JPH08334367A - System and method for calculating present location - Google Patents

Abstract

PURPOSE: To provide a present location calculating system which can accurately calculate the present location of its own vehicle by reducing the unnatural movement of the present location of the vehicle. CONSTITUTION: A processor 18 gives a first bias value to the reliability of a candidate point obtained from displayed candidate points and, while its own vehicle travels a prescribed distance after passing a branchpoint, gives a second bias value which is smaller than the first bias value to the reliability of another candidate point obtained based on displayed candidate points. The processor 18 compares the reliability of a first candidate for the branchpoint other than the displayed candidate points obtained from the candidate points displayed when the vehicle passes through the branchpoint and the reliability of a second candidate for the branchpoint found from the first candidate point while the vehicle travels the prescribed distance with the reliability of the displayed candidate point to which the second bias value is added and, at the same time, compares the reliability of candidate points other than the candidate for the branchpoint with that of the displayed candidate point to which the first bias value is added.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is mounted on a moving body such as a vehicle and measures the traveling distance and traveling direction of the moving body.
Thus, the present invention relates to a current position calculation system that calculates the current position of the moving body.

[0002]

2. Description of the Related Art Conventionally, in a current position calculation system for calculating the current position of a vehicle traveling on a road, the current position of the vehicle is the traveling direction of the vehicle measured by a direction sensor such as a gyro and a vehicle speed sensor or distance. It is calculated based on the traveling distance of the vehicle measured by the sensor.

The traveling distance of the vehicle is generally measured by measuring the output shaft of the transmission or the rotation speed of the tire, and the distance is a distance that the vehicle travels per rotation of the tire. It is calculated by multiplying by.

Further, in order to correct the error of the current position obtained from the traveling direction and traveling distance of the vehicle as described above, as described in JP-A-63-148115, based on the traveling distance and the direction change amount. The estimated position of the vehicle determined and the amount of error based on the error of the road map are obtained, and the estimated position is registered as the self-position corresponding to all the roads located within the range of the amount of error centered on the estimated position. However, a technique is disclosed in which the correlation coefficient of each of the registered estimated positions for each road is calculated, and the estimated position related to the correlation coefficient indicating that the error for the road is the smallest is the current position.
As described in this publication, to match the road,
There is known a so-called map matching technique for correcting the obtained current position of the vehicle, and this map matching technique can improve the accuracy of the current position calculation.

[0005]

In the current position calculation system for executing map matching using the above-mentioned technique, particularly when a vehicle passes through a branch point, a plurality of estimated positions respectively located on a plurality of roads are estimated. Is calculated,
Further, as the vehicle travels, each correlation coefficient changes, and the road where the estimated position related to the correlation coefficient indicating that the error for the road is the smallest changes every time the correlation coefficient is calculated. There is a case to do. In such a case, the current position displayed on the display device provided in the current position calculation system may appear on a road connected to the branch point at some time after the vehicle has passed through the branch point. On the other hand, at some other time, it may appear on another road, resulting in an unnatural movement of the current position.

[0006] On the other hand, after the vehicle has passed through the branch point, for a while (for example, until a clear difference in the shapes of the roads connected to the branch point appears), the road on which road the vehicle is located. It is often difficult to determine if you are driving.

An object of the present invention is to provide a current position calculation system for calculating a more accurate current position of a vehicle while reducing unnatural movement of the current position of the vehicle displayed on a display device.

[0008]

An object of the present invention is a current position calculation system mounted on a vehicle for calculating the current position of the vehicle, and an azimuth detecting means for detecting a traveling azimuth of the vehicle.
Distance calculating means for calculating the traveling distance of the vehicle, relative displacement obtained based on the traveling direction and the traveling distance, a state where the vehicle is located on any road, or a state where the vehicle is not located on the road A virtual current position generating means for generating a virtual current position expected to be the current position of the vehicle based on the candidate point indicating the current position, and the virtual current position and the road direction included in the road data included in the map data. Candidate point generation means for generating a candidate point indicating that a vehicle exists on the road corresponding to the road data based on the data, and credibility that the vehicle exists at a position on the road corresponding to the candidate point. Reliability calculating means for calculating the reliability indicating
Comparing the reliability of the candidate points, the candidate point having the largest value, the determining means for determining as a display candidate point indicating the current position of the vehicle, the reliability calculating means, based on the display candidate point First bias value adding means for giving a predetermined first bias value to the obtained reliability value of the candidate point, and the display candidate point while the vehicle travels a predetermined distance after passing the branch point. The reliability of the candidate points obtained based on
Second bias value adding means for giving a predetermined second bias value smaller than the bias value of, and the determining means is a candidate point obtained from the display candidate points when the vehicle has passed the branch point. And a first branch candidate point other than the newly obtained display candidate point and one or more second branch candidate points obtained based on the first branch candidate point while the vehicle travels the predetermined distance. And the reliability of the candidate point obtained on the basis of the display candidate point obtained by adding a second bias value to the value of the branch candidate point. A present configured to compare the reliability of a candidate point other than the two branch candidate points with the reliability of the candidate point obtained based on the display candidate point obtained by adding a first bias value to the value. Achieved by the position calculation system.

[0009] In a preferred aspect of the present invention, the determining means sets the reliability of any one of the first branch candidate point and the second branch candidate point and the candidates other than the branch candidate point. The first comparing means for comparing the reliability of the point, the reliability of the candidate point having the largest reliability value obtained by the first comparing means, and the first comparing means according to the candidate point. The second comparison means compares the reliability of the candidate point obtained based on the display candidate point to which the bias value or the second bias value is added.

In a further preferred aspect of the present invention, further, when the vehicle is traveling on a highway, the predetermined distance is given a first distance;
When the vehicle is traveling on a general road, it is provided with a distance giving means for giving a second distance smaller than the first distance.

[0011]

According to the present invention, since the bias value is added to the reliability of the display candidate points, candidate points other than the candidate points obtained based on the display candidate points can be determined as new candidate points. Since the property is reduced by a ratio corresponding to the bias value, it is possible to reduce the possibility that the calculated current position of the vehicle will make an unnatural movement as the vehicle travels.

Further, according to the present invention, the reliability of the candidate points obtained based on the display candidate points is smaller than the first bias value while the vehicle travels a predetermined distance after passing the branch point. Since the sum of the second bias value and the reliability of the branch candidate points are compared, the candidate points other than the branch candidate points are more likely to be determined as the new display candidate points than the branch candidate points. Is more likely to be determined as a new display candidate point. That is, while the vehicle travels a predetermined distance after passing the branch point,
Candidate points other than the display candidate points generated by passing the branch point are relatively likely to be determined as new display candidate points, and as a result, when the vehicle passes the branch point. Even if the obtained display candidate point corresponds to a road other than the road on which the vehicle is traveling, it is possible to more quickly obtain the display candidate point at an appropriate position on the road.

According to a preferred embodiment of the present invention, the first
Comparing means compares the reliability of the branch candidate point with the reliability of other candidate points, and the second comparing means compares the reliability of the candidate point obtained by the first comparing means and the bias value. The reliability of the display candidate points including is compared. Therefore, it is possible to determine an appropriate display candidate point without requiring complicated processing.

[0014]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the configuration of the present position calculating apparatus according to the embodiment of the present invention. As shown in FIG. 1, the present position calculation device 10 includes an angular velocity sensor 11 that detects a change in the heading by detecting the yaw rate of the vehicle, and a direction sensor 12 that detects the heading of the vehicle by detecting the geomagnetism. And a vehicle speed sensor 13 that outputs pulses at time intervals proportional to the rotation of the output shaft of the vehicle transmission.

Further, a display 17 for displaying a map around the current position and a mark indicating the current position, a switch 14 for receiving a command for switching the scale of the map displayed on the display 17 from a user (driver), and digital map data. CD-ROM 15 for storing the
A driver 16 for reading map data from the ROM 15. Further, the controller 18 for controlling the operation of each peripheral device described above is provided. In the present embodiment, the digital map data described above includes road data composed of coordinates indicating the ends of a plurality of line segments,
Alternatively, it includes road width data indicating the road width of the road, a highway flag indicating whether the road is a highway or a general road, and the like.

The controller 18 includes an A / D converter 19 for converting the signal (analog) of the angular velocity sensor 11 into a digital signal, and an A / D converter 20 for converting the signal (analog) of the azimuth sensor 12 into a digital signal. , Vehicle speed sensor 13
A counter 26 that counts the number of pulses output from the device every 0.1 seconds, a parallel I / O 21 that inputs whether or not the switch 14 is pressed, and a DMA (Direct) that transfers the map data read from the CD-ROM 15. Memory Acces
s) It has a controller 22 and a display processor 23 for displaying a map image on the display 17.

The controller 18 further includes a microprocessor 24 and a memory 25. The microprocessor 24 outputs the signal of the angular velocity sensor 11 obtained through the A / D converter 19, the signal of the direction sensor 12 obtained through the A / D converter 20, and the output pulse of the vehicle speed sensor 13 counted by the counter 26. Number, whether or not the switch 14 is pressed through the parallel I / O 21, the map data from the CD-ROM 15 obtained through the DMA controller 22 is accepted, and processing is performed based on those signals,
Calculate the current position of the vehicle and display it
To be displayed on the display 17 via. As shown in FIG. 2, the vehicle position is already displayed on the display 17
This is done by superimposing and displaying an arrow mark etc. on the map displayed in. This allows the user to know the current position of the vehicle on the map. The memory 25 includes a ROM that stores a program or the like that defines the contents of processing (described later) for realizing such an operation, and a RAM that is used as a work area when the microprocessor 24 performs the processing. There is.

The operation of the present position calculation device 10 thus configured will be described below.

The operation of the apparatus 10 is generally as follows: a process for calculating the traveling direction and traveling distance of the vehicle, a process for determining the current position of the vehicle from the calculated traveling direction and distance, and the obtained vehicle position and Since it can be divided into three processes, that is, the process of displaying the azimuth, these processes will be described sequentially.

FIG. 3 illustrates the flow of processing for calculating the traveling direction and traveling distance of the vehicle.

This processing is carried out at a fixed cycle, for example, 100 m.
This is a routine of the microprocessor 24 that is activated and executed for each S.

In this routine, first, the A / D converter 1
The output value of the angular velocity sensor 11 is read from 9 (step 301). Since the azimuth change is output as the output value of the angular velocity sensor 11, only a relative value in the traveling direction of the vehicle can be detected. Therefore, next, the output value of the azimuth sensor 12 including the geomagnetic sensor is read from the A / D converter 20 (step 302), and the absolute azimuth calculated from the output value of the azimuth sensor 12 and the angular velocity sensor 11 output it. The estimated azimuth of the vehicle is determined by using the azimuth change (angular velocity output) (step 303).

This azimuth determination can be performed, for example, for a long time,
When the vehicle speed is low, the error of the angular velocity sensor is large, so
When the vehicle speed is low for a certain period of time or more, the direction of the azimuth sensor is used.

Next, the number of pulses output from the vehicle speed sensor 13 is counted by the counter 26 every 0.1 seconds, and the counted value is read (step 304). By multiplying the read value by the distance coefficient, the distance advanced in 0.1 second is obtained (step 305).

Next, the traveling distance value per 0.1 second thus obtained is integrated with the previously obtained value,
It is checked whether the traveling distance of the vehicle has reached 20 m (step 306), and if it is less than 20 m (step 306).
No, the current process is terminated and a new process is started.

As a result of the traveling distance calculation processing, when the accumulated traveling distance is a constant distance, for example, 20 m (Yes in step 306), the traveling direction and traveling distance R at that time (in the present embodiment, in this embodiment). 20 m) is output (step 307). In step 307, the accumulated distance is further initialized and the accumulated traveling distance is newly started.

Next, the process of calculating the virtual current position of the vehicle based on the calculated traveling direction and traveling distance and obtaining the candidate points of the vehicle based on the calculated virtual current position will be described.

FIG. 4 shows the flow of this processing.

This processing is a routine of the microprocessor 24 which is started and executed in response to the output of the traveling direction and traveling distance from FIG. That is, in the present embodiment, this process is started every time the vehicle advances 20 m.

In this process, first, step 30
The traveling direction and traveling distance output in 7 are read (step 401). Next, based on those values, the amount of movement of the vehicle is obtained separately in the latitude and longitude directions. Further, the movement amount in each of these directions is added to the position of the vehicle candidate point obtained in the previous process for obtaining the vehicle candidate point, and the virtual current position (position where the current vehicle is estimated to exist) ( A) is calculated (step 402).

If there is no candidate point obtained in the previous process for obtaining the candidate point of the vehicle, such as immediately after the start of the apparatus, the position set separately is used as the position of the previously obtained candidate point. Then, the virtual current position (A) is obtained.

Here, the candidate points will be described. In an initial state such as immediately after the start of the device, the virtual current position (A) is uniquely determined by the user (driver) inputting predetermined information using the switch 14 and the like. Is located on the line segment corresponding to the road. However, after the vehicle has traveled, the virtual current position (A) may not exist on the line segment corresponding to the road due to an error in the direction sensor or the like. As a result, for example, as shown in FIG. 5, when the road is branched, that is, the node or end 6 of the line segment 61 corresponding to the road.
From FIG. 8, when two line segments 64 and 65 appear, it is often impossible to clarify which line segment the vehicle is on.

Therefore, in such a case, in this embodiment, the points existing on the line segment (two line segments in the example shown in FIG. 5) obtained by the process described later are set under predetermined conditions. Set as a candidate point with, and the current position, error cost, accumulated error cost described later, etc., respectively,
The memory 25 is configured to be stored in a predetermined area of the RAM. In addition, in order to facilitate the description, in the following description, one or more new candidate points will be generated from a single candidate point, unless it is clearly indicated that there are a plurality of candidate points.

Next, the first road search processing for matching with the road is executed only for the candidate points in the matching state obtained in the previous processing for obtaining the candidate points of the vehicle (step 403). In this example,
The matching state means that there is a road in which the distance from the virtual current position or the direction difference between the direction and the traveling direction of the vehicle is within a predetermined range in relation to the virtual current position. Then, as a result, a state in which the candidate point is obtained at a predetermined position on the road based on the virtual current position is referred to. On the other hand, there may be a case where there is no road whose distance and heading difference described above are within a predetermined range in relation to a certain virtual current position. In the present embodiment, in such a case, the point itself corresponding to the virtual current position A becomes a candidate point, and the candidate point thus obtained is called a free state candidate point.

FIG. 6 is a flow chart showing the first road search processing according to this embodiment.

As shown in FIG. 6, in this road search processing, first, predetermined road data is read from the CD-ROM 15 via the driver 16 and the DMA controller 23 (step 601). In this embodiment, the road data is approximated by a plurality of line segments 51 to 55 connecting two points as shown in FIG.
The one represented by the coordinates of the start point and the end point is used. For example, the line segment 53 has its starting point (x3, y3)
And the end point (x4, y4). Therefore, in this step 601, the line segment in which the candidate point in the matching state obtained by the previous process is located is selected, and the data regarding this is read.

Next, based on the coordinates of the line segment selected in step 601, a line segment including a position advanced by 20 m from the position of the candidate point along the traveling direction of the vehicle is searched. Coordinate data regarding this line segment is temporarily stored as data indicating the primary candidate line segment (step 602). More specifically, if the length of the line segment where the candidate point is located to the end in the traveling direction of the vehicle is greater than the length corresponding to 20 m, the line segment is regarded as the primary candidate line segment and its coordinate data and the like are calculated. Remember. In addition, the length of the line segment where the candidate point is located to the end in the traveling direction of the vehicle is 20
If the length is equal to or less than the length corresponding to m, a line segment connected to the line segment is searched.

Next, in step 602, it is judged whether or not at least one primary candidate line segment has been found (step 603). If it is judged no (No), the process proceeds to step 604.

On the other hand, if it is determined as Yes in step 603, an angle comparison process for comparing the angle between the traveling direction of the vehicle and the direction of the primary candidate line segment is executed. (Step 605). FIG. 8 is a flowchart showing the angle comparison process according to this embodiment. As shown in FIG. 8, in this process, the heading difference θd between the heading of the vehicle and the heading of the line segment is calculated (step 901), and the absolute value of the heading difference θd is smaller than a predetermined threshold value θth. Is also large (step 90)
2). In this embodiment, this threshold value θth is 30 °.
Is set to In step 902, no (N
o), the processing is terminated, while
If YES is determined, it is determined that the road is not the primary candidate line segment, and the temporarily stored data corresponding to the primary candidate line segment is deleted (step 903). .

When the angle comparison process shown in step 605 of FIG. 6 is completed, if a plurality of primary candidate line segments are stored in step 602, the angle comparison process is also executed for other primary candidate line segments (step 605, 60
6) When the angle comparison process is executed for all the primary candidate line segments, the process proceeds to step 607. In this way, the line segment where the candidate point obtained in the previous process is located, or among the line segments connected to this line segment, the heading difference between that heading and the heading of the vehicle is less than or equal to the threshold value θth. The data related to the line segment such as is stored as data indicating the primary candidate line segment.

In step 607, it is judged whether or not at least one temporarily stored primary candidate line segment exists. If it is determined No in step 607, the process proceeds to step 604. On the other hand, when it is determined to be Yes in step 607, the perpendicular distance comparison process is executed (step 608). FIG. 9 is a flowchart showing the perpendicular distance comparison processing according to this embodiment. As shown in FIG. 9, in this process, a vertical line is drawn from the virtual current position toward the primary candidate line segment, and the length L of this vertical line is obtained (step 1001). Then, the length L of this perpendicular is
It is determined whether or not it is less than or equal to a predetermined threshold value Lth (step 1002). That is, it is determined whether the primary candidate line segment exists within the range of the threshold value Lth from the virtual current position. If YES is determined in this step 1002, various data related to this primary candidate line segment are stored as data indicating the secondary candidate line segment, and from the candidate points obtained in the previous process. , Coordinate data of positions separated by a distance R along a predetermined line segment is stored as position data corresponding to the secondary candidate line segment.

On the other hand, if it is judged No in step 1002, the data related to this primary candidate line segment is erased, and as a result, the secondary candidate line segment is not generated (step 1004).

When the perpendicular distance comparison processing 608 is completed in this way, it is judged whether or not the processing is completed for all the primary candidate line segments (step 609).

By repeating step 608 and step 609, a predetermined segment is obtained in the traveling direction of the vehicle from the line segment where the candidate point obtained by the previous process is located, along the line segment or the line segment connected thereto. Is present, the heading difference between the heading and the traveling heading of the vehicle is equal to or smaller than a predetermined threshold value θth, and the distance to the virtual current position is a predetermined point. It is possible to obtain a secondary candidate line segment that is equal to or less than the threshold value Lth. Further, as position data corresponding to the obtained secondary line segment, coordinate data of a position separated by the distance R along the predetermined line segment from the candidate point obtained in the previous process can be obtained. This coordinate data corresponds to the data indicating the candidate points described later.

When the processing of steps 608 and 609 is completed for the primary candidate line segment, it is judged whether or not the secondary candidate line segment is obtained as a result of passing through these steps (step 610). If it is determined No in step 610, the process proceeds to step 604. On the other hand, if it is determined yes, the process ends.

For example, in FIG. 5, it is assumed that the virtual current position A is represented by the position indicated by the point 63 with respect to a certain candidate point 62 existing on the line segment 61. In such a case, first, the line segment 61 where the candidate point 62 is located is selected (step 601), and the distance from the candidate point 62 on this line segment to the end 68 in the traveling direction of the vehicle is determined. In the case of the example of FIG. 5, since there is a road connected to this line segment,
The data related to the line segments 64 and 65 are each temporarily stored as data indicating the primary candidate line segment, and the angle comparison process (step 605) is executed in association with each. Here, in the example of FIG. 5, | θ (1) −θcar |
Assuming that <θth and | θ (2) −θcar | <θth, the processing loop consisting of steps 605 and 606 is repeated twice, and the perpendicular distance comparison is performed in relation to each of the line segments 64 and 65. The process (step 608) is executed.

Further, in the example of FIG. 5, L (1) <Lt
If h and L (2) <Lth, then the line segment 64,
Data related to 65 are stored as secondary candidate line segments,
Further, the points advanced by a length corresponding to the traveling distance R (20 m in the present embodiment) from the candidate point 62 along the line segments 61 and 64 or the line segments 61 and 65 are the candidate points 66 and 67. As the coordinate data of this point, the data corresponding to the distances L (1) and L (2) from the virtual current position to the line segment, and the line segment angles θ (1) and θ (2).
The data corresponding to is stored.

Returning again to the description of the first road search process of FIG. Here, when it is determined as No in step 603, when all the primary candidate line segments are deleted in the angle comparison processing in step 605 (step 6
If the secondary candidate line segment is not obtained in the perpendicular distance comparison processing in step 608 (No in step 610), the coordinate data indicating the virtual current position is displayed. , Becomes data indicating candidate points.

When the first road search processing of step 403 is completed in this way, the second road for matching with the road only with respect to the free state candidate points obtained in the previous processing for obtaining the candidate points of the vehicle. The road search process is executed (step 404). First road search process (step 403) and second road search process (step 404)
By executing, it becomes possible to obtain new candidate points for all the candidate points obtained by the previous processing. FIG. 10 is a flowchart showing the second road search processing according to this embodiment.

As shown in FIG. 10, this processing (steps 1301 to 1304) is similar to the first road search processing (step 403 in FIG. 4) for the candidate points in the matching state shown in FIG. The differences between these two processes are as follows. That is, in the first road search process, the line segment on which the candidate point obtained in the process of finding the candidate point of the previous vehicle is located or the line segment connected to this is temporarily set as the primary candidate line segment. From these primary candidate line segments, the azimuth difference between the azimuth and the vehicle azimuth is less than or equal to a predetermined threshold θth, and the length corresponding to the distance from the virtual current position is a predetermined threshold. A line segment within the value Lth is selected as a secondary candidate line segment.

On the other hand, in the second road search process, all line segments within the preset distance D centered on the virtual current position (A) are extracted (step 130).
1) From these line segments, select a line segment whose heading difference between the heading and the vehicle heading is equal to or less than a predetermined threshold value θth (step 1
302) Further, a distance between the selected line segment and the virtual current position is obtained, and a line segment whose length corresponding to this distance is within a predetermined threshold value Lth is selected as a secondary candidate line segment. (Step 1303). In other words, in step 602 of the first road selection process, the line segment on which the candidate point is located, or some line segments extending from the branch points of the line segment are selected. In 1302, the line segment to be extracted is determined based on the road data included in the read map data. Therefore, the processing time for executing steps 1301 to 1303 depends on the density of the road corresponding to the road data, and particularly when the map corresponding to the read map data is an urban area. When the density is high, this processing time is large compared to the time required to execute the corresponding processing in the first road search processing.

In the second road search processing, when step 1303 is completed, the line segment extracted in steps 1302 and 1303, that is, the heading difference between the heading and the vehicle heading is less than or equal to the threshold value θth. And a line segment whose length corresponding to the distance from the virtual current position is equal to or smaller than the threshold value Lth is selected as a secondary candidate line segment, and various data related to the line segment are secondary data. It is stored as data indicating the candidate line segment. Further, the point where the current position is present, and the foot of the perpendicular line drawn from the virtual current position to the line segment, that is, the intersection of this perpendicular line and the line segment is determined as the candidate point, and the coordinate data of these candidate points is determined. Is stored (step 1304). Note that in the second road search process, the intersection of the perpendicular and the line segment drawn from the virtual current position to the line segment becomes the candidate point. This is because the candidate point obtained by the previous process is in the free state. This is because there is no line segment to follow.

In the second road search process,
When the line segment does not exist within the predetermined range D from the virtual current position, the azimuth difference between the azimuth and the traveling azimuth of the vehicle is the threshold value θ.
If there is no line segment equal to or less than th, or if there is no line segment whose length corresponding to the distance from the virtual current position is equal to or less than the threshold value Lth, the point corresponding to the virtual current position is unique. Will be the candidate point.

As described above, when the second road search processing in step 404 ends, the length of the perpendicular line associated with the n candidate points obtained by the first road search processing and the second road search processing. It is defined by the following formula based on L (i) (1 ≦ i ≦ n) and the bearing difference θd (i) between the bearing of the secondary candidate line segment where the candidate point is located and the bearing of the vehicle. The error cost ec (i) is calculated (step 404).

Ec (i) = α × | θd (i) | + β × L (i) where α and β are weighting factors. The value of these weighting factors determines whether the deviation between the traveling direction of the vehicle and the direction of the line segment or the deviation between the virtual current position and the line segment is important in selecting the road. Therefore, it is determined.
For example, when it is important to select a traveling azimuth and a road whose azimuth is close to the azimuth, the α is increased.

Next, the calculated error cost ec
According to (i) and the accumulated error cost es related to the candidate points obtained in the previous process, the accumulated error cost es in this process defined by the following formula is calculated (step 405). .

Es (i) = (1−k) × es + k × ec (i) Here, k is a weighting coefficient larger than 0 and smaller than 1. The cumulative error cost es (i) represents how much the error cost calculated in the previous process is reflected in the error cost calculated in the current process.

Furthermore, the calculated cumulative error cost es
The reliability trst defined by the following equation based on (i)
(I) is calculated (step 406).

Trst (i) = 100 / (1 + es (i)) As apparent from the above equation, the accumulated error cost ec
The reliability trst increases as (i) increases.
(I) decreases and approaches 0 (zero). On the other hand, as it becomes smaller, the reliability trst (i) increases, and its value approaches 100.

By performing such processing, the reliability trst (i) associated with the n secondary candidate line segments obtained corresponding to a certain candidate point is obtained. When there are a plurality of candidate points, the reliability trst associated with the plurality of secondary candidate line segments obtained corresponding to each candidate point may be calculated.

In connection with the candidate points in the free state, the error cost ec (n) to be calculated in step 405 is given a constant value larger than the error cost value obtained in the matching state. To be

Then, these new candidate points are sorted according to the value of the reliability trst corresponding to each of the thus obtained candidate points (step 408) and then obtained in steps 403 and 404. From the candidate points, a display candidate point determination process of determining display candidate points which are candidate points to be displayed on the display 17 is executed (step 409).

FIG. 11 is a diagram showing a display candidate point determination process according to this embodiment. As shown in FIG. 11, first, as will be described later, it is determined whether or not a branch point passage flag flag which is set to 1 after the vehicle has passed the branch point is 0 (zero) (step 1101), The branch point passage flag is set to 1 in this process or reset to 0 (zero), and is reset to 0 (zero) in the initialization process executed when the apparatus is started up. .

In step 1101, the answer is yes (Y
es), it is determined whether or not the display candidate point has passed the branch point (step 1102). More specifically, it is determined that the display candidate point has passed the branch point when a plurality of candidate points in the matching state are generated based on the display candidate point obtained by the previous process.

If it is determined No in step 1102, the bias value HYS to be added to the reliability of the candidate points generated based on the display candidate points obtained in the previous processing is set to HYShigh. (Step 110
3). Then, the HYS obtained in the previous step is added to the reliability trst of the candidate points obtained based on the display candidate points obtained in the previous process (step 1104), and then the reliability of all candidate points is set. The comparison is performed, and the one having the largest value is determined as the display candidate point (step 1105).

The reason why the predetermined bias value HYS is added to the candidate points obtained from the display candidate points in this way is as follows. That is, the display candidate point is a candidate point having the highest reliability, that is, a candidate point having high credibility as the actual vehicle position. Therefore, by adding a minute value HYS to the reliability of the candidate point obtained from this, a mark (for example, an arrow shown in FIG. 2) displayed as the current position of the vehicle on the display device can be displayed between the roads. It prevents movement and significant changes in the front-back direction on the road.

On the other hand, if a too large HYS is given, it may take time to obtain the display candidate point at a more preferable position when the position of the display candidate point deviates from the actual vehicle position. There is. Therefore, this H
The value of YS is adjusted according to the direction sensor, the accuracy of road data, and the like.

In step 1105, if there are three or more candidate points whose reliability is to be compared,
Among candidate points other than the candidate points obtained based on the display candidate points, the candidate point having the highest reliability value is determined, and the reliability of this candidate point and one or more obtained based on the display candidate points are determined. Is compared with the reliability of the candidate point.

If YES at step 1102, the branch point passage flag fl
When ag = 1 is set, step 11 described later is performed.
The branch effective distance counter LC = 0 indicating the period in which the processing in 11 should be executed is reset (step 110).
6). Furthermore, when the display candidate point obtained in the previous process is not on the line segment corresponding to the expressway, the effective distance threshold LCth = Lgn is set (steps 1107 and 110).
8) On the other hand, when the display candidate point is on the line segment corresponding to the expressway, LCth = Lhw is set (steps 1107 and 1109). In this embodiment, Lgn
Is preset to a value corresponding to 500 m, and Lhw is preset to a value corresponding to 2 km. Even after passing through step 1108 or step 1109, the reliability of the display candidate points obtained by the previous processing is trst = trst +
It is set to HYS (step 1104), and display candidate points are determined by comparing the reliability (step 110).
5).

As described above, when the branch point passage flag flag = 1 is set by passing through step 1106,
In step 1101, it is determined as No.
In this case, only the value corresponding to the traveling distance R of the vehicle (20 m in this embodiment) is applied to the branch effective distance counter LC.
Is incremented (step 1110), and then it is determined whether the value of LC is larger than LCth (step 1111). If it is determined No in step 1111, the process proceeds to step 1112.

At step 1112, the bias value HYS is set to the following value. That is, among the candidate points other than the candidate points obtained based on the display candidate points, one or a plurality of candidates obtained based on the candidate points obtained when it is determined that the branch point is passed in step 1102 described above. Bias value HYS for branch candidate point which is a point
Is set to HYSlow which is somewhat smaller than HYShigh set in step 1103, and the bias value HYS for candidate points other than the branch candidate points is set to HYS
Set to high (step 1111).

For example, as shown in FIG. 12, a line segment 120 corresponding to a road and a line segment 121 connected thereto,
122 and the like, and the line segment 124 and the line segment 125 connected thereto, and at some point, step 401 of FIG. 4 or step 408 described below is executed, and the point 130 on the line segment 121 and the line segment 125. The upper point 131
I think that it was decided as a candidate point. Here, candidate point 13
It is assumed that 0 is a point generated based on the display candidate points obtained by the previous processing. In this case, steps 1101 to 110 in the display candidate point determination process shown in FIG.
As a result, the reliability trst regarding the candidate point 130 is the reliability trst of the candidate point 130 itself plus HYShigh (step 1104). That is, in step 1105,
When determining which of the candidate points 130 and 131 is to be the display candidate point, the reliability degree trst + HYShigh associated with the candidate point 130 is compared with the reliability degree trst associated with the candidate point 131. That is, the bias value HY
By Shigh, candidate points other than the candidate points obtained based on the display candidate points are less likely to be determined as new display candidate points.

Here, of these candidate points, the point 130 is
I think that it was decided as a display candidate point. It is considered that the processing of steps 401 to 408 is executed and the candidate points 132 to 134 are obtained as the vehicle further travels the distance R (20 m in this embodiment). In this case, in the display candidate point determination process shown in FIG.
Steps 1101, 1102, 1106, 1107, 1
108 or 1109, 1104 and 1105 are sequentially executed, and as a result, candidate points 132 and 133 are obtained.
Each reliability trst regarding the candidate point 13
HYShigh is added to the reliability trst of 2 and 133 itself (step 1104). That is,
In step 1105, candidate points 132-133
When determining which of the two is to be the display candidate point, the reliability degree trst + HYShigh associated with the candidate point 132,
Confidence level trst + HYShigh related to candidate point 133
And the reliability trst associated with the candidate point 134 are compared.

Furthermore, of these candidate points, the point 132 is
It is assumed that the candidate points 135 to 137 are obtained by assuming that the candidate points have been determined as the display candidate points and the vehicle further travels the distance R (20 m in this embodiment) to execute the processing of steps 401 to 408. Think In this case, in the display candidate point determination process shown in FIG.
Steps 1101, 1110 through 1112, 1104
As a result, the reliability of the candidate point 136 that is a branch candidate point out of the reliability trst of the candidate point 135 is the reliability trst of the candidate point 135 itself plus HYSlow. ,
On the other hand, the reliability for the candidate point 137 is
HYShigh is added to the reliability trst of 5 itself (step 1104). That is, step 11
In 05, when determining which of the candidate points 135 to 137 is to be the display candidate point, the reliability degree trst associated with the candidate point 136 and the reliability degree trst associated with the candidate point 137 are compared, If the confidence associated with point 136 is greater than that associated with candidate point 137, then the confidence associated with candidate point 135 trst + HY
Slow is compared to the confidence value trst associated with candidate point 136. On the other hand, when the reliability associated with the candidate point 136 is smaller than the reliability associated with the candidate point 137, the reliability trst + HYS associated with the candidate point 135.
high is compared with the reliability trst associated with the candidate point 137.

That is, among the candidate points other than the candidate points obtained from the display candidate points, the branch candidate point is less likely to be determined as a new candidate point by the bias value HYSlow, and the bias value HYShigh. Therefore, among the candidate points other than the candidate points obtained from the display candidate points, the candidate points other than the branch candidate points are less likely to be determined as new candidate points. Further, as described above, since the bias value HYSlow <HYShigh, the branch candidate point is more likely to be determined as a new candidate point than the other candidate points.

As the vehicle moves further,
When the value of the branch effective distance counter LC exceeds the set value of LCth, the branch point passage flag flag = 0 (steps 1110 and 1113). That is, the process of step 1112 can be performed only while the vehicle travels the distance corresponding to LCth after it is determined that the vehicle has passed the branch point.

As described above, when the display candidate point determination processing in step 409 of FIG. 4 is completed, the display candidate points determined in this processing, that is, the positions of the candidate points to be displayed on the display 17, the accumulation error. Cost, reliability,
A state flag indicating whether the state is the matching state or the free state is stored in a predetermined area of the RAM of the memory 25, and the positions of candidate points other than the display candidate points, cumulative error cost, reliability, The status flag and the like are also stored in a predetermined area of the RAM (step 410). In this embodiment, the data related to the seven candidate points can be stored. Therefore, when eight or more candidate points are calculated as a result of executing the processing of steps 401 to 408 in FIG.
Various data related to the seven candidate points in the descending order of the value of rst will be stored in a predetermined area of the RAM of the memory 25.

Finally, the data related to the display candidate points are output (step 411), and the process ends.

The display candidate points obtained by executing steps 401 to 410 in FIG. 4 are displayed on the screen of the display 17 by the processing based on the flowchart shown in FIG.

This process is a routine of the microprocessor 24 which is activated and executed every one second.

First, it is determined whether or not the switch 14 is instructed to change the map scale by looking at the contents of the parallel I / O 21 (step 1401). If it is pressed (Yes in step 1401),
Correspondingly, a predetermined scale flag is set (step 1402).

Next, the data indicating the position and orientation of the display candidate point obtained by executing the processing of FIG. 4 is read from a predetermined area of the RAM of the memory 25 (step 1403) and switched in step 1402. The map of the scale according to the content of the scale flag is displayed on the display 17,
For example, it is displayed in the state as shown in FIG. 2 (step 1
404).

Then, the position and the direction of the display candidate point are displayed by superimposing them on the map, for example, using the arrow symbol "↑" as shown in FIG. 2 (step 140).
5). Finally, the north mark indicating north and the distance mark corresponding to the reduced scale are displayed in a superposed manner as shown in FIG. 2 (step 1406).

In the present embodiment, the vehicle position and the direction are indicated by using the arrow symbols as described above, but the display form of the vehicle position and the direction is such that the position and the traveling direction are
The form may be arbitrary as long as the display state is clearly shown. The same applies to the north mark and the like.

According to this embodiment, the bias value HYS is added to the reliability of the candidate points obtained based on the display candidate points,
Since the display candidate point is determined by comparing the reliability added with this bias value and the reliability of other candidate points, the line segment where the display candidate point is located is determined based on a slight change in the reliability. As a result, the current position of the vehicle, which is changed, can be less likely to make an unnatural movement.

Further, according to the present embodiment, among the candidate points other than the candidate points obtained based on the display candidate points, the reliability of the candidate points corresponding to the branch candidate points and the display candidate points are obtained. When comparing the reliability of candidate points,
Bias value HYShigh used when comparing with other candidate points
A slightly smaller bias value HYSlow is added.
Therefore, when it is not clear on which road the vehicle is located after passing the branch point, it is a line segment other than the line segment on which the previous display candidate point is located and on which the branch candidate point is located. Since the possibility of generating a new display candidate point is increased by a minute, it is possible to more accurately display the current position of the vehicle.

Further, according to the present embodiment, the line segment where the candidate point is located or the line segment connected to this candidate point is searched in relation to the virtual current position obtained from the candidate point in the matching state. Therefore, it is possible to search for a desired line segment in a shorter time, as compared with a case where all the roads existing around the virtual current position are searched.

Further, according to the present embodiment, the traveling distance of the vehicle is corresponded along the line segment where the candidate point in the matching state is located and / or the line segment connected to the line segment where the candidate point is located. Since the position advanced from the candidate point by the length is used as the candidate point, it is possible to further reduce the error between the calculated current position of the vehicle and the actual current position of the vehicle.

The present invention is not limited to the above embodiments, and various modifications can be made within the scope of the invention described in the claims, and these are also included in the scope of the present invention. It goes without saying that it is one.

For example, in the display candidate point determination process of the above embodiment, the value of the threshold value LCth to be compared with the branch effective distance counter is Lhw (2 km when the vehicle is traveling on a highway. Is set to Lgn (a value corresponding to 500 m) when the vehicle is traveling on a general road. This value, the bias value HYSlow for the branch candidate points and the bias value HYShigh for the other candidate points define the period during which the process of giving the reliability of the candidate points obtained based on the display candidate points can be executed. . In this way, depending on whether the vehicle is traveling on a general road or on a highway,
The threshold is changed because there is a clear shape (the shape of the line segment corresponding to the road) between the roads that extend from the branch point.
This difference is due to the greater distance on the expressway. However, the threshold value is not limited to such a threshold value, and the threshold value set when the vehicle travels on a highway and the threshold value set when the vehicle travels on a general road are the same. However, it is clear that it is good.

Further, in the above embodiment, in the display candidate point determination processing of step 409 in FIG. 4, the bias value HYS is added to the reliability trst of the candidate points obtained based on the display candidate points obtained in the previous processing. And add
When there are multiple candidate points other than the candidate points obtained based on the display candidate points, the candidate point having the highest reliability value is determined from among the plurality of candidate points, and the reliability of the candidate point is determined. The display candidate point is determined by comparing the degree with the reliability obtained by adding the bias value HYS (steps 1104 and 1105 in FIG. 11).

However, the present invention is not limited to this. For example, referring to the candidate points sorted in the order of the reliability value in step 408 of FIG. 4, the candidate point having the largest value is set as the display candidate point. If the candidate point is not obtained based on the above, the reliability of the candidate point and the predetermined bias value HYS
The display candidate point may be determined by comparing with the reliability of the candidate point obtained based on the display candidate point added with.

Furthermore, the parameters used in the present embodiment are only given for the purpose of illustration, and therefore, these parameters are the processing speed of the device, the type of road on which the vehicle runs (for example, general road). , Expressways, etc.) should be understood.

Further, in the present specification, the term "means" does not necessarily mean physical means, but also includes the case where the function of each means is realized by software.
Further, the function of one means may be realized by two or more physical means, or the functions of two or more means may be realized by one physical means.

[0096]

According to the present invention, it is possible to provide a current position calculation system for calculating a more accurate current position of a vehicle while reducing unnatural movement of the current position of the vehicle displayed on the display device. It will be possible.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a current position calculation device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a display example of a map and a current position according to the present embodiment.

FIG. 3 is a flowchart showing a process of calculating a traveling direction and a traveling distance of a vehicle according to the present embodiment.

FIG. 4 is a flowchart showing a process of calculating candidate points for a vehicle according to this embodiment.

FIG. 5 is a diagram for explaining a line segment corresponding to a road, a virtual current position, and a candidate point.

FIG. 6 is a flowchart showing a first road search process according to the present embodiment.

FIG. 7 is a diagram for explaining an example of road data according to the present embodiment.

FIG. 8 is a flowchart showing an angle comparison process according to the present embodiment.

FIG. 9 is a flowchart showing a perpendicular distance comparison process according to this embodiment.

FIG. 10 is a flowchart showing a second road search process according to the present embodiment.

FIG. 11 is a flowchart showing display candidate point determination processing according to the present embodiment.

FIG. 12 is a diagram for explaining a bias value added to the reliability of candidate points in the display candidate point determination processing according to the present embodiment.

FIG. 13 is a flowchart showing a current position display process according to this embodiment.

[Explanation of symbols]

 10 Current Position Calculation Device 11 Angular Velocity Sensor 12 Direction Sensor 13 Vehicle Speed Sensor 14 Switch 15 CD-ROM 16 CD-ROM Read Driver 17 Display 18 Controller

Claims (4)

[Claims] 1. A current position calculation system mounted on a vehicle for calculating the current position of the vehicle, comprising: an azimuth detecting means for detecting a traveling azimuth of the vehicle; and a distance calculating means for calculating a traveling distance of the vehicle. The current position of the vehicle based on the relative displacement obtained based on the traveling direction and the traveled distance and a candidate point indicating a state where the vehicle is located on any road or a state where the vehicle is not located on the road. A virtual current position generating means for generating a virtual current position expected to be, a virtual current position, and a road corresponding to the road data based on data indicating a road direction included in the road data included in the map data. A candidate point generation unit that generates a candidate point indicating that a vehicle exists above, and a reliability calculation that calculates reliability indicating the reliability that the vehicle exists at a position on the road corresponding to the candidate point. Means, and determining means for comparing the reliability of the candidate points and determining the candidate point having the largest value as the display candidate point indicating the current position of the vehicle, wherein the reliability calculation means is the display candidate. First bias value adding means for giving a predetermined first bias value to the reliability value of the candidate point obtained based on the points, and while the vehicle travels a predetermined distance after passing the branch point,
A second bias value adding means for giving a predetermined second bias value smaller than the first bias value to the reliability of the candidate points obtained based on the display candidate points, and the determining means. A candidate point obtained from the display candidate points when the vehicle passes the branch point, the first branch candidate point other than the newly obtained display candidate point, and the vehicle traveling the predetermined distance. In the meantime, the reliability of one or more second branch candidate points obtained based on the first branch candidate point and the display candidate point obtained by adding a second bias value to the reliability of the second branch candidate point are obtained. And the reliability of candidate points other than the first branch candidate point and the second branch candidate point, and the display candidate in which a first bias value is added to the reliability. Configured to compare the confidence level of the candidate points obtained based on the points A current position calculation system characterized by the above. 2. The determining means compares the reliability of any one of the first branch candidate point and the second branch candidate point with the reliability of candidate points other than the branch candidate point. And the reliability of the candidate point having the largest reliability value obtained by the first comparing means, and the first bias value or the second bias value according to the candidate point. The present position calculation system according to claim 1, further comprising a second comparison unit that compares the reliability of the candidate points obtained based on the added display candidate points. 3. Further, when the vehicle is traveling on a highway, a first distance is given to the predetermined distance, while when the vehicle is traveling on a general road. The present position calculation system according to claim 1 or 2, further comprising: a distance giving unit that gives a second distance smaller than the first distance. 4. A relative displacement obtained based on a traveling direction and a traveling distance of the vehicle, and a candidate point indicating a state where the vehicle is located on any road or a state where the vehicle is not located on the road. , A virtual current position expected to be the current position of the vehicle is generated, and on the road corresponding to the road data based on the virtual current position and data indicating the road direction included in the road data included in the map data. To generate a candidate point indicating that the vehicle exists, at the position on the road corresponding to the candidate point, calculate the reliability indicating the credibility that the vehicle exists, comparing the reliability of the candidate point, A current position calculation method for calculating a current position of a vehicle, including a step of determining a candidate point having the largest value as a display candidate point indicating a current position of the vehicle, wherein the step of calculating the reliability includes the display. Candidate A first bias value adding step of giving a predetermined first bias value to the reliability value of the candidate point obtained on the basis of the display, while the vehicle travels a predetermined distance after passing the branch point. Based on the reliability of the candidate points obtained based on the candidate points, the first
A second bias value adding step for giving a predetermined second bias value smaller than the bias value of, and the determining step includes a candidate obtained from the display candidate points when the vehicle has passed the branch point. A first branch candidate point other than the newly obtained display candidate point and one or more points obtained based on the first branch candidate point while the vehicle travels the predetermined distance. The reliability of the second branch candidate point is compared with the reliability of the candidate point obtained based on the display candidate point obtained by adding the second bias value to the value, and
Reliability of candidate points other than the first branch candidate point and the second branch candidate point, and reliability of candidate points obtained based on the display candidate points obtained by adding a first bias value to the values. A method for calculating a current position, characterized in that it is configured to compare.