Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication
Reexamination Certificate
1999-07-12
2001-05-08
Nguyen, Tan (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
C340S995190, C701S210000
Reexamination Certificate
active
06230083
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a road shape predicting method for predicting the road shape on the basis of map data which are a collection of a plurality of nodes, and a vehicle controlling method using such a predicting method.
2. Description of the Related Art
Such a road shape predicting method and a vehicle controlling method were proposed in U.S. patent application Ser. No. 09/056,244 by the applicant of this invention. As seen from
FIG. 4
, they use coordinates of a larger number of nodes N
N
(N
N
=N
0
, N
1
, N
2
, N
3
, . . . ) set at prescribed intervals on a road as road map data. On the basis of a link length L
N
which is defined as a distance between adjacent nodes N
N
and N
N+1
, and a crossing angle &thgr;
N
formed by a certain link N
N−1
N
N
and another link N
N
N
N+1
located forward, a passing state decision quantity (vehicle cornering amount) &thgr;
N
/L
N
at each node is computed. The passable speed at the node N
N
computed on the basis of the passing state decision quantity &thgr;
N
/L
N
is compared with the passage predicting speed at the node N
N
through which an own vehicle passes. If it is decided that the passage is difficult, a warning is given to a driver or automatic speed reduction is made. The above passing state decision quantity &thgr;
N
/L
N
corresponds to a change quantity in the azimuth angle of a vehicle for a moving distance thereof. Its large value indicates that the road is curved, whereas its small value indicates that the road is straight.
Where there are three nodes N
0
, N
1
, N
2
, on a straight road as shown in
FIG. 9
, if the positions of the nodes are deviated from the inherent N
0
, N
1
, N
2
, to N
0
′, N
1
′, N
2
′, owing to an error in the road map data, at the node N
1
, the passing state quantity &thgr;
1
/L
1
which should not be essentially produced is produced. In this case, if the link length L
1
between N
1
and N
2
is sufficiently large, the passing state decision quantity &thgr;
1
/L
1
is relatively small so that the road shape is decided to be a gentle curve approximately to the straight road. Thus, no hitch occurs. On the other hand, if the link length L
1
between N
1
and N
2
is small, the passing state quantity &thgr;
1
/L
1
is fairly large so that the road shape which should be actually straight is decided to be erroneously curve.
SUMMARY OF THE INVENTION
The present invention has been accomplished in view of the above circumstance. An object of the present invention is to prevent the road shape from being falsely predicted owing to an error in road map data.
In order to attain the above object, according to the present invention, there is provided a road shape predicting method wherein three positions of the positions of a plurality of nodes constituting road map data and an own vehicle position on a road are selected, and the road shape is predicted on the basis of a crossing angle formed by a link connecting a first position and a second position of the selected three positions and another link connecting the second and a third position thereof and a link length between the second and the third position. Then, in case that the link length between the second and the third position is not larger than the reference link length set in accordance with the crossing angle, the third position is excluded, and the position of a node further forward is adopted in place of the third position to predict the road shape.
In this configuration, in case that the link length between the second and the third position is not larger than the reference link length set in accordance with the crossing angle of two links, the position of the node further forward is adopted in place of the third position to predict the road shape. Therefore, the link length necessarily exceeds the reference link length so that the predicting error in the road shape can be minimized.
In the above configuration, the link length L
ref
may be given by
L
ref
=A
{2
d
/tan(&thgr;/4)}
where
A: a coefficient satisfying 0<A<1
d: an upper limit of a sag
&thgr;: a crossing angle formed by two links.
In this configuration, in order to determine a standard for determining a reference link length, 2d/tan(&thgr;/4) that is the maximum value of the link length between the second and third positions is multiplied by a coefficient A that is larger than 0 and smaller than 1. Therefore, it is possible to avoid setting the reference link length at an excessively large value with anxiety about an increase in the error in the road shape. This prevents the inconvenience that the third position is excluded excessively.
In the embodiment, the above coefficient A is set in a range from 0.2 to 0.5. Therefore, it can be suitably set in a range satisfying 0<A<1 in accordance with the accuracy of the road map data. The upper limit of the sag d is defined as the upper limit of a distance between a link connecting two adjacent nodes and an actual road. In the embodiment, it is actually 2.5 m-6 m.
Further, in addition to the above configuration, in case that the link length between the position of the node further forward and the second position exceeds a prescribed length, the position of the node further forward is not adopted.
In this configuration, where the position of the node further forward is located forward to exceed a prescribed length from the second position, the position of the node further forward is not adopted. For this reason, it is possible to avoid adopting the node not presenting on the same curve to thereby prevent reduction in the predicting accuracy of the road shape.
Incidentally, in the embodiment, although the above prescribed length is set at the maximum link length L
max
, it may be a prescribed constant.
Further, according to another aspect, there is provided a vehicle controlling method using the above road shape predicting method, and the running state of a vehicle is controlled on the basis of the predicted road shape so that the vehicle can pass a forward road.
In this configuration, an error in a road map data is excluded to predict the road shape precisely and the running state is controlled so that the vehicle can pass the road having the predicted shape. For this reason, the vehicle can be suitably controlled according to the road shape so that the vehicle can surely pass a forward road.
REFERENCES:
patent: 5661650 (1997-08-01), Sekine et al.
patent: 6023653 (2000-02-01), Ichimura et al.
patent: 6058350 (2000-04-01), Ihara
patent: 6067497 (2000-04-01), Sekine et al.
patent: 6070121 (2000-04-01), Matsuda
patent: 10-283594 (1998-10-01), None
Matsuda Shohei
Otabe Makoto
Sakaki Yuji
Arent Fox Kintner & Plotkin & Kahn, PLLC
Honda Giken Kogyo Kabushiki Kaisha
Nguyen Tan
Tran Dalena
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