Positioning device, positioning method, and positioning program

Abstract

When a Doppler measurement unit (20) receives a transmission signal from a roadside device by means of an antenna (14), the Doppler measurement unit (20) measures a Doppler frequency and records the measured time, a relative position calculation unit (22) determines a change in the relative position of a vehicle accompanying travel by the vehicle and records the vehicle speed, a Doppler frequency correction unit (24) refers to the vehicle speed during Doppler measurement and corrects the Doppler frequency to a Doppler frequency converted for a reference vehicle speed, a roadside device passage determination unit (26) determines whether the vehicle has passed the front surface of the roadside device on the basis of the measured Doppler frequency, and a positioning calculation unit (28) identifies the position of the roadside device with respect to the travel path of the vehicle using the change in the Doppler frequency before and after passage of the roadside device.

Description

Positioning device, positioning method, and positioning program Cross-reference of related applications

[0001] This application is based on Japanese Patent Application No. 2025-30611, filed in Japan on February 27, 2025, and incorporates the contents of the basic application by reference in whole.

[0002] This disclosure relates to a positioning device, a positioning method, and a positioning program.

[0003] Various methods have been considered for positioning using communication between roadside units and vehicles in vehicle-to-infrastructure communication, as described in Patent Documents 1-3 and Non-Patent Document 1.

[0004] Patent Document 1 discloses a communication system that determines the vehicle's position by installing three roadside antennas at a distance from each other around the positioning area, determining the difference in arrival time when a signal transmitted from an in-vehicle unit is received by the three roadside antennas, and performing hyperbolic positioning from the arrival time difference.

[0005] Patent Document 2 discloses a location information generation system in which an in-vehicle unit transmits a first signal to the first and second communication units of a roadside unit, and receives a second signal transmitted by the first and second communication units of the roadside unit. The system then calculates the distance from the first communication unit of the in-vehicle unit to the second communication unit, identifies the intersection of a circle or sphere centered on the positions of the first and second communication units as its own position, and generates location information.

[0006] Patent Document 3 discloses a vehicle position estimation device comprising: a vehicle position estimation unit that calculates the position of a vehicle based on the output of a sensor that detects the behavior of the vehicle; a wireless position estimation unit that calculates the relative position of the vehicle and the wireless unit by communicating with a wireless unit installed at an arbitrary position; and a position estimation parameter correction unit that corrects parameters used by the vehicle position estimation unit to calculate at least the vehicle's position and turning angle information, wherein the position estimation parameter correction unit corrects the parameters by comparing the amount of vehicle movement calculated by the wireless position estimation unit with the amount of vehicle movement calculated by the vehicle position estimation unit.

[0007] 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.

[0008] Japanese Patent Publication No. 2008-292316, Japanese Patent Publication No. 2009-198374, Japanese Patent No. 7591463

[0009] Seiichiro Kawase, "Computer Simulation of Radio Source Positioning by Satellite Doppler Observation," Quarterly Reports of the Radio Research Laboratory, vol. 31, No. 159, June 1985.

[0010] 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.

[0011] 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 a roadside unit.

[0012] 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.

[0013] 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.

[0014] The positioning device according to the second embodiment includes: a plurality of antennas provided at a distance from the vehicle in the front-rear 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.

[0015] According to the second 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.

[0016] The positioning device according to the third embodiment further comprises a Doppler frequency correction unit that corrects the Doppler frequency based on the vehicle speed, in addition to the positioning device according to the first embodiment.

[0017] According to the third embodiment, the influence of vehicle speed during measurement of Doppler frequency can be suppressed.

[0018] The positioning device according to the fourth embodiment is a positioning device according to the third embodiment, wherein the Doppler frequency correction unit invalidates the measured Doppler frequency when the vehicle speed is below a predetermined threshold, and the positioning calculation unit calculates the position of the roadside unit using at least three valid measurement values ​​before and after the vehicle passes the roadside unit.

[0019] According to the fourth embodiment, even when the vehicle repeatedly starts and stops due to traffic congestion, etc., it becomes possible to identify the location of the roadside unit.

[0020] In the fifth embodiment of the positioning device, the relative position calculation unit calculates the distance traveled by the vehicle by integrating the wheel speed over time.

[0021] According to the fifth embodiment, it becomes possible to calculate the relative position of the vehicle.

[0022] In the positioning device according to the sixth embodiment, the relative position calculation unit calculates the relative position of the vehicle by dead reckoning, which includes at least one of the vehicle's turning and lane changes.

[0023] According to the sixth aspect, it is possible to determine the position of the roadside unit even when the vehicle is not traveling in a straight line.

[0024] The positioning method according to the seventh embodiment involves a computer measuring the Doppler frequency from the reception frequency when an antenna on the vehicle receives a transmission signal from a roadside unit installed on the roadside, calculating the relative position of the vehicle from the vehicle speed, determining whether the vehicle has passed the roadside unit based on the measured Doppler frequency, and calculating the position of the roadside unit based on the change in the Doppler frequency before and after the vehicle has passed the roadside unit.

[0025] According to the seventh 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.

[0026] The positioning method according to the eighth embodiment involves a computer measuring the difference in Doppler frequencies between each of several antennas, based on 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 the vehicle in the front-rear direction, calculating the relative position of the vehicle from the vehicle speed, determining whether the vehicle has passed the roadside unit based on the measured difference, and calculating the position of the roadside unit based on the change in the difference before and after the vehicle has passed the roadside unit.

[0027] According to the eighth aspect, 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.

[0028] 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.

[0029] According to the ninth 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.

[0030] 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.

[0031] 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.

[0032] According to this disclosure, a positioning device, a positioning method, and a positioning program can be provided 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.

[0033] This figure shows the schematic configuration of a vehicle equipped with a positioning device according to the first embodiment. This is a block diagram showing the schematic configuration of a positioning device according to the first embodiment. This is a functional block diagram showing the functional configuration of a positioning device according to the first embodiment. This figure shows a scene in which a moving vehicle passes in front of a roadside unit. This figure shows an example of the change in Doppler shift when a vehicle passes in front of a roadside unit. This is a flowchart showing an example of the processing flow performed by the positioning device according to the first embodiment. This is a functional block diagram showing the functional configuration of a positioning device according to the second embodiment. This figure shows an example of a scene in which a vehicle travels in front of and passes a roadside unit. This figure shows an example of the change in Doppler shift (Doppler frequency) with respect to the position of the vehicle. This figure shows an example of the change in the difference (Doppler difference) between these two Doppler shifts with respect to the position of the vehicle. This figure shows the positional relationship when a vehicle passes in front of a roadside unit. This figure shows an example of calculating the change in Doppler difference when the vehicle speed and the distance to the roadside unit are changed. This is a flowchart showing an example of the processing flow performed by the positioning device according to the second embodiment. This figure shows an example of the change in Doppler difference (extraction of valid observed values) with respect to the position of the vehicle. This figure shows an example in which there is a difference in height between the antenna of the roadside unit and the antenna of the vehicle. This figure shows an example in which the antenna is directly above the road.

[0034] Hereinafter, an example of an embodiment 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.

[0035] (First Embodiment) FIG. 1 is a diagram showing a schematic configuration of a vehicle equipped with a positioning device according to a first embodiment. Further, FIG. 2 is a block diagram showing a schematic configuration of the positioning device according to the first embodiment.

[0036] The positioning device 10 according to the present embodiment is mounted on a vehicle 12, and is connected to an antenna provided on the vehicle 12.

[0037] The antenna 14 is provided to communicate with a roadside device 18 installed beside a road. It is assumed that the installation position information of the roadside device 18 is known.

[0038] As shown in FIG. 2, the positioning device 10 according to the present embodiment is configured as a general microcomputer including a CPU (Central Processing Unit) 10A, a ROM (Read Only Memory) 10B, a RAM (Random Access Memory) 10C, a storage 10D, an interface (I / F) 10E, a bus 10F, and other components.

[0039] The CPU 10A is a central processing unit that executes various programs and controls each unit. Specifically, the CPU 10A reads a program from the ROM 10B or the storage 10D, and executes the program using the RAM 10C as a work area. The CPU 10A performs various types of control and various arithmetic processing in accordance with programs recorded in the ROM 10B or the storage 10D.

[0040] The ROM 10B stores various programs and various data. The RAM 10C temporarily stores programs or data as a work area. The storage 10D is configured of an HDD (Hard Disk Drive), an SSD (Solid State Drive), or the like, and stores various programs and various data. In the present embodiment, a positioning program for performing positioning calculation is stored in the ROM 10B or the storage 10D.

[0041] The antenna 14 and a wheel speed sensor 16 are connected to the I / F 10E, and the signal from the 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.

[0042] Next, the functional configuration of the positioning device 10 according to the first embodiment will be described. FIG. 3 is a functional block diagram showing the functional configuration of the positioning device 10 according to the present embodiment.

[0043] In the positioning device 10 according to the present embodiment, a CPU 10A expands a positioning program stored in a ROM 10B or a storage 10D into a RAM 10C and executes the program, thereby realizing the functions of a Doppler measurement unit 20, a relative position calculation unit 22, a Doppler frequency correction unit 24, a roadside unit passage determination unit 26, and a positioning calculation unit 28.

[0044] The Doppler measurement unit 20 measures the Doppler frequency from the reception frequency when an antenna 14 receives a transmission signal from the roadside unit 18.

[0045] The relative position calculation unit 22 calculates the relative position of a vehicle from the vehicle speed of the vehicle. For example, the relative position calculation unit 22 obtains a change in relative position (movement distance) of the vehicle 12 accompanying traveling of the vehicle 12 by integrating the wheel speed detected by a wheel speed sensor 16.

[0046] 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 a value converted to a predetermined reference vehicle speed.

[0047] 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 12 has passed in front of the roadside unit 18 from a change in the Doppler frequency.

[0048] The positioning calculation unit 28 calculates the position of the roadside unit 18 based on a 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 relative to the position of the vehicle 12 and the Doppler frequency. During calculation, the position of the roadside unit 18 relative to the travel trajectory of the vehicle 12 is specified by using a change in Doppler frequency before and after the vehicle 12 passes the vicinity of the roadside unit 18.

[0049] 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.

[0050] 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.

[0051] 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).

[0052] 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 vcosθ.

[0053] When the vehicle 12 receives the signal transmitted from the roadside unit 18, a Doppler shift occurs as the vehicle 12 moves. Therefore, the frequency of the signal transmitted by the roadside unit 18 is set to f Ｓ Therefore, the frequency f of the received signal in vehicle 12 Ｒ The equation is as follows:

[0054]

[0055] 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.

[0056]

[0057] Let x be the position of vehicle 12, and let the vehicle speed and direction be functions of position.

[0058]

[0059] As a result, the Doppler shift f is relative to the position x of the vehicle 12. Ｄ Figure 5 illustrates this.

[0060] In this embodiment, when the vehicle 12 enters the communication area of ​​the roadside unit 18, the signal transmitted from the roadside unit 18 is received by the antenna 14 installed on the vehicle 12. The Doppler frequency is determined by the vehicle speed and the direction from the antenna 14 to the roadside unit 18. The Doppler measurement unit 20 measures the Doppler frequency of the received signal and simultaneously records the time of measurement.

[0061] 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.

[0062] As vehicle 12 moves, its position changes, and the direction from antenna 14 to roadside unit 18 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.

[0063] 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.

[0064] Specifically, since the Doppler frequency is proportional to the vehicle speed v(x), the reference vehicle speed is V ０ In this case, the coefficient v ０ By multiplying by / v(x), the Doppler frequency can be corrected to that of a vehicle traveling at a reference speed, regardless of the position of the vehicle 12.

[0065]

[0066] 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.

[0067] 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.

[0068]

[0069] From the above, we can determine the distance Y from the roadside unit 18 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 12's travel trajectory.

[0070] This allows us to determine the lateral distance of the vehicle 12 to the roadside unit 18 when it passes over it, making it possible to identify the lane the vehicle is traveling in, for example, when driving on a multi-lane road. Furthermore, the position of the driving trajectory can be corrected based on the installation position information of the roadside unit 18.

[0071] 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.

[0072] 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.

[0073] 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 the vehicle speed from the wheel speed sensor 16, and calculates the distance traveled by the vehicle 12 by integrating the wheel speed.

[0074] 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.

[0075] 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.

[0076] In step 108, the CPU 10A determines whether the measurement was taken before or after the passage of the roadside device 18. If the determination is negative, the process returns to step 100 and the above process is repeated. If the determination is positive, 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 device 18 can be obtained.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] (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.

[0081] In this embodiment, compared to the first embodiment, the vehicle 12 is equipped with two antennas (antenna A14A, antenna 14B) 14. Also, instead of the Doppler measurement unit 20, it is equipped with the function of a Doppler difference measurement unit 21.

[0082] The Doppler difference measurement unit 21 measures the difference in Doppler shift between each antenna 14 from the reception frequency when each antenna 14 receives the transmission signal from the roadside unit 18.

[0083] Here, we consider the case where the antennas 14 of vehicle 12 are installed at a distance from the vehicle 12 in the front-to-back direction. Figure 8 shows a scene in which vehicle 12 drives in front of and passes the 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 the roadside unit 18.

[0084] 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.

[0085] The difference from the first embodiment is that when the position of the vehicle 12 is x = X, the positions of the two antennas 14 are X １ , X ２is expressed by the following formula using the inter-antenna distance d, respectively.

[0086]

[0087] Since the azimuth θ1 from the antenna A14A to the roadside device 18 and the azimuth θ2 from the antenna B14B to the roadside device 18 are different, the Doppler frequency f of the received signal at each antenna 14 corresponds to the difference in azimuth Ｄ１ , f Ｄ２ has a difference. This frequency difference f ＤＤ is measured by the Doppler difference measurement unit 21, and the time of simultaneous measurement is recorded.

[0088]

[0089] The roadside device passage determination unit 26 determines whether the vehicle has passed the front of the roadside device 18 from the change in the Doppler difference. As shown in FIG. 10, the Doppler difference increases before passing the roadside device 18 and decreases after passing the roadside device 18, so the change in the Doppler difference reaches a maximum and takes a peak value when passing the front of the roadside device 18. Therefore, it can be determined whether the vehicle has passed the roadside device 18.

[0090] The positioning calculation unit 28 identifies the position of the roadside device 18 relative to the travel trajectory of the vehicle 12 by using the change in the Doppler difference between the two antennas 14 before and after passing the roadside device 18. Since the Doppler difference takes a peak value when passing the front of the roadside device 18, the front-rear position of the vehicle 12 at the point where the peak value occurs is set as the front of the roadside device 18. In addition, the peak value of the Doppler difference at that point is determined by the vehicle speed, the inter-antenna distance, and the distance to the roadside device 18 at the time of passage, and is expressed by the following formula.

[0091]

[0092] Here, θ ０ is the azimuth from each antenna 14 to the roadside device 18 when the vehicle 12 passes the front of the roadside device 18. FIG. 11 shows the positional relationship when the vehicle 12 passes the front of the roadside device 18.

[0093] 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.

[0094] 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 roadside unit 18 can be determined.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] In step 204, the CPU 10A corrects the Doppler difference and proceeds to step 206. That is, the Doppler frequency correction unit 24 corrects the measured Doppler difference and vehicle speed to a Doppler difference converted to a reference vehicle speed.

[0100] 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.

[0101] In step 208, the CPU 10A determines whether the measurement was taken before or after the passage of the roadside device 18. If the determination is negative, the process returns to step 200 and the above process is repeated. If the determination is positive, 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 device 18 can be obtained.

[0102] In step 210, a 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. The lateral position (distance) is also determined from the maximum value of the Doppler difference.

[0103] 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.

[0104] (Third Embodiment) In each of the above embodiments, since Doppler is used, it is assumed that the vehicle passes near the roadside unit 18 at a certain speed or higher. In addition, in the description 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.

[0105] 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.

[0106] 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).

[0107] 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 the 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 vehicle 12's position. Thus, the gaps can be interpolated from data where Doppler observations were valid, and the same processing can be performed.

[0108] If the number of valid Doppler frequency measurement results 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 is a diagram showing an example of the change in Doppler difference with respect to the vehicle's position (extraction of valid observation values).

[0109] 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.

[0110] 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.

[0111] Furthermore, in each of the above embodiments, when the relative position calculation unit 22 determines the change in relative position 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.

[0112] 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.

[0113] For example, Figure 15 shows the case where there is a difference in height between the roadside unit 18 and the vehicle 12's antenna. 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.

[0114] Furthermore, as shown in Figure 16, each embodiment is applicable even if the antenna of the roadside unit 18 is directly above the road. 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.

[0115] In the above embodiment, a CPU was given as an example of a processor, but the term "processor" refers to a broader term and includes general-purpose processors (e.g., CPUs) and dedicated processors (e.g., GPUs: Graphics Processing Units, ASICs: Application Specific Integrated Circuits, FPGAs: Field Programmable Gate Arrays, programmable logic devices, etc.).

[0116] 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's operations is not limited to the order described in each of the above embodiments, but may be changed as appropriate.

[0117] 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.

[0118] The program of this application can be provided as a program product. A program product includes all forms of products 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.

[0119] Furthermore, this disclosure is not limited to the foregoing, and it is of course possible to implement it in various modified forms without departing from its intent.

[0120] The present disclosure may adopt the following embodiments: (1) A positioning device comprising: an antenna provided on a vehicle and installed on the roadside to receive a transmission signal from a roadside unit; a Doppler measurement unit that measures a 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.

[0121] (2) A positioning device comprising: a plurality of antennas provided at a distance from the vehicle in the longitudinal direction and installed on the roadside to receive transmission signals from a roadside unit; a Doppler difference measurement unit that measures the difference in Doppler frequencies between each of the antennas from the reception frequencies when each of the antennas 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.

[0122] (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.

[0123] (4) The positioning device according to (3), wherein the Doppler frequency correction unit invalidates the measured Doppler frequency when the vehicle speed is below a predetermined threshold, and the positioning calculation unit calculates the position of the roadside unit using at least three valid measured values ​​before and after the vehicle passes the roadside unit.

[0124] (5) A 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.

[0125] (6) A 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 changing lanes.

[0126] (7) A positioning method comprising: a computer measuring 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; calculating the relative position of the vehicle from the vehicle speed; determining whether the vehicle has passed the roadside unit based on the measured Doppler frequency; and calculating the position of the roadside unit based on the change in the Doppler frequency before and after the vehicle has passed the roadside unit.

[0127] (8) A positioning method comprising: a computer measuring the difference in Doppler frequencies between each of several antennas, based on the reception frequencies when a signal transmitted from a roadside unit installed on the roadside is received by a plurality of antennas installed at a distance from the front and rear of the vehicle; calculating the relative position of the vehicle from the vehicle speed; determining whether the vehicle has passed the roadside unit based on the measured difference; and calculating the position of the roadside unit based on the change in the difference before and after the vehicle has passed the roadside unit.

[0128] (9) A positioning program that 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.

[0129] (10) A positioning program that 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 front and rear of the vehicle; 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.

Claims

1. A positioning device comprising: an antenna mounted on a vehicle and installed on the roadside to receive a transmission signal from a roadside unit; 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.

2. A positioning device comprising: a plurality of antennas provided at a distance from the vehicle in the longitudinal direction and installed on the roadside to receive transmission signals from a roadside unit; 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.

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 positioning device according to claim 3, wherein the Doppler frequency correction unit invalidates the measured Doppler frequency when the vehicle speed is below a predetermined threshold, and the positioning calculation unit calculates the position of the roadside unit using at least three valid measured 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. A positioning method comprising: a computer measuring the Doppler frequency from the reception frequency when an antenna on a vehicle receives a transmission signal from a roadside unit installed on the roadside; calculating the relative position of the vehicle from the vehicle speed; determining whether the vehicle has passed the roadside unit based on the measured Doppler frequency; and calculating the position of the roadside unit based on the change in the Doppler frequency before and after the vehicle has passed the roadside unit.

8. A positioning method comprising: a computer measuring the difference in Doppler frequencies between multiple antennas, based on the reception frequencies when a signal transmitted from a roadside unit installed on the roadside is received by multiple antennas installed at a distance from the vehicle in the front-rear direction; calculating the relative position of the vehicle from the vehicle speed; determining whether the vehicle has passed the roadside unit based on the measured difference; and calculating the position of the roadside unit based on the change in the difference before and after the vehicle has passed the roadside unit.

9. A positioning program that causes a computer to perform the following processes: measure the Doppler frequency from the reception frequency when an antenna on a 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.

10. A positioning program that 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.

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