Patent Application
20240411044
The invention relates to an axle counting method for rail-mounted vehicles, having the following method steps: producing an electromagnetic transmission signal with a frequency, by a frequency source; transmitting the electromagnetic transmission signal by means of a transmission device of an electromagnetic rail contact element; detecting the electromagnetic transmission signal as a first reception signal and a second reception signal by means of two spaced-apart receiving units of the rail contact element; transmitting the reception signals; and producing an evaluation signal within a signal processing unit.
The invention further relates to an axle counting system.
By way of example, an axle counting method is known from EP 2 899 093 B1.
Axle counters are used to report track vacancy. Passing axles are detected by means of rail contact elements.
Axle counting devices and methods are used in railway signaling 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 route sections are vacant or occupied. The sensor elements used for this purpose generally comprise among other things a transmission device and a receiving device, which are mounted on opposite sides of a rail. The receiving devices generate a magnetic field, which is disturbed in the event of a passing axle. This disturbance is detected as a wheel pulse. The sensor elements form a so-called “rail contact element”.
Conventional axle counters with electromagnetic sensors are sensitive when the wheels are close to the sensor or pass the sensor very slowly. External disturbances, such as return traction currents or radiated fields from units in the operating frequency of the axle counter, can lead to incorrect axle evaluation. This is particularly a problem in train station areas where it is very likely that wheels will come to a stop near the axle counting sensor, or only pass it very slowly. This can result in disrupted axle counter sections with subsequent delays.
In principle, the problem could be solved by pattern recognition that can distinguish between wheels and return traction currents. However, such solutions would be very complex.
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 the axle counting points for each axle counting point position, independently of the selection at other axle counting point positions. The provided redundancy allows disturbances to be detected. For this purpose, two transmission devices are used for each counting point that transmit signals at different frequencies (28 kHz, 30 kHz). By using different frequencies, two independent channels are generated to prevent crosstalk. However, a redundant design of the axle counting points means high material outlay.
It is an object of the invention to propose an axle counting method with which external disturbances can be distinguished from wheel signals in a simple and cost-effective manner.
This object is achieved according to the invention by a method according to claim 1 and by an axle counting system according to claim 7.
In the axle counting method according to the invention, a single transmission unit is used to generate the transmission signal. According to the invention, the reception signals received by the two receiving units originate from the same transmission signal.
Using a single transmission unit ensures that possible external disturbances will always be reflected in the same way in both reception signals, and reduced occupancy of the frequencies in the band.
By detecting the same transmission signal using two spatially separated receiving units, two reception signals result. When a wheel travels between the transmission device and the two receiving units, the influence of the passing wheel on the transmission signal is time-shifted due to the spatial separation of the two receiving units—i.e., it is detected with a time-shift. External signals not belonging to the transmission signal are received equally by both receiving units, since both receivers receive signals on the same frequency. In this way, signals caused by external disturbances can be distinguished from wheel signals (i.e., signals caused by wheels passing the rail contact element). A redundant design of the rail contact elements can be dispensed with.
The signal processing unit processes the reception signals so that they can be interpreted/evaluated by an evaluation logic. The evaluation logic compares evaluation signals with a threshold value and interprets an exceeding of the threshold value as a passage of an axle.
The two adjacent receiving units, preferably coils, form a receiving device in the form of a double sensor.
Preferably, the evaluation signals of the two spatially separated receiving units are evaluated in a phase-inverted manner, which allows error detection for the transmission of the reception signals as well as error correction for disturbances. The phase-inverted evaluation can be realized by the type of evaluation (e.g., subtraction of the two reception signals), by signal processing or by phase inversion (i.e., a phase shift of) 180° before signal processing. The phase-inverted evaluation can detect an unwanted mutual influence between the two reception signals (crosstalk).
For this purpose, a particularly preferred variant of the method according to the invention provides that an inversion of the phase of one of the reception signals is generated before the transmission of the reception signals. This creates two channels independent of each other, even though the two reception signals have the same frequency. In this way, crosstalk can be reliably ascertained. This is, in particular, advantageous in critical sections in which the transmission cable can be easily damaged, which increases the risk of crosstalk. A “critical section” is to be understood as a section, or a portion of a section, over which the signal is to be transmitted, on which crosstalk is likely if no countermeasures are taken. Such sections are, in particular, connections between the frequency source and the transmission device, between the transmission device and the receiving units, and between the receiving units and the components for signal processing. In a preferred variant of the method according to the invention, the transmission of the electromagnetic reception signals (AC signals) therefore takes place over such a critical section.
Preferably, the phase inversion is carried out before the transmission of the reception signals by connecting the receiving units in opposite polarity. For this purpose, the receiving units are connected to the input of the signal processing unit with opposite polarities (cross-wire configuration).
In a special variant of the method, the phase inversion is removed after the transmission of the reception signals, in particular, by phase-synchronous rectification to the same transmission signal. Whether or not removal of the phase inversion is provided depends on how the signals are further processed, in particular, whether the reception signals are later subtracted from one another or added to one another. In the latter case, removal of the phase inversion is unnecessary. The rectification occurs regardless of which channel was used to transmit the reception signals.
Alternatively, a phase inversion can also be generated via software.
Preferably, phase-inverted synchronization signals are generated and used for the synchronous rectification, in particular, 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 reception signals. Without influences (i.e., without a passing wheel or external disturbances), a constant signal results from the synchronization process and after low-pass filtering.
If there is an influence, the field lines of the magnetic field generated by the transmission unit, which run through the receiving units are deflected, which can lead to a phase shift or even a signal inversion of the reception signal during the period of influence. The low-pass filtering “removes” the transmission frequency, which allows the different receivers, which are influenced differently by the wheel in spatial terms, to be evaluated. Due to the synchronization process and the low-pass filtering, a signal deviating from the constant signal is produced for each receiving unit during the respective periods of influence.
In the event of unwanted electromagnetic influence, both receiving units are usually influenced during the same period. In the event of a wheel influence due to a passing train, the receiving units are influenced with a time-shift. The rectification of the reception signals enables a subsequent differentiation between the two reception signals.
Preferably, a difference signal of the two synchronized reception signals is formed as an evaluation signal in the signal processing unit.
In the case of unwanted electromagnetic influence, a constant signal, in particular, a zero line results as the difference signal. In the event of a wheel influence due to a passing train, a non-vanishing difference signal results due to the time-shifted influence.
The difference signal is preferably generated using the rectified reception signals. Alternatively, the non-rectified signals could be used and then rectified.
If an inversion takes place before the transmission of the reception signals to the signal processing unit, the difference signal can be generated by adding the inverted reception signals, or by removing the inversion and then subtracting the no-longer-inverted reception signals.
If no inversion takes place before the transmission of the reception signals, the difference signal is generated by subtracting the two reception signals. In the latter variant, non-inverted reception signals are initially generated by connecting the receiving units with the same polarity; the non-inverted reception signals are transmitted to the signal processing unit for further processing.
The invention also relates to an axle counting system for carrying out a method described above, the axle counting system comprising:
According to the invention, the transmission device has a single transmission unit.
During operation, the rail contact element is attached to a rail of a track and comprises a transmitter generating an alternating electromagnetic field, and two receiving units that receive the alternating electromagnetic field. The evaluation circuit detects the change in the alternating electromagnetic field in the reception signals caused by a wheel rolling past on the rail by generating an evaluation signal from the two reception signals. The evaluation signal is compared with a threshold value, and if the threshold value is exceeded it is interpreted as an axle passage and is fed as a counting pulse to a track vacancy reporting device.
An evaluation logic can be provided to evaluate the evaluation signal.
A particularly preferred embodiment provides that the receiving units of the rail contact element are connected to the evaluation circuit with different polarity. This causes a phase inversion of one of the reception signals so that the two reception signals can be transmitted independently of each other to the signal processing unit.
A further preferred embodiment provides that a synchronization device is present for removing the specified phase shift of the reception signals, which is electrically connected between the receiving units and the signal processing unit. This allows a previously applied phase inversion to be reversed.
Preferably, the frequency source is configured to generate a synchronization signal and an inverted synchronization signal and is connected by signaling connection 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 reception signals.
Preferably, the signal evaluation device comprises a difference signal device. The difference signal device is used to eliminate external disturbances.
Furthermore, it is advantageous if the signal evaluation device comprises a comparator. The comparator compares an analog (optionally processed) reception signal to whether it falls below a fixed switching threshold and is used to detect when a wheel is exactly between the two receiving units, since this could be compensated for in the difference signal.
Preferably, the synchronization device comprises rectifiers.
Furthermore, it can be advantageous if low-pass filters are present between the synchronization device and the signal processing unit. The low-pass filters are used to eliminate higher frequencies (preferably >130 Hz) which definitely cannot be attributed to wheel influences.
Further advantages of the invention can be found in the description and the drawings. Likewise, according to the invention, the aforementioned features and those which are to be explained below can each be used individually or together in any desired combinations. The embodiments shown and described are not to be understood as an exhaustive list, but, rather, have an exemplary character for the description of the invention.
The transmission unit 2 is preferably arranged 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 each other along the longitudinal extension of the rail 3. In this way, the first reception signal RX1 received by the first receiving unit 4a is influenced by a passing wheel at a different time than that of the second reception signal RX2 received by the second receiving unit 4b.
In addition to the transmission signal TX, the frequency source 1 also generates synchronization signals TXs+, TXs− which are in phase or phase-inverted with respect 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 channels independent from each other, and includes, in particular, phase-synchronous rectification. For this purpose, the synchronization signals TXs+, TXs− are relayed as reference signals to synchronous rectifiers 5a, 5b. The rectifiers 5a, 5b form input rectifiers of the signal processing unit 10. The signal processing unit 10 further comprises a difference signal generation unit 8 by means of which a difference signal RXdiff is generated from the synchronized reception signals RX1b, RX2b. The difference signal RXdiff can be used to determine, independently of external disturbances, whether a wheel has passed the rail contact element 12.
In the example shown in
In the present example (but not absolutely necessary), in phase-synchronous rectification, the channel of the second reception signal RX2 is evaluated in antiphase to the channel of the first reception signal RX1. For this purpose, two synchronization signals TXs+, TXs− are first generated by the same frequency source 2, which is also used to generate the transmission signal, and these also have a phase shift of 180° to each other and are in phase respectively phase-inverted to the transmission signal TX. The phase inversion is therefore removed by the synchronization of the reception signals RX1, RX2 with the synchronization signals TXs+, TXs−.
In order to generate a difference signal RXdiff by means of the difference signal generation unit 8, the signal-processed analog evaluation signals RX1b, RX2b are subtracted from one another in the difference signal generation unit 8. The evaluation of the difference signal RXdiff is carried out in an evaluation logic 9.
In the following, the invention is described with reference to further exemplary embodiments of the axle counting system according to the invention and method variants. The same reference signs as in
When evaluating the analog evaluation signals RX1b, RX2b, in addition to generating the difference signal RXdiff, an activation detection is carried out by means of comparators 7a, 7b. For this purpose, one comparator 7a, 7b is used per channel, which performs a wheel detection for each reception signal (by generating activation signals RX1d, RX2d). The activation signals RX1d, RX2d and the difference signal RXdiff are evaluated in the evaluation logic 9.
The digital activation signals RX1d, RX2d, preferably generated by comparators, are used to monitor the sensor (transmission device and receiving units) at rest (activation detection). This additional information on the difference signal RXdiff is used, among other things, to detect a wheel parked in the region of the sensor in a region between the receiving units.
By subtracting the two evaluation signals, the difference signal RXdiff is generated, from which the influence by the passing wheel (signal region 13) is clearly recognizable, since this occurred with a time-shift for the two receiving units 4a, 4b. However, the influence due to the external disturbance (signal region 14), which occurred simultaneously for both receiving units 4a, 4b, is no longer recognizable in the difference signal. It is therefore a disturbance-corrected signal. The method according to the invention achieves a desensitization of the axle counting points to signals other than the transmission signal (disturbances signals).
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2022 201 840.0 | Feb 2022 | DE | national |
This continuation application claims priority to PCT/EP2023/054341 filed on Feb. 21, 2023, which has published as WO 2023/161239 A1 and also the German application number DE 10 2022 201 840.0 filed on Feb. 22, 2022, the entire contents of which are fully incorporated herein with these references.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2023/054341 | Feb 2023 | WO |
| Child | 18810441 | US |
