JP5195114B2 - Road-to-vehicle communication system and method and in-vehicle apparatus used therefor - Google Patents

Description

  The present invention relates to a road-to-vehicle communication system and method for performing bidirectional communication using an optical signal between an optical beacon installed on a roadside and an in-vehicle device mounted on a vehicle, and an in-vehicle device used therefor.

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 light as a communication medium, and is capable of two-way communication with an in-vehicle device. 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 in-vehicle device (see, for example, Patent Document 1).

The optical beacon includes a light emitter / receiver (beacon head) that performs bidirectional communication with an in-vehicle device, and the light emitter / receiver (LED) that irradiates downlink light toward the road side. ) And the like, and a light receiving element such as a photodiode (PD) that receives uplink light from the vehicle side.
The in-vehicle device is also equipped with a light projecting / receiving device (an in-vehicle head) having the light emitting element and the light receiving element in order to perform bidirectional communication with the beacon head using an optical signal.

For example, as shown in FIG. 3, in the beacon head 8 of the optical beacon 4, the communication area A is set on the upstream side in the vehicle traveling direction rather than immediately below the standard.
The communication area A according to this standard includes an uplink area UA that can receive uplink information (a range indicated by dotted line hatching) and a downlink area DA (a range indicated by solid line hatching) that transmits downlink information. Become. The lengths and positions of the areas UA and DA in the vehicle traveling direction are defined by the “near infrared interface standard” of an optical beacon (optical vehicle detector).

According to the above standard, the uplink area UA overlaps with the upstream part (the right part in FIG. 3) of the downlink area DA in the vehicle traveling direction, and the upstream ends of the downlink area DA and the uplink area UA are mutually connected. It is supposed to match.
In addition, the vehicle traveling direction length of the downlink area DA is the same as the length of the communication area A in the same direction.

In the communication area A of the road-vehicle communication system, the following communication is performed between the optical beacon 4 and the in-vehicle device 2.
That is, first, the beacon head 8 of the optical beacon 4 uses the first downlink information (downlink light DO) including the lane notification information (vehicle ID, no lane number) as the first information as the road downlink area DA. Are always transmitted at a predetermined transmission cycle.

Next, when the in-vehicle head 27 of the vehicle C enters the downlink area DA, the in-vehicle head 27 receives the first downlink information. With this as a trigger, the in-vehicle device 2 starts transmitting uplink information (uplink light UO) storing its own vehicle ID.
When the beacon head 8 receives the uplink information, the beacon head 8 switches the downlink and starts to transmit the second downlink information (downlink light DO) including the vehicle ID and the lane information to the in-vehicle head 27. The transmission of the second downlink information is repeated as much as possible within a predetermined time.

When confirming that the vehicle ID is stored in the second downlink information, the in-vehicle device 2 recognizes that the first downlink information is transmitted to itself, and the second Necessary information can be obtained from the downlink information.
The in-vehicle device 2 repeatedly transmits uplink information until it is confirmed that its own vehicle ID is stored in the second downlink information.
JP 2005-268925 A

In the beacon head 8 of the optical beacon 4 that is actually used in the conventional road-to-vehicle communication system, as shown in FIG. 14, for example, in order to increase the detection accuracy of the first downlink information by the in-vehicle device 2, The area of the downlink light DO (hereinafter referred to as “irradiation area”) IA that is actually irradiated to the vehicle in the vehicle traveling direction of the downlink area DA (same range as the communication area A) according to the interface standard In some cases, it extends to the upstream side of the dimension range.
Therefore, in this case, the irradiation area IA has a protruding area RA that extends upstream from the uplink area UA.

However, as described above, in the road-to-vehicle communication of the optical beacon 4, the uplink light UO is returned when the first downlink light DO is received by the in-vehicle head 27. Since the region IA extends to the upstream side, and there is the above-described protruding region RA on the upstream side of the uplink region UA, in the protruding region RA, the light emitting element of the in-vehicle head 27 generates useless uplink light UO. There is a problem of sending out.
That is, even when the uplink light UO is irradiated from the in-vehicle head 27 located in the protruding area RA, the beacon head 8 receives the uplink light UO because the in-vehicle head 27 has not yet reached the uplink area UA at this time. The uplink optical UO is wasted.

Thus, since the uplink light UO irradiated in the protrusion area RA does not reach the beacon head 8 because the transmission timing is too early, every time the in-vehicle head 27 passes through the optical beacon 4 having the protrusion area RA. As a result, useless uplink light UO irradiation occurs, and there is a problem in that the life of the light emitting element on the in-vehicle C side is shortened.
In particular, if the vehicle C stops with the in-vehicle head 27 in the protruding area RA due to traffic jams or the like, useless uplink light UO continues to be sent out many times at the time of the stop. Shortening the life becomes even more remarkable.

On the other hand, as a countermeasure for extending the lifetime of the light emitting element, the in-vehicle device 2 may execute a control process for limiting the number of times the uplink light UO is transmitted.
However, in this case, the limit on the number of times is exceeded by the useless uplink light UO transmitted based on the detection of the downlink light DO irradiated to the protruding area RA, and the in-vehicle head 27 has reached the uplink area UA. In some cases, the uplink optical UO cannot be transmitted, and eventually the uplink optical UO does not reach the beacon head 8 and communication cannot be established.

  In view of such a situation, the present invention prevents a useless uplink light from being transmitted from the vehicle side even when the irradiation area of the downlink light is spread to the upstream side than usual, so that the light emitting element on the vehicle side It is an object of the present invention to provide a road-to-vehicle communication system and method capable of suppressing a decrease in service life of the vehicle, and an in-vehicle device used therefor.

  An in-vehicle device according to the present invention (Claim 1) is an in-vehicle device of a vehicle that performs two-way communication using an optical signal with a beacon head of an optical beacon, and the downlink that the beacon head emits toward a road A light receiving element that receives the light, and a limiting member that restricts the downlink light irradiated to the upstream side portion of the actual downlink light irradiation area on the road from entering the light receiving element. It is characterized by having.

According to the vehicle-mounted device of the present invention, the limiting member limits the incidence of the downlink light that is irradiated on the upstream portion of the actual downlink light irradiation area on the road from entering the light receiving element. While the vehicle-side light receiving element passes through the upstream portion of the irradiation region, reception of downlink light by the light receiving element is hindered.
For this reason, when the upstream part of the irradiation area, which is the area of the downlink light that is actually irradiated to the road, is a protruding area that is wider than the uplink area, the downlink irradiated to the protruding area The light receiving element on the vehicle side does not receive the light, and unnecessary transmission of uplink light by the in-vehicle device is prevented. Accordingly, it is possible to suppress a decrease in the lifetime of the light emitting element due to the light emitting element emitting uplink light more than necessary.

In addition, according to the in-vehicle device of the present invention, transmission of uplink light in the protruding area is prevented, so in the case of an in-vehicle device having a control function for limiting the number of times of uplink light transmission, The uplink light can be transmitted appropriately within the range, and road-to-vehicle communication can be performed more reliably.
In the in-vehicle device of the present invention, the limiting member can be constituted by a shielding member disposed in front of the light receiving element, for example. Specifically, the shielding member has a structure that allows the incidence of the downlink light whose incident angle with respect to the light receiving element is equal to or larger than a predetermined value and shields the downlink light whose incident angle is less than the predetermined value. What has it can be employ | adopted (Claim 1 ).

The in-vehicle device according to the present invention may be configured such that a light emitting element that emits uplink light toward the beacon head and a start of reception of the downlink light that allows the shielding member to enter the light emitting element. and a communication control unit for transmitting a link light (claim 2).
In this case, at the start of reception of the downlink light that allows the shielding member to enter, the light receiving element on the vehicle side has already passed through the upstream portion of the irradiation region. For this reason, even if the upstream part of the irradiation region is a protruding region, useless uplink light is not transmitted in this protruding region.

On the other hand, in the in-vehicle device of the present invention, even if the vehicle traveling direction length of the irradiation region is different for each beacon head, the incident angle at the reception start time of the downlink light that allows the shielding member to be incident is It almost coincides with the limit angle (predetermined value) set for the shielding member.
For this reason, the light receiving element on the vehicle side at the time of starting the reception of the downlink light can be regarded as being located upstream of the position directly below the beacon head by a distance corresponding to the tangent corresponding to the limit angle set in the shielding member. As a result, the vehicle position of the vehicle at the start of downlink light reception can be identified almost accurately.

Therefore, in the in-vehicle device of the present invention, a position specifying unit for specifying the vehicle position of the vehicle based on a relative positional relationship with respect to the beacon head at the reception start time of the downlink light that allows the shielding member to enter. It is preferable to provide (Claim 1 ).
In this case, the position specifying unit can specify the own vehicle position using the downlink light autonomously and accurately on the vehicle side.

In the in-vehicle device of the present invention, the following two methods are conceivable as a method for specifying the reception start time of the downlink light.
(1) Based on the received light intensity of the downlink light that is allowed to be incident by the shielding member, the reception start time of the downlink light is specified.
(2) The time when the shielding member detects a digital signal included in the downlink light that is allowed to be incident is set as the reception start time of the downlink light.

In the in-vehicle device of the present invention, the limiting member may further include a second shielding member in addition to the shielding member.
In this case, the second shielding member shields the downlink light incident on the light receiving element from the downstream area of the actual downlink light irradiation area on the road. (Claim 3 ).

Further, if the second shielding member is formed in a shape covering the light receiving element so that the diffusely reflected light of the downlink light entering the passenger compartment of the vehicle does not enter the light receiving element ( 5 ), it is possible to prevent erroneous detection of downlink light accompanying detection of the irregularly reflected light by the light receiving element.
For this reason, it is possible to prevent the communication control unit from transmitting uplink light at an incorrect transmission timing due to diffusely reflected light generated in the passenger compartment.

Further, when the two types of shielding members are provided, the two types of the shielding members are based on the relative positional relationship with respect to the beacon head at the reception start time and the reception end time of the downlink light that allow the incidence. Te, it is preferable that the position specifying unit that specifies the vehicle position of the vehicle (claim 4).
In this case, the reliability of the relative positional relationship with respect to the beacon head at the reception start time of the downlink light can be determined using the relative positional relationship with respect to the beacon head at the reception end time, thereby identifying the vehicle position. Accuracy can be improved.

By the way, a vehicle traveling on an actual road does not necessarily travel parallel to the road surface of the road due to the uneven state of the road, the load of luggage or passengers, the acceleration / deceleration conditions, etc., and is about ± 5 degrees. Driving on the road while changing the slope in the pitch direction within the fluctuation range.
For this reason, if the change of the inclination of the pitch direction produced in the said shielding member mounted in the vehicle is not considered, an error will arise in the own vehicle position which a position specific | specification part specifies.
Therefore, it is preferable that the in-vehicle device of the present invention further includes an inclination detection unit that detects an inclination of the vehicle in the pitch direction, and in this case, the position specifying unit is configured so that the shielding member allows the down-coupling. the relative positional relationship with respect to the beacon head in reception start time point or receiving end of the link light, it is preferable to correct the inclination of said detected pitch direction (claim 6).

Road-vehicle communication system of the present invention (claim 7) is a road-to-vehicle communication system using the vehicle device of the present invention (claim 1-6), the same effects as the vehicle device (claim 1-6) Play.
The road-to-vehicle communication method of the present invention (Claim 8 ) is a road-to-vehicle communication method performed using the on-vehicle device of the present invention (Claim 1), and has the same effect as the on-vehicle device (Claim 1). There is an effect. Furthermore, the road-to-vehicle communication method of the present invention (Claim 9) is a road-to-vehicle communication method performed using the in-vehicle device of the present invention (Claim 4), and has the same effect as the in-vehicle device (Claim 4). There is an effect.

  As described above, according to the present invention, even when the irradiation area of the downlink light is spread upstream than normal, useless uplink light is not transmitted from the vehicle side. It is possible to suppress a decrease in the life of the light emitting element.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Overall system configuration]
FIG. 1 is a block diagram showing the overall configuration of the road-vehicle communication system of the present invention.
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 a large number of optical beacons (optical vehicle detectors) 4 installed at various locations on the road R. Two-way communication is performed with the in-vehicle device 2 by optical communication using 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 A plurality of (four in the illustrated example) beacon heads (projector / receiver) 8 connected to the sensor interface are provided.
Each beacon head 8 is configured by housing a light emitting element 10 made of a light emitting diode (LED) or the like and a light receiving element 11 made of a photodiode or the like in a housing 9 (see FIG. 3). Among these, the light emitting element 10 irradiates the downlink light DO made of near infrared rays toward the road R side, and the light receiving element 11 receives the uplink light UO made of near infrared rays from the in-vehicle device 2.

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 beacon heads 8 provided and a single beacon controller 7 serving as a control unit that collectively controls these 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 is a two-way communication with the central device 3 by the communication unit 6 and the in-vehicle device 2 by each projector / receiver 8. And a function as a communication control unit that controls 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 beacon head 8 is attached to an installation bar 13 installed horizontally on the road R side from the support column 12, and each lane R <b> 1 of the road R. It is arrange | positioned just above -R4.
The light emitting element 10 of each beacon head 8 emits near-infrared light toward the upstream side from directly below each lane R1 to R4, and thereby communication for performing road-to-vehicle communication with the in-vehicle device 2. Region A is set on the upstream side of the beacon head 8 (right side in FIG. 2).

FIG. 3 is a side view of the road R for showing the communication area A on the standard of the optical beacon 4.
As shown in FIG. 3, the communication region A on this standard, which will be described later in-vehicle apparatus 2 of the in-vehicle head (emitter and receiver) 2 7 is solid in the downlink region (Fig. 3 which can receive downlink information The area is provided with a hatched area DA, and the uplink area (the area provided with the broken line hatching in FIG. 3) UA from which the beacon head 8 of the optical beacon 4 can receive the uplink information.

In the “near-infrared interface standard” of the optical beacon (optical vehicle detector) 4, the uplink area UA overlaps with the upstream part (right side part of FIG. 3) of the downlink area DA in the vehicle traveling direction, The upstream end c of the downlink area DA and the uplink area UA coincide with each other.
Accordingly, the vehicle traveling direction length of the downlink area DA matches the same direction length of the entire communication area A according to the standard.

  In 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 the downlink area The distance from the downstream end a of the DA to the downstream end b of the uplink area UA is defined as 2.1 m, and the distance from the downstream end b of the uplink area UA to the upstream end c of the area UA is defined as 1.6 m. Has been. In this case, the total length of the communication area A in the vehicle traveling direction is 3.7 m.

However, the vehicle traveling direction length of each of the areas DA and UA is not limited to the above numerical values according to the standard.
Further, as indicated by a virtual line in FIG. 3, the beacon head 8 of the optical beacon 4 that is actually operated actually irradiates the road R, for example, in order to improve the detection accuracy of the downlink information. In some cases, the upstream end c ′ of the region (irradiation region) IA of the downlink light DO is located further upstream (right side in FIG. 3) than the upstream end c of the uplink region UA. In this case, the irradiation area IA of the actual downlink light DO has a protruding area RA that spreads upstream from the uplink area UA.

[Configuration of in-vehicle device and vehicle]
FIG. 4 is a schematic configuration diagram of the 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), the in-vehicle device 2 mounted on the vehicle body 21, and electronic control for integrated control of each part of the vehicle C. An apparatus (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 are provided.

Among these, ECU22 performs various control with respect to the vehicle C, such as drive control of the engine 23 based on a driver | operator's accelerator operation, and braking control based on a brake operation.
The in-vehicle device 2 includes an in-vehicle computer 26, an in-vehicle head (projector / receiver) 27 connected to a sensor interface of the computer 26, a display 28 and a speaker device 29 as a human interface for a driver of a passenger seat. Yes.

As in the case of the beacon head 8, the in-vehicle head 27 includes a light emitting element 18 made of a light emitting diode (LED) or the like and a light receiving element 19 made of a photodiode (PD) or the like.
The light emitting element 18 of the in-vehicle head 27 emits an uplink light UO (uplink information 35) made of near infrared rays, and the light receiving element 19 is a downlink light DO (down downlink) made of near infrared rays emitted by the beacon head 8. The link information 34, 36) 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. As a functional unit to be executed by this program, a communication control unit 30 for road-to-vehicle communication and specification of the vehicle position are provided. And a position specifying unit 31 for. The processing contents of these functional units 30 and 31 will be described later.

The in-vehicle device 2 includes an inclination detector (inclination detection unit) 33 that detects an inclination of the vehicle C in the pitch direction. The inclination detector 33 uses a gyro sensor, a G sensor, or an acceleration sensor. The degree of inclination of the vehicle C with respect to the horizontal plane in the pitch direction is constantly monitored.
The gyro sensor is a sensor that measures the angular velocity of an object, and an angle (tilt) can be obtained by integrating the detection signal. The G sensor is a sensor that measures the acceleration of an object, and gravitational acceleration is also added to the G sensor. On the other hand, an acceleration sensor is often synonymous with a G sensor. In this specification, an acceleration sensor that senses only an acceleration component having frequency characteristics and does not sense static acceleration (gravity acceleration) is called an acceleration sensor. .

FIG. 13 is an explanatory diagram illustrating the principle of detecting the inclination of the vehicle C that can be implemented by the sensor.
Among these, Fig.13 (a) has shown the detection principle of the inclination detector 33 which combined the triaxial G sensor and the triaxial acceleration sensor.
When the object is placed on the horizontal plane, the output of the 3G sensor is gz = G (G: gravitational acceleration), gx = gy = 0, but when the object is tilted from the horizontal plane, gz <G and gx ≠ 0 or gy ≠ 0. Therefore, the inclination of the object with respect to the horizontal plane can be calculated by using the ratio of gz to the other gx, gy among the three outputs of the 3G sensor.

However, when dynamic acceleration is generated in the object, such as when the vehicle C is accelerating, the dynamic acceleration is superimposed on gx, gy, and gz. Therefore, a triaxial acceleration sensor that does not detect gravitational acceleration (static acceleration) is used at the same time.
That is, if the output in each direction of the triaxial acceleration sensor is ax, ay, az, the output component is subtracted in each direction, and the ratio of (gx-ax), (gy-ay), (gz-az) The absolute value of the inclination of the object in the pitch direction with respect to the horizontal plane can be calculated by the following equation (1) using.

As for the direction of the inclination in the pitch direction, it can be determined whether the front of the vehicle C is upward or downward with respect to the horizontal plane by the sign of (gy-ay).
It should be noted that the absolute value of the inclination in the pitch direction can be simply obtained using only the value of (gz-az) using a single-axis G sensor and a single-axis acceleration sensor.

FIG. 13B shows the detection principle of the inclination detector 33 that combines a single-axis gyro sensor and a single-axis or three-axis acceleration sensor.
Assuming that the single-axis gyro sensor detects the angular velocity in the direction of the arrow in FIG. 13B with the horizontal plane as a base point, the inclination of the object in the pitch direction with respect to the horizontal plane can be detected by integrating the angular velocity. However, since errors accumulate in the integrated value over time, it is necessary to periodically perform zero point correction.

Therefore, the 1-axis, 2-axis or 3-axis G sensor is used simultaneously. That is, in this case, the output of the G sensor is monitored, and when the output is gz = G (and gx = gy = 0) and the value is stable, it is determined that the object is stable in the horizontal state, and the gyro What is necessary is just to correct | amend the zero point of the output of a sensor.
In addition, as another example of the inclination detector 33, it can also be comprised from the vehicle-mounted camera which images the road R, and the image processing apparatus which analyzes the imaged image data and calculates | requires the relative inclination with respect to the road R. .

[Road-to-vehicle communication: Processing contents of the communication control unit]
FIG. 5 shows a procedure for bidirectional road-to-vehicle communication performed between the beacon head 8 and the in-vehicle head 27. 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 of the optical beacon 4 sets first downlink information 34 including lane notification information as the first information before downlink switching from the beacon head 8 corresponding to each lane R1 to R4. Are constantly transmitted in the transmission cycle (F1 in FIG. 5). At this stage, the vehicle ID is not yet stored in the lane notification information.

Thereafter, when the in-vehicle head 27 of the vehicle C enters the irradiation area IA of the downlink light DO, the light receiving element 19 of the in-vehicle head 27 receives the first downlink information 34 including the lane notification information (no vehicle ID). .
At this time, the communication control unit 30 of the in-vehicle computer 26 recognizes that the vehicle C has reached an area where the vehicle C can communicate with the beacon head 8. Thereafter, the communication control unit 30 causes the light emitting element 18 of the in-vehicle head 27 to start transmitting the uplink information 35 (F2 in FIG. 5), and transmits the uplink information 35 to the beacon head 8 for a predetermined transmission cycle (up Link transmission cycle) (F3 in FIG. 5).

The communication control unit 30 of the in-vehicle computer 26 stores a specific vehicle ID for the vehicle C in the uplink information 35, transmits the uplink information 35, and has travel time information between beacons. This information is also included in the uplink information 35.
Further, the communication control unit 30 continues to transmit the uplink information 35 from the light emitting element 18 until it recognizes that the beacon controller 7 of the optical beacon 4 has switched the downlink.

On the other hand, when the light receiving element 11 of the beacon head 8 receives the uplink information 35 (F4 in FIG. 5), the beacon controller 7 switches the downlink and then has the vehicle ID information as the second information. The light emitting element 10 is started to transmit the second downlink information 36 including the notification information (F5 in FIG. 5). The transmission of the downlink information 36 is repeated as much as possible within a predetermined time (F6 in FIG. 5).
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 jam information, section travel time information, and event regulation information in addition to lane notification information including a vehicle ID. The second downlink information 36 may include signal information that is timing information for changing the lamp color of the traffic light downstream from the optical beacon 4.

As shown in FIG. 5, 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. 5), and transmits the uplink information 35 at this time. Stop.

[Injection restriction by restriction member]
In the in-vehicle device 2 of the present embodiment, in the irradiation area IA that is the area of the downlink light DO that is actually irradiated to the road R, the downlink light DO irradiated to the upstream side portion thereof is the in-vehicle head. 27 is provided with a restricting member 41 for restricting the light incident on the 27 light receiving elements 19.
FIG. 6 is a side view showing a configuration example of the restricting member 41.
As shown in FIG. 6, the limiting member 41 of the present embodiment includes a plate-shaped shielding member 42 disposed in front of the light receiving element 19 of the in-vehicle head 27.

This shielding member 42 is made of a plate material standing in front of the light receiving element 19 in a state of being inclined rearward, and an angle formed by the upper end edge of this shielding member 42 and the upstream end edge of the light receiving element 19 in the vehicle traveling direction. Accordingly, a limit angle α (α = 45 ° in the figure) for limiting the incidence of the downlink light DO is set.
Accordingly, among the downlink light DOs emitted from the beacon head 8 and having different incident angles θ, the downlink light DO whose incident angle θ with respect to the light receiving element 19 is less than the limit angle α is shielded by the shielding member 42 and incident. Only the downlink light DO whose angle θ is equal to or larger than the limit angle α can enter the light receiving element 19.

The side surface shape and other structures of the shielding member 42 are not particularly limited as long as the limit angle α can be fixedly set. For example, as shown in the lower part of FIG. Alternatively, it may be L-shaped in a side view or a circular arc in a side view.
Further, the limiting angle α of the shielding member 42 is an inclination angle θu of a line segment connecting the light emitting element 10 of the beacon head 8 and the upstream end c of the uplink area UA (see FIGS. 3 and 7: hereinafter, upstream of the uplink). It is set to a value that almost coincides with the inclination angle.

FIG. 7 is an operation explanatory view of the limiting member 41 formed of a single shielding member 42.
In the example shown in FIG. 7, an area surrounded by a solid line is an actual irradiation area IA of the downlink light DO, and this area IA is wider than the standard communication area A. A portion surrounded by a broken line is an uplink area UA.
Accordingly, in the irradiation area IA in this case, the upstream end portion is a protruding area RA that spreads further upstream than the uplink area UA.

Here, as shown in FIG. 7A, when the light receiving element 19 on the vehicle C side enters the protruding area RA of the irradiation area IA, the light receiving element 19 on the vehicle C side normally enters the protruding area RA. The irradiated downlink light DO is received.
However, in this embodiment, the downlink light DO whose incident angle θ with respect to the light receiving element 19 is less than the limit angle α is shielded by the shielding member 42, and the limit angle α is inclined upstream of the uplink. It is almost the same value as the angle θu. Accordingly, the light receiving element 19 on the vehicle C side does not receive the downlink light DO while passing through the protruding area RA.

Thereafter, as shown in FIG. 7B, when the light receiving element 19 on the vehicle C side starts to enter the uplink area UA, the incident angle θ of the downlink light DO with respect to the light receiving element 19 becomes the limit angle α (= θu). Thus, the light receiving element 19 starts to receive the downlink light DO.
For this reason, as shown in FIG. 7C, the light receiving element 19 on the vehicle C side uses the first downlink information 34 as the downlink light DO emitted downstream from the upstream end of the uplink area UA. As a trigger, road-to-vehicle communication with the beacon side is performed.

Thus, according to the in-vehicle device 2 of the present embodiment, the downlink light DO irradiated to the upstream side portion of the irradiation region IA of the actual downlink light DO is applied to the light receiving element 19 by the shielding member 42. Limit the incidence.
For this reason, even when the irradiation area IA includes the protruding area RA as shown in FIG. 7, the downlink light DO by the light receiving element 19 until the light receiving element 19 on the vehicle C side passes through the protruding area RA. Light reception is hindered.

Therefore, in the road-to-vehicle communication shown in FIG. 5, the communication control unit 30 of the in-vehicle computer 26 detects the downlink light DO irradiated to the protruding area RA and starts transmitting the uplink information 35 (F2 in FIG. 5). The transmission of the uplink information 35 is not started until the downlink light DO (the downlink light DO with the incident angle θ equal to or larger than the limit angle α) that the shielding member 42 allows the incident is detected (in FIG. 5). F2).
That is, the communication control unit 30 according to the present embodiment uplinks the light emitting element 18 in response to the start of reception of the downlink light DO that the shielding member 42 allows incidence in the road-to-vehicle communication performed with the beacon head 8. The emission of light UO is started.

Therefore, it is effectively prevented that the light emitting element 18 of the in-vehicle device 2 emits useless uplink light UO in the protruding area RA, and this causes the light emitting element 18 to emit the uplink light UO more than necessary. And the lifetime reduction of the light emitting element 18 is suppressed.
Further, for example, when the vehicle C stops while the light emitting element 18 is in the protruding area RA due to a traffic jam or the like, the light emitting element 18 continues to transmit useless uplink light UO many times. However, in this embodiment, it is possible to prevent such an unnecessary hit of the uplink optical UO.

On the other hand, the above-described useless use of the uplink optical UO can also be executed by setting a function for limiting the number of times the uplink optical UO is transmitted to the in-vehicle computer 26. However, in this limiting method, since the downlink light DO irradiated to the protruding area RA is detected, if the number of unnecessary uplink optical UO transmissions increases, the number of transmissions may be exceeded only by this number of transmissions.
In this case, since the uplink optical UO cannot be transmitted when the vehicle-mounted head 27 reaches the uplink area UA, the uplink optical UO does not reach the beacon head 8 and communication is not established. Become.

In this regard, according to the in-vehicle device 2 of the present embodiment, the transmission of the uplink optical UO in the overhang area RA is restricted, so that the uplink optical UO is appropriately transmitted within a preset limit number of times. Can do.
Therefore, it is possible to prevent the uplink light UO from reaching the beacon head 8 due to the restriction on the number of times the uplink optical UO is transmitted, and to perform road-to-vehicle communication more reliably.

[Processing content of the position identification part]
Next, processing contents of the position specifying unit 31 of the in-vehicle computer 26 will be described.
Here, the incident angle θ at the reception start time point (FIG. 7B) of the downlink light DO that allows the shielding member 42 to be incident is independent of the difference in the vehicle traveling direction length of the irradiation region IA. 42 should substantially coincide with the limit angle α set in advance.
Accordingly, as shown in FIG. 7B, the light receiving element 19 on the vehicle C side at the start of reception of the downlink light DO is the beacon head 8 by a distance L1 corresponding to the tangent corresponding to the limit angle α of the shielding member 42. It is located upstream from the position directly below.

That is, in FIG. 7B, when the distance from the position immediately below the beacon head 8 to the light receiving element 19 is L1, the installation height of the beacon head 8 is H0, and the installation height of the light receiving element 19 is H1, (2) is established.
L1 = (H0−H1) × tan (90−α) (2)
In the above equation (2), since the limit angle α and the installation heights H0 and H1 are both constant, the distance L1 based on the above equation (2) established at the reception start time of the downlink optical DO is also substantially constant. Value.

Therefore, the position specifying unit 31 of the present embodiment specifies the vehicle position of the vehicle C based on the relative positional relationship (formula (2)) with respect to the beacon head 8 at the reception start time of the downlink light DO.
That is, the position specifying unit 31 calculates a coordinate change amount (Δx1, Δy1) from immediately below the beacon head 8 to the reception start point of the downlink light DO from the distance L1 and its azimuth, and this change amount (Δx1) , Δy1) is added to the position coordinates (x0, y0) immediately below the beacon head 8, thereby calculating the vehicle position (x0 + Δx1, y0 + Δy1) of the vehicle C at the start of receiving the downlink light DO.

Since the own vehicle position (x0 + Δx1, y0 + Δy1) is more accurate than coordinates obtained by a GPS receiver, for example, if the GPS coordinates are corrected by the own vehicle position specified by the position specifying unit 31, the own vehicle position The accuracy of rating can be improved.
Further, when the vehicle-mounted device 2 acquires signal information related to the switching timing of the intersection signal, it is based on the signal information and the distance from the own vehicle position specified by the position specifying unit 31 to the downstream intersection position. Thus, it is possible to perform support control for safe driving that prompts the driver to brake the vehicle C or forcibly decelerates the vehicle C.

  The position coordinates (x0, y0) immediately below the beacon may be stored in advance in the storage device of the in-vehicle device 2, or included in the downlink information 34, 36 from the beacon side and stored in the in-vehicle device 2. Notification may be made.

[Identification method of reception start time]
In the processing of the communication control unit 30 and the position specifying unit 31, it is necessary to specify the reception start time of the downlink light DO that the shielding member 42 allows the incidence in the in-vehicle computer 26. The following two can be considered.
FIG. 8 is an example of a graph showing the relationship between the position of the light receiving element 19 in the vehicle traveling direction and the light receiving intensity. As shown in FIG. 8, the light receiving intensity of the light receiving element 19 rapidly increases at the reception start position of the downlink light DO, and then gradually decreases as it goes directly under the beacon after the maximum value continues for a while.

Therefore, the light receiving intensity of the light receiving element 19 is monitored in the in-vehicle computer 26, and the time when the light receiving intensity suddenly increases can be specified as the reception start time of the downlink light that allows the shielding member 42 to enter. .
However, since the in-vehicle computer 26 extracts a digital signal included in the downlink light DO that the shielding member 42 allows in the road-to-vehicle communication in the communication area A, the time when the in-vehicle computer 26 detects this digital signal. Then, the reception start time of the downlink optical DO may be set.

[Modification of restriction member]
FIG. 9 is a side view showing a modification of the limiting member 41.
As shown in FIG. 9, the limiting member 41 of this modified example is not limited to the first shielding member 42 that shields the downlink light DO whose incident angle θ with respect to the light receiving element 19 is less than a predetermined value. A second shielding member 43 that shields the downlink light DO having an incident angle θ exceeding another predetermined value is provided.

Of these two types of shielding members 42 and 43, the first shielding member 42 is made of a plate material standing in front of the light receiving element 19 in a substantially upright state, and the second shielding member 43 is the first shielding member 43. It is made of a substantially upright plate material disposed above the shielding member 42 with a predetermined gap.
The second shielding member 43 has a limit angle β for limiting the incidence of the downlink light DO (in the example shown in the figure) by an angle formed between the lower end edge of the second shielding member 43 and the downstream end edge of the light receiving element 19 in the vehicle traveling direction. β = 75 °) is set.

Accordingly, the incident angle θ of the downlink light DO incident from the gap between the two types of shielding members 42 and 43 with respect to the light receiving element 19 is limited to a range of α ≦ θ ≦ β. The downlink DO outside the range is shielded by the shielding members 42 and 43.
The side surface shape and other structures of the shielding members 42 and 43 are not particularly limited as long as the restriction range α ≦ θ ≦ β can be fixedly set. For example, as shown in the lower part of FIG. In addition, the second shielding member 43 may have a flat plate shape extending horizontally, and the shielding members 42 and 43 may have an arc shape in a side view. Moreover, in FIG. 9, in order to show the shielding function of the 1st and 2nd shielding members 42 and 43, both are drawn separately, but these shielding members 42 and 43 are substantially single members. It can also be formed integrally.

In the case of the second shielding member 43 shown in the lower part of FIG. 9, since the shape and arrangement covers the upper side of the light receiving element 19, the irregularly reflected light of the downlink light DO that has entered the passenger compartment of the vehicle C is The light does not enter the light receiving element 19.
For this reason, the erroneous detection of the downlink light DO accompanying the detection of the irregularly reflected light by the light receiving element 19 is prevented, and it is possible to prevent the communication control unit 30 from transmitting the uplink light UO at the wrong transmission timing due to the irregularly reflected light. Can be prevented.

FIG. 10 is an explanatory diagram of the operation of the limiting member 41 including two types of shielding members 42 and 43.
In the example shown in FIG. 10, an area surrounded by a solid line is an actual irradiation area IA of the downlink light DO, and this area IA has a wide range on both the upstream side and the downstream side of the communication area A on the standard. It has become. A portion surrounded by a broken line is a downlink area DA (the same range as the communication area A) according to the interface standard.
Accordingly, the irradiation area IA in this case has a protrusion area RA1 extending upstream from the standard downlink area DA and a protrusion area RA2 extending downstream from the standard downlink area DA.

In the limiting member 41 shown in FIG. 9, the range of the incident angle θ of the downlink light DO emitted from the beacon head 8 with respect to the light receiving element 19 is in the range of α ≦ θ ≦ β by the two types of shielding members 42 and 43. It is narrowed down to.
Therefore, while the light receiving element 19 on the vehicle C side passes through the upstream protruding area RA1 and the downstream protruding area RA2, the incidence of the downlink light DO is limited, and only while passing through the downlink area DA. Inclusion of downlink light DO is allowed.
For this reason, as shown in FIG. 10, even when the upstream areas and the downstream areas include the protruding areas RA1 and RA2, respectively, only within the range of the vehicle traveling direction excluding these areas RA1 and RA2. Road-to-vehicle communication can be performed.

[Processing contents of position specifying unit when there are two types of shielding members]
As described above, when the two types of shielding members 42 and 43 are provided, the incident angle θ at the reception start time point of the downlink light DO (FIG. 10A) is preset in the first shielding member 42. It almost coincides with the limit angle α. Further, the incident angle θ at the time when the reception of the downlink light DO ends (FIG. 10B) substantially matches the limit angle β set in advance for the second shielding member 43.

Then, the light receiving element 19 on the vehicle C side at the reception start time of the downlink light DO (FIG. 10A) is the beacon head 8 by a distance L1 corresponding to the tangent corresponding to the limit angle α of the first shielding member 42. This distance L1 can be calculated by the following equation (2).
L1 = (H0−H1) × tan (90−α) (2)

The light receiving element 19 on the vehicle C side at the end of reception of the downlink light DO (FIG. 10B) has a beacon head 8 of a distance L2 corresponding to the tangent corresponding to the limit angle β of the second shielding member 43. This distance L2 can be calculated by the following equation (3).
L2 = (H0−H1) × tan (90−β) (3)

On the other hand, when the reception start time of the downlink light DO is t1, the reception end time is t2, the time difference between them is Δt (= t2−t1), and the vehicle speed during this time is V, the reception start time of the downlink light DO ( The travel distance ΔL of the vehicle C from the time point (a) in FIG. 10 to the time point when the reception ends (the line (b) in FIG. 10) can be expressed by the following equation (4).
L = V × Δt (4)
And this travel distance L should theoretically agree with the distance difference ΔL (= L1−L2) obtained by the equations (2) and (3).

However, for example, when there is a detection delay at the reception start time t1 of the downlink optical DO, the relationship of the equation (2) is not established, and therefore the distance L1 is calculated based on the equation (2). Become inappropriate.
Therefore, the position specifying unit 31 of the present embodiment determines the reliability of the reception start time t1 based on whether or not the distance difference ΔL (= L1−L2) is substantially the same as the travel distance L in Expression (4). Specifically, the position specifying unit 31 first obtains the travel distance L obtained by the expression (4) and the expressions (2) and (3) before specifying the vehicle position based on the expression (2). It is determined whether or not the difference from the obtained distance difference ΔL (= L1−L2) is within a predetermined threshold.

When the determination result is within the threshold value, it can be considered that the reception start time t1 of the downlink optical DO is properly detected, and therefore the position specifying unit 31 is a beacon head at the reception start time t1 of the downlink optical DO. Based on the relative positional relationship with respect to 8 (equation (2)), the vehicle position (x0 + Δx1, y0 + Δy1) of the vehicle C at the reception start time t1 is calculated.
As described above, the position specifying unit 31 of the present embodiment determines the reliability of the reception start time t1 using the distance L2 obtained from the relative positional relationship (formula (3)) with respect to the beacon head 8 at the reception end time t2. In addition, since the vehicle position is specified using the relative positional relationship (formula (2)) with respect to the beacon head 8 at the reception start time t1, the specification of the vehicle position using the incorrect reception start time t1 is performed. This can be prevented, and the identification accuracy of the vehicle position can be improved in this respect.

[Identification method when reception ends]
In the processing of the position specifying unit 31, not only the reception start time t1 of the downlink light DO whose incident angle θ is reduced by the two types of shielding members 42 and 43 but also the reception end time t2 of the downlink light DO is mounted on the vehicle. Although it is necessary to specify in the computer 26, the reception end time t2 can be specified by the light receiving intensity of the light receiving element 19.
FIG. 11 is an example of a graph showing the relationship between the vehicle traveling direction position of the light receiving element 19 and the light receiving intensity when the limiting member 41 is configured by two types of shielding members 42 and 43.

As shown in FIG. 11, the light receiving intensity of the light receiving element 19 rapidly increases at the reception start position of the downlink light DO, and then rapidly decreases after reaching the maximum value and immediately below the beacon. Returns to 0.
Therefore, in the in-vehicle computer 26, the time point at which the received light intensity suddenly increases is specified as the reception start time t1 of the downlink light DO that allows each of the shielding members 42 and 43 to be incident, and the received light intensity returns to zero. Can be identified as the reception end time t2 of the downlink optical DO.

[Correction processing by pitch direction inclination]
By the way, the vehicle C traveling on the actual road R does not necessarily travel parallel to the traveling surface of the road R due to the uneven state of the road, the load of the luggage or the passenger, the acceleration / deceleration situation, etc. The vehicle travels on the road R while dynamically changing the inclination in the pitch direction within a fluctuation range of ± 5 degrees.
For this reason, if the change of the inclination of the pitch direction which arises in the shielding member 42 mounted in the vehicle C is not taken into consideration, an error also occurs in the own vehicle position specified by the position specifying unit 31.

FIG. 12 is an operation explanatory view showing a method for specifying the vehicle position in consideration of the inclination in the pitch direction.
As shown in FIG. 12, it is assumed that the vehicle C here has an inclination φ in the pitch direction of the forward descending when entering the uplink area UA.
In this case, the first shielding member 42 mounted on the vehicle C is inclined forwardly downward by the inclination φ in the pitch direction as compared with the case where the vehicle C is traveling in the horizontal direction. The incident angle θ at the reception start time of the downlink light DO that allows the one shielding member 42 to be incident is inclined with respect to the pitch direction inclination φ (previous rise) with respect to the limit angle α set in advance on the first shielding member 42. In the case of, it will be added by the negative number).

Therefore, as shown in FIG. 12, the light receiving element 19 on the vehicle C side at the start of receiving the downlink light DO is a distance corresponding to a tangent corresponding to an angle obtained by adding the inclination φ to the limit angle α of the first shielding member 42. Only L3 is located upstream of the position directly below the beacon head 8.
That is, in FIG. 12, when the distance from the position immediately below the beacon head 8 to the light receiving element 19 is L3, the installation height of the beacon head 8 is H0, and the installation height of the light receiving element 19 is H1, the following equation (5) Is established.
L3 = (H0−H1) × tan (90−α−φ) (5)

Therefore, the position specifying unit 31 of the present embodiment always obtains the inclination φ in the pitch direction from the inclination detector 33, and substitutes the inclination φ at the start of receiving the downlink light DO into the above equation (5). By doing this, the distance L3 with respect to the beacon head 8 at the reception start time of the downlink light DO is obtained, and the vehicle position of the vehicle C is specified based on the distance L3.
As described above, the position specifying unit 31 of the present embodiment determines the relative positional relationship with respect to the beacon head 8 at the reception start time of the downlink light DO that the first shielding member 42 allows the incidence, and the pitch at the reception start time point. Since the correction is performed based on the direction inclination φ, the distance L3 can be accurately grasped, and the vehicle position specifying accuracy can be improved.

Note that the position specifying unit 31 of the present embodiment is not illustrated, but is relative to the beacon head 8 at the time when the reception of the downlink light DO permitted by the second shielding member 43 is completed in the same manner as described above. The positional relationship can also be corrected by the inclination φ in the pitch direction at the end of the reception.
That is, in the position specifying unit 31 of the present embodiment, the inclination φ at the time when the reception of the downlink light DO is finished is substituted into the following equation (6), and the beacon head 8 at the time when the reception of the downlink light DO is finished. By obtaining the distance L4, the relative positional relationship with respect to the beacon head 8 (distance L2 in the equation (3)) at the end of reception of the downlink light DO can be corrected.
L4 = (H0−H1) × tan (90−β−φ) (6)

[Other variations]
The embodiments disclosed thus far are all illustrative and not restrictive. The scope of the present invention is indicated by the scope of claims for patent, and all modifications within the scope equivalent to the structure of the claims for patent are included in the present invention.

For example, in the above embodiment, the limiting member 41 is configured by the plate-shaped shielding members 42 and 43, but the limiting member 41 is a louver film having a property of transmitting only light having an incident angle within a predetermined range. It can also be configured. In the case of this louver film, the effect of restricting incidence is exhibited only by being attached to the surface of the light receiving element 19, so that there is an advantage that the restricting member 41 can be easily manufactured and installed.
In the above embodiment, the functional units 30 and 31 of the in-vehicle computer 26 can be incorporated into the electronic control unit (ECU) 22 of the vehicle C.

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 of the road for showing the communication area on the standard of an optical beacon. 1 is a schematic configuration diagram of an in-vehicle device and a vehicle on which the in-vehicle device is mounted. It is a conceptual diagram which shows the procedure and data content of road-to-vehicle communication. It is a side view which shows the structural example of a limiting member. It is an action explanatory view of a restricting member, (a) at the time of rushing into an overhang area, (b) at the time of rushing into an uplink area, and (c) showing passing through the uplink area, respectively. It is a graph which shows the relationship between the vehicle advancing direction position of a light receiving element, and received light intensity. It is a side view which shows the modification of a limiting member. It is operation | movement explanatory drawing of the limitation member which consists of two types of shielding members, (a) has shown at the time of rushing into a specification area | region, (b) has each shown at the time of exiting from a specification area | region. It is a graph which shows the relationship between the vehicle advancing direction position of a light receiving element, and received light intensity. It is an operation explanatory view showing the identification method of the own vehicle position in consideration of the inclination in the pitch direction. It is explanatory drawing which shows the detection principle of the inclination of a vehicle. It is a side view of the road for showing the problem of a protrusion area | region.

Explanation of symbols

4 Optical beacon 7 Beacon controller 8 Beacon head 10 Light emitting element (beacon side)
11 Light receiving element (beacon side)
18 Light emitting element (vehicle side)
19 Light receiving element (vehicle side)
30 Communication Control Unit 31 Position Identification Unit 33 Inclination Detector (Inclination Detection Unit)
34 1st downlink information 35 Uplink information 36 2nd downlink information 41 Restriction member 42 1st shielding member 43 2nd shielding member
A Communication area
C vehicle R road IA irradiation area UA uplink area DA downlink area RA protrusion area UO uplink light DO downlink light

Claims (9)

An in-vehicle device of a vehicle that performs bidirectional communication with an optical signal between a beacon head of an optical beacon,
A light receiving element that receives downlink light emitted from the beacon head toward the road;
A limiting member that limits the incidence of the downlink light that is irradiated on the upstream side portion of the actual irradiation area of the downlink light on the road to the light receiving element ;
The limiting member comprises a shielding member disposed in front of the light receiving element,
The shielding member has a structure that allows the incidence of the downlink light whose incident angle with respect to the light receiving element is equal to or larger than a predetermined value, and shields the downlink light whose incident angle is less than a predetermined value,
The apparatus further comprises a position specifying unit that specifies a position of the vehicle of the vehicle based on a relative positional relationship with respect to the beacon head at a reception start time of the downlink light that is allowed to be incident on the shielding member. In-vehicle device. A light emitting element for irradiating uplink light toward the beacon head;
The in-vehicle device according to claim 1 , further comprising: a communication control unit that causes the light emitting element to irradiate the uplink light when triggered by reception of the downlink light that allows the shielding member to be incident. The limiting member further includes a second shielding member in addition to the shielding member,
The second shielding member, in claim 1, wherein the downlink beam irradiated to the downstream portion in the beam spot of the actual said downlink beam with respect to the road to shield from entering the light receiving element The in-vehicle device described. An in-vehicle device of a vehicle that performs bidirectional communication with an optical signal between a beacon head of an optical beacon,
A light receiving element that receives downlink light emitted from the beacon head toward the road;
A limiting member that limits the incidence of the downlink light that is irradiated on the upstream side portion of the actual irradiation area of the downlink light on the road to the light receiving element;
The limiting member comprises a shielding member disposed in front of the light receiving element,
The shielding member has a structure that allows the incidence of the downlink light whose incident angle with respect to the light receiving element is equal to or larger than a predetermined value, and shields the downlink light whose incident angle is less than a predetermined value,
The limiting member further includes a second shielding member in addition to the shielding member,
The second shielding member shields the downlink light incident on the downstream portion of the actual downlink light irradiation area on the road from entering the light receiving element,
A position specifying unit for specifying the vehicle position of the vehicle based on a relative positional relationship with respect to the beacon head at a reception start time and a reception end time of the downlink light that allows both types of the shielding members to be incident; A vehicle-mounted device further comprising: The second shielding member, said as the downlink beam irregularly reflected light passenger has entered the interior of the vehicle is not incident to the light receiving element, according to claim 3 are formed in a shape covering the upper side of the light receiving element or 4. The in-vehicle device according to 4 . An inclination detector that detects an inclination of the vehicle in the pitch direction;
The position specifying unit is configured to determine a relative positional relationship with respect to the beacon head at a reception start time or a reception end time of the downlink light at which the shielding member is allowed to be incident, or both, based on the detected inclination in the pitch direction. The in-vehicle device according to claim 1 or 4 to correct. A road-vehicle communication system comprising an in-vehicle device of a vehicle traveling on a road and an optical beacon having a beacon head, and performing bidirectional communication by an optical signal between the in-vehicle device and the beacon head,
The road-to-vehicle communication system, wherein the vehicle-mounted device is the vehicle-mounted device according to any one of claims 1 to 6 . A road-to-vehicle communication method for performing bidirectional communication by an optical signal composed of downlink light and uplink light between an in-vehicle device of a vehicle traveling on a road and a beacon head of an optical beacon,
The incidence of the are the downlink optical radiation on the upstream portion in the beam spot of the actual said downlink beam with respect to the road is shielded by the shielding member below by using the downlink light clear this shielding said bidirectional communication line Utotomoni, based on the relative positional relationship with respect to the beacon head in reception start time point of the down ring light, road-to-vehicle communication method and identifies the vehicle position of the vehicle.
Shielding member: disposed in front of the light receiving element that receives the downlink light, allows the incidence of the downlink light whose incident angle with respect to the light receiving element is equal to or larger than a predetermined value, and has the incident angle smaller than the predetermined value. Shielding member having structure for shielding link light A road-to-vehicle communication method for performing bidirectional communication by an optical signal composed of downlink light and uplink light between an in-vehicle device of a vehicle traveling on a road and a beacon head of an optical beacon,
Of the actual irradiation area of the downlink light on the road, the incidence of the downlink light irradiated on the upstream part and the downstream part is shielded by the following shielding member and the following second shielding member, respectively. The two-way communication is performed using the downlink light that has cleared the shielding, and the vehicle itself is based on the relative positional relationship with the beacon head at the reception start time and the reception end time of the downlink light. A road-to-vehicle communication method characterized by specifying a position.
Shielding member: disposed in front of the light receiving element that receives the downlink light, allows the incidence of the downlink light whose incident angle with respect to the light receiving element is equal to or larger than a predetermined value, and has the incident angle smaller than the predetermined value. Shielding member having structure for shielding link light
Second shielding member: a shielding member that shields the downlink light irradiated to the downstream portion from entering the light receiving element.

Images