Method for calibrating a wheel sensor, corresponding wheel sensor, and railway installation with a wheel sensor of this kind

Abstract

A particularly flexible method for automatically calibrating a wheel sensor includes using the wheel sensor to determine that a calibration must be carried out. The wheel sensor determines a point in time suitable for carrying out the calibration and the calibration itself is carried out by the wheel sensor at the determined point in time. A wheel sensor for carrying out the method is also provided.

Claims

1. A method for calibrating a wheel sensor, the method comprising the following steps: using the wheel sensor to establish that a decentralized calibration procedure is to be performed; using the wheel sensor to provide a self-acting determination of a point in time being suitable for the calibration procedure to be performed with reference to a detection that a rail-borne vehicle has completely driven past the wheel sensor by taking into consideration a temporal sequence of detecting wheels of the rail-borne vehicle; and using the wheel sensor to automatically perform a self-calibration at the determined point in time.

2. The method according to claim 1, which further comprises carrying out the step of using the wheel sensor to detect that a rail-borne vehicle has completely driven past the wheel sensor by determining that the wheel sensor does not detect a further wheel within a predetermined time period or within a time period that may be determined by the wheel sensor.

3. The method according to claim 1, which further comprises using the wheel sensor to determine at least one of a velocity of the rail-borne vehicle or a change in a velocity of the rail-borne vehicle and taking at least one of the velocity or the change in a velocity into consideration when detecting that the rail-borne vehicle has completely driven past the wheel sensor.

4. The method according to claim 1, which further comprises carrying out the step of using the wheel sensor to establish that the calibration procedure is to be performed by taking into consideration a comparison of at least one measured value with at least one desired value.

5. The method according to claim 4, which further comprises forming a temporal mean value of the at least one measured value and comparing the temporal mean value of the at least one measured value with the at least one desired value.

6. The method according to claim 5, which further comprises forming the temporal mean value of the at least one measured value over a time period of one day or multiple days.

7. The method according to claim 4, which further comprises carrying out the step of using the wheel sensor to establish that the calibration procedure is to be performed by determining if the comparison of the at least one measured value with the at least one desired value results in a deviation lying in a predetermined value range.

8. The method according to claim 1, which further comprises carrying out the step of using the wheel sensor to establish that the calibration procedure is to be performed if a predetermined time period has elapsed since a last calibration procedure.

9. The method according to claim 1, which further comprises providing a wheel sensor having two sensor channels and performing the method in each of the two sensor channels independently of one another.

10. The method according to claim 1, which further comprises providing a wheel sensor having two sensor channels and performing the method across the two sensor channels.

11. A vehicle, comprising: a wheel sensor for establishing in a decentralized manner that a calibration procedure is to be performed; said wheel sensor determining in a self-acting manner a point in time being suitable for the calibration procedure to be performed with reference to a detection that a rail-borne vehicle has completely driven past said wheel sensor by taking into consideration a temporal sequence of detecting wheels of the rail-borne vehicle; and said wheel sensor automatically performing a self-calibration procedure at the determined point in time.

12. The vehicle according to claim 11, wherein said wheel sensor is part of a track clear signaling installation.

13. A railway installation or track clear signaling installation, comprising a vehicle according to claim 11 having at least one said wheel sensor.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) The invention is explained in detail below with reference to exemplary embodiments. In the drawings:

(2) FIG. 1 for explaining an exemplary embodiment of the method in accordance with the invention illustrates in a schematic drawing signals detected by a wheel sensor as a rail-borne vehicle is driving past and

(3) FIG. 2 for further explaining the exemplary embodiment of the method in accordance with the invention illustrates a flow diagram.

DESCRIPTION OF THE INVENTION

(4) FIG. 1 for explaining an exemplary embodiment of the method in accordance with the invention illustrates in a schematic drawing signals detected by a wheel sensor as a rail-borne vehicle is driving past. The figure illustrates signals S.sub.1 to S.sub.32 that are detected by a wheel sensor within the scope of a rail-borne vehicle driving past. In this case, the term “drive past” is to be understood such that the wheels of the rail-borne vehicle move through a detection region of the wheel sensor and are consequently detected by said wheel sensor. The corresponding wheel sensor may be used for different switching and controlling tasks within the scope of an automated railway operation and in particular may be a component of a track clear signaling installation. According to the illustration in FIG. 1, the signals S.sub.1 to S.sub.32 are detected by the wheel sensor at the points in time t.sub.1 to t.sub.32. Within the scope of the described exemplary embodiment, it is to be assumed by way of example that the rail-borne vehicle comprises eight vehicles each with four axles, wherein in each case two axles may be incorporated into one bogie. In this case, it is possible by way of example in each case for the signals S.sub.1 to S.sub.4, S.sub.5 to S.sub.8, S.sub.9 to S.sub.12, S.sub.13 to S.sub.16, S.sub.17 to S.sub.20, S.sub.21 to S.sub.24, S.sub.25 to S.sub.28 and S.sub.29 to S.sub.32 to relate to wheels of a corresponding vehicle or rather vehicle part, possibly in the form of a locomotive or a wagon of the rail-borne vehicle.

(5) It is apparent in FIG. 1 that the maximum temporal interval between the sequential signals S.sub.1 to S.sub.32 that is identified by Δt.sub.max occurs between the detection of the second and third axle of the first vehicle. Usually the maximum axle spacing within a rail-borne vehicle is approximately 20 m, with the result that from the respective velocity of the rail-borne vehicle and accordingly from an anticipated velocity of said rail-borne vehicle, it is possible to determine the maximum interval Δt.sub.max between the sequential signals S.sub.1 to S.sub.32. It is to be noted that the maximum temporal interval Δt.sub.max could naturally also occur in one of the other vehicles of the rail-borne vehicle in dependence upon a possible change in velocity of the rail-borne vehicle and in dependence upon the respective vehicle types.

(6) Insofar as the wheel sensor has now established that a self-calibration procedure is to be performed, said wheel sensor may determine a point in time that is suitable for the calibration procedure to be performed. In this case, the wheel sensor may derive the point in time at which a calibration procedure is to be triggered or rather the point in time at which to trigger a calibration procedure essentially from the sequence of states “not clear”/“clear” of one sensor system or in the case of a two channel dual sensor of both sensor systems. In the latter case, the decision regarding the point in time at which a calibration procedure is permissible and accordingly which point in time is suitable for a calibration procedure may be taken in each part-system or rather channel of the wheel sensor and accordingly of the axle counting point separately or from the result of both part-systems. It is essential in this case that further components, such as by way of example an axle counting computer in the internal system, are not involved in determining the point in time that is suitable for the calibration procedure to be performed. This is in particular advantageous in such cases in which as a consequence a change in the interface between the respective wheel sensor and the internal system is avoided.

(7) In the exemplary embodiment illustrated in FIG. 1, after the last signal S.sub.32 at the point in time t.sub.32 until at a point in time t.sub.33, the wheel sensor does not detect any further rail-borne vehicle driving past, in other words does not detect any further axle. Consequently, after the last axle of the rail-borne vehicle has been detected using the signal S.sub.32, the interval Δt.sub.e is considerably greater than the maximum temporal interval Δt.sub.max between the sequential signals S.sub.1 to S.sub.32. This is used by the wheel sensor as a criterion for detecting that the relevant rail-borne vehicle has completely driven past the wheel sensor and consequently the point in time t.sub.33 is determined as a point in time that is suitable for the calibration procedure to be performed. On account of the usual sequence of train intervals, it is hereby ensured that during the calibration procedure a rail-borne vehicle is not expected to drive past the wheel sensor and consequently the calibration procedure does not impair the detection or signaling of a subsequent rail-borne vehicle driving over said wheel sensor.

(8) Irrespective of this, the wheel sensor is however advantageously configured in such a manner that even during the calibration procedure said wheel sensor may correctly signal that wheels are driving over it or however at least detect that wheels are driving over it and may distribute an error message. Different embodiments are possible in this case depending up the design of the respective wheel sensor. Thus, even the shortest time periods during which a wheel is driving past, in other words at the highest occurring velocity, typically amount to approx. 3 ms. Insofar as the wheel sensor performs self-calibration more quickly or said wheel sensor is not impaired by means of a calibration procedure with regard to its detection ability, the performance of the calibration procedure does not have any influence on the reliability of the wheel sensor. If the situation occurs that the wheel sensor on account of or rather during its calibration procedure does not perform an error-free counting procedure, then this does not lead to a safety-critical situation in the event of an individual error at least in the case of a wheel sensor of an axle counting device even for the case that contrary to expectation a rail-borne vehicle is driving over the wheel sensor during the calibration procedure. Although as a consequence an axle counting error could occur that possibly results in an interruption of the train operation; insofar as it is possible to reliably exclude that the wheel sensor is “blind” with regard to a rail-borne vehicle having completely driven past it, a corresponding axle counting error is however not critical as far as safety aspects are concerned.

(9) According to the above explanations, with reference to the fact that it has been detected that a rail-borne vehicle has completely driven past the wheel sensor it is possible for the wheel sensor to determine the point in time that is suitable for the calibration procedure to be performed and subsequently for the wheel sensor to perform the self-calibration procedure at the determined point in time. As explained with reference to the illustration in FIG. 1, it is possible by taking into consideration a temporal sequence of detecting wheels of the rail-borne vehicle to detect that the rail-borne vehicle has completely driven past the wheel sensor. Specifically, it is possible for the wheel sensor to detect that the rail-borne vehicle has completely driven past the wheel sensor by way of example if the wheel sensor does not detect a further wheel within a predetermined time period or within a time period that may be determined by the wheel sensor Δt.sub.e. In this case, the time period may be predetermined to the extent that it is set to a constant value of by way of example 45 s.

(10) As an alternative thereto, the time period may also be determined by way of example by the wheel sensor itself. In this case, it is by way of example conceivable that the time period Δt.sub.e amounts to a multiple of the maximum interval Δt.sub.max detected by the wheel sensor between the sequential signals S.sub.1 to S.sub.32. The time period Δt.sub.e may thus be selected by way of example to be five times or ten times the maximum temporal interval Δt.sub.max or rather may be determined by the wheel sensor itself. Where appropriate, it is possible in this case by way of example to also take into consideration the braking capacity of the trains traveling on the respective stretch of rail, in order even in the case of the respective rail-borne vehicle braking in the region of the relevant wheel sensor to be able to reliably rule out that the rail-borne vehicle has braked heavily in the region of the wheel sensor and has possibly come to a standstill and consequently has not completely driven past the wheel sensor. Where appropriate, it is also possible in this case for the wheel sensor to determine the velocity of the rail-borne vehicle and/or a change in velocity of said rail-borne vehicle and for this to be taken into consideration when detecting that the rail-borne vehicle has completely driven past the wheel sensor.

(11) After it has been explained in particular in connection with FIG. 1 how the wheel sensor may determine a point in time that is suitable for the calibration procedure to be performed, the exemplary embodiment of the method in accordance with the invention is to be further explained below with reference to FIG. 2.

(12) FIG. 2 illustrates a flow diagram for further explaining the exemplary embodiment of the method in accordance with the invention.

(13) It is assumed within the scope of the algorithm described by way of example below, that a check is initially performed in a method step 10 as to whether a predetermined time period has elapsed since the last calibration procedure. In this case, the predetermined time period may be by way of example one month or also three months, in which case the wheel sensor would have been calibrated at a maximum monthly or rather at a maximum every three months. Insofar as the condition is fulfilled, in other words the predetermined time period has elapsed since the last calibration period the method moves on to step 20; failing this the method returns to the starting point so that by way of example a check is performed in turn at regular temporal intervals as to whether in the meantime the predetermined time period has elapsed since the last calibration procedure.

(14) In the method step 20, the wheel sensor performs a check as to whether it is necessary to perform a calibration procedure by taking into consideration a comparison of at least one measured value with at least a desired value. In the described exemplary embodiment, it is assumed in this case that in a method step 30 the wheel sensor forms a temporal mean value of a measured value in the form of a rectified or rather open-circuit voltage of the wheel sensor and this mean value is supplied in a method step 40 as an input variable to the check step 20. In an advantageous manner, in this case a temporal mean value is formed over a time period of one day or of multiple days in order to determine therefrom in particular effects that are dependent upon the time of day, such as by way of example temperature effects.

(15) The wheel sensor checks in method step 20 with reference to a comparison of the at least one measured value in the form of the mean value of the rectified voltage in the track-clear state with a desired value, possibly in the form of the value of the rectified voltage that is determined within the scope of the last calibration procedure, as to whether there is a deviation in a predetermined value range. In this case, a check is consequently performed to establish that the relevant deviation is not too large and not too small and the wheel sensor is consequently located in a “calibratable range”. Insofar as this is the case, the method moves onto the method step 50. Failing this, the method returns to the starting point since it is not necessary or rather not expedient to calibrate the wheel sensor by taking into consideration the measured value.

(16) After it has been established in the preceding steps that a calibration procedure is to be performed, the wheel sensor determines in the method step 50 a point in time that is suitable for the calibration procedure to be performed. This means that the wheel sensor checks whether a wheel of a rail-borne vehicle is covering said wheel sensor or whether it is to be expected that a wheel will accordingly cover said wheel sensor or rather drive over said wheel sensor. According to the explanations in connection with FIG. 1, this may occur by way of example by virtue of the fact that the wheel sensor detects that a rail-borne vehicle has completely driven past said wheel sensor and said wheel sensor determines the relevant point as a point in time that is suitable for the calibration procedure to be performed. Insofar as the wheel sensor has determined the respective point in time as being suitable for the self-calibration to be performed, the wheel sensor performs the self-calibration in the method step 60. Failing this, the wheel sensor repeats the check, in particular as the next rail-borne vehicle drives over said wheel sensor, as to whether or rather if a point in time that is suitable for the calibration procedure to be performed is present.

(17) After the wheel sensor has been calibrated in the method step 60, a time counter is reset or rather a time stamp is set in the method step 70. This information may subsequently be used by the wheel sensor during the next performance of the method step 10 in order to decide whether from the time point of view it is necessary to perform a calibration procedure.

(18) According to the above explanations in connection with the exemplary embodiment of the method in accordance with the invention, this method and also a wheel sensor that is configured so as to perform the method in particular comprise the advantage that the wheel sensor itself completely controls and performs the calibration procedure. This means in particular that the wheel sensor alone also determines a point in time that is suitable for the calibration procedure to be performed. By virtue of the corresponding automatic independent calibration of the wheel sensor, there is on the one hand the advantage that owing to the wheel sensor itself determining that a calibration procedure is necessary, predetermined fixed inspection periods are no longer required. Moreover, by virtue of the wheel sensor performing the calibration procedure independently, it is advantageously possible to also increase the availability of the wheel sensor and consequently to increase the availability of the railroad installation which said wheel sensor is part of. As a consequence of the fact that it is not necessary to transfer information from other components to the wheel sensor so as to perform the calibration procedure, the method may furthermore also be used advantageously for such situations or rather wheel sensors in which only a unidirectional interface is available between the wheel sensor and by way of example an axle counting computer, with the result that a corresponding transfer of information would not be possible or rather would make it necessary to change the interface by way of example to the internal system.