JP4142802B2 - Vehicle navigation device - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a vehicle navigation device that receives the latest traffic information transmitted from an external communication device and calculates a route in consideration of past traffic information.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in order to support traveling on a vehicle in an unguided land, a vehicle navigation device that displays the current location of the vehicle together with a road map around it has been used. In such a vehicle navigation device, a driver or a passenger (hereinafter collectively referred to as a “driver”) can set a destination, and a computer automatically sets the shortest time path between the current location and the set destination. There are some which can be obtained automatically (see, for example, Japanese Patent Laid-Open No. 5-53504).
[0003]
In the vehicular navigation device to which this route calculation function is added, when a destination is set, road map data composed of links connecting road intersections, etc. are read, and the current location and destination are set starting from the current location or destination. Search the link tree for the area that includes the ground. In this case, the travel time (link cost) data of each link included in the road map data is sequentially added, and the route with the longer travel time is deleted from the plurality of routes reaching the same link. The tree of the route that reaches each link at the minimum link cost is obtained, and the route between the current location and the destination along this tree is set as the shortest time route.
[0004]
By the way, the travel time data actually changes depending on traffic conditions such as traffic restrictions due to road construction and the presence or absence of an accident. It is impossible to prepare travel time data in consideration of such changing traffic conditions on the vehicle side in advance. Therefore, in recent years, a system for providing a vehicle with traffic information reflecting the current traffic situation from an external communication device is being put into practical use. For example, specific examples of currently implemented systems include road traffic information communication systems (VICS: Vehicle Information and Communication System) that transmit traffic information to vehicles using radio wave beacons, optical beacons or FM multiplex broadcasting, and There is a traffic information service (ATIS: Advanced Traffic Information Service) that transmits traffic information to vehicles using an automobile / cell phone network.
[0005]
There are various methods for obtaining traffic information by the control center that transmits the traffic information to the vehicle. For example, the traffic flow is detected by a vehicle detector or a TV camera installed in various places on the road. There is a method of collecting and collecting traffic information and travel time information at the center.
However, the traffic volume on each road varies greatly depending on the time of collection. FIG. 5 is a graph in which the travel time of the link is estimated from the data of the vehicle speed obtained by the vehicle detector. The horizontal axis in the figure is divided every 2 hours from midnight, and the vertical axis represents the link travel time in seconds. This graph shows that the link travel time fluctuates drastically.
[0006]
If such fluctuations are taken into the link travel time as they are, the traffic information provided to the vehicle side cannot be said to accurately represent the travel time passing through the link, and this accuracy is reduced. The shortest time route is calculated based on the traffic information.
[0007]
[Problems to be solved by the invention]
The inventor of the present invention paid attention to how the link travel time varies in the graph as shown in FIG. There are two types of fluctuations, and one is a medium-term fluctuation in which travel time fluctuates, for example, in an early morning time zone and a time zone around 10 am. The other is a smaller variation that occurs regardless of the time of day.
[0008]
The latter minute fluctuation occurs because the vehicle slows down or stops while waiting for a signal, or the vehicle flow improves and speeds up. The cause of this is the signal control parameter of the traffic light system, specifically In particular, it is considered to be due to the signal switching period or split (red / blue time ratio).
The traffic light system detects changes in traffic conditions such as traffic jams with vehicle detectors and TV cameras on the road, transmits the detection results to the center, determines signal control parameters at the center, and transmits them to each traffic light This method is adopted. It is a well-known fact that the running state of the vehicle between signals varies depending on whether the response for determining the signal control parameter is slow or fast.
[0009]
That is, when the response is slow, the vehicle repeats stop and go, and the slight fluctuation of the link travel time is not eliminated. In this case, the past link travel time information for the same link acquired by the vehicle side from the control center varies, and it is necessary to suppress fluctuations by taking an average.
On the other hand, when the response is fast, the vehicle flows well on average, and the past link travel time for the same link acquired by the vehicle side from the control center does not vary much. In this case, if the average of the data far back in the past is averaged, the adverse effect of overlooking the medium-term time fluctuation of the link travel time itself is great.
[0010]
Furthermore, due to the hardware and software characteristics of the traffic information communication system, it takes some time to collect and aggregate traffic information and travel time information, and the traffic information transmitted to the vehicle is updated every few minutes to several tens of minutes. Is called. As a result, the traffic information provided to the vehicle side has a certain time difference and is not real time information in a strict sense.
[0011]
From the above viewpoint, the vehicle navigation apparatus is required to be able to acquire a link travel time reflecting the current traffic situation with high accuracy and calculate the shortest time route.
Therefore, the present invention provides a vehicle navigation device that can calculate the shortest time path reflecting the actual traffic situation with high accuracy and indicate it to the driver when acquiring traffic information from an external communication device. With the goal.
[0012]
[Means for Solving the Problems and Effects of the Invention]
(1) A vehicle navigation apparatus according to claim 1 for achieving the object, road map data storage means for storing road map data associated with a link which is a constituent unit of a route network, and external communication Receiving means for receiving traffic information including link travel time transmitted from the device, and when the traffic information is received by the receiving means, the link travel time of each link is acquired and held based on the traffic information Link travel time acquisition means, and link travel time correction means for smoothing the link travel time of the same link acquired and held by the link travel time acquisition means to obtain a smoothed link travel time. The smoothed link travel time obtained by the link travel time correction means and the road map data stored in the road map data storage means. Route calculating means for calculating a route based on the vehicle, and the link travel time correcting means performs time series weighting of the smoothing process based on a control response characteristic of a traffic control system in a region where the vehicle travels It is.
[0013]
Here, the control response characteristic of the traffic control system is a response time delay that occurs when a traffic flow control system such as a traffic light system performs traffic flow control, and the vehicle after the control center acquires the latest travel time data. This is the sum of delays in the time it takes to tell
For example, in the case of a traffic light system, (a) a flow of traffic is detected by a vehicle sensor on a road and transmitted to a control center. (b) The control center optimizes and controls the signal control cycle based on the traffic flow captured by the vehicle detector and the TV camera. (c) Then, signal control data is transmitted to each traffic light.
[0014]
In the case of a road traffic information communication system, (d) if travel time data of the link is detected by a vehicle detector or a television camera, (e) the control center collects and aggregates data of each link. (f) Then, travel time data is transmitted to each vehicle through a predetermined communication medium.
The total time taken from (a) to (c) and the time taken from (d) to (f) is the “control response characteristic of the traffic control system”.
[0015]
According to the configuration of the present invention, when the link travel time of the same link acquired and held in the past is smoothed, the smoothing is performed based on the control response characteristics of the traffic control system in the area where the vehicle travels. Perform time-series weighting of processing.
That is, when the response of the control response characteristic of the traffic control system is fast, the control of the traffic control system is performed quickly. Therefore, the time series weighting coefficient may be made smaller in the past or ignored. When the response of the control response characteristic of the traffic control system is slow, since the control of the traffic control system is slow, the past time series weighting coefficient is evaluated relatively heavily.
[0016]
By such control, it is possible to obtain a link travel time reflecting the current traffic situation with high accuracy and to calculate a shortest time route with high reliability.
(2) The control response characteristic of the traffic control system may be determined according to a current position of the vehicle detected by the navigation device (Claim 2), and the control response characteristic of the traffic control system is determined by the receiving means. It may be determined on the basis of traffic information received in (Claim 3).
[0017]
The former is because what kind of traffic light system is applied to the vehicle is specified by the current position of the vehicle, that is, the link on which the vehicle is traveling, and the control response characteristic can be known.
The latter is effective when the traffic information received by the receiving means includes data of control response characteristics of the traffic control system. It is also conceivable that the control response characteristic can be grasped to some extent by the road traffic information communication system. This is because, for example, there are a plurality of information providers, and the control response characteristics differ depending on differences in management purposes, national information, wide area information, or local information.
[0018]
(3) The control response characteristic of the traffic control system may be corrected according to the type and width of the road around the current position of the vehicle (Claim 4), and the control response characteristic of the traffic control system is corrected according to the current time. (Claim 5).
The former is the link travel time and congestion level collected by the control system according to the type of road (highway automobile national road, automobile exclusive road, other national roads, prefectural roads, city roads of government-designated cities, other living roads, etc.) This is because the control response characteristics of the information may differ. This is because the degree of maintenance of the traffic light system, the vehicle detector, the TV camera, the information transmission characteristic, and the like differ depending on the type of road and the road width, and the control response characteristic also differs.
[0019]
The latter is because there is a possibility that a correlation between the actual traffic situation at each time and the control response characteristic of the control system may be obtained. For example, the characteristics of the traffic light system may be switched depending on time zones such as morning, noon, and night. Therefore, it is conceivable to change the contents of the time series weighting of the smoothing process depending on the time.
(4) It is preferable to acquire the control response characteristic of the traffic control system along the route to the destination by transmitting the destination from the vehicle to the control center.
When the destination is transmitted from the vehicle to the control center, the control center may return the travel time data of the link included in the road map from the current location to the destination to the vehicle. In this case, if the control response characteristic of the traffic control system of each link is acquired and saved, the exact travel time of the link included in the road map to the destination is subjected to time series weighting smoothing processing, Since it can be obtained, an optimal route can be calculated.
[0020]
(5) The degree of time-series weighting performed by the link travel time correcting means may be set by the user (claim 7).
For example, when there is an actual local accident and there is a rapid fluctuation in the link travel time, if the past smoothing coefficient is large, this fluctuation may not be reflected. In this case, setting the current link travel time by giving an instruction through the man machine from the driver can make the situation closer to the actual situation. In such a case, if the content of the time-series weighted smoothing process can be changed by an instruction from the user, it is possible to cope with such a sudden situation as described above.
[0021]
(6) In the vehicle navigation device according to any one of claims 1 to 7, the same effect can be obtained even when the traveling speed is used instead of the travel time. Since travel time and travel speed are in the relationship of (travel time) × (travel speed) = travel distance, if the link distance is fixed, if one is found, the other is automatically found. . Therefore, even if such a replacement is made, the content of the invention does not change.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic diagram of a system for providing traffic information to the vehicle navigation apparatus of the present invention. In this traffic information providing system, road beacons B1, B2,... Installed on each road in the traffic information providing area and communication lines (public lines or dedicated lines) L are connected to the road beacons B1, B2,. And a control center C that transmits data via the network.
[0023]
The road beacons B1, B2,... May be either radio wave beacons or optical beacons.
In the control center C, a relatively coarse first having links a, b,..., F,... (Hereinafter referred to as “traffic information links”) connecting major intersections in the traffic information provision area. Link traffic information corresponding to the route network is stored. This link traffic information is the latest traffic information that changes from moment to moment, and includes travel time information that is the time required for the vehicle to travel on the road corresponding to the link. The travel time information is collected by, for example, a vehicle detector, a TV camera, a helicopter that travels over the sky, or a traffic information collection vehicle that actually travels on the road.
[0024]
This link traffic information is given to the road beacons B1, B2,... The road beacons B1, B2,... Transmit the given link traffic information to the vehicle.
FIG. 2 is a block diagram showing an electrical configuration of the vehicle navigation apparatus. The vehicle navigation apparatus 1 includes an external antenna 2 for receiving traffic information from the outside, and a DVD-ROM, DVD-RAM, CD-ROM, MD, hard disk, floppy disk, MO for storing road map data. , DAT, and the like, a display device 3 composed of a CRT tube, a liquid crystal display, and the like, and a wired or wireless remote control unit 4 are attached.
[0025]
The vehicle navigation apparatus 1 includes a receiver 12 that receives traffic information through an external antenna 2, a hard disk memory 13 that stores at least link travel time information included in the received traffic information, and a stored link travel time. Smoothing processing obtained by the travel time calculation unit 14 that obtains the smoothed link travel time by the smoothing process, the link travel time information stored in the road map data memory 5, and the travel time calculation unit 14 A route calculating unit 15 that calculates a route based on the link travel time information, an interface unit 16 that takes a man-machine interface, an azimuth sensor that detects the amount of azimuth change of the vehicle, and a distance sensor that detects the amount of movement of the vehicle. And a position detection unit 17 that detects the current position of the vehicle using the detection signal and the road map data. .
[0026]
The position detection unit 17 may employ a GPS receiver that detects the current location of the vehicle based on propagation delay time information of GPS radio waves transmitted from a GPS (Global Posioning System) satellite navigating the earth orbit. Good.
The road map data stored in the road map memory 5 is a mesh of road maps (including national highways, roads dedicated to automobiles, other national roads, prefectural roads, city roads of government-designated cities, and other living roads). A relatively small second route network consisting of a combination of nodes corresponding to road intersections etc. in each mesh unit and links (hereinafter referred to as “navigation links”) connecting each link for a certain period of time It is memorized with statistical link travel time data.
[0027]
The road map memory 5 stores a link correspondence table representing the correspondence between the traffic information link and the navigation link in addition to the road map data. As a correspondence relationship between a traffic information link and a navigation link, (1) When a traffic information link and a navigation link correspond one-to-one, (2) a series of a plurality of navigation links correspond to one traffic information link. If there is. Such a relationship is defined in the first correspondence table.
[0028]
The route calculation unit 15 uses the remote controller key 4 by the driver to determine the destination and various calculation conditions (whether toll roads are prioritized, ferry use is prioritized, transit points are used, etc. ) Is read out from the road map memory 5, and the shortest time path between the destination and the navigation links close to the current location detected by the vehicle position detection unit 17 is, for example, the Dijkstra method or the potential method. Use to calculate. The calculated shortest time path is superimposed and displayed on the road map displayed on the display device 3 with, for example, a broken line.
[0029]
Here, the potential method is the following method. That is, the navigation link near the departure point (or the destination) may be used as the calculation start link, the navigation link closest to the destination (or the departure point) may be used as the calculation end link, and the navigation within the predetermined map area starting from the calculation start link. Search all links. At this time, the link travel time of each navigation link is sequentially added, and the process of discarding the non-shortest route and leaving only the route that realizes the shortest route is repeated. As a result, a tree of routes consisting only of the shortest route is finally obtained. Therefore, if the route from the calculation end link to the calculation start link is traced in reverse, the shortest time route can be obtained.
[0030]
The travel time data handling process performed by the travel time calculation unit 14 will be described below with reference to a flowchart (FIG. 3). When the vehicle enters the transmission area of the road beacons B1, B2,... (See FIG. 1) and receives traffic information (step S1), the travel time calculation unit 14 gives the traffic information to the hard disk memory 13. (Step S2).
[0031]
When the travel time calculation unit 14 requests travel time data for a predetermined range of traffic information links including the current location and destination from the route calculation unit 15 (step S3), the travel time calculation unit 14 sequentially extracts the traffic information links within the range. (Step S5), link travel time information held in the hard disk memory 13 is acquired.
If a single piece of link travel time information for the same link is stored in the hard disk memory 13, the data is directly supplied to the route calculation unit 15 (step S8).
[0032]
When a plurality of link travel time information for the same link is held in the hard disk memory 13, the following time-series weighted smoothing process is performed (step S7).
FIG. 4 is a block diagram for explaining the specific contents of the time-series weighted smoothing process.
[0033]
The time-series weighted smoothing process is executed using the control response characteristic of the traffic control system (response time is T) and the weighting coefficients α, β,.
Now, let tn, tn-1, tn-2,... Be a plurality of travel times of the traffic information link to be processed. It is assumed that tn is the latest data, and the data acquired retroactively as n decreases. Furthermore, it is assumed that the acquisition time interval is constant (for example, tn-1 is data 10 minutes before, tn-2 is data 20 minutes before, and tn-m is data 10 m before). When travel time data at a certain time is missing, interpolation is performed with the preceding and following data.
[0034]
In this smoothing process, (a) Travel time before a certain period in the past is not taken into account (the weight is set to 0), or (b) The weight that takes travel time into account is gradually reduced as the past. And
If it is the process of (a), the following methods can be illustrated.
(a-1) Take travel time data tn, tn-1, tn-2 at the present 1 time point and the past 2 time points,
(Αtn-2 + βtn-1 + tn) / (α + β + 1)
Calculate At this time, the response time T is divided into a plurality of stages, for example, 0 minutes, 1 minute-10 minutes, 10 minutes-20 minutes,..., If T is 0 minutes, α = 0 and β = 0, and T = 1 From minutes to 10 minutes, α = 0.01, β = 0.1, and when T is from 10 minutes to 20 minutes, α = 0.1, β = 0.5, and so on. That is, the shorter the response time T, the more important is the latest data, and the longer the response time T, the higher the weight of past data.
[0035]
(a-2) It is also possible to take out all the data traced back in the past by the response time and average it with a weighted average or an equal weight. For example, if the response time T is 30 minutes, data tn, tn-1, tn-2, tn-3 up to the past 30 minutes are taken. The weighting coefficient may be larger for data closer to the present, smaller for older data, or may be equal.
[0036]
If it is the process of (b), the following methods can be illustrated.
All travel time data tn, tn-1, tn-2,... Are taken out and weighted averaged. Depending on the response time, the weighting coefficient is larger for data closer to the present time and smaller for older data. For example, as a weighting coefficient for data of M minutes ago,
e^{-M / T}
Is adopted. Since it is an exponential function, the coefficient decreases rapidly as M increases.
[0037]
Note that the weighting coefficient can be changed automatically by the vehicle navigation device or manually by the driver. For example, when there is a local accident and a sudden change in the link travel time is expected, if the past smoothing coefficient is large, this fluctuation cannot be reflected. It is conceivable that the past smoothing coefficient is ignored and the past smoothing coefficient is ignored.
[0038]
This process may be performed by using the remote controller key 4 as an instruction from the driver, or if a special code is included in the traffic information, receiving the code signal as a trigger. This makes it possible to perform route calculation in accordance with the current road traffic situation.
Here, how to determine the response time T will be described with reference to FIG. As shown in FIG. 4, the response time T is determined based on the current position of the vehicle, the type of the surrounding road, the road width, the traffic information, and the current time.
[0039]
If the traffic information includes data of response time T corresponding to the current position of the vehicle (the running link), the data is adopted.
Even when the response time T data cannot be obtained from the outside or is obtained, the response time T data is registered in a memory in the vehicle navigation device 1, for example, the road map memory 5. It is possible. Possible ways of registration include registering response time T data in association with each link, registering response time T data in regions and mesh units, and the like.
[0040]
When registering the response time T in units of regions or meshes, it is conceivable to correct the response time T according to the type of road on which the vehicle is traveling. For example, it is considered that road infrastructure development is progressing for high-level roads such as national roads, and response time T is shortened, and road infrastructure development is relatively not advanced for local roads. To increase the response time T.
[0041]
It is also conceivable to correct the obtained response time T according to time. For example, it is determined that the control response characteristic of the traffic control system is advanced in a time zone with a lot of traffic and the response time T is shortened, and it is determined that the control response characteristic is not advanced in a night time zone. Is corrected for a long time.
Furthermore, the travel time data included in the road map memory 5 may be taken with a certain weight. The travel time data included in the road map memory 5 is considered to be statistical data over the past and long term, meaning that it is respected.
[0042]
When the route calculation unit 15 receives the link travel time data from the travel time calculation unit 14, if it is a relatively rough traffic information link, the route calculation unit 15 uses the link correspondence table, if necessary, to calculate the travel time of the navigation link. Convert to data. For example, when the traffic information link and the navigation link have a one-to-one correspondence, the travel time data of the traffic information link is used as the travel time data of the navigation link as it is. When a navigation link corresponds, the travel time data of the traffic information link is the sum of the travel time data of each navigation link.
[0043]
If the travel time data of the traffic information link is missing, or if the destination is off the main road and there is no traffic information link, the travel time of the navigation link stored in the road map memory 5 Data should be adopted. Further, a method of correcting the travel time data of the navigation link with reference to the fluctuation of the travel time data of the nearby traffic information link from which the link travel time data is obtained can be considered. This is because if a certain road is congested, it can be expected that the roads in the vicinity are also congested.
[0044]
When the travel time information of the link to the destination is obtained in this way, the route calculation unit 15 calculates the shortest time route as described above. Then, when a predetermined point where the route is guided, for example, a predetermined distance before an intersection on the route, etc., is reached, the direction of the intersection and the direction of guidance are instructed by the display screen or voice of the display device 3 and the route is guided. .
[0045]
The contents of the guidance instruction information corresponding to the shortest time route are conventionally known, such as the direction to the destination, the straight line distance to the destination, the route distance and travel time along the shortest time route, and an intersection schematic diagram. There are various things and any or all of these information is presented to the driver.
The description of the embodiment of the present invention is as described above, but the present invention is not limited to the above-described embodiment. For example, instead of road beacons B1, B2,..., For example, leaky coaxial cables, automobile / mobile phone networks, TV / FM multiplex broadcast networks, communication satellites, broadcast satellites, etc. are applied as means for transmitting data to vehicles. May be. In addition, various design changes can be made within the scope of the present invention.
[Brief description of the drawings]
FIG. 1 is a schematic view of a system for providing traffic information to a vehicle navigation apparatus of the present invention.
FIG. 2 is a block diagram showing an electrical configuration of the vehicle navigation apparatus.
FIG. 3 is a flowchart for explaining travel time data handling processing performed by a travel time calculation unit 14;
FIG. 4 is a block diagram for explaining a method of determining a response time T based on the current position of a vehicle, the type of surrounding road, road width, traffic information, and the current time.
FIG. 5 is a graph showing a time variation of a travel time of a link detected by a vehicle sensor.
[Explanation of symbols]
B1, B2, ... Road beacons
C Control Center
L Communication line
a, b, ..., f links
1 Vehicle navigation system
2 External antenna
5 Road map data memory
3 display devices
4 Remote control unit
12 Receiver
13 Hard disk memory
14 Travel time calculator
15 Route calculator
16 Interface section
17 Position detector

Claims (7)

Road map data storage means for storing road map data associated with a link which is a constituent unit of a route network;
Receiving means for receiving traffic information including link travel time transmitted from an external communication device;
When the traffic information is received by the receiving means, link travel time acquisition means for acquiring and holding the link travel time of each link based on the traffic information;
Link travel time correction means for smoothing the link travel time of the same link acquired and held by the link travel time acquisition means to obtain a smoothed link travel time;
A route calculation means for calculating a route based on the smoothed link travel time obtained by the link travel time correction means and the road map data stored in the road map data storage means,
The link travel time correcting means performs time series weighting of the smoothing processing based on a control response characteristic of a traffic control system in a region where the vehicle travels. The vehicle navigation apparatus according to claim 1, wherein the control response characteristic of the traffic control system is determined according to a current position of the vehicle detected by the navigation apparatus. The vehicle navigation apparatus according to claim 1, wherein the control response characteristic of the traffic control system is determined based on traffic information received by the receiving means. 4. The vehicle navigation apparatus according to claim 2, wherein the control response characteristic of the traffic control system is corrected according to the type and width of a road existing around the current position of the vehicle. The vehicle navigation apparatus according to claim 2 or 3, wherein a control response characteristic of the traffic control system is corrected according to a current time. 4. The vehicle navigation apparatus according to claim 3, wherein the control response characteristic of the traffic control system for the link to the destination is acquired by transmitting the destination to the control center. The vehicle navigation apparatus according to claim 1, wherein the degree of time series weighting performed by the link travel time correcting means can be set by a user.

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