Position Detection System

Abstract

To accurately detect a position of a vehicle traveling on a track at low cost.SOLUTION: A position detection system 1 detects the position of a vehicle 2 traveling on a track. The position detection system 1 includes a sign 3 provided on the track or in the vicinity of the track and an LiDAR 4 and a processing part 5 provided on the vehicle 2. The sign 3 has a plurality of recursive reflectors 6 and indicates information by an arrangement pattern of the recursive reflectors 6. The LiDAR 4 emits laser beam toward the front of the vehicle 2 and detects the arrangement pattern of the recursive reflectors 6 by the reflected light to measure a distance to the sign 3. The processing part 5 acquires position information of the sign 3 based on the information indicated by the arrangement pattern of the recursive reflectors 6 and calculates the position of the vehicle 2 from the position information of the sign 3 and the distance to the sign 3.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a position detection system for detecting the position of a vehicle. [Background technology]

[0002] One method for detecting the position of a vehicle on the ground is to use track circuits. Track circuits require a large maintenance burden for railway operators. The most common method for detecting the position of a vehicle on the vehicle side is to use a tachometer generator. This is because satellite positioning cannot be used inside tunnels.

[0003] In the detection method using a tachograph, the rotation of the wheels is detected by the tachograph, and the travel distance of the vehicle is calculated from the number of rotations of the wheels and the wheel diameter.

[0004] However, errors occur in the wheel rotation count due to wheel skidding and spinning. Furthermore, as wheel diameters become smaller due to wear, the difference from the initial diameter used in calculations increases, resulting in errors in the calculation of the mileage. Therefore, the detection method using a tachometer generator accumulates errors in the calculated mileage, and information for error correction is required.

[0005] Furthermore, in order to know the position of the vehicle, not only the travel distance but also information on the initial position or absolute position of the specific point of the vehicle is required.

[0006] Conventionally, there has been known a train position detection device that uses a tachograph to calculate the running distance, and uses an on-board coil to detect a known position of the ground coil to correct the position information of the train itself (see, for example, Patent Document 1). However, the installation of the ground coil is expensive. In addition, the ground coil can be damaged by snow falling from the vehicle, and repairs are costly.

[0007] Furthermore, for trains that detect their position using radio waves, there is known an initial train position setting device that has an on-board coil and an on-board transponder mounted on the train and a ground coil and a ground transponder installed on the ground (see Patent Document 2). This initial train position setting device sets the initial position of the train using electromagnetic coupling between the on-board coil and the ground coil and communication between the on-board transponder and the ground transponder. However, installing the ground coil and the ground transponder is costly.

[0008] Since the on-board coil is electromagnetically coupled directly above the ground coil, the presence of the ground coil is not known until it is directly above the ground coil. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Utility Model Application Publication No. 4-108479 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-359156 Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention is intended to solve the above problems, and has as its object to detect the position of a vehicle traveling on a track at low cost and with high accuracy. [Means for solving the problem]

[0011] The position detection system of the present invention is a system for detecting the position of a vehicle traveling on a track, and comprises a marking provided on or near the track, and a LiDAR and processing unit provided on the vehicle, wherein the marking has a plurality of retroreflectors and indicates information by the arrangement pattern of the retroreflectors, the LiDAR emits laser light ahead of the vehicle, detects the arrangement pattern by the reflected light, and measures the distance to the marking, and the processing unit obtains position information of the marking based on the information indicated by the arrangement pattern, and calculates the position of the vehicle from the position information of the marking and the distance to the marking.

[0012] In this position detection system, each of the retroreflectors preferably constitutes a dot or a line on the marking.

[0013] In this position detection system, the marking may have the retroreflectors forming a plurality of dots in an area sandwiched between the retroreflectors forming a plurality of lines.

[0014] In this position detection system, the information indicated by the sign is identification information for uniquely identifying the sign, and the processing unit pre-stores the identification information of the sign in correspondence with additional information, and it is preferable that the additional information includes position information of the sign.

[0015] In this position detection system, the vehicle may be operated as a train between stations, the signs may be provided at stations, and the additional information may further include station information regarding the stations.

[0016] In this position detection system, the station information may include a station name or a station number.

[0017] In this position detection system, the station information may include a distinction between stations where the train stops and stations where the train passes through.

[0018] In this position detection system, the station information may include a track number of the station.

[0019] In this position detection system, the station information may include information on train stop position targets.

[0020] In this position detection system, the station information may include information about doors that open at the station.

[0021] In this position detection system, the arrangement pattern preferably has redundancy for error detection or error correction. [Effects of the Invention]

[0022] According to the position detection system of the present invention, since a marking having a retroreflector is provided on or near the track, the position of a vehicle can be detected at a lower cost than by providing a ground coil on the track. Furthermore, since the laser light of the LiDAR is used to measure the distance to the marking, the position of the vehicle can be detected with high accuracy. Furthermore, since the LiDAR emits a laser light ahead of the vehicle, the position of the vehicle can be detected from just before the marking. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a configuration diagram of a position detection system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a plan view illustrating the arrangement of signs in the system. [Figure 3] Figures 3(a) to (d) are examples of LiDAR displays in this system. [Figure 4] FIG. 4 is a plan view illustrating an example of the arrangement of marks in a position detection system according to a modified embodiment of the present invention. [Figure 5] Figures 5(a) and (b) are examples of LiDAR displays in this modified example. [Figure 6] FIG. 6 is a plan view showing the arrangement of signs in an embodiment of the present invention. [Figure 7] FIG. 7 is a plan view showing the arrangement of signs in another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] A position detection system according to one embodiment of the present invention will be described with reference to Figs. 1 to 5. As shown in Fig. 1, the position detection system 1 is a system for detecting the position of a vehicle 2 traveling on a track. The position detection system 1 includes a sign 3, a LiDAR 4, and a processing unit 5. The sign 3 is provided on the track or near the track. The LiDAR 4 and the processing unit 5 are provided on the vehicle 2. The sign 3 has a plurality of retroreflectors 6, and indicates information by the arrangement pattern of the retroreflectors 6.

[0025] The LiDAR 4 emits laser light L ahead of the vehicle 2, and detects the arrangement pattern of the retroreflectors 6 on the sign 3 by the reflected light, and measures the distance to the sign 3.

[0026] The processing unit 5 acquires the position information of the sign 3 based on the information indicated by the arrangement pattern of the retroreflectors 6, and calculates the position of the vehicle 2 from the acquired position information of the sign 3 and the measured distance to the sign 3. The position of the vehicle 2 is expressed in kilometers, for example.

[0027] The position detection system 1 will now be described in further detail. The vehicle 2 is, for example, a streetcar (see the Railway Act). The vehicle 2 may also be a regular railway vehicle (see the Railway Business Act).

[0028] The processing unit 5 is a computer having a CPU, memory, etc., and functions by executing a program (see FIG. 1). The processing unit 5 processes the data input from the LiDAR 4 and outputs the processing results. The processing results are output to, for example, a display mounted on the vehicle 2, or a device or other system that uses the processing results.

[0029] LiDAR is an abbreviation for Light Detection and Ranging or Laser Imaging Detection and Ranging, and is also written as LIDAR. Generally, LiDAR emits laser light and measures the distance to an object that reflects that light, as well as detecting the object's position and shape.

[0030] In the position detection system 1, the LiDAR 4 is used to detect the arrangement pattern of the retroreflectors 6 on the sign 3 and to measure the distance to the sign 3. In other words, the sign 3 is a target marker for the LiDAR 4.

[0031] Retroreflection is a reflection in which light is selectively reflected back in a direction roughly along the optical path of the incident light over a wide illumination angle (see JIS Z8713 "Retroreflectors - Optical properties - Terminology"). Retroreflectors have a surface that returns most of the reflected light (see the same JIS). For example, a transparent synthetic resin embedded with many tiny glass spheres with a high refractive index retroreflects incident light using the glass spheres.

[0032] As shown in FIG. 2 , in this embodiment, each retroreflector 6 forms a dot (a point having a certain size) on the marking 3. One specific example of the retroreflector 6 forming a dot is a retroreflective road stud. A road stud has an outer shape that protrudes from the road surface and has a reflective surface at least on the side facing oncoming vehicles. For example, the road stud has an outer shape of a polygonal pyramid such as a square pyramid or a cone, and is installed so that the cone surface facing oncoming vehicles becomes the reflective surface. The road stud is installed on the track. For example, in the case of a combined track for trams, the road stud is fixed to the road surface. In the case of a slab track, the road stud is fixed to the slab. In the case of a ballasted track, the road stud is fixed to the sleeper.

[0033] In the example of Figure 2, the arrangement pattern of the retroreflectors 6 is a two-dimensional code of 3 cells x 3 cells. Each cell has a binary value (1 bit) depending on whether a dot is present or absent. The number of cells may be more than 3 x 3.

[0034] The arrangement pattern of the retroreflectors 6 has redundancy for error detection or error correction. That is, an error detection code or an error correction code (redundant bits) is added to the data portion of the arrangement pattern of the retroreflectors 6. This allows the position detection system 1 to obtain the information indicated by the markings 3 even if a small number of retroreflectors 6 cannot be read, making the system more resistant to noise (external light such as sunlight) and reducing the frequency of repairs or replacements of the retroreflectors 6.

[0035] 3(a) to (d) show examples of the display of the LiDAR 4 when the signs 3 (3a, 3b, 3c, 3d) are viewed from the LiDAR 4. The display examples in these figures are equivalent to perspective views of the signs 3 as viewed from the LiDAR 4. Note that some LiDARs are capable of displaying a bird's-eye view from directly above. FIGS. 3(a), (b), (c), and (d) correspond to the signs 3a, 3b, 3c, and 3d in FIG. 2, respectively.

[0036] The laser light emitted by the LiDAR 4 is reflected not only by the sign 3 but also by surrounding objects. The strength of the reflection is expressed as brightness as seen by the LiDAR 4. The retroreflector 6 of the sign 3 retroreflects the laser light emitted by the LiDAR 4, increasing the brightness. The LiDAR 4 detects the retroreflector 6 by setting a threshold for the brightness to be detected, thereby distinguishing it from surrounding objects.

[0037] Based on the arrangement pattern of the retroreflectors 6 detected by the LiDAR 4, the processing unit 5 reads information indicated by the arrangement pattern (see FIG. 1).

[0038] As shown in FIG. 4, in a modified example of the marking 3 in this embodiment, each retroreflector 6 forms a line in the marking 3. The line may be, for example, a straight line, a polygonal line, an open curve, a closed curve, or the like. One specific example of the retroreflector 6 forming the line is retroreflective reflective tape. The reflective tape is attached to the track. For example, in the case of a combined track for trams, the reflective tape is attached to the road surface. In the case of a slab track, the reflective tape is attached to the slab. In the case of a ballasted track, the reflective tape is attached to the sleepers.

[0039] In the example of FIG. 4, the arrangement pattern of the retroreflectors 6 is determined by the lengths and relative positions of each of a plurality of reflective tapes.

[0040] The arrangement pattern of the retroreflectors 6 has redundancy for error detection or error correction.

[0041] 5(a) and (b) show examples of the display of the LiDAR 4 when the signs 3 (3e, 3f) are viewed from the LiDAR 4. FIGS. 5(a) and (b) correspond to the signs 3e and 3f in FIG. 4, respectively.

[0042] The markings 3 may be a combination of retroreflectors 6 that form dots and retroreflectors that form lines.

[0043] In this embodiment, the information indicated by the sign 3 is identification information for uniquely identifying the sign 3. The processing unit 5 pre-stores the identification information of the sign 3 in association with additional information. The additional information includes position information of the sign 3.

[0044] For example, the processing unit 5 has a database in its memory or storage device. The database has data in a tabular format table. Records corresponding to the rows of the table correspond to each sign 3. Columns corresponding to the columns of the table correspond to identification information and additional information. There may be multiple columns of additional information, and there should be at least a column for location information of the sign 3. The processing unit 5 uses such a database to refer to the additional information of the sign 3 having the identification information as a condition.

[0045] As a result, the processing unit 5 can acquire the position information included in the additional information corresponding to the identification information indicated by the sign 3, and can calculate the position of the vehicle 2.

[0046] As a modification of this embodiment, the information indicated by the sign 3 may not be the identification information but may be the position information of the sign 3 itself. This simplifies the processing in the processing unit 5. However, in this case, the amount of information (number of bits) of the sign 3 may become large.

[0047] As described above, according to the position detection system 1 of this embodiment, the markings 3 having retroreflectors 6 are provided on or near the tracks, so the position of the vehicle 2 can be detected at a lower cost than by providing a ground coil (see FIG. 1). Furthermore, the position detection system 1 uses laser light from the LiDAR 4 to measure the distance to the markings 3, so it can accurately detect the position of the vehicle 2. Furthermore, the position detection system 1 can detect the position of the vehicle 2 from just before the markings 3, because the LiDAR 4 emits laser light ahead of the vehicle 2.

[0048] Unlike a tachometer generator, the LiDAR 4 of the position detection system 1 is not affected by wheel slippage or spin. The position of the vehicle 2 detected by the position detection system 1 may be used to correct position information obtained using a tachometer generator. In addition, the tachometer generator may be omitted by providing signs 3 at locations where position information of the vehicle 2 is required.

[0049] By adding information other than the position information as the additional information pre-stored in the processing unit 5 of the position detection system 1, the position detection system 1 can be used for purposes other than detecting the position of the vehicle 2. An example of such a use will be described below.

[0050] The vehicles 2 are operated as a train between stations. The train may consist of one or more cars. The markings 3 are provided on the track of the station or near the track. It is desirable that the markings 3 be provided on the gauge of the track (between the left and right rails). The markings 3 may be provided on the outside of the rails of the track. The markings 3 may also be provided near the track. Near the track means within the detection range of the LiDAR 4 close to the track, for example, the longitudinal end of the station platform. The additional information includes station information related to the station in addition to the position information. Note that in the train's operating section, the markings 3 may be provided not only at stations but also between stations.

[0051] As a result, station information about stations can be obtained in addition to the position of the train itself using the position detection system 1. This station information is used, for example, for on-board ticket gate systems, automatic announcements, automatic display switching on information displays, driving assistance systems, fixed point stopping systems, etc. Examples of station information that make these possible will be described below.

[0052] For example, the station information stored in advance as additional information in the processing unit 5 includes a station name or a station number. The station number is a number assigned to a station.

[0053] This makes it possible to use the position detection system 1 to identify the station into which the train is approaching or at which the train is stopped.

[0054] Furthermore, for example, the station information stored in advance as additional information by the processing unit 5 includes a distinction between stations where the train stops and stations that the train passes through.

[0055] This makes it possible to use the position detection system 1 to prevent trains from passing through stations by mistake.

[0056] Furthermore, for example, the station information stored in advance as additional information by the processing unit 5 includes the track number of the station.

[0057] This makes it possible to identify the track number of the station where the train is entering or where the train is stopped, using the position detection system 1. Note that such track number of the station is information that cannot be determined even if a tachometer generator is used.

[0058] Furthermore, for example, the station information previously stored as additional information by the processing unit 5 includes information on target train stop positions, which is information on the positions at which the train itself should stop in the station.

[0059] This allows the brakes to be controlled using information output from the position detection system 1. By using this position detection system 1, a fixed-point stopping system can be realized at low cost.

[0060] Furthermore, for example, the station information previously stored as additional information by the processing unit 5 includes information on doors that open at stations. The door information is, for example, information on whether the doors that open at stations are on the right or left side of the train. The door information acquired by the position detection system 1 may be provided to a train crew member or used for door control.

[0061] This makes it possible to use the position detection system 1 to prevent doors that should not be opened at stations from being opened by mistake. [Example]

[0062] The position detection system 1 of the present invention was tested on an actual vehicle. A vehicle owned by a streetcar operator was used as the vehicle 2. A non-repetitive scanning pattern LiDAR was used as the LiDAR 4 of the position detection system 1. The LiDAR was installed in the driver's seat inside the streetcar. Road studs were used as the retroreflectors 6 of the markings 3. The road studs had a square pyramid shape, a base measuring 100 x 100 mm square, and a height of 18 mm. As shown in Figure 6, multiple road studs were installed on the track to form markings 3g, 3h, and 3i. Marking 3h is the road stud of marking 3g, with a greater distance in the direction of the track.

[0063] The white arrow indicates the traveling direction of the vehicle 2. The LiDAR 4 irradiates laser light in the direction of the white arrow (forward).

[0064] When the vehicle 2 was stopped, the position detection system 1 was able to accurately read the sign 3g using the LiDAR 4. When the vehicle 2 was moving, the position detection system 1 was able to accurately read the signs 3g, 3h, and 3i using the LiDAR 4. [Example]

[0065] Reflective tape with a width of 45 mm was used as the retroreflector 6 of the marking 3. As shown in Figure 7, multiple pieces of reflective tape were attached to the track to form marks 3j and 3k. The other test conditions were the same as in Example 1.

[0066] When the vehicle 2 was stopped and when it was moving, the position detection system 1 was able to accurately read the signs 3j and 3k using the LiDAR 4. [Example]

[0067] Markings 3l and 3m were constructed as the retroreflectors 6 of marking 3 by combining the road studs used in Example 1 with the reflective tape used in Example 2. Markings 3l and 3m have multiple road studs (retroreflectors 6 forming dots) in the area sandwiched between two (multiple) reflective tapes (retroreflectors 6 forming lines). Marking 3m has more road studs in the direction of the sleepers than marking 3l. All other test conditions were the same as in Example 2.

[0068] While the vehicle 2 was traveling, the position detection system 1 was able to accurately read the signs 3l and 3m using the LiDAR 4.

[0069] The present invention is not limited to the configuration of the above embodiment, and various modifications are possible within the scope of the invention. For example, the vehicle 2 is not limited to a streetcar or a regular railway vehicle. Furthermore, the arrangement pattern of the retroreflectors 6 on the sign 3 is not limited to those exemplified in Figures 2, 4, 6, and 7. [Explanation of symbols]

[0070] 1. Position detection system 3, 3a, 3b, 3c, 3d, 3e, 3f markings 3g, 3h, 3i, 3j, 3k, 3l, 3m markings 4. LiDAR 5 Processing section 6 Retroreflectors

Claims

1. A position detection system for detecting the position of a vehicle traveling on a track, comprising: Markings on the track surface or slabs or sleepers; A LiDAR and a processing unit are provided in a vehicle, the sign has a plurality of retroreflectors and indicates information by an arrangement pattern of the retroreflectors; Each of the retroreflectors constitutes a dot or a line in the marking, The retroreflectors constituting the dots have an outer shape that protrudes from the road surface, slab, or sleeper, and have a reflective surface at least on the side facing an oncoming vehicle, The LiDAR irradiates laser light ahead of the vehicle, detects the arrangement pattern by the reflected light, and measures the distance to the sign; The processing unit acquires the position information of the marking based on the information indicated by the placement pattern, and calculates the position of the vehicle from the position information of the marking and the distance to the marking.

2. A position detection system as described in Claim 1, characterized in that the retroreflective material that constitutes the dot is a road stud.

3. 2. The position detection system according to claim 1, wherein the marking has the retroreflectors forming a plurality of dots in an area sandwiched between the retroreflectors forming a plurality of lines.

4. the information indicated by the mark is identification information for uniquely identifying the mark, the processing unit stores in advance the identification information of the sign and additional information in association with each other, The position detection system according to claim 1 , wherein the additional information includes position information of the sign.

5. The vehicle is operated as a train between stations, The sign is provided at a station, The position detection system according to claim 4 , wherein the additional information further includes station information about the station.

6. The position detection system according to claim 5 , wherein the station information includes a station name or a station number.

7. The position detection system according to claim 5, wherein the station information includes a distinction between stations where the train stops and stations where the train passes through.

8. The position detection system according to claim 5 , wherein the station information includes a track number of the station.

9. The position detection system according to claim 5, wherein the station information includes information on train stop position targets.

10. The position detection system according to claim 5, wherein the station information includes information about doors that open at the station.

11. 11. The position detection system according to claim 1, wherein the arrangement pattern has redundancy for error detection or error correction.

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