{DESCRIPTION}
{Title of Invention}
APPARATUS FOR VEHICLE AND POSITION CORRECTING METHOD THEREFOR
{Technical Field}
{0001}
The present invention relates to an apparatus for vehicle
and a position correcting method therefor.
{Background Art}
{0002}
In the related art, as a function of a car navigation
system, etc., there is known technology called map matching,
in which a traveling route is identified by using position
information obtained by using GPS, etc. and map information
prepared in advance (e.g., see Patent Literature 1).
Map matching is also being utilized in road pricing. For
example, map matching is being used to detect that a
predetermined charging position has been passed through and to
then execute charging processing.
{Citation List}
{Patent Literature}
{0003}
{PTL 1}
Japanese Unexamined Patent Application, Publication No.
2006-266986
{Summary of Invention}
2
{Technical Problem}
{0004}
Recently, in road pricing, there is a demand for
immediately notifying the driver when the driver has passed
through a predetermined charging position.
With the conventional map matching, however, an error
occurs between a traveling position on a map and an actual
traveling position due to an error in position detection by
means of GPS. Thus, there are cases where it is difficult to
instantly recognize that a predetermined charging position has
been passed through, and it is difficult to immediately notify
the driver that he or she has passed through the charging
position.
{0005}
An object of the present invention is to improve the
accuracy of position detection after an intersection is passed
through.
{Solution to Problem}
{0006}
A first aspect of the present invention is an apparatus
for vehicle including a position-information obtaining means
for obtaining position information of a moving object; an
intersection-information storage means for storing
intersection information in which, for at least one
intersection, the coordinates of intersection positions are
3
registered in association with combinations of a direction of
entry into and a turning direction at the intersection; a
detecting means for detecting, as a reference detection
position, the position of the moving object at the time when
an angle made by an advancing direction at a first
predetermined time before and a current advancing direction
has reached a first predetermined angle in an intersection
region set for each intersection; an intersection-position
obtaining means for obtaining, from the intersection
information, the coordinates of a relevant intersection
position based on a direction of entry of the moving object
into the intersection region and a turning direction of the
moving object in the intersection region; and a correcting
means for correcting the position information of the moving
object obtained by the position-information obtaining means by
using (i) the position coordinates of the intersection
position obtained by the intersection-position obtaining means
and (ii) the reference detection position detected by the
detecting means.
{0007}
According to this aspect, for each intersection, the
coordinates of intersection positions that serve as references
are registered in association with directions of entry into
the intersection and turning directions at the intersection.
When the moving object passes through an intersection, the
4
position information is corrected by using the coordinates of
an appropriate intersection position based on the direction of
entry into and turning direction at the intersection. Thus,
for example, compared with the case where the same
intersection position is registered irrespective of the
direction of entry and turning direction, it is possible to
improve the accuracy of position-information correction after
passing through the intersection. Accordingly, for example,
in the case where a charging position is set ahead of the exit
of the intersection, it is possible to quickly detect that the
charging position has been passed through. This makes it
possible to immediately notify the driver that the charging
position has been passed through.
{0008}
In the above apparatus for vehicle, in a case where the
angle made by an advancing direction at a second predetermined
time before and a current advancing direction, the second
predetermined time being longer than the first predetermined
time, has reached a second predetermined angle, the second
predetermined angle being greater than the first predetermined
angle, the detecting means may detect, as a reference
position, the position of the moving object where the moving
object is at the firsr predetermined angle relative to the
advancing direction at the second predetermined time before
based on a traveling history from the second predetermined
5
time before to a current time.
{0009}
This makes it possible to reliably detect that the moving
object has turned at the intersection, while excluding the
case where the moving object has passed straight through the
intersection in a meandering fashion, etc.
{0010}
The above apparatus for vehicle may further include an
angular-velocity sensor, and the detecting means may detect a
traveling angle by using an integral value of values measured
by the angular-velocity sensor.
{0011}
By detecting the traveling angle by using the angularvelocity
sensor, it becomes possible to readily detect the
traveling angle while maintaining the desired accuracy.
{0012}
In the above apparatus for vehicle, the correcting means
may include a correcting-amount calculating means for
calculating an offset vector for making the reference
detection position detected by the detecting means coincide
with the coordinates of the intersection position obtained by
the intersection-position obtaining means; and a position
correcting means for correcting, by using the offset vector,
the position information of the moving object obtained by the
position-information obtaining means.
6
{0013}
Since the position information is corrected by using the
offset vector, in the case where a uniform offset is included
in the position information obtained by the positioninformation
obtaining means, it is possible to effectively
remove this offset error.
{0014}
In the above apparatus for vehicle, the position
correcting means may correct the offset vector by multiplying
the offset vector by a weighting coefficient that gradually
decreases to zero as time passes, and the position correcting
means may correct the position information of the moving
object by adding the corrected offset vector to the position
information of the moving object obtained by the positioninformation
obtaining means.
{0015}
Since the offset vector is gradually decreased to zero,
it is possible to gradually shift to position information
detection by the position-information obtaining means.
{0016}
In the above apparatus for vehicle, the positioninformation
obtaining means may include a GPS unit and a dead
reckoning means, the correcting means may execute correction
for making the reference detection position coincide with the
position coordinates of the intersection position, and in a
7
case where the correcting means has correcced the reference
detection position, the position-information obtaining means
may adopt a position detected by the dead reckoning means with
reference to the intersection position as the position
information of the moving object and then switch to adopt a
position detected by the GPS unit.
{0017}
Since the GPS unit and the dead reckoning means are used,
and the dead reckoning means is used during periods in which
higher accuracy is attained with the result of detection by
the dead reckoning means while switching to the GPS unit
during periods in which a large error is involved in the
position detection by the dead reckoning means, it is possible
to execute position detection by using an optimal position
detecting means in accordance with the period. This makes it
possible to improve the accuracy of position-information
detection.
{0018}
In the above apparatus for vehicle, the positioninformation
obtaining means the position-information obtaining
means may include a GPS unit and a dead reckoning means and
may obtain the position information of the moving object by
calculating a weighted average of the position information
obtained by the dead reckoning means and the position
information obtained by the GPS unit, and in a case where the
8
correcting means has corrected the reference detection
position, a large weight may be used for the dead reckoning
means immediately after the correction, and a weight for the
GPS unit may be gradually increased as time passes.
{0019}
Accordingly, it becomes possible to execute position
detection by using an optimal position detecting means in
accordance with the period and to gradually shift from the
position detection by the dead reckoning means to the position
detection by the GPS unit. This makes it possible to maintain
the continuity of detected positions.
{0020}
In the above apparatus for vehicle, information obtained
by the GPS unit may be used regarding velocity information
when the dead reckoning means obtains position information.
{0021}
This makes it possible to overcome the disadvantage of
error accumulation with the dead reckoning means.
{0022}
The above apparatus for vehicle may further include an
output means for outputting the position information of the
moving object obtained by the position-information obtaining
means and for outputting corrected position information of the
moving object during a period in which the position
information of the moving object is being corrected by the
9
correcting means; and a map matching means for identifying a
position of the moving object on a map by using the position
information of the moving object output from the output means,
the map matching means having map information in which roads
are configured of multiple links and each of the links has
unique identification information and position information
assigned thereto.
{0023}
With this configuration, it becomes possible to improve
the accuracy of map matching.
{0024}
In the above apparatus for vehicle, together with the
coordinates of each intersection position in the intersection
information, the identification information of a link that
exists ahead of a turn at the relevant intersection may be
registered, and the output means may output the identification
information of the link together with the position information
of the moving object.
{0025}
By outputting the link ID of a link that the moving
object, having passed through an intersection, enters next, as
described above, it becomes possible for the map matching
means to uniquely identify the link.
{0026}
A second aspect of the present invention is a position
10
correcting method for an apparatus for vehicle, wherein
intersection information is prepared in advance, in which, for
at least one intersection, the coordinates of intersection
positions are registered in association with combinations of a
direction of entry into and a turning direction at the
intersection, the position correcting method including a
position-information obtaining step of obtaining position
information of a moving object; a detecting step of detecting,
as a reference detection position, the position of the moving
object at the time when an angle made by an advancing
direction at a first predetermined time before and a current
advancing direction reached a first predetermined angle in an
intersection region set for each intersection; an
intersection-position obtaining step of obtaining, from the
intersection information, the coordinates of a relevant
intersection position based on a direction of entry of the
moving object into the intersection region and a turning
direction of the moving object in the intersection region; and
a correcting step of correcting the position information of
the moving object obtained in the position-information
obtaining step by using the position coordinates of the
intersection position obtained in the intersection-position
obtaining step and the reference detection position detected
in the detecting step.
{0027}
11
A third aspect of the present invention is a position
correcting program for an apparatus for vehicle, wherein
intersection information is stored in advance, in which, for
at least one intersection, the coordinates of intersection
positions are registered in association with combinations of a
direction of entry into and a turning direction at the
intersection, the position correcting program causing a
computer to execute position-information obtaining processing
for obtaining position information of a moving object;
detection processing for detecting, as a reference detection
position, the position of the moving object at the time when
an angle made by an advancing direction at a first
predetermined time before and a current advancing direction
reached a first predetermined angle in an intersection region
set for each intersection; intersection-position obtaining
processing for obtaining, from the intersection information,
the coordinates of a relevant intersection position based on a
direction of entry of the moving object into the intersection
region and a turning direction of the moving object in the
intersection region; and correction processing for correcting
the position information of the moving object obtained in the
position-information obtaining processing by using the
position coordinates of the intersection position obtained in
the intersection-position obtaining processing and the
reference detection position detected in the detection
12
processing.
{Advantageous Effects of Invention}
{0028}
According to the present invention, an advantage is
afforded in that, in the case where a charging position has
been set at a position ahead of an intersection, it is
possible to reduce a time delay involved in a notification of
passage through the charging position.
{Brief Description of Drawings}
{0029}
{Fig. 1}
Fig. 1 is a diagram showing a functional block diagram of
an apparatus for vehicle according to an embodiment of the
present invention.
{Fig. 2}
Fig. 2 is a diagram for explaining map information
according to the embodiment of the present invention.
{Fig. 3}
Fig. 3 is a diagram for explaining intersection positions
that are registered in intersection information.
{Fig. 4}
Fig. 4 is a diagram for explaining the detection of a
turn at an intersection by a detecting unit.
{Fig. 5}
Fig. 5 is a diagram for explaining an intersection
13
region.
{Fig. 6}
Fig. 6 is a graph for explaining a method of detecting a
turn and a method of detecting a reference detection position
according to a second method of the detecting unit, showing an
example of a history of angular-velocity integral values in
the case of a right turn.
{Fig. 7}
Fig. 7 is a graph for explaining a method of detecting a
turn and a method of detecting a reference detection position
according to the second method of the detecting unit, showing
an example of a history of angular-velocity integral values in
the case of a left turn.
{Fig. 8}
Fig. 8 is a graph for explaining a method of detecting a
reference detection position according to a third method of
the detecting unit, showing an example of a history of
angular-velocity integral values in the case of a right turn.
{Fig. 9}
Fig. 9 is a graph for explaining a method of detecting a
reference detection position according to the third method of
the detecting unit, showing an example of a history of
angular-velocity integral values in the case of a left turn.
{Fig. 10}
Fig. 10 is a diagram for explaining a direction of entry
14
of a moving obJect into an intersection region and a turning
direction of the moving object in the intersection region.
{Fig. ll}
Fig. 11 is a diagram for explaining a direction of entry
of the moving object into an intersection region and a turning
direction of the moving object in the intersection region.
{Fig. 12}
Fig. 12 is a diagram for explaining a direction of entry
of the moving object into an intersection region and a turning
direction of the moving object in the intersection region.
{Fig. 13}
Fig. 13 is a diagram for explaining a direction of entry
of the moving object into an intersection region and a turning
direction of the moving object in the intersection region.
{Fig. 14}
Fig. 14 is a diagram for explaining position-information
correction.
{Fig. 15}
Fig. 15 is a graph showing an example of a weighting
coefficient function.
{Fig. 16}
Fig. 16 is a diagram for explaining another example of
position-information correction.
{Fig. 17}
Fig. 17 is a graph showing an example of a we~ghting
15
coefficient function.
{Fig. 18}
Fig. 18 is a diagram for explaining another example of
position-information correction.
{Description of Embodiments}
{0030}
An embodiment of an apparatus for vehicle and a position
correcting method therefor according to the present invention
will be described below with reference to the drawings.
The apparatus for vehicle according to this embodiment is
widely used for road pricing. For example, the apparatus for
vehicle is applied to a pricing scheme in which a fixed toll
is charged when a toll road has been passed through, a pricing
scheme in which a toll corresponding to the distance travelled
in a predetermined charging area is charged, etc. The
apparatus for vehicle can be applied to both the case where a
toll to be collected is determined or charged upon entry into
a charging area or a toll road and the case where a toll to be
collected is determined or charged upon exit from a charging
area or a toll road.
{0031}
Fig. 1 is a diagram showing a functional block diagram of
an apparatus for vehicle 1 according to an embodiment of the
present invention. For example, the apparatus for vehicle 1
has a computer installed therein, and the functions of the
16
individual components described below are realized by hardware
corresponding to the functions or by a computational
processing unit executing programs (a position correcting
program, etc.) recorded on a computer-readable recording
medium.
As shown in Fig. 1, the apparatus for vehicle 1 includes
a positioning unit 10 that outputs position information of a
moving object, a map matching unit 30, and a charging
processing unit 40.
{0032}
The positioning unit 10 includes, as its main components,
a position-information obtaining unit 11, an intersectioninformation
storage unit 12, a detecting unit 13, an
intersection-position obtaining unit 14, a correcting unit 15,
and an output unit 16.
The position-information obtaining unit 11 obtains
position information of the moving object. The positioninformation
obtaining unit 11 includes a GPS unit 111 and a
dead reckoning unit 112. The dead reckoning unit 112
identifies the advancing direction of and the distance
travelled by the moving obJect by using values measured by onboard
sensors and thereby detects the current position.
Examples of the on-board sensors include a gyro, an
acceleration sensor, and a velocity sensor.
{0033}
17
The position-information obtaining unit 11 obtains
position information of the moving object, for example, by
executing processing for combining (e.g., calculating a
weighted average of) a position output from the GPS unit 111
and a position output from the dead reckoning unit 112. For
example, the position-information obtaining unit 11 obtains
position information of the moving object by using equation
(1) given below.
{0034)
Position information of the moving object = w x Position
output from the GPS unit + (1 - w) x Position output from the
dead reckoning unit (1)
{0035)
In equation (1), w denotes a weighting coefficient that
varies dynamically within a range from 0 to 1.0. For example,
in a place where it is possible to obtain a position by means
of the GPS unit 111, the weighting coefficient w is set to be
a relatively large value. On the other hand, in a place where
it is impossible or difficult to obtain a position by means of
the GPS unit 111, for example, in a tunnel or between tall
buildings, the weighting coefficient w is set to be zero or a
value close to zero. More specifically, the GPS unit 111
outputs, together with the positioning result at a certain
time, the standard deviation s of the error thereof. The
standard deviation s takes on a relatively small value in a
18
place where the reception conditions of the GPS unit 111 are
good. On the other hand, the standard deviation s takes on a
relatively large value in a place where the reception
conditions are poor. For example, the position-information
obtaining unit 11 is provided in advance with a formula (e.g.,
w ~ 1 I s) for calculating the weighting coefficient w, which
includes the standard deviation s as a parameter. The
position-information obtaining unit 11 calculates the
weighting coefficient w by substituting the standard deviation
s output from the GPS unit 111 into this formula. As
described earlier, the value of w is restricted within the
range from 0 to 1.0.
{0036}
The intersection-information storage unit 12 stores
intersection information for at least one intersection, in
which the coordinates (latitude and longitude) of different
intersection positions are registered for individual
combinations of a direction of entry into and a turning
direction at the intersection. Furthermore, an intersection
region R (see Fig. 4), which will be described later, is set
for each intersection, and information about this intersection
region R is also included in the intersection information.
{0037}
For example, as shown in Fig. 3, at a broad intersection,
etc., the traveling route during a turn at the intersection
19
often varies depending on the direction of entry into the
intersection and the turning direction at the intersection (a
right turn, a left turn, etc.). Thus, it is preferred to set
a reference position of an intersection in accordance with the
direction of entry and the turning direction. This is because
the accuracy of position-information correction at an
intersection is likely to be degraded if a reference position
of an intersection is set uniformly (e.g., at the center of
the intersection) irrespective of the direction of entry and
the turning direction.
(0038}
In this embodiment, for example, as shown in Fig. 3, the
coordinates of an intersection position A are registered for
the case where the direction of entry is the South and the
turning direction is a left turn, whereas the coordinates of
an intersection position B are registered for the case where
the direction of entry is the South and the turning direction
is a right turn.
The directions of entry and turning directions associated
with the coordinates of intersection positions should
preferably be set with some margins. This is because the
direction of entry conceivably varies depending on the moving
object when a road is broad and because the position detection
and direction detection by the GPS unit 111 and the dead
reckoning unit 112 involve errors.
20
{0039}
As shown in Fig. 4, the detecting unit 13 determines that
the moving object has turned at an intersection when the angle
8 made by the advancing direction at a first predetermined
time T1 [seconds] before and the current advancing direction
{hereinafter referred to as the ''turning angle 8"} in the
intersection region R set for each intersection has reached a
first predetermined angle 8 1 [deg] and detects the position of
the moving object at that time as a reference detection
position.
Here, the first predetermined time T1 [seconds] and the
first predetermined angle 8 1 are values that may be set
arbitrarily. For example, the first predetermined time T1
[seconds] is set between 5 [seconds] and 20 [seconds], and the
first predetermined angle 8 1 is set between 40 [deg] and 65
[deg]. Obviously, these values may be set outside these
ranges depending on the case.
For example, the first predetermined time T1 [seconds] is
set to be 15 [seconds], and the first predetermined angle 81
is set to be 45 [deg].
{ 0 0 4 0 }
Alternatively, the detecting unit 13 may determine that
the moving object has curned at an intersection when the angle
8 made by the advancing direction at a second predetermined
time T2 [seconds] before, which is earlier than the first
21
predetermined time T1 [seconds] before, and the current
advancing direction has reached a second predetermined angle
82 [deg], which is greater than the first predetermined angle
81 [deg], in the intersection region R set for each
intersection and then may detect the position of the moving
object at the time when the turning angle 8 reached the first
predetermined angle 81 [deg] as a reference detection position
based on the traveling route from the present back to the
second predetermined time T2 [seconds] before.
{0041}
Here, the second predetermined time T2 [seconds] and the
second predetermined angle 82 are values that may be set
arbitrarily. For example, the second predetermined time T2
[seconds] is set between 25 [seconds] and 35 [seconds], and
the second predetermined angle 82 is set between 80 [deg] and
95 [deg]. Obviously, these values may be set outside these
ranges depending on the case.
{0042}
As shown in Fig. 5, for example, the intersection region
R is set so as to have a radius x [m] about the center 0 of
each intersection. Here, the radius x [m] is a value that may
be set arbitrarily. Although the intersection regions R
should preferably be set such that adjacent ones do not
overlap each other, in the case where there is an overlap, it
is determined that the moving object has turned a nearer
22
intersection.
{0043}
Examples of the methods of detecting a turn at an
intersection and detecting the above-described reference
detection position by the detecting unit 13 include the
following methods.
[First method]
For example, the detecting unit 13 monitors the integral
value of an angular-velocity sensor provided in the moving
object, determines that the moving object has turned at an
intersection when the integral value of the angular-velocity
sensor from the first predetermined time T1 [seconds] before
to the current time has reached a value corresponding to the
first predetermined angle 81 [deg], and detects the position
of the moving object at that time as a reference detection
position.
{0044}
[Second method]
As shown in Fig. 6, the detecting unit 13 monitors the
integral value from the angular-velocity sensor from the
second predetermined time T2 [seconds] before to the current
time, the second predetermined time T2 [seconds] being longer
than the first predetermined time T1 [seconds], and determines
that the moving object has turned at an intersection in the
case where it has detected that the angular-velocity integral
23
value from the second predetermined time T2 [seconds] before
has reached a value Z7 corresponding to the second
predetermined angle 82 , which is greater than the first
predetermined angle 8 1 • Then, the detecting unit 13 detects,
as a reference detection position, the position of the moving
object at the time when the angular-velocity integral value
reached a value Z1 corresponding to the first predetermined
angle 8 1 (the position of the moving object at the time
indicated by a double circle in Fig. 6) based on the history
of the angular-velocity integral value from the second
predetermined time T2 [seconds] before to the current time.
{0045}
Figs. 6 and 7 shows examples in which the first
predetermined time T1 [seconds] is set to be 15 [seconds], the
first predetermined angle 8 1 is set to be 45 [deg], the second
predetermined time T2 [seconds] is set to be 30 [seconds], and
the second predetermined angle 82 is set to be 90 [deg]. Fig.
6 shows the history of the angular-velocity integral value Z
in the case of a right turn, and Fig. 7 shows the history of
the angular-velocity integral value Z in the case of a left
turn. It is possible to distinguish between a right turn and
a left turn by distinguishing whether the integral value is
positive or negative.
{0046}
The second predetermined angle 82 should preferably be
24
set to be an angle that is sufficiently large to ascertain
that the moving object has turned at an intersection (e.g., 90
[deg]) More specifically, with the first method described
above, for example, in the case where the traveling direction
of the moving object is considerably changed to detour around
an automobile stopped at an intersection and the moving object
passes straight through the intersection in a meandering
fashion, there is a possibility of wrongly ascertaining that
the moving object has turned at the intersection. In
contrast, with the second method, since it is determined that
the moving object has turned at an intersection when the
turning angle 8 has reached the second predetermined angle 82 ,
it is possible to exclude the case where the moving object has
passed straight through the intersection in a meandering
fashion.
{0047}
[Third method]
The detecting unit 13 detects the turning angle 8 based
on, for example, a result of measurement by a gyro, a result
of CPS positioning, a difference between the rotation speeds
of right and left wheels, a handle steering angle, etc. and
determines that the moving object has turned at an
interseccion when the turning angle 8 has reached the first
predetermined angle 81 or the second predetermined angle 82 .
Furthermore, as for the detection of a reference
25
detection position in this case, as shown in Fig. 8, the
detecting unit 13 monitors the values measured by the angularvelocity
sensor since the moving object entered the
intersection region R and detects, as a reference detection
position, the position of the moving object at the time when
the value measured by the angular-velocity sensor exhibited a
peak value. Fig. 8 shows the history of the angular velocity
in the case of a right turn, and Fig. 9 shows the history of
the angular velocity in the case of a left turn. It is
possible to distinguish between a right turn and a left turn
by distinguishing whether the angular velocity is positive or
negative.
{0048)
The intersection-position obtaining unit 14 obtains the
coordinates of the relevant intersection position from the
intersection information stored in the intersectioninformation
storage unit 14 based on the direction of entry of
the moving object into the intersection region R and the
turning direction thereof in the intersection region.
For example, as shown in Figs. 10 and 11, in the case
where the moving object enters an intersection from the South
direction and turns right, the intersection-position obtaining
unit 14 obtains, from the intersection information, the
coordinates of the intersection position for which the South
direction is registered as the direction of entry and a right
26
turn is set as the turning direction in the intersection
region. The deviation of the traveling route from the road in
Fig. 10 indicates a large error in GPS positioning.
{0049}
As another example, as shown in Fig. 12, in the case
where the moving object enters an intersection from the South
direction and turns left, the intersection-position obtaining
unit 14 obtains, from the intersection information, the
coordinates of the intersection position for which the South
direction is registered as the direction of entry and a left
turn is set as the turning direction in the intersection
region.
As another example, as shown in Fig. 13, in the case
where the moving object enters an intersection from the East
direction and turns right, the intersection-position obtaining
unit 14 obtains, from the intersection information, the
coordinates of the intersection position for which the East
direction is registered as the direction of entry and a right
turn is set as the turning direction in the intersection
region.
As described above, the coordinates of individually
different intersection positions are obtained from the
intersection information in accordance with the directions of
entry into the intersection region and the turning directions
in the intersection region.
27
{0050)
The correcting unit 15 corrects the position information
output from the position-information obtaining unit 11 by
using the position coordinates of the intersection position
obtained by the intersection-position obtaining unit 14 and
the reference detection position detected by the detecting
unit 13.
Specifically, the correcting unit 15 includes a
correcting-amount calculating unit 151 and a position
correcting unit 152. As shown in Fig. 14, the correctingamount
calculating unit 151 calculates an offset vector Vt for
making the reference detection position Pl detected by the
detecting unit 13 coincide with the coordinates PO of the
intersection position obtained by the intersection-position
obtaining unit 14.
The position correcting unit 152, by using the offset
vector Vt, corrects the position information of the moving
object obtained by the position-information obtaining unit 11.
For example, the position correcting unit 152 corrects the
position information by adding the offset vector Vt to the
position information of the moving object obtained by the
position-information obtaining unit 11.
{0051)
More specifically, when the correcting-amount calculating
unit 151 has calculated the offset vector Vt for making the
28
reference detection position P1 coincide with the coordinates
PO of the intersection position, the position correcting unit
152 corrects the offset vector Vt by multiplying the offset
vector Vt by a weighting coefficient a that gradually
decreases to zero as time passes.
For example, as shown in Fig. 15, the position correcting
unit 152 has a function in which the weighting coefficient a
is 1 during a predetermined period (the period until time T3
in Fig. 15) from the time when the reference detection
position P1 is detected by the GPS unit 111 (hereinafter
referred to as the "correction start time'') and then the
weighting coefficient a decreases to zero at a constant rate
during a predetermined period (the period from time T3 to time
T4 in Fig. 15).
{0052}
The position correcting unit 152, by using this function,
obtains the weighting coefficient a corresponding to the time
elapsed since the correction start time and corrects the
offset vector Vt by multiplying the offset vector Vt by the
obtained weighting coefficient a. Then, the position
correcting unit 152 corrects the position information of the
moving object obtained by the position-information obtaining
unit 11 by adding the corrected offset vector to the position
information of the moving object.
Thus, as shown in Fig. 14, the values of the corrected
29
position information become closer to those of the position
information obtained by the position-information obtaining
unit 11 as the position becomes farther from the vicinity of
an intersection.
{0053}
The output unit 16 outputs the corrected position
information to the map matching unit 30 in the case where the
position has been corrected by the correcting unit 15, whereas
the output unit 16 outputs the position information output
from the position-information obtaining unit 11 to the map
matching unit 30 in the case where the position has not been
corrected by the correcting unit 15. Thus, the output unit 16
outputs the position information received from the correcting
unit 15 until the weighting coefficient a becomes zero,
whereas the output unit 16 outputs the position information of
the moving object output from the position-information
obtaining unit 11 after the weighting coefficient a becomes
zero.
{0054}
The map matching unit 30 has map information in which
roads are constituted of multiple links and each link has
unique identification information (link ID) assigned thereto.
The map matching unit 30 identifies a link that is closest to
the current position of the moving object by using the
position information of the moving object output from the
30
positioning unit 10.
{0055}
In the map information, for example, as shown in Fig. 2,
roads are virtually divided into multiple links, and each of
the links has an associated link ID, which serves as
identification information unique to the link, and associated
position information (e.g., latitude and longitude). In the
map information, nodes (see black dots in the figure) are set
at road intersections and branches, and basically the line
segments between nodes are defined as links. Alternatively,
the links that have been set as described above may be further
divided into smaller segments to configure multiple links
between nodes. In Fig. 2, 44885, 43492, 31847, etc. represent
individual link IDs.
The map matching unit 30 identifies the current position
of the moving object on a road by identifying, from the map
information, the link ID corresponding to the position
information of the moving object output from the positioning
unit 10.
{0056}
The charging processing unit 40 has a database (not
shown) in which link IDs for which positions related to
charging have been set are registered. The charging
processing unit 40 executes processing related to charging in
the case where a link ID registered in the database is input
31
from the map matching unit 30. Examples of the processing
related to charging include processing for notifying the
driver of the start of charging or the fixing of a toll to be
collected, processing for starting charging, and processing
for fixing a toll to be collected.
{0057}
Next, the operation of the apparatus for vehicle 1
according to this embodiment will be described.
First, the position-information obtaining unit 11
sequentially obtains position information of the moving object
according to equation (1), given earlier, by using the
position detected by the GPS unit 111 and the position
detected by the dead reckoning unit 112 and outputs the
position information to each of the detecting unit 13, the
intersection-position obtaining unit 14, the correcting unit
15, and the output unit 16.
The detecting unit 13 determines whether the moving
object has entered any intersection region R or not based on
the intersection regions R registered in the intersection
information stored in the intersection-information storage
unit 12 and the position information received from the
position-information obtaining unit 11. In the case where it
is determined, as a result, that the moving object has entered
an intersection region R, the detecting unit 13 determines
whether the moving object has turned the relevant intersection
32
or not. Then, in the case where it is determined that the
moving object has turned at the intersection, the detecting
unit 13 detects, as a reference detection position, the
position of the moving object at the time when the angle 8
made by the advancing direction at the first predetermined
time T1 [seconds] earlier and the current advancing direction
(hereinafter referred to as the ''turning angle 8'') reached the
first predetermined angle 81 [deg] in the relevant
intersection region R.
The methods for carrying out the above determination and
detection of the reference detection position have been
described earlier.
The detecting unit 13 reports the direction of entry at
the time of entry into the intersection region R and the
turning direction in the intersection region R to the
intersection-position obtaining unit 14 and outputs the
reference detection position to the correcting unit 15.
(0058)
Based on the direction of entry into the intersection
region R and the turning direction in the intersection region
R of the moving object, reported from the detecting unit 13,
the intersection-position obtaining unit 14 obtains the
coordinates of the relevant intersection position from the
intersection information stored in the intersectioninformation
storage unit 12 and outputs the coordinates of the
33
intersection position to the correcting unit 15.
{0059}
The correcting-amount calculating unit 151 of the
correcting unit 15 calculates an offset vector Vt for making
the reference detection position detected by the detecting
unit 13 coincide with the position coordinates of the
intersection position obtained by the intersection-position
obtaining unit 14 (see Fig. 14) and outputs the offset vector
Vt to the position correcting unit 152.
The position correcting unit 152 adds the result of
multiplying the offset vector Vt by a weighting coefficient a
obtained from a function shown in Fig. 15 to the position
information of the moving object received from the positioninformation
obtaining unit 11, thereby correcting the position
information of the moving object, and outputs the corrected
position information to the output unit 16.
{0060}
During periods in which corrected position information is
being input from the correcting unit 15, the output unit 16
outputs the corrected position information to the map matching
unit 30. On the other hand, during periods in which corrected
position information is not being input from the correcting
unit 15, the output unit 16 outputs the position information
output from the position-information obtaining unit 11 to the
map matching unit 30.
34
(0061}
The map matching unit 30 obtains a link ID corresponding
to the position information input from the output unit 16 from
map information and outputs the link ID to the charging
processing unit 40.
The charging processing unit 40 searches a database (not
shown) by using the link ID input from the map matching unit
30 as a key and, for example, executes charging processing in
the case where the link ID input from the map matching unit 30
is registered in the database. For example, in the case of a
link ID that requires a notification about charging, the
charging processing unit 40 sends a notification about
charging to the driver.
(0062}
As described above, with the apparatus for vehicle 1 and
the position correcting method therefor according to this
embodiment, for each intersection, the coordinates of
intersection positions that serve as references are registered
in association with directions of entry into the intersection
and turning directions at the intersection. When the moving
object passes through an intersection, the position
information is corrected by using the coordinates of an
appropriate intersection position based on the direction of
entry into and turning direction at the intersection. Thus,
for example, compared with the case where the same
35
intersection position is registered irrespective of the
direction of entry and turning direction, it is possible to
improve the accuracy of position-information correction after
passing through the intersection. Accordingly, for example,
in the case where a charging position is set ahead of the exit
of the intersection, it is possible to quickly detect that the
charging position has been passed through. This makes it
possible to immediately notify the driver that the charging
position has been passed through.
{0063}
With the apparatus for vehicle 1 and the position
correcting method therefor according to the embodiment
described above, after an intersection is passed, the position
information is corrected by adding an offset vector Vt in
accordance with time to the result of positioning by the GPS
unit 111. Although this method is effective when
substantially the same offset is constantly applied, the
detection error of the GPS unit 111 may change as time passes.
In this case, an expected level of accuracy may not
necessarily be attained with the above-described position
detection based on the offset vector Vt. Thus, the following
correcting method may be employed instead of the abovedescribed
correcting method.
{0064}
For example, as shown in Fig. 16, after the reference
36
detection position detected by the detecting unit 13 is made
to coincide with the position coordinates of the intersection
position, when calculating the position information of the
moving object, the weighting coefficient w in equation (1)
given earlier may be set to zero to switch to position
detection by the dead reckoning unit 112 with reference to the
position coordinates of the intersection position.
Accordingly, the result of positioning by the GPS unit 111 is
not reflected, and the position information detected by the
dead reckoning unit 112 is output from the positioninformation
obtaining unit 11 to the output unit 16 as the
position information of the moving object and is then output
to the map matching unit 30. In this case, after the
weighting coefficient a of the offset vector Vt becomes zero,
for example, the weighting coefficient w is determined
according to the earlier-described formula based on the
standard deviation s.
{0065}
Alternatively, instead of completely switching between
the obtaining of position information by the dead reckoning
unit 112 and the obtaining of position information by the GPS
unit 111 as described above, for example, as shown ln Fig. 17,
a function with which the weighting coefficient w increases
gradually may be prepared in advance, and the position
information of the moving object may be obtained by using this
37
function.
{0066}
Accordingly, at the correction start time, the position
information of the moving object in which the result of
detection by the dead reckoning unit 112 is reflected more
strongly is output to the output unit 16, and as time passes,
the position information of the moving object in which the
result of detection by the GPS unit 111 is reflected more
strongly is output to the output unit 16.
For example, the position detection by the dead reckoning
unit 112 is executed by integrating the values measured by
sensors. Thus, although a certain level of accuracy can be
expected at the beginning, errors increase as time passes,
which results in the problem of degraded detection accuracy.
Therefore, the dead reckoning unit 112 is mainly used during
an initial period of correction, in which the detection
accuracy of the dead reckoning unit 112 is expected to be
higher than that of the GPS unit 111, then the weight of the
position detection by the GPS unit 111 is gradually increased,
and finally, the operation is completely switched to position
detection by the GPS unit 111. This makes it possible to
employ an appropriate position detecting means in accordance
with the elapse of time, which makes it possible to further
improve the accuracy of position detection.
{0067}
38
Alternatively, as a modification of the above-described
method, as shown in Fig. 18, the result of posi~ioning by the
GPS unit 111 may be used for velocity detection by the dead
reckoning unit 112. For example, integration by an
acceleration sensor is sometimes used for velocity, and in
such cases, there is a concern that the accuracy of velocity
detection will gradually degrade due to the accumulation of
errors as described above. Thus, for velocity detection, in
which errors accumulate, the result of positioning by the GPS
unit 111 may be used to avoid an increase in errors due to
integration.
{0068}
Furthermore, although only the position information is
output from the positioning unit 10 to the map matching unit
30 in this embodiment, a link ID that exists ahead of a turn
at the intersection may be output together with the position
information. By outputting the link ID of the link that the
moving object enters next after passing through the
intersection, it becomes possible for the map matching unit 30
to uniquely identify the link.
In order to attach such a link ID, for example, in
association with the coordinates of each intersection
position, a link ID that exists ahead of a turn at the
intersection should be registered.
{0069}
39
Although the embodiment of the present invention has been
described above in detail with reference to the drawings,
specific configurations are not limited to the embodiment, and
the present invention encompasses design modifications, etc.
that do not depart from the scope thereof.
{Reference Signs List}
{0070}
1 Apparatus for vehicle
10 Positioning unit
11 Position-information obtaining unit
12 Intersection-information storage unit
13 Detecting unit
14 Intersection-position obtaining unit
15 Correcting unit
16 Output unit
30 Map matching unit
40 Charge processing unit
111 GPS unit
112 Dead reckoning unit
151 Correcting-amount calculating unit
152 Position correcting unit

{CLAIMS}
{Claim 1}
40
An apparatus for vehicle comprising:
a position-information obtaining means for obtaining
position information of a moving object;
an intersection-information storage means for storing
intersection information in which, for at least one
intersection, the coordinates of intersection positions are
registered in association with combinations of a direction of
entry into and a turning direction at the intersection;
a detecting means for detecting, as a reference detection
position, a position of the moving object at the time when an
angle made by an advancing direction at a first predetermined
time before and a current advancing direction reached a first
predetermined angle in an intersection region set for each
intersection;
an intersection-position obtaining means for obtaining,
from the intersection information, the coordinates of a
relevant intersection position based on a direction of entry
of the moving object into the intersection region and a
turning direction of the moving object in the intersection
region; and
a correcting means for correcting the position
information of the moving object obtained by the positioninformation
obta~ning means by using the position coordinates
41
of the intersection position obtained by the intersectionposition
obtaining means and the reference detection position
detected by the detecting means.
{Claim 2}
The apparatus for vehicle according to Claim 1, wherein,
in a case where an angle made by an advancing direction at a
second predetermined time before and a current advancing
direction, the second predetermined time being longer than the
first predetermined time, has reached a second predetermined
angle, the second predetermined angle being greater than the
first predetermined angle, the detecting means detects, as a
reference position, the position of the moving object where
the moving object is at the first predetermined angle relative
to the advancing direction at the second predetermined time
before based on a traveling history from the second
predetermined time before to a current time.
{Claim 3}
The apparatus for vehicle according to Claim 1 or 2,
further comprising an angular-velocity sensor,
wherein the detecting means detects a traveling angle by
using an integral value of values measured by the angularvelocity
sensor.
{Claim 4}
The apparatus for vehicle according to any one of Claims
1 to 3,
42
wherein the correcting means includes:
a correcting-amount calculating means for calculating an
offset vector for making the reference detection position
detected by the detecting means coincide with the coordinates
of the intersection position obtained by the intersectionposition
obtaining means; and
a position correcting means for correcting, by using the
offset vector, the position information of the movlng object
obtained by the position-information obtaining means.
{Claim 5}
The apparatus for vehicle according to Claim 4, wherein
the position correcting means corrects the offset vector by
multiplying the offset vector by a weighting coefficient that
gradually decreases to zero as time passes, and the position
correcting means corrects the position information of the
moving object by adding the corrected offset vector to the
position information of the moving object obtained by the
position-information obtaining means.
{Claim 6}
The apparatus for vehicle according to any one of Claims
1 to 5,
wherein the position-information obtaining means
includes:
a GPS unit; and
a dead reckoning means,
43
wherein the correcting means executes correction for
making the reference detection position coincide with the
position coordinates of the intersection position, and
wherein, in a case where the correcting means has
corrected the reference detection position, the positioninformation
obtaining means adopts a position detected by the
dead reckoning means with reference to the intersection
position as the position information of the moving object and
then switches to adopt a position detected by the GPS unit.
{Claim 7}
The apparatus for vehicle according to any one of Claims
1 to 5,
wherein the position-information obtaining means includes
a GPS unit and a dead reckoning means and obtains the position
information of the moving object by calculating a weighted
average of the position information obtained by the dead
reckoning means and the position information obtained by the
GPS unit, and
wherein, in a case where the correcting means has
corrected the reference detection position, a large weight is
used for the dead reckoning means immediately after the
correction, and a weight for the GPS unit is gradually
increased as time passes.
{Claim 8}
The apparatus for vehicle according to Claim 6 or 7,
44
wherein information obtained by the GPS unit is used regarding
velocity information when the dead reckoning means obtains
position information.
{Claim 9}
The apparatus for vehicle according to any one of Claims
1 to 8, further comprising:
an output means for outputting the position information
of the moving object obtained by the position-information
obtaining means and for outputting corrected position
information of the moving object during a period in which the
position information of the moving object is being corrected
by the correcting means; and
a map matching means for identifying a position of the
moving object on a map by using the position information of
the moving object output from the output means, the map
matching means having map information in which roads are
configured of multiple links and each of the links has unique
identification information and position information assigned
thereto.
{Claim 10}
The apparatus for vehicle according to Claim 9,
wherein, together with the coordinates of each
intersection position in the intersection information, the
identification information of a link that exists ahead of a
turn at the relevant intersection is registered, and
45
wherein the output means outputs the identification
information of the link together with the position information
of the moving object.
{Claim 11}
A position correcting method for an apparatus for
vehicle, wherein intersection information is prepared in
advance, in which, for at least one intersection, the
coordinates of intersection positions are registered in
association with combinations of a direction of entry into and
a turning direction at the intersection, the position
correcting method comprising:
a position-information obtaining step of obtaining
position information of a moving object;
a detecting step of detecting, as a reference detection
position, the position of the moving object at the time when
an angle made by an advancing direction at a first
predetermined time before and a current advancing direction
reached a first predetermined angle in an intersection region
set for each intersection;
an intersection-position obtaining step of obtaining,
from the intersection information, the coordinates of a
relevant intersection position based on a direction of entry
of the moving object into the intersection region and a
turning direction of the moving object in the intersection
region; and
46
a correcting step of correctjng
of the moving object obtained in he
the position information
position-information
obtaining step by using the posit'on coordinates of the
intersection position obtained in the intersection-position
obtaining step and the reference etection position detected
in the detecting step.
{Claim 12}
A position correcting program for an apparatus for
vehicle, wherein intersection information is stored in
advance, in which, for at least one intersection, the
coordinates of intersection positions are registered in
association with combinations of a direction of entry into and
a turning direction at the intersection, the position
correcting program causing a computer to execute:
position-information obtaining processing for obtaining
position information of a moving object;
detection processing for detecting, as a reference
detection position, the position of the moving object at the
time when an angle made by an advancing direction at a first
predetermined time before and a current advancing direction
reached a first predetermined angle in an intersection region
set for each intersection;
intersection-position obtaining processing for obtaining,
from the intersection information, the coordinates of a
relevant intersection position based on a direction of entry
47
of the moving object into the intersection region and a
turning direction of the moving object in the intersection
region; and
correction processing for correcting the position
information of the moving object obtained in the positioninformation
obtaining processing by using the position
coordinates of the intersection position obtained in the
intersection-position obtaining processing and the reference
detection position detected in the detection processing.