JP5474611B2 - Navigation device and route search method - Google Patents

Description

  The present invention relates to a navigation device and a route search method, and in particular, follows each node along a plurality of routes while sequentially adding link costs from a departure node to a destination node, and guides a route with the lowest accumulated cost. It is suitable for use in a navigation device having a route search function for searching as a route.

  In general, in a route search function provided in a navigation apparatus, an algorithm called Dijkstra method is often used. One of the methods for calculating the optimum route from various routes that can be taken as the route from the starting point to the destination is the Dijkstra method.

  In the Dijkstra method, search branches are extended along a plurality of routes while sequentially adding link costs from a departure node to a destination node. In the process of extending the search branch, if a different route arrives at the same node on the way, the route with the lower cumulative cost is adopted, and the route with the higher cumulative cost is canceled from the subsequent search. . This is because even if searching further, it is considered that the optimum route from the departure node to the destination node cannot be obtained. Terminating the search for a route that is determined to be an optimal route on the way is called “branch hunting”. In the Dijkstra method, the search is advanced while branching from the departure node to the destination node, so that it is possible to efficiently obtain the optimum route between the two points.

  The road between the departure point and the destination has various attributes such as road width and road type, and there may be traffic restrictions. The link cost attached to each link expressed by dividing roads and lanes is different depending on these road attributes and traffic regulations. That is, the link cost is set as a value multiplied by a predetermined constant according to the road width, road type, right and left turns, traffic regulations, etc. Is a numerical value.

  By the way, there are pedestrian roads, single car roads, private roads, etc. among the roads. 2. Description of the Related Art Conventionally, a technique has been proposed in which an optimal route including a road where a vehicle cannot pass can be searched for (see, for example, Patent Document 1). In Patent Document 1, when there is a link having an inaccessible condition, a search is performed by temporarily canceling the inaccessible condition, and after the search is completed, only the accessible road is adopted as a recommended route. Yes.

JP 11-344350 A

  As described above, the Dijkstra method advances the search while branch-hunting from the departure node to the destination node, so that the number of search branch candidates is prevented from increasing explosively and the optimal route between the two points is efficient. Can be obtained. However, since branch hunting is sequentially performed in the search process, there is a problem that a truly optimal route may not be searched. This problem will be described in detail below.

  For example, in the road where the upper and lower lines are separated by the central separator as shown in FIG. 8A, the nodes and links of the map data are as shown in FIG. 8B. In FIG. 8B, L1 to L7 are links, which correspond to individual vectors when roads and lanes are finely divided and represented by a connection of a plurality of vectors. For each of these links L1 to L7, link costs corresponding to road attributes, traffic regulations, and the like are set. N1 to N8 are nodes and correspond to both end points of each link.

  Assume that there is a restriction that prohibits a U-turn as shown in FIG. 9A as a traffic restriction on the road where the vertical lines are separated in this way. In this case, as shown in FIG. 9B, the link L6 corresponding to the terminal link constituting the U-turn path on the map data cannot be passed through the “link L7 → L4 → L6”. The traffic regulation information is attached.

  In such a road network, when the first route searched in the order of “... → L7 → L4” and the second route searched in the order of “... → L5 → L4” are compared. In the Dijkstra method, the one with the higher accumulated cost up to the link L4 (up to the node N4) is hunted. The reason why the branch is not picked when both the first route and the second route arrive at the node N5 is that the link cost is attached to the left turn and the right turn, so the left turn from the link L7 to the link L4. This is because the correct accumulated cost cannot be compared unless the link cost is added.

  Here, as a result of comparing the accumulated costs up to the link L4, if the accumulated cost of the second route is higher, the second route is pruned and no further search is performed. However, if the first route “... → L7 → L4 → L6” added up to the next link L6 is compared with the second route “... → L5 → L4 → L6”, the first route is Passing is prohibited on the U-turn. Therefore, when viewed at the point of the link L6, the accumulated cost may be lower for the second route than for the first route. However, since the second route has already been picked at the point of the link L4, the second route is not actually selected.

  In such a case, another third route that is neither the first route nor the second route is selected as the optimum route. For example, it is assumed that a route search from the vehicle position (link L13) to the destination (link L9) is performed on the road network as shown in FIG. In this case, the optimal route to the link L4 is assumed to be the first route of “L13 → L10 → L7 → L4”. However, since the traffic restriction prohibiting passage is attached to the route “L7 → L4 → L6”, the actual optimum route to the destination is “L13 → L8 → L5 → L4 → L6 → L9”. Assume that there are two routes.

  In such a case, when the first route and the second route are compared at the point of the link L4, the accumulated cost up to the link L4 is higher in the second route than in the first route. Is done. Thereafter, the search branch of the first route is extended to the link L6, but the route arriving at the link L6 includes a third route “L13 → L8 → L14 → L16 → L15 → L1 → L6” in addition to the first route. A route exists.

  Comparing the first route and the third route at the point of the link L6, the traffic prohibition of passage of the first route is set, so the accumulated cost is higher than the third route, and the first route is Hunted. As a result, the third route is calculated as the optimum route. Thus, in the case of a road network in which passage prohibition (hereinafter referred to as “special traffic regulation”) is set across three or more links, the original optimum route (second route) may not be calculated. is there.

  The present invention has been made to solve such a problem. In an algorithm for performing a route search while performing branch hunting based on the accumulated cost from the departure node to the destination node, a special The purpose is to enable the calculation of the original optimum route even if traffic restrictions exist.

In order to solve the above-described problems, in the present invention, in the process of extending the search branch while sequentially adding the link costs of various routes from the departure node to the destination node, it is set across three or more links. when detecting a special traffic regulation information in the starting link, among the three or more links to the special traffic regulation is set, the intermediate link, excluding the start link and the end link, the search branches with respect to the intermediate link Forbid the branch hunting when it grows, and search for the route with the lowest total link cost from the departure node to the destination node, including the route that forbids the branch hunting and extended the search branch I have to.

  According to the present invention configured as described above, a plurality of routes are accumulated in a link that constitutes a route (referred to as a first route) that is never selected as the optimum route due to the presence of special traffic regulations. As a result of comparing the costs, even if the route without special traffic regulations (the second route) has a higher accumulated cost and is hunted for branching, the route is searched including the second route. The route search is performed while extending the branch.

  For this reason, in the link ahead of which the search branch is extended, the cumulative cost is lower than that of the first route in the third route whose cumulative cost is lower than that of the first route in which the special traffic regulation is set, and in the link before the search branch is extended. Is compared with the second route that has been higher, and the lower cumulative cost is selected, and the higher cumulative cost is pruned. At this time, if the accumulated cost of the second route is lower than that of the third route, the second route that should have been branch-hunted because the accumulated cost is higher than the first route is selected as the optimum route. . Thereby, even if special traffic regulations exist on the link, the true optimum route can be calculated.

It is a block diagram which shows the function structural example of the navigation apparatus by this embodiment. It is a figure which shows the example of the road network which performs the route search by this embodiment. It is a figure which shows the example of the road network which performs the route search by this embodiment. It is a figure which shows the example of a route search by this embodiment. It is a figure which shows the example of a route search by this embodiment. It is a figure which shows the example of a route search by this embodiment. It is a flowchart which shows the operation example (route search method) of the navigation apparatus by this embodiment. It is a figure which shows the example of a road network. It is a figure which shows the example of a road network. It is a figure which shows the example of the conventional route search.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram illustrating a functional configuration example of the navigation device according to the present embodiment. As shown in FIG. 1, the navigation device 10 of the present embodiment includes, as its functional configuration, a map readout control unit 11, a map memory 12, a position measurement unit 13, a destination setting unit 14, a route search unit 15, and a guidance route memory. 16 is provided.

  The map reading control unit 11 controls reading of map data stored in a DVD (Digital Versatile Disk) 20. Specifically, the map reading control unit 11 inputs the current position information of the host vehicle from the position measuring unit 13, and outputs a map data reading instruction within a predetermined range including the current vehicle position, thereby displaying a map display or Map data necessary for route search is read from the DVD 20 and stored in the map memory 12.

  The map memory 12 corresponds to a map data storage unit of the present invention, and temporarily stores map data read from the DVD 20 under the control of the map read control unit 11. The map data stored in the map memory 12 includes road units composed of data necessary for processing such as map matching and route search. This road unit includes information on links corresponding to individual vectors when roads and lanes are subdivided and represented by a connection of a plurality of vectors, and information on nodes corresponding to both end points of each link. ing.

  As information about links, information such as link distance, cost, road attribute, road type, and the like is given to each link. In addition, when traffic regulation such as prohibition of passage is set across three or more links, the special traffic regulation information indicating the traffic regulation is at least one of the three or more links constituting the regulation. Has been granted. In the present embodiment, it is assumed that special traffic regulation information is given to the termination link among the three or more links constituting the regulation.

  The position measurement unit 13 measures the current position of the vehicle, and includes a self-contained navigation sensor, a GPS receiver, a position calculation CPU, and the like. The self-contained navigation sensor includes a vehicle speed sensor (distance sensor) that outputs a single pulse for each predetermined travel distance to detect the travel distance of the vehicle, and an angular velocity sensor such as a vibration gyro that detects the rotation angle (movement direction) of the vehicle (Relative orientation sensor). The self-contained navigation sensor detects the relative position and direction of the vehicle using these vehicle speed sensor and angular velocity sensor.

  The position calculation CPU calculates the absolute own vehicle position (estimated vehicle position) and vehicle direction based on the relative position and direction data of the own vehicle output from the self-contained navigation sensor. The GPS receiver receives radio waves transmitted from a plurality of GPS satellites by a GPS antenna and performs a three-dimensional positioning process or a two-dimensional positioning process to calculate the absolute position and direction of the vehicle (the vehicle direction is The calculation is based on the current vehicle position and the current vehicle position one sampling time ΔT before).

  The destination setting unit 14 sets the destination of the guidance route through the operation of the remote controller 30 by the user. The route search unit 15 searches for a guide route with the lowest cost connecting from the departure point to the destination set by the destination setting unit 14 using the current vehicle position measured by the position measurement unit 13 as a departure point. Then, the route search unit 15 stores the data of the searched guide route in the guide route memory 16.

  The route search unit 15 uses the Dijkstra method as a route search algorithm. That is, the route search unit 15 sequentially adds link costs on various routes from the departure node to the destination node, and performs branch hunting based on the accumulated cost up to the link on the way, A route having the smallest link cost to the ground node is searched.

  At this time, the route search unit 15 has the highest total link cost from the departure node to the destination node, including the route searched without branching in the link for which traffic restriction is set by the special traffic restriction information. Search for a small route. Specifically, the route search unit 15 compares the accumulated costs regarding various routes up to the end link of three or more links for which traffic regulation is set by special traffic regulation information. In addition, a route that has already been pruned on a link for which special traffic regulations are set is restored to the search target, and the accumulated costs are compared.

  It should be noted that all the data of each route obtained in the route search process, including the data of the route hunted, are stored in the guidance route memory 16 so that the route hunted can be restored at any time. When the route search from the departure point to the destination is completed, the data related to the branch-hunted route is deleted from the guidance route memory 16.

  After reviving a route that once picked a branch, branch hunting should not be performed on the link row for which special traffic regulations are set for the revived route. The next link on the revived route may not be the end link of the link train constituting the special traffic regulation. Therefore, if branch hunting is not prohibited, the search branch of the restored route will be picked again before extending to the end link of the special traffic regulation, and it will be useless that it has been restored. is there.

  In addition, regarding the restored route, branch hunting may be prohibited in all link trains for which special traffic regulations are set, but branch hunting is permitted in the end link in the link train. Also good. This is because even if branch hunting is performed at the end link, the searched branch of the restored route is not picked again before reaching the end link of the special traffic regulation. In the present embodiment, description will be made assuming that branch hunting is permitted in the termination link.

  The actual operation will be described below with an example. For example, when there is a road network as shown in FIG. 2 and a link L7 corresponding to a terminal link constituting a U-turn route is passed through “link L8 → L5 → L4 → L7”, special traffic that cannot pass It is assumed that regulatory information is attached. When the route search unit 15 searches for a guidance route based on map data having such a road network, along the two routes (first route and second route) as shown in FIG. 3 during the search. Assume that the search branch extends to the link L5.

  The first route is a route in which the search branches extend in the order of “... → L8 → L5” and arrive at the link L5. On the other hand, the second route is a route in which the search branch extends in the order of “... → L6 → L5” and arrives at the link L5. As a result of comparing the accumulated costs up to the link L5 between the first route and the second route, if the accumulated cost of the first route is lower, the route search unit 15 branches the second route at this point, Select the first route.

  The route search unit 15 continues the search process for the selected first route. When the search branch extends to the link L7 as shown in FIG. 4, the route search unit 15 detects that the special traffic regulation information is given to the link L7. In response to this, the route search unit 15 restores the second route that has already been hunted in the link L5 for which traffic regulation is set based on the detected special traffic regulation information to the search target as shown in FIG.

  The route search unit 15 resumes the search process for the second route restored to the search target. Thereby, the search branch of the second route once picked by the link L5 is extended to the link L4. In this case, the link L4 has already been searched for in the first route, but the link L4 is one of the link trains constituting the special traffic regulation and is not a terminal link. Does not execute.

  Subsequently, the route search unit 15 extends the search branch of the second route to the link L7 as shown in FIG. Since the link L7 corresponds to the end link of the link train constituting the special traffic regulation, the route search unit 15 performs branch hunting. That is, the route search unit 15 compares the accumulated costs up to the link L7 between the first route and the second route, selects the lower accumulated cost, and hunts the higher accumulated cost. Here, since the special traffic regulation is set for the first route, the accumulated cost to the link L7 is higher than that for the second route. As a result, the route search unit 15 branches the first route and selects the second route.

  Here, although it has been described that the accumulated costs are compared for the two routes, the first route and the second route, other routes (for example, “... → L8 → L2 →... → L1 If there is a third route (→ L7)), the accumulated costs are compared including the third route. That is, the route search unit 15 uses the first route for which the special traffic regulation is set, the third route whose accumulated cost is lower, and the restored second route in the link L7 to which the search branch is extended. And compare. At this time, if the accumulated cost of the second route is lower than that of the third route, the route search unit 15 branches the first route and the third route, and the accumulated cost is higher than the first route. The second route that has undergone branch picking is selected as the optimum route.

  Thus, according to the present embodiment, the accumulation of the first route and the second route in the link L5 that constitutes the first route that is never selected as the optimum route due to the presence of special traffic regulations. As a result of comparing the costs, even if the second route without special traffic regulations has a higher accumulated cost and the branch is hunted, while extending the search branch including the second route, It is possible to search for an optimum route. That is, the route search unit 15 can select the second route as the optimum route and continuously search for the route to the destination.

  Although explanation is omitted in FIG. 5, the route restored by detecting the special traffic regulation information when the search branch extends to the link L7 is not limited to the second route hunted at the link L5. There is also a route (not shown) that has been branch-hunted at the link L8. However, since the route revived by the link L8 will follow the link as L5 → L4 → L7 (the links L5 and L4 are not end links and are not hunted for branching). The route cannot pass due to traffic restrictions and is hunted on a link L7.

  In this way, in order to prevent the search branch from being unnecessarily extended for a route that is known to be pruned, special traffic regulation is configured for the start link L8 of the link train that constitutes the special traffic regulation. Information indicating that the link is the start link of the link sequence to be performed. Further, branching is permitted not only at the end link of the link train constituting the special traffic regulation but also at the starting link (that is, branching is prohibited only at the intermediate link excluding the starting link and the terminating link). Good.

  FIG. 7 is a flowchart showing an operation example (route search method) of the navigation device 10 according to the present embodiment. The flowchart shown in FIG. 7 starts when the destination of the route search is issued after setting the destination of the guidance route. In FIG. 7, the route search unit 15 extends the search branch to the next link in order from the departure point node, and calculates the accumulated cost up to the extended link (step S1).

  Moreover, the route search part 15 determines whether special traffic regulation information is provided with respect to the extended destination link (step S2). If the special traffic regulation information is not given to the link, the link is not a terminal link constituting the special traffic regulation. In this case, when there are a plurality of routes arriving at the link, the route search unit 15 compares the accumulated costs regarding the plurality of routes up to the link. Then, the route with the highest accumulated cost is pruned and the route with the lowest accumulated cost is selected (step S3).

  Next, the route search unit 15 determines whether or not the search branch has extended to the destination, that is, whether or not the route search from the departure point to the destination has been completed (step S4). If the search branch has not yet reached the destination, the process returns to step S1. Then, the route search unit 15 continues the search process for the selected route without branching. That is, the search branch is further extended to the next link, and the accumulated cost to the extended link is calculated.

  Then, it is determined again whether or not special traffic regulation information is given to the extended link (step S2). Here, if the special traffic regulation information is given to the link, the link is a terminal link constituting the special traffic regulation. In this case, the route search unit 15 restores a route that has already been pruned in any of the link trains for which special traffic regulations are set (step S5).

  After restoring the branch-hunted route, the route search unit 15 extends the searched branch of the restored route to the next link, and calculates the accumulated cost up to the extended link (step S6). Here, it is determined whether or not the extended link is a terminal link in the link train for which special traffic regulation is set (step S7). If special traffic regulation information is given to the extended link, it can be determined that the link is a terminal link.

  If the link extended for the restored route is not the terminal link, branch picking at that time is prohibited, and the process returns to step S6. That is, the search branch is further extended to the next link, and the accumulated cost to the extended link is calculated. On the other hand, when the link extended about the restored route is a termination link, the process proceeds to step S3. When the above steps S1 to S7 are performed and the search branches are sequentially extended, the branches are picked on the way, and when the search branches are extended to the destination, a series of route search processes are completed.

  As described above in detail, in this embodiment, in the process of extending the search branch while sequentially adding the link costs of various routes from the departure node to the destination node, the special traffic regulation information given to the link is displayed. If detected, the route that has been pruned in the link for which traffic regulation is set by the special traffic regulation information is restored, and the route with the smallest total link cost from the departure node to the destination node is searched. I have to.

  According to the present embodiment configured as described above, a route with no special traffic regulation is set rather than a route (first route) that is never selected as an optimum route because special traffic regulation exists. Even in the case where the accumulated cost is higher for the (second route), it is possible to search for the optimum route while extending the search branch including the second route. Thereby, even if special traffic regulations exist on the link, the true optimum route can be calculated.

  In addition, although the said embodiment demonstrated the example which resurrected the route which carried out the branch hunting in any of the link queue | trains with which special traffic regulation is set, this invention is not limited to this. For example, among the three or more links for which special traffic regulations are set, only the route that has been branch-hunted in the intermediate link excluding the start link and the end link may be restored. This is because it does not make sense to restore the route that was pruned at the start and end links.

  That is, even if the route picked at the start link is revived, the route is eventually picked based on the special traffic regulation information given to the end link to which the search branch is extended. On the other hand, the route that has been pruned at the end link has a higher accumulated cost than other routes other than those that constitute the special traffic regulations. Eventually, the cost is higher than that of the other route, and the branches are hunted. Therefore, by not restoring the route that is pruned at the start link and the end link, it is possible to omit useless processing that is meaningless and to obtain an optimum route efficiently.

  Moreover, in the said embodiment, special traffic regulation information is provided to the termination link among three or more links which constitute special traffic regulation, and when special traffic regulation information was detected, it was already pruned. Although an example of restoring the route has been described, the present invention is not limited to this. For example, instead of or in addition to the end link, special traffic regulation information may be given to the start link. In this case, when the route search unit 15 detects that the special traffic regulation information is given to the starting link, the route search unit 15 performs a route search by prohibiting branch hunting in the link row in which the special traffic regulation is set. . In addition, you may make it prohibit branching only in the intermediate link except the start end link and the termination | terminus link among the link strings which comprise special traffic regulation.

  Moreover, although the said embodiment demonstrated the example which has special traffic regulation information as information regarding a link, you may make it have special traffic regulation information as information regarding a node.

  Moreover, although the said embodiment demonstrated the example which performs a route search by the Dijkstra method, the algorithm which can apply this invention is not limited to this. In other words, if the algorithm is to hunt branches in the process of extending the search branch along a plurality of routes in order from the departure node to the destination node, and finally search for a route with the minimum link cost, The present invention can be applied.

  In addition, each of the above-described embodiments is merely an example of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed in a limited manner. In other words, the present invention can be implemented in various forms without departing from the spirit or main features thereof.

10 navigation device 12 map memory (map data storage unit)
15 Route search unit

Claims (2)

A map data storage unit that stores map data in which special traffic regulation information representing traffic regulation set across three or more links is given to the starting link among the three or more links;
Link costs on various routes from the departure node to the destination node included in the map data are sequentially added, and the link cost to the destination node is hunted based on the accumulated cost up to the middle link. A route search unit that searches for a route having the smallest sum of
When the route search unit detects that the special traffic regulation information is given to the starting link among the three or more links, the starting link and the terminating link are excluded from the three or more links. In an intermediate link, a link from the departure node to the destination node is also included, including a route searched by prohibiting branch hunting when the search branch extends with respect to the intermediate link, and prohibiting the branch hunting. A navigation device characterized by searching for a route having the smallest total cost. Various traffic from the departure node to the destination node based on the map data in which special traffic regulation information representing traffic regulation set over three or more links is given to the starting link among the three or more links. This is a route search method for a navigation device that sequentially adds the link costs on a simple route and searches for the route with the smallest total link cost to the destination node while pruning based on the accumulated cost up to the intermediate link. And
A first step in which the route search unit of the navigation device determines whether or not the special traffic regulation information is given to the starting link among the three or more links;
The route search unit, when detecting the specific traffic control information in the beginning link, among the three or more links in which the traffic regulation is set, the intermediate link, excluding the start link and the end link, the A second step of prohibiting branch hunting when the search branch extends with respect to the intermediate link ;
The route search unit compares the accumulated costs regarding various routes up to the end link, including the route where the branching is forbidden by prohibiting the branch hunting, and the route having the higher accumulated cost is branched. A route search method comprising: a third step of hunting.