Axle detection system and electromagnetic induction sensor

Abstract

To implement an axle detection system with a simpler configuration. [Solution] The axle detection system 1 includes a sensor body 10 which incorporates a transmitting coil and a differentially connected first receiving coil and second receiving coil, in the order of the first receiving coil, transmitting coil and second receiving coil, and which is installed in a direction along the longitudinal direction of the rail, so that the differential output due to the differential connection changes as the wheel flange passes, and a control unit 20 which determines the passage of a railway vehicle running on the rail based on the change in signal level and phase indicated by the differential output.

Description

Technical Field

[0001] The present invention relates to an axle detection system and the like.

Background Art

[0002] As a technique for detecting the axles of railway vehicles, a technique using electromagnetic induction sensors is known (for example, Patent Document 1). Such an axle detection sensor arranges two sets of detectors each consisting of a transmission coil TX and a reception coil RX facing each other across a rail, with a fixed distance L along the longitudinal direction of the rail. The reception coils RXa and RXb of each detector are differentially connected in series. The passing direction of the train is determined from the difference in the timing when each of the two sets of detectors detects a wheel, and the passing speed of the train is determined from the detected time difference and the fixed distance L between the detectors.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above-described conventional technology, since it is necessary to arrange two sets of detectors with a fixed distance L, there are problems in terms of the labor and cost of the installation work for each. Further, when attempting to install at a predetermined position planned in advance, there may be cases where the fixed distance L cannot be ensured depending on the location. Therefore, a method of installing by changing the distance L can be considered, but if the distance L is changed, it is necessary to change the speed calculation formula. On the other hand, if the installation position is changed from the original planned installation position so as to ensure the distance L, the detection position changes, and thus when using the detection result for train speed control, it is necessary to change control parameters (for example, inspection speed, etc.). These various inconveniences could occur in the above-described conventional technology.

[0005] The problem that this invention aims to solve is to realize an axle detection system with a simpler configuration. [Means for solving the problem]

[0006] The first invention for solving the above problem is: A sensor body that incorporates a transmitting coil and differentially connected first and second receiving coils, in the order of the coil arrangement of the first receiving coil, the transmitting coil, and the second receiving coil, and that is installed in a direction along the longitudinal direction of the rail, such that the differential output due to the differential connection changes as the wheel flange passes, Control unit and Equipped with, The control unit includes a determination means (for example, the determination unit 26 in Figure 4) that determines the passage of a railway vehicle traveling on the rails based on the signal level and phase changes indicated by the differential output. This is an axle detection system.

[0007] Other inventions include, An electromagnetic induction sensor comprising a transmitting coil and differentially connected first and second receiving coils, with the coil arrangement being the first receiving coil, the transmitting coil, and the second receiving coil, and the coil arrangement being oriented along the longitudinal direction of the rail, wherein the differential output due to the differential connection changes as the wheel flange passes, Based on the signal level and phase changes indicated by the differential output, the passage of a railway vehicle traveling on the rails is determined. An electromagnetic induction sensor (for example, the sensor body 10 in Figure 1) may be constructed.

[0008] According to the first invention, the axle detection system can be realized with a simpler configuration. Specifically, a transmitting coil and differentially connected first and second receiving coils can be incorporated in the order of the coil arrangement (first receiving coil, transmitting coil, and second receiving coil), and installed in that order along the longitudinal direction of the rail. The differential output of the differentially connected first and second receiving coils is almost constant when no railway vehicle is passing, but when a vehicle is passing, its signal level and phase change due to the electromagnetic induction phenomenon caused by the proximity of the wheel flange, which is a metal object. Therefore, it is possible to determine the passage of a railway vehicle based on the change in the signal level and phase indicated by the differential output.

[0009] The second invention is, in the above invention, The determination means determines the direction of passage of the railway vehicle based on the change. This is an axle detection system.

[0010] According to the second invention, the signal level and phase changes shown by the differential output of the first and second receiving coils differ depending on which direction the railway vehicle approaches from, as these coils are arranged along the longitudinal direction of the rail. Based on these changes, it becomes possible to determine the direction in which the railway vehicle is passing.

[0011] The third invention is, in the above invention, The determination means determines the passing speed of the railway vehicle based on the change. This is an axle detection system.

[0012] According to the third invention, the time it takes for the signal level and phase indicated by the differential output of the first receiving coil and the second receiving coil to change differs depending on the time it takes for the railway vehicle to pass the sensor body. Based on this change, it becomes possible to determine the speed at which the railway vehicle is passing.

[0013] The fourth invention is, in the above invention, The determination means performs the determination based on the trajectory of plotted points based on the differential output in a predetermined coordinate system composed of coordinate axes corresponding to the signal level and phase, respectively. This is an axle detection system.

[0014] According to the fourth invention, the trajectory of the plotted points represents the time-series changes in signal level and phase indicated by the differential output of the first receiving coil and the second receiving coil as a railway vehicle passes. Therefore, it is possible to determine the passage of a railway vehicle based on this trajectory.

[0015] The fifth invention is, in the above invention, The determination means performs the determination based on the trajectory which is outside a predetermined threshold distance range from the reference point of the coordinate system determined based on the differential output when the railway vehicle is not passing. This is an axle detection system.

[0016] When a railway vehicle approaches, the differential output of the first and second receiving coils may become unstable as the output begins to change. Therefore, as in the fifth invention, it is possible to suppress misjudgments of the passing of a railway vehicle by basing the determination on a trajectory outside the range of a predetermined threshold distance from a reference point determined based on the differential output when the railway vehicle is not passing.

[0017] The sixth invention is, in the above invention, The determination means performs the determination based on the change in magnitude and orientation from a reference point in the coordinate system, which is determined based on the differential output when a railway vehicle is not passing, to the plotted point, in a predetermined coordinate system composed of coordinate axes corresponding to the signal level and phase, respectively. This is an axle detection system.

[0018] When the differential output of the first receiving coil and the second receiving coil when the railway vehicle is not passing is almost constant, the changes in magnitude and direction from the reference point corresponding to the non-passing state to the plotted point are relative changes based on the non-passing state of the signal level and phase indicated by the differential output. Therefore, as in the sixth invention, it is possible to determine the passage of the railway vehicle based on the changes in magnitude and direction from the reference point to the plotted point.

[0019] The seventh invention is in the above-mentioned invention, The determination means performs the determination by comparing the locus with a given reference locus. It is an axle detection system.

[0020] According to the seventh invention, for example, by predetermining the locus when the railway vehicle to be determined passes as a reference locus, it is possible to determine the passage of the railway vehicle to be determined.

[0021] The eighth invention is in the above-mentioned invention, The locus when the railway vehicle passes is composed of two partial loci that appear at point-symmetrical positions in time series. The determination means determines the passing direction of the railway vehicle based on which of the two partial loci appears first. It is an axle detection system.

[0022] According to the eighth invention, since the first receiving coil and the second receiving coil are differentially connected, the locus when the railway vehicle passes is composed of two partial loci that appear at point-symmetrical positions in time series. Also, depending on whether the railway vehicle approaches and passes from the first receiving coil or the second receiving coil, the changes in the signal level and phase indicated by the differential output are different. Therefore, it is possible to determine the passing direction of the railway vehicle based on which of the two partial loci appears first.

[0023] The ninth invention is in the above-mentioned invention, The determination means determines the type of railway vehicle due to the difference in wheel size based on the size of the locus. This is an axle detection system.

[0024] According to the ninth invention, since the degree of change in signal level and phase shown by the differential output of the first and second receiving coils differs depending on the size of the wheels of the railway vehicle, it is possible to determine the type of railway vehicle based on the size of the trajectory of the plotted points based on the differential output. [Brief explanation of the drawing]

[0025] [Figure 1] An example of an axle detection system installation. [Figure 2] Schematic diagram of the sensor body. [Figure 3] Schematic diagram of the sensor body. [Figure 4] Circuit diagram of the axle detection system. [Figure 5] An example of the relationship between wheel position and output value (X,Y). [Figure 6] An example of a trajectory plotted from the output values ​​(X,Y). [Figure 7] An example of output values ​​(X,Y) corresponding to the direction of passage. [Figure 8] An example of output values ​​(X,Y) corresponding to the direction of passage. [Figure 9] An example of a trajectory plotted from the output values ​​(X,Y). [Figure 10] Example of setting a threshold distance. [Figure 11] Diagram illustrating the reference trajectory in the first embodiment. [Figure 12] Flowchart of the determination process in the first embodiment. [Figure 13] An explanatory diagram illustrating the determination of the passage of a railway vehicle in the second embodiment. [Figure 14] An explanatory diagram illustrating the determination of the passage of a railway vehicle in the second embodiment. [Figure 15] An explanatory diagram illustrating the determination of the passage of a railway vehicle in the third embodiment. [Modes for carrying out the invention]

[0026] Preferred embodiments of the present invention will be described below with reference to the drawings. However, the applicable forms of the present invention are not limited to the following embodiments. Furthermore, in the drawings, the same elements are denoted by the same reference numerals.

[0027] [Overall structure] Figure 1 shows an example of the installation of the axle detection system in this embodiment. Figure 1 is a top view. As shown in Figure 1, the axle detection system 1 comprises a sensor body 10 and a control unit 20. The sensor body 10 is installed inside one of the two rails R, and the control unit 20 is installed, for example, in an equipment box near the track. The cable electrically connecting the sensor body 10 and the control unit 20 is routed under the rails R.

[0028] Figures 2 and 3 are schematic diagrams of the sensor body 10. Figure 2 is a top view, and Figure 3 is a side view. Figure 3 includes a reference image of the wheel 5 of a railway vehicle 3 running on the rail R. As shown in Figures 2 and 3, the sensor body 10 is fixed to the side of the rail R (more specifically, the side of the rail's belly). The sensor body 10 contains a transmitting coil TX1 and differentially connected first receiving coils RX1 and second receiving coils RX2, arranged (built-in) in the order of the first receiving coil RX1, transmitting coil TX1, and second receiving coil RX2. The distance L1 between the first receiving coil RX1 and the transmitting coil TX1, and the distance L2 between the transmitting coil TX1 and the second receiving coil RX2 are equal (L1=L2). In terms of the installation position relative to the rail R, the sensor body 10 is installed in a position below the wheel flange 7 of the railway vehicle 3 running on the rail R, with its coil arrangement oriented along the longitudinal direction of the rail.

[0029] The sensor body 10 is an electromagnetic induction sensor that utilizes the electromagnetic induction phenomenon that occurs in metal objects. As a metal wheel 5 traveling on the rail R passes, the wheel flange 7 passes in close proximity, causing a change in the differential output due to the differential connection of the first receiving coil RX1 and the second receiving coil RX2. This differential output is output to the control unit 20 via a cable, and the control unit 20 determines the passage of a railway vehicle traveling on the rail based on the change in signal level and phase indicated by the differential output of the sensor body 10. In this embodiment, since the first receiving coil RX1, the transmitting coil TX1, and the second receiving coil RX2 are arranged at equal intervals, the operating output is almost zero when the wheel flange 7 to be detected is not present (when the axle is not detected).

[0030] Figure 4 is a circuit diagram of the axle detection system 1. As shown in Figure 4, the control unit 20 of the axle detection system 1 has a transmitting / receiving unit 22, a signal processing unit 24, and a determination unit 26.

[0031] The transmitting / receiving unit 22 transmits an AC signal with frequency f0 generated by the oscillator as a transmission signal to the transmitting coil TX1 via a cable. The transmitting / receiving unit 22 also extracts a signal with frequency f0, which is the frequency of the transmission signal, as a received signal from the differential output of the first receiving coil RX1 and the second receiving coil RX2 received via the cable, using a Band Pass Filter (BPF).

[0032] The signal processing unit 24 performs quadrature detection of the transmitted signal and received signal transmitted and received by the transmitting / receiving unit 22, and generates output values ​​(X,Y) based on the level difference and phase difference between the transmitted signal and the received signal.

[0033] The determination unit 26 determines the passage of a railway vehicle 3 traveling on rail R based on the change in the output value (X,Y) generated by the signal processing unit 24. Specifically, it determines the passage of the railway vehicle 3 by detecting the passage of the wheels 5 of the railway vehicle 3. It also determines the direction and speed of passage at that time.

[0034] The determination of the passage of a railway vehicle 3 (direction of passage and speed of passage) by the determination unit 26 will be explained. Figure 5 is a diagram showing an example of the relationship between the position of the wheels 5 of the railway vehicle 3 and the output values ​​(X, Y). For the sake of explanation, the size of the wheels 5 is shown in a small size. In Figure 5, the horizontal direction is a common position along the longitudinal direction of the rail, the upper side shows the positional relationship between the center of the wheel 5 (corresponding to the position of the axle; hereinafter simply referred to as "the position of wheel 5") and the sensor body 10, and the lower side shows graphs of the X and Y values ​​for the position of wheel 5.

[0035] As shown in Figure 5, the output value (X,Y) changes when the relative position of the wheel 5 with respect to the sensor body 10 is within a predetermined range. The range of wheel 5 positions in which this output value (X,Y) changes is called the response distance.

[0036] Specifically, when the wheel 5 is outside the response distance range from the sensor body 10 (corresponding to non-passing), an alternating magnetic field is generated from the transmitting coil TX1, which transmits a transmission signal of frequency f0. The induced voltages of the first receiving coil RX1 and the second receiving coil RX2 due to this alternating magnetic field are approximately equal. In other words, the differential output of the first receiving coil RX1 and the second receiving coil RX2 is approximately constant, and the output value (X,Y) is approximately constant.

[0037] Next, consider the case where wheel 5 moves from left to right in Figure 5. As wheel 5 approaches the second receiving coil RX2, the magnetic field generated by transmitting coil TX1 is attracted to and biased by the metal wheel flange 7, causing the magnetic field passing through the second receiving coil RX2 to link with the second receiving coil RX2. In addition, due to the demagnetizing effect of eddy currents, the magnetic field passing through the second receiving coil RX2 decreases, resulting in a decrease in the induced voltage and a phase change in the second receiving coil RX2. Consequently, the differential output of the first receiving coil RX1 and the second receiving coil RX2, i.e., the signal level and phase of the received signal, changes, and the output value (X,Y), which is the result of quadrature detection of the transmitted and received signals, also changes. In the example in Figure 5, both the X and Y values ​​increase. Then, as wheel 5 is positioned approximately directly above the second receiving coil RX2 and passes approximately directly above it, the values ​​decrease. The X and Y values ​​reach their maximum values ​​when wheel 5 is positioned approximately directly above the second receiving coil RX2.

[0038] As wheel 5 moves further and is positioned approximately directly above the transmitting coil TX1, the bias in the magnetic field generated by the transmitting coil TX1 is almost eliminated, and the demagnetizing effect of the eddy currents on the first receiving coil RX1 and the second receiving coil RX2 becomes almost equal. As a result, the differential output of the first receiving coil RX1 and the second receiving coil RX2 becomes almost the same as when wheel 5 is outside the range of the response distance, and the output value (X,Y) becomes almost the same as when wheel 5 is outside the range of the response distance.

[0039] As wheel 5 moves further and approaches the first receiving coil RX1, the magnetic field generated by the transmitting coil TX1 is attracted to the wheel flange 7 and becomes biased, causing a decrease in the induced voltage and a phase change in the first receiving coil RX1. Consequently, along with the demagnetic field effect of eddy currents, the differential output of the first receiving coil RX1 and the second receiving coil RX2, i.e., the signal level and phase of the received signal, changes, and the output value (X,Y), which is the result of quadrature detection of the transmitted and received signals, also changes. This change is the opposite of the change when wheel 5 is approaching the second receiving coil RX2, and in the example in Figure 5, both the X and Y values ​​decrease. Then, when wheel 5 is positioned approximately directly above the first receiving coil RX1 and passes approximately directly above it, the values ​​increase. When wheel 5 is positioned approximately directly above the first receiving coil RX1, the X and Y values ​​reach their minimum values. Subsequently, as wheel 5 moves away from the first receiving coil RX1, the X and Y values ​​increase, and when wheel 5 is outside the range of the response distance, the differential output of the first receiving coil RX1 and the second receiving coil RX2 becomes almost constant, and the output value (X,Y) returns to the state when the vehicle is not passing through, with an almost constant value.

[0040] Figures 6 and 9 show the trajectories plotted on an XY coordinate system for the output values ​​(X,Y) shown in Figure 5. The output values ​​(X,Y) are the result of quadrature detection between the transmitted and received signals, and are based on the level difference and phase difference between the transmitted and received signals. Therefore, the X and Y axes that make up the XY coordinate system are the coordinate axes corresponding to the signal level and phase, respectively. In Figure 6, the trajectories are shown as smoothed curves, which are lines connecting each plotted point corresponding to the discrete output values ​​(X,Y).

[0041] As shown in Figures 6 and 9, the trajectory of the output value (X,Y) is roughly figure-eight shaped. The intersection of this figure-eight shape is the reference point P, which is the plotted point of the reference value (Xs,Ys), which is the output value (X,Y) when the railway vehicle 3 is not passing. The trajectory can be said to be composed of two partial trajectories, an upper and a lower loop shape, centered on this reference point P. These two partial trajectories appear in point-symmetric positions with respect to the reference point P. The top of the upper partial trajectory corresponds to the time when the wheel 5 is positioned roughly directly above the second receiving coil RX2, and the top of the lower partial trajectory corresponds to the time when the wheel 5 is positioned roughly directly above the first receiving coil RX1.

[0042] Incidentally, as shown in Figure 5, the way the output value (X,Y) changes differs depending on whether the railway vehicle 3 is approaching the first receiving coil RX1 or the second receiving coil RX2. For this reason, the order in which the trajectory appears when the railway vehicle 3 passes will differ depending on the direction in which the railway vehicle 3 passes.

[0043] Figure 7 shows an example of the time-series change in the output value (X,Y) when the railway vehicle 3 approaches and passes from the direction of the second receiving coil RX2. In Figure 7, the horizontal axis represents the position of the wheel 5, and the time-series changes in the X and Y values ​​are shown as a graph. In this case, as shown by the circled numbers in Figure 6, the upper partial trajectory where both the X and Y values ​​are positive appears first, followed by the lower partial trajectory where the X value is positive and the Y value is negative.

[0044] Figure 8 shows an example of the time-series change in the output value (X,Y) when the railway vehicle 3 approaches and passes from the direction of the first receiving coil RX1. In Figure 8, as in Figure 7, the horizontal axis represents the position of the wheel 5, and the time-series changes in the X and Y values ​​are shown as a graph. In this case, as shown by the circled numbers in Figure 9, the lower partial trajectory where the X value is positive and the Y value is negative appears first, followed by the upper partial trajectory where both the X and Y values ​​are positive.

[0045] Thus, the order in which the plotted points of the output value (X,Y) appear differs depending on whether the railway vehicle 3 (wheel 5) approaches the sensor body 10 from the first receiving coil RX1 or the second receiving coil RX2. In other words, the trajectory when the wheels 5 of the railway vehicle 3 pass is composed of two partial trajectories that appear in point-symmetric positions in time series. Therefore, the determination unit 26 determines the direction of passage of the railway vehicle 3 based on which of the two partial trajectories appears first. Specifically, if the upper partial trajectory appears first, the direction from the second receiving coil RX2 towards the first receiving coil RX1 is determined as the direction of passage. If the lower partial trajectory appears first, the direction from the first receiving coil RX1 towards the second receiving coil RX2 is determined as the direction of passage. In this way, it is possible to determine the direction of passage while the trajectory associated with the passage of the wheels 5 of the railway vehicle 3 is still appearing.

[0046] Furthermore, when the position of wheel 5 is outside the range of the response distance relative to the sensor body 10, the output value (X,Y) remains almost constant, and the plotted point in the XY coordinate system hardly changes from the reference point P. When the position of wheel 5 is within the range of the response distance, the output value (X,Y) changes, the plotted point in the XY coordinate system changes, and the trajectory appears. Therefore, the determination unit 26 determines the passing speed of the railway vehicle 3 by using the time it took for the output value (X,Y) to change, that is, the time it took for the figure-eight shaped trajectory to appear, as the time it took for the wheel 5 of the railway vehicle 3 to pass through the response distance.

[0047] Furthermore, if the size (diameter) of the wheels 5 of the railway vehicle 3 differs, the distance to each coil of the sensor body 10 will differ, resulting in different effects on the magnetic field generated by the transmitting coil TX1 and the eddy current effects on the first receiving coil RX1 and the second receiving coil RX2. Therefore, the magnitude of the output value (X,Y) when the railway vehicle 3 (wheel 5) passes will differ, and the magnitude of the trajectory of the plotted output value (X,Y) in the XY coordinate system will differ. Based on this, the determination unit 26 determines the type of railway vehicle 3 due to the difference in wheel size 5, based on the magnitude of the trajectory plotted for the output value (X,Y). For example, it distinguishes and determines the type of railway vehicle 3, such as a passenger vehicle or a maintenance vehicle with a smaller wheel diameter compared to a passenger vehicle.

[0048] In this way, the determination unit 26 determines the passage of a railway vehicle 3 running on the rail R based on the signal level and phase changes indicated by the differential output of the sensor body 10. At that time, it also determines the direction of passage of the railway vehicle 3, the speed at which it passes, and the type of railway vehicle 3 based on differences in wheel size.

[0049] Furthermore, as shown in Figure 10, the determination unit 26 may determine the passage of the railway vehicle 3 based on the trajectory outside the range of a predetermined threshold distance DH from the reference point P. In other words, a circular threshold distance range with a radius of the reference point P and the threshold distance DH is set, and the passage of the railway vehicle 3 is determined based on the trajectory outside this threshold distance range. The trajectory portion within the threshold distance range is masked as an exclusion target to prevent false determinations. Specifically, this is to exclude unstable values ​​when the differential output of the first receiving coil RX1 and the second receiving coil RX2 begins to change, such as when the railway vehicle 3 is approaching. In this method, the trajectory that is subject to determination when the railway vehicle 3 passes is a curved shape with a part of the center of the figure eight missing, and consists of two partial trajectories that appear at points symmetrical positions with respect to the reference point P. The following explanation will assume that this method is adopted. Of the two partial trajectories that appear when the railway vehicle 3 passes, the one that appears first is called the "first trajectory," and the one that appears later is called the "second trajectory."

[0050] The following describes three embodiments of the determination of the passage of a railway vehicle 3 by the determination unit 26.

[0051] [First Embodiment] In the first embodiment, the determination unit 26 determines the passage of a railway vehicle 3 based on the trajectory of plotted points based on differential output in a predetermined coordinate system composed of coordinate axes corresponding to signal level and phase, respectively. Specifically, the determination is made by comparing the trajectory with a given reference trajectory. The reference trajectory is the trajectory obtained when a railway vehicle 3 of the type to be determined to pass passes the sensor body 10. For example, the sensor body 10 can be installed on a test track, and time-series data of output values ​​(X,Y) can be obtained when a railway vehicle 3 of the type to be determined is run on a test track. Based on the acquired time-series data of output values ​​(X,Y), a reference trajectory can be generated.

[0052] Figure 11 is an explanatory diagram of the reference trajectory. As shown in Figure 11, first, a trajectory is generated by plotting the time-series data of the output values ​​(X,Y) when a railway vehicle 3 of the type to be judged passes through in chronological order. Next, from this trajectory, trajectories outside the threshold distance range, which is the range of the threshold distance DH centered on the reference point P, are extracted. The extracted trajectory consists of two sub-trajectories, an upper and a lower one, that appear at point-symmetrical positions with respect to the reference point P, so this pair of two sub-trajectories is designated as the reference trajectory.

[0053] Furthermore, the response distance for the type of railway vehicle 3 being judged is determined from the time-series data of the output values ​​(X,Y). This response distance is a distance that takes into account the threshold distance DH. That is, the response distance is the distance from the position of the wheel at the time one of the two sub-trajectories constituting the trajectory appears to the position of the wheel at the time the appearance of the other sub-trajectory ends.

[0054] Furthermore, a reference value (Xs,Ys) is determined based on the output value (X,Y) when the railway vehicle is not passing through. For example, the average of multiple output values ​​(X,Y) when the vehicle is not passing through is used as the reference value (Xs,Ys).

[0055] Figure 12 is a flowchart illustrating the flow of the determination process in the first embodiment. This process is performed by the determination unit 26 and determines one instance of the wheels 5 of the railway vehicle 3 of the type to be determined. The signal processing unit 24 outputs the results of quadrature detection of the transmission signal and reception signal to the sensor body 10 as needed, and the determination unit 26 samples the quadrature detection output from the signal processing unit 24 at a predetermined time interval (sampling interval) and acquires it as output values ​​(Xi, Yi).

[0056] As shown in Figure 12, in the determination process, each time an output value (Xi, Yi) is acquired, the determination unit 26 calculates the distance D from the reference value (Xs, Ys) in the XY coordinate system to the output value (Xi, Yi), and compares the calculated distance D with a predetermined threshold distance DH (see Figure 10) to determine whether it is outside the threshold distance range. The distance D is calculated by the following equation (1).

number

[0057] If the distance D to the output value (Xi, Yi) is greater than or equal to the threshold distance DH (Step S1: YES), the plotted point is outside the threshold distance range, so the plotting process is performed (Step S3). In the plotting process, the output value (Xi, Yi) is plotted in the XY coordinate system, and a trajectory (partial trajectory) is generated as a smoothed curve connecting the plotted points in chronological order. This plotting process is continued as long as the distance D to the output value (Xi, Yi) exceeds the threshold distance DH (Step S5: NO).

[0058] If the distance D to the output values ​​(Xi, Yi) becomes less than or equal to the threshold distance DH (Step S5: YES), it is determined that a partial trajectory has appeared, and a trajectory determination is performed (Step S9). For the trajectory determination, first, it is determined whether the appearing partial trajectory is the trajectory of the wheel 5 of the railway vehicle 3 of the type to be determined. Specifically, it is determined whether the size of the appearing partial trajectory matches the size of the partial trajectory of the wheel 5 of the railway vehicle 3 of the type to be determined. For example, this can be determined by whether the maximum distance Dm from the reference point P in the appearing partial trajectory (corresponding to the case when the position of the wheel 5 is located approximately directly above the first receiving coil RX1 or the second receiving coil RX2) is within a predetermined distance range.

[0059] If the trajectory is that of the wheel 5 of the railway vehicle 3 of the type being judged (Step S11: YES), then the direction of passage is determined (Step S13). That is, the resulting partial trajectory is compared with each of the two reference partial trajectories for the railway vehicle 3 of the type being judged (see Figure 11) to determine if they match. Matching can be determined, for example, by pattern matching using the trajectory as an image, based on the degree of match (also called similarity). The direction of passage is determined by which of the two partial trajectories the resulting partial trajectory matches.

[0060] Next, if the appearing partial trajectory is not the second trajectory (i.e., it is the first trajectory) (step S15: NO), the process returns to step S1, and the same process is performed for the next appearing partial trajectory (the second trajectory). If the appearing partial trajectory is the second trajectory (step S15: YES), the passing speed is determined (step S17). That is, the time required from the start of the appearance of the first trajectory to the end of the appearance of the second trajectory is determined, and the passing speed is calculated from that time and the response distance. After performing the above process, the determination process related to one pass of the wheels 5 of the railway vehicle 3 is completed.

[0061] [Second Example] In the second embodiment, the determination unit 26 determines whether the railway vehicle 3 has passed based on the change in magnitude and orientation from a reference point in the coordinate system, which is determined based on the differential output when the railway vehicle 3 is not passing, to a plotted point.

[0062] As shown in Figures 6 and 9, the trajectory of the railway vehicle 3 when it passes through consists of two partial trajectories that appear at point-symmetric positions centered on the reference point P, and the order in which these two partial trajectories appear differs depending on the direction of passage. Therefore, the direction of passage can be determined by judging which of the two trajectory parts appeared based on the change in magnitude and direction of the trajectory vector from the reference point P in the XY coordinate system to the plotted point.

[0063] Figures 13 and 14 are explanatory diagrams for determining the passage of the railway vehicle 3 in the second embodiment. In Figures 13 and 14, for explanatory purposes, the trajectories are shown after coordinate transformation to an XY coordinate system with reference point P as the origin. Figure 13 is an example of a trajectory when the direction of passage is from the second receiving coil RX2 to the first receiving coil RX1. In this case, the upper (first quadrant) subtrajectory appears first (first trajectory), followed by the lower (third quadrant) subtrajectory (second trajectory). Figure 14 is an example of a trajectory when the direction of passage is from the first receiving coil RX1 to the second receiving coil RX2. In this case, the lower (third quadrant) subtrajectory appears first (first trajectory), followed by the upper (first quadrant) subtrajectory (second trajectory).

[0064] As shown in Figures 13 and 14, in the XY coordinate system, a circle with radius DP centered at reference point P is defined, and a judgment threshold is set that intersects each of the two sub-trajectories. This judgment threshold intersects each of the two sub-trajectories in a total of four places. That is, it intersects the sub-trajectory appearing on the upper side (first quadrant) in two places, and the sub-trajectory appearing on the lower side (third quadrant) in two places.

[0065] The trajectory vectors pointing to each of these four intersection plot points are the same in magnitude, which is the radius of the judgment threshold, DP, but their directions are almost opposite. From this, the judgment unit 26 determines the timing at which the trajectory intersects the judgment threshold from the magnitude of the trajectory vector pointing from the reference point P to the plot point of output value (Xn, Yn), and determines which of the two trajectory vectors appeared from the direction of the trajectory vector at that timing. The magnitude of the trajectory vector is the distance Dn from the reference point P to the plot point of output value (Xn, Yn), and is calculated by the following equation (2). The direction of the trajectory vector is the angle θn with respect to the X axis, and is calculated by the following equation (3).

number

[0066] Specifically, the determination unit 26 samples the quadrature detection output of the transmitted and received signals from the signal processing unit 24 at predetermined time intervals (sampling intervals) and acquires it as an output value (Xn, Yn). Each time an output value (Xn, Yn) is acquired, the determination unit 26 calculates the distance Dn, which is the magnitude of the distance from the reference value (Xs, Ys) to the output value (Xn, Yn).

[0067] First, the distance Dn to the output value (Xn, Yn) is compared with the threshold distance DH (see Figure 10). If the distance exceeds this threshold distance DH, it is determined that the railway vehicle 3 (wheel 5) is approaching. Next, the distance Dn to the output value (Xn, Yn) is compared with the judgment threshold distance DP. If it is determined that the distance Dn has changed from being less than the judgment threshold distance DP to being greater than or equal to the judgment threshold distance DP (hereinafter referred to as "up"), it is determined that this is the moment when the judgment threshold was first crossed, and the angle θn, which is the direction from the reference value (Xs, Ys) towards the output value (Xn, Yn) at that time, is calculated.

[0068] Next, when it is determined that the distance Dn has changed from a state where it exceeds the judgment threshold distance DP to a state where it falls below the judgment threshold distance DP (hereinafter referred to as "down"), it is determined that this is the moment when it intersects with the second judgment threshold, and the angle θn from the reference value (Xs, Ys) to the output value (Xn, Yn) at that time is calculated.

[0069] Then, from the angle θn during these "up" and "down" movements, we determine whether the partial trajectory is in the upper (first quadrant) or the lower (third quadrant). That is, if the angle θn is 0° < θn < 90°, we determine that the partial trajectory is in the upper (first quadrant) (see Figure 13), and if it is 180° < θn < 270°, we determine that the partial trajectory is in the lower (third quadrant) (see Figure 14).

[0070] Next, similarly, the distance Dn to the output value (Xn, Yn) is compared with the judgment threshold distance DP to determine the timing of the intersection with the judgment threshold for the third and fourth times ("up" and "down"). Based on the angle θn from the reference value (Xs, Ys) to the output value (Xn, Yn) at that time, it is determined whether the partial trajectory is in the upper quadrant (first quadrant) or the lower quadrant (third quadrant). Then, if the determined partial trajectory is different from the previously determined partial trajectory, the previously determined direction of passage is confirmed.

[0071] Thus, in the second embodiment, the direction of the railway vehicle 3 can be determined from the change in the output values ​​(Xn, Yn) while the railway vehicle 3 is passing, without generating a trajectory by plotting the output values ​​(Xn, Yn).

[0072] [Third Embodiment] In the third embodiment, the determination unit 26 determines whether the railway vehicle 3 has passed based on the trajectory in progress. Specifically, it determines whether the railway vehicle 3 has passed by comparing the trajectory in progress with a reference trajectory, which is the trajectory that the railway vehicle 3 to be determined to pass would take.

[0073] Figure 15 is an explanatory diagram of the determination of the passage of a railway vehicle 3 in the third embodiment. As shown in the upper part of Figure 15, from the time-series data of the output values ​​(X,Y) when the wheels 5 of the railway vehicle 3 to be determined pass by, multiple images of intermediate trajectories from the start of appearance to the end of appearance (completion) are generated, and these intermediate trajectory images are associated with the direction of passage and the elapsed time t from the start of appearance of the trajectory to create a reference trajectory image. Such reference trajectory images, which are sets of intermediate trajectory images, are generated for each of the many passages. Then, a classifier, which is a trained AI model, is generated by training these reference trajectory images as training data.

[0074] As shown in the lower part of Figure 15, when the determination unit 26 determines that a railway vehicle 3 (wheel 5) is approaching because the distance Dn from the reference value (Xs,Ys) to the output value (X,Y) exceeds the threshold distance DH (see Figure 10), it starts plotting the output value (X,Y) in the XY coordinate system to generate a trajectory. Then, at predetermined time intervals, it inputs the trajectory images that have appeared up to that point, along with the elapsed time tn from the start of the plotting process, into the classifier, and determines the direction of passage of the railway vehicle 3 based on the determination result of whether the obtained image matches the reference image.

[0075] Thus, in the third embodiment, even while the railway vehicle 3 is passing, the direction of passage of the railway vehicle 3 can be determined based on the trajectory plotted from the output values ​​(X,Y) up to that point.

[0076] [Effects and Effects] According to this embodiment, the axle detection system 1 can be realized with a simpler configuration. Specifically, the transmitting coil TX1 and the differentially connected first receiving coil RX1 and second receiving coil RX2 are built into the system in the order of the coil arrangement (first receiving coil RX1, transmitting coil TX1, and second receiving coil RX2), and are installed in that order along the longitudinal direction of the rail, resulting in a simpler configuration.

[0077] The differential output of the differentially connected first receiving coil RX1 and second receiving coil RX2 is almost zero when the railway vehicle 3 is not passing, but when the railway vehicle 3 passes, its signal level and phase change due to the eddy currents generated in the metal wheel flange 7. Therefore, it is possible to determine the passage of the railway vehicle 3 based on the change in signal level and phase indicated by the differential output.

[0078] It should be noted that the applicable embodiments of the present invention are not limited to those described above, and can be modified as appropriate without departing from the spirit of the invention.

[0079] (A) Coil spacing In the above embodiment, the distance L1 between the first receiving coil RX1 and the transmitting coil TX1, and the distance L2 between the transmitting coil TX1 and the second receiving coil RX2 in the sensor body 10 were set to be equal (L1=L2), but they may be slightly different (L1≠L2). In this case, the differential output of the differentially connected first receiving coil RX1 and second receiving coil RX2 can detect a certain level of output even when the railway vehicle 3 is not passing. As a result, for example, if a coil is disconnected, the operating output will become zero, making it possible to detect an abnormality in the axle detection system 1. [Explanation of Symbols]

[0080] 1…Axle detection system 10... Sensor body TX1…Transmitter coil RX1…First receiving coil RX2…Second receiving coil 20... Control Unit 22... Transmitter / Receiver 24... Signal Processing Unit 26…Judgment section R... Rail 3…Railway vehicles 5...Wheel 7...Wheel flange

Claims

1. A sensor body that incorporates a transmitting coil and differentially connected first and second receiving coils, in the order of the coil arrangement of the first receiving coil, the transmitting coil, and the second receiving coil, and is installed in a direction along the longitudinal direction of the rail, such that the differential output due to the differential connection changes as the wheel flange passes, Control unit and Equipped with, The control unit includes a determination means for determining the passage of a railway vehicle traveling on the rails based on the signal level and phase changes indicated by the differential output. Axle detection system.

2. The determination means determines the direction of passage of the railway vehicle based on the change. The axle detection system according to claim 1.

3. The determination means determines the passing speed of the railway vehicle based on the change. The axle detection system according to claim 1.

4. The determination means performs the determination based on the trajectory of plotted points based on the differential output in a predetermined coordinate system composed of coordinate axes corresponding to the signal level and phase, respectively. The axle detection system according to any one of claims 1 to 3.

5. The determination means performs the determination based on the trajectory which is outside a predetermined threshold distance range from the reference point of the coordinate system determined based on the differential output when the railway vehicle is not passing. The axle detection system according to claim 4.

6. The determination means performs the determination based on the change in magnitude and orientation from a reference point in the coordinate system, which is determined based on the differential output when a railway vehicle is not passing, to the plotted point, in a predetermined coordinate system composed of coordinate axes corresponding to the signal level and phase, respectively. The axle detection system according to claim 1 or 2.

7. The determination means performs the determination by comparing the trajectory with a given reference trajectory. The axle detection system according to claim 4.

8. The trajectory of a passing railway vehicle consists of two partial trajectories that appear in point-symmetrical positions in chronological order. The determination means determines the direction of the railway vehicle's passage based on which of the two partial trajectories appears first. The axle detection system according to claim 4.

9. The determination means determines the type of railway vehicle based on the size of the trajectory, based on the difference in wheel size. The axle detection system according to claim 4.

10. An electromagnetic induction sensor comprising a transmitting coil and differentially connected first and second receiving coils, with the coil arrangement being the first receiving coil, the transmitting coil, and the second receiving coil, and the coil arrangement being oriented along the longitudinal direction of the rail, wherein the differential output due to the differential connection changes as the wheel flange passes, Based on the signal level and phase changes indicated by the differential output, the passage of a railway vehicle traveling on the rails is determined. Electromagnetic induction sensor.

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