Vehicle counting system

Abstract

The present disclosure is a vehicle counting system that performs: acquiring a signal measured by an optical fiber vibration measurement device to which an optical cable having a crossing section laid to cross a road or a railway is connected; calculating a vibration waveform of the crossing section using the acquired signal; and counting the number of vehicles that passed through the crossing section on the basis of the calculated number of vibration waveforms.

Description

Vehicle Counting System

[0001] This disclosure relates to traffic monitoring technology using optical fiber sensing.

[0002] A method for estimating traffic conditions on a road using a distributed acoustic sensing (DAS) device has been proposed (see, for example, Non-Patent Document 2). DAS is a technology for measuring the longitudinal vibration distribution of an optical fiber serving as a sensing probe (see, for example, Non-Patent Document 1).

[0003] In Non-Patent Document 2, an optical cable is laid along a road underground, and the vibration distribution transmitted to the optical cable is measured using DAS. In Non-Patent Documents 2 and 3, by using artificial intelligence, it is possible to derive the driving trajectory of a vehicle from the vibration distribution.

[0004] “Distributed AcousticNibration Sensing (DAS / DVS)”, AP SENSINGhttps: / / www.apsensing.com / technology / distributed-acoustic-sensing-das-dvs“NEC, NEXCO Central Japan Deliver High-Precision Traffic Monitoring System Utilizing Optical Fiber Sensing Technology”, NEC Press Release, May 24, 2022http: / / jpn.nec.com / press / 202205 / 20220524_01.html#top“Road Monitoring Using Optical Fiber Sensing”, #Deep Learning - Qiitahttps: / / qiita.com / d_ike / items / 08492b3ba5d3c83adccf

[0005] Since the number of vehicles is very important for estimating traffic conditions on a road or railway track, it is desirable that the exact number can be measured without delay. Therefore, it is desirable that the number of vehicles can be measured without using complex calculations. However, when trying to measure the number of vehicles using artificial intelligence, complex calculations are necessary (see, for example, Non-Patent Document 3).

[0006] This disclosure aims to enable the measurement of the number of vehicles in traffic conditions estimation using DAS without requiring complex calculations.

[0007] The vehicle counting system of this disclosure includes a crossing section of an optical cable laid on a road or railway track, which is laid to cross the road or railway. For example, it utilizes an optical cable laid to cross at a point on the road or track where vehicle detection is to be performed.

[0008] Specifically, the vehicle count measurement system of this disclosure comprises an optical cable, an optical fiber vibration measuring instrument for measuring vibrations of the optical cable, and a signal processing device of this disclosure for acquiring a signal from the optical fiber vibration measuring instrument.

[0009] The signal processing device of the present disclosure performs the vehicle count measurement method of the present disclosure. In the vehicle count measurement method of the present disclosure, the signal processing device acquires a signal measured by an optical fiber vibration measuring instrument to which an optical cable having a cross section laid to cross a road or railway is connected, calculates the vibration waveform of the cross section using the acquired signal, and measures the number of vehicles that have passed through the cross section based on the number of calculated vibration waveforms.

[0010] The crossing sections may be located on each road leading to the intersection. In this configuration, the signal processing device calculates the vibration waveform of the crossing sections located on each road and measures the number of vehicles in each direction of travel at the intersection based on the combination of crossing sections from which vibration waveforms have been detected.

[0011] Furthermore, the above disclosures can be combined as much as possible.

[0012] According to this disclosure, it is possible to measure the number of vehicles in traffic conditions estimation using DAS without using complex calculations.

[0013] An example of a system using DAS is shown. An example of the configuration of the vehicle count measurement system of this embodiment is shown. An example of the configuration of the vehicle count measurement system of this embodiment is shown. A waterfall diagram of vibration intensity of this embodiment is shown. An example of vibration waveform in a cross section is shown. An example of the configuration of the vehicle count measurement system of this embodiment is shown. A waterfall diagram of vibration intensity of this embodiment is shown. An example of the configuration of the vehicle count measurement system of this embodiment is shown. A waterfall diagram of vibration intensity of this embodiment is shown. An example of vibration waveform in a cross section is shown. This is an explanatory diagram of the optical cable laying configuration.

[0014] Embodiments of this disclosure will be described in detail below with reference to the drawings. However, this disclosure is not limited to the embodiments shown below. These examples are illustrative, and this disclosure can be implemented in various modified and improved forms based on the knowledge of those skilled in the art. In this specification and in the drawings, components with the same reference numerals refer to the same components.

[0015] Figure 1 shows an example of a system using a DAS. This system comprises an optical fiber vibration measuring instrument (DAS) 11 and a signal processing device 12. In this disclosure, as a preliminary step, an optical cable 13 is laid on the road. The optical cable 13 houses an optical fiber (sensing probe) that connects to the DAS 11. When estimating the traffic conditions on the road, the optical cable 13 is connected to the DAS 11, and the vibration of the optical cable 13 is measured using the DAS 11.

[0016] DAS11 can employ any device capable of measuring the vibration distribution along the longitudinal direction of an optical fiber. For example, a coherent-optical time-domain reflectometer (C-OTDR) can be used.

[0017] The signal processing device 12 is a device that analyzes the vibration distribution in the longitudinal direction of the optical cable 13 using the signal obtained from the DAS 11, and performs arbitrary calculation processing. For example, the signal processing device 12 detects and extracts the vibration of the vehicle 100 from the vibration distribution in the longitudinal direction of the optical cable 13.

[0018] The DAS 11 can measure the time variation of vibration intensity for each longitudinal section of the optical cable 13. Therefore, if the optical cable 13 is laid to cross a road, the vibration waveform of a vehicle 100 can be calculated for each lane of the road. Accordingly, in this disclosure, an optical cable 13 having a transverse section laid to cross a road is connected to the DAS 11, and the vehicle count measurement method of this disclosure is executed.

[0019] In the vehicle count measurement method of this disclosure, the signal processing device 12 acquires the signal measured by the DAS 11, calculates the vibration waveform of the crossing section using the acquired signal, and measures the number of vehicles 100 that passed through the crossing section based on the number of calculated vibration waveforms. A detailed explanation follows below.

[0020] (First Embodiment) Figure 2 shows an example of the configuration of the vehicle count measurement system of this embodiment. This figure shows the road as viewed from above. The optical cable 13 connected to the DAS 11 is laid in the longitudinal direction across the cross section S of the road to be measured. Ｎ It is equipped with.

[0021] Crossing section S Ｎ This system employs a transverse underground optical cable that is laid across the road lanes where the vehicle 100 should be detected, and whose laying condition does not change over a long period of time in an environment subject to vibrations from the vehicle 100. Under these conditions, the system of this embodiment measures the vibration of the optical cable 13 using the DAS 11.

[0022] The signal processing device 12 acquires the signal measured by the DAS 11 and uses the acquired signal to process the crossing section S Ｎ The vibration waveform is calculated. Then, the signal processing device 12 calculates the vibration waveform for the cross section S based on the number of calculated vibration waveforms. Ｎ The number of vehicles 100 that have passed through is measured. For example, the signal processing device 12 determines the vibration waveform of each vehicle 100 and outputs the number of determined vibration waveforms as the number of vehicles 100.

[0023] In this embodiment, only the vibration waveform is used in the calculation process, and complex calculations such as those used in machine learning are unnecessary. Therefore, the system of this embodiment can only perform simple analysis, and when there are two or more lanes on one side, it can be separated for each lane so that the number of vehicles can be measured and the passing time can be recorded.

[0024] As described above, the system of the present disclosure has a function of measuring the vibration distribution in the longitudinal direction of the optical fiber, and among the measured vibration distributions, for the vibration waveform in the cross-sectional section S Ｎ it has a function of calculating, and with only simple analysis, even when there are two or more lanes on one side, it can be separated for each lane and the number of vehicles can be measured.

[0025] Note that the cross-sectional section S Ｎ may be the tip of the optical cable 13 as shown in FIG. 2, or may be in the middle of the optical cable 13 as will be described later. Also, the optical cable 13 of the cross-sectional section S Ｎ may be arranged perpendicular to the longitudinal direction of the road as shown in this figure, but the effects of the present disclosure can still be obtained even if it is not arranged in such a way.

[0026] In addition, in this embodiment, an example of the traffic situation of vehicles traveling on the road is shown, but it is also applicable to the situation of trains traveling along the tracks of railways and the like. The same applies to the following embodiments.

[0027] (Second Embodiment) FIG. 3 shows a configuration example of the vehicle number measurement system of this embodiment. In this embodiment, as shown in the waterfall diagram of the vibration intensity in FIG. 4, an example is shown in which the cross-sectional sections L ＡＢ and L ＢＣ are arranged in the middle of the optical cable 13. The cross-sectional sections L ＡＢ and L ＢＣ are separated for each lane. The signal processing device 12 calculates the vibration waveform for each of the cross-sectional sections L ＡＢ and L ＢＣ , and measures the number of vehicles 100 for each of the cross-sectional sections L ＡＢ and L ＢＣ .

[0028] FIG. 5 shows an example of the vibration waveforms of the cross-sectional sections L ＡＢ and L ＢＣ . In this embodiment, the signal processing device 12 performs the cross-sectional section LＡＢ and L ＢＣ To calculate the vibration waveform for each section L, ＡＢ Waveform F ＡＢ and crossing section L ＢＣ Waveform F ＢＣ These can be obtained individually. For this reason, the signal processing device 12 processes the waveform F ＡＢ The vibration intensity in the transverse section L ＡＢ Threshold H Ａ Time t exceeding ＡＢ The number of times is measured, and the waveform F ＢＣ The vibration intensity in the transverse section L ＢＣ Threshold H B Time t exceeding ＢＣ And the number of times is measured.

[0029] Here, one waveform F ＡＢ Multiple peaks may appear, and multiple peaks may exceed the threshold. In such cases, the crossing section L can be used to measure each vehicle 100 individually. ＡＢ After the measurement interval ΔT, which is determined by the driving speed, the threshold H Ａ A comparison with this may also be made.

[0030] Thus, in this embodiment, the cross section L ＡＢ and L ＢＣ Unlike conventional methods, the function of separating and calculating vibration waveforms for each lane allows for the measurement of the number of vehicles and their passing times for each lane, even when there are vehicles 100 traveling in the same direction parallel to multiple lanes.

[0031] (Third Embodiment) Figure 6 shows an example of the configuration of the vehicle count measurement system of this embodiment. In this embodiment, in order to make it easier to separate the vibration waveform for each lane, the cross section L is as shown in the vibration intensity waterfall diagram in Figure 7. ＡＢ and L ＢＣ Remaining length L Ｅ It is equipped with.

[0032] In this embodiment, there is an excess length L at point B. Ｅ An example is shown in which there is an extra length L between either point A and B, or between point B and C, or both. Ｅ It may be provided with the following: Excess length L Ｅ By providing this, it becomes possible to apply DAS11 with a spatial resolution worse than that of the lane width, and the cross section LＡＢ and L ＢＣ Even if the device is far from DAS11, it becomes possible to calculate vibration waveforms with high sensitivity (relatively speaking, compared to DAS11 with a high spatial resolution setting).

[0033] (Fourth Embodiment) Figure 8 shows an example of the configuration of the vehicle count measurement system of this embodiment. In this embodiment, an example of laying optical cables 13 near an intersection is shown. In Figure 8, as an example, at an intersection 85 of a single-lane road, crossing sections L are laid on each road connected to the intersection. ＡＢ , L ＢＣ , L ＣＤ , L ＤＡ This shows an example of where they are arranged.

[0034] In this embodiment, the signal processing device 12 controls each cross section L ＡＢ , L ＢＣ , L ＣＤ , L ＤＡ The vibration waveform is calculated, and the number of vehicles 100 in each direction of travel at intersection 85 is measured based on the combination of crossing sections in which the vibration waveform was detected.

[0035] For example, as shown in Figure 8, when a vehicle 100 that entered intersection 85 from road 81 turns right onto road 84, as shown in the vibration intensity waterfall diagram in Figure 9, the crossing section L ＡＢ Following that is the cross section L ＤＡ Vibration detected in cross section L ＢＣ and L ＣＤ Therefore, no vibration is detected.

[0036] Figure 10 shows the cross section L. ＡＢ and L ＤＡ An example of a vibration waveform is shown. In this embodiment, the transverse section L ＡＢ , L ＢＣ , L ＣＤ , L ＤＡ To calculate the vibration waveform for each section L, ＡＢ Vibration waveform F ＡＢ After that, cross section L ＤＡ Vibration waveform F ＤＡ You can obtain this.

[0037] Therefore, the crossing section L ＡＢ Following that is the cross section L ＤＡThe vibration waveform is detected, and the crossing section L ＢＣ and L ＣＤ When the vibration waveform is not detected, the signal processing device 12 determines that the vehicle 100 has turned right from the road 81 to the road 84. In this embodiment, an example of entering from the road 81 and turning right to the road 84 is shown, but the present disclosure is not limited to this.

[0038] For example, if the traveling direction of the vehicle 100 is a left turn, the vibration waveform is detected after the crossing section L ＡＢ and then after the crossing section L ＢＣ When the vibration waveform is detected, the signal processing device 12 determines that the vehicle 100 has turned left from the road 81 to the road 84 when the vibration waveform is not detected in the crossing section L ＡＢ and then after the crossing section L ＢＣ When the vibration waveform is detected, and the vibration waveform is not detected in the crossing section L ＤＡ and L ＣＤ

[0039] For example, if the traveling direction of the vehicle 100 is straight ahead, the vibration waveform is detected after the crossing section L ＡＢ and then after the crossing section L ＣＤ When the vibration waveform is detected, the signal processing device 12 determines that the vehicle 100 has traveled straight from the road 81 to the road 83 when the vibration waveform is not detected in the crossing section L ＡＢ and then after the crossing section L ＣＤ When the vibration waveform is detected, and the vibration waveform is not detected in the crossing section L ＤＡ and L ＢＣ

[0040] Thus, the vibration waveform is detected in the crossing section corresponding to the destination of the vehicle 100 among the crossing sections L ＡＢ L ＢＣ L ＣＤ L ＤＡ In this embodiment, an example of entering from the road 81 to the intersection 85 is shown, but when entering from the roads 82, 83, and 84 to the intersection 85, the determination can be made by the same method.

[0041] The system of this embodiment can determine the passing direction and the number of vehicles 100 passing through the intersection 85 based on the vibration waveforms of the crossing sections L ＡＢ L ＢＣ L ＣＤ L ＤＡ respectively.

[0042] Furthermore, since the magnitude of vibrations measured by DAS11 differs between large vehicles such as trucks and passenger cars, it becomes possible to determine the size of the vehicle 100. Therefore, according to the system of this disclosure, it becomes possible to measure, 24 hours a day, 365 days a year, how many vehicles 100 of what size are passing through intersection 85 and in which direction, at what time of day, using the vibrations measurable by DAS11. Consequently, the traffic volume at small intersections used as shortcuts can be monitored at low cost and utilized in road planning.

[0043] Furthermore, although this embodiment shows an example of laying a single optical cable 13 in a single continuous line, the disclosure is not limited to this. For example, different optical cables 13 may be laid for each road connected to an intersection, and the vibration of the optical cable 13 may be measured using a different DAS 11 for each optical cable 13.

[0044] (Fifth Embodiment) The laying of the optical cable 13 in this disclosure can be carried out in any manner that can detect road vibrations. For example, as shown in Figure 2, it may be underground under the road, or it may be realized by road surface wiring optical fiber cable design technology.

[0045] In particular, this disclosure describes laying the optical cable 13 across a road. Therefore, as shown in Figure 11(a), a groove 14 may be provided on the road surface, and the optical cable 13 may be housed in the groove 14. Alternatively, as shown in Figure 11(b), a laying layer 15 may be provided on the road surface, and the optical cable 13 may be housed in a cutout in the laying layer 15. The laying layer 15 can be made of any means capable of fixing the optical cable 13 to the road, for example, resin can be used.

[0046] The grooves 14 and the laying layer 15 may be equipped with a mechanism that generates specific vibrations without hindering the movement of the vehicle 100. For example, vibrations may be reflected within the grooves 14, or irregularities may be provided on the surface of the laying layer 15.

[0047] Furthermore, the system may be equipped with a mechanism to amplify the vibrations generated when the vehicle 100 passes. For example, a speed bump (a structure that raises a part of the road) may be placed directly in front of the optical cable 13. This makes the vibration waveform when the vehicle 100 passes clearer, and also makes it possible to measure the vibrations of slow-moving vehicles and small vehicles such as motorcycles.

[0048] Furthermore, the groove 14 and the laying layer 15 do not need to be present along the entire length of the optical cable 13; when laid along the longitudinal direction of the road, they are buried underground, and the cross section S Ｎ It is possible to provide a groove 14 and a laying layer 15.

[0049] (Other Embodiments) The signal processing device 12 of the present invention can also be realized by a computer and a program, and the program can be recorded on a recording medium or provided via a network. The program of this disclosure is a program that causes a computer to realize each of the functions provided in the signal processing device 12 according to this disclosure, and is a program that causes a computer to execute each of the procedures provided in the method executed by the signal processing device 12 according to this disclosure.

[0050] 11: DAS 12: Signal processing device 13: Optical cable 14: Groove 15: Laying layer 81, 82, 83, 84: Road 85: Intersection 100: Vehicle

Claims

1. A signal processing device that acquires signals measured by an optical fiber vibration measuring instrument to which an optical cable having a cross section laid to cross a road or railway is connected, calculates the vibration waveform of the cross section using the acquired signals, and measures the number of vehicles that have passed through the cross section based on the number of calculated vibration waveforms.

2. The signal processing device according to claim 1, wherein the crossing sections are arranged on each road leading to the intersection, the vibration waveform of the crossing sections arranged on each road is calculated, and the number of vehicles in each direction of travel at the intersection is measured based on the combination of the crossing sections from which vibration waveforms have been detected.

3. A vehicle counting system comprising: an optical cable having a cross section laid to cross a road or railway; an optical fiber vibration measuring instrument for measuring vibrations of the optical cable; and a signal processing device according to claim 1 or 2 for acquiring a signal from the optical fiber vibration measuring instrument.

4. A method for measuring the number of vehicles, comprising: a signal processing device acquiring a signal measured by an optical fiber vibration measuring instrument to which an optical cable having a cross section laid to cross a road or railway is connected; the signal processing device using the acquired signal to calculate the vibration waveform of the cross section; and the signal processing device measuring the number of vehicles that have passed through the cross section based on the number of vibration waveforms calculated.

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