Measuring system

Abstract

To improve an accuracy of counting a rotating axle contained in a vehicle.SOLUTION: A measuring system is a sensor which generates first speed information by measuring a speed of a vehicle body of a vehicle traveling on a road, the measuring system comprising: a sensor which may be a camera sensor, a radar sensor, or an ultrasonic sensor; an FMCW-LiDAR sensor for measuring a speed of a wheel and generating second speed information based on reflection light generated by irradiating the wheel of the vehicle with a beam; and a processing unit for counting a number of rotating axle of the vehicle and generating axle number information based on the first speed information and the second speed information.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present disclosure relates to measurement systems. [Background technology]

[0002] Conventionally, devices have been proposed that use radar or laser to measure the distance to an object or the speed of the object. For example, a distance and speed measuring device using the FMCW (Frequency Modulated Continuous Wave) method has been developed. The FMCW measuring device transmits electromagnetic waves whose frequency is modulated at a constant cycle, and can measure the distance and speed based on the difference in frequency between the transmitted wave and the reflected wave. When the electromagnetic wave is light such as visible light or infrared light, the FMCW measuring device is called an FMCW-LiDAR (Light Detection and Ranging) or laser radar. The FMCW-LiDAR splits light whose frequency is modulated at a constant cycle into output light and reference light, generates interference light between the reflected light generated by the output light being reflected by an object and the reference light, and detects the interference light. Based on the frequency of the interference light, the distance to the object and the speed of the object can be calculated.

[0003] Patent documents 1 and 2 disclose measuring distance and speed using a sensing device based on the FMCW method. Patent document 3 discloses a method of multiplexing multiple output signals on one detector using multiple delay lines in an FMCW laser radar that emits multiple light beams. Patent document 4 discloses a method of counting rotating axles by measuring the rotation speed of the wheels of a traveling vehicle using an FMCW LiDAR. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-135446 A [Patent Document 2] JP 2011-027457 A [Patent Document 3] JP 2015-111160 A [Patent Document 4] JP 2022-139736 A Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure provides sensing techniques for improving the accuracy of counting rotating axles in a moving vehicle. [Means for solving the problem]

[0006] A measurement system according to one embodiment of the present disclosure includes a sensor that measures the speed of a body of a vehicle traveling on a road and generates first speed information, the sensor being a camera sensor, a radar sensor, or an ultrasonic sensor; an FMCW-LiDAR sensor that measures the speed of the wheels of the vehicle based on reflected light produced by irradiating the wheels with a beam and generates second speed information; and a processing device that counts the rotating axles of the vehicle based on the first speed information and the second speed information and generates axle number information.

[0007] A comprehensive or specific aspect of the present disclosure may be realized by a system, an apparatus, a method, an integrated circuit, a computer program, or a recording medium such as a computer-readable recording disk, or may be realized by any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium. The computer-readable recording medium may include a volatile recording medium, or may include a non-volatile recording medium such as a CD-ROM (Compact Disc - Read Only Memory). The apparatus may be composed of one or more devices. When the apparatus is composed of two or more devices, the two or more devices may be arranged in one device, or may be arranged separately in two or more separate devices. In this specification and the claims, "apparatus" may mean not only one device, but also a system consisting of multiple devices. Effect of the Invention

[0008] According to one aspect of the present disclosure, it is possible to improve the accuracy of counting rotating axles included in a moving vehicle. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram showing a schematic configuration example of a sensor using FMCW LiDAR technology. [Figure 2A] FIG. 2A is a diagram showing a schematic diagram of changes in the frequency of the reference light and the reflected light over time when the vehicle is stationary. [Figure 2B] FIG. 2B is a diagram showing a schematic diagram of changes in the frequency of the reference light and the reflected light over time when a vehicle is approaching the sensor. [Figure 3A] FIG. 3A is a side view that diagrammatically illustrates an example of a vehicle. [Figure 3B] FIG. 3B is a top view that diagrammatically illustrates an example of a vehicle. [Figure 3C] FIG. 3C is a front view that diagrammatically illustrates an example of a vehicle. [Figure 3D] FIG. 3D is a close-up view of one of the wheels of the vehicle shown in FIG. 3A. [Figure 4] FIG. 4 is a diagram illustrating an example of changes in the measured speed and the measured distance over time. [Diagram 5] FIG. 5 is a diagram illustrating a schematic configuration example of a sensing system according to the first exemplary embodiment of the present disclosure. [Figure 6] FIG. 6 is a diagram illustrating an example of the configuration of a sensing system. [Figure 7] FIG. 7 is a diagram showing an example of the arrangement of the camera and the emission unit. [Figure 8A] FIG. 8A shows images of a vehicle in the nth and n+1th frames. [Figure 8B] FIG. 8B is a diagram in which feature points of the vehicle are associated with each other in the nth and (n+1)th frames. [Figure 8C]FIG. 8C is a diagram showing the amount of movement of the vehicle on the image calculated from the coordinates of each feature point. [Figure 8D] FIG. 8D is a diagram for explaining a method for determining the speed of a vehicle based on the distance to the vehicle. [Figure 9] FIG. 9 is a graph showing an example of the vehicle speed and the wheel rotation speed measured by the sensing system. [Figure 10A] FIG. 10A is a diagram showing a schematic example of the relationship between the position of the shooting area of ​​a camera on a vehicle, the position of the irradiation point of a beam, and the timing at which the speed at the irradiation point is measured. [Figure 10B] FIG. 10B is a diagram showing another example of the relationship between the position of the shooting area of ​​the camera on the vehicle, the position of the irradiation point of the beam, and the timing at which the speed at the irradiation point is measured. [Figure 11] FIG. 11 is a flowchart showing an example of the operation of the processing device in the sensing system. [Figure 12] FIG. 12 is a flowchart showing the details of the operation of determining the presence or absence of a vehicle in step S1020. [Figure 13] FIG. 13 is a flowchart showing the details of the operation of determining whether or not the rotation speed of the wheel has been measured in step S1060. [Figure 14] FIG. 14 is a flowchart showing details of the operation in step S1061. [Figure 15] FIG. 15 is a flowchart showing details of the operation of step S1070. [Figure 16] FIG. 16 shows an example of the change over time in the speed measured when the vehicle is stopped during measurement of the rotational speed of the wheels. [Figure 17A] FIG. 17A is a diagram for explaining the arrangement conditions of an emission section in an FMCW-LiDAR sensor. [Figure 17B] FIG. 17B is a diagram for explaining the arrangement conditions of the emission part in the FMCW-LiDAR sensor. [Figure 17C]FIG. 17C is a diagram for explaining the arrangement conditions of the emission part in the FMCW-LiDAR sensor. [Figure 17D] FIG. 17D is a diagram for explaining the arrangement conditions of the emission part in the FMCW-LiDAR sensor. [Figure 17E] FIG. 17E is a diagram for explaining the arrangement conditions of the emission part in the FMCW-LiDAR sensor. [Figure 18A] FIG. 18A is a diagram showing a schematic example of a change over time in the measured speed of a vehicle having a gap. [Figure 18B] FIG. 18B is a diagram showing a schematic example of a change over time in the measured speed of a vehicle with low reflectivity. [Figure 19A] FIG. 19A is a perspective view showing an example of the arrangement of the camera and the emitter in the ETC. [Figure 19B] FIG. 19B is a front view showing an example of the arrangement of the camera and the emitter in the ETC. [Figure 20A] FIG. 20A is a perspective view showing another example of the arrangement of the camera and the emission unit. [Figure 20B] FIG. 20B is a front view showing another example of the arrangement of the camera and the emission unit. [Figure 21] FIG. 21 is a diagram illustrating another configuration example of the sensing system. [Figure 22] FIG. 22 is a diagram showing an example of the arrangement of a radar device and an emitter. [Figure 23] FIG. 23 is a diagram showing yet another configuration example of the sensing system. In FIG. [Figure 24] FIG. 24 is a diagram showing an example of the arrangement of an ultrasonic device and an emitter. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] In this disclosure, all or part of a circuit, unit, device, member or part, or all or part of a functional block in a block diagram may be implemented by one or more electronic circuits including, for example, a semiconductor device, a semiconductor integrated circuit (IC), or an LSI (large scale integration). The LSI or IC may be integrated into one chip, or may be configured by combining multiple chips. For example, functional blocks other than memory elements may be integrated into one chip. Here, although it is called an LSI or an IC, the name may change depending on the degree of integration, and it may be called a system LSI, a VLSI (very large scale integration), or an ULSI (ultra large scale integration). A field programmable gate array (FPGA), which is programmed after the manufacture of the LSI, or a reconfigurable logic device (RLD), which can reconfigure the connection relationship inside the LSI or set up the circuit partition inside the LSI, can also be used for the same purpose.

[0011] Furthermore, all or part of the functions or operations of a circuit, unit, device, member, or section can be executed by software processing. In this case, the software is recorded in one or more non-transitory recording media such as ROMs, optical disks, hard disk drives, etc., and when the software is executed by a processor, the functions specified in the software are executed by the processor and peripheral devices. The system or device may include one or more non-transitory recording media on which the software is recorded, a processor, and necessary hardware devices, such as interfaces.

[0012] In this disclosure, "light" refers to electromagnetic waves including not only visible light (wavelength of about 400 nm to about 700 nm), but also ultraviolet light (wavelength of about 10 nm to about 400 nm) and infrared light (wavelength of about 700 nm to about 1 mm).

[0013] Hereinafter, exemplary embodiments of the present disclosure will be described. Note that the embodiments described below are all comprehensive or specific examples. The numerical values, shapes, components, arrangement and connection forms of components, steps, order of steps, etc. shown in the following embodiments are merely examples and are not intended to limit the present disclosure. In addition, among the components in the following embodiments, components that are not described in the independent claims showing the highest concept are described as optional components. In addition, each figure is a schematic diagram and is not necessarily illustrated strictly. Furthermore, in each figure, substantially the same components are given the same reference numerals, and duplicated descriptions may be omitted or simplified.

[0014] <Findings discovered by the inventors> The ETC (Electronic Toll Collection System) is a system for paying tolls on toll roads such as expressways without having to stop the vehicle at the toll booth. There are several vehicle type classifications for tolls, for example, according to the size of the vehicle and the number of axles (or the number of wheels that rotate or touch the ground). Users pay the toll by setting the information corresponding to their vehicle type classification in the on-board unit.

[0015] Tolls may vary depending on the number of rotating axles. Current ETC systems use a footplate-shaped axle detection sensor to count the number of rotating axles based on the number of wheels that come into contact with the sensor. In recent years, the number of large trucks equipped with a function called lift axles has increased. Large trucks with three or more axles can use the lift axle function to lift some axles and lift the wheels attached to those axles. This increases the pressure on other wheels when the load is light, preventing the large truck from slipping. Large trucks that use the lift axle function have axles that do not rotate while driving. For this reason, ETC is required to accurately count the number of rotating axles among the multiple axles on a vehicle.

[0016] The inventors have devised a method for identifying rotating axles of a moving object in a non-contact manner using FMCW LiDAR technology, and disclosed it in Patent Document 4. In the method described in Patent Document 4, a light beam is obliquely irradiated onto the side of a wheel to measure the rotation speed of the wheel, and the number of rotating axles can be counted based on the measurement result.

[0017] In this disclosure, we devise a method for more accurately counting the number of rotating axles, even when the vehicle speed (hereinafter sometimes referred to as "traveling speed" or "vehicle speed") changes as the vehicle accelerates or decelerates during measurement. When the vehicle accelerates or decelerates during measurement, the measured speed of the rotating wheels changes over time in a manner that differs from the time change when the vehicle speed is constant, making it difficult to distinguish the sections of each wheel. For this reason, a method is required that can correctly acquire speed information due to wheel rotation and accurately count the axles, even when speed changes occur due to vehicle acceleration or deceleration.

[0018] Therefore, in the embodiment of the present disclosure described below, a method is proposed for generating wheel rotation speed information that is free from the influence of vehicle acceleration and deceleration by acquiring information on the vehicle's traveling speed by another sensor in addition to the wheel rotation speed information using FMCW LiDAR technology. The other sensor is a camera sensor, a radar sensor, or an ultrasonic sensor. This method makes it possible to measure the wheel rotation speed with high accuracy and to accurately count the number of axles in a vehicle.

[0019] <How to identify a spinning wheel> Before describing the details of the embodiments of the present disclosure, an example of a method for identifying a rotating wheel of a vehicle in a non-contact manner using FMCW LiDAR technology will be described. The method described below is similar to the method disclosed by the inventors in Patent Document 4. The disclosure of Patent Document 4 is incorporated herein by reference in its entirety.

[0020] FIG. 1 is a block diagram showing a schematic configuration example of a sensor 110 using FMCW LiDAR technology, i.e., FMCW-LiDAR technology. FIG. 1 shows a vehicle 10 to be measured. The vehicle 10 shown in FIG. 1 is a large truck including a body 12 having five axles and ten wheels 14 attached to the five axles. The wheels 14 include metal wheels and rubber tires attached to the wheels. The type of vehicle 10 is not particularly limited, and may be any vehicle having wheels, such as a regular car, a motorcycle, or a light truck.

[0021] The sensor 110 shown in Fig. 1 includes a light source 20, an interference optical system 30, a photodetector 40, a beam shaper 50, a processing circuit 60, and a memory 62. The open arrow shown in Fig. 1 indicates the traveling direction of the vehicle 10. The thick arrow shown in Fig. 1 indicates the flow of light. The thin arrow shown in Fig. 1 indicates the flow of a signal. The sensor 110 may be installed, for example, at the side of the lane in which the vehicle 10 travels, or at a gate above the lane.

[0022] The light source 20 can change the frequency in response to control from the processing circuit 60. The light source 20 emits a laser light 20L0. The frequency can be modulated at a constant time period, for example, a triangular wave or a sawtooth wave. This period is called a modulation period. The frequency modulation period can be, for example, 1 μsec or more and 10 ms or less. The frequency modulation amplitude can be, for example, 100 MHz or more and 1 THz or less. The wavelength of the laser light can be included in the near-infrared wavelength range, for example, 700 nm or more and 2000 nm or less. Since the amount of near-infrared light in sunlight is less than the amount of visible light, the effect of sunlight as noise can be reduced by using near-infrared light as the laser light 20L0. Alternatively, the wavelength of the laser light 20L0 may be included in the visible light wavelength range of 400 nm or more and 700 nm or less, or may be included in the ultraviolet light wavelength range.

[0023] The interference optical system 30 includes a first fiber splitter 32, a second fiber splitter 34, and an optical circulator 36. The first fiber splitter 32 separates the laser light 20L0 emitted from the light source 20 into a reference light 20L1 and an output light 20L2. The first fiber splitter 32 inputs the reference light 20L1 to the second fiber splitter 34, and inputs the output light 20L2 to the optical circulator 36. The optical circulator 36 inputs the output light 20L2 to the beam shaper 50. The optical circulator 36 inputs the reflected light 20L3 generated by irradiating the side of the vehicle 10 with the output light 20L2 to the second fiber splitter 34. The second fiber splitter 34 inputs the interference light 20L4, which is obtained by superimposing and interfering with the reference light 20L1 and the reflected light 20L3, to the photodetector 40.

[0024] The photodetector 40 detects the interference light 20L4. The photodetector 40 includes one or more photodetection elements. The photodetection elements output an electrical signal according to the intensity of the detected light.

[0025] The beam shaper 50 shapes the irradiation spot of the output light 20L2 and emits the output light 20L2 toward the vehicle 10. The side of the vehicle 10 is irradiated with the output light 20L2 output from the beam shaper 50. The side of the vehicle 10 includes the side of the body 12 and the side of the wheels 14. Even if the direction of the output light 20L2 is fixed, the side of the vehicle 10 is scanned across by the output light 20L2 as the vehicle 10 travels. The beam shaper 50 inputs the reflected light 20L3 generated at the side of the vehicle 10 to the interference optical system 30. The beam shaper 50 is located on the optical path of the output light 20L2 and the reflected light 20L3 between the interference optical system 30 and the vehicle 10.

[0026] The beam shaper 50 may include, for example, a collimating lens 52 that reduces the spread of the output light 20L2. The collimating lens 52 adjusts, for example, the irradiation spot diameter of the output light 20L2 to be smaller than the diameter of the wheel 14 of the vehicle 10. The output light 20L2 having such an irradiation spot diameter can separately irradiate the vehicle body 12 and the wheel 14 of the vehicle 10. The collimating lens 52 may adjust the irradiation spot diameter of the output light 20L2 to be smaller than the cross-sectional height of the tire. The cross-sectional height is equal to half the value obtained by subtracting the inner diameter of the tire from the outer diameter of the tire. The output light 20L2 having such an irradiation spot diameter can irradiate only the tire of the wheel 14 with the output light 20L2. A part of the wheel of the wheel 14 may be hollowed out from the viewpoint of design. In such a case, the sensor 110 may be configured to irradiate only the tire of the wheel 14 with the output light 20L2. The collimator lens 52 adjusts the irradiation spot diameter of the output light 20L2 so that it is smaller than the shortest distance between two adjacent wheels 14. The output light 20L2 having such an irradiation spot diameter can measure the rotation speeds of the multiple wheels 14 individually.

[0027] The processing circuit 60 controls the operation of the light source 20 and the photodetector 40. The processing circuit 60 processes the signal output from the photodetector 40 using FMCW-LiDAR technology. The processing circuit 60 can count the number of rotating axles in the vehicle 10 by processing the signal.

[0028] The computer program executed by the processing circuit 60 is stored in a memory 62 such as a ROM or a RAM (Random Access Memory). The processing circuit 60 and the memory 62 may be integrated on one circuit board or may be provided on separate circuit boards. The functions of the processing circuit 60 may be distributed among multiple circuits. A part or the whole of the processing circuit 60 may be installed in a remote location away from other components in the sensor 110, and may control the operations of the light source 20 and the photodetector 40 and process the signal output from the photodetector 40 via a wired or wireless communication network.

[0029] Next, the principle of distance and speed measurement using FMCW-LiDAR technology will be briefly described with reference to Figures 2A and 2B. FMCW-LiDAR technology makes it possible to realize a measurement device that is highly vibration-resistant, has a wide dynamic range for distance, and has high spatial resolution, and is capable of measuring the distance and speed of a moving object.

[0030] FIG. 2A is a diagram showing a schematic diagram of the time change of the frequency of the reference light 20L1 and the reflected light 20L3 when the vehicle 10 is stationary. The solid line represents the reference light, and the dashed line represents the reflected light. The frequency of the reference light 20L1 shown in FIG. 2A repeats a time change of a triangular wave. That is, the frequency of the reference light 20L1 increases linearly during one period, and then decreases linearly by the amount of increase. The frequency of the reflected light 20L3 is shifted along the time axis by the time it takes for the output light 20L2 to be emitted from the sensor 110, reflected by the vehicle 10, and returned as the reflected light 20L3, compared to the frequency of the reference light 20L1. As a result, the interference light 20L4, which is the result of the superposition and interference of the reference light 20L1 and the reflected light 20L3, has a frequency corresponding to the difference between the frequency of the reflected light 20L3 and the frequency of the reference light 20L1. The double-headed arrow shown in FIG. 2A represents the difference between the two frequencies. The photodetector 40 outputs an electrical signal indicative of the intensity of the interference light 20L4. This signal is called a beat signal. The frequency of the beat signal, i.e. the beat frequency, is equal to the difference of the above frequencies. From the beat frequency, the processing circuit 60 can generate data relating to the distance from the sensor 110 to the vehicle 10.

[0031] FIG. 2B is a diagram showing a schematic diagram of the change in frequency of the reference light 20L1 and the reflected light 20L3 over time when the vehicle 10 is approaching the sensor 110. When the vehicle 10 is approaching, the frequency of the reflected light 20L3 is shifted in an increasing direction along the frequency axis due to the Doppler shift, compared to when the vehicle 10 is stationary. The amount of shift in the frequency of the reflected light 20L3 depends on the component of the velocity vector of the irradiated part of the vehicle 10 projected in the direction of the reflected light 20L3. The beat frequency differs between the up-chirp period in which the frequencies of the reference light 20L1 and the reflected light 20L3 increase linearly and the down-chirp period in which they decrease linearly. In the example shown in FIG. 2B, the beat frequency in the down-chirp period in which the frequencies of both decrease linearly is higher than the beat frequency in the up-chirp period in which the frequencies of both increase linearly. Based on the difference in the beat frequency, the processing circuit 60 can calculate the component of the velocity of the irradiated point on the vehicle 10 in the direction toward the sensor 110.

[0032] Next, an example of how a moving vehicle 10 is illuminated with output light 20L2 will be described with reference to Figures 3A to 3D. Figures 3A, 3B, and 3C are respectively a side view, a top view, and a front view that typically show an example of the vehicle 10. Figure 3D is an enlarged view of one of the wheels 14 of the vehicle 10 shown in Figure 3A. Of the wheels 14 shown in Figure 3D, the inner circle represents the wheel 14a, and the outer ring represents the tire 14b.

[0033] 3A to 3D, for ease of explanation, an X-axis, a Y-axis, and a Z-axis that are orthogonal to each other are shown. The direction opposite to the traveling direction of the vehicle 10 is the +X direction, the direction perpendicular to the road surface and away from the road surface is the +Y direction, and the direction to the left in the traveling direction is the +Z direction. Note that this coordinate system is introduced for convenience of explanation, and the positions and attitudes of the vehicle 10 and the sensor 110 are not limited by this coordinate system.

[0034] The white arrows shown in Fig. 3A and Fig. 3B represent the traveling direction of the vehicle 10. The thick arrows shown in Fig. 3A represent the position and direction in which the traveling vehicle 10 is scanned by the output light 20L2. Of the two thick arrows shown in Fig. 3B and Fig. 3C, the arrow from the sensor 110 toward the vehicle 10 represents the output light 20L2, and the arrow from the vehicle 10 toward the sensor 110 represents the reflected light 20L3. The angle φ shown in Fig. 3B represents the angle between the output light 20L2 and the YZ plane perpendicular to the traveling direction of the vehicle 10. This angle is equal to the angle between the traveling direction of the output light 20L2 and the direction in which the traveling direction of the output light 20L2 is projected onto the YZ plane. The angle θ shown in Fig. 3C represents the angle between the output light 20L2 and the XZ plane parallel to the road surface. This angle is equal to the angle between the traveling direction of output light 20L2 and the direction of the traveling direction of output light 20L2 projected onto the XZ plane. The white arrow shown in FIG.

[0035] The angles φ and θ can have not only positive values ​​but also negative values. When the output light 20L2 is emitted obliquely from the front toward the side of the vehicle 10, the angle φ is positive. Conversely, when the output light 20L2 is emitted obliquely from the rear toward the side of the vehicle 10, the angle φ is negative. Also, when the output light 20L2 is emitted obliquely from above toward the side of the vehicle 10, the angle θ is positive. Conversely, when the output light 20L2 is emitted obliquely from below toward the side of the vehicle 10, the angle θ is negative.

[0036] If the absolute value of the traveling speed of the vehicle 10 is V, the traveling speed vector of the vehicle 10 is expressed as (-V, 0, 0). In the example shown in FIG. 3D, the maximum radius of the wheel 14 is R, the straight-line distance from the center of the wheel 14 to the position P is r, and the angle by which the straight line rotates from the X-axis is A. The X and Y components of the position P in the XY coordinate system with the center of the wheel 14 as the origin are expressed as x=r×cosA and y=r×sinA, respectively. Since the absolute value of the rotation speed of the outermost circumference of the wheel 14 is equal to the absolute value V of the traveling speed, the absolute value of the rotation speed of the wheel 14 at the position P is V×r / R. The rotation speed vector of the position P is expressed as (-V×r / R×sinA,V×r / R×cosA,0)=(-(y / R)V,(x / R)V,0).

[0037] The velocity vector V1 of the vehicle body 12 or the non-rotating wheels 14 is equal to the road velocity vector and is expressed by the following equation (1).

number

[0038] The velocity vector V2 of the rotating wheel 14 is a composite velocity vector of the running velocity vector and the rotational velocity vector, and is expressed by the following equation (2).

number

[0039] On the other hand, a unit vector N parallel to the direction of the reflected light 20L3 is expressed by the following formula (3).

number

[0040] The X component on the right side of equation (3) can be derived by projecting unit vector N onto the X axis in the example shown in Fig. 3B. The Y component on the right side of equation (3) can be derived by projecting unit vector N onto the Y axis in the example shown in Fig. 3C. The Z component on the right side of equation (3) can be derived because the magnitude of unit vector N is 1 and it is a positive component.

[0041] The speed measured by the sensor 110 is a component obtained by projecting a speed vector in the illuminated portion of the vehicle 10 in the direction of the reflected light 20L3. That is, the measured speed is obtained by the inner product of the speed vector in that portion of the vehicle 10 and the unit vector N.

[0042] When output light 20L2 is emitted toward vehicle body 12 or non-rotating wheels 14, measured velocity v1 is obtained by the inner product of velocity vector V1 and unit vector N, and is expressed by the following equation (4).

number

[0043] Since the angle φ is known, when the angle φ≠0°, the traveling speed V of the vehicle 10 can be calculated by dividing the measured speed v1 by sin φ.

[0044] On the other hand, when the output light 20L2 is emitted toward the rotating wheel 14, the measured velocity v2 is obtained by the inner product of the velocity vector V2 and the unit vector N, and is expressed by the following equation (5).

number

[0045] The measured speed v2 is the measured speed v1 plus the first term on the right hand side due to the rotation speed. The first term depends on the X and Y components of the position P.

[0046] When the emission angles of output light 20L2 are θ=0° and φ=0°, measurement speeds v1 and v2 are zero. If at least one of the emission angles θ and φ of output light 20L2 is not zero, measurement speeds v1 and v2 may differ from each other. If both emission angles θ and φ of output light 20L2 are not zero, the absolute value of the difference between measurement speeds v1 and v2 may be larger than when only one of the emission angles θ and φ is not zero.

[0047] Next, an example of the change over time in the measured speed and the measured distance will be described with reference to FIG. 4. FIG. 4 is a diagram that shows an example of the change over time in the measured speed and the measured distance. The dashed lines in FIG. 4 represent the front and rear ends of the vehicle 10. The dashed lines in FIG. 4 represent both ends of a local gap located on the scanning line of the output light 20L2 when the vehicle 10 is viewed from the side. In this specification, the local gap in the vehicle 10 is referred to as a "gap". The dashed lines in FIG. 4 represent both ends of the part of the wheel 14 that is scanned by the output light 20L2. In the vehicle 10 shown in FIG. 4, the fourth axle from the front among the five axles is raised by the lift axle function. Therefore, the wheel 14 attached to the fourth axle is floating and does not rotate during traveling.

[0048] 4, the emission angle of the output light 20L2 is θ>0° and φ=0°, and the output light 20L2 passes near the center of the wheel 14. The output light 20L2 intersects the road surface obliquely and perpendicularly to the traveling direction of the vehicle 10.

[0049] The measured speed shown in FIG. 4 is zero for the vehicle body 12 and the fourth non-rotating wheel 14 from the front, and increases linearly from negative to positive for the wheels 14 other than the fourth. The change in the measured speed over time can be explained by equations (4) and (5). In this example, φ=0°, so from equation (4), the measured speed of the vehicle body 12 and the non-rotating wheels 14 is zero. From equation (5), the measured speed of the rotating wheel 14 is V(x / R)sinθ. In the example shown in FIG. 4, x / R increases linearly from -1 to 1 over time. The rotation speed of the front part of the wheel 14 is measured as a negative value, and the rotation speed of the rear part is measured as a positive value. The rotation speed of the wheel 14 changes from a minimum speed -Vsinθ to a maximum speed Vsinθ. There is a clear difference between the measured speed of the rotating wheel 14 and the measured speed of the vehicle body 12 or the non-rotating wheel 14. Therefore, based on the difference between these measured speeds, the rotating wheels can be detected and the number of rotating wheels can be counted.

[0050] The measured distance shown in Fig. 4 represents the distance from the sensor 110 to the vehicle 10 when the vehicle 10 is illuminated with the output light 20L2. When the vehicle 10 is not illuminated with the output light 20L2, the measured distance represents the distance from the sensor 110 to an object located far away. Here, the case where the vehicle 10 is not illuminated with the output light 20L2 refers not only to the case where the output light 20L2 passes across the front or rear of the vehicle 10, but also to the case where the output light 20L2 passes through an opening. In reality, the measured distances differ between the vehicle body 12 and the wheels 14, but in Fig. 4, for simplicity, the measured distances between the vehicle body 12 and the wheels 14 are constant.

[0051] 4, φ=0°, but φ≠0° may also be true. That is, the output light 20L2 may not only cross the road surface obliquely, but also cross the traveling direction of the vehicle 10 obliquely. With such a configuration, as can be seen from the above equations (4) and (5), the difference between the measured speeds v1 and v2 becomes larger, making it easier to detect the rotating axle.

[0052] By using the above method, it is possible to identify the rotating wheels of a traveling vehicle 10 and count the number of rotating axles. However, as described above, if the vehicle 10 accelerates or decelerates during measurement, the measured speed value associated with the rotation of the wheels will differ from that when the vehicle speed is constant, making it difficult to identify the rotating wheels or axles. Hereinafter, an embodiment for solving this problem will be described in detail.

[0053] <Embodiment> FIG. 5 is a diagram illustrating a schematic configuration example of a sensing system 100 according to an exemplary embodiment of the present disclosure. The sensing system 100 illustrated in FIG. 5 is an example of a measurement system based on FMCW-LiDAR technology. The sensing system 100 measures the speed of a traveling vehicle and the rotation speed of the wheels of the vehicle, and counts the rotating axles included in the vehicle based on the measurement results. In this specification, "measurement of rotation speed" is not limited to measuring the rotation speed (i.e., the number of rotations or rotation angle per unit time) itself, but also includes measuring the speed of a measurement point associated with rotation, and measuring the component of the speed of the measurement point in the direction toward the sensor. The "measurement point" is a point where a light beam emitted from a sensor is irradiated, and is also referred to as an "irradiation point."

[0054] The sensing system 100 shown in FIG. 5 includes a first sensor 111, a second sensor 112, a processing device 120, a storage device 130, and an output device 140. The first sensor 111 is a camera sensor, a radar sensor, or an ultrasonic sensor for measuring speed. The camera sensor measures speed using a camera. The radar sensor measures speed using electromagnetic waves. The ultrasonic sensor measures speed using ultrasonic waves. The second sensor 112 is a sensor using FMCW-LiDAR technology for measuring distance and speed, i.e., an FMCW-LiDAR sensor.

[0055] The first sensor 111 is used to measure the speed of the vehicle 10 and the presence or absence of the vehicle 10. Instead of measuring the presence or absence of the vehicle 10, the distance to the vehicle 10 may be measured. The second sensor 112 is used to measure the rotation speed of the wheels included in the vehicle measured by the first sensor 111 and the distance to the wheels.

[0056] The processing device 120 may be a computer including one or more processors and one or more memories. The processor executes a computer program stored in the memory to perform various processes described below. The processing device 120 is connected to the first sensor 111 and the second sensor 112.

[0057] The storage device 130 is a device including any storage medium such as a semiconductor storage medium or a magnetic storage medium. The storage device 130 is connected to the processing device 120 and stores various data generated by the processing device 120 during processing.

[0058] The output device 140 includes, for example, a communication device, and outputs the processing result by the processing device 120 to a higher-level system. The output device 140 may include a display device that displays the processing result of the processing device 120.

[0059] The upper system is a computer system connected to the sensing system 100, more specifically, to the output device 140 included in the sensing system 100, by wire or wirelessly. The upper system records the number of axles of each vehicle traveling on a road and manages tolls. The upper system may display information related to the number of axles based on axle number information indicating the number of axles obtained from the processing device 120. The information related to the number of axles may be, for example, a toll. The upper system may be realized by, for example, a server computer on a cloud. The output device 140 and the upper system may communicate with each other via a network such as the Internet.

[0060] The second sensor 112 includes an emission unit that emits a light beam for measuring the wheel speed of the vehicle. The second sensor 112 may include a configuration similar to that of the light source 20, the interference optical system 30, the photodetector 40, and the beam shaper 50 in the sensor 110 shown in Fig. 1, for example. In this specification, the light beam is simply referred to as a "beam."

[0061] In the following, an embodiment in which the first sensor 111 is a camera sensor will be described as embodiment 1. An embodiment in which the first sensor 111 is a radar sensor will be described as embodiment 2. An embodiment in which the first sensor 111 is an ultrasonic sensor will be described as embodiment 3.

[0062] <Embodiment 1> Fig. 6 is a diagram showing an example configuration of the sensing system 100 according to the first exemplary embodiment of the present disclosure. Fig. 6 shows the rear part of the vehicle 10 to be measured. The vehicle 10 shown in Fig. 6 is a standard automobile. The thick arrows shown in Fig. 6 represent the flow of light, and the thin arrows shown in Fig. 6 represent the flow of signals.

[0063] The first sensor 111 is configured as a camera sensor including a camera 70 and an image processing device 80. The camera sensor is used to measure the speed of the vehicle 10.

[0064] The camera 70 captures an image of a predetermined area including the side of the vehicle body. The predetermined area may include the top surface of the vehicle body instead of the side of the vehicle body. If the camera 70 is capable of continuously capturing images of a plurality of frames, it can measure the speed of the vehicle 10 at a predetermined cycle, such as 1 / 30 seconds.

[0065] The triangle and the thick arrow in FIG. 6 represent the light having a spread from a predetermined area entering the camera 70. The triangle is formed by a solid line and a dashed line, and the solid line represents the predetermined area, and the dashed line represents the spread of the light. In the example shown in FIG. 6, the reflected light generated by irradiating the vehicle 10 with the ambient light enters the camera 70, but is not limited to this example. The first sensor 111 may further include a light source that emits light for irradiating the vehicle 10 around the camera 70. In that case, the reflected light generated by irradiating the vehicle 10 with the light enters the camera 70.

[0066] The image processing device 80 generates information regarding the presence or absence of the vehicle 10 and speed information of the vehicle 10 based on an image of all or a part of the vehicle 10 captured by the camera 70. In this specification, the speed information of the vehicle 10 is also referred to as "first speed information." The speed information of the vehicle 10 is information regarding the traveling speed of the vehicle 10, and may include, for example, information on the traveling speed of the vehicle 10 itself, or information from which the traveling speed of the vehicle 10 can be derived.

[0067] In this way, the camera sensor generates the first speed information based on an image obtained by photographing the side or top surface of the vehicle body.

[0068] The second sensor 112 is configured as an FMCW-LiDAR sensor including a light source 20, an interference optical system 30, a photodetector 40, a beam shaper 50, and a processing circuit 60. The configurations and functions of the light source 20, the interference optical system 30, the photodetector 40, and the beam shaper 50 are as described with reference to FIG. 1. The processing circuit 60 controls the light source 20 and the photodetector 40. The light source 20 emits a laser light whose frequency varies periodically in response to a control signal input from the processing circuit 60. The interference optical system 30 separates the laser light emitted from the light source 20 into an output light and a reference light, and generates an interference light between the reflected light from the object and the reference light. The photodetector 40 receives the interference light and outputs an electrical signal, i.e., a beat signal, according to the intensity of the interference light. The processing circuit 60 generates distance information and speed information of the wheels of the vehicle 10 based on the beat signal output from the photodetector 40 of the second sensor 112. In this specification, the wheel speed information is also referred to as "second speed information". The wheel speed information is information relating to the speed of the wheels and may include, for example, information on the rotational speed of the wheels themselves or information from which the rotational speed of the wheels can be derived.

[0069] The processing device 120 counts the rotating axles on the vehicle 10 and generates axle number information based on the speed information of the vehicle 10 and the wheel distance information and speed information. However, the wheel distance information is not necessarily required to generate the axle number information.

[0070] In addition, components that perform part of the functions of the first sensor 111 and the second sensor 112 may be included in the processing device 120. The components may be, for example, the image processing device 80 included in the first sensor 111 and / or the processing circuit 60 included in the second sensor 112. Such a processing device 120 may be configured to generate speed information based on an image captured by the camera 70 included in the first sensor 111, and generate distance information and speed information based on a signal output from the photodetector 40 included in the second sensor 112. The processing device 120 may be configured to perform processing to count the number of rotating axles in the vehicle 10 based on the speed information of the vehicle 10 output from the image processing device 80 in the first sensor 111 and the distance information and speed information of the wheels output from the processing circuit 60 in the second sensor 112. In this case, the combination of the processing device 120, the image processing device 80 included in the first sensor 111, and the processing circuit 60 included in the second sensor 112 functions as "a processing device that generates first speed information and second speed information, and counts the rotating axles of the vehicle based on the first speed information and the second speed information to generate axle number information."

[0071] In this specification, the "photographing area" of the camera 70 is an area on the vehicle 10 side that corresponds to a captured image when the camera 70 captures an image of the traveling vehicle 10. The photographing area of ​​the camera 70 may be rephrased as the photographing area of ​​the camera sensor. The photographing area may include a flat or curved surface that constitutes the surface of the vehicle 10. When the image processing device 80 crops the captured image, the area on the vehicle 10 side that corresponds to the cropped image may be the photographing area. Based on the image that corresponds to the photographing area, speed information of the vehicle 10 and information on the presence or absence of the vehicle 10 are generated.

[0072] When the photographed area is sufficiently wide, more specifically, when it is sufficiently wide in the height direction of the vehicle 10, it becomes possible for the image processing device 80 to extract many feature points of the vehicle body. In particular, when the photographed area includes the entire vehicle body in the height direction of the vehicle 10, many parts of the vehicle body can be included in the photographed image, and it becomes possible for the image processing device 80 to extract more feature points of the vehicle body. In addition, even if the vehicle 10 has a gap, the probability that the photographed image includes a part of the vehicle body can be increased, and it becomes possible for the image processing device 80 to extract more feature points of the vehicle body. Furthermore, even if the vehicle 10 has an optically low reflectance such as a black paint and / or a surface state close to a mirror such as a plated paint, it is possible to include the boundary between the vehicle body and the background in the photographed image, and it becomes possible for the image processing device 80 to extract more feature points of the vehicle body. By extracting more feature points of the vehicle body, it becomes possible to more stably acquire information on the traveling speed of the vehicle 10.

[0073] In order to avoid detecting the rotation of the wheels, the area above the top end of the wheels may be set as the shooting area, but generally, even if the wheels are included in the image, it is difficult to detect the rotation speed component from the image.

[0074] In this specification, the term "emitter" refers to a part or component of the FMCW-LiDAR sensor that emits a beam toward an external space. In the example shown in FIG. 6, the beam shaper 50 corresponds to the emitter. The sensing system 100 includes an emitter that emits a beam for measuring the rotation speed of the wheels of the vehicle 10. The emitter is fixed so as to face the direction in which the vehicle 10 to be measured passes.

[0075] 6 shows the beam being perpendicularly irradiated to the side surface of the vehicle 10, but in reality, the beam is irradiated obliquely to the side surface of the vehicle 10. In this embodiment, the beam is irradiated obliquely to the side surface of the wheel of the vehicle 10.

[0076] The "illumination area" of the FMCW-LiDAR sensor is the area of ​​the illumination point when the beam from the emission unit is illuminated on the surface of the vehicle 10. Based on the light reflected from this area, speed information and distance information are generated. The shape of the illumination spot may be, for example, circular.

[0077] The spot of the irradiation point is focused by the collimator lens 52 included in the beam shaper 50 so that the spot diameter is sufficiently small. The spot diameter on the surface of the vehicle 10 may be, for example, 1 mm or less. The smaller the spot diameter, the greater the amount of reflected light that can be returned to the emission part, and the S / N ratio of the signal detected by the photodetector 40 can be improved.

[0078] The tire of the wheel does not have a gap due to the structure of the tire when air is put in. The difference in the optical characteristics of the tire is small regardless of the vehicle 10. The area of ​​the tire is small compared to the vehicle body. For these reasons, it is effective to measure the rotation speed of the wheel by irradiating the wheel with a beam having a small spot diameter.

[0079] The shortest distance from the camera 70 to the nearest vehicle 10 may be, for example, 0.1 m or more and 10 m or less. The same applies to the shortest distance from the emission part of the FMCW-LiDAR sensor to the nearest vehicle 10.

[0080] Fig. 7 is a diagram showing an example of the arrangement of the camera 70 and the emission unit 112a. Part (a) of Fig. 7 shows the side of the vehicle 10 to be measured. Part (b) of Fig. 7 shows the front of the vehicle 10. Part (c) of Fig. 7 shows the top surface of the vehicle 10.

[0081] The black dot at the bottom left shown in part (a) of FIG. 7 represents the irradiation point 112b of the beam emitted from the emission unit 112a. The rectangular area shown in part (a) of FIG. 7 represents the shooting area of ​​the camera 70. The black dot in the middle of the rectangular area represents the center 111b of the shooting area. The star marks shown in parts (b) and (c) of FIG. 7 represent the position of the emission unit 112a. The thick arrows starting from the star marks shown in parts (b) and (c) of FIG. 7 represent the beam emitted from the emission unit 112a. The black dots shown in parts (b) and (c) of FIG. 7 represent the center 111a of the lens (not shown) of the camera 70. The thick arrows from the vehicle 10 shown in parts (b) and (c) of FIG. 7 represent a part of the reflected light from the vehicle body 12 that is condensed toward the center 111a of the lens. The white arrows shown in part (c) of FIG. 7 represent the traveling direction of the vehicle 10.

[0082] The X-axis, Y-axis, and Z-axis shown in FIG. 7 and the following figures are as described above. The "driving direction" of the vehicle 10 refers to the direction in which the road on which the vehicle 10 runs extends. The road extends linearly within the area in which the measurement is performed, and the direction parallel to the road corresponds to the "driving direction". The vehicle 10 does not necessarily run parallel to the direction in which the road extends, but in this specification, the "driving direction" refers to the direction in which the vehicle 10 advances that is parallel to the road, regardless of the actual orientation of the vehicle 10. In the following description, for simplicity, it is assumed that the vehicle 10 runs parallel to the road.

[0083] As shown in part (b) of FIG. 7, the camera 70 is positioned at a height where it can capture an image of a portion of the body of the vehicle 10. Meanwhile, the irradiation point 112b of the beam is positioned at a height where it can illuminate the wheels of the vehicle 10. The camera 70 captures one or more frames of images so as to scan the side of the body of the vehicle 10 from the front to the rear as the vehicle 10 travels. As the vehicle 10 travels, the beam scans the front part of the side of the body of the vehicle 10, the side of the front wheels, the part of the side of the body between the front and rear wheels, the side of the rear wheels, and the rear part of the side of the body in this order.

[0084] In this embodiment, the camera 70 and the emission unit 112a are disposed on the side of the vehicle 10. The angle of view of the camera 70 is adjusted so that the captured image includes part or all of the vehicle body in the height direction of the vehicle 10 while the vehicle is traveling. The emission unit 112a emits a beam obliquely from above toward the side of the wheels of the vehicle 10.

[0085] Here, a plane along the surface of the road (hereinafter also referred to as "road surface") 90 on which the vehicle 10 travels is defined as a first plane P1, and a plane perpendicular to the traveling direction of the vehicle 10 is defined as a second plane P2. If the road surface is considered to be approximately planar, the first plane P1 is parallel to the road surface. The first plane P1 is parallel to the XZ plane and corresponds to a horizontal plane. The second plane P2 is parallel to the YZ plane and corresponds to a vertical plane that crosses the road.

[0086] The angles φ and θ are as described above. That is, the angle φ is the angle between the direction of the beam and the second plane P2. The angle θ is the angle between the direction of the beam and the first plane P1. φ takes a positive value when the beam is inclined toward the traveling direction of the vehicle 10 (i.e., the -X direction) with respect to the second plane P2. θ takes a positive value when the beam is inclined upward (i.e., the +Y direction) with respect to the first plane P1.

[0087] In this embodiment, φ=0, θ>0. That is, the emission section 112a emits a beam in a direction parallel to the second plane P2 (that is, perpendicular to the traveling direction) and obliquely downward from above onto the side surface of the wheel.

[0088] 8A to 8C are diagrams illustrating an example of the operation of determining the speed of the vehicle 10 from an image of the vehicle captured by the camera 70. FIG.

[0089] 8A is a diagram showing images of the vehicle 10 in the nth and n+1th frames, where n is a natural number. As the vehicle 10 travels, the n+1th frame shows a closer rear portion of the vehicle 10 than the nth frame.

[0090] 8B is a diagram showing the correspondence between the feature points of the vehicle 10 in the n-th and (n+1)-th frames. n , q n , r n is detected, and the feature point p n+1 , q n+1 , r n+1 By matching similar feature points, p n and p n+1 Similarly, q n and q n+1 is associated, and r n and r n+1 For the detection and matching of the feature points, for example, a known image processing method may be used.

[0091] FIG. 8C is a diagram showing the movement amount of the vehicle 10 on the image obtained from the coordinates of each feature point. The thick arrow in FIG. 8C represents the movement amount on the image. The speed of the vehicle 10 on the image can be obtained from the movement amount on the image and the elapsed time between frames. When different speeds are detected from a plurality of sets of feature points, the average value or the most frequent value of those speeds may be obtained. When the vehicle 10 does not travel across lanes, such as the travel lanes of a toll booth, the variation in the distance from the camera 70 to the side of the vehicle 10 is not so large. Therefore, the actual speed of the vehicle 10 can be obtained by converting the speed of the vehicle 10 on the image.

[0092] When the photographed area is sufficiently wide, more specifically, when viewed from the side of the vehicle 10, it is sufficiently wide in the horizontal direction parallel to the road surface. n , q n , r n The feature points p n+1 , q n+1 , r n+1 exists in the image of the n+1th frame. In that case, the velocity of the vehicle 10 can be obtained by the above operation.

[0093] In the examples shown in Figures 8A to 8C, it is assumed that the side of the vehicle 10 is at the same position on the lane regardless of the vehicle 10. In that case, the size of the vehicle 10 shown in the captured image is always the same. However, if the lane width is wide, the vehicle 10 may be traveling at different positions between the left end and the right end of the lane, so the size of the vehicle 10 shown in the captured image differs depending on the traveling position of the vehicle 10. In that case, even if the feature point moves by the same number of pixels per unit time on the image, the speed of the vehicle 10 is not necessarily the same.

[0094] Therefore, the distance to the vehicle 10 may be estimated based on the size of the vehicle 10 captured in the captured image, and the actual speed of the vehicle 10 may be calculated based on the estimated distance. In this case, the actual speed of the vehicle 10 can be calculated more accurately. Alternatively, the actual speed of the vehicle 10 may be estimated using distance information obtained by the FMCW-LiDAR sensor.

[0095] 8D is a diagram for explaining a method of calculating the speed of the vehicle 10 based on the distance to the vehicle 10. The horizontal angle of view of the camera 70 is assumed to be α. In the example shown in FIG. 8D, the distance d from the camera 70 to the vehicle 10 and the movement amount p of the feature point on the image per unit time are m Here, the unit time is the time from capturing the nth frame to capturing the n+1th frame.

[0096] When a vehicle 10 at a distance d appears in a photographed image, the actual horizontal length of the photographed area is r h is r as shown in Figure 8D. h = 2d tan(α / 2). The total number of pixels in the horizontal direction of the captured image is p h Then, the actual travel distance of vehicle 10 per unit time is r m is r m =(p m / p h )r h =(p m / p h )·2d·tan(α / 2). The actual travel distance r of vehicle 10 per unit time mgives the speed of vehicle 10.

[0097] Fig. 9 is a graph showing an example of the speed and wheel rotation speed of the vehicle 10 measured by the sensing system 100. The upper part of Fig. 9 shows an example of the change in speed over time measured by the camera sensor. The lower part of Fig. 9 shows an example of the change in speed over time measured by the FMCW-LiDAR sensor.

[0098] In the camera sensor, the image processing device 80 calculates the speed based on the characteristic points of the body of the vehicle 10. Therefore, as shown in the upper part of FIG. 9, the measured speed is almost constant while the vehicle 10 is in the image, and is zero while the vehicle 10 is not in the image. On the other hand, in the FMCW-LiDAR sensor, the beam is irradiated to the body and wheels of the vehicle 10. The measured speed at the irradiation point 112b of the beam is the component of the speed of the body or the wheel in the direction toward the emission unit 112a. In this embodiment, since φ=0, θ>0, in the measurement by the beam, the measured speed of the body is almost zero, and only the Y-direction component of the speed at the irradiation point 112b on the side of the wheel is substantially measured. Therefore, in this embodiment, the measured speed data shown in FIG. 9 is obtained.

[0099] In reality, the vehicle 10 may accelerate or decelerate during measurement, so the actually measured speed may show a time change different from that shown in the graph in Fig. 9. In addition, due to, for example, misalignment of the camera 70 and the emitter 112a and misalignment of the traveling direction of the vehicle 10, the measured speed often does not actually become zero even during a period when the measured speed should become zero. For this reason, the processing device 120 may perform processing such as treating the measured speed as zero if it is less than a threshold close to zero. The threshold may be determined based on, for example, a statistical value such as the variance or standard deviation of the acquired data.

[0100] In this embodiment, φ=0, but it may be φ>0 or φ<0. That is, the emission unit 112a may emit a beam from the front side or rear side of the vehicle 10 toward the wheels.

[0101] FIG. 10A is a diagram showing an example of the relationship between the position of the photographing area of ​​the camera 70 in the vehicle 10, the position of the irradiation point 112b of the beam, and the timing at which the speed at the irradiation point 112b is measured. In the example shown in FIG. 10A, φ=0, and the camera 70 and the emission unit 112a are arranged so that the center 111b of the photographing area is located on the rear side of the vehicle 10 relative to the irradiation point 112b. When viewed from the side of the vehicle 10, the maximum range of the photographing area includes the irradiation point 112b, i.e., the irradiation area of ​​the beam, in the horizontal direction parallel to the road surface. At this time, the speed measurement by the camera sensor is started before the speed measurement by the FMCW-LiDAR sensor.

[0102] Here, the distance in the X direction (i.e., horizontal direction) between the irradiation point of the beam on the vehicle 10 and the center of the imaging area is Δx, the length of the imaging area in the X direction is W, the overall length of the vehicle 10 is L, and the vehicle 10 travels at a constant traveling speed V during measurement. In this case, the speed measurement of the vehicle 10 by the camera sensor continues for a time (L+W) / V, the speed measurement of the vehicle 10 by the FMCW-LiDAR sensor continues for a time L / V, and the speed measurement by the camera sensor starts earlier by a time of ((W / 2)+Δx) / V and ends later by a time of ((W / 2)-Δx) / V than the speed measurement by the FMCW-LiDAR sensor. The time period during which the FMCW-LiDAR sensor measures the wheel speed is entirely included in the time period during which the camera sensor measures the speed of the vehicle 10, or the presence or absence of the vehicle 10 in addition to the speed of the vehicle 10. Therefore, in this example, the processing unit 120 does not need to count the rotating axles by taking into account the time difference between the timing of the speed measurements by the camera sensor and the FMCW-LiDAR sensor.

[0103] FIG. 10B is a diagram showing another example of the relationship between the position of the photographing area of ​​the camera 70 in the vehicle 10, the position of the irradiation point 112b of the beam, and the timing at which the speed at the irradiation point 112b is measured. In the example shown in FIG. 10B, unlike the example shown in FIG. 10A, when viewed from the side of the vehicle 10, the maximum range of the photographing area does not include the irradiation area of ​​the beam in the horizontal direction parallel to the road surface. In this case, the speed measurement by the camera sensor starts earlier by a time of (Δx+(W / 2)) / V than the speed measurement by the FMCW-LiDAR sensor, and ends earlier by (Δx-(W / 2)) / V. The part before the last part (i.e., the time period of (Δx-(W / 2)) / V) of the time period during which the FMCW-LiDAR sensor measures the wheel speed is included in the time period during which the camera sensor measures the speed of the vehicle 10, or the presence or absence of the vehicle 10 in addition to the speed of the vehicle 10. However, the last part is not included in the time interval during which the camera sensor measures the speed of the vehicle 10, or the presence or absence of the vehicle 10 in addition to the speed of the vehicle 10. Therefore, in this example, the processing device 120 counts the rotating axles taking into account the time difference between the timing of the end of the speed measurements by the camera sensor and the FMCW-LiDAR sensor.

[0104] Next, a specific example of the operation of the sensing system 100 according to this embodiment will be described. Fig. 11 is a flowchart showing an example of the operation of the processing device 120 in the sensing system 100. The processing device 120 starts operation according to an operation start signal input from an input means (not shown). The input means may be, for example, an input device such as an external computer. The processing device 120 executes the operations of steps S1010 to S1080 shown in Fig. 11. The operation of each step will be described below.

[0105] <Step S1010> The processor 120 judges whether or not an operation end signal has been input from the input means. If an end signal has been input, the processor 120 ends the operation. If an end signal has not been input, the process proceeds to step S1020.

[0106] <Step S1020> The processing device 120 determines whether or not the vehicle 10 is present based on the measurement results from the camera sensor. If it is determined that the vehicle 10 is present, the process proceeds to step S1060. If it is determined that the vehicle 10 is not present, the process proceeds to step S1030. Details of the operation for determining whether or not the vehicle 10 is present will be described later with reference to FIG.

[0107] <Step S1030> The processing device 120 determines whether the number of axles recorded in the storage device 130 is greater than zero. The number of axles is recorded in the storage device 130 when the rotating axles are counted in step S1080, which will be described later. If the number of axles recorded is greater than zero, the process proceeds to step S1040. If the number of axles recorded is zero, the process returns to step S1010.

[0108] <Step S1040> The processing device 120 outputs the number of axles recorded in the storage device 130 to the output device 140. The output device 140 transmits the recorded number of axles as the number of axles of the vehicle 10 that has just passed by to a higher-level system.

[0109] <Step S1050> The processing unit 120 resets to zero the number of axles recorded in the storage unit 130. After the operation of step S1050, the process returns to step S1010.

[0110] <Step S1060> When the processing device 120 determines in step S1020 that the vehicle 10 is present, the process proceeds to step S1060. In step S1060, the processing device 120 determines whether or not the rotation speed of the wheels has been measured based on the results of the speed measurements by the camera sensor and the FMCW-LiDAR sensor. When the speed of the vehicle 10 measured by the camera sensor is greater than zero and the rotation speed of the wheels measured by the FMCW-LiDAR sensor is greater than zero, or when the rotation speed has been continuously measured until just before, the processing device 120 determines that the rotation speed of the wheels has been measured. When the processing device 120 determines that the rotation speed of the wheels has been measured, the processing device 120 records information on the rotation speed of the wheels in the storage device 130. On the other hand, when the processing device 120 determines that the rotation speed is no longer being measured, the processing device 120 records information on the end of rotation indicating that the section of the rotating wheels has ended in the storage device 130. When the rotation speed has been measured, the process returns to step S1010. When the rotation speed has not been measured, the process proceeds to step S1070. The details of the operation for determining whether or not the rotation speed has been measured will be described later with reference to FIG.

[0111] <Step S1070> The processing device 120 judges whether the measurement section of the wheel has ended or not, according to whether the information on the rotation speed and the end of rotation has been recorded in the storage device 130 or not. Here, the rotation speed of the wheel is measured immediately before, and it is judged whether the measurement has ended or not. If it is judged that the measurement section of the wheel rotation speed has ended, the process proceeds to step S1080. If it is judged that the measurement section of the wheel rotation speed has not ended, the process returns to step S1010. Details of the operation of judging whether the measurement section of the wheel rotation speed has ended or not will be described later with reference to FIG. 15.

[0112] <Step S1080> When the processing device 120 determines that the measurement section of the wheel rotation speed has ended, it adds 1 to the number of axles and records it in the memory device 130. That is, the processing device 120 counts 1 each time a rotating axle is detected, and stores the counted number of axles in the memory device 130. After the operation of step S1080, the process returns to step S1010.

[0113] By repeating the operations from step S1010 to step S1080, the processing device 120 can detect and count the rotating axles included in the vehicle 10 that is the measurement target.

[0114] Next, the operation of step S1020 will be described in detail with reference to FIG.

[0115] Fig. 12 is a flowchart showing the details of the operation in step S1020 to determine the presence or absence of the vehicle 10. Step S1020 includes steps S1021 to S1024 shown in Fig. 12. The operation of each step will be described below.

[0116] <Step S1021> The processing device 120 judges whether the presence of the vehicle 10 has been measured based on the result of the distance measurement by the camera sensor. Specifically, the processing device 120 judges that the presence of the vehicle 10 has been measured when the image acquired by the image processing device 80 included in the camera sensor includes a part or the whole of the vehicle 10. In other cases, the processing device 120 judges that the presence of the vehicle 10 has not been measured, that is, the vehicle 10 was not present. When the processing device 120 judges that the presence of the vehicle 10 has been measured, the processing device 120 associates the presence of the vehicle 10 with the time and stores it in the storage device 130. If the presence of the vehicle 10 has been measured, the process proceeds to step S1023. If the presence of the vehicle 10 has not been measured, the process proceeds to step S1022.

[0117] <Step S1022> The processing device 120 reads out the most recent time when the distance to the vehicle 10 was measured from the storage device 130, and judges whether the difference between the time and the current time is within a predetermined margin. In the example shown in FIG. 10B, the margin is a value equivalent to the time offset [Δx-(W / 2)] / V. Δx is a fixed value determined by the position and orientation of the emission unit 112a. The speed V can be calculated based on the result of the speed measurement by the camera sensor. Alternatively, an average vehicle speed that is expected in advance can be set as V. If the difference between the most recent time when the presence of the vehicle 10 was measured and the current time is within the margin, proceed to step S1023. If the difference between the most recent time when the presence of the vehicle 10 was measured and the current time exceeds the margin, proceed to step S1024.

[0118] 10A, the determination step of step S1022 can be omitted because the time interval during which the FMCW-LiDAR sensor measures the wheel speed is included in the time interval during which the camera sensor measures the speed of the vehicle 10, or the presence or absence of the vehicle 10 in addition to the speed of the vehicle 10. The presence or absence of the vehicle 10 needs to be determined only in the determination step of step S1021, which has the advantage of simplifying the processing steps.

[0119] <Step S1023> The processing device 120 determines that the vehicle 10 is within the measurement range of the sensing system 100, and proceeds to step S1060.

[0120] <Step S1024> The processing device 120 determines that the vehicle 10 is not within the measurement range of the sensing system 100, and proceeds to step S1030.

[0121] Next, the operation of step S1060 will be described in detail with reference to FIG.

[0122] Fig. 13 is a flowchart showing details of the operation of determining whether or not the rotation speed of the wheel has been measured in step S1060. Step S1060 includes the operations of steps S1061 to S1069 shown in Fig. 13. The operation of each step will be described below.

[0123] <Step S1061> The processing device 120 determines whether or not the speed of the vehicle 10 to be measured has been measured based on the speed measured by the camera sensor. That is, the processing device 120 determines whether or not the vehicle 10 to be measured is moving. If the speed of the vehicle 10 has been measured, the process proceeds to step S1062. If the speed of the vehicle 10 has not been measured, the process proceeds to step S1066. Details of the method of determining whether or not the vehicle 10 is moving will be described later with reference to FIG. 14.

[0124] <Step S1062> The processing device 120 determines whether the absolute value of the rotation speed measured by the FMCW-LiDAR sensor is greater than a threshold value. The threshold value is a predetermined value close to zero, and may be determined based on a statistical value such as the variance or standard deviation of the acquired rotation speed data. If the absolute value of the measured rotation speed is greater than the threshold value, the process proceeds to step S1064. If the absolute value of the measured rotation speed is equal to or less than the threshold value, the process proceeds to step S1063.

[0125] <Step S1063> The processing device 120 judges whether the absolute value of the rotation speed obtained in any of the immediately preceding consecutive measurements of a predetermined number of times (e.g., 1, 2, 3, etc.) is greater than the above threshold value based on the rotation speed information stored in the storage device 130. If the absolute value of the rotation speed obtained in any of the immediately preceding measurements of a predetermined number of times is greater than the threshold value, the process proceeds to step S1064. If the absolute values ​​of the rotation speed obtained in all of the immediately preceding measurements of a predetermined number of times are equal to or less than the threshold value, the process proceeds to step S1066.

[0126] <Step S1064> The processing device 120 stores the value of the rotation speed currently measured using the beam in the storage device 130 .

[0127] In this embodiment, the emission unit emits a beam in a direction perpendicular to the traveling direction of the vehicle 10, so that a velocity component in the same direction as the traveling direction is not measured. On the other hand, since the emission direction of the beam has an angle greater than zero with respect to a plane parallel to the road surface (i.e., a horizontal plane), a velocity component in the vertical direction can be measured. That is, in measuring the rotational speed of a wheel using a beam, a value corresponding to a vertical component of a velocity vector accompanying the rotation of the wheel at the position where the beam is irradiated is measured. Therefore, as shown in the lower part of FIG. 9, in a time period in which there is no vertical component of the velocity due to the rotation, that is, in a time period in which the beam is irradiated to the body part of the vehicle 10, the measured velocity is substantially zero. A rotating wheel has a downward velocity component in the front half and an upward velocity component in the rear half.

[0128] In the example shown in FIG. 9, the downward velocity component is measured as a negative value, and the upward velocity component is measured as a positive value. In this embodiment, the vertical component of the velocity of one rotating wheel measured using a beam has a moment of zero because the sign is reversed from negative to positive in the process of measuring one wheel. In order to determine that the section is a section of one rotating wheel even at a time when the vertical component of the velocity is zero even though it is a section of a wheel, the process of step S1063 is introduced in the example shown in FIG. 13. As a result, when the magnitude of the measured velocity by the FMCW-LiDAR sensor obtained in one or more measurements immediately before exceeds a threshold close to zero, even if the measured velocity by the FMCW-LiDAR sensor in the current measurement is equal to or less than the threshold (for example, almost zero), the measured velocity is recorded in step S1064 as the value of the velocity in the section of the rotating wheel.

[0129] <Step S1065> The processor 120 determines that the rotation speed has been measured, and returns to step S1010.

[0130] <Step S1066> The processing device 120 refers to the storage device 130 and determines whether the end of the rotating wheel section has been recorded. The end of the rotating wheel section is recorded in step S1068, which will be described later. If the end of the rotating wheel section has been recorded, the process proceeds to step S1069. If the end of the rotating wheel section has not been stored, the process proceeds to step S1067.

[0131] <Step S1067> The processing device 120 reads out from the storage device 130 the measured values ​​of the rotational speed acquired so far by the measurement using the FMCW-LiDAR sensor, and judges whether the time change of the measured values ​​of the rotational speed matches the pattern of the end of the section of the rotating vehicle. For example, the processing device 120 judges whether the measured values ​​of the rotational speed acquired by one or more previous measurements show a pattern of changing from a value exceeding the above threshold (i.e., a value greater than zero) to the current measured value (e.g., approximately zero). Alternatively, the processing device 120 may judge whether the time change of the measured values ​​of the rotational speed acquired by multiple measurements immediately before the current measurement changes from a negative value to a positive value and then changes to a value approximately zero, as shown in FIG. 9. Note that, when the beam is emitted obliquely upward from below the vehicle toward the wheels (i.e., when θ<0), it may be judged whether the time change of the measured values ​​of the rotational speed changes from a positive value to a negative value and then changes to a value approximately zero. When the measured time change of the rotational speed matches the pattern of the end of the section of the rotating wheels, the process proceeds to step S1068. If the measured change in rotation speed over time does not match the pattern of the end of a section of a rotating wheel, proceed to step S1069.

[0132] In this embodiment, the time change in the rotation speed as shown in Fig. 9 is recorded in advance in the storage device 130 as a time change pattern of the rotation speed of the wheel measured using the beam. This enables the processing device 120 to correctly determine the timing at which the section of the rotating wheel ends, and to identify a state in which the rotation of the wheel is not detected.

[0133] <Step S1068> The processing unit 120 records the end of the interval of the rotating wheels in the storage unit 130. At this time, the processing unit 120 erases the previous record of the rotation speed of the wheels.

[0134] <Step S1069> The processor 120 determines that the rotation speed has not been measured in the current measurement, and proceeds to step S1070.

[0135] Next, the operation of step S1061 will be described in more detail with reference to FIG.

[0136] Fig. 14 is a flowchart showing details of the operation of step S1061. Step S1061 includes the operations of steps S1161 to S1164 shown in Fig. 14. The processing device 120 judges whether the speed of the vehicle 10 to be measured has been measured, i.e., whether the vehicle 10 is moving, based on the speed value measured by the camera sensor. The operation of each step will be described below.

[0137] <Step S1161> The processing device 120 determines whether the speed measured by the camera sensor is greater than a threshold value. The threshold value is a predetermined value close to zero, and may be determined based on a statistical value such as the variance or standard deviation of the acquired speed data. If the measured speed is greater than the threshold value, the process proceeds to step S1162. If the measured speed is equal to or less than the threshold value, the process proceeds to step S1163.

[0138] <Step S1162> The processor 120 determines that the speed of the vehicle 10 has been measured, that is, that the vehicle 10 to be measured is moving, and proceeds to step S1062.

[0139] <Step S1163> The processing device 120 reads from the storage device 130 the time when the measured speed of the vehicle 10 exceeded the threshold, and judges whether the difference between that time and the current time is within a predetermined margin. In the example shown in FIG. 10B, the margin is a value equivalent to the time offset [Δx-(W / 2)] / V. If the difference between the time when the measured speed of the vehicle 10 exceeded the threshold and the current time is within the margin, the process proceeds to step S1162. If the difference between the time when the measured speed of the vehicle 10 exceeded the threshold and the current time exceeds the margin, the process proceeds to step S1164.

[0140] <Step S1164> The processing device 120 determines that the speed of the vehicle 10 has not been measured, and proceeds to step S1066.

[0141] As with step S1022 shown in FIG. 12, in the example shown in FIG. 10A, the determination step of step S1163 can be omitted, and the processing steps can be simplified.

[0142] Next, the operation in step S1070 shown in FIG. 11 will be described in more detail with reference to FIG.

[0143] Fig. 15 is a flowchart showing details of the operation of step S1070. Step S1070 includes steps S1071 to S1074 shown in Fig. 15. The operation of each step will be described below.

[0144] <Step S1071> The processing device 120 refers to the storage device 130 and determines whether information indicating the end of the section of the rotating wheels is recorded. The information is recorded in step S1068 shown in Fig. 13. If the information is recorded, the process proceeds to step S1074. If the information is not recorded, the process proceeds to step S1072.

[0145] <Step S1072> The processing device 120 refers to the storage device 130 and determines whether or not there is a record of the rotation speed measured using the beam in one or more measurements prior to the current measurement. If there is a record of the previously measured rotation speed, the process proceeds to step S1073. If there is no record of the previously measured rotation speed, the process proceeds to step S1074.

[0146] <Step S1073> The processor 120 determines that the rotating wheel section is continuing, ie, the rotating wheel section has not ended, and proceeds to step S1010.

[0147] <Step S1074> The processor 120 determines that the rotating wheel interval has ended and proceeds to step S1080.

[0148] In the above operation, the vehicle 10 may accelerate or decelerate while the rotation speed of the wheels is being measured. For example, the vehicle 10 may stop while the rotation speed of the wheels is being measured. FIG. 16 shows an example of the change in speed over time measured when the vehicle 10 stops while the rotation speed of the wheels is being measured. The upper part of FIG. 16 shows an example of the speed measured by the camera sensor. The lower part of FIG. 16 shows an example of the speed measured by the FMCW-LiDAR sensor. In the example shown in FIG. 16, the measurement value of the speed of the vehicle 10 by the image processing device 80 continues to be a constant value, and then decreases monotonically with deceleration and becomes zero. Thereafter, as the vehicle 10 accelerates, the measurement value of the speed increases and becomes a constant value again. When the running speed of the vehicle 10 decreases to zero and then accelerates, the measurement value shown in the lower part of FIG. 16 is obtained when the rotation speed of the wheels is measured by the FMCW-LiDAR sensor during the time period in which the vehicle 10 stops rotating and the vertical component of the speed at the irradiation point of the beam becomes zero, and the measured speed using the beam becomes zero. When accelerating after a section where the speed is zero, the vertical component of the wheel speed increases, so the absolute value of the speed measurement value using the beam also increases. As shown in the example of FIG. 16, even if there is a time section where the rotation speed of the wheel becomes zero as the vehicle 10 stops, in order to detect it as a section of one wheel, the process of step S1067 shown in FIG. 13 is introduced in this embodiment. As a result, even if the wheel speed is not detected in the measurement using the beam, it is determined that the measurement section of the rotation speed of one wheel continues until the time change pattern of the speed at the end of the measurement section of the rotation speed of the wheel is detected. Therefore, even if the vehicle 10 performs an operation involving acceleration or deceleration, such as stopping during measurement, the measurement section of the rotation speed of one wheel can be accurately detected.

[0149] Next, an example of the arrangement conditions of the emission unit that emits the beam for measuring the rotation speed of the wheel will be described.

[0150] 17A to 17E are diagrams for explaining the arrangement conditions of the emitter 112a in the FMCW-LiDAR sensor. For ease of explanation, the explanation will be given using the angle θp between the direction of the beam projected onto the second plane P2 perpendicular to the traveling direction of the vehicle 10 and the first plane P1 parallel to the road surface. The positive and negative values ​​of θp are defined the same as those of θ.

[0151] 17A shows a schematic diagram of the beam angle θp and the positional relationship with the vehicle 10 in the lane 92. In this embodiment, the beam emission direction is tilted downward from the horizontal, and the angle θp is positive. When the vehicle 10 to be measured travels on the side of the lane 92 closer to the emission unit 112a, the second beam is irradiated onto a higher position of the vehicle 10. Conversely, when the vehicle 10 travels on the side of the lane 92 farther from the emission unit 112a, the beam is irradiated onto a lower position of the vehicle 10, as shown by the dashed line.

[0152] FIG. 17B is a diagram showing a schematic diagram of a condition under which the beam can measure the rotational speeds of the wheels of all the vehicles 10 traveling in the lane 92. The diameter (i.e., height) of the smallest wheel assumed among the wheels of the vehicle 10 to be measured is set to h. In this case, the emitter 112a is arranged so that the beam is irradiated to a position less than the height h of the side of the wheel 14n located closest to the emitter 112a on the lane 92, and is irradiated to a position higher than the contact point between the side of the wheel 14f located farthest from the emitter 112a on the lane 92 and the road surface. For example, consider a case where the lane width is 3 m (meters), the minimum wheel height h is 0.5 m, and the width of the vehicle 10 is 1.5 m. In this case, the side of the wheel 14f located farthest from the emitter 112a is located 1.5 m from the side of the wheel 14n located closest to the emitter 112a. At this time, the position and orientation of the emission portion 112a are determined so that the angle θp is smaller than the following angle:

number

[0153] However, in the case of a two-wheeled vehicle, in which the wheels are further away from the emitting portion 112a and the distance between the side of the wheel 14f that is farthest from the emitting portion 112a and the side of the wheel 14n that is closest to the emitting portion 112a becomes closer to the lane width, the angle θp becomes even smaller.

[0154] By determining the angle θp as described above, the beam is irradiated onto the wheels no matter where the vehicle 10 to be measured is traveling within the lane. Therefore, the rotational speed of the wheels can be stably measured regardless of the position of the vehicle 10 within the lane.

[0155] As shown in Fig. 17C, multiple beams with different heights may be irradiated onto the wheels, and the speed of the corresponding wheels may be measured individually from each beam. In this case, the upper beam is used to irradiate the wheels located in the range from 14f to 14m, and the lower beam is used to irradiate the wheels located in the range from 14m to 14n, to measure their speed. In this method, the beam angle θp' shown in Fig. 17C can be made larger than the beam angle θp shown in Fig. 17B, so that the wheel speed can be measured with higher sensitivity.

[0156] Also, as shown in Fig. 17D, multiple beams of the same height may be irradiated onto the wheel, and the speed of the corresponding wheel may be measured individually from each beam. In this method, the beam angles θp', θp'' shown in Fig. 17D can be made larger than the beam angle θp shown in Fig. 17B, so that the wheel speed can be measured with higher sensitivity.

[0157] Alternatively, the wheel speed may be measured by scanning the beam while changing the irradiation angle in the vertical direction, as shown in Fig. 17E. This method allows the wheel speed to be measured with a single beam with higher sensitivity.

[0158] In the example shown in FIG. 17E, the positions are indicated by symbols 14n, 14m', 14m", and 14f, in order from closest to the emission part. When the irradiation angle is θp", the top of the wheel side located at symbol 14n is irradiated with the beam. When the irradiation angle is θp', the bottom of the wheel side located at symbol 14f is irradiated with the beam. When the beam is scanned, the irradiation direction of the beam continues to change up and down with the irradiation angle ranging from θp" to θp'.

[0159] Here, we will explain which parts of the vehicle 10 are illuminated by the beam as the illumination angle changes from θp" to θp'. When the wheel is located at reference symbol 14n, the beam illuminates the top of the side of the wheel and the vehicle body, in that order. When the wheel is located at reference symbol 14m', the beam illuminates the entire side of the wheel and the vehicle body, in that order. When the wheel is located at reference symbol 14m", the beam illuminates the road surface and the entire side of the wheel, in that order. When the wheel is located at reference symbol 14f, the beam illuminates the road surface and the bottom of the side of the wheel, in that order.

[0160] When the wheel is located in the range from 14n to 14m', a portion of the side of the wheel and the vehicle body are irradiated by the beam in this order. When the wheel is located in the range from 14m' to 14m", the road surface, the entire side of the wheel, and the vehicle body are irradiated by the beam in this order. When the wheel is located in the range from 14m" to 14f, the road surface and a portion of the side of the wheel are irradiated by the beam in this order.

[0161] In all of the above cases, the road speed is zero and the vehicle body speed is different from the wheel speed, so the wheel speed can be measured.

[0162] In the example shown in FIG. 17E, the positions of the wheels may be identified by a camera other than camera 70, and the irradiation angle of the beam may be optimized according to the positions of the wheels.

[0163] 17A to 17E, the beam will be irradiated onto the wheels no matter where in the lane the vehicle 10 to be measured is traveling. Therefore, the rotational speed of the wheels can be stably measured regardless of the position of the vehicle 10 in the lane.

[0164] As described above, the sensing system 100 in this embodiment can count the rotating axles by measuring the running speed of the vehicle 10 to be measured and the rotation speed of the wheels and identifying the rotating wheels in one vehicle 10. By measuring the running speed of the vehicle 10 and the rotation speed of the wheels, respectively, even if it is difficult to distinguish between a speed change due to rotation and a speed change due to acceleration or deceleration only from the measurement result of the sensor that measures the wheel speed, these speed changes can be distinguished. This makes it possible to more reliably count the rotating axles. Furthermore, by using the measurement result of the speed of the vehicle 10, it is possible to detect that the vehicle 10 is stopped during measurement. Therefore, when the wheel speed becomes zero during measurement, erroneous detection such as counting one wheel multiple times can be avoided, and the axles can be accurately counted.

[0165] Furthermore, the sensing system 100 in this embodiment measures the speed of the vehicle 10 based on information from a relatively wide area, and measures the rotational speed of the wheels based on information from a relatively small area. Therefore, even if the vehicle 10 has gaps, information on the traveling speed of the vehicle 10 can be stably acquired, and the number of axles can be counted accurately. Furthermore, even if the vehicle 10 is painted with a low reflectivity paint and / or has a surface state close to that of a mirror, information on the traveling speed of the vehicle 10 can be acquired with a high probability, and the axles can be counted accurately.

[0166] (Specific examples) Hereinafter, with reference to FIGS. 18A and 18B, the effect of detecting the traveling speed of a vehicle 10 having a gap or a low reflectance based on information from a wide shooting area will be described with a concrete example.

[0167] FIG. 18A is a diagram showing an example of the time change of the measured speed of a vehicle 10 having a gap. FIG. 18A shows a car carrier as an example of a vehicle 10 having a gap. The length of the vehicle 10 is 13.8 m and the height is 4 m. Between the front end and the rear end of the vehicle 10, there is one gap of 3 m x 2 m and three gaps of 2.3 m x 2 m in this order. The height from the bottom of the gap to the road surface is 1.5 m, and the width of the frame between the gaps is 0.35 m.

[0168] Assume that two types of cameras 70 directly face such a vehicle 10 and photograph the vehicle 10. One type of camera 70 has a photographing area (A) of 0.5m x 0.5m, and the other type of camera 70 has a photographing area (B) of 4m x 4m. The height of the centers of these photographing areas is 2m. The lower boundary of the photographing area (B) coincides with the road surface, and the height of the photographing area (B) is equal to the height of the vehicle 10. In this case, the photographing area (B) includes the entire body of the vehicle 10 in the height direction.

[0169] 18A, in the camera 70 having the photographing area (A), there are time periods during which the speed cannot be measured intermittently even though the vehicle 10 is traveling in front of the camera 70. This is because when the entire photographing area overlaps with the gap, the image processing device 80 cannot obtain information about the vehicle body and cannot detect the characteristic points of the vehicle body.

[0170] In contrast, with a camera 70 having a shooting area (B), the image processing device 80 can acquire information about the vehicle body while the vehicle 10 is traveling in front of the camera 70, making it possible to detect characteristic points of the vehicle body and continuously measure the speed of the vehicle 10.

[0171] Fig. 18B is a diagram showing an example of the change over time in the measured speed of a vehicle 10 with low reflectance. Fig. 18B shows a black painted car as an example of a vehicle 10 with low reflectance. The length of the vehicle 10 is 4.8 m and the height is 1.8 m. The headlights and windows are visible from the sides of the vehicle 10.

[0172] Assume that two types of cameras 70 directly face such a vehicle 10 and photograph the vehicle 10. One type of camera 70 has a photographing area (A) of 0.24 m x 0.24 m, and the other type of camera 70 has a photographing area (B) of 2.4 m x 2.4 m. The height of the centers of these photographing areas is 1 m. The lower boundary of the photographing area (B) coincides with the road surface, and the height of the photographing area (B) is greater than the height of the vehicle 10. In this case, the photographing area (B) includes the entire body of the vehicle 10 in the height direction.

[0173] 18B, in the camera 70 having the photographing area (A), there are time periods during which the speed cannot be measured intermittently even though the vehicle 10 is traveling in front of the camera 70. This is because the image processing device 80 can obtain information about the vehicle and detect characteristic points of the vehicle body only when the photographing area includes the boundary between the background and the vehicle body, or the boundary between the headlights and the vehicle body.

[0174] In contrast, it can be seen that the camera 70 having the shooting area (B) can continuously measure the speed while the vehicle 10 is traveling in front of the camera 70. This is because the image processing device 80 can always obtain information on any one of the boundaries between the vehicle body and the background, the boundaries between the vehicle body and the headlights, the boundaries between the vehicle body and the wheels, and the boundaries between the vehicle body and the windows, and can detect feature points.

[0175] As shown in FIGS. 18A and 18B, by measuring the traveling speed of the vehicle 10 based on information from a wider shooting area, the traveling speed of the vehicle 10 can be acquired more stably.

[0176] (Example of application to ETC) Next, an example of a method for installing the sensing system according to the first embodiment at an ETC toll booth will be described.

[0177] 19A and 19B are respectively a perspective view and a front view showing an example of the arrangement of the camera 70 and the emission unit 112a in the ETC. As shown in FIG. 19A, the camera 70 and the emission unit 112a in the first embodiment can be installed in a housing 96 installed on an island 94 that divides a lane. FIG. 19A illustrates an example of an image capturing area captured by the camera 70 and an emission direction of a beam 112c emitted from the emission unit 112a. In this example, the camera 70 and the emission unit 112a are arranged vertically side by side in the housing 96 installed on the island 94. The camera 70 is arranged at a higher position than the emission unit 112a.

[0178] 20A and 20B are a perspective view and a front view, respectively, showing another example of the arrangement of the camera 70 and the emitter 112a in the ETC. The camera 70a in the first embodiment may be arranged in a housing 97 installed facing downward from a gate 95 spanning lanes, as shown in FIG. 20A and FIG. 20B. The emitter 112a in the first embodiment may be arranged in a housing 96 installed on an island 94.

[0179] 20A and 20B, camera 70 captures an image of the upper surface of vehicle 10 as it travels from above vehicle 10. Emitter 112a irradiates light obliquely downward from the side of vehicle 10 onto the side of the wheels of vehicle 10 as it travels.

[0180] 19A to 20B, the emission unit 112a emits the beam 112c in a direction parallel to a plane perpendicular to the traveling direction of the vehicle 10 and obliquely downwardly incident on the side of the wheel of the vehicle 10. This arrangement is the same as the arrangement in the first embodiment.

[0181] <Embodiment 2> Next, a sensing system according to the second embodiment of the present disclosure will be described. Fig. 21 is a diagram showing another configuration example of the sensing system 100. The sensing system 100 shown in Fig. 21 differs from the sensing system 100 shown in Fig. 6 in that the first sensor 111 is a radar sensor rather than a camera sensor. The thick arrows shown in Fig. 21 represent the flow of electromagnetic waves, and the thin arrows shown in Fig. 21 represent the flow of signals.

[0182] The first sensor 111 is configured as a radar sensor including a radar device 72 and a signal processing device 82. The radar device 72 includes a transmitting antenna that transmits electromagnetic waves for irradiating the side of the vehicle body, and a receiving antenna that receives reflected waves resulting from the electromagnetic waves. Instead of the side of the vehicle body, the upper surface of the vehicle body may be irradiated with electromagnetic waves. The radar device 72 may be, for example, a millimeter wave radar device that emits millimeter waves with a frequency of 79 GHz. The radar sensor is used to measure the speed of the vehicle 10. If the radar device 72 is capable of continuous measurement, it can measure the speed at a predetermined period, such as 1 / 30 seconds. The triangle and the thick arrow in FIG. 21 show how the electromagnetic waves having a spread are transmitted from the transmitting antenna of the radar device 72, and how the reflected waves having a spread from a predetermined area are incident on the receiving antenna. The triangle is formed by solid lines and dashed lines, where the solid lines represent the predetermined area, and the dashed lines represent the spread of the electromagnetic waves. The signal processing device 82 generates information regarding the presence or absence of the vehicle 10 and speed information of the vehicle 10 based on the reflected waves generated by irradiating the vehicle 10 with electromagnetic waves. In this way, the radar sensor generates speed information of the vehicle 10 based on the reflected waves generated by irradiating the side or top surface of the vehicle body with electromagnetic waves.

[0183] In this specification, the "illumination area" of the radar device 72 refers to an area where the traveling vehicle 10 is illuminated with electromagnetic waves transmitted from the transmitting antenna of the radar device 72 and where the receiving antenna of the radar device 72 can receive the electromagnetic waves. The illumination area of ​​the radar device 72 may be referred to as the illumination area of ​​the radar sensor. The illumination area may include a flat or curved surface constituting the surface of the vehicle 10. When the signal processing device 82 trims the result of the spatial plot of the speed distribution based on the received signal, the area on the object side corresponding to the spatial plot after trimming may be the illumination area. Based on the result of the spatial plot of the distance and speed corresponding to the illumination area, speed information and information on the presence or absence of the vehicle 10 are generated.

[0184] When the irradiation area is sufficiently wide, more specifically, when it is sufficiently wide in the height direction of the vehicle 10, it becomes possible to stably receive the reflected wave from the vehicle body. In particular, when the irradiation area includes the entire vehicle body in the height direction of the vehicle 10, the irradiation area includes a larger portion of the vehicle body, so that it becomes possible to more stably receive the reflected wave from the vehicle body. In addition, even if the vehicle 10 has a gap, it is possible to more stably receive the reflected wave from the vehicle body. Furthermore, by using the radar device 72, it is possible to receive the reflected wave even if the vehicle 10 has a low reflectivity and / or a surface state close to that of a mirror, and it becomes possible to stably obtain information on the traveling speed of the vehicle 10.

[0185] In order to avoid detection of wheel rotation, the area above the top end of the wheel may be set as the illumination area.

[0186] The shortest distance from the radar device 72 to the nearest vehicle 10 may be, for example, 0.1 m or more and 10 m or less. The same applies to the shortest distance from the emission part of the FMCW-LiDAR sensor to the nearest vehicle 10.

[0187] Fig. 22 is a diagram showing an example of the arrangement of the radar device 72 and the emission unit 112a. Part (a) of Fig. 22 shows the side of the vehicle 10 to be measured. Part (b) of Fig. 22 shows the front of the vehicle 10. Part (c) of Fig. 22 shows the top surface of the vehicle 10.

[0188] The elliptical area shown in part (a) of FIG. 22 represents the irradiation area of ​​the radar device 72. The black dot in the center of the elliptical area represents the center 111b of the irradiation area. The elliptical area has a minor axis parallel to the road surface 90 and a major axis perpendicular to the road surface 90. The black dots shown in parts (b) and (c) of FIG. 22 represent the emission part 111a of the radar device 72. The angle θ1 shown in part (b) of FIG. 22 represents the angle between the irradiation direction of the electromagnetic wave transmitted from the radar device 72 and the first plane P1 parallel to the road surface 90. The angle θ2 of the beam shown in part (b) of FIG. 22 is the same as the angle θ of the beam in the first embodiment. The angle φ1 shown in part (c) of FIG. 22 represents the angle between the irradiation direction of the electromagnetic wave emitted from the radar device 72 and the second plane P2 perpendicular to the traveling direction. The angle Δφ shown in part (c) of FIG. 22 represents the angle seen from the radar device 72 in the minor axis direction of the irradiation area (elliptical area). This angle Δφ will be called the spread angle of the electromagnetic wave in the horizontal direction. Similarly, the angle seen from the radar device 72 in the major axis direction of the irradiation area (elliptical area) will be called the spread angle of the electromagnetic wave in the vertical direction. The beam angle φ2 shown in part (c) of FIG. 22 is the same as the beam angle φ in embodiment 1. The remaining reference symbols and coordinates shown in parts (a) to (c) of FIG. 22 are as described in embodiment 1.

[0189] In the embodiment, φ1>0, θ1=0. That is, the emission unit 111a emits electromagnetic waves in a direction parallel to the first plane P1 (i.e., parallel to the road surface 90) and obliquely incident on the side of the wheel from the front. The positive and negative signs of φ1 and θ1 are defined the same as those of φ2 and θ2.

[0190] The angle φ1 is greater than 0°, and may be, for example, 5° to 90°. This is because the radar device 72 measures the speed using the Doppler effect of the electromagnetic waves, and therefore there must be a relative speed between the direction of irradiation of the electromagnetic waves and the vehicle 10. Note that although the angle φ1 has a positive value in the second embodiment, it may also have a negative value.

[0191] In the second embodiment, for ease of understanding, as shown in part (a) of FIG. 22, when viewed from the side of the vehicle 10, the maximum range of the irradiation area of ​​the radar device 72 does not include the irradiation area of ​​the beam in the horizontal direction parallel to the road surface. In this case, the processing device 120 counts the rotating axles taking into consideration the time difference between the timing of speed measurement by the radar sensor and the FMCW-LiDAR sensor. In contrast, when the maximum range of the irradiation area of ​​the radar device 72 in the horizontal direction includes the irradiation area of ​​the beam, the processing device 120 does not need to count the rotating axles taking into consideration the above-mentioned time difference.

[0192] In the second embodiment, when the width of the irradiation area is narrower, the variation in the measured speed is reduced, so that the speed of the vehicle 10 can be measured with higher accuracy. The above-mentioned spread angle Δφ of the electromagnetic wave can be, for example, less than 10°. Furthermore, as described above, when the irradiation area is sufficiently wide in the height direction of the vehicle 10, the reflected wave from the vehicle body can be received more stably. Therefore, the spread of the electromagnetic wave is set so that the spread angle in the vertical direction is smaller than the spread angle in the horizontal direction.

[0193] The time changes in the speed of the vehicle 10 and the rotation speed of the wheels measured in the second embodiment are the same as those described in the first embodiment, except that a radar sensor is used instead of a camera sensor. The same is true for the operation of the processing device 120 in the second embodiment and the application example of the sensing system 100 in the second embodiment to ETC.

[0194] As described above, by measuring the speed of the vehicle 10 using a radar sensor, the speed of the vehicle 10 can be measured based on information from a wider area of ​​the vehicle body, and it becomes possible to more stably acquire information on the speed of the vehicle 10. Furthermore, by irradiating the wheels with a beam using an FMCW-LiDAR sensor, the rotational speed of the wheels can be measured independently of the speed of the vehicle 10.

[0195] <Embodiment 3> Next, a sensing system according to the third embodiment of the present disclosure will be described. Fig. 23 is a diagram showing yet another configuration example of the sensing system 100. The sensing system 100 shown in Fig. 23 differs from the sensing system 100 shown in Fig. 6 in that the first sensor 111 is an ultrasonic sensor rather than a camera sensor. The thick arrows shown in Fig. 23 represent the flow of ultrasonic waves, and the thin arrows shown in Fig. 23 represent the flow of signals.

[0196] The first sensor 111 is configured as an ultrasonic sensor including an ultrasonic device 74 and a signal processing device 84. The ultrasonic device 74 includes a transmitting unit that transmits ultrasonic waves for irradiating the side of the vehicle body, and a receiving unit that receives reflected waves resulting from the ultrasonic waves. Instead of the side of the vehicle body, the upper surface of the vehicle body may be irradiated with ultrasonic waves. The ultrasonic sensor is used to measure the speed of the vehicle 10. Therefore, the ultrasonic sensor functions as an ultrasonic speedometer. If the ultrasonic device 74 is capable of continuous measurement, it can measure the speed at a predetermined period, such as 1 / 30 seconds. The triangle and the thick arrow in FIG. 23 show how ultrasonic waves having a spread are transmitted from the transmitting unit of the ultrasonic device 74, and how reflected waves having a spread from a predetermined area are incident on the receiving unit. The triangle is formed by solid lines and dashed lines, and the solid lines represent the predetermined area, and the dashed lines represent the spread of the ultrasonic waves. The signal processing device 84 generates information regarding the presence or absence of the vehicle 10 and speed information of the vehicle 10 based on the reflected waves generated by irradiating the vehicle 10 with ultrasonic waves. In this way, the ultrasonic sensor functioning as an ultrasonic speedometer generates speed information of the vehicle 10 based on the reflected waves generated by irradiating the side or top surface of the vehicle body with ultrasonic waves.

[0197] In this specification, the "irradiation area" of the ultrasonic device 74 refers to an area where the traveling vehicle 10 is irradiated with ultrasonic waves transmitted from the transmitting section of the ultrasonic device 74 and where the receiving section of the ultrasonic device 74 can receive the ultrasonic waves. The irradiation area of ​​the ultrasonic device 74 may be referred to as the irradiation area of ​​the ultrasonic sensor. The irradiation area may include a flat or curved surface that constitutes the surface of the vehicle. When the signal processing device 84 trims the result of the spatial plot of the speed distribution based on the received signal, the area on the object side corresponding to the spatial plot after trimming may be the irradiation area. Speed ​​information and information on the presence or absence of the vehicle 10 are generated based on the result of the spatial plot of the distance and speed corresponding to the irradiation area.

[0198] When the irradiation area is sufficiently wide, more specifically, when it is sufficiently wide in the height direction of the vehicle 10, it becomes possible to stably receive the reflected wave from the vehicle body. In particular, when the irradiation area includes the entire vehicle body in the height direction of the vehicle 10, the irradiation area includes a larger portion of the vehicle body, so that it becomes possible to more stably receive the reflected wave from the vehicle body. In addition, even if the vehicle 10 has a gap, it is possible to more stably receive the reflected wave from the vehicle body. Furthermore, by using the ultrasonic device 74, it is possible to receive the reflected wave even if the vehicle 10 has a low reflectivity and / or a surface state close to that of a mirror, and it becomes possible to stably obtain information on the traveling speed of the vehicle 10.

[0199] In order to avoid detection of wheel rotation, the area above the top end of the wheel may be set as the illumination area.

[0200] The shortest distance from the ultrasonic device 74 to the nearest vehicle 10 may be, for example, 0.1 m to 10 m. The same is true for the shortest distance from the emission part of the FMCW-LiDAR sensor to the nearest vehicle 10.

[0201] Fig. 24 is a diagram showing an example of the arrangement of the ultrasonic device 74 and the emitter 112a. Part (a) of Fig. 24 shows the side of the vehicle 10 to be measured. Part (b) of Fig. 24 shows the front of the vehicle 10. Part (c) of Fig. 22 shows the top surface of the vehicle 10.

[0202] The elliptical area shown in part (a) of FIG. 24 represents the irradiation area of ​​the ultrasonic device 74. The black dot in the center of the elliptical area represents the center 111b of the irradiation area. The elliptical area has a minor axis parallel to the road surface 90 and a major axis perpendicular to the road surface 90. The black dots shown in parts (b) and (c) of FIG. 24 represent the emission unit 111a of the ultrasonic device 74. The angle θ1 shown in part (b) of FIG. 24 represents the angle between the irradiation direction of the ultrasonic wave transmitted from the ultrasonic device 74 and the first plane P1 parallel to the road surface 90. The angle θ2 of the beam shown in part (b) of FIG. 24 is the same as the angle θ of the beam in the first embodiment. The angle φ1 shown in part (c) of FIG. 24 represents the angle between the irradiation direction of the ultrasonic wave emitted from the ultrasonic device 74 and the second plane P2 perpendicular to the traveling direction. The angle Δφ shown in part (c) of FIG. 24 represents the angle of the minor axis direction of the irradiation area (elliptical area) seen from the ultrasonic device 74. This angle Δφ is referred to as the ultrasonic wave spread angle in the horizontal direction. Similarly, the angle seen from the ultrasonic device 74 in the long axis direction of the irradiation area (elliptical area) is referred to as the ultrasonic wave spread angle in the vertical direction. The beam angle φ2 shown in part (c) of FIG. 24 is the same as the beam angle φ in embodiment 1. The remaining reference symbols and coordinates shown in parts (a) to (c) of FIG. 24 are as explained in embodiment 1.

[0203] In the third embodiment, φ1>0, θ1=0. That is, the emitter 111a emits ultrasonic waves in a direction parallel to the first plane P1 (i.e., parallel to the road surface 90) and obliquely incident on the side of the wheel from the front. The positive and negative signs of φ1 and θ1 are defined the same as those of φ2 and θ2.

[0204] The angle φ1 is greater than 0°, and may be, for example, greater than or equal to 5° and less than or equal to 90°. This is because the ultrasonic device 74 measures the speed using the Doppler effect of ultrasonic waves, and therefore there must be a relative speed between the direction of ultrasonic radiation and the vehicle 10. Note that although the angle φ1 has a positive value in the third embodiment, it may also have a negative value.

[0205] In the third embodiment, when the width of the irradiation area is narrower, the variation in the measured speed is reduced, so that the speed of the vehicle 10 can be measured with higher accuracy. The above-mentioned spread angle Δφ of the ultrasonic waves can be, for example, less than 10°. Furthermore, as described above, when the irradiation area is sufficiently wide in the height direction of the vehicle 10, the reflected wave from the vehicle body can be received more stably. Therefore, the spread of the ultrasonic waves is set so that the spread angle in the vertical direction is larger than the spread angle in the horizontal direction.

[0206] In the third embodiment, for ease of understanding, as shown in part (a) of FIG. 24, when viewed from the side of the vehicle 10, the maximum range of the irradiation area of ​​the ultrasonic device 74 does not include the irradiation area of ​​the beam in the horizontal direction parallel to the road surface. In this case, the processing device 120 counts the rotating axles taking into account the time difference between the timing of speed measurement by the ultrasonic sensor and the FMCW-LiDAR sensor. On the other hand, when the maximum range of the irradiation area of ​​the ultrasonic device 74 in the horizontal direction includes the irradiation area of ​​the beam, the processing device 120 does not need to count the rotating axles taking into account the above-mentioned time difference.

[0207] The time changes in the speed of the vehicle 10 and the rotation speed of the wheels measured in the third embodiment are the same as those described in the first embodiment, except that an ultrasonic sensor is used instead of a camera sensor. The same is true for the operation of the processing device 120 in the third embodiment and the application example of the sensing system 100 in the third embodiment to ETC.

[0208] As described above, by measuring the speed of the vehicle 10 using an ultrasonic sensor, the speed of the vehicle 10 can be measured based on information from a wider area of ​​the vehicle body, and information on the traveling speed of the vehicle 10 can be acquired more stably. Furthermore, by irradiating the wheels with a beam using an FMCW-LiDAR sensor, the rotational speed of the wheels can be measured independently of the vehicle speed.

[0209] [Note] The above description of the embodiments discloses the following techniques.

[0210] [Technology 1] a sensor that measures a speed of a vehicle body of a vehicle traveling on a road to generate first speed information, the sensor being a camera sensor, a radar sensor, or an ultrasonic sensor; an FMCW-LiDAR sensor that measures a speed of the wheel based on a reflected light generated by irradiating a wheel of the vehicle with a beam and generates second speed information; a processing device that counts the rotating axles of the vehicle based on the first speed information and the second speed information to generate axle number information; Equipped with Measurement system.

[0211] This measurement system allows for improved accuracy in counting the rotating axles of a moving vehicle.

[0212] [Technology 2] the sensor is the camera sensor; The camera sensor generates the first speed information based on an image obtained by photographing a side or a top surface of the vehicle body. The measurement system described in Technology 1.

[0213] In this measurement system, the first velocity information can be generated by a camera sensor.

[0214] [Technology 3] The camera sensor photographs a side of the vehicle body, When viewed from the side of the vehicle, in a horizontal direction parallel to the road surface, the maximum range of the imaging area of ​​the camera sensor includes the irradiation area of ​​the beam. The measurement system described in Technique 2.

[0215] This measurement system does not require counting the rotating axles, taking into account the time difference between the speed measurements taken by the camera sensor and the FMCW-LiDAR sensor.

[0216] [Technology 4] The camera sensor photographs a side of the vehicle body, The imaging area of ​​the camera sensor includes the entire vehicle body in the height direction of the vehicle. The measurement system according to any one of claims 2 to 3.

[0217] This measurement system can extract more characteristic points of the vehicle body, making it possible to obtain information on the vehicle's traveling speed more reliably.

[0218] [Technology 5] the sensor is the radar sensor, The radar sensor generates the first speed information based on a reflected wave generated by irradiating a side or an upper surface of the vehicle body with an electromagnetic wave. The measurement system described in Technology 1.

[0219] In this measurement system, the first speed information can be generated by a radar sensor.

[0220] [Technology 6] The radar sensor irradiates a side surface of the vehicle body with the electromagnetic wave, When viewed from the side of the vehicle, the directions parallel to and perpendicular to the road surface are defined as horizontal and vertical directions, respectively. a spread angle of the electromagnetic wave in the vertical direction is greater than a spread angle of the electromagnetic wave in the horizontal direction; The measurement system described in technique 5.

[0221] In this measurement system, the spread angle of the electromagnetic waves in the horizontal direction is relatively small, so the vehicle speed can be measured with greater accuracy and less variation, and the spread angle of the electromagnetic waves in the vertical direction is relatively large, so the reflected waves from the vehicle body can be received more stably.

[0222] [Technology 7] The radar sensor irradiates a side surface of the vehicle body with the electromagnetic wave, When viewed from the side of the vehicle, in a horizontal direction parallel to a road surface of the road, a maximum range of an irradiation area of ​​the radar sensor includes an irradiation area of ​​the beam. The measurement system according to any one of claims 5 to 6.

[0223] This measurement system does not require counting the rotating axles, taking into account the time difference between the speed measurements by the radar sensor and the FMCW-LiDAR sensor.

[0224] [Technology 8] The radar sensor irradiates a side surface of the vehicle body with the electromagnetic wave, The irradiation area of ​​the radar sensor includes the entire vehicle body in the height direction of the vehicle. A measurement system according to any one of claims 5 to 7.

[0225] This measurement system can extract more characteristic points of the vehicle body, making it possible to obtain information on the vehicle's traveling speed more reliably.

[0226] [Technology 9] the sensor is an ultrasonic sensor, The ultrasonic sensor generates the first speed information based on a reflected wave generated by irradiating a side or a top surface of the vehicle body with an ultrasonic wave. The measurement system described in Technology 1.

[0227] In this measurement system, the first velocity information can be generated by an ultrasonic sensor.

[0228] [Technology 10] The ultrasonic sensor irradiates the side surface of the vehicle body with the ultrasonic wave, When viewed from the side of the vehicle, the directions parallel to and perpendicular to the road surface are defined as horizontal and vertical directions, respectively. A spread angle of the ultrasonic wave in the vertical direction is larger than a spread angle of the ultrasonic wave in the horizontal direction. The measurement system described in technique 9.

[0229] In this measurement system, the spread angle of the ultrasonic waves in the horizontal direction is relatively small, so the vehicle speed can be measured with high accuracy and little variation, and the spread angle of the ultrasonic waves in the vertical direction is relatively large, so the reflected waves from the vehicle body can be received more stably.

[0230] [Technology 11] The ultrasonic sensor irradiates the side surface of the vehicle body with the ultrasonic wave, When viewed from the side of the vehicle, in a horizontal direction parallel to the road surface, the maximum range of the irradiation area of ​​the ultrasonic sensor includes the irradiation area of ​​the beam. The measurement system according to any one of claims 9 to 10.

[0231] This measurement system does not require counting the rotating axles, taking into account the time difference between the speed measurements taken by the ultrasonic sensor and the FMCW-LiDAR sensor.

[0232] [Technology 12] The ultrasonic sensor irradiates the side surface of the vehicle body with the ultrasonic wave, The irradiation area of ​​the ultrasonic sensor includes the entire vehicle body in the height direction of the vehicle. A measurement system according to any one of claims 9 to 11.

[0233] This measurement system can extract more characteristic points of the vehicle body, making it possible to obtain information on the vehicle's traveling speed more reliably.

[0234] [Technology 13] The measurement system is connected to a host system, The host system displays information regarding the number of axles based on the axle number information. The measurement system according to any one of claims 1 to 9.

[0235] This measurement system can obtain information about the number of axles, such as toll fees, from a higher-level system. [Industrial Applicability]

[0236] The technology disclosed herein can be used, for example, in an apparatus or system that detects the rotating axles of a moving vehicle in a traffic infrastructure such as an ETC that uses FMCW-LiDAR technology. [Explanation of symbols]

[0237] 10 Vehicles 12 Body 14 wheels 20 light source 30 Interference Optical System 40 Photodetector 50 Beam shaper (output part) 60 Processing circuit 70 Camera 72 Radar Equipment 74 Ultrasonic device 80 Image processing device 82, 84 Signal processing device 62 Memory 90 Road surface 92 lanes 94 Island Gate 95 96, 97 Case 100 Sensing System 110 Sensors 111 First Sensor 111a Center of camera, emission part 111b Center of the photographed area, center of the irradiated area 112 Second Sensor 112a Beam output section 112b Beam irradiation point 120 Processing equipment 130 Storage device 140 Output Device

Claims

1. a sensor that measures a speed of a body of a vehicle traveling on a road and generates first speed information, the sensor being a camera sensor, a radar sensor, or an ultrasonic sensor; an FMCW-LiDAR sensor that measures the speed of the wheels based on reflected light generated by irradiating the wheels of the vehicle with a beam and generates second speed information; a processing device that counts the rotating axles of the vehicle based on the first speed information and the second speed information to generate axle number information; Equipped with Measurement system.

2. the sensor is the camera sensor; The camera sensor generates the first speed information based on an image obtained by photographing a side or a top surface of the vehicle body. The measurement system of claim 1 .

3. The camera sensor photographs a side of the vehicle body, When viewed from the side of the vehicle, in a horizontal direction parallel to the road surface, the maximum range of the imaging area of ​​the camera sensor includes the irradiation area of ​​the beam. The measurement system of claim 2 .

4. The camera sensor photographs a side of the vehicle body, The imaging area of ​​the camera sensor includes the entire vehicle body in the height direction of the vehicle. The measurement system according to claim 2 or 3.

5. the sensor is the radar sensor, The radar sensor generates the first speed information based on a reflected wave generated by irradiating a side or an upper surface of the vehicle body with an electromagnetic wave. The measurement system of claim 1 .

6. The radar sensor irradiates a side surface of the vehicle body with the electromagnetic wave, When viewed from the side of the vehicle, the directions parallel to and perpendicular to the road surface are defined as horizontal and vertical directions, respectively. a spread angle of the electromagnetic wave in the vertical direction is greater than a spread angle of the electromagnetic wave in the horizontal direction; The measurement system of claim 5 .

7. The radar sensor irradiates a side surface of the vehicle body with the electromagnetic wave, When viewed from the side of the vehicle, in a horizontal direction parallel to a road surface of the road, a maximum range of an irradiation area of ​​the radar sensor includes an irradiation area of ​​the beam. The measurement system according to claim 5 or 6.

8. The radar sensor irradiates a side surface of the vehicle body with the electromagnetic wave, The irradiation area of ​​the radar sensor includes the entire vehicle body in the height direction of the vehicle. The measurement system according to claim 5 or 6.

9. the sensor is an ultrasonic sensor, The ultrasonic sensor generates the first speed information based on a reflected wave generated by irradiating a side or an upper surface of the vehicle body with an ultrasonic wave. The measurement system of claim 1 .

10. The ultrasonic sensor irradiates the side surface of the vehicle body with the ultrasonic wave, When viewed from the side of the vehicle, the directions parallel to and perpendicular to the road surface are defined as horizontal and vertical directions, respectively. A spread angle of the ultrasonic wave in the vertical direction is larger than a spread angle of the ultrasonic wave in the horizontal direction. The measurement system of claim 9.

11. The ultrasonic sensor irradiates the side surface of the vehicle body with the ultrasonic wave, When viewed from the side of the vehicle, in a horizontal direction parallel to the road surface, the maximum range of the irradiation area of ​​the ultrasonic sensor includes the irradiation area of ​​the beam. The measurement system according to claim 9 or 10.

12. The ultrasonic sensor irradiates the side surface of the vehicle body with the ultrasonic wave, The irradiation area of ​​the ultrasonic sensor includes the entire vehicle body in the height direction of the vehicle. The measurement system according to claim 9 or 10.

13. The measurement system is connected to a host system, The host system displays information regarding the number of axles based on the axle number information.

10. The measurement system of claim 1, 2, 5, or 9.

Images