Positioning device, positioning method, and positioning program

Abstract

The objective is to provide a positioning device, a positioning method, and a positioning program that can accurately determine the relative position between a vehicle and a roadside unit with a simple configuration and a simple processing procedure when a vehicle passes a roadside unit. [Solution] When the Doppler measurement unit 20 receives a transmission signal from the roadside unit with the antenna 14, it measures the Doppler frequency and records the time of measurement. The relative position calculation unit 22 determines the change in the relative position of the vehicle as the vehicle moves and records the vehicle speed. The Doppler frequency correction unit 24 corrects the Doppler frequency to the value obtained by converting it to a reference vehicle speed, referring to the vehicle speed at the time of Doppler measurement. The roadside unit passage determination unit 26 determines whether the vehicle has passed in front of the roadside unit based on the measured Doppler frequency. The positioning calculation unit 28 uses the change in Doppler frequency before and after the passage of the roadside unit to determine the position of the roadside unit relative to the vehicle's travel trajectory.

Description

[Technical Field]

[0001] The present invention relates to a positioning device, a positioning method, and a positioning program. [Background Art]

[0002] For positioning using communication between roadside units of road-to-vehicle communication and vehicles, various methods have been studied as shown in Patent Documents 1 to 3 and Non-Patent Document 1.

[0003] Patent Document 1 discloses a communication system that specifies the position of a vehicle by disposing three antennas of a roadside unit at spaced intervals around a positioning area, obtaining the time difference of arrival when a transmission signal from an in-vehicle device is received by the three antennas of the roadside unit, and performing hyperbolic positioning based on the time difference of arrival.

[0004] Patent Document 2 discloses a position information generation system in which an in-vehicle device transmits a first signal to a first communication unit and a second communication unit of a roadside unit, receives second signals transmitted by the first communication unit and the second communication unit of the roadside unit, calculates a distance from the first communication unit of the roadside unit, calculates a distance from the second communication unit of the roadside unit, and specifies the intersection of circles or spheres centered on the positions of the first communication unit and the second communication unit as its own position to generate position information.

[0005] Patent Document 3 discloses a vehicle position estimation apparatus comprising: a vehicle position estimation unit that calculates a vehicle position based on an output from a sensor that detects behavior of the vehicle; a wireless position estimation unit that communicates with a radio device installed at an arbitrary position to calculate a relative position between the vehicle and the radio device; and a position estimation parameter correction unit that corrects parameters used for calculating at least vehicle position and turning angle information in the vehicle position estimation unit, wherein the position estimation parameter correction unit corrects the parameters by comparing a vehicle movement amount calculated by the wireless position estimation unit with a vehicle movement amount calculated by the vehicle position estimation unit.

[0006] Non-patent document 1 describes a procedure for simulating Doppler positioning by providing the orbit of the search satellite and the position of the signal transmission point, calculating the Doppler shift, adding the observation error to this, and inputting the resulting pseudo-observed value into the positioning program. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2008-292316 [Patent Document 2] Japanese Patent Publication No. 2009-198374 [Patent Document 3] Patent No. 7591463 [Non-patent literature]

[0008] [Non-Patent Document 1] Seiichiro Kawase, "Computer Simulation of Radio Source Positioning by Satellite Doppler Observation," Quarterly Report of the Radio Research Laboratory, vol. 31, No. 159, June 1985. [Overview of the project] [Problems that the invention aims to solve]

[0009] However, there is room for improvement in accurately determining the relative position between a vehicle and a roadside machine when a vehicle passes over it, using a simple configuration and simple processing procedure.

[0010] The purpose of this disclosure is to provide a positioning device, a positioning method, and a positioning program that can accurately determine the relative position between a vehicle and a roadside unit with a simple configuration and a simple processing procedure when a vehicle passes over the roadside unit. [Means for solving the problem]

[0011] To achieve the above objective, the positioning device according to the first embodiment comprises: an antenna provided on a vehicle to receive a transmission signal from a roadside unit installed on the roadside; a Doppler measurement unit that measures the Doppler frequency from the reception frequency when the antenna receives the transmission signal from the roadside unit; a relative position calculation unit that calculates the relative position of the vehicle from the vehicle speed; a roadside unit passage determination unit that determines whether or not the vehicle has passed the roadside unit based on the Doppler frequency measured by the Doppler measurement unit; and a positioning calculation unit that calculates the position of the roadside unit based on the change in the Doppler frequency before and after the vehicle has passed the roadside unit.

[0012] According to the first embodiment, the position of the roadside unit can be determined by measuring the Doppler frequency, calculating the relative position of the vehicle, and calculating the position of the roadside unit based on the change in Doppler frequency before and after the vehicle passes the roadside unit. Therefore, when a vehicle passes a roadside unit, the relative position between the vehicle and the roadside unit can be accurately determined with a simple configuration and a simple processing procedure.

[0013] The positioning device according to the second embodiment comprises: a plurality of antennas provided at a distance from the vehicle in the longitudinal direction and receiving transmission signals from a roadside unit installed on the roadside; a Doppler difference measurement unit that measures the difference in Doppler frequencies between each antenna from the reception frequencies when each antenna receives the transmission signals from the roadside unit; a relative position calculation unit that calculates the relative position of the vehicle from the vehicle speed; a roadside unit passage determination unit that determines whether or not the vehicle has passed the roadside unit based on the difference measured by the Doppler difference measurement unit; and a positioning calculation unit that calculates the position of the roadside unit based on the change in the difference before and after the vehicle has passed the roadside unit.

[0014] According to the second aspect, the position of the roadside unit can be specified by measuring the difference in Doppler frequency between a plurality of antennas, calculating the relative position of the vehicle, and calculating the position of the roadside unit based on a change in the difference before and after the vehicle passes the roadside unit. Therefore, when the vehicle passes the roadside unit, the relative position between the vehicle and the roadside unit can be obtained with high accuracy by a simple configuration and a simple processing procedure.

[0015] A positioning device according to a third aspect is the positioning device according to the first aspect, further comprising a Doppler frequency correction unit that corrects the Doppler frequency based on the vehicle speed.

[0016] According to the third aspect, the influence of vehicle speed during Doppler frequency measurement can be suppressed.

[0017] A positioning device according to a fourth aspect is the positioning device according to the third aspect, wherein the Doppler frequency correction unit invalidates the measured Doppler frequency when the vehicle speed is equal to or less than a predetermined threshold, and the positioning calculation unit calculates the position of the roadside unit using at least three or more valid measurement values before and after the vehicle passes the roadside unit.

[0018] According to the fourth aspect, the position of the roadside unit can be specified even when starting and stopping are repeated due to traffic congestion or the like.

[0019] A positioning device according to a fifth aspect is the positioning device according to the first aspect, wherein the relative position calculation unit calculates the travel distance of the vehicle by time-integrating a wheel speed.

[0020] According to the fifth aspect, the relative position of the vehicle can be calculated.

[0021] A positioning device according to a sixth aspect is the positioning device according to the first aspect, wherein the relative position calculation unit calculates the relative position of the vehicle by dead reckoning including at least one of turning of the vehicle and lane change.

[0022] According to the sixth aspect, the position of the roadside unit can be specified even when the vehicle does not travel straight.

[0023] In the positioning method according to the seventh aspect, a computer measures a Doppler frequency from a reception frequency obtained when an antenna provided on a vehicle receives a transmission signal from a roadside device installed on a roadside side, calculates a relative position of the vehicle from a vehicle speed of the vehicle, determines whether the vehicle has passed the roadside device based on the measured Doppler frequency, and performs a process of calculating a position of the roadside device based on a change in the Doppler frequency before and after the vehicle passes the roadside device.

[0024] According to the seventh aspect, the position of the roadside device can be specified by measuring the Doppler frequency, calculating the relative position of the vehicle, and calculating the position of the roadside device based on a change in the Doppler frequency before and after the vehicle passes the roadside device. Therefore, when the vehicle passes the roadside device, the relative position between the vehicle and the roadside device can be obtained with high accuracy through a simple configuration and a simple processing procedure.

[0025] In the positioning method according to the eighth aspect, a computer measures a difference in Doppler frequency between each of a plurality of antennas from reception frequencies obtained when the plurality of antennas, which are arranged spaced apart by a distance in a front-rear direction of a vehicle, respectively receive a transmission signal from a roadside device installed on a roadside side, calculates a relative position of the vehicle from a vehicle speed of the vehicle, determines whether the vehicle has passed the roadside device based on the measured difference, and performs a process of calculating a position of the roadside device based on a change in the difference before and after the vehicle passes the roadside device.

[0026] According to the eighth aspect, the position of the roadside device can be specified by measuring the difference in Doppler frequency between the plurality of antennas, calculating the relative position of the vehicle, and calculating the position of the roadside device based on a change in the difference before and after the vehicle passes the roadside device. Therefore, when the vehicle passes the roadside device, the relative position between the vehicle and the roadside device can be obtained with high accuracy through a simple configuration and a simple processing procedure.

[0027] The positioning program according to the ninth embodiment causes a computer to perform the following processes: measure the Doppler frequency from the reception frequency when an antenna installed on the vehicle receives a transmission signal from a roadside unit installed on the roadside; calculate the relative position of the vehicle from the vehicle speed; determine whether the vehicle has passed the roadside unit based on the measured Doppler frequency; and calculate the position of the roadside unit based on the change in the Doppler frequency before and after the vehicle has passed the roadside unit.

[0028] According to the ninth aspect, the position of the roadside unit can be determined by measuring the Doppler frequency, calculating the relative position of the vehicle, and calculating the position of the roadside unit based on the change in Doppler frequency before and after the vehicle passes the roadside unit. Therefore, when a vehicle passes a roadside unit, the relative position between the vehicle and the roadside unit can be accurately determined with a simple configuration and a simple processing procedure.

[0029] The positioning program according to the tenth embodiment causes a computer to perform the following processes: measure the difference in Doppler frequency between each of the antennas from the reception frequencies when a transmission signal from a roadside unit installed on the roadside is received by a plurality of antennas installed at a distance from the vehicle in the front-rear direction; calculate the relative position of the vehicle from the vehicle speed; determine whether the vehicle has passed the roadside unit based on the measured difference; and calculate the position of the roadside unit based on the change in the difference before and after the vehicle has passed the roadside unit.

[0030] According to the tenth embodiment, the position of the roadside unit can be determined by measuring the difference in Doppler frequencies between multiple antennas, calculating the relative position of the vehicle, and then calculating the position of the roadside unit based on the change in the difference before and after the vehicle passes the roadside unit. Therefore, when a vehicle passes a roadside unit, the relative position between the vehicle and the roadside unit can be accurately determined with a simple configuration and a simple processing procedure. [Effects of the Invention]

[0031] As described above, the present invention provides a positioning device, a positioning method, and a positioning program that can accurately determine the relative position between a vehicle and a roadside unit with a simple configuration and a simple processing procedure when a vehicle passes over the roadside unit. [Brief explanation of the drawing]

[0032] [Figure 1] This figure shows a schematic configuration of a vehicle equipped with a positioning device according to the first embodiment. [Figure 2] This is a block diagram showing a schematic configuration of a positioning device according to the first embodiment. [Figure 3] This is a functional block diagram showing the functional configuration of the positioning device according to the first embodiment. [Figure 4] This diagram shows a scene where a moving vehicle passes in front of a roadside machine. [Figure 5] This figure shows an example of the change in Doppler shift when a vehicle passes in front of a roadside device. [Figure 6] This flowchart shows an example of the processing flow performed by the positioning device according to the first embodiment. [Figure 7] This is a functional block diagram showing the functional configuration of the positioning device according to the second embodiment. [Figure 8] This diagram shows an example of a scene where a vehicle drives in front of and passes a roadside machine. [Figure 9] This diagram illustrates an example of the change in Doppler shift (Doppler frequency) with respect to the vehicle's position. [Figure 10] This figure shows an example of how the difference between these two Doppler shifts (Doppler difference) relative to the vehicle's position changes. [Figure 11] This diagram shows the relative positions of vehicles when they pass in front of a roadside unit. [Figure 12] This figure shows an example of calculating the change in Doppler difference when the vehicle speed and the distance to the roadside unit 18 are changed. [Figure 13] This flowchart shows an example of the processing flow performed by the positioning device according to the second embodiment. [Figure 14]This figure shows an example of the change in Doppler difference relative to the vehicle's position (extracting valid observations). [Figure 15] This figure shows an example of a case where there is a difference in height between the roadside unit and the vehicle's antenna. [Figure 16] This diagram shows an example where the antenna is located directly above the road. [Modes for carrying out the invention]

[0033] Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings. In this embodiment, a positioning device that determines the relative positional relationship between a roadside unit and a vehicle using road-to-vehicle communication will be described as an example.

[0034] (First Embodiment) Figure 1 is a diagram showing the schematic configuration of a vehicle equipped with a positioning device according to the first embodiment. Figure 2 is a block diagram showing the schematic configuration of the positioning device according to the first embodiment.

[0035] The positioning device 10 according to this embodiment is mounted on a vehicle 12 and is connected to an antenna provided on the vehicle 12.

[0036] Antenna 14 is provided for communication with roadside unit 18 installed next to the road. The installation location information of roadside unit 18 is assumed to be known.

[0037] As shown in Figure 2, the positioning device 10 according to this embodiment is composed of a general-purpose microcomputer including a CPU (Central Processing Unit) 10A, ROM (Read Only Memory) 10B, RAM (Random Access Memory) 10C, storage 10D, interface (I / F) 10E, and bus 10F.

[0038] The CPU 10A is the central processing unit, which executes various programs and controls various parts. Specifically, the CPU 10A reads programs from ROM 10B or storage 10D and executes them using RAM 10C as the working area. The CPU 10A performs various control and calculation processes according to the programs recorded in ROM 10B or storage 10D.

[0039] ROM 10B stores various programs and data. RAM 10C temporarily stores programs or data as a working area. Storage 10D is composed of an HDD (Hard Disk Drive) or SSD (Solid State Drive), etc., and stores various programs and data. In this embodiment, ROM 10B or storage 10D stores a positioning program that performs positioning calculations.

[0040] Antenna A14 and wheel speed sensor 16 are connected to I / F10E, and the signal from antenna 14 and the detection result of the wheel speed of the vehicle 12 detected by the wheel speed sensor 16 are input to the positioning device 10.

[0041] Next, the functional configuration of the positioning device 10 according to the first embodiment will be described. Figure 3 is a functional block diagram showing the functional configuration of the positioning device 10 according to this embodiment.

[0042] In this embodiment, the positioning device 10 has the functions of a Doppler measurement unit 20, a relative position calculation unit 22, a Doppler frequency correction unit 24, a roadside device passage determination unit 26, and a positioning calculation unit 28, which are performed by the CPU 10A loading a positioning program stored in ROM 10B or storage 10D into RAM 10C and executing it.

[0043] The Doppler measurement unit 20 measures the Doppler frequency from the reception frequency when the antenna 14 receives the transmission signal from the roadside unit 18.

[0044] The relative position calculation unit 22 calculates the relative position of the vehicle from the vehicle speed. For example, the relative position calculation unit 22 obtains the change in the relative position (distance traveled) of the vehicle 12 as the vehicle 12 moves by integrating the wheel speed detected by the wheel speed sensor 16.

[0045] The Doppler frequency correction unit 24 corrects the Doppler frequency based on the vehicle speed. For example, the Doppler frequency correction unit 24 refers to the vehicle speed at the time of Doppler measurement and corrects the Doppler frequency to the Doppler frequency when converted to a predetermined reference vehicle speed.

[0046] The roadside unit passage determination unit 26 determines whether or not the vehicle 12 has passed the roadside unit 18 based on the Doppler frequency measured by the Doppler measurement unit 20. For example, the roadside unit passage determination unit 26 determines whether or not the vehicle has passed in front of the roadside unit 18 based on the change in Doppler frequency.

[0047] The positioning calculation unit 28 calculates the position of the roadside unit 18 based on the change in Doppler frequency before and after the vehicle 12 passes the roadside unit 18. For example, the positioning calculation unit 28 calculates the position of the roadside unit 18 from the vehicle speed and Doppler frequency relative to the position of the vehicle 12. During the calculation, the change in Doppler frequency before and after the vehicle 12 passes near the roadside unit 18 is used to determine the position of the roadside unit 18 relative to the vehicle 12's travel trajectory.

[0048] Next, we will explain how the relative positional relationship between the roadside unit 18 and the vehicle 12 is determined by the positioning device 10 according to this embodiment. Figure 4 shows a scene in which a moving vehicle 12 passes in front of the roadside unit 18. Here, we consider the case where one antenna 14 is installed on the vehicle 12. The roadside unit 18 is installed next to the road, and the installation position information of the roadside unit 18 is known.

[0049] When vehicle 12 passes in front of roadside unit 18, the vehicle receives a signal transmitted from roadside unit 18, and a Doppler shift occurs in the received frequency due to the Doppler shift corresponding to the vehicle speed. Figure 5 shows an example of the Doppler shift (Doppler frequency) with respect to the position of vehicle 12. As shown in Figure 5, the frequency increases when vehicle 12 approaches roadside unit 18 and decreases when it moves away.

[0050] Consider a scenario where vehicle 12 travels in a straight line at speed v and passes in front of roadside unit 18. Let the direction of travel of vehicle 12 be the x-axis, and the width direction of vehicle 12 be the y-axis. Assume the vehicle travels along the x-axis where Y=0, and the front of roadside unit 18 is the origin of the x-axis. Let the coordinates of the installation position of roadside unit 18 be (0,Y), and the position of vehicle 12 be represented as (X,0).

[0051] At this time, using the direction θ of the roadside unit 18 as seen from the vehicle 12, the speed of movement of the roadside unit 18 in the direction seen from the vehicle 12 is given by vcosθ.

[0052] When a signal transmitted from the roadside unit 18 is received by the vehicle 12, a Doppler shift occurs as the vehicle 12 moves. Therefore, the frequency of the signal transmitted by the roadside unit 18 is f S Therefore, the frequency f of the received signal in vehicle 12 R The equation is as follows:

[0053]

number

[0054] The reason a minus sign is used for the vehicle speed here is that the direction of radio wave propagation and the direction of vehicle 12 movement are opposite. Also, C is the propagation speed of radio waves (speed of light). Doppler frequency (frequency shift due to Doppler shift) f D If we extract only that part, we get the following equation.

[0055]

number

[0056] Let x be the position of vehicle 12, and let the vehicle speed and direction be functions of position.

[0057]

number

[0058] As a result, the Doppler shift f is relative to the position x of vehicle 12. D Figure 5 illustrates this.

[0059] In this embodiment, when vehicle 12 enters the communication area of ​​roadside unit 18, an antenna 14 installed on vehicle 12 receives a signal transmitted from roadside unit 18. The Doppler frequency is determined by the vehicle speed and the direction from antenna 14 to roadside unit 18. The Doppler measurement unit 20 measures the Doppler frequency of the received signal and simultaneously records the time of measurement.

[0060] The relative position calculation unit 22 calculates the relative position change (distance traveled) of the vehicle 12 as it moves by integrating it with respect to the wheel speed. It calculates the relative position of the vehicle 12 at the measurement time and records the vehicle speed.

[0061] As vehicle 12 moves, its position changes, and the orientation of the roadside unit 18 as seen from antenna 14 also changes, causing the Doppler frequency to change. Therefore, the Doppler frequency is measured repeatedly, and the measurement time, vehicle speed, and relative position are all recorded.

[0062] The Doppler frequency correction unit 24 refers to the vehicle speed at the time of Doppler measurement and corrects the Doppler frequency to the Doppler frequency when converted to a reference vehicle speed. The reference vehicle speed can be set to any value, so it may be the vehicle speed when entering the communication area, or the average vehicle speed when passing through the communication area. Alternatively, it may be set in advance based on the speed limit of the road where the roadside unit 18 is installed.

[0063] Specifically, since the Doppler frequency is proportional to the vehicle speed v(x), if the reference vehicle speed is V0, multiplying by the coefficient v0 / v(x) allows the Doppler frequency to be corrected to that of a vehicle traveling at the reference vehicle speed, regardless of the vehicle's position.

[0064]

number

[0065] The roadside unit passage determination unit 26 determines whether or not the vehicle has passed in front of the roadside unit 18 based on the change in Doppler frequency. As shown in Figure 5, the point where the slope of the Doppler frequency change with respect to the position of the vehicle 12 is maximum corresponds to the point when the vehicle has passed in front of the roadside unit 18. Therefore, if the slope of the Doppler frequency increases, it can be determined that the vehicle has not yet passed the roadside unit 18, and if the slope decreases, it can be determined that the vehicle has already passed the roadside unit 18.

[0066] The positioning calculation unit 28 uses the change in Doppler frequency before and after the passage of the roadside unit 18 to determine the position of the roadside unit 18 relative to the vehicle 12's travel trajectory. Since the slope of the Doppler frequency change takes its maximum value when the vehicle passes directly in front of the roadside unit 18, the longitudinal position of the vehicle 12 at that point on the travel trajectory is determined to be directly in front of the roadside unit 18. Furthermore, since the slope of the Doppler frequency at the point determined to be directly in front is determined by the reference vehicle speed and the distance to the roadside unit 18 at the time of passage, the slope of the vehicle 12's position when x=0 is directly in front of the roadside unit 18 is given by the following equation.

[0067]

number

[0068] From the above, we can determine the distance Y from the vehicle 12 to the roadside unit 18, which corresponds to the lateral position of the vehicle 12 when it passes the roadside unit 18 head-on along the vehicle's trajectory.

[0069] This allows us to determine the lateral distance of the vehicle 12 to the roadside unit 18 when it passes by, making it possible to identify the lane the vehicle is traveling in, for example, when traveling on a multi-lane road. Furthermore, the position of the travel trajectory can be corrected based on the installation location information of the roadside unit 18.

[0070] Next, we will describe the specific processing performed by the positioning device 10 according to this embodiment, which is configured as described above. Figure 6 is a flowchart showing an example of the processing flow performed by the positioning device 10 according to this embodiment. Note that the processing in Figure 6 starts, for example, when a vehicle 12 enters the communication area of ​​the roadside unit 18 and the antenna 14 receives a transmission signal from the roadside unit 18.

[0071] In step 100, the CPU 10A measures the Doppler frequency and proceeds to step 102. Specifically, the Doppler measurement unit 20 measures the measurement time and the frequency of the received signal, calculates the Doppler frequency, and stores it.

[0072] In step 102, the CPU 10A acquires the vehicle speed, calculates the distance traveled, and proceeds to step 104. Specifically, the relative position calculation unit 22 acquires and stores the wheel speed as an example of vehicle speed from the wheel speed sensor 16, and calculates the distance traveled by the vehicle 12 by integrating the wheel speed.

[0073] In step 104, the CPU 10A corrects the Doppler frequency and proceeds to step 106. Specifically, the Doppler frequency correction unit 24 corrects the Doppler value converted from the Doppler frequency measured by the Doppler measurement unit 20 and the vehicle speed to a reference vehicle speed.

[0074] In step 106, the CPU 10A performs a roadside device pass detection and proceeds to step 108. Specifically, the roadside device pass detection unit 26 determines whether the vehicle 12 has passed the roadside device 18 based on the change (slope) of the Doppler frequency with respect to the distance traveled by the vehicle speed.

[0075] In step 108, the CPU 10A determines whether the measurement was taken before or after the passage of the roadside unit 18. If this determination is denied, the process returns to step 100 and the above process is repeated. If the determination is affirmative, the process proceeds to step 110. In other words, the above process is repeated until measurement values ​​before and after the passage of the roadside unit 18 can be obtained.

[0076] In step 110, the CPU 10A performs positioning calculations and completes the series of processes. Specifically, the positioning calculation unit 28 determines the longitudinal position of the vehicle 12 from the time when the change (slope) of the Doppler frequency is at its maximum, thereby determining whether the longitudinal position of the vehicle 12 is directly in front of the roadside unit 18. It also determines the lateral position (distance) from the maximum value of the change (slope) of the Doppler frequency.

[0077] By performing this process, the position of the roadside unit 18 relative to the vehicle 12's travel trajectory can be accurately determined with a simple configuration of one roadside unit 18 and one antenna 14 on the vehicle 12, and with a simple processing procedure.

[0078] In this embodiment, a Doppler frequency correction unit 24 is provided to correct the Doppler frequency due to vehicle speed, but the Doppler frequency correction unit 24 may be omitted.

[0079] (Second Embodiment) Next, the functional configuration of the positioning device 10 according to the second embodiment will be described. Figure 7 is a functional block diagram showing the functional configuration of the positioning device 10 according to the second embodiment.

[0080] In this embodiment, compared to the first embodiment, the vehicle 12 is equipped with two antennas (antenna A14A, antenna 14B) 14. In addition, the Doppler measurement unit 20 is replaced with a Doppler difference measurement unit 21.

[0081] The Doppler difference measurement unit 21 measures the difference in Doppler shift between each antenna 14 from the reception frequencies when each antenna 14 receives the transmission signal from the roadside unit 18.

[0082] Here, we consider the case where the antennas 14 of vehicle 12 are installed at a distance from vehicle 12 in the front-to-back direction. Figure 8 shows a scene in which vehicle 12 drives in front of and passes roadside unit 18. Figure 9 shows the change in Doppler shift (Doppler frequency) with respect to the position of vehicle 12. It can be seen that the change in Doppler shift is shifted with respect to the position of vehicle 12 because the two antennas 14 are offset in the front-to-back direction. Figure 10 shows the change in the difference between these two Doppler shifts (Doppler difference) with respect to the position of vehicle 12. It can be seen that the Doppler difference reaches its peak value when passing directly in front of roadside unit 18.

[0083] Next, a method for determining the relative positional relationship between the roadside unit 18 and the vehicle 12 using the positioning device 10 according to this embodiment will be described.

[0084] The difference from the first embodiment is that when the position of the vehicle 12 is x=X, the positions X1 and X2 of the two antennas 14 are given by the following equations using the distance d between the antennas.

[0085]

number

[0086] Since the azimuth θ1 from antenna A14A to roadside unit 18 and the azimuth θ2 from antenna B14B to roadside unit 18 are different, the Doppler frequency f of the received signal at each antenna 14 corresponds to the difference in azimuth. D1 ,f D2 A difference arises. This frequency difference f DD The Doppler difference measurement unit 21 measures this value and simultaneously records the time of measurement.

[0087]

number

[0088] The roadside machine passage determination unit 26 determines whether or not the vehicle has passed in front of the roadside machine 18 based on the change in Doppler difference. As shown in Figure 10, the Doppler difference increases before the vehicle passes the roadside machine 18 and decreases after the vehicle passes the roadside machine 18. Therefore, the change in Doppler difference reaches its maximum and peaks when the vehicle passes in front of the roadside machine 18. Thus, it is possible to determine whether or not the vehicle has passed the roadside machine 18.

[0089] The positioning calculation unit 28 uses the change in the Doppler difference between the two antennas 14 before and after the roadside unit 18 passes to determine the position of the roadside unit 18 relative to the vehicle's trajectory. Since the Doppler difference reaches its peak value when the vehicle passes directly in front of the roadside unit 18, the forward and backward position of the vehicle 12 at the point where the peak value occurs is considered to be the front of the roadside unit 18. The peak value of the Doppler difference at that point is determined by the vehicle speed, the distance between the antennas 14, and the distance to the roadside unit 18 at the time of passing, and is given by the following equation.

[0090]

number

[0091] Here, θ0 is the direction from each antenna 14 to the roadside unit 18 when the vehicle 12 passes in front of the roadside unit 18. Figure 11 shows the positional relationship when the vehicle 12 passes in front of the roadside unit 18.

[0092] Figure 12 also shows an example of calculating the change in Doppler difference when the vehicle speed and the distance to the roadside unit 18 are changed. It can be seen that the peak value of the Doppler difference is proportional to the vehicle speed and roughly inversely proportional to the distance to the roadside unit 18. Although not shown in the figure, it is also roughly inversely proportional to the distance between the antennas 14. Therefore, the lateral position of the vehicle 12 (distance to the roadside unit 18 when passing) can be determined from the peak value, vehicle speed, and the distance between the antennas 14.

[0093] From the above, the position of the roadside unit 18 when the vehicle 12 passes directly in front of it and the relative position of the vehicle 12 to the roadside unit 18 can be determined.

[0094] In this embodiment, since the Doppler difference between receiving antennas is determined based on the transmitted signal from the same roadside unit 18, the influence of the receiver's frequency stability is reduced, and the Doppler effect can be measured with greater accuracy. As a result, the lateral distance of the vehicle 12 to the roadside unit 18 when it passes by can be determined, so for example, when driving on a multi-lane road, the lane being traveled in can be identified. In addition, the position of the driving trajectory can be corrected based on the installation position information of the roadside unit 18.

[0095] Next, we will describe the specific processing performed by the positioning device 10 according to this embodiment, which is configured as described above. Figure 13 is a flowchart showing an example of the processing flow performed by the positioning device 10 according to the second embodiment. Note that the processing in Figure 13 starts, for example, when a vehicle 12 enters the communication area of ​​the roadside unit 18 and the antenna 14 receives a transmission signal from the roadside unit 18.

[0096] In step 200, the CPU 10A measures the Doppler difference and proceeds to step 202. Specifically, the Doppler difference measurement unit 21 measures the measurement time and the frequency of the received signal, calculates the difference in Doppler frequencies between the antennas 14, and stores it.

[0097] In step 202, the CPU 10A acquires the vehicle speed, calculates the distance traveled, and proceeds to step 204. Specifically, the relative position calculation unit 22 acquires and stores the vehicle speed at the time of Doppler difference measurement from the wheel speed sensor 16, and calculates the distance traveled by the vehicle 12 by integrating the wheel speed.

[0098] In step 204, the CPU 10A corrects the Doppler difference and proceeds to step 206. Specifically, the Doppler frequency correction unit 24 corrects the Doppler difference from the measured Doppler difference and vehicle speed to a Doppler difference converted to a reference vehicle speed.

[0099] In step 206, the CPU 10A performs a roadside device pass detection and proceeds to step 208. Specifically, the roadside device pass detection unit 26 determines whether the vehicle 12 has passed the roadside device 18 based on the change (slope) of the Doppler frequency with respect to the distance traveled by the vehicle speed.

[0100] In step 208, the CPU 10A determines whether the measurement was taken before or after the passage of the roadside unit 18. If this determination is denied, the process returns to step 200 and the above process is repeated. If the determination is affirmative, the process proceeds to step 210. In other words, the above process is repeated until measurement values ​​before and after the passage of the roadside unit 18 can be obtained.

[0101] In step 210, the positioning calculation is performed to complete the series of processes. Specifically, the positioning calculation unit 28 determines the longitudinal position of the vehicle 12 from the time when the Doppler difference is maximum, thereby determining whether the longitudinal position of the vehicle 12 is directly in front of the roadside unit 18. It also determines the lateral position (distance) from the maximum value of the Doppler difference.

[0102] Even with this processing method, the position of the roadside unit 18 relative to the vehicle 12's travel trajectory can be accurately determined with a simple configuration of one roadside unit 18 and one antenna 14 on the vehicle 12, and with a simple processing procedure.

[0103] (Third embodiment) In each of the embodiments described above, since Doppler is used, it is assumed that the vehicle passes near the roadside unit 18 at a certain speed or higher. Furthermore, in the descriptions of the roadside unit passage determination unit 26 and the positioning calculation unit 28 in each embodiment, the vehicle speed before and after passing the roadside unit 18 is assumed to be constant, or the Doppler frequency is corrected by converting it to a reference vehicle speed. However, depending on the traffic conditions, the vehicle speed may decrease significantly or the vehicle may come to a stop.

[0104] When vehicle 12 is stopped, no Doppler shift occurs. Also, if the vehicle speed decreases significantly, the Doppler shift itself becomes smaller in proportion to the decrease in vehicle speed, which may make it difficult to detect.

[0105] Therefore, in this embodiment, in the processing described above, the Doppler observation value is invalidated when the vehicle speed falls below a predetermined threshold (for example, 1 m / s).

[0106] Disabling Doppler observations results in gaps in the observation data when the vehicle speed is extremely low. However, because the speed is so low, the distance traveled by vehicle 12 is also short. Therefore, even with long stopping times, the gaps are limited when observing changes in the Doppler difference relative to the position of vehicle 12. Thus, the gaps can be interpolated from data where Doppler observations were valid, and the same processing can be performed.

[0107] If the number of valid Doppler frequency measurements is limited due to a decrease in vehicle speed, etc., it is possible to determine whether the vehicle has passed in front of the roadside device 18 if there is a change in increase or decrease using at least three or more Doppler difference values ​​or Doppler derivative values. Therefore, as shown in Figure 14, it is sufficient to have at least one valid Doppler measurement value before and after the passage of the roadside device 18, and at least three or more valid Doppler measurements in total. Figure 14 shows an example of the change in Doppler difference with respect to the vehicle's position (extraction of valid observed values).

[0108] Furthermore, positioning calculations can be performed by fitting the Doppler difference or Doppler derivative (slope) formula to the measured values. The transmission frequency of the roadside unit 18, the reference vehicle speed, and the distance between the antennas 14 are known from the Doppler difference or Doppler derivative formula for the position of the vehicle 12. If the longitudinal position of the vehicle 12 and the distance Y to the roadside unit 18, which are the desired X=0 values ​​for positioning calculations, can be determined, the position can be identified. Therefore, the X and Y values ​​should be searched to best match the Doppler difference values ​​of three or more measurement results.

[0109] Furthermore, in the case of a single antenna 14 as in the first embodiment, the time derivative of the Doppler frequency is used, while in the case of two antennas 14 spaced apart as in the second embodiment, the Doppler difference (which can also be called the spatial derivative) is used. Therefore, both methods may be used in combination. By combining them, an improvement in positional accuracy can be expected.

[0110] Furthermore, in each of the above embodiments, when the relative position calculation unit 22 determines the relative position change accompanying the movement of the vehicle 12, it assumes that the vehicle 12 is traveling in a straight line and uses the distance traveled. As can be seen from Figures 5, 9, and 10, the Doppler frequency changes significantly, or the Doppler difference becomes large, only in a section of at most a few tens of meters before and after the vehicle 12 passes near the roadside unit 18, and this method is intended to be implemented in this section. In particular, in normal traffic conditions on expressways and motorways, the vehicle passes this section near the roadside unit 18 within a few seconds, so in most cases it is not a problem to approximate it as straight-line driving. If approximation as straight-line driving is not possible, by adding sensors that detect the state of the vehicle, such as a gyro sensor or an acceleration sensor, the relative position calculation unit 22 can calculate the relative position of the vehicle 12 by dead reckoning, which includes at least one of the vehicle's turning (change of direction) and lane changes, and determine the driving trajectory, and this method can be applied in many cases.

[0111] Furthermore, although the above embodiments are described using two-dimensional positioning on a plane, the antenna of the roadside unit 18 is generally installed at a higher position than the antenna 14 of the vehicle 12. If the antenna height is known in advance, the lateral position of the roadside unit 18 when it passes can be corrected from the difference in height between the roadside unit 18 and the antenna.

[0112] For example, Figure 15 shows the case where there is a difference in height between the roadside unit 18 and the vehicle 12's antennas. The distance between the roadside unit 18 and the vehicle 12 as determined in each embodiment is the distance of the straight line connecting the roadside unit 18 and the vehicle 12's antenna 14 in the figure. For example, if the distance from the roadside unit 18 is 10m and the difference in antenna height is 8m, the lateral distance from the roadside unit 18 to the vehicle can be calculated as 8m.

[0113] Furthermore, each embodiment is applicable even if the antenna of the roadside unit 18 is directly above the road, as shown in Figure 16. Since the distance to the nearest point of passage to the roadside unit 18 is known, if the height of the antenna is known, it is possible to determine whether the vehicle passed through the lane directly below the roadside unit 18 or an adjacent lane by comparing the distances. Figure 16 shows an example where the antenna 14 is directly above the road.

[0114] In the above embodiment, a CPU was given as an example of a processor, but the term "processor" refers to a broader type of processor, including general-purpose processors (such as CPUs) and specialized processors (such as GPUs: Graphics Processing Units, ASICs: Application Specific Integrated Circuits, FPGAs: Field Programmable Gate Arrays, and programmable logic devices).

[0115] Furthermore, the operation of the processor in the above embodiments may not be performed by a single processor, but may be performed by multiple processors located in physically separate locations working together. Also, the order of the processor operations is not limited to the order described in each of the above embodiments, but may be changed as appropriate.

[0116] Furthermore, the processing performed by the positioning device 10 according to the above embodiment may be software-based processing, hardware-based processing, or a combination of both.

[0117] The program of this application can be provided as a program product. A program product includes any form of product for providing a program. For example, a program product includes a program provided via a network such as the Internet, and non-temporary computer-readable recording media such as CD-ROMs and DVDs on which the program is stored.

[0118] Furthermore, the present invention is not limited to the above, and it is of course possible to implement it in various modified forms without departing from its spirit.

[0119] This disclosure may adopt the following embodiments: (1) An antenna installed on the vehicle to receive transmission signals from a roadside unit mounted on the roadside, A Doppler measurement unit measures the Doppler frequency from the reception frequency at which the antenna receives the transmission signal from the roadside unit, A relative position calculation unit that calculates the relative position of the vehicle from the vehicle speed of the vehicle, A roadside device passage determination unit determines whether or not the vehicle has passed the roadside device based on the Doppler frequency measured by the Doppler measurement unit, A positioning calculation unit that calculates the position of the roadside unit based on the change in the Doppler frequency before and after the vehicle passes the roadside unit, A positioning device equipped with the following features.

[0120] (2) Multiple antennas are provided, spaced apart in the front-to-rear direction of the vehicle, to receive transmission signals from roadside units installed on the roadside. A Doppler difference measuring unit measures the difference in Doppler frequencies between each antenna from the reception frequencies when each of the antennas receives the transmission signal from the roadside unit, A relative position calculation unit that calculates the relative position of the vehicle from the vehicle speed of the vehicle, A roadside device passage determination unit determines whether or not the vehicle has passed the roadside device based on the difference measured by the Doppler difference measurement unit, A positioning calculation unit calculates the position of the roadside unit based on the difference in change before and after the vehicle passes the roadside unit, A positioning device equipped with the following features.

[0121] (3) The positioning device according to (1) or (2), further comprising a Doppler frequency correction unit that corrects the Doppler frequency based on the vehicle speed.

[0122] (4) The Doppler frequency correction unit invalidates the measured Doppler frequency if the vehicle speed is below a predetermined threshold. The positioning device according to (3), wherein the positioning calculation unit calculates the position of the roadside unit using at least three or more valid measurement values ​​before and after the vehicle passes the roadside unit.

[0123] (5) The positioning device according to any one of (1) to (3), wherein the relative position calculation unit calculates the distance traveled by the vehicle by integrating the wheel speed over time.

[0124] (6) The positioning device according to any one of (1) to (5), wherein the relative position calculation unit calculates the relative position of the vehicle by dead reckoning, which includes at least one of the vehicle turning and lane changes.

[0125] (7) Computers The Doppler frequency is measured from the reception frequency when an antenna on the vehicle receives a transmission signal from a roadside unit installed on the roadside. The relative position of the vehicle is calculated from the vehicle speed of the vehicle. Based on the measured Doppler frequency, it is determined whether the vehicle has passed the roadside unit. A positioning method that performs a process of calculating the position of the roadside unit based on the change in the Doppler frequency before and after the vehicle passes the roadside unit.

[0126] (8) Computers The difference in Doppler frequency between each of the antennas is measured from the reception frequencies when the transmission signal from a roadside unit installed on the roadside is received by multiple antennas installed at a distance from each other in the front-rear direction of the vehicle. The relative position of the vehicle is calculated from the vehicle speed of the vehicle. Based on the measured difference, it is determined whether the vehicle has passed the roadside machine. A positioning method that performs a process of calculating the position of the roadside unit based on the difference change before and after the vehicle passes the roadside unit.

[0127] (9) On the computer, The Doppler frequency is measured from the reception frequency when an antenna on the vehicle receives a transmission signal from a roadside unit installed on the roadside. The relative position of the vehicle is calculated from the vehicle speed of the vehicle. Based on the measured Doppler frequency, it is determined whether the vehicle has passed the roadside unit. A positioning program for causing the vehicle to perform a process to calculate the position of the roadside unit based on the change in the Doppler frequency before and after the vehicle passes the roadside unit.

[0128] (10) On the computer, The difference in Doppler frequency between each of the antennas is measured from the reception frequencies when the transmission signal from a roadside unit installed on the roadside is received by multiple antennas installed at a distance from each other in the front-rear direction of the vehicle. The relative position of the vehicle is calculated from the vehicle speed of the vehicle. Based on the measured difference, it is determined whether the vehicle has passed the roadside machine. A positioning program for causing the vehicle to perform a process to calculate the position of the roadside unit based on the difference in change before and after the vehicle passes the roadside unit. [Explanation of Symbols]

[0129] 10 Positioning device 12 vehicles 14 Antennas 14A Antenna A 14B Antenna B 16 Wheel speed sensor 18 Roadside unit 20 Doppler measurement unit 21 Doppler difference measurement unit 22 Relative position calculation unit 24 Doppler frequency correction section 26 Roadside machine passage determination section 28 Positioning Calculation Unit

Claims

1. An antenna installed on the vehicle to receive transmission signals from a roadside unit mounted on the roadside, A Doppler measurement unit measures the Doppler frequency from the reception frequency at which the antenna receives the transmission signal from the roadside unit, A relative position calculation unit that calculates the relative position of the vehicle from the vehicle speed of the vehicle, A roadside device passage determination unit determines whether or not the vehicle has passed the roadside device based on the Doppler frequency measured by the Doppler measurement unit, A positioning calculation unit that calculates the position of the roadside unit based on the change in the Doppler frequency before and after the vehicle passes the roadside unit, A positioning device equipped with the following features.

2. Multiple antennas are provided, spaced apart in the front-to-rear direction of the vehicle, to receive transmission signals from roadside units installed on the roadside. A Doppler difference measuring unit measures the difference in Doppler frequencies between each antenna from the reception frequencies when each of the antennas receives the transmission signal from the roadside unit, A relative position calculation unit that calculates the relative position of the vehicle from the vehicle speed of the vehicle, A roadside device passage determination unit determines whether or not the vehicle has passed the roadside device based on the difference measured by the Doppler difference measurement unit, A positioning calculation unit calculates the position of the roadside unit based on the difference in change before and after the vehicle passes the roadside unit, A positioning device equipped with the following features.

3. The positioning device according to claim 1, further comprising a Doppler frequency correction unit that corrects the Doppler frequency based on the vehicle speed.

4. The Doppler frequency correction unit invalidates the measured Doppler frequency if the vehicle speed is below a predetermined threshold. The positioning device according to claim 3, wherein the positioning calculation unit calculates the position of the roadside unit using at least three or more valid measurement values ​​before and after the vehicle passes the roadside unit.

5. The positioning device according to claim 1, wherein the relative position calculation unit calculates the distance traveled by the vehicle by integrating the wheel speed over time.

6. The positioning device according to claim 1, wherein the relative position calculation unit calculates the relative position of the vehicle by dead reckoning, which includes at least one of the vehicle turning and lane changes.

7. Computers The Doppler frequency is measured from the reception frequency when an antenna on the vehicle receives a transmission signal from a roadside unit installed on the roadside. The relative position of the vehicle is calculated from the vehicle speed of the vehicle. Based on the measured Doppler frequency, it is determined whether the vehicle has passed the roadside unit. A positioning method that performs a process of calculating the position of the roadside unit based on the change in the Doppler frequency before and after the vehicle passes the roadside unit.

8. Computers The difference in Doppler frequency between each of the antennas is measured from the reception frequencies when a transmission signal from a roadside unit installed on the roadside is received by multiple antennas installed at a distance from each other in the front-rear direction of the vehicle. The relative position of the vehicle is calculated from the vehicle speed of the vehicle. Based on the measured difference, it is determined whether the vehicle has passed the roadside machine. A positioning method that performs a process of calculating the position of the roadside unit based on the difference change before and after the vehicle passes the roadside unit.

9. On the computer, The Doppler frequency is measured from the reception frequency when an antenna on the vehicle receives a transmission signal from a roadside unit installed on the roadside. The relative position of the vehicle is calculated from the vehicle speed of the vehicle. Based on the measured Doppler frequency, it is determined whether the vehicle has passed the roadside unit. A positioning program for causing the vehicle to perform a process to calculate the position of the roadside unit based on the change in the Doppler frequency before and after the vehicle passes the roadside unit.

10. On the computer, The difference in Doppler frequency between each of the antennas is measured from the reception frequencies when a transmission signal from a roadside unit installed on the roadside is received by multiple antennas installed at a distance from each other in the front-rear direction of the vehicle. The relative position of the vehicle is calculated from the vehicle speed of the vehicle. Based on the measured difference, it is determined whether the vehicle has passed the roadside machine. A positioning program for causing the vehicle to perform a process to calculate the position of the roadside unit based on the difference in change before and after the vehicle passes the roadside unit.

Images