JP2012084072A - Optical beacon and identification method of uplink reception position using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the positioning accuracy of an uplink reception position in a final division area UA1 in a PD division type optical beacon 4.
An optical beacon 4 according to the present invention includes a position specifying unit 50 that specifies any representative point of A _{j as} an uplink reception position in A _j based on a light reception level generated in each PD _i. comprises light receiving level of PD1 becomes equal to the value obtained by multiplying a predetermined coefficient to the sum of light receiving level of the total PD _i at the boundary position of the UA _i, a storage unit 48 for storing in advance a downstream end position of the a _n, the . Position specifying unit 50, when the uplink reception position the previously identified is in the range from the boundary position of the UA _i to A _n-1, A threshold for _n, the total PD during reception previous uplink information _i is updated to a value obtained by multiplying the total value of the light reception levels of _{i by} the predetermined coefficient, the current uplink reception position is included in An, and the light reception level of PD1 at the time of reception of the current uplink information is _equal to or greater than the updated threshold value. If it is, the stored downstream end position and the representative point of a _n.
[Selection] Figure 7

Description

  The present invention relates to a method in which an optical beacon installed on a road side performs bidirectional communication using an optical signal with an in-vehicle device mounted on a vehicle, and specifies an uplink reception position from the in-vehicle device. .

As a traffic information service using a road-to-vehicle communication system, so-called VICS (Vehicle Information and Communication System: registered trademark of Road Traffic Information Communication System Center) using optical beacons, radio beacons or FM multiplex broadcasting has already been developed. ing.
Among these, the optical beacon employs optical communication using near infrared as a communication medium, and bidirectional communication with the in-vehicle device is possible. Specifically, uplink information including travel time information between beacons held by the vehicle is transmitted from the in-vehicle device to the optical beacon on the infrastructure side, and conversely, traffic jam information, section travel time information, event regulation information, and lanes Downlink information including notification information and the like is transmitted from the optical beacon to the vehicle-mounted device (see, for example, Patent Document 1).

  With a road-to-vehicle communication system using such an optical beacon, for example, a specific position in the communication area (for example, the upstream end in the vehicle traveling direction) is regarded as the position of the vehicle (on-vehicle device), and a predetermined position downstream from the specific position. The “distance information” up to (for example, the stop line provided in front of the traffic light) is included in the second downlink information, and the distance information is received by the in-vehicle device that has received this distance information. In some cases, the vehicle is braked so as to be forcibly stopped before the stop line, or the driver is instructed to stop or decelerate to provide safe driving assistance to the driver (for example, Patent Documents 2 and 3). reference).

However, in order to receive uplink information from onboard devices more reliably, in optical beacons that are actually operated, the communication area (especially the uplink area) becomes wider than the official range defined in the standard. There are many.
Thus, if the communication area is wide, there is a high possibility that the difference between the specific position in the communication area that is the starting point of the “distance information” and the actual position at the time when the vehicle receives the distance information is increased. The accuracy of distance information is reduced.

For this reason, the accuracy of the safe driving support using this distance information is similarly reduced.For example, the vehicle is braked to stop before the stop line by the safe driving support control, but the stop line is exceeded. As a result, the vehicle may stop.
Therefore, the present applicant defines the uplink region as a plurality of divided regions divided in the vehicle traveling direction, and receives a plurality of light receptions corresponding to each of the plurality of divided regions arranged in the vehicle traveling direction. An optical beacon in which a light emitting / receiving unit is provided has already been proposed (see, for example, Patent Document 4).

If an optical beacon having a plurality of light receiving portions corresponding to each divided area (hereinafter, “PD divided type” (PD may be abbreviated as “Photodiode”)) is used, the uplink area is compared with the vehicle traveling direction. Even if it is set to be wide enough, by dividing the uplink area into a plurality of divided areas, each of the divided areas can be set narrow in the vehicle traveling direction.
For this reason, it becomes possible to accurately set a specific representative point as a starting point of the “distance information” in each divided region.

JP 2005-268925 A JP 2007-293660 A JP 2007-317166 A JP 2008-186349 A

In the PD split type optical beacon, for example, the uplink transmission position can be specified in more detail by calculating the ratio of the light receiving levels of the light receiving units (PD) in the adjacent divided areas generated by one uplink light. (See paragraphs 0065 to 0066 of Patent Document 4).
As described above, in the PD split type optical beacon, if the ratio of the received light levels generated in the light receiving portions of the adjacent divided areas is used, the position determination accuracy in the vehicle traveling direction can be suppressed to be less than the length of the divided areas.

However, among the plurality of divided areas arranged in the vehicle traveling direction, in the case of the most downstream divided area (UA1: in FIG. 3, hereinafter referred to as “final divided area”), there are others on the downstream side. Therefore, for the subdivision area at the downstream end of the final divided area (A10 in FIG. 7; hereinafter, sometimes referred to as “final area”), the received light level corresponding to the adjacent divided area is It is not possible to subdivide the area using the ratio.
Therefore, conventionally, for such a final area, a position where the light receiving level of the light receiving unit of the final divided region is lower than the threshold is defined as a representative point of the final area (L0 in FIG. 7), and the uplink light generated in the final area When the received light level falls below the threshold, the stored representative point is specified as the uplink reception position of the final area.

However, it has been found that such a conventional position identification method has the following problems.
That is, the intensity of the uplink light transmitted from the vehicle varies depending on the performance of the in-vehicle device itself, the degree of dirt on the windshield, etc., so in order to maintain the detection accuracy of the uplink light in the final divided area, It is necessary to set the threshold value (fixed value) of the light receiving unit corresponding to the final divided region to be relatively small.

However, the distribution of the received light level with the vehicle advancing direction as the horizontal axis is, as shown in FIG. 7, for example, a substantially symmetrical left and right mountain shape with a wide base, so the threshold of the light receiving unit corresponding to the final divided region is reduced. The representative point of the final area moves to the downstream side as it goes.
For this reason, in order to maintain the detection accuracy of uplink light, if the threshold for the light receiving unit corresponding to the final divided region is set low, the final area becomes too wide on the downstream side, and the desired position location accuracy for the final area is reached. May not be obtained.

  In view of such a situation, an object of the present invention is to improve the positioning accuracy of an uplink reception position in a final division area in a PD division type optical beacon.

Hereinafter, although the technical feature of the optical beacon of the present invention will be described in this column, in the present specification, a plurality of divided regions, light receiving portions, and subdivided areas are described as follows as necessary.
Divided area: UA _i (where i is 1, 2,... M in order from the downstream side)
Light receiving part: PD _i (i corresponds to the case of the divided area)
Subdivision area: A _j (where j is 1, 2, ... n in order from the upstream side)
Further, in this specification, when a divided area, a light receiving unit, and a subdivision area are described by putting actual numbers in the subscripts i and j, normal full-width characters are used for easy identification, for example, “ It is displayed as “UA1”, “PD1”, “A1”. The same applies to the other subscript signed (V _i and L _k, etc.).

(1) The optical beacon of the present invention is based on a plurality of PD _i respectively corresponding to a plurality of UA _i arranged in the vehicle traveling direction and a light reception level generated in each PD _i when uplink information is received from the vehicle. one of the representative points of the subdivided a _j in the vehicle traveling direction _i, and the a _j position specifying unit that specifies as the uplink receiving position in, the PD1 of the light-receiving level, the total at the boundary position of the UA _i equal to the value obtained by multiplying a predetermined coefficient to the sum of light receiving level of PD _i, and a, a storage unit for previously storing a downstream end position of the a _n.

On top of that, the light beacon of the present invention, the position specifying unit, when the uplink reception position the previously identified is in the range from the boundary position up to A _n-1, the threshold value for A _n, previous the updated to a value obtained by multiplying a predetermined coefficient, when the current uplink receiving position is contained in a _n, the current uplink information to the total value of the light receiving levels of all PD _i of the uplink information when receiving The stored downstream end position is adopted as a representative point of the An on condition that the received light level of the PD1 at the time of reception is _equal to or higher than the updated threshold value.

According to the optical beacon of the present invention, the light receiving level of the PD1, the value and equal position multiplied by the predetermined coefficient to the sum of light receiving level of the total PD _i at the boundary position of the UA _i, of A _n is the last area since the downstream end position, can be according to the value of the predetermined coefficient sets downstream end position of the a _n on the upstream side of the normal.
Further, according to the optical beacon of the present invention, the position specifying unit, a threshold value for A _n, is updated to a value obtained by multiplying a predetermined coefficient to the sum of light receiving level of the total PD _i upon receiving the last uplink information since, also set on the upstream side of the normal to the downstream end position of a _n as described above, regardless of the emission intensity of the uplink information, determines whether the received position is contained in a _n be able to.

Thus, according to the optical beacon of the present invention, setting the downstream end position of the A _n on the upstream side of the normal, since the uplink receiving position can be determined whether or not contained in A _n, The positioning accuracy of the uplink reception position in UA1 can be improved.

The “total value of the received light levels of all PD _i at the boundary position of UA _i ” in the present invention is the boundary position when there are three or more (m ≧ 3) PD _i corresponding to UA _i. In the case of including PD _{i in} which the light reception level at 0 is almost zero, it means that the total value is calculated by excluding the light reception level of PD _i from the beginning.
That is, for example, when there are four PD _i (m = 4), the light receiving levels V1, V2 of PD1 and PD2 corresponding to the two UA1 and UA2 at the boundary position L2 between the two UA1 and UA2 adjacent to each other. However, when the light receiving levels of the other PD3 and PD4 are almost zero at the boundary position (see FIG. 8), the values of the light receiving levels V1 to V4 of the four PD1 to PD4 are not necessarily added. There is no need to do this, and the total value of the light receiving levels V1 and V2 of PD1 and PD2 may be substituted.

(2) In the optical beacon of the present invention, if the boundary position of the UA _i have multiple, the storage unit may store a downstream end position of the A _n corresponding to a plurality of the boundary position, the localization parts, based on whether the previous uplink receiving position is included in any of the plurality of a _j, determining whether to adopt any of a plurality of said downstream end position as the representative point a _n It is preferable.

In this case, since an appropriate one can be selected from a plurality of downstream end positions based on the previous uplink reception position, even if the emission intensity of the uplink information changes for each vehicle, the intensity of the uplink information is increased. in the corresponding appropriate precision, it is possible to identify the uplink reception position for a _n.
(3) More specifically, in the position specifying portion, equal at the boundary position of the UA _i upstream of the previous uplink receiving position, a value obtained by multiplying the predetermined coefficient to the received light level of all the PD _i A _n of the downstream end position, it may be employed as the representative point of the a _n.

(4) In the optical beacon of the present invention, the predetermined coefficient is preferably 0.5 or more. This is because when a predetermined coefficient is below 0.5, the downstream end position of the A _n is not much different from the normal, it can not be less improved position location accuracy at UA1.
Incidentally, by setting the predetermined coefficient to 0.5, since it measured accurately downstream end position of the A _n, there is an advantage that it is possible to store an accurate downstream end position in the storage unit.

(5) Moreover, in the optical beacon of the present invention, it is preferable that the predetermined coefficient is a value equal to or less than a maximum value of a ratio of light reception levels of both PD _i for adjacent UA _i . The reason is that when the predetermined coefficient exceeds the maximum value of the ratio, the threshold value to be dynamically updated becomes too large, and the detection accuracy of the uplink reception position at UA1 is lowered.
In this case, near the predetermined coefficient to the maximum value of the ratio value (e.g., alpha = 0.8) is set to, the accuracy falls as actual measurement value of the downstream end position of the A _n, a downstream end position of the A _n Can be set on the more upstream side, so that the positioning accuracy at UA1 can be improved.

(6) The optical beacon of the present invention includes a transmitter that transmits downlink information, and the downlink information that is transmitted after receiving the uplink information, and the downstream side from the uplink reception position that is specified by the position specifying unit. It is preferable to further include a communication control unit including distance information regarding the distance to the predetermined position.
In this case, the communication control unit, so include the distance information on the distance from the uplink reception position position specifying unit has identified to a predetermined position on the downstream side in the down-link information, the vehicle accurately uplink receiving position with respect to A _n Can be notified.

  (7) The method for specifying the uplink reception position of the present invention relates to the specifying method performed by the optical beacon of the present invention, and has the same effects as the optical beacon of the present invention.

  As described above, according to the present invention, since the downstream end position of the final area can be set upstream of the normal area, it is possible to improve the positioning accuracy of the uplink reception position in the final divided area.

1 is a block diagram showing an overall configuration of a road-vehicle communication system according to an embodiment of the present invention. It is a top view of an optical beacon. It is a side view which shows the communication area | region of an optical beacon. It is a schematic block diagram of a vehicle equipment and a vehicle carrying this. It is a block diagram which shows an example of the circuit structure of an optical receiver and a beacon controller. It is a conceptual diagram which shows the procedure of road-to-vehicle communication. It is a distribution map of the light reception level of each light-receiving part when a vehicle advancing direction is made into a horizontal axis. FIG. 8 is a distribution diagram corresponding to FIG. 7 for illustrating a method of actually measuring the downstream end position of the final area. It is a table | surface which shows the identification method of the uplink receiving position by a position specific part. It is a flowchart which shows the selection process of the representative point about the last area. It is a continuation of the flowchart of FIG. FIG. 6 is a distribution diagram of light reception levels actually measured (when α = 0.8). FIG. 6 is a distribution diagram of light reception levels actually measured (when α = 0.5).

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Overall system configuration]
FIG. 1 is a block diagram showing an overall configuration of a road-vehicle communication system according to an embodiment of the present invention. As shown in FIG. 1, the road-to-vehicle communication system of the present embodiment includes an infrastructure-side traffic control system 1 and an in-vehicle device 2 mounted on a vehicle C (see FIG. 3) traveling on a road R. .
The traffic control system 1 includes a central device 3 provided in a control room, and a large number of optical beacons (optical vehicle detectors) 4 installed at various locations 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.

[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 beacon controller 7. And a plurality (four in the illustrated example) of beacon heads (projector / receiver) 8 connected to the sensor interface.
Each beacon head 8 has a plurality of light receiving parts 9 constituted by photodiodes (PDs) and a light projecting part 10 constituted by light emitting diodes (LEDs), which are housed inside the casing. (See FIG. 3).

The light projecting unit 10 projects (transmits) downlink light DO (an optical signal constituting the downlink information 34 and 36) made of near infrared rays to a communication area A described later.
The plurality of light receiving units 9 receive uplink light UO (an optical signal constituting the uplink information 35) made of near infrared rays from the vehicle-mounted device 2, and each of the uplink areas UA described later. It is provided corresponding to the divided areas UA1 to UA4.

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. A plurality of beacon heads 8 and one beacon controller 7 serving as a control unit that collectively controls the beacon heads 8.

The beacon controller 7 includes a programmable microcomputer having a CPU, a memory (RAM), and a storage device (ROM). The beacon controller 7 uses a communication unit 6 (see FIG. 1) for bidirectional communication with the central device 3 and a beacon head 8. It has the function as the communication control part 49 which performs road-to-vehicle communication with the vehicle equipment 2.
The contents of road-to-vehicle communication between the beacon controller 7 and the in-vehicle computer 26 (FIG. 6) will be described later.

The beacon controller 7 stores a computer program for executing predetermined functions in its own storage device 48 (see FIG. 5). The functional parts executed by this program include the communication control unit 49 related to road-to-vehicle communication and the position of the in-vehicle device 2 at the moment of receiving the uplink light UO from the in-vehicle device 2 (hereinafter referred to as “uplink reception position”). .) Is specified (see FIGS. 1, 2 and 4).
The processing content performed by the position specifying unit 50 will also be described later.

The beacon controller 7 is installed on a support column 13 standing on the side of the road. Each beacon head 8 is attached to an erection bar 14 installed horizontally on the road R side from the column 13, and is arranged immediately above each lane R <b> 1 to R <b> 4 of the road R.
The light projecting unit 10 of each beacon head 8 emits near infrared rays toward the upstream side in the vehicle traveling direction from directly below the lanes R <b> 1 to R <b> 4. A communication area A for performing the above is set on the upstream side of the head 8.

[About communication area]
FIG. 3 is a side view showing the communication area A of the optical beacon 4.
As shown in FIG. 3, the communication area A of the optical beacon 4 is a downlink area in which the in-vehicle head 27 that is a projector / receiver of the in-vehicle device 2 can receive downlink information (an area in which solid line hatching is provided in FIG. 3). DA and the beacon head 8 of the optical beacon 4 are composed of an uplink area (area provided with broken-line hatching in FIG. 3) UA in which uplink information from the in-vehicle head 27 can be received.

In FIG. 3, the downlink area DA is a range indicated by Δdac with the projecting / receiving position d of the beacon head 8 and the positions a and c at the 1.0 m level from the road surface as vertices, and the uplink area UA is , A light emitting / receiving position d, and a range indicated by Δdbc with apexes at positions b and c at a level of 1.0 m from the road surface.
Accordingly, the upstream end c of the downlink area DA and the uplink area UA coincide with each other, and the uplink area UA overlaps with the upstream portion (right side portion in FIG. 3) of the downlink area DA in the vehicle traveling direction. Further, the vehicle traveling direction length of the downlink area DA coincides with the same direction length of the entire communication area A.

According to the “near infrared interface standard” of the optical beacon (optical vehicle sensor) 4, the formal area dimensions of the downlink area DA and the uplink area UA are defined.
In the case of the optical beacon 4 for general roads, the upstream end c of the uplink area UA is about 6.04 m from directly below the head at a height of 1 m from the road surface, and the downstream end b of the uplink area UA is It is set to 3.4 m from directly below the head at the same height. Accordingly, the total length of the official communication area A in the vehicle traveling direction (the length between bc) is about 3.6 m.

The uplink area UA of the present embodiment is composed of divided areas UA1 to UA4 obtained by dividing the area UA into a plurality (four in the illustrated example) in the vehicle traveling direction.
The four light receiving units 9 (PD1 to PD4) provided in the beacon head 8 use the divided areas UA1 to UA4 of the uplink area UA as light receiving areas, respectively. Therefore, for example, the uplink light UO transmitted from the in-vehicle head 27 in the divided area UA4 located on the most upstream side is mainly received by the PD 4 corresponding to the divided area UA4.

[Configuration of in-vehicle device and vehicle]
FIG. 4 is a schematic configuration diagram of an in-vehicle device 2 that performs road-to-vehicle communication with the optical beacon 4 and a vehicle C in which the in-vehicle device 2 is mounted.
As shown in FIG. 4, the vehicle C includes a vehicle body 21 having a driver's boarding seat (not shown), an in-vehicle device 2 mounted on the vehicle body 21, and an electronic control device that integrally controls each part of the vehicle C. (ECU) 22, an engine 23 that drives the vehicle body 21, a brake device 24 that brakes the vehicle body 21, and a speed detector 25 that constantly detects the current speed of the vehicle C.

The ECU 22 performs various controls on the vehicle C, such as drive control of the engine 23 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 26, an in-vehicle head (projector / receiver) 27 connected to the sensor interface of the computer 26, a display 28 and a speaker device 29 as a human interface for the driver of the passenger seat. Yes.

The vehicle-mounted head 27 includes a light projecting unit made of a light emitting diode (LED) and a light receiving unit made of a photodiode (not shown), like the light beacon light projecting / receiving device 8.
The light projecting unit transmits uplink light UO (uplink information 35) made of near infrared rays, and the light receiving unit is downlink light DO (downlink information 34, 36) made of near infrared rays emitted to the communication area A. Is received.

The in-vehicle computer 26 includes a programmable microcomputer having a CPU, a memory (RAM), and a storage device (ROM), and performs control processing for road-to-vehicle communication with the optical beacon 4 by the in-vehicle head 27.
The in-vehicle computer 26 stores a program for executing each predetermined function in a storage device, and includes a distance recognition unit 30 and a support control unit 32 as functional units executed by the program. The processing contents of these functional units 30 and 32 will be described later.

[Circuit configuration of beacon controller, etc.]
FIG. 5 is a block diagram illustrating an example of a circuit configuration of the optical receiver of the optical beacon 4 and the beacon controller 7.
In FIG. 5, four light receiving portions 9 (PD1 to PD4) are arranged in the beacon head 8 with photodiodes that function independently from each other being placed close to each other, and each light receiving portion 9 is divided into road-side divided areas UA1 to UA4, respectively. It corresponds to.

Among the four light receiving units 9 (PD1 to PD4), PD1 corresponds to the most downstream divided area (final divided area) UA1 in the communication area A, and PD2 to PD4 are respectively 2 from the downstream side. This corresponds to the third, fourth and fourth divided areas UA2 to UA4.
PD1 to PD4 may be arranged by arranging a plurality of photodiodes made of independent substrates, or arranged by arranging a plurality of elements that function independently from each other on a single substrate. Also good.

The optical receiver of the optical beacon 4 includes the PD1 to PD4, a plurality of amplifier circuits 42 that amplify these output voltages, an adder 43 on the rear stage side of the amplifier circuit 42, a comparator 44, and a detector circuit 46. These circuits or elements are mounted on a plurality of beacon heads 8 corresponding to the lanes R1 to R4, respectively.
The amplifying circuit 42 includes an amplifying element made of an n-type MOSFET or the like, and a plurality of operational amplifiers for further amplifying the output voltage of the element, and amplifies the output voltage of PD1 to PD4 on the order of 10,000 to 100,000 times, for example.

The output side of the amplifier circuit 42 is connected to a single adder 43, and the comparator 44 is connected to the output side of the adder 43.
The output voltage from each amplifier circuit 42 is superimposed on one analog signal by the adder 43. Further, the analog signal output from the adder 43 is converted into a digital signal by the comparator 44 and sent to the processor 45 of the beacon controller 7. The processor (CPU) 45 extracts a data signal and a communication control signal included in the uplink information 35 from the digital signal sent from the comparator 44.

The output side of each amplifier circuit 42 is connected to a detection circuit 46, and the output side of these detection circuits 46 is connected to an A / D converter 47 in the beacon controller 7.
The output voltage of each amplifier circuit 42 is smoothed by the detection circuit 46, converted to a digital signal by the A / D converter 47 in the subsequent stage, and sent to the processor 45 of the beacon controller 7.

The processor 45 acquires the light reception levels V1 to V4 of the PD1 to PD4 from the digital signal of the A / D converter 47, and compares the light reception levels V1 to V4 with a predetermined threshold value between the light reception levels V1 to V4. Based on the ratio, it is possible to specify at which position in the uplink area UA the uplink light UO is received.
Therefore, the processor 45 executes the computer program stored in the storage device 48, thereby realizing not only a communication control function for road-to-vehicle communication but also a function realization means for an uplink reception position specifying function based on the light reception level. Become.

The storage device 48 stores computer programs related to the above functions, and stores threshold values Th1 to Th4 for determining whether or not the PD1 to PD4 receive the uplink light UO.
That is, the processor 45 and the storage device 48 constitute the position specifying unit 50 (see FIGS. 1, 2, and 4) that specifies the uplink reception position based on the light reception levels of PD1 to PD4.

  The processor 45 is mounted on the vehicle based on a data signal included in the uplink information 35, information on the uplink reception position from the specified vehicle-mounted device 2, information given from the central device 3 via the communication unit 6, and the like. Information to be transmitted to the machine 2 can be generated.

[Contents of road-to-vehicle communication (processing contents of communication control unit)]
FIG. 6 shows a two-way road-to-vehicle communication procedure performed between the beacon head 8 and the vehicle-mounted head 27 in the communication area A. Hereinafter, the contents of the road-to-vehicle communication of the present embodiment will be described with reference to FIG.

First, the beacon controller 7 (communication control unit 49) of the optical beacon 4 includes, from the beacon head 8 corresponding to each lane R1 to R4, first lane notification information including first lane information before downlink switching. The downlink information 34 is continuously transmitted in the predetermined transmission cycle to the downlink area DA of each lane R1 to R4 (F1 in FIG. 6).
At this stage, the vehicle ID is not yet stored in the lane notification information.

When the vehicle C equipped with the in-vehicle device 2 enters the actual downlink area DA, the in-vehicle head 27 of the in-vehicle device 2 receives the first downlink information 34 including the lane notification information (no vehicle ID).
At this time, the in-vehicle computer 26 of the in-vehicle device 2 recognizes that the vehicle C exists in the actual communication area A. Thereafter, the in-vehicle computer 26 starts transmission of the uplink information 35 (F2 in FIG. 6), and transmits this uplink information 35 to the beacon head 8 at a predetermined transmission cycle (uplink transmission cycle) (FIG. 6). 6 F3).

The in-vehicle computer 26 stores the specific vehicle ID of the vehicle C in the uplink information 35 and transmits the uplink information 35. If the in-vehicle computer has travel time information between beacons, this information is also uploaded. It is included in the link information 35.
The in-vehicle computer 26 continues to transmit the uplink information 35 until it recognizes that the beacon controller 7 of the optical beacon 4 has switched the downlink.

  On the other hand, when the beacon head 8 of the optical beacon 4 receives the uplink information 35 (F4 in FIG. 6), the beacon controller 7 (communication control unit 49) performs downlink switching, and vehicle ID information as second information. The transmission of the second downlink information 36 including the lane notification information having the following information is started (F5 in FIG. 6), and the transmission of the second downlink information 36 is repeated as much as possible within a predetermined time (F6 in FIG. ).

The lane notification information includes a field for storing a vehicle ID for each lane R1 to R4 (FIG. 2), and a lane number can be assigned to each vehicle ID.
For this reason, the in-vehicle computer 26 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 second downlink information 36 includes traffic information, section travel time information, event regulation information, and support information for safe driving support for the driver, in addition to the lane notification information including the vehicle ID. Yes.
The support information includes signal information that is timing information for changing the lamp color of the traffic light downstream from the optical beacon 4 and the uplink area UA based on the reception position of the uplink optical UO specified by the position specifying unit 50. “Distance information” regarding the distance to a predetermined position on the downstream side (for example, the stop line 40 shown in FIG. 7) is included.

As shown in FIG. 6, the second downlink information 36 includes a single or a plurality of minimum frames 37. According to the “near infrared interface standard”, the data amount of the minimum frame 37 is defined as a total of 128 bytes, and 5 bytes are allocated to the header portion 38 and 123 bytes are allocated to the actual data portion 39.
According to the standard, the second downlink information 36 can be composed of 1 to 80 minimum frames 37, and the transmittable time is set to 250 ms. The downlink information 36 includes an arbitrary number of minimum frames 37 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 37 is about 1 ms. Therefore, for example, when one downlink information 36 is constituted by three minimum frames 37, the transmission period of the downlink information 36 is about 3 ms. Therefore, the downlink information 36 has a predetermined transmittable time (250 ms). ) Will be repeatedly transmitted about 80 times during this period.
The in-vehicle computer 26 of the in-vehicle device 2 recognizes the downlink switching in the optical beacon 4 at the time of receiving the second downlink information 36 (F7 in FIG. 6), and transmits the uplink information 35 at this time. Stop.

[Contents of safe driving support]
When the in-vehicle head 27 receives the second downlink information 36 including the distance information, the distance recognition unit 30 (see FIG. 4) of the in-vehicle computer 26 displays the distance information ( 7 is recognized as the distance from the own vehicle to the stop line 40. As shown in FIG. 7, “L” is a distance from the reference position Pr to the stop line 40, and “LEN (k)” is a correction distance from the reference position Pr to each of the representative points L0 to L9.

The support control unit 32 of the in-vehicle computer 26 performs safe driving support for the driver using the distance information recognized by the distance recognition unit 30.
For example, the support control unit 32 determines a deceleration (negative acceleration) for stopping before the stop line 40 from the distance to the stop line 40 notified from the optical beacon 4 and the current traveling speed of the vehicle C. ) And the deceleration is notified to the ECU 22.
The ECU 22 operates the brake device 24 so as to achieve the deceleration, whereby the vehicle C can be automatically stopped before the stop line 40.

Further, the safe driving support of the support control unit 32 may be alerting the driver using the display 28 or the speaker device 29.
For example, the distance to the stop line 40 (L-LEN (k)) may be displayed on the display 28 by the support control unit 32. When the current traveling speed of the vehicle C is too fast, the support control unit 32 displays a warning for stopping or decelerating on the display 28, or outputs the warning from the speaker device 29 as a voice. May be.

Further, the support control unit 32 can also perform safe driving support using signal information included in the second downlink information 36.
Here, the signal information refers to information related to the current or future signal lamp color displayed by the traffic signal device, and includes information (display schedule information) regarding the display continuation period of each signal lamp color, the display order, and the like. For example, “the current lamp color is blue and the scheduled duration is 5 seconds, the next lamp color is yellow and the scheduled duration is 8 seconds, and the next lamp color is a right turn blue arrow lamp and the scheduled duration is 10 seconds. It is information such as “second”.

The support control unit 32 of the in-vehicle computer 27 that has received this signal information estimates the required time to reach the stop line 40 from the distance to the stop line 40, the traveling speed of the vehicle C, and the like, and then the required time. The signal lamp color after the lapse can be estimated.
For example, if the current signal lamp color is a blue signal, but the signal lamp color is predicted to be a red signal when arriving at the stop line 40, it can be safely stopped before the stop line 40. Thus, control for braking the vehicle C is performed. Conversely, if it can be determined that the vehicle can safely pass through the intersection unless the vehicle is decelerated, the control for maintaining the speed of the vehicle C can be performed.

In order to brake the vehicle C or maintain the speed, the support control unit 32 may directly control the brake device 24 (FIG. 4) and the accelerator of the vehicle.
Further, the support control unit 32 may simply generate information related to braking and speed maintenance and notify the ECU 22 of the information to control the brake device 24 and the accelerator by the ECU 22. That is, the support control unit 32 may perform indirect control. In addition, the support control unit 32 may perform not only control led by the in-vehicle device but also operation for assisting the driving operation of the driver such as brake assist.

The support control unit 32 may notify the passenger of the vehicle C of the result of the signal lamp color estimation by voice or image information. For example, sound such as “Since the signal changes soon and should be stopped” is emitted from the speaker device 29 to the driver, or displayed on the display 28 such as a head-up display or a navigation device with characters or symbols. Can do.
For safe driving assistance, a human interface that does not notify the driver of information at an inappropriate timing or content, for example, it is possible to prevent notification by voice or image display during low-speed driving .

The signal information may be only the currently displayed lamp color and its duration, or information for one cycle may be provided collectively. Further, in addition to these pieces of information, parameter information related to the control, information on a time zone in which the control is performed, and the like may be included at the point where the point sensitive control is performed.
The signal information may be acquired from an optical beacon or may be acquired from an infrastructure device other than the optical beacon.

  In the latter case, for example, when the signal controller of the traffic signal is equipped with a wireless communication device, it may be acquired from the wireless communication device, or may be acquired by inter-vehicle communication from the preceding vehicle that acquired the signal information. Also good. The signal information receiving unit that receives the signal information may use the in-vehicle head 27 or may be another receiver provided in the in-vehicle device 2.

[Subdivision area and its representative points]
FIG. 7 is a distribution diagram of the light reception levels V1 to V4 of the light receiving units 9 (PD1 to PD4) when the vehicle traveling direction is taken as the horizontal axis.
First, the meaning of each symbol in FIG. 7 will be described as follows.
V1: PD1 light reception level (detected PD voltage: mV)
V2: PD2 light receiving level (detected PD voltage: mV)
V3: PD3 light reception level (detected PD voltage: mV)
V4: PD4 light reception level (detected PD voltage: mV)

Th1: PD1 threshold (mV)
Th2: PD2 threshold (mV)
Th3: PD3 threshold (mV)
Th4: PD4 threshold (mV)
In the present embodiment, Th1 = Vdf = 100 mV, Th2 = 100 mV, Th3 = 85 mV, and Th4 = 70 mV are set. However, the fixed value of the threshold is not limited to these values.

Pr: Reference position on the road R (5m upstream from the position H immediately below the head)
P0: a predetermined position on the downstream side of the beacon (position of the stop line 40)
L: Path distance from Pr to P0 A _j : Subdivision area obtained by subdividing each UA _i (i = 1 to 4) (j = 1, 2,... 10)
L _k : representative point defined for each A _j (k = 0, 2,... 9)

Here, as shown in FIG. 7, the light receiving levels V1 to V4 (PD voltage: mV) of PD1 to PD4 mounted on the beacon head 8 are left-right symmetric with the vehicle traveling direction as the horizontal axis. The distribution is substantially mountain-shaped, and adjacent PD _i overlap each other in a range of about half of the maximum width.
Further, when the beacon head 8 is not tilted (that is, when the beacon head 8 is installed horizontally), the intensity of the uplink light UO decreases as the distance from the beacon head 8 decreases. The amplitude of the PD voltage gradually decreases in the order of ~ V4.

Therefore, in this embodiment, by utilizing the above distribution characteristic of the light receiving levels V1-V4, and the boundary position of the UA _i, the subdivision area A _j of the distance obtained by dividing a predetermined subdivision number N between the boundary positions newly The resolution of the position location that can be specified by the light reception levels V1 to V4 of each PD _i is increased.
That is, the “boundary position” of each divided region is set to a position where V _i = V _{i + 1} (L2, L5, L8 in FIG. 7), and a subdivision area A _j is further defined by further dividing the distance between the boundary positions. .

Specifically, intermediate positions where the light reception levels V _i and V _{i + 1 of} PD _i and PD _{i + 1} whose divided areas are adjacent to each other have a constant ratio m1 / m2 or the inverse m2 / m1 are defined, and these intermediate positions are defined. Each of the divided areas is subdivided by using as a boundary.
For example, in the example of FIG. 7, the ratio m1 / m2 is 9/1, for example, and the intermediate position where V4 / V3 = 9 is L9. The most upstream divided area UA4 is subdivided into two areas A1 and A2 with the intermediate position L9 as a boundary.

The intermediate position where V4 / V3 = 1/9 is L7, and the intermediate position where V3 / V2 = 9 is L6. UA3 which is the second divided area from the upstream side is subdivided into three areas A3 to A5 with these two intermediate positions L7 and L6 as a boundary.
Similarly, the intermediate position where V3 / V2 = 1/9 is L4, and the intermediate position where V2 / V1 = 9 is L3. UA2, which is the third divided region from the upstream side, is subdivided into three areas A6 to A8 with these two intermediate positions L4, L3 as a boundary.

Furthermore, the intermediate position where V2 / V1 = 1/9 is L1. UA1, which is the most downstream divided region, is subdivided into two areas A9 and A10 with this intermediate position L1 as a boundary.
As described above, if the ratio of the light receiving levels V _i and V _{i + 1} corresponding to the adjacent divided areas is used, a subdivision area A _j less than the length of the divided area can be defined in each divided area. Can be subdivided into areas of finer length.

In the present embodiment, the downstream end position of each A _j (j = 1, 2,... 10) is defined as the representative point of the area. That is, in the example of FIG. 7, the representative point of A1 is L9, the representative point of A2 is L8, the representative point of A3 is L7,.
The beacon controller 7 of the present embodiment is configured so that the positions of the representative points L0 to L9 (specifically, the correction distance LEN (k) from the reference position Pr to the representative points L0 to L9: k = 0, 1,... ... 9) are stored in the storage device 48 in advance.

The data input operation for storing the correction distance LEN (k) in the storage device 48 of the beacon controller 7 is performed as follows, for example.
1) If the light reception levels V1 to V4 are monitored, the vehicle equipped with the simulated vehicle-mounted device 2 that emits the uplink light UO at a certain level is slowly moved from the point upstream of the reference position Pr toward the point H immediately below the beacon. Let it run.
2) In a state where V4 exceeds Th4, a position L9 where V3 / V4 = 1/9 is searched, and a correction distance LEN (9) from this position L9 to Pr is input to the storage device 48.

3) In a state where V4 exceeds Th4, a position L8 where V3 / V4 = 1 is searched, and a correction distance LEN (8) from this position L8 to Pr is input to the storage device 48.
4) In a state where V3 exceeds Th3, a position L7 where V3 / V4 = 9 is searched, and a correction distance LEN (7) from this position L7 to Pr is input to the storage device 48.
Similarly, the remaining positions L6 to L9 are searched based on the ratio of the received light levels between the adjacent PD _i , and the correction distance LEN (k) (k = 6, 5...) From these positions L6 to L9 to Pr. 9) are input to the storage device 48, respectively.
5) V1 is the light reception level of PD1 corresponding to UA1 located on the most downstream side, and since position L0 cannot be specified using the ratio of the light reception levels, position L0 where V1 is equal to Th1 (= Vdf) Search is performed, and the correction distance LEN (0) from the position L0 to Pr is input to the storage device 48.

[Distance correction processing and notification to the vehicle]
Position specifying unit 50 of the beacon controller 7, the process of selecting representative points L _k, which will be described later correction distance LEN (k) (FIG. 9) is found, by subtracting the correction distance LEN (k) from the journey distance L real The distance (= L−LEN (k)) is calculated, and this actual distance is notified to the beacon controller 7.
The beacon controller 7 stores the notified actual distance (= L-LEN (k)) in the transmission frame of the second downlink information 36 as distance information, and repeatedly transmits this transmission frame from the beacon head 8. .

For example, as shown in FIG. 7, when the actual uplink optical UO is transmitted at A4, the position specifying unit 50 subtracts the correction distance LEN (6) from the journey distance L (L-LEN (6)). The communication control unit 49 stores the value in the second downlink information 36.
In this case, an error β corresponding to the area length of A4 at the maximum is included between the representative point L6 of A4 and the actual uplink reception position.

However, in the present embodiment, the area length of A4 is shortened to about 30 cm by dividing UA3 into three equal parts, so there is no particular problem in the magnitude of error β itself, and A4 is a representative point of A4. Since the downstream end position L6 is employed, the vehicle C side is always notified of distance information that is slightly shorter than the true distance and slightly shifted to the safe side.
For this reason, even if the vehicle-mounted device 2 provides safe driving support based on the above actual distance, troubles such as the vehicle C overrunning the stop line 40 will not occur.

Further, in this embodiment, the beacon 4 side does not perform the distance correction calculation, but stores both the road distance L and the correction distance LEN (k) in the downlink information 36, and performs the correction process for calculating the actual distance. You may decide to do it on the side.
Alternatively, when the vehicle C previously stores the travel distance L, only the correction distance LEN (k) is stored in the downlink information 36, and correction processing for calculating the actual distance is performed on the vehicle C side. May be.

[Problems in the final area]
By the way, as shown in FIG. 7, in the case of the most downstream UA1 (final divided region) among the plurality of divided regions, there is no other divided region downstream from this, so the downstream end of UA1 As for A10 constituting the part, the area cannot be subdivided using the ratio with the light reception level corresponding to the adjacent divided region.

On the other hand, since the intensity of the uplink light UO transmitted from the vehicle C varies depending on the performance of the vehicle-mounted device 2 itself, the degree of dirt on the windshield, and the like, in order to maintain the detection accuracy of the uplink light UO in the UA1. Therefore, it is necessary to set the threshold Th1 of PD1 corresponding to UA1 to be relatively small.
However, as shown in FIG. 7, the distribution of the received light level with the vehicle traveling direction as the horizontal axis is a substantially symmetrical left-and-right mountain shape with a wide base, so that the threshold Th1 (= Vdf) of PD1 corresponding to UA1. As A becomes smaller, the representative point L0 of A10 moves to the downstream side.

Therefore, if the threshold value for UA1 is set low to maintain the detection accuracy of the uplink optical UO, A10 becomes too wide on the downstream side, and the desired position location accuracy may not be obtained in A10.
Therefore, in the present embodiment, the downstream end positions “L0 ′ ″”, “L0 ′”, “L0 ″” of A10 corresponding to the threshold values Vb, Vc, Vd higher than the normal fixed value Vdf of Th1 (FIG. 8) is measured and stored in the storage device 48, and which of the positions “L0 ′ ″”, “L0 ′”, and “L0 ″” is used as the representative point of A10 is determined last time. By dynamically determining using the uplink light UO corresponding to the amount of light received, the maintenance of the detection accuracy of the uplink light UO and the improvement of the positioning accuracy by shortening the final area (A10) are made compatible.

[Measurement method of downstream end position of final area]
FIG. 8 is a distribution diagram corresponding to FIG. 7 for illustrating a method of actually measuring the downstream end position of the final area (A10). Hereinafter, with reference to FIG. 8, the actual measurement method and the conditions for selecting the actually measured downstream end position will be described.
As described above, the light receiving level V1-V4 of PD1~PD4 are overlapped with each other in a range of about half of the maximum width in PD _i adjacent to each other, the amplitude of the PD voltage gradually decreases in the order of V1-V4.

Accordingly, paying attention to the total value Vsum (= V1 + V2 + V3 + V4) of the light receiving levels of all PD _i , when a characteristic curve CL is drawn by multiplying this Vsum by a predetermined coefficient α (α = 0.9 in this embodiment), FIG. As shown in FIG. 4, the characteristic curve CL is a curve that monotonously increases so as to increase toward the downstream side from approximately A2 to A9.
In addition, the distribution of the light reception levels V1 to V4 of each PD _i is such that when the intensity of the uplink light UO changes, the amplitude in the vertical axis only expands and contracts, and the phase in the horizontal axis hardly changes. The relative position of each distribution in the vehicle traveling direction hardly changes regardless of the intensity of the uplink light UO.

Therefore, when the downstream end positions (representative points) L1 to L9 of the areas A1 to A9 other than A10 are actually measured locally, the value of Vsum × α is monitored at the same time, and the boundary positions L2, L5, L8 of the divided regions are monitored. Measure the downstream positions L0 ′ ″, L0 ′, L0 ″ where the values Vb, Vc, Vd of Vsum × α intersect the light receiving level V1 of the final divided area.
These positions L0 ′ ″, L0 ′, L0 ″ (specifically, distance values from the reference position Pr) are stored in advance in the storage device 48 as candidates for downstream end positions that can be representative points of A10. Remember.

At the boundary positions L2, L5, and L8 of the divided areas, the light reception levels of adjacent PD _i are the same value. Therefore, if the voltage values Vb, Vc, and Vd of Vsum × α are defined in different expressions, It is.
Vb: Value of Vsum × α when V1 = V2 Vc: Value of Vsum × α when V2 = V3 Vd: Value of Vsum × α when V3 = V4

As shown in FIG. 8, the downstream end positions L0 ′ ″, L0 ′, and L0 ″ all appear upstream from the downstream end position L0 corresponding to the default value Vdf (= 100 mV) of Th1. .
For this reason, any one of these downstream end positions L0 ′ ″, L0 ′, and L0 ″ is used as the representative point of A10 as compared to the conventional case where the representative point of A10 is operated only by L0. The area length of A10 can be shortened, and the positioning accuracy for A10 can be increased.

In the case of the distribution of the received light level illustrated in FIG. 8, the received light levels V3 and V4 of PD3 and PD4 are almost zero at the boundary position L2 where V1 = V2, so when obtaining Vsum of this boundary position L2. The light reception levels V3 and V4 may be excluded, and Vb may be obtained as Vsum = V1 + V2.
At the boundary position L5 where V2 = V3, the light receiving levels V1 and V4 of PD1 and PD4 are substantially zero. Therefore, when Vsum at the boundary position L5 is obtained, the light receiving levels V1 and V4 are excluded, and Vsum Vc may be obtained as = V2 + V3.

Similarly, at the boundary position L8 where V3 = V4, the light reception levels V1 and V2 of PD1 and PD2 are substantially zero. Therefore, when obtaining Vsum at this boundary position L8, the light reception levels V1 and V2 are excluded, Vd may be obtained as Vsum = V3 + V4.
As described above, when PD _{i in} which the light receiving level at certain boundary positions L2, L5, and L8 is almost zero is included, Vsum may be obtained by excluding the light receiving level of PD _i from the beginning. .

[Criteria for selecting representative points for the final area]
Therefore, when the optical beacon 4 is operated, it becomes a problem which downstream end positions L0 ′ ″, L0 ′, L0 ″ other than L0 should be selected under any conditions.
In this respect, in the range of A3 to A9, since the characteristic curve CL has a characteristic of becoming higher at the downstream side, the previous uplink light UO transmitted from the vehicle C is temporarily within the range of A3 to A5. When the current uplink light UO transmitted from the same vehicle C is in the range of A10, the light reception level V1 of PD1 generated by the current uplink light UO is Vsum × α generated by the previous uplink light UO. It is considered to be higher than the value of.

  Accordingly, when the previous uplink transmission position by the vehicle C traveling in the communication area A is A3 to A5, the value of Vsum × α generated by the previous uplink light UO is temporarily used as a threshold for A10. If the received light level V1 generated in PD1 by the current uplink light UO from the same vehicle C exceeds the threshold value, the current uplink reception position has been measured in advance. It can be considered that it is always upstream of “L0 ″” corresponding to Vd.

  Similarly, the previous uplink light UO transmitted from the vehicle C is in the range of A6 to A8, and the current uplink light UO transmitted from the same vehicle C is in the range of A10. In this case, the light receiving level V1 of PD1 generated by the current uplink light UO is considered to be higher than the value of Vsum × α generated by the previous uplink light UO.

  Therefore, when the previous uplink transmission position by the vehicle C traveling in the communication area A is A6 to A8, the value of Vsum × α generated by the previous uplink light UO is temporarily used as a threshold for A10. If the received light level V1 generated in PD1 by the current uplink light UO from the same vehicle C exceeds the threshold value, the current uplink reception position has been measured in advance. It can be considered that it was upstream from “L0 ′” corresponding to Vc.

  Further, similarly to the above, even when the previous uplink light UO transmitted from the vehicle C is within the range of A9, and the current uplink light UO transmitted from the same vehicle C is within the range of A10. The light reception level V1 of PD1 generated by the current uplink light UO is considered to be higher than the value of Vsum × α generated by the previous uplink light UO.

  Therefore, when the previous uplink transmission position by the vehicle C traveling in the communication area A is A9, the value of Vsum × α generated by the previous uplink light UO is temporarily stored as a threshold for A10. If the received light level V1 generated in PD1 by the current uplink light UO from the same vehicle C exceeds the threshold, the current uplink reception position is Vc that has been measured in advance. It can be considered that it was upstream from the corresponding “L0 ′ ″”.

[Method of identifying uplink reception position]
FIG. 9 is a table showing a method for specifying the uplink reception position by the position specifying unit 50. The position specifying unit 50 of the beacon controller 7 selects one of the representative points L _k of A _j based on the determination criteria shown in this table, and selects the selected representative point L _k from the vehicle C in the communication area A. The position (uplink reception position) where the uplink optical UO is received is specified.

Specifically, when V4 ≧ Th4 and m1 / m2 ≦ V4 / V3, the uplink reception position can be regarded as being in the range of A1, so the position specifying unit 50 sets the representative point L9 of A1 to the uplink. Specify as the receiving position.
Further, when V4 ≧ Th4 and 1 ≦ V4 / V3 <m1 / m2, the uplink reception position can be regarded as being in the range of A2, so the position specifying unit 50 sets the representative point L8 of A2 to the uplink. Specify as the receiving position.

Further, when V3 ≧ Th3 and m2 / m1 ≦ V4 / V3 <1, the uplink reception position can be regarded as being in the range of A3, and therefore the position specifying unit 50 sets the representative point L7 of A3 to the uplink. Specify as the receiving position.
Position specifying unit 50, and so on, the subdivision area to A9 except A10, when V1~V4 satisfies each criterion described in FIG. 9, one representative point L corresponding to the A _{j k} is specified as the uplink reception position.

On the other hand, when specifying the uplink reception position for the final subdivision area A10, the position specifying unit 50 determines a plurality of representative points L0, L0 ″, L0 ′ based on where the “previous area” is. , L0 '''and the selected representative point is specified as the uplink position.
The “previous area” refers to a subdivision area including the uplink reception position specified for the previous uplink optical UO.

Specifically, if there is no previous area (the first specific area is A10) or the previous area is A1 to A2, the position specifying unit 50 adopts the default value Vdf as the threshold Th1 and increases the current time. When the light reception level V1 of the link light UO is equal to or higher than the threshold Th1, L0 is selected as the representative point of A10.
Further, when the previous area is A3 to A5, the position specifying unit 50 adopts Vsum × α obtained for the previous uplink light UO as the threshold Th1, and the light reception level V1 of the current uplink light UO is When it is equal to or greater than the threshold Th1, L0 ″ is selected as the representative point of A10.

Similarly, when the previous area is A6 to A8, the position specifying unit 50 adopts Vsum × α obtained for the previous uplink light UO as the threshold value Th1, and the light reception level V1 of the current uplink light UO is When it is equal to or greater than the threshold Th1, L0 ′ is selected as the representative point of A10.
Further, even when the previous area is A9, the position specifying unit 50 adopts Vsum × α obtained for the previous uplink light UO as the threshold Th1, and the light reception level V1 of the current uplink light UO is equal to or higher than the threshold Th1. In this case, L0 ′ is selected as the representative point of A10.

  Thus, when the previous area is A3 to A9, the position specifying unit 50 sets Vsum × α of the previous uplink optical UO as the threshold Th1, and the previous area is A3 to A5, A6 to A8, or A9. Any one of L0 ″, L0 ′, and L0 ′ ″ is selected depending on which range.

[Process of selecting representative points for the final area]
FIG. 10 is a flowchart showing representative point selection processing for the final area, which is performed by the position specifying unit 50. Hereinafter, the method for selecting the representative point of the final area will be described in more detail with reference to FIG.
In the flowchart of FIG. 10, “RN” is a variable that represents the identification result of the current uplink reception position, and “RA” is a variable that represents the identification result of the previous uplink reception position (step ST1). ).

First, when the RN is A1 to A2 (Yes in Step ST2), the position specifying unit 50 initializes Th1 to the default value Vdf (Step ST3) and stores the RN as RA (Step SR1). ) And RN are output (step SR2).
Although omitted in FIG. 10, the position specifying unit 50 has a predetermined time (for example, 1 second: from the previous determination to the current determination) in preparation for the case where there is no previous determination and the light is suddenly received at A10 this time. The time required for the vehicle C to pass through the uplink region is much shorter than 1 second even at a relatively low speed, so it can be determined that another vehicle is available if there is a space of 1 second or more. , Th1 is initialized to the default value Vdf.
In addition, when the RN is not A1 to A2 (No in Step ST2) and the RN is A3 to A9 (Yes in Step ST4), the position specifying unit 50 sets Th1 to the value of Vsum × α. Is updated (step ST5), RN is stored as RA (step SR1), and RN is output (step SR2).

Note that “update Th1 to the value of Vsum × α” in step ST5 means that the value of Vsum × α generated by the previous uplink optical UO is temporarily stored as the threshold Th1 for A10. To do.
On the other hand, when the determination result in step ST4 is No, RN is not in the range of A1 to A9, so RN may be in the range of A10. Therefore, the position specifying unit 50 performs the processing subsequent to the case where Step ST4 is No, the downstream end positions “L0 ″”, “L0 ′”, “L0 ′” of A10 based on the previous uplink reception position (= RA). ”” Is selected.

  That is, when the determination result in step ST4 is No and RA is A1 to A2 (Yes in step ST6), the position specifying unit 50 sets the RN to “unspecified” (step ST7). ), RN is stored as RA (step SR1), and RN is output (step SR2).

Further, when RA is not A1 to A2 (No in step ST6) and RA is A3 to A5 (Yes in step ST8), the position specifying unit 50 determines that the light reception level V1 of PD1 is equal to or higher than the threshold Th1. It is determined whether or not there is (step ST9).
The position identifying unit 50 replaces RN with “L0 ″” when V1 ≧ Th1 (step ST10), and replaces RN with “UL area over” when not V1 ≧ Th1 (step ST11). The RN is stored as RA (step SR1), and the RN is output (step SR2).

  Note that “UL area over” in this case means that the optical beacon 4 could not receive the uplink because the in-vehicle device 2 transmitted the uplink downstream from the final area A10.

Furthermore, when RA is not A3 to A5 (No in Step ST8) and RA is A6 to A8 (Yes in Step ST12), the position specifying unit 50 also determines that the light reception level V1 of PD1 is equal to or greater than the threshold Th1. It is determined whether or not there is (step ST13).
The position identifying unit 50 replaces RN with “L0 ′” when V1 ≧ Th1 (step ST14), and replaces RN with “UL area over” when V1 ≧ Th1 (step ST15). The RN is stored as RA (step SR1), and the RN is output (step SR2).

Similarly, when RA is not A6 to A8 (No in step ST12) and RA is A9 (Yes in step ST16), position specifying unit 50 also has light reception level V1 of PD1 equal to or greater than threshold Th1. Is determined (step ST17).
The position identifying unit 50 replaces RN with “L0 ′ ″” when V1 ≧ Th1 (step ST18), and replaces RN with “UL area over” when V1 ≧ Th1 is not satisfied (step ST18). ST19), the RN is stored as RA (step SR1), and the RN is output (step SR2).

Further, when RA is not A9 (No in Step ST16) and RA is “L0 ′ ″” (Yes in Step ST20), the position specifying unit 50 also has the light receiving level V1 of PD1 equal to or higher than the threshold Th1. Is determined (step ST21).
The position identifying unit 50 replaces RN with “L0 ′ ″” when V1 ≧ Th1 (step ST22), and replaces RN with “UL area over” when V1 ≧ Th1 is not satisfied (step ST22). ST23), the RN is stored as RA (step SR1), and the RN is output (step SR2).

When the RA is not “L0 ′ ″” (No in Step ST20) and the RA is “L0 ′” (Yes in Step ST24), the position specifying unit 50 also sets the light reception level V1 of the PD1 to the threshold Th1. It is determined whether or not this is the case (step ST25).
The position specifying unit 50 replaces RN with “L0 ′” when V1 ≧ Th1 (step ST26), and replaces RN with “UL area over” when V1 ≧ Th1 (step ST27). The RN is stored as RA (step SR1), and the RN is output (step SR2).

Similarly, when the RA is not “L0 ′” (No in step ST24) and the RA is “L0 ″” (Yes in step ST28), the position specifying unit 50 also sets the light reception level V1 of the PD1. It is determined whether or not the threshold value is Th1 or more (step ST29).
The position specifying unit 50 replaces RN with “L0 ″” when V1 ≧ Th1 (step ST30), and replaces RN with “UL area over” when not V1 ≧ Th1 (step ST31). The RN is stored as RA (step SR1), and the RN is output (step SR2).

If the RA is not “L0 ″” (No in step ST28), the position specifying unit 50 determines whether or not the RA, which is the previous specific result, is “UL area over” (step ST32). .
When RA is “UL area over”, the position specifying unit 50 replaces RN with “UL area over” (step ST33), and when RA is not “UL area over”, RN cannot be specified. (Step ST34), the RN is stored as RA (step SR1), and the RN is output (step SR2).

[Effect of light beacon]
As described above, according to the optical beacon 4 of the present embodiment, the light reception level V1 of the PD1 is equal to the total value Vsum of the light reception levels of all the PD _i at the boundary positions L2, L5, and L8 of the UA _i. In the embodiment, the positions “L0 ′ ″”, “L0 ′”, “L0 ″” that are equal to the value multiplied by α = 0.9) are set as the downstream end positions of the last area A10. The downstream end position of A10 can be set on the upstream side than usual.

Further, according to the optical beacon 4 of the present embodiment, the position specifying unit 50 multiplies the threshold Th1 for A10 by the predetermined coefficient α to the total value Vsum of the light reception levels of all PD _i for the previous uplink optical UO. Therefore, even _if the downstream end positions “L0 ′ ″”, “L0 ′”, and “L0 ″” of An are set to the upstream side of the normal as described above, the uplink optical UO It is possible to specify whether or not the uplink reception position is included in A10 regardless of the strength of.

  As described above, according to the optical beacon 4 of the present embodiment, even if the downstream end positions “L0 ′ ″”, “L0 ′”, “L0 ″” of A10 are set on the upstream side of the normal position, they are up. Since it is possible to accurately specify whether or not the link reception position is included in A10, it is possible to improve the positioning accuracy of the uplink reception position in UA1, which is the final divided region.

Moreover, according to the optical beacon 4 of this embodiment, the downstream end positions “L0 ′ ″” and “L0” of A10 corresponding to the plurality of boundary positions L2, L5, and L8 are stored in the storage device 48 of the beacon controller 7, respectively. '","L0''"are stored, and the position specifying unit 50 determines the plurality of downstream end positions“ L0 ”based on which of the plurality of A _j includes the previous uplink reception position. It is determined which of “″”, “L0 ′”, and “L0 ″” is to be adopted as the representative point of A10. For this reason, since an appropriate representative point of A10 can be selected based on the previous uplink reception position, even if the intensity of the uplink light UO changes for each vehicle C, the intensity of the uplink light UO is increased. The uplink reception position for A10 can be identified with appropriate corresponding accuracy.

12 and 13 are distribution diagrams when the light reception levels of PD1 to PD4 are actually measured with respect to the PD split type optical beacon 4 in which the beacon head 8 is attached at a predetermined position on the road R. FIG.
This distribution map shows the vehicle-mounted device 2 whose emission intensity is adjusted so that the reception intensity at the center of the lane and 4.5 m downstream from the optical beacon 4 is 1.0 μW / cm ² from the road surface. This is a measurement result when the vehicle is placed on the carriage so as to have a height of 0.0 m, and this carriage is slowly moved downstream along the road R.

Here, the value on the horizontal axis in FIGS. 12 and 13 is the value of the distance upstream from the head direct point H (see FIG. 7) as the origin. In FIG. 12, a characteristic curve CL with α = 0.8 is drawn, and in FIG. 13, a characteristic curve CL with α = 0.5 is drawn.
As shown in FIG. 12, when the predetermined coefficient α multiplied by Vsum is 0.8, the distance from the downstream end position of A9 to L0 ″ is 0.66 m, and the distance to L0 ′ is 0. It became 55m. On the other hand, as shown in FIG. 13, when the predetermined coefficient α multiplied by Vsum is 0.5, the distance from the downstream end position of A9 to L0 ″ is 0.73 m, up to L0 ′. The distance was 0.64m.

As can be seen from the actual measurement results, in order to shorten the area length of the final area A10, it is preferable to set the predetermined coefficient α multiplied by Vsum as large as possible.
However, a predetermined coefficient alpha, be set to a value greater than (0.9 in this embodiment) the maximum value m1 / m @ 2 of the ratio of the light receiving level of both PD _i of the neighboring UA _i, the previous uplink optical There is a possibility that the value of the threshold value (= Vsum × α) to be updated at the reception level of UO becomes too large, and it becomes impossible to detect the uplink optical UO at UA1. For this reason, it is preferable that m1 / m2 be the upper limit value of the predetermined coefficient α.

The predetermined coefficient α is preferably 0.5 or more. The reason is that when the predetermined coefficient α is less than 0.5, the characteristic curve CL becomes lower than that in the case of FIG. 13, and therefore the downstream end positions L0 ′ and L0 ″ of A10 corresponding to Vc and Vd are the normal positions. This is because the positioning accuracy at UA1 cannot be improved so much as L0.
If the predetermined coefficient α is set to 0.5, the downstream end position L0 of A10 is smaller than when the predetermined coefficient α is set larger (for example, α = 0.8 or 0.9). Since ', L0 ″, L0 ′ ″ can be measured more accurately, there is an advantage that the accurate downstream end position can be stored in the storage device 48.

However, if α = 0.5 is set, the Vsum × α curve coincides with the point where the light receiving levels of adjacent PD _i intersect, so that the downstream end positions L0 ′, L0 ″, L0 ′ ″ of A10 are mounted on the vehicle. While there is almost no change depending on the machine 2, the distance between L9 to L0 ′, L0 ″, L0 ′ ″, that is, the error of the uplink reception position becomes large.
On the other hand, when α = 0.9 (or 0.8) is set, the Vsum × α curve coincides with the point that the light reception level of the adjacent PD _i becomes a ratio of 9/1 (or 8/2). Therefore, the downstream end positions L0 ′, L0 ″, L0 ′ ″ of A10 slightly vary depending on the vehicle-mounted device 2 (varies compared to the case where α = 0.5), while L9 to L0 ′, L0. The distance of '', L0 ''', that is, the error of the uplink reception position becomes small.

[Other variations]
The embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of right of the present invention is not the above-described embodiment, but includes all modifications within the scope equivalent to the scope of claims.
For example, in the above embodiment, the uplink area UA is configured by the four divided areas UA1 to UA4. However, the number of the divided areas UA1 to UA4 (the number of photodiodes PD1 to PD4) constituting the uplink area UA is 2. It may be three, three or more.

Further, in the above-described embodiment, the subdivision number N for subdividing the divided areas adjacent to the other divided areas on both the upstream side and the downstream side (UA2 and UA3 when the total number of divided areas is 4) is “3”. However, N = 2 may be set or N ≧ 4 may be set.
Further, the downstream end that is the end of the path distance L may be a stop line 40, a traffic light installation position, or a vehicle detector position.

In addition, the distance information in the present embodiment is not limited to a format that directly stores a distance value to the predetermined position P0, and any format may be used as long as the information can uniquely determine the distance to the predetermined position P0. May be.
For example, one or a plurality of nodes may be set between the reference position Pr and a predetermined position P0 on the downstream side, and the distance information may be configured by a plurality of distance value groups corresponding to these nodes. That is, the distance information can be constituted by the distance from the reference position Pr to the nearest node, the distance between the nodes, and the distance from the node nearest to the predetermined position P0 to the predetermined position P0.

In this case, the in-vehicle computer 26 of the vehicle C that has received the distance information can recognize the distance to the predetermined position P0 by obtaining the total value of the distances.
Also, the information transmitted by the optical beacon 4 is not the value of the distance itself, but the absolute position (latitude / longitude or a coordinate value in a three-dimensional space with an arbitrary point in outer space as the origin). Etc.).

For example, the distance information is composed of the coordinates of the predetermined position P0 and the coordinates of the uplink reception positions L0 to L9 specified by the position specifying unit 50, and based on these coordinates (which may be an absolute position or a relative position). The distance recognition unit 30 of the in-vehicle device 2 may calculate the distance by itself.
In this case, if the coordinates of the predetermined position P0 are stored on the in-vehicle device 2 side, it is sufficient to transmit only the uplink reception positions L0 to L9 from the optical beacon 4 side.

1 Traffic control system (road-to-vehicle communication system)
2 In-vehicle device 4 Optical beacon 7 Beacon controller 8 Beacon head 9 Photodiode (light receiving part)
10 Light-emitting diode (emitter: transmitter)
45 processor 48 storage device (storage unit)
49 Communication Control Unit 50 Location Identification Unit A Communication Area C Vehicle R Road UA Uplink Area DA Downlink Area UA _i Uplink Area Divided Area PD Photodetector (Photodiode) Corresponding to _i Divided Area
A _j Subdivision area UO Uplink light DO Downlink light

Claims (7)

A plurality of light receiving portions (hereinafter referred to as “PD _i ”) respectively corresponding to a plurality of divided regions (hereinafter referred to as “UA _i ”, i being 1, 2,... M in order from the downstream side) arranged in the vehicle traveling direction. ,
Based on the light reception level generated in each PD _i when receiving uplink information from the vehicle, each UA _i is divided into a plurality of subdivision areas (hereinafter referred to as “A _j ”. _J is 1 in order from the upstream side. , 2... N), a position specifying unit that specifies the representative point as an uplink reception position in A _j ,
PD1 of the light-receiving level is equal to the value obtained by multiplying a predetermined coefficient to the sum of light receiving level of the total PD _i at the boundary position of the UA _i, provided with a storage unit for previously storing a downstream end position of the A _n ,
The position specifying unit, when the uplink reception position the previously identified is in the range from the boundary position up to A _n-1, the threshold value for A _n, for all PD _i upon receiving the last uplink information Update to a value obtained by multiplying the total value of the received light level by the predetermined coefficient,
If the current up-link receiver position is contained in A _n, the condition that the current uplink information received during the PD1 of the light-receiving level is equal to or greater than the updated threshold value, the stored said downstream end position the optical beacon, characterized by employing as the representative point of the a _n. When there are multiple boundary positions of UA _i ,
The storage unit stores a downstream end position of the A _n corresponding to a plurality of the boundary position,
Or the position specifying unit, based on whether the previous uplink receiving position is included in any of the plurality of A _j, employing any of a plurality of said downstream end position as the representative point A _n The optical beacon according to claim 1, wherein: Wherein the position specifying unit, at the boundary position of the UA _i upstream of the previous uplink receiving position, the downstream end position of the equal A _n a value obtained by multiplying the predetermined coefficient to the received light level of all the PD _i, the A The optical beacon according to claim 2 adopted as a representative point of _n .   The optical beacon according to any one of claims 1 to 3, wherein the predetermined coefficient is 0.5 or more. The said predetermined coefficient is a value below the maximum value of the ratio of the light reception level of both PD _i about adjacent UA _i set in order to define the boundary of A _{j. 5.} The optical beacon described in 1. A transmitter for transmitting downlink information;
A communication control unit including, in the downlink information transmitted after receiving the uplink information, distance information related to a distance from the uplink reception position specified by the position specifying unit to a predetermined position downstream thereof; The optical beacon according to any one of claims 1 to 5. Based on the light reception level generated in each PD _i when uplink information is received from the vehicle, any one of a plurality of A _{j obtained} by subdividing each UA _i in the vehicle traveling direction is specified as an uplink reception position. A method,
PD1 of the light-receiving level, the steps of storing the entire PD _i becomes equal to the value obtained by multiplying a predetermined coefficient to the sum of light receiving level of prestored device downstream end position of the A _n at the boundary position of the UA _i,
If the last identified uplink receiving position is in the range from the boundary position up to A _n-1, the threshold value for A _n, the sum of the light receiving levels of all PD _i upon receiving the last uplink information Updating to a value multiplied by the predetermined coefficient;
If the current up-link receiver position is contained in A _n, the condition that the current uplink information received during the PD1 of the light-receiving level is equal to or greater than the updated threshold value, the stored said downstream end position a method employed as the representative point of the a _n a,
A method for identifying an uplink reception position.

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