Data processing: vehicles – navigation – and relative location – Navigation – Employing position determining equipment
Reexamination Certificate
2002-07-22
2004-06-15
Beaulieu, Yonel (Department: 3661)
Data processing: vehicles, navigation, and relative location
Navigation
Employing position determining equipment
C701S209000
Reexamination Certificate
active
06751550
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to navigation apparatuses. More specifically, the present invention relates to a navigation apparatus that has a route searching function for searching for a route to a destination, a detour route searching function for searching for a detour route for detouring around a partial segment of a route found by the route searching function, and a return route searching function for searching for a return route for returning to an original route when a vehicle turns off the route.
2. Description of the Related Art
On-vehicle navigation apparatuses generally have various functions including a map displaying function for displaying a map of the vicinity of the position of the vehicle on a screen, a route searching function for searching for a route to a destination or a point on route specified by a user, and a route guidance function for guiding the vehicle to travel along a route found by a route search.
Furthermore, many navigation apparatuses have a detour route searching function for searching for a detour route for detouring around a segment of a current route, for example, when the traffic is heavy on the current route, and a return route searching function for searching for a return route for returning to an original route when the vehicle turns off the route.
For the detour route searching function, a distance to be detoured (e.g., two kilometers) is specified and a high cost is set for a road in the segment to be detoured, so that a detour route for returning to an initial route is searched for while avoiding the segment.
For the return route searching function, when the vehicle turns off the route, a route for returning to a point on an initial route (e.g., an intersection that has not been passed and that is nearest to the position of the vehicle) at an optimal cost is searched for as a return route.
In a conventional navigation apparatus, it sometimes occurs that an inappropriate detour route is set when a search for a detour route is repeated in a relatively short period.
FIGS. 10A
to
10
C are diagrams showing an example where an inappropriate detour route is set in a conventional navigation apparatus. A case where a route r
1
to a destination d is set and an instruction for calculation of a detour route is issued three times repeatedly, as shown in
FIG. 10A
, will be considered. Since it is unlikely that a user changes the detour distance each time the calculation instruction is issued, it is assumed that the detour distance is fixed at a preset value (e.g., two kilometers).
In this case, when a first instruction for calculation of a detour route is issued, a detour route r
2
for returning to the initial route r
1
from the current position g of the vehicle while detouring a segment p
1
corresponding to the detour distance is searched for, as shown in FIG.
10
A. Then, when a second instruction for calculation of a detour route is issued, a new return route r
3
for returning to the previous detour route r
2
from the current position g of the vehicle while detouring a segment p
2
corresponding to the detour distance is searched for, as shown in FIG.
10
B. Then, when a third instruction for calculation of a detour route is issued, a new return route r
4
for returning to the previous detour route r
3
from the current position g of the vehicle while detouring a segment p
3
corresponding to the detour distance is searched for, as shown in FIG.
10
C.
When a search for a detour route is repeated in a relatively short period as described above, in order to return to the original route r
1
, the vehicle first returns to the detour route r
3
via the detour route r
4
, then returns to the detour route r
2
via the detour route r
3
, and finally returns to the original route r
1
via the detour route r
2
, as shown in FIG.
10
C. Thus, more than a necessary number of right turns and left turns are made to return to the original route r
1
; that is, a detour route with many deviations overall is set. Such a return route incurs an increased travel distance and time, which is inappropriate in consideration of the original intent to find a detour route for detouring part of the original route r
1
in order to avoid an increase in travel time due to heavy traffic, etc. That is, the conventional navigation apparatus suffers from a problem that an inappropriate route is set when a search for a detour route is repeated several times.
Furthermore, when a search for a detour route has been repeated several times, in some cases more reasonable route guidance can be achieved by newly searching at that time for a route directly going to the destination than by returning to the original route. However, the conventional navigation apparatus does not execute such a process, and it simply searches for a detour route for returning to the original route irrespective of the current position of the vehicle, the distance to the destination, the distance of the detour route, etc.
A similar problem may also arise in searching for a return route when the vehicle has turned off a guided route. For example, when the vehicle has turned off an original route, a return route for returning to the original route is searched for, and if the vehicle further turns off the return route repeatedly, in some cases more reasonable route guidance can be achieved by newly searching at that time for a route directly going to the destination than by searching for a new return route for returning to the previous return route (or to the original route) each time. Even in such cases, the conventional navigation apparatus does not execute such a process, and it sometimes sets a lengthy, inappropriate return route irrespective of the current position of the vehicle, the distance to the destination, the distance of the detour route, etc., similar to the case of the detour route described above.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above problems, and it is an object of the present invention to provide a navigation apparatus in which the selection of an inappropriate route is prevented when a detour route or return route is calculated.
To this end, the present invention, in one aspect thereof, provides a navigation apparatus including a destination setting device for setting a destination; a route searching device for searching for an initial route to the destination set by the destination setting device, under a given condition; a detour calculation instruction device for instructing the calculation of a detour route; and a detour route searching device for searching for a detour route for returning to the initial route, wherein when an instruction for first calculation of a detour route is issued by the detour calculation instruction device with a detour distance specified, the detour route searching device searches for a detour route while increasing the cost of a link corresponding to the detour distance specified by the detour calculation instruction device, whereas when an instruction for a second or subsequent calculation of a detour route is issued, the detour route searching device searches for a detour route while increasing the cost of each link corresponding to a detour route that has been found according to a previous instruction for the calculation of a detour route.
When a second or subsequent calculation of a detour route is instructed, the cost of a link corresponding to the entire previous detour route is increased before searching for a new detour route for returning to the initial route, so that the selection of a lengthy, inappropriate detour route is prevented even if the search for a detour route is executed a plurality of times.
Preferably, the navigation apparatus further includes a route researching device for searching again for a route to the destination set by the destination setting device when an instruction for a second or subsequent calculation of a detour route is issued and if a ratio of a distance of a detour route found by the detour route searching device ex
Alpine Electronics Inc.
Beaulieu Yonel
Brinks Hofer Gilson & Lione
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