JP4930075B2 - Road-to-vehicle communication system and optical beacon used therefor - Google Patents

Description

  The present invention relates to a road-to-vehicle communication system for obtaining a distance to a predetermined position ahead in the traveling direction by communication between an optical beacon and an in-vehicle device, and an optical beacon used therefor.

As a traffic information service using a road-to-vehicle communication system, so-called VICS (Vehicle Information and Communication System) using optical beacons, radio wave beacons or FM multiplex broadcasting has already been developed. Among these, the optical beacon employs optical communication using near infrared rays as a communication medium, and enables two-way communication with the in-vehicle device.
Specifically, uplink information including a vehicle ID for identifying a vehicle is transmitted from the in-vehicle device to the infrastructure-side optical beacon, and conversely includes traffic jam information, section travel time information, lane notification information, and the like. Downlink information is transmitted from the optical beacon to the vehicle-mounted device (see, for example, Patent Document 1).

  The optical beacon is disposed on a road and includes a light emitter / receiver that performs bidirectional communication with an in-vehicle device. From this light emitter / receiver, lane notification information ( The first downlink information including the vehicle ID and the lane number is constantly transmitted to the downlink region of the road at a predetermined transmission cycle. When the vehicle passes through the downlink area, the in-vehicle device mounted on the vehicle receives the first downlink information, and the in-vehicle device starts transmitting uplink information storing its own vehicle ID.

  When the optical beacon receives the uplink information, the optical beacon starts to transmit the second downlink information including the vehicle ID to the in-vehicle device, and can transmit the second downlink information within a predetermined time. Repeat as long as possible. When confirming that the vehicle ID is stored in the second downlink information, the in-vehicle device recognizes that the second downlink information is transmitted to itself, and Necessary information can be obtained from the downlink information. The in-vehicle device repeatedly transmits the uplink information until it is confirmed that its own vehicle ID is stored in the second downlink information.

  In the light beacon projector / receiver described above, for example, as shown in FIG. According to the “near-infrared interface standard” of the optical beacon (optical vehicle sensor) 4, the uplink area UA that receives the uplink information from the in-vehicle device 2 is the vehicle traveling in the communication area A as shown in the figure. The downlink area DA is set to coincide with the entire communication area A. Accordingly, the upstream end c of the uplink area UA coincides with the upstream end of the downlink area DA, and the uplink area UA is set to overlap with the upstream portion of the downlink area DA.

  Therefore, the vehicle traveling direction length of the downlink area DA matches the same direction length of the entire communication area A. In addition, according to the above standard, in the case of the optical beacon 4 for general roads, the downstream end a of the downlink area DA is located 1.0 to 1.3 m upstream immediately below the light emitter / receiver 8 and is The distance from the downstream end a of the link area DA to the downstream end b of the uplink area UA is defined as 2.1 m, and from the downstream end b of the uplink area UA to the upstream end c of the area UA (downlink area DA) The distance is defined as 1.6 m. Accordingly, in this case, the total length of the communication area A in the vehicle traveling direction is 3.7 m.

JP 2005-268925 A

  In the road-to-vehicle communication system using the conventional optical beacon, for example, distance information from the communication area A to a predetermined position (for example, a stop line) on the downstream side is included in the second downlink information. The in-vehicle device 2 that has received the distance information uses the distance information to brake the vehicle so that it is forcibly stopped before the stop line, or to notify the driver to stop or decelerate the vehicle. On the other hand, there are cases where safe driving support is performed (for example, Japanese Patent Application Nos. 2006-121692 and 2006-121700 proposed by the present applicant).

  Normally, the optical beacon 4 can receive the uplink information transmitted from the vehicle-mounted device 2 located in the uplink area UA with a probability of approximately 90% or more. For this reason, if the upstream end of the downlink area DA and the upstream end of the uplink area UA coincide with each other according to the standard, the vehicle-mounted device 2 starts transmission of the uplink information and receives the second downlink information. The position is in the vicinity of the upstream end of the communication area A where the in-vehicle device 2 enters the communication area A and receives the first downlink information. Here, if the distance information stored in the downlink information is, for example, the distance from the upstream end of the uplink area UA to the predetermined position, the in-vehicle device actually performs the operation from the point where the downlink information is received to the predetermined position. It is possible to obtain distance information that substantially matches the distance of.

On the other hand, the main purpose of a road-to-vehicle communication system using an optical beacon has been to reliably transmit traffic information such as VICS to an in-vehicle device. In most cases, the downlink area DA is set wider than the area length defined in the standard so that data can be transmitted and received reliably in the communication area.
Furthermore, since the optical signal emitted from the light emitter / receiver 8 of the optical beacon 4 spreads as it goes farther, even if the position of the upstream end of the downlink area DA is set according to the standard, it is even more than the set position. The optical signal from the projector / receiver may reach the upstream side.

For the above reason, as shown in FIG. 6, there is a case where the upstream end c ′ of the actual downlink area DA is located upstream of the upstream end c of the uplink area UA. In such a case, in the communication area A, the area constituted only by the downlink area is not only downstream of the uplink area UA downstream end b, but also upstream of the upstream end c of the same area (in FIG. It also exists in a region indicated by a one-dot chain line).
When the vehicle-mounted device 2 of the vehicle C traveling on the road enters the communication area A, first, the vehicle C enters the area composed only of the downlink area DA existing on the upstream side of the uplink area UA (in FIG. 6, Vehicle C) indicated by a solid line. Then, the in-vehicle device 2 receives the first downlink information and transmits the uplink information. However, at this stage, as shown in FIG. 6, since the vehicle-mounted device 2 has not yet reached the uplink area UA, the uplink information transmitted by the vehicle-mounted device 2 is received by the light emitter / receiver 8 of the optical beacon 4. In addition, the second downlink information including the vehicle ID is not transmitted from the optical beacon 4.
Since the in-vehicle device 2 transmits the uplink information at a predetermined transmission cycle, the vehicle position indicated by the broken line in FIG. 6 is a position advanced from the position where the uplink information was first transmitted during the time of the transmission cycle. In C), uplink information is transmitted again. If the in-vehicle device 2 has entered the uplink area UA at the time of the second transmission, the uplink information transmitted again is received by the light projector / receiver 8. Thereafter, the in-vehicle device 2 receives the second downlink information including the vehicle ID and various information transmitted from the optical beacon 4 that has received the uplink information.

  In the above case, the position of the vehicle C indicated by the broken line at the time of the second transmission is less than the position of the vehicle C indicated by the solid line at the time of the first transmission during the time corresponding to the transmission cycle of the uplink information It will approach the predetermined position on the downstream side by the distance X where C moves forward. Here, when the distance information included in the downlink information is set as the distance from the upstream end of the uplink area UA to the predetermined position assuming that the communication area A is set according to the standard, An error corresponding to the distance X is generated at the maximum between the distance from the current position 2 where the distance information 2 is received to the predetermined position and the distance based on the distance information.

  As described above, the uplink information received first by the optical beacon is transmitted from the vehicle-mounted device 2 located at the upstream end of the uplink area UA, or even more than the upstream end of the uplink area UA. When the position of the in-vehicle device 2 when the uplink information received first by the optical beacon 4 is transmitted, such as the information transmitted from the downstream side, is transmitted to the in-vehicle device 2 thereafter. Error may occur in the distance information included in the second downlink information, and in such a case, the in-vehicle device cannot accurately recognize the distance to the predetermined position and is appropriate for the driver. There is a situation where safe driving support cannot be performed.

  As described above, when the road-vehicle communication system is used not only for transmission of traffic information but also for safe driving support, the optical beacon always causes the in-vehicle device to receive the second downlink information at a stable position. In other words, in other words, it is preferable that the position of the vehicle-mounted device at the time of transmission of the uplink information first received by the optical beacon is always stable.

  The present invention has been made in view of such circumstances, and it is possible to stabilize the position of the vehicle-mounted device at the time of transmission of the uplink information first received by the optical beacon at a certain position, and the vehicle traveling direction It is an object of the present invention to provide a road-to-vehicle communication system capable of recognizing a distance to a predetermined position ahead with high accuracy, and an optical beacon used therefor.

The road-to-vehicle communication system of the present invention includes an in-vehicle device of a vehicle traveling on a road, and an optical beacon having a projector / receiver that sets a communication area within a predetermined range on the road, and the communication area includes the optical beacon. A region in which downlink information is transmitted to the in-vehicle device, and a region in which the projector / receiver receives uplink information transmitted by the in-vehicle device receiving the downlink information. The upstream and downstream ends of the uplink region are set upstream of the upstream end of the downlink region, and the upstream and downstream ends of the downlink region. On the upstream side, there is an area where information that can be received by the in-vehicle device is not transmitted by being configured only by the uplink area .

According to the road-to-vehicle communication system configured as described above, the upstream end of the uplink region is set upstream of the upstream end of the downlink region, so when the vehicle-mounted device enters the downlink region. This means that the user has definitely entered the uplink area. That is, when the in-vehicle device transmits uplink information for the first time after receiving the downlink information, the in-vehicle device is located in the uplink region. For this reason, the optical beacon can reliably receive the uplink information transmitted first at the position immediately after the vehicle-mounted device enters the downlink region.
In other words, the optical beacon reliably receives the first uplink information transmitted at the position immediately after the in-vehicle device enters the downlink region, so the in-vehicle when the uplink information received first by the optical beacon is transmitted. The position of the aircraft can be stabilized at the position immediately after entering the downlink area.

  In the road-to-vehicle communication system, the optical beacon stores distance information related to a distance from the communication area to a predetermined position on the downstream side in the downlink information in response to reception of the uplink information. The vehicle-mounted device may include a distance recognition unit that recognizes a distance to the predetermined position based on the distance information.

  In this case, since the in-vehicle device can stably receive the downlink information transmitted from the optical beacon according to the received uplink information at the position immediately after entering the downlink region, An error can be prevented from occurring in the included distance information, and the distance to a predetermined position ahead in the vehicle traveling direction can be recognized with high accuracy.

Moreover, the optical beacon of the present invention has a projector / receiver that sets a communication area for communication with an in-vehicle device of a vehicle traveling on a road to a predetermined range of the road, and the communication area includes the projector / receiver. A region in which downlink information is transmitted to the in-vehicle device, and a region in which the projector / receiver receives uplink information transmitted by the in-vehicle device receiving the downlink information. The upstream and downstream ends of the uplink region, and the upstream and downstream ends of the downlink region and the upstream end of the downlink region. An area where no information that can be received by the in-vehicle device is transmitted exists by being configured only by the uplink area .

  According to the optical beacon configured as described above, as described above, uplink information to be transmitted first is reliably received at a position immediately after the vehicle-mounted device enters the downlink region. Therefore, it is possible to stabilize the position of the vehicle-mounted device at the time of transmitting the uplink information received first by the optical beacon at the position immediately after entering the downlink region.

  Further, in the optical beacon, in response to reception of the uplink information, distance information related to a distance from the communication area to a predetermined position on the downstream side is stored in the downlink information, and the distance information is based on the distance information. When the in-vehicle device that recognizes the distance to the predetermined position is provided with a control unit that transmits the downlink information, as described above, an error occurs in the distance information stored in the downlink information. It is possible to prevent the vehicle-mounted device from recognizing the distance to a predetermined position ahead of the vehicle traveling direction with high accuracy.

  As described above, according to the present invention, it is possible to stabilize the position of the vehicle-mounted device at the time of transmission of the uplink information received first by the optical beacon at a certain position and to a predetermined position ahead of the vehicle traveling direction. Can be recognized with high accuracy.

Next, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
[Overall system configuration]
FIG. 1 is a block diagram showing the overall configuration of a road-vehicle communication system including an optical beacon.
As shown in FIG. 1, the road-to-vehicle communication system includes an infrastructure-side traffic control system 1 and an in-vehicle device 2 mounted on each vehicle C traveling on a road R.

  The traffic control system 1 includes a central device 3 provided in a control room and optical beacons (optical vehicle detectors) 4 installed in many places on the road R. The optical beacon 4 performs bidirectional communication with the in-vehicle device 2 by optical communication using near infrared rays as a communication medium. The central device 3 is provided in the traffic control room.

[Configuration of optical beacon]
The optical beacon 4 includes a communication unit 6 that is a communication interface connected to the central apparatus 3 via a communication line 5 such as a telephone line, a beacon controller 7 to which the communication unit 6 is connected, and the controller 7 And a plurality of light emitters / receivers 8 connected to the sensor interface.
Each projector / receiver 8 is configured by housing a light emitting diode (LED) 10 and a photosensor 11 inside a housing 9 (see FIG. 3). Among them, the LED 10 emits downlink information made of near infrared rays to a communication area A described later, and the photo sensor 11 receives uplink information made of near infrared rays from the in-vehicle device 2. A downlink area DA and an uplink area UA, which will be described later, are set to a predetermined range on the road by adjusting the LED 10 and the photo sensor 11.

FIG. 2 is a plan view of the optical beacon 4.
As shown in FIG. 2, the optical beacon 4 of this embodiment is installed on a road R having a plurality of lanes R1 to R4 (four in the illustrated example) in the same direction, and corresponds to each lane R1 to R4. The plurality of projectors / receivers 8 provided and a single beacon controller 7 serving as a control unit that collectively controls the projectors / receivers 8.
The beacon controller 7 includes a microcomputer having a CPU, a memory (RAM), and a storage device (ROM). It functions as a control unit that performs road-to-vehicle communication. The contents of road-to-vehicle communication by the beacon controller 7 will be described later.

The beacon controller 7 is installed on a support column 12 erected on the side of the road, and each projector / receiver 8 is attached to an installation bar 13 installed horizontally on the road R side from the support column 13, and each lane on the road R. Arranged immediately above R1 to R4.
The LED 10 of each projector / receiver 8 emits near-infrared light toward the upstream side of the lanes R <b> 1 to R <b> 4, and thereby a communication area for performing road-to-vehicle communication with the in-vehicle device 2. A is set on the upstream side (right side in FIG. 2) of the light projector / receiver 8.

[Communication area]
FIG. 3 is a side view showing the communication area A of the optical beacon 4, and the vehicle C travels in the direction of the arrow in the figure. In FIG. 3, the communication area A set by the projector / receiver 8 is a downlink area (indicated by a solid line in FIG. 3) in which an in-vehicle head 20 (see FIG. 4) of the in-vehicle apparatus 2 described later can receive downlink information. (Hatched area) DA and an uplink area (area where broken line hatching is provided in FIG. 3) UA in which the projector / receiver 8 of the optical beacon 4 can receive uplink information.

  In the “near infrared interface standard” of the optical beacon (optical vehicle detector) 4, the uplink region overlaps the upstream portion of the downlink region in the vehicle traveling direction, and the upstream end of the downlink region and the uplink region It is defined that the upstream ends coincide with each other. For this reason, the vehicle traveling direction length of the entire communication area A coincides with the length of the downlink area in the same direction.

With respect to the above standard, the point u2 indicating the upstream end of the uplink area UA of the present embodiment is upstream (right side in FIG. 3) from the point d2 indicating the upstream end of the downlink area DA. The upstream end of the entire communication area A is set to a point u2, and the downstream end is set to a point d1 indicating the downstream end of the downlink area DA.
For this reason, the downstream part of the uplink area UA and the upstream part of the downlink area DA overlap between the point u1 indicating the downstream end of the uplink area UA and the point d2. On the upstream side of the upstream end (point d2) of the overlapping portion (between point u1 and point d2) where both the regions overlap, there is a region composed only of the uplink region UA.
Therefore, when the vehicle-mounted device 2 of the vehicle C traveling on the road R enters the downlink area DA, the vehicle-mounted device 2 surely enters the uplink area UA.
Note that the point u2 which is the upstream end of the uplink area UA is surely a point even if the upstream end of the downlink area DA is set further to the upstream end side than the point to be set due to an error or the like. It is set at a position on the upstream side of d2.

[Configuration of in-vehicle device and vehicle]
FIG. 4 is a schematic configuration diagram of a vehicle C in which the optical beacon 4 and the in-vehicle device 2 that communicates with the optical beacon 4 are mounted.
As shown in FIG. 4, the vehicle C includes a vehicle body 15 having a driver's boarding seat (not shown), the above-described in-vehicle device 2 mounted on the vehicle body 15, and an electronic device that integrally controls each part of the vehicle C. A control device (ECU) 16, an engine 17 that drives the vehicle body 15, a brake device 18 that brakes the vehicle body 15, and a speed detector 26 that constantly detects the current speed of the vehicle C are provided. The ECU 16 performs various controls on the vehicle C such as drive control of the engine 17 based on the accelerator operation of the driver and braking control based on the brake operation.

The in-vehicle device 2 includes an in-vehicle computer 19, an in-vehicle head 20 connected to a sensor interface of the in-vehicle computer 19, and a display 21 and a speaker device 22 as a human interface for a driver of a passenger seat.
The vehicle-mounted head 20 includes a light emitting diode (LED) and a photosensor (not shown), like the light beacon projector / receiver 8. Among these, the LED emits uplink information composed of near infrared rays, and the photosensor receives downlink information composed of near infrared rays emitted to the communication area A.

The in-vehicle computer 19 is configured by a microcomputer having a CPU, a memory (RAM), and a storage device (ROM), and performs control processing of road-to-vehicle communication with the optical beacon 4 by the in-vehicle head 20.
The in-vehicle computer 19 stores a program for executing each predetermined function in a storage device, and includes a distance recognition unit 23 and a support control unit 24 as functional units to be executed by the program.

The distance recognition unit 23 of the in-vehicle computer 19 is based on the distance information stored in the uplink information transmitted from the optical beacon 4 in road-to-vehicle communication described later (for example, a vehicle on the downstream side of the optical beacon 4 (e.g., vehicle The distance to the stop line (in front of the intersection in front of the traveling direction) is calculated and recognized.
The support control unit 24 of the in-vehicle computer 19 controls the safe driving support for the driver based on the support information included in the downlink information received by the in-vehicle device 2. This safe driving support will be described later, and includes, for example, deceleration control of the vehicle C based on support information such as traffic signal information and distance information, and notification control to the driver. This traffic signal information is timing information or the like at which the color of the traffic light on the downstream side of the optical beacon 4 changes, and the distance information is information on the distance from the downlink area DA to a predetermined position on the downstream side of the optical beacon 4. .

  By including these traffic signal information and distance information in the downlink information, the support control unit 24 brakes the ECU 16 so that the vehicle C does not enter the intersection after the traffic signal ahead changes to red. The device 18 is operated to decelerate the vehicle C, and the display 21 and the speaker device 22 notify the driver that the traffic light turns red.

  The display 21 includes an in-vehicle display that constitutes an image display unit of a navigation device or a television device, a head-up display that displays a figure on the windshield surface of the vehicle body 15, and the like. The speaker device 22 includes a speaker provided on the front panel or door of the vehicle body 15 of the passenger seat. The display 21 and the speaker device 22 function as an output unit that notifies the driver of information related to safe driving support as described above.

[Road-to-vehicle communication]
FIG. 5 shows a two-way road-to-vehicle communication procedure performed between the light projector / receiver 8 of the optical beacon 4 and the vehicle-mounted head 20 of the vehicle-mounted device 2 in the communication area A. Hereinafter, the contents of the road-to-vehicle communication will be described with reference to FIG.
First, the beacon controller 7 of the optical beacon 4 receives first downlink information 28 including lane notification information from each projector / receiver 8 corresponding to each lane R1 to R4 as the first information before downlink switching. Is continuously transmitted to the downlink area DA of each lane R1 to R4 at a predetermined transmission cycle (F1 in FIG. 5). At this stage, the vehicle ID is not yet stored in the lane notification information.

  When the vehicle C equipped with the vehicle-mounted device 2 enters the upstream portion of the downlink area DA, the vehicle-mounted head 20 of the vehicle-mounted device 2 receives the first downlink information 28 including the lane notification information (no vehicle ID). At this time, the in-vehicle computer 19 of the in-vehicle device 2 recognizes that the vehicle C exists in the communication area A. Thereafter, the in-vehicle computer 19 starts transmission of the uplink information 29 (F2 in FIG. 5), and transmits this uplink information 29 to the projector / receiver 8 of the optical beacon 4 at a predetermined transmission cycle (in FIG. 5). F3). The in-vehicle computer 19 stores a specific vehicle ID for the vehicle C in the uplink information 29 and transmits the uplink information 29. The in-vehicle computer 19 continues to transmit the uplink information 29 until it recognizes that the beacon controller 7 of the optical beacon 4 has switched the downlink.

On the other hand, when the projector / receiver 8 of the optical beacon 4 receives the uplink information 29 in the uplink area UA set by the optical beacon 4 (F4 in FIG. 5), the beacon controller 7 switches the second after the downlink switching. As information, transmission of the second downlink information 30 including lane notification information for the vehicle-mounted device 2 having the vehicle ID information is started (F5 in FIG. 5), and transmission of the downlink information 30 is performed within a predetermined time. Repeat as much as possible (F6 in FIG. 5).
The lane notification information includes a field for storing a vehicle ID for each lane R1 to R4, and a lane number can be assigned to each vehicle ID. For this reason, the vehicle-mounted computer 19 of each vehicle C traveling in different lanes R1 to R4 determines which lane R1 to R4 the host vehicle is in by determining which of the storage fields includes the vehicle ID of the host vehicle. Can recognize if you are driving.

The beacon controller 7 stores, in the second downlink information 30, traffic information, event regulation information, and the support information for safe driving support for the driver, in addition to the lane notification information including the vehicle ID. To send.
This support information includes the traffic signal information, which is timing information for changing the color of the traffic light downstream of the optical beacon 4, and a predetermined position downstream of the optical beacon 4 from the downlink area DA (for example, before the front intersection). Distance information that is length information to a certain stop line) is included.

  As shown in FIG. 5, the second downlink information 30 includes a single or a plurality of minimum frames 31. According to the “near infrared interface standard”, the data amount of the minimum frame 31 is defined as a total of 128 bytes, and 5 bytes are allocated to the header portion 32 and 123 bytes are allocated to the actual data portion 33.

According to the standard, the second downlink information 30 can be composed of 1 to 80 minimum frames 31, and the transmittable time is set to 250 ms. The downlink information 30 is composed of an arbitrary number of minimum frames 31 corresponding to the amount of information to be transmitted, and is repeatedly transmitted within the range of the transmittable time.
The transmission period of the minimum frame 31 is about 1 ms. Therefore, for example, when one downlink information 30 is composed of the three minimum frames 31, the transmission period of the downlink information 30 is about 3 ms. Therefore, the downlink information 30 has a predetermined transmittable time (250 m). ) Will be repeatedly transmitted about 80 times during this period.

The in-vehicle computer 19 of the in-vehicle device 2 recognizes the downlink switching in the optical beacon 4 at the time of receiving the second downlink information 30 (F7 in FIG. 5), and transmits the uplink information 29 at this time. Stop.
Thus, the in-vehicle computer 19 of the in-vehicle device 2 receives the downlink information 30 including the support information, and starts recognition of the distance to the predetermined position and control of the safe driving support based on the support information ( F8 in FIG.
Hereinafter, this safe driving support will be described in detail.

[Safe driving support]
The safe driving support is such that the vehicle C is automatically decelerated to a predetermined speed or the vehicle C is automatically stopped at a predetermined position downstream of the light emitting / receiving device 8 of the optical beacon 4 in the vehicle traveling direction. It is an operation that can be performed.
With reference to FIG. 3, in the following description, the system of the present embodiment automatically decelerates the vehicle according to the color of the traffic light 35 located in front of the traveling vehicle C on the road R. A case where the vehicle C is automatically stopped according to a stop line P as a predetermined position in front of the vehicle traveling direction provided in front of the vehicle 35 will be described.

In FIG. 3, when the vehicle C moves forward toward the traffic light 35, the vehicle C enters the communication area A. Here, in the communication area A, as described above, the point u2 that is the upstream end of the uplink area UA is set upstream of the point d2 that is the upstream end of the downlink area DA. An upstream area (point d2) upstream of the overlapping portion where UA and DA overlap, and an area composed only of the uplink area UA exists between the point d2 and the point u2. . For this reason, the vehicle C first enters an area composed only of the uplink area UA (position c1 in the figure). At this time, the vehicle-mounted device 2 of the vehicle C is in a state of entering the uplink area UA, but has not yet entered the downlink area DA, and therefore is transmitted from the light projector / receiver 8 of the optical beacon 4. The first downlink information 28 is never received. For this reason, in this position c1, the vehicle equipment 2 does not transmit the uplink information 29.
Thereafter, when the vehicle C further moves forward and the in-vehicle device 2 enters the overlapping area (position c2 in the figure), the in-vehicle device 2 enters the downlink area DA. The first downlink information 28 to be transmitted is received, and the transmission of the uplink information 29 is started in response thereto.

Here, since the projector / receiver 8 of the optical beacon 4 always transmits the first downlink information 28 in the downlink area DA, when the vehicle-mounted device 2 enters the downlink area DA, The first downlink information 28 is received at the position c2, which is the position of. Thereafter, transmission of the uplink information 29 is started at a predetermined transmission cycle.
Usually, it is understood that the projector / receiver 8 of the optical beacon 4 can receive the uplink information 29 transmitted from the vehicle-mounted device 2 located in the uplink area UA with a probability of approximately 90% or more. For this reason, the optical beacon 4 is the uplink information transmitted first among the uplink information 29 transmitted at a predetermined cycle at the position c2 immediately after the vehicle-mounted device 2 of the vehicle C enters the downlink area DA. 29 can be received almost certainly.

When receiving the uplink information 29, the optical beacon 4 performs downlink switching as described above, and starts transmitting the second downlink information 30.
The beacon controller 7 of the optical beacon 4 stores and transmits support information and the like in addition to the lane notification information in the second downlink information 30 as described above.
The support information includes traffic light information including information on the light color of the front traffic light 35 and information on the display duration of the light color, and a distance that is length information from the downlink area DA to the front stop line P. Contains at least information. The distance information can be, for example, a distance D1 from the point d2 that is the upstream end of the downlink area DA to the stop line P. This distance information is measured when the optical beacon 4 is installed, and is stored in the beacon controller 7.

  Since the optical beacon 4 receives the uplink information 29 transmitted first from the in-vehicle device 2 and starts transmitting the second downlink information 30 in response thereto, the in-vehicle device 2 After the transmission is started, the second downlink information 30 from the optical beacon 4 is immediately received. That is, the in-vehicle device 2 starts transmission of the uplink information 29 and receives the second downlink information 30 at a position c2 that is a position immediately after entering the downlink area DA. When the in-vehicle device 2 receives the second downlink information 30 at the position c <b> 2, the in-vehicle computer 19 of the in-vehicle device 2 acquires each information stored in the second downlink information 30.

The distance recognition unit 23 of the in-vehicle computer 19 of the in-vehicle device 2 causes the vehicle C to move from the current position c2 to the stop line based on the distance information D1 among the support information stored in the second downlink information 30. The distance to the position when stopped according to P is calculated and recognized.
The distance calculated and recognized by the distance recognition unit 23 can be the distance D2 from the current position c2 to the position c3. That is, in FIG. 3, since the vehicle-mounted head 20 of the vehicle-mounted device 2 is normally installed on the dashboard of the vehicle C, the vehicle-mounted head 20 is installed at a predetermined installation height H with respect to the road surface of the road R. A width dimension D3 is provided between the head 20 and the front end portion of the vehicle C. For this reason, a dimensional difference D4 occurs between the distance D1 as the distance information and the distance D2 in the vehicle C.
The in-vehicle computer 19 stores in advance the installation height H and the width dimension D3, which are values specific to the vehicle C, and the distance recognition unit 23 refers to each stored value in addition to the distance D1. The distance D2 in the vehicle C is acquired.

  As described above, the in-vehicle computer 19 of the in-vehicle device 2 acquires the distance D2, and performs safe driving support based on the distance D2. Specifically, the support control unit 24 of the in-vehicle computer 19 stops the vehicle C at the stop line P based on the current vehicle speed detected by the speed detector 26 in addition to the distance D2 and the traffic signal information. Judgment whether or not to make it. When it is determined that the vehicle C is to be stopped, the support control unit 24 notifies the driver that the vehicle 21 has been stopped using the display 21 or the speaker device 22 and cooperates with the ECU 16 to provide the engine 17 and the brake device. 18 is controlled to stop the vehicle C according to the stop line P.

According to the road-to-vehicle communication system of the present embodiment configured as described above, the point u2 that is the upstream end of the uplink area UA is set upstream of the point d2 that is the upstream end of the downlink area DA. Therefore, when the in-vehicle device 2 enters the downlink area DA, the in-vehicle device 2 surely enters the uplink area UA. That is, when the in-vehicle device 2 first transmits the uplink information 29 after receiving the first downlink information 28, the in-vehicle device 2 is located in the uplink area UA. For this reason, the optical beacon 4 can reliably receive the uplink information 29 transmitted first at the position c2 immediately after the in-vehicle device 2 enters the downlink area DA.
That is, since the optical beacon 4 reliably receives the uplink information 29 transmitted first at the position c2 immediately after the vehicle-mounted device 2 enters the downlink area DA, the uplink beacon 4 that the optical beacon 4 receives first. Can be stabilized at a position c2 immediately after entering the downlink area DA.

  For this reason, the in-vehicle device 2 receives the second downlink information 30 transmitted from the light emitter / receiver 8 of the optical beacon 4 according to the received uplink information 29, in the vicinity of the position c2 immediately after entering the downlink area DA. Can be received stably. Therefore, for example, as described in the above conventional example, the in-vehicle device is compared with the case where the position of the in-vehicle device 2 varies when the uplink information 29 first received by the optical beacon 4 is transmitted. An error can be prevented from occurring in the distance information included in the second downlink information 30 received by 2, and the distance to the stop line P can be recognized with high accuracy.

  Moreover, in the said embodiment, after the vehicle equipment 2 of the vehicle C located in the position c2 immediately after entering the downlink area DA receives the first downlink information 28 from the optical beacon 4, the second A small amount of communication time is required until the downlink information 30 is received. For this reason, the vehicle C moves forward slightly during the communication time, and an error due to the communication time may occur in the distance information acquired by the distance recognition unit 23. In such a case, when the distance recognition unit 23 calculates the distance D2, the distance recognition unit 23 can be configured to perform correction in advance in consideration of the communication time and the traveling speed of the vehicle C at that time.

In the above embodiment, the minimum frame 31 of the second downlink information 30 may further include progress information based on the transmission time of the first downlink information after receiving the uplink information 29. Good.
In this case, the in-vehicle device 2 cannot receive the first second downlink information 30 transmitted by the optical beacon 4 and the second downlink information 30 is received after the vehicle C has traveled a certain distance. Even if an error has occurred in the information, the distance recognizing unit 23 obtains the distance D2 in which the error is corrected by using the elapsed information and the current travel speed information in addition to the distance information. You can also.

In the above embodiment, the distance information stored in the second downlink information 30 is the distance D1 from the point d2 that is the upstream end of the downlink area DA to the stop line P. It is good also as the information shown by the form.
For example, a plurality of intermediate points are set from the point d2 to the stop line P, the distance from the point d2 to the nearest intermediate point, the distance between each intermediate point, and the intermediate point nearest to the stop line P The distances to the stop line P can be stored, respectively, and information indicating the distance D1 as a whole can be obtained.

The present invention is not limited to the above embodiment. For example, in the above-described embodiment, the case where the vehicle C is stopped according to the stop line P has been described. However, a situation in which the vehicle C must be greatly decelerated, for example, a position before a sharp curve with a poor view is set to a predetermined position, The driving distance can be accurately recognized and safe driving assistance can be performed, or a predetermined position can be set at a point where the vehicle must be temporarily stopped (for example, before a railroad crossing).
In the above embodiment, the distance information is the distance D1 from the point d2 that is the upstream end of the downlink area DA to the stop line P. However, from the installation point of the light emitter / receiver 8 of the optical beacon 4 to the stop line P. It can also be a distance. In this case, the in-vehicle computer 19 of the in-vehicle device 2 stores a predetermined distance from the upstream end of the downlink area DA to the installation point, and the distance recognition unit 23 stores the stored distance. In addition, the distance to the stop line P in the vehicle C can be calculated and recognized by adding the distance obtained from the distance information.

It is a block diagram which shows the whole structure of a road-vehicle communication system. It is a top view of an optical beacon. It is a side view which shows the aspect of installation of an optical beacon, and its communication area. It is a schematic block diagram of the vehicle carrying the optical beacon and the vehicle equipment which carries out road-to-vehicle communication with this. It is a conceptual diagram which shows the procedure and data content of the road-vehicle communication performed in a communication area. It is a side view which shows the communication area | region of the optical beacon in the conventional road-vehicle communication system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Traffic control system 2 Onboard equipment 4 Optical beacon 6 Communication part 7 Beacon controller (control part)
8 Projector / Receiver 19 In-vehicle computer 20 In-vehicle head 23 Distance recognition unit 28 First downlink information 29 Uplink information 30 Second downlink information C Vehicle R Road DA Downlink area d2 point (upstream end of downlink area)
UA uplink area u2 point (upstream end of uplink area)

Claims (4)

An in-vehicle device of a vehicle traveling on a road, and an optical beacon having a light emitter / receiver that sets a communication area in a predetermined range on the road,
The communication area includes a downlink area in which downlink information is transmitted from the optical beacon to the in-vehicle device, and uplink information to be transmitted when the in-vehicle device receives the downlink information. A road-to-vehicle communication system comprising an uplink area that is an area received by a light receiver,
The light emitter / receiver sets the upstream end of the uplink region upstream from the upstream end of the downlink region, and only the uplink region is upstream of the upstream end of the downlink region. A road-to-vehicle communication system characterized in that there is an area where information that can be received by the in-vehicle device is not transmitted . The optical beacon includes a control unit that stores distance information related to a distance from the communication region to a predetermined position downstream thereof in the downlink information in response to reception of the uplink information,
The road-to-vehicle communication system according to claim 1, wherein the vehicle-mounted device includes a distance recognition unit that recognizes a distance to the predetermined position based on the distance information. A projector / receiver that sets a communication area for communication with an in-vehicle device of a vehicle traveling on a road to a predetermined range of the road, and the communication region is a downlink from the projector / receiver to the in-vehicle device. An optical beacon comprising a downlink region that transmits information and an uplink region that is a region where the projector / receiver receives uplink information that is transmitted when the in-vehicle device receives the downlink information. There,
The light emitter / receiver sets the upstream end of the uplink region upstream from the upstream end of the downlink region, and only the uplink region is upstream of the upstream end of the downlink region. An optical beacon characterized in that there is an area where information that can be received by the in-vehicle device is not transmitted .   In response to reception of the uplink information, distance information related to the distance from the communication area to a predetermined position downstream thereof is stored in the downlink information, and the distance to the predetermined position is recognized based on the distance information. The optical beacon according to claim 3, further comprising a control unit that transmits the downlink information to the in-vehicle device.

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