unit 8, by means of which a differential signal RXdiff is generated from the synchronized reception signals RX1b, RX2b. Based on the differential signal RXdiff, it can be determined, regardless of external interference, whether a wheel has passed the rail contact element 12.

[0068] In the example shown in Figure 1, phase-inverted received signals RX1, RX2 are generated, i.e. received signals that have a phase shift of 180° relative to one another. For this purpose, the receiving units 4a, 4b are connected in opposite polarity. The corresponding wiring is shown in detail in Figure 4. While in the first channel the in-phase rectifier 5a is connected to the coil start (marked with a dot) of the coil serving as the first receiving unit 4a, in the second channel the in-phase rectifier 5b is connected to the coil end of the coil serving as the second receiving unit 4b. The coils of the two receiving devices 4a, 4b are therefore flowed through in different winding directions. This results in a phase shift of the second received signal of 180° compared to the received signal that would be obtained if the second receiving unit were connected with its coil start to the rectifier 5b.Since both receiving units 4a, 4b receive the same transmission signal, the two received signals also have a phase shift of 180° to each other.

[0069] In the present example (but not absolutely necessary), during in-phase rectification, the channel of the second received signal RX2 is evaluated in phase opposition to the channel of the first received signal RX1. To do this, two synchronization signals TXs+ and TXs- are first generated by the same frequency source 2 that also generates the transmitted signal. These synchronization signals also exhibit a phase shift of 180° from each other and are in phase or phase-inverted to the transmitted signal TX. The phase inversion is thus canceled by synchronizing the received signals RX1 and RX2 with the synchronization signals TXs+ and TXs-.

[0070] To generate a differential signal RXdiff using the differential signal generation unit 8, the signal-processed analog evaluation signals RX1b, RX2b are subtracted from each other in the differential signal generation unit 8. The evaluation of the differential signal RXdiff takes place in an evaluation logic 9.

[0071] The invention is described below with reference to further exemplary embodiments of the axle counting system according to the invention and method variants. The same reference numerals as in Figure 1 are used for identical parts.

[0072] Figure 2 shows a variant of the method according to the invention and the components of the axle counting system according to the invention, in which no phase inversion of the received signals RX1, RX2 occurs. Therefore, only a single synchronization signal TXs+ is generated for the rectification of the received signals RX1, RX2.

[0073] Figure 2 also shows a method variant with expanded signal processing and evaluation. In contrast to the variant shown in Figure 1, to generate the analog evaluation signals RX1b, RX2b, the received signals RX1, RX2 are not only rectified but also low-pass filtered after rectification. For this purpose, the axle counting device according to the invention comprises low-pass filters 6a, 6b. Therefore, after rectification, in this method variant, the analog evaluation signals RX1b, RX2b are not yet available, but rather intermediate signals RX1a, RX2a.

[0074] When evaluating the analog evaluation signals RXlb, RX2b, in addition to generating the difference signal RXdiff, activation detection is performed using comparators 7a, 7b. For this purpose, one comparator 7a, 7b is used per channel, which performs wheel detection for each received signal (by generating activation signals RXld, RX2d). The activation signals RXld, RX2d and the difference signal RXdiff are evaluated in the evaluation logic 9. Figure 3 shows a particularly preferred variant of the method according to the invention and the components of the axle counting system according to the invention, in which, in addition to the extended signal processing and the extended evaluation as in the variant shown in Fig. 2, a phase inversion of the second received signal RX2 also takes place, as in the variant shown in Fig. 1.

[0075] Figure 5 shows the signals at various stages of signal processing and evaluation in an axle counting system according to Figure 2. In the time period shown in Figure 5, an influence first occurred by a passing wheel (signal area 13) and then by an external disturbance (signal area 14). The influence on the received signals is particularly noticeable through a change in amplitude, which can be seen in Figure 5 from the change in the shape of the envelope of the received signals. The two received signals RX1, RX2 are influenced by the passing wheel with a time delay, while the external disturbance occurs simultaneously in both received signals RX1, RX2. After phase-synchronous rectification, intermediate signals RX1a, RX2a are produced. After low-pass filtering, analog evaluation signals RX1b, RX2b are produced, which correspond to the envelope of the intermediate signals. The influences are clearly recognizable as local minima.

[0076] The digital activation signals RXld, RX2d, preferably generated by comparators, are used to monitor the sensor (transmitter and receiver units) at rest (activation detection). This additional information to the difference signal RXdiff is used, among other things, to detect a wheel parked in the sensor's range between the receiver units.

[0077] By subtracting the two evaluation signals, the difference signal RXdiff is generated, from which the influence of the passing wheel (signal range 13) is clearly visible, since this occurred at different times for the two receiving units 4a, 4b. However, the influence due to the external interference (signal range 14), which occurred simultaneously for both receiving units 4a, 4b, is no longer recognizable in the difference signal. It is therefore an interference-corrected signal. The method according to the invention desensitizes the axle counting points to signals external to the transmission signal (interference signals).

[0078] 1 frequency source

[0079] 2 transmitting device

[0080] 3 rail

[0081] 4a first receiving unit

[0082] 4b second receiving unit

[0083] 5a, 5b Rectifier

[0084] 6a, 6b Low-pass filter

[0085] 7a, 7b Comparators

[0086] 8 Differential signal generation unit

[0087] 9 Evaluation logic

[0088] 10 Signal processing unit

[0089] 11 Evaluation circuit

[0090] 12 Rail contact arrangement

[0091] 13 Signal area influenced by a passing wheel

[0092] 14 Signal range affected by an external disturbance

[0093] RX1 first received signal

[0094] RX2 second receive signal

[0095] RXla first synchronized receive signal

[0096] RX2a second synchronized receive signal

[0097] RXlb first analog rectified receive signal

[0098] RX2b second analog rectified receive signal

[0099] RXld first digital activation signal

[0100] RX2d second digital activation signal

[0101] TXs+, TXs- synchronization signals

[0102] RXdiff difference signal (evaluation signal)

[0103] Literature list:

[0104] EP 2 899 093 Bl

Claims

Patent claims for axle counting methods for rail-bound vehicles comprising the following process steps: • Generating an electromagnetic transmit signal (TX) with a frequency by a frequency source (1), • Emitting the electromagnetic transmission signal by means of a transmitting device (2) of an electromagnetic rail contact element, • Detection of the electromagnetic transmission signal as the first received signal (RX1) and second received signal (RX2) by means of two spaced-apart receiving units (4a, 4b) of the rail contact element, • Transmission of received signals (RX1, RX2) , • Generation of an evaluation signal (RX1b, RX2b) within a signal processing unit (10), characterized in that a single transmitting unit is used to generate the transmit signal, and that the received signals received by the two receiving units originate from the same transmit signal. Method according to claim 1, characterized in that the received signals are evaluated in phase inversion. Method according to claim 2, characterized in that, prior to the transmission of the received signals (RX1, RX2), an inversion of the phase of one of the received signals (RX1, RX2) is generated.

4. Method according to claim 3, characterized in that the phase inversion is carried out before the transmission of the received signals (R.X1, RX2) by connecting the receiving units (4a, 4b) in opposite polarities.

5. Method according to one of the preceding claims, characterized in that the cancellation of the phase inversion after the transmission of the received signals (RX1, RX2) is carried out by phase-synchronous rectification to the same transmitted signal.

6. Method according to claim 4, characterized in that phase-inverted synchronization signals are generated and used for synchronous rectification, in particular rectangular signals phase-shifted by 180°.

7. Method according to one of claims 2 to 5 characterized in that a difference signal (AB) of the two synchronized received signals is formed as an evaluation signal in the signal processing unit (10).

8. Method according to one of the preceding claims, characterized in that a comparison with a fixed limit value takes place in the signal processing unit (10).

9. Axle counting system for carrying out a method according to one of the preceding claims, wherein the axle counting system comprises: • an electromagnetic rail contact element with an electromagnetic transmitting device (2) and two spaced-apart electromagnetic receiving units (4a, 4b), • a frequency source (1) for generating a transmit signal (TX) for the electromagnetic transmitting device (2), wherein the frequency source (1) is electrically connected to the transmitting device (2) of the rail contact element, • an evaluation circuit (11) for determining an axis crossing with a signal processing unit (10) for generating an evaluation signal from the two received signals (RX1, RX2) and characterized in that the transmitting device (2) has a single transmitting unit.

10. Axle counting system according to claim 9, characterized in that the receiving units (4a, 4b) of the rail contact element are connected with different polarization to the evaluation circuit (11).

11. Axle counting system according to one of claims 9 to 11, characterized in that a synchronization device (5a, 5b) for canceling the predetermined phase shift of the received signals (RX1, RX2) is provided, which is electrically connected between the receiving units (4a, 4b) and the signal processing unit (10).

12. Axle counting system according to claim 11, characterized in that the frequency source is set up to generate two phase-shifted synchronization signals (TXs+, TXs-) and is connected to the synchronization device (5a, 5b) via signal technology.

13. Axle counting system according to one of claims 9 to 12, characterized in that the signal evaluation device comprises a differential signal device (8).

14. Axle counting system according to any one of claims 9 to 12, characterized in that the signal evaluation device comprises a comparator (7a, 7b).

15. Axle counting system according to any one of claims 9 to 13, characterized in that the synchronization device comprises rectifiers (5a, 5b).

16. Axle counting system according to one of claims 9 to 14, characterized in that low-pass filters (6a, 6b) are provided between synchronization device (5a, 5b) and signal processing unit (10).

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