Speed ​​detection device, speed detection system, and speed detection method

Abstract

The present invention enables the accurate measurement of travel speed even in a travel area where the measurement accuracy of a CW millimeter wave speed sensor is reduced, such as on a pit line in a rail yard or a bridge.　Provided is a speed detection device including a speed sensor and a sensor selection unit, wherein the mode of the speed sensor can be switched between a continuous wave (CW) system and a frequency modulation continuous wave (FMCW) system, and the sensor selection unit selects the FMCW system of the speed sensor at a predetermined speed or less and selects the CW system in the range other than these speeds.　If necessary, a plurality of speed detection devices are installed in the vehicle formation, and an SNR determination unit is provided for each device. When the detection accuracy of one speed detection device decreases, the mode of the other speed detection device is changed for a given time period to thereby stably and accurately acquire the travel speed of the vehicle.

Description

[Technical Field]

[0001] The present invention relates to a speed detection device, a speed detection system, and a speed detection method. [Background technology]

[0002] Traditionally, trains received location information from ground sensors installed between a pair of rails, and calculated their position by sequentially adding the amount of movement obtained from the rotation speed of the wheels to this location information. However, the speed generator used to measure the rotation speed of the wheels becomes difficult to use accurately when slippage or sliding occurs, where the rails and wheels are not in a state of adhesion.

[0003] For this reason, sensors have been developed to detect ground speed non-contactually using millimeter-wave radio waves under the train floor. For example, Patent Document 1 discloses the following speed detection device. "The speed measuring device 1 is installed under the vehicle floor and has a transmitting function that irradiates electromagnetic waves (irradiated waves) onto the rails 7 (more broadly, the track including the rails 7), and a receiving function that acquires electromagnetic waves (reflected waves) that return after hitting the rails 7. The transmitting and receiving functions may be implemented by separate antennas, or by a single antenna that has both transmitting and receiving functions." Furthermore, the speed measuring device 1 has a speed calculation function that inputs the reflected wave acquired by the above-mentioned receiving function into a calculation unit, and the calculation unit calculates the train's speed signal based on the frequency of the irradiated wave and the frequency of the reflected wave. More specifically, the speed calculation function of the speed measuring device 1 utilizes the fact that when a train is running, the electromagnetic waves irradiated onto the rail 7 (irradiated wave) and the electromagnetic waves reflected by the rail 7 (reflected wave) have different frequencies due to the Doppler effect, and calculates the speed signal based on this frequency difference. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-18205 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The speed measuring device disclosed in Patent Document 1 employs a millimeter-wave radar called the CW (Continuous Wave) method, which emits radio waves at a constant frequency. However, in the low-speed range, even with a speed generator or a CW-type millimeter-wave radar, it was difficult to achieve accurate speed detection unless the sampling time was set to a long duration. In particular, the CW-type millimeter-wave radar illuminates not only the rail itself but also the track bed, and detects speed including the reflected waves from the track bed. For this reason, there were challenges in speed detection accuracy in areas where the radar reflection conditions of the road surface differ, such as pit lines, bridge sections, and puddles. Therefore, the present invention aims to provide a technology that enables accurate speed detection regardless of the radar reflection conditions of the road surface, from low speed ranges to high speed ranges. [Means for solving the problem]

[0006] To solve the above problems, one representative speed detection device of the present invention is a speed detection device equipped with a speed sensor and a sensor selection unit, The aforementioned speed sensor is capable of speed detection using the CW (Continuous Wave) method and the FMCW (Frequency Modulation Continuous Wave) method. The sensor selection unit selects an FMCW speed sensor for speeds below a certain speed range, and a CW speed sensor for all other speed ranges. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a technology that enables accurate speed detection from low speed ranges to high speed ranges, regardless of the radar reflection conditions of the road surface. Problems, configurations, and effects other than those described above will be clarified by the description in the following embodiments for carrying out the invention.

Brief Description of the Drawings

[0008] [Figure 1] FIG. 1 is a diagram for explaining an example of mounting a speed detection device on a train. [Figure 2] FIG. 2 is a diagram for explaining the positional relationship between a millimeter-wave speed sensor and a road surface. [Figure 3] FIG. 3 is a diagram for explaining the positional relationship between a millimeter-wave speed sensor and a road surface. [Figure 4] FIG. 4 is a diagram for explaining the processing of a millimeter-wave speed sensor in the first embodiment. [Figure 5] FIG. 5 is a diagram for explaining the processing when the millimeter-wave speed sensor described in FIG. 4 is used in the CW mode. [Figure 6] FIG. 6 is a diagram for explaining an example of switching the sensor mode to be applied according to the running speed of a train. [Figure 7] FIG. 7 is a diagram for explaining an example of installation of a speed detection device in the second embodiment. [Figure 8] FIG. 8 is a flowchart showing the mode switching logic of the first embodiment. [Figure 9] FIG. 9 is a diagram for explaining the situation where a train consisting of a four-car formation approaches a section with a bridge or a puddle. [Figure 10] FIG. 10 is a table for explaining three conditions in the second embodiment. [Figure 11] FIG. 11 is a diagram for explaining the situation where a train consisting of a five-car formation equipped with three speed detection devices approaches a section with a bridge or a puddle. ]>

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited by this embodiment. Also, in the description of the drawings, the same parts are denoted by the same reference numerals. When there are a plurality of components having the same or similar functions, they may be described with the same reference numeral and different subscripts. Also, when it is not necessary to distinguish these plurality of components, the description may be made with the omission of subscripts. In addition, terms such as "first", "second", "third", etc. may be used in the present disclosure to describe various elements or components, but it will be understood that these elements or components should not be limited by these terms. These terms are only used to distinguish one element or component from another. Therefore, the first element or component discussed below can also be called the second element or component without departing from the teachings of the inventive concept. The positions, sizes, shapes, ranges, etc. of the respective components shown in the drawings may not represent the actual positions, sizes, shapes, ranges, etc. in order to facilitate the understanding of the invention. For this reason, the present invention is not necessarily limited to the positions, sizes, shapes, ranges, etc. disclosed in the drawings.

[0010] <CW method and FMCW method> First, the method of the millimeter-wave sensor used in the present disclosure will be described. The millimeter-wave sensor includes a CW method that irradiates millimeter waves of a certain frequency and detects the speed from the change in the frequency (Doppler effect) between the irradiated wave and the reflected wave, and an FMCW method that is a method of varying the frequency of the radiated radio wave within a certain frequency band.

[0011] The CW method detects the speed of the millimeter-wave irradiation target from the Doppler effect between the irradiated wave and the reflected wave, but it cannot calculate the distance from the sensor to the irradiation target. For this reason, in the CW method, the reflected wave from the rail and the reflected wave from the roadbed cannot be distinguished, and when the environment of the roadbed or the road surface changes, the speed detection accuracy may decrease.

[0012] On the other hand, the FMCW method emits millimeter waves whose frequency changes at a constant rate, and calculates the distance from the sensor to the object from the frequency deviation caused by the time difference between the emitted wave and the reflected wave. Therefore, it becomes possible to separate the signals from multiple objects based on distance information, and to analyze the primary reflected wave from the signal identified as a rail. Thus, it becomes possible to accurately calculate the velocity of the object. However, in the FMCW method, since the measurement of velocity is based on the change in distance information, that is, the change in phase with respect to the frequency deviation mentioned above, the wavelength of the emitted millimeter wave is λ, and the time interval of the repeatedly emitted band B signal is T. c In that case, the following equation (1) shows v max This represents the upper limit of the measurement speed. v max <λ / 4T c ··········(1) In other words, if λ is 4 mm and Tc is 40 μs, then v max This corresponds to approximately 90 km / h. Furthermore, the FMCW method has a greater computational load for calculations compared to the CW method, making it unsuitable for measurements at high speeds.

[0013] On the other hand, high-speed rail operates at a wide speed range, from 0 km / h to 400 km / h. Therefore, there was a need for a speed detection method that could accurately detect speed under various road surface conditions within this speed range.

[0014] <First Embodiment> First, with reference to Figure 1, we will explain an example of a speed detection device mounted on a train. In Figure 1, train 100 is a vehicle intended to operate on tracks under various surface conditions, both at and outside of stations. Generally, a train is composed of multiple coupled cars, but for the sake of simplicity, Figure 1 only shows the configuration of the cars that make up the train (the leading car). Furthermore, while Figure 1 shows an example where the train position recognition system for measuring the vehicle's speed is mounted on the lead vehicle, in the train position recognition system according to the present invention, the speed measuring device may be mounted on other vehicles. As shown in Figure 1, the train position recognition system 102 is mounted on a train 100 running on rails 101, and the train position recognition system consists of a speed detection device 103 and an on-board control device 104. Furthermore, the speed detection device 103 includes a millimeter-wave speed sensor 106 and a sensor selection unit 107. Furthermore, the on-board control device can acquire the position at any point using a transponder (not shown) installed on the ground, and calculate the distance traveled from that point using the distance calculated from the speed information acquired from the speed detection device.

[0015] (On regular routes) Next, with reference to Figure 2, the positional relationship between the millimeter-wave speed sensor and the track bed when the train 100 is located on a normal track will be explained. Figure 2 is a diagram illustrating the positional relationship between the millimeter-wave speed sensor 106, the rail 101, and the track bed when the rail 101 is installed at approximately the same height as the track bed 220. The millimeter-wave speed sensor 106 is fixed inside the housing 205 and includes a lens 207 that controls the irradiation range of the electromagnetic waves and a transparent window 208 for irradiating the electromagnetic waves of the millimeter-wave sensor to the outside of the speed measuring device. It is installed on the underside of the vehicle so that the rail 101 is included in the irradiation range 214 of the electromagnetic waves irradiated from the millimeter-wave speed sensor 106.

[0016] In Figures 2 and 3, the wheel 209 is shown to make it easier to understand the relationship between the irradiation range of the electromagnetic waves emitted from the millimeter-wave velocity sensor 106 and the rail; however, this does not mean that the wheel is positioned within the irradiation range of the electromagnetic waves. The millimeter-wave velocity sensor 106 is not installed directly above the wheel 209, but rather at a position offset in the forward and backward direction of travel from the position directly above the wheel 209, and it is desirable that the electromagnetic waves emitted from the millimeter-wave velocity sensor are irradiated from an oblique direction to the top of the rail.

[0017] In Figure 2, the distances of the electromagnetic waves emitted from the millimeter-wave velocity sensor are shown, with h1 representing the distance of the electromagnetic waves irradiated onto the top of the rail 210a and h2 representing the distance of the electromagnetic waves irradiated onto the bottom of the rail 210b. In Figure 2, the millimeter-wave velocity sensor is positioned at the inner end of the rail top when the vehicle and the ground are horizontal. However, the position of the center of the millimeter-wave velocity sensor relative to the rail top is not limited to this; the center of the millimeter-wave velocity sensor may be at the center of the rail top or at the outer end of the rail top. Furthermore, in Figure 2, the millimeter-wave velocity sensor is irradiating electromagnetic waves onto one rail, but the number and position of the millimeter-wave sensors are not limited to this; for example, they may be installed on both the left and right rails.

[0018] (If the rails are raised) Next, referring to Figure 3, we will explain the positional relationship between the millimeter-wave velocity sensor, the rail 101, and the roadbed 320 when the train is installed on a member 322 that raises the rails from the roadbed 320, such as in a pit line at a train depot.

[0019] Figure 3 differs from Figure 2 in that the rail 101 is not installed on the track bed 220 as in Figure 2, but rather rests on a member 322 that raises the roadbed 320. For this reason, in the following description, components that are the same as or equivalent to those described in Figure 2 above will be denoted by the same reference numerals, and their descriptions will be simplified or omitted.

[0020] In Figure 3, since the rail is installed on a member 322 that raises it above the roadbed 320, the distance from the millimeter-wave velocity sensor 106 to the target of illumination is h1 to the top of the rail 210a, h2 to the bottom of the rail 210b, and h3 to the roadbed 320. The roadbed 320 is the part of the ground that is walked on by staff and others in a train depot, etc.

[0021] In a situation like that shown in Figure 3, when detecting the speed of a train using a CW millimeter-wave radar, the train is moving at a low speed, and the CW millimeter-wave radar receives reflected waves from various distances, which can lead to a decrease in the accuracy of the speed measurement. Furthermore, the situation shown in Figure 3 can lead to a decrease in the accuracy of speed measurement, not only in train depots but also when traveling on bridges.

[0022] (If the roadbed or track bed is flooded) Furthermore, if the roadbed or track bed is flooded, even if the distance relationship from the millimeter-wave velocity sensor 106 to the target of illumination is the same as shown in Figure 2, the presence of water can cause many secondary reflections, potentially reducing the accuracy of velocity measurement using the CW method.

[0023] <Configuration of millimeter-wave sensor> Next, with reference to Figures 4 and 5, the configuration and processing of the millimeter-wave velocity sensor used in the first embodiment of the present invention will be described. In the following description, we will assume that the sensor can switch between FMCW and CW modes with a single speed sensor. However, the sensor applied to the present invention does not necessarily have to be a sensor that can switch between both modes; it is also possible to use FMCW and CW sensors separately and switch between them.

[0024] Figure 4 illustrates the processing of the millimeter-wave velocity sensor used in the present invention, particularly the processing using the FMCW method. The millimeter-wave velocity sensor used in the present invention outputs a variable frequency from the synthesizer 415 and emits an irradiation wave 418, which is an electromagnetic wave irradiated from the antenna 416. The antenna also receives a reflected wave 419, which is an electromagnetic wave that has been reflected from an object. In this figure, the irradiation wave and the reflected wave are shown to be transmitted and received by a single antenna, but a configuration in which the antenna that transmits the irradiation wave and the antenna that receives the reflected wave are separate is also possible.

[0025] The millimeter-wave velocity sensor has a mixer 417 that combines two frequencies to generate a signal of a new frequency. The mixer acquires the irradiation wave output by the synthesizer and the reflected wave received from the antenna, and performs A / D 420 and FFT that convert analog signals and digital signals. R Perform 421 processing to perform distance conversion 422. Then, perform sampling selection 423 to obtain only the signal of a specific distance component from the distance conversion, and perform FFT V 424 processing to perform velocity conversion 425. In this figure, FFT processing is performed in the process of performing distance conversion and velocity conversion. Since the processing contents are different, they are respectively FFT R and FFT V are classified. Also, after FFT <000001​0>421, an SNR measurement unit 430 is provided to measure and determine whether the component of the reflected wave can be recognized as a signal, and the process of distance conversion 422 may be performed only when the signal exceeds the set threshold.

[0026] FIG. 5 is a diagram for explaining the processing when the millimeter-wave velocity sensor described in FIG. 4 is used in the CW method. In the CW method, since the frequency of the irradiated millimeter wave is constant, a millimeter wave of a constant frequency is generated from the synthesizer 415, and the mixer 417 acquires the irradiation wave output by the synthesizer and the reflected wave 419 received from the antenna, and performs A / D 420 and FFT V 424 processing to perform velocity conversion 425. That is, the velocity of the object is calculated from the change in frequency due to the Doppler effect between the irradiation wave and the reflected wave.

[0027] ​​​​​​​This indicates that if the speed exceeds a certain threshold, the CW (Continuous Wave) method will be used to detect the train's speed. In other words, in the first embodiment, the sensor selection unit 107 selects the FMCW method for the millimeter-wave velocity sensor 106 at speeds below a predetermined speed, and selects the CW method in other speed ranges. A possible threshold speed for switching could be set to, for example, around 30 km / h. In CW speed measurement, the measurement accuracy decreases in the speed range below approximately 30 km / h, so setting this speed as a threshold is reasonable. Furthermore, when trains travel on sections where the rails are raised above the roadbed 320, such as in the pit lines of train depots, they generally travel at speeds of approximately 30 km / h or less. Therefore, setting the threshold to this level can improve the accuracy of speed measurements when trains travel on pit lines. Note that this threshold is not limited to 30 km / h and may be set to other speed levels. For example, it is possible to set the threshold to the speed at which the vehicle travels on bridges or in flooded areas, and to switch to the FMCW method when accurate speed measurement is difficult using the CW method.

[0028] <Modified form of the first embodiment> In the first embodiment, a single threshold was determined, and the CW mode and FMCW mode were switched depending on whether the driving speed exceeded this threshold. However, the threshold for switching between the CW mode and FMCW mode does not necessarily have to be a single threshold; it may be set with hysteresis. For example, as an example of hysteresis, it is possible to set the threshold to 20 mk / h when transitioning from CW mode to FMCW mode, and to 30 km / h when transitioning from FMCW mode to CW mode.

[0029] <Second Embodiment> Next, a second embodiment will be described with reference to Figures 7 to 11. Figure 7 is a diagram illustrating an example of the installation of a speed detection device in the second embodiment. In the second embodiment, as shown in Figure 7, a train formation 700 consisting of one or more vehicles 710 is equipped with multiple speed detection devices, each equipped with an SNR measuring unit, to constitute a speed detection system.

[0030] In the second embodiment, when at least two speed detection devices 103 are installed near the leading end and the trailing end of the train in the direction of travel, the mode switching method between the CW method and the FMCW method in each speed detection device can be set based on the speed detected by each speed detection device (103A, 103B) and the accuracy of the reflected wave in the SNR measurement unit (the accuracy of whether or not the components of the reflected wave can be recognized as a signal).

[0031] (First example) First, with reference to Figure 8, the speed detection system of the first embodiment in the second embodiment will be described. Figure 8 is a flowchart showing the mode switching logic of the first embodiment. In the first embodiment, as shown in Figure 7, when speed detection devices 103A and 103B are installed near the leading and trailing ends of the train in the direction of travel, the system switches between the CW method and the FMCW method by determining whether the speed detected by each speed detection device exceeds an arbitrary threshold speed, for example, 30 km / h. If the speed detection devices near the leading end and the trailing end of the train are designated as the first speed detection device and the second speed detection device, respectively, these devices would normally detect the same speed. Therefore, in the first embodiment, the switching logic described below is applied.

[0032] (Step 801) The initial mode at the start of operation may be either CW or FMCW. Step 803 is performed promptly after the train starts moving.

[0033] (Step 803) In step 803, the driving speed is calculated based on the initial mode set at the start of driving. If the speed exceeds an arbitrary threshold speed, the process proceeds to step 805; otherwise, the process proceeds to step 807.

[0034] (Step 805) In step 805, since the threshold speed is exceeded, control is performed to select the CW method in the sensor selection unit for both the first and second speed detection devices. After that, after an arbitrary time interval, the process returns to step 803 and the travel speed is calculated again.

[0035] (Step 807) In step 807, since the threshold speed has not been exceeded, control is performed to select the FMCW method in the sensor selection unit for both the first and second speed detection devices. After that, after an arbitrary time interval, the process returns to step 803 and the driving speed is calculated again.

[0036] The above describes the mode switching control between the CW method and the FMCW method in the first embodiment. The interval for detecting the travel speed can be set arbitrarily; for example, it may be set to every 0.5 seconds, or it may be set to any other time interval.

[0037] (Second example) Next, a second embodiment relating to the second embodiment will be described with reference to Figures 9 to 11. The second embodiment sets a method for switching between the CW method and the FMCW method when the accuracy of measuring the running speed decreases when the train formation approaches a bridge or puddle while in motion.

[0038] First, referring to Figure 9, we will explain the situation when a train travels through a section where there are puddles on bridges or the track bed. Figure 9 illustrates the situation when a train consisting of four cars approaches a bridge or a section with puddles. When a train traveling from left to right in the diagram approaches a bridge, first, the accuracy of the speed detection device 103A installed at the front of the train in the direction of travel may decrease. Subsequently, the accuracy of the speed detection device 103B installed at the rear of the train in the direction of travel may decrease. Furthermore, the accuracy of the speed detection device 103A at the front of the train in the direction of travel will recover, and then the accuracy of the speed detection device 103B at the rear of the train in the direction of travel will also recover. Furthermore, this situation is not limited to bridge sections; it can occur similarly in sections where there are puddles on the roadbed.

[0039] In this situation, accurately determining the speed of a moving train requires deciding whether to use CW (Continuous Wave) or FMCW (Full-Time Multi-Wave) mode for each speed detection device, and which of the multiple sensors' values ​​should be used to accurately determine the train's speed.

[0040] In the second embodiment, the conditions under which the measurement accuracy of the travel speed of each speed detection device decreases are classified into four categories, and the mode of the speed detection device is set according to each condition. The following explains the four categories of conditions, referring to Figure 10. Note that the conditions shown in Figure 10 assume that, in the initial stage, the speed detection device measures the running speed using the CW method. Also, in the table in Figure 10, a circle (○) indicates a state where the speed detection device has good accuracy in measuring the running speed, while a cross (×) indicates a state where the speed detection device has reduced accuracy in measuring the running speed.

[0041] (Condition 1) If there are no problems with the accuracy of measuring the running speed of either the speed detection device at the front or the speed detection device at the rear, there is no need to switch modes for either speed detection device, and the normal CW method is continued. In this case, the running speed of the train may be calculated based on either speed detection device, or the speeds calculated by multiple speed detection devices may be averaged to determine the running speed of the train.

[0042] (Condition 2) If a problem occurs with the accuracy of the speed detection device at the front of the train, the mode of the speed detection device at the rear of the train will be switched to the FMCW (Full-Motion Control) method. This means that if the train approaches a bridge or similar section and a problem occurs with the accuracy of the speed detection device at the front of the train, the mode of the speed detection device at the rear of the train will be quickly switched to the FMCW method to ensure accurate detection of the train's speed using the rear speed detection device. Then, after a predetermined time has elapsed since the detection accuracy of the sensor in the speed detection device at the front of the vehicle was restored, the sensor selection unit of the speed detection device at the rear of the vehicle will return the speed detection device at the rear of the vehicle to the CW (Continuously Variable) mode. By doing this, after the leading part of the train has passed through the section where measurement accuracy problems occur, all speed detection devices will be able to return to normal mode.

[0043] Furthermore, in order to detect a decrease in the accuracy of the speed detection device's measurement of the train's speed, the measurement results from the SNR measurement unit 430, which measures and determines whether or not the components of the reflected wave can be recognized as a signal, can be used, but this is not the only method. For example, it is also possible to determine that the accuracy of the train's speed measurement has decreased by using the plot bandwidth in the CW method or by observing rapid changes in acceleration.

[0044] Furthermore, the predetermined time required to switch the mode of the rear-end speed detection device, which has been switched to the FMCW method, back to the CW method can be determined by predicting the time it takes for the rear end of the train to pass through the section where measurement accuracy problems occur. For example, if the length of one vehicle is 30m, and the train consists of 10 cars, the total length of the train is approximately 300m. Therefore, if the train speed is 30km / h, it can be assumed that the rear end will pass through the section where measurement accuracy problems occur approximately 36 seconds after the measurement accuracy of the front end has recovered, so the predetermined time can be set to approximately 36 seconds.

[0045] (Condition 3) If the measurement accuracy of the speed detection devices at both the front and rear ends of the train decreases, it suggests that the measurement accuracy of the entire train cannot be ensured by the CW method, and that the entire train is traveling on a bridge section, among other possibilities. In such cases, the modes of the speed detection devices at both the front and rear of the train are switched to the FMCW system, and measures are taken to accurately detect the train's speed using either the front or rear speed detection device. Then, similar to the case of condition 2, after a predetermined time has elapsed since the detection accuracy of the sensor in the leading speed detection device recovered, the sensor selection unit of the rear speed detection device will return the rear speed detection device to the CW (Continuously Variable) mode.

[0046] (Third example) Next, with reference to Figure 11, a third embodiment will be described in which an intermediate speed detection device is installed between the front and rear speed detection devices described in the second embodiment. Fail-safe design is always required for train operation management, and from this perspective, safety can be further enhanced by installing an intermediate speed detection device between the front and rear speed detection devices and by mutually sharing detection accuracy information of all speed detection devices in the train set. Figure 11 is an explanatory diagram showing the case where three speed detection devices, 103A, 103B, and 103C, are distributed and arranged at three locations: the front, rear, and middle of a five-car train. In the case where three speed detection devices are provided in this manner, if the measurement accuracy of the leading and / or trailing speed detection device deteriorates, the mode of the intermediate speed detection device 103C can be temporarily switched to the FMCW method. Once the measurement accuracy of the leading and / or trailing speed detection device recovers, the mode of the intermediate speed detection device 103C can be returned to the CW method after a predetermined time. In this case, the train's speed may be determined based on the calculation result of the intermediate speed detection device 103C, or it may be taken into account by weighting the calculation results of the speed detection devices at the front and / or rear ends. In any case, determining the speed based on the results of multiple speed detection devices makes it possible to perform more safe speed detection.

[0047] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the present invention. The number of vehicles described in the example can be changed as appropriate, and the location and number of speed detection devices can also be changed as appropriate. [Explanation of Symbols]

[0048] 100: Train 101: Rail 102: Train position recognition system 103: Speed ​​detection device 104: On-board control device 106: Millimeter-wave velocity sensor 107: Sensor Selection Section 205: Cabinet 207: Lens 208: Transparent window 209: Wheel 214: Range of electromagnetic wave irradiation 220: Dodoko 320: Roadbed 322: Raising component 415: Synthesizer 417: Mixer 418: Irradiation wave 419:Reflected wave 430: SNR Measurement Unit 700: Formation 710: Vehicle

Claims

1. A speed sensor capable of speed detection using the CW (Continuous Wave) method and the FMCW (Frequency Modulation Continuous Wave) method, A sensor selection unit that selects an FMCW type speed sensor at speeds below a predetermined speed, and a CW type speed sensor in other speed ranges, SNR measurement unit and A speed detection system comprising multiple speed detection devices equipped with the following features within a single train set: When the sensor selection unit of any speed detection device is set to select a CW type speed sensor, When the SNR measurement unit detects a decrease in the detection accuracy of the speed sensor in the first speed detection device located at the front of the vehicle formation in the direction of travel, When the detection accuracy of the speed sensor of the second speed detection device, which is located at the rear in the direction of travel of the aforementioned train set, decreases, the sensor selection units of both the first speed detection device and the second speed detection device shall select an FMCW type speed sensor. When the detection accuracy of the speed sensor of the second speed detection device has not deteriorated, the sensor selection unit of the first speed detection device continues to select a CW type speed sensor, and the sensor selection unit of the second speed detection device selects a FMCW type speed sensor. After a predetermined time has elapsed since the detection accuracy of the speed sensor in the first speed detection device recovered, the sensor selection unit of the second speed detection device selects a CW type speed sensor for the second speed detection device. Speed ​​detection system.

2. A speed detection system according to claim 1, The speed detection system includes a third speed detection device in the intermediate region of the vehicle formation in the direction of travel between the first speed detection device and the second speed detection device. When the detection accuracy of the speed sensor of the first speed detection device decreases, the sensor selection unit of the third speed detection device selects an FMCW type speed sensor for at least a predetermined time. When the detection accuracy of the speed sensor of the first speed detection device is restored, the sensor selection unit of the third speed detection device selects a CW type speed sensor. The train's speed is determined based on the speeds calculated by the first, second, and third speed detection devices. Speed ​​detection system.

3. In a train set equipped with multiple speed detection devices, each consisting of a speed sensor capable of switching between the CW (Continuous Wave) method and the FMCW (Frequency Modulation Continuous Wave) method, a sensor selection unit, and an SNR measurement unit, The sensor selection unit selects an FMCW type speed sensor for speeds below a predetermined speed, and a CW type speed sensor for speeds in other speed ranges. In a speed detection method, When the sensor selection unit of any speed detection device is set to select a CW type speed sensor, When the SNR measurement unit detects a decrease in the detection accuracy of the speed sensor in the first speed detection device located at the front of the vehicle formation in the direction of travel, When the detection accuracy of the speed sensor of the second speed detection device, which is located at the rear in the direction of travel of the aforementioned train set, decreases, the sensor selection units of both the first speed detection device and the second speed detection device shall select an FMCW type speed sensor. When the detection accuracy of the speed sensor of the second speed detection device has not deteriorated, the sensor selection unit of the first speed detection device continues to select a CW type speed sensor, and the sensor selection unit of the second speed detection device selects a FMCW type speed sensor. After a predetermined time has elapsed since the detection accuracy of the sensor in the first speed detection device was restored, the sensor selection unit of the second speed detection device selects a CW type speed sensor for the second speed detection device. Speed ​​detection method.

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