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

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

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

[0002] Previously, trains received location information from a ground coil installed between a pair of rails, and calculated their current position by sequentially adding the amount of movement obtained from the number of wheel rotations to that information. However, the tachometer generator used to measure wheel rotations has difficulty making accurate measurements when wheel slippage or sliding occurs, which causes a loss of adhesion between the rail and wheels.

[0003] For this reason, sensors that detect ground speed non-contactly using millimeter-wave radio waves and are installed under the floor of a train have also been developed. For example, Patent Document 1 discloses the following speed detection device: "The speed measurement device 1 is installed under the floor of a vehicle and has a transmitting function of irradiating electromagnetic waves (irradiated waves) onto the rails 7 (or, more broadly, the track including the rails 7) and a receiving function of acquiring the electromagnetic waves (reflected waves) that return after hitting the rails 7. The transmitting function and the receiving function may be implemented by independent antennas, or may be implemented by a single antenna having transmitting and receiving functions. The speed measurement device 1 also has a speed calculation function that inputs the reflected waves acquired by the receiving function into a calculation unit, and the calculation unit calculates a train speed signal based on the frequencies of the irradiated waves and the reflected waves. More specifically, the speed calculation function of the speed measurement device 1 utilizes the fact that, when a train is running, the frequencies of the electromagnetic waves irradiated onto the rails 7 (irradiated waves) and the electromagnetic waves reflected by the rails 7 (reflected waves) differ due to the Doppler effect, and calculates the speed signal based on this frequency difference."

[0004] Japanese Patent Application Laid-Open No. 2021-18205

[0005] The speed measurement device disclosed in Patent Document 1 employs a millimeter-wave radar called a CW (Continuous Wave) type, which emits radio waves at a constant frequency. However, at low speeds, accurate speed detection tends to be difficult, whether using a tachograph or a CW millimeter-wave radar, unless the sampling time is set long. In particular, CW millimeter-wave radar irradiates not only the rail itself but also the rail trackbed, detecting speed based on the reflected waves from the trackbed. As a result, speed detection accuracy is problematic in areas where the radar reflection conditions of the road surface vary, such as pit lines, bridges, 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 to high speeds.

[0006] In order 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, wherein the speed sensor is capable of detecting speed by a CW (Continuous Wave) method and an FMCW (Frequency Modulation Continuous Wave) method, and the sensor selection unit selects an FMCW method speed sensor below a certain speed, and selects a CW method speed sensor in other speed ranges.

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

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

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to these embodiments. In the drawings, identical parts are denoted by the same reference numerals. When multiple components having the same or similar functions are present, they may be described using the same reference numerals with different subscripts. Furthermore, when it is not necessary to distinguish between these multiple components, the subscripts may be omitted. Furthermore, although terms such as "first," "second," and "third" may be used to describe various elements or components in this disclosure, it should be understood that these elements or components should not be limited by these terms. These terms are used only to distinguish one element or component from another. Therefore, a first element or component discussed below may also be referred to as a second element or component without departing from the teachings of the inventive concept. The position, size, shape, range, etc. of each component shown in the drawings may not represent the actual position, size, shape, range, etc., in order to facilitate understanding of the invention. Therefore, the present invention is not necessarily limited to the position, size, shape, range, etc. disclosed in the drawings.

[0010] <CW Method and FMCW Method> First, the method of the millimeter wave sensor used in this disclosure will be described. Millimeter wave sensors include a CW method that irradiates millimeter waves of a fixed frequency and detects speed from the change in frequency between the irradiated wave and the reflected wave (Doppler effect), and an FMCW method that varies the frequency of the emitted radio waves within a fixed frequency band.

[0011] The CW method detects the speed of an object illuminated with millimeter waves from the Doppler effect of the emitted and reflected waves, but it cannot calculate the distance from the sensor to the illuminated object. As a result, the CW method cannot distinguish between waves reflected from the rail and waves reflected from the trackbed, and speed detection accuracy may decrease if the trackbed or road surface environment changes.

[0012] On the other hand, the FMCW method emits millimeter waves whose frequency changes at a constant rate, and can calculate the distance from the sensor to the target from the frequency deviation that occurs due to the time difference between the emitted wave and the reflected wave. This makes it possible to separate the signals for multiple targets based on distance information, and to analyze the primary reflected wave from a signal that is determined to be a rail. This makes it possible to accurately calculate the speed of the target. However, in the FMCW method, since speed measurement is based on changes in distance information, i.e., the phase change relative to the aforementioned frequency deviation, the wavelength of the emitted millimeter waves is set to λ, and the time interval between the repeatedly emitted signals in band B is set to T. ｃ In this case, v shown in the following equation (1) ｍａｘ is the upper limit of the measurement speed. ｍａｘ <λ / 4T ｃ ・・・・・・・・・(1) In other words, when λ is 4 mm and Tc is 40 μs, v ｍａｘ is approximately 90 km / h. Furthermore, the FMCW method requires a larger calculation load than the CW method, making it less suitable for measurements at high speeds.

[0013] On the other hand, the speed range of high-speed trains is wide, from 0 km / h to 400 km / h, and there was a demand for a speed detection method that could accurately detect speed across this speed range, even under various road conditions.

[0014] First Embodiment First, referring to FIG. 1 , an example of a speed detection device mounted on a train will be described. In FIG. 1 , a train 100 is a vehicle intended to operate on tracks with various road surface conditions, both at stations and outside stations. Generally, a train is composed of multiple coupled vehicles. However, for simplicity's sake, FIG. 1 only shows the configuration of a vehicle (the lead vehicle) that constitutes the train. Also, while FIG. 1 illustrates an example in which a train position recognition system that measures the vehicle's speed is mounted on the lead vehicle, in the train position recognition system according to the present invention, the speed measurement device may be mounted on another vehicle. As shown in FIG. 1 , a train position recognition system 102 is mounted on a train 100 traveling on rails 101, and the train position recognition system includes 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. The on-board control device can acquire the position at any point using a transponder (not shown) installed on the ground, and calculate the travel distance from the any point using the distance calculated from the speed information acquired from the speed detection device.

[0015] (On a normal route) Next, the positional relationship between the millimeter-wave speed sensor and the track bed when the train 100 is located on a normal route will be described with reference to Figure 2. 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 within a housing 205 and includes a lens 207 that controls the irradiation range of the electromagnetic waves and a transparent window 208 that emits the electromagnetic waves of the millimeter-wave sensor to the outside of the speed measuring device. The millimeter-wave speed sensor 106 is installed under the vehicle so that the rail 101 is included in the irradiation range 214 of the electromagnetic waves emitted from the millimeter-wave speed sensor 106.

[0016] 2 and 3, wheels 209 are shown to make it easier to understand the relationship between the rail and the irradiation range of the electromagnetic waves emitted from millimeter-wave speed sensor 106, but this does not mean that the wheels are located within the irradiation range of the electromagnetic waves. The millimeter-wave speed sensor 106 is not installed directly above the wheels 209, but is installed in a position offset in the longitudinal direction of the traveling direction from the position directly above the wheels 209, and it is desirable that the electromagnetic waves emitted from the millimeter-wave speed sensor be irradiated from an oblique direction to the top of the rail.

[0017] In FIG. 2, the distance of the electromagnetic wave irradiated from the millimeter wave speed sensor to the rail head portion 210a is h １ , the distance of the electromagnetic wave irradiated to the rail bottom 210b is h ２ In Figure 2, when the vehicle and the ground are horizontal, the millimeter-wave speed sensor is positioned at the inner edge of the rail top, but the positions of the center of the millimeter-wave speed sensor and the rail top are not limited to this, and the center of the millimeter-wave speed sensor may be at the center of the rail top or at the outer edge of the rail top. Furthermore, in Figure 2, the millimeter-wave speed sensor irradiates electromagnetic waves onto one rail, but the number and positions of the millimeter-wave sensors are not limited to this, and millimeter-wave sensors may be installed on both the left and right rails, for example.

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

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

[0020] In FIG. 3, the rail is installed on a member 322 that raises the rail from the roadbed 320, so the distance from the millimeter wave velocity sensor 106 to the target to be irradiated is the distance h １ , distance h to the rail bottom 210b ２ , distance h to the roadbed 320 ３ The roadbed 320 is the ground surface on which staff and others pass in a vehicle depot or the like.

[0021] In the situation 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 reduce the accuracy of speed measurement.The situation shown in Figure 3 can also occur when the train is traveling over a bridge, not just at a railyard.

[0022] (When the roadbed or trackbed is flooded) Furthermore, when the roadbed or trackbed is flooded, even if the distance relationship from the millimeter wave speed sensor 106 to the target to be irradiated is the same as that shown in Figure 2, the presence of the water surface can cause a lot of secondary reflections, which can reduce the accuracy of speed measurement using the CW method.

[0023] <Configuration of Millimeter-Wave Sensor> Next, the configuration and processing of the millimeter-wave velocity sensor used in the first embodiment of the present invention will be described with reference to Figures 4 and 5. Note that in the following description, a single velocity sensor will be described as being capable of switching between the FMCW method and the CW method, but the sensor applied to the present invention does not necessarily have to be a sensor capable of switching between both methods, and it is also possible to use an FMCW sensor and a CW sensor and switch between them.

[0024] 4 is a diagram illustrating the processing of the millimeter-wave velocity sensor used in the present invention, particularly the processing in the FMCW system. The millimeter-wave velocity sensor used in the present invention outputs a variable frequency from a synthesizer 415 and emits an irradiated wave 418, which is an electromagnetic wave irradiated from an antenna 416. The antenna also receives a reflected wave 419, which is an electromagnetic wave that is the irradiated wave reflected by an object. In this diagram, the irradiated wave and the reflected wave are transmitted and received by a single antenna, but a configuration in which the antenna that transmits the irradiated wave and the antenna that receives the reflected wave are separate may also be used.

[0025] The millimeter wave velocity sensor has a mixer 417 that combines two frequencies to generate a signal of a new frequency, and the mixer receives the irradiated wave output by the synthesizer and the reflected wave received from the antenna, and converts the analog signal into a digital signal using an A / D 420 and an FFT. Ｒ 421 is executed to perform distance conversion 422. After that, sampling selection 423 is executed to acquire only signals of specific distance components from the distance conversion, and FFT is performed. Ｖ In this figure, FFT processing is performed in the process of distance conversion and velocity conversion, but since the processing contents are different, FFT processing is performed in each case. Ｒ and FFT Ｖ Also, FFT Ｒ After 421, an SNR measurement unit 430 may be provided to measure and determine whether the reflected wave components can be recognized as a signal, and the distance conversion 422 process may be performed only if the signal exceeds a set threshold.

[0026] 5 is a diagram for explaining the processing when the millimeter wave velocity sensor described in FIG. 4 is used in the CW system. In the CW system, the frequency of the irradiated millimeter wave is constant, so a synthesizer 415 generates a millimeter wave of a constant frequency, a mixer 417 acquires the irradiated wave output by the synthesizer and a reflected wave 419 received from the antenna, and the A / D 420 and FFT 430 convert the analog signal to a digital signal. V The process of 424 is executed to perform velocity conversion 425. In other words, the velocity of the object is calculated from the change in frequency due to the Doppler effect of the irradiated wave and the reflected wave.

[0027] <First embodiment> Next, a first embodiment of the present disclosure will be described with reference to Fig. 6. Fig. 6 is a diagram illustrating an example in which the sensor method to be applied is switched depending on the running speed of a train. In Fig. 6, the vertical axis represents the running speed of the train, and the horizontal axis represents time. When the running speed of the train exceeds a threshold V ｔｈ In the following cases, the FMCW method is adopted to detect the train's running speed, and the train's running speed exceeds the threshold V ｔｈ , the CW method is adopted to detect the train's running speed. In other words, in the first embodiment, the sensor selection unit 107 selects the FMCW method for the millimeter-wave speed sensor 106 when the speed is below a predetermined speed, and selects the CW method for other speed ranges. The predetermined speed serving as the switching threshold can be set to, for example, about 30 km / h. Since the measurement accuracy of the CW method for speed measurement decreases at speeds below about 30 km / h, it is reasonable to set this speed as the threshold. Furthermore, even when a train travels through a section where the rails are elevated above the roadbed 320, such as a pit line at a rail depot, the train travels at a speed below about 30 km / h. Therefore, setting the threshold at this level can improve the speed accuracy when traveling along the pit line. Note that this threshold is not limited to 30 km / h and may be set to another speed level. For example, it is possible to set a threshold value based on the driving speed when traveling over a bridge or in a flooded area, and switch to the FMCW method when it is difficult to accurately measure the speed using the CW method.

[0028] In the first embodiment, a single threshold value is determined, and switching between the CW mode and the FMCW mode is performed depending on whether the traveling speed exceeds the threshold value. However, the threshold value for switching between the CW mode and the FMCW mode does not necessarily have to be a single threshold value, and may be set with hysteresis. For example, as an example of hysteresis, the threshold value for transitioning from the CW mode to the FMCW mode may be set to 20 km / h, and for transitioning from the FMCW mode to the CW mode, it may be set to 30 km / h.

[0029] <Second embodiment> Next, a second embodiment will be described with reference to Fig. 7 to Fig. 11. Fig. 7 is a diagram illustrating an example of installation of a speed detection device in the second embodiment. In the second embodiment, as shown in Fig. 7, a train formation 700 consisting of one or more cars 710 is provided with a plurality of speed detection devices each equipped with an SNR measurement unit, thereby constituting a speed detection system.

[0030] In the second embodiment, when at least two speed detection devices 103 are installed near the front end and rear end of the train in the traveling direction, respectively, a method of switching between the CW and FMCW modes 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 the component of the reflected wave can be recognized as a signal).

[0031] (First Example) First, a speed detection system according to a first example of the second embodiment will be described with reference to FIG. 8. FIG. 8 is a flowchart showing the mode switching logic of the first example. In the first example, as shown in FIG. 7, when speed detection devices 103A and 103B are installed near the front and rear ends of a 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 value, for example, 30 km / h. If the speed detection devices near the front and rear ends of the train in the direction of travel are designated as the first and second speed detection devices, respectively, these devices normally detect the same speed, and therefore the switching logic described below is applied in the first example.

[0032] (Step 801) The initial mode at the start of running may be the CW system or the FMCW system. After the train starts running, the process proceeds to step 803 immediately.

[0033] (Step 803) In step 803, the running speed is calculated based on the initial mode set at the start of running, and if it exceeds a threshold speed that can be set arbitrarily, the process proceeds to step 805, and if it does not exceed the threshold speed, the process proceeds to step 807.

[0034] (Step 805) In step 805, since the speed exceeds the threshold value, the sensor selection unit is controlled to select the CW method for both the first speed detection device and the second speed detection device. After that, after an arbitrary time interval, the process returns to step 803 and the traveling speed is calculated again.

[0035] (Step 807) In step 807, since the speed does not exceed the threshold value, the sensor selection unit is controlled to select the FMCW method for both the first speed detection device and the second speed detection device. After that, after an arbitrary time interval, the process returns to step 803 and the traveling speed is calculated again.

[0036] The above is the mode switching control between the CW method and the FMCW method in Example 1. The interval at which the traveling speed is detected can be set arbitrarily, and for example, it may be performed every 0.5 seconds or at other time intervals.

[0037] 9 to 11, a second example of the second embodiment will be described. The second example sets a method for switching between the CW and FMCW modes when a train comes across a bridge or a puddle while traveling, causing a decrease in the accuracy of measuring the traveling speed.

[0038] First, referring to FIG. 9 , a situation in which a train travels through a section where there is a bridge or puddle on the roadbed will be described. FIG. 9 illustrates a situation in which a four-car train approaches a section where there is a bridge or puddle. When a train traveling from left to right in the drawing approaches a bridge, the accuracy of measuring the running speed of speed detection device 103A installed at the front of the train in the direction of travel may decrease. Then, the accuracy of measuring the running speed of speed detection device 103B installed at the rear end of the train in the direction of travel may decrease. Furthermore, the accuracy of measuring the running speed of speed detection device 103A installed at the front of the train in the direction of travel may recover, and then the accuracy of measuring the running speed of speed detection device 103B installed at the rear end of the train in the direction of travel may also recover. This situation is not limited to bridges, but may also occur in sections where there is puddle on the roadbed.

[0039] In such a situation, in order to accurately grasp the running speed of a moving train, the problem is whether each speed detection device should use the CW or FMCW mode for speed detection, and which of the multiple sensors should be used to accurately grasp the running speed of the train.

[0040] In the second embodiment, the conditions under which the measurement accuracy of the traveling speed of each speed detection device decreases are classified into four categories, and the speed detection device mode is set according to each condition. The four classified conditions will be explained below with reference to FIG. 10 . The conditions shown in FIG. 10 are based on the premise that the speed detection device initially measures the traveling speed using the CW method. In the table of FIG. 10 , a circle indicates a state in which the measurement accuracy of the traveling speed of the speed detection device is good, and an x ​​indicates a state in which the measurement accuracy of the traveling speed of the speed detection device has decreased.

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

[0042] (Condition 2) If a problem occurs in the running speed measurement accuracy of the speed detection device at the front end, the mode of the speed detection devices at the rear end is switched to FMCW mode. This means that if a train formation approaches a bridge or other section and a problem occurs in the running speed measurement accuracy of the speed detection device at the front end, the mode of the speed detection device at the rear end is quickly switched to FMCW mode, so that the speed detection device at the rear end can accurately detect the train's speed. Then, after a predetermined time has passed since the detection accuracy of the sensor in the speed detection device at the front end has recovered, the sensor selection unit of the speed detection device at the rear end returns the speed detection device at the rear end to CW mode. This allows both speed detection devices to return to their normal mode after the front end of the formation has passed the section where the measurement accuracy problem occurs.

[0043] In order to detect a decrease in the measurement accuracy of the traveling speed of the speed detection device, the measurement results by the SNR measurement unit 430, which measures and determines whether or not the reflected wave component can be recognized as a signal, can be used, but the method is not limited to this. For example, it is also possible to determine that the measurement accuracy of the traveling speed has decreased using a plot bandwidth in the CW method or a sudden change in acceleration.

[0044] Furthermore, the predetermined time required for the speed detection device of the rear end portion, which has been switched from the FMCW system, to return to the CW system can be determined by predicting the time required for the rear end portion of the train to pass through the section where measurement accuracy is problematic. For example, if each car is 30 m long and the train consists of 10 cars, the length of the train is approximately 300 m. Therefore, if the train speed is 30 km / h, it can be assumed that the rear end will be able to pass through the section where measurement accuracy is problematic approximately 36 seconds after the measurement accuracy of the front car is restored, and therefore the predetermined time can be set to approximately 36 seconds.

[0045] (Condition 3) If the running speed measurement accuracy of the speed detection devices at both the front and rear ends of the train decreases, it may be that the measurement accuracy of the entire train set cannot be ensured using the CW method, and the entire train set is traveling over a bridge. In such a case, the mode of the speed detection devices at both the front and rear ends of the train is switched to the FMCW method, and measures are taken to ensure that the speed of the train is accurately detected using the speed detection devices at the front or rear ends. Then, as in Condition 2, the sensor selection unit of the speed detection device at the rear end of the train will return the speed detection device at the rear end to the CW method a predetermined time after the detection accuracy of the sensor in the speed detection device at the front end has recovered.

[0046] Third Embodiment Next, referring to FIG. 11 , a third embodiment will be described in which a speed detection device is installed between the speed detection devices at the front and rear ends of the train described in the second embodiment. A fail-safe design is always required for train running management. From this perspective, installing a speed detection device at the middle between the speed detection devices at the front and rear ends and sharing detection accuracy information of all speed detection devices in the train can further enhance safety. FIG. 11 is an explanatory diagram of a five-car train with three speed detection devices 103A, 103B, and 103C distributed at three locations: the front, rear, and middle of the train. With this three speed detection devices, if the measurement accuracy of the speed detection devices at the front and / or rear ends decreases, the speed detection device 103C located in the middle can be temporarily switched to the FMCW mode. When the measurement accuracy of the speed detection devices at the front and / or rear ends is restored, the speed detection device 103C located in the middle can be switched back to the CW mode after a predetermined time. In this case, the running speed of the train may be determined based on the calculation results of the speed detection device 103C located in the middle, or may be taken into account by taking a weighted average of the calculation results of the speed detection devices at the front and / or rear ends. In either case, determining the speed based on the results of multiple speed detection devices enables safer speed detection.

[0047] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present invention. The number of vehicles described as examples can be modified as appropriate, and the locations and number of speed detection devices can also be modified as appropriate.

[0048] 100: Train 101: Rail 102: Train position recognition system 103: Speed ​​detection device 104: On-board control device 106: Millimeter-wave speed sensor 107: Sensor selection unit 205: Housing 207: Lens 208: Transparent window 209: Wheel 214: Electromagnetic wave irradiation range 220: Track bed 320: Roadbed 322: Raising member 415: Synthesizer 417: Mixer 418: Irradiated wave 419: Reflected wave 430: SNR measurement unit 700: Formation 710: Vehicle

Claims

1. A speed detection device equipped with a speed sensor and a sensor selection unit, wherein the speed sensor is capable of detecting speed using a CW (Continuous Wave) method and an FMCW (Frequency Modulation Continuous Wave) method, and the sensor selection unit selects an FMCW type speed sensor below a predetermined speed, and selects a CW type speed sensor for other speed ranges.

2. A speed detection device according to claim 1, characterized in that said speed detection device comprises an SNR determination unit.

3. A speed detection system comprising a plurality of the speed detection devices according to claim 2 in one trainset, wherein, when the sensor selection units of all the speed detection devices select a CW type speed sensor, if the detection accuracy of the speed sensor in a first speed detection device arranged at the front in the direction of travel declines and the detection accuracy of the speed sensor in a second speed detection device arranged at the rear in the direction of travel declines, the sensor selection units of both the first speed detection device and the second speed detection device select an FMCW type speed sensor, and when the detection accuracy of the speed sensor of the second speed detection device has not declined, the sensor selection unit of the first speed detection device continues to select the CW type speed sensor and the sensor selection unit of the second speed detection device selects the FMCW type speed sensor, and a predetermined time after the detection accuracy of the speed sensor in the first speed detection device has recovered, the sensor selection unit of the second speed detection device selects the CW type speed sensor for the second speed detection device.

4. A speed detection system as claimed in claim 3, comprising a third speed detection device in an intermediate region in the direction of travel between the first speed detection device and the second speed detection device, wherein when the detection accuracy of the speed sensor of the first speed detection device decreases, a sensor selection unit of the third speed detection device selects an FMCW type speed sensor for at least a predetermined period of time, and 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, and the speed of the train is determined based on the speeds calculated by the first, second and third speed detection devices.

5. A speed detection method in a rolling stock formation having one or more speed detection devices equipped with a speed sensor capable of switching between CW (Continuous Wave) and FMCW (Frequency Modulation Continuous Wave) systems and a sensor selection unit, wherein the sensor selection unit selects an FMCW type speed sensor when the speed is below a predetermined speed, and selects a CW type speed sensor in other speed ranges.

6. A speed detection method as claimed in claim 5, wherein, when the detection accuracy of the speed sensor in a first speed detection device arranged at the front in the traveling direction decreases while the sensor selection units of both speed detection devices have selected a CW type speed sensor, and when the detection accuracy of the speed sensor of a second speed detection device arranged at the rear in the traveling direction decreases, the sensor selection units of both the first speed detection device and the second speed detection device select an FMCW type speed sensor, and when the detection accuracy of the speed sensor of the second speed detection device has not decreased, the sensor selection unit of the first speed detection device continues to select the CW type speed sensor and the sensor selection unit of the second speed detection device selects the FMCW type speed sensor, and a predetermined time after the detection accuracy of the sensor in the first speed detection device has recovered, the sensor selection unit of the second speed detection device selects the CW type speed sensor for the second speed detection device.

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