JPH06289778A - Vehicular position detector - Google Patents

Abstract

PURPOSE:To avoid degradation in position detection precision and to stably continue map matching for a long time by selecting a combination of satellites whose error ellipse of vehicular position measurements supplied by a GPS receiver produces a minimum error along the direction of a road and by measuring the position. CONSTITUTION:If the direction of a road, on which a vehicle is moving, is specified, a processor selects a combination of satellites so that the direction of the major axis of an error ellipse becomes approximately normal to the direction of the road and obtains a measured position PG. Therefore, the vehicular position on the road is determined within a relatively narrow region with a high probability. When the road is not specified, a combination of the satellites is selected so that the direction of the major axis of an error ellipse becomes approximately normal to the direction of the road and the measured position PG is obtained. Thus, other nearby roads are discriminated and the road on which the vehicle is moving is easily specified. Therefore, the measured position PG obtained from the GPS receiver is used as the vehicular position in either case.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle position detecting device, and more specifically, it obtains the vehicle position by using a direction sensor (gyro etc.) and a distance sensor (wheel speed sensor etc.) mounted on the vehicle. Pattern matching is performed between the vehicle position and road network data obtained from the road map memory, and the degree of similarity between vehicles on each road (referred to as the matching rate between the vehicle's running locus and the map pattern) and the vehicle existence probability area ( When the vehicle position is detected based on the region where the vehicle existence probability is equal to or higher than a certain value, which is determined by the accuracy of the position detection method, the vehicle position is determined using the positioning position acquired from the GPS receiver. The present invention relates to a vehicle position detection device that can be modified.

[0002]

2. Description of the Related Art Conventionally, attempts have been made to obtain a running locus of a vehicle by using a direction sensor and a distance sensor. This method is called dead reckoning because it detects its own position only by the sensor mounted on the vehicle, and it can be adopted relatively easily because no external support equipment is introduced. However, since an error occurs in the sensor, the position detection error accumulates as the traveling distance increases.

Therefore, a map matching method has been proposed which eliminates accumulated errors by performing pattern matching between the traveling locus obtained by the sensor and road network data. At present, a vehicle position detecting device utilizing this has been developed. (JP-A-63-148115, JP-A-63-148115)
115004, Japanese Patent Laid-Open No. 64-53112). However, in the vehicle position detection device, if the road network data is inaccurate or the road network has a complicated shape or a grid shape, it becomes difficult to compensate the position error obtained by dead-reckoning with a map, It may be difficult to detect the vehicle position. Therefore, the road on which the vehicle exists may be considered as another road. Further, once the vehicle position is incorrect, it may take time to recover the correct position.

One method is to improve the accuracy of road network data, but there is a drawback that labor and cost increase rapidly. As described above, the reliability of the map matching method is not sufficient, and it has been a problem in the art to improve the reliability. Therefore, a satellite navigation system GPS (Global Positioning) that can know the absolute position of the vehicle
A position detection method has been proposed in which the absolute position of the vehicle is known by using the (System) and the vehicle position is corrected using this absolute position (referred to as a positioning position) to supplement the accuracy of the map matching method. 2-275310).

The GPS (Global Positioning System) is a technology for positioning one's own position by using radio waves from GPS satellites. The principle is that a plurality of artificial satellites orbiting in a predetermined orbit are used. The purpose is to measure the two-dimensional or three-dimensional position of the self by measuring the propagation delay time of the generated radio wave. The positioning position of the receiver is known by measuring the propagation delay time of signals from three or four orbiting satellites.

[0006]

If the method according to the above proposal is adopted, the position detection accuracy is improved.
The error is distributed in the elliptical area centered on the measured position of the vehicle, which is obtained by using the GPS. When this error becomes large, it becomes larger than the error in the detection position obtained by the map matching method, and it is no longer possible to play a role of compensating for the decrease in accuracy of the map matching method.

On the other hand, when positioning is performed by the GPS receiver, a combination of satellites is designated to perform positioning. That is, there are more than ten GPS satellites orbiting the earth at present (24 in the future), and a combination of three or four satellites is selected from these. The distribution of the vehicle positioning position error supplied from the GPS receiver is an ellipse as is known, and the shape of the ellipse differs depending on the combination of satellites used for positioning. For example, as shown in FIG.
When the combination of satellites 1, 2, 3, 4 in the north-south direction is selected, the error ellipse of the positioning position becomes an ellipse elongated in east and west. When a combination of satellites 5, 2, 6, and 7 in the east-west direction is selected, the error ellipse of the positioning position becomes an ellipse elongated in north and south.

An object of the present invention is to utilize a distribution of positioning position errors supplied from a GPS receiver to prevent vehicle position detection from deteriorating in position detection accuracy and to continue stable map matching navigation for a long time. To provide a device.

[0009]

[Means and Actions for Solving the Problems]

(1) In order to achieve the above object, the vehicle position detecting device according to claim 1 detects a vehicle position on a road by a map matching method, and is one of a plurality of GPS satellites that orbit. From the GPS receiver, the combination specifying means capable of specifying the combination of the satellites used for positioning from the above, the position acquisition means for acquiring the positioning position of the vehicle in the combination of the satellites specified by the combination specifying means, and the map matching. Correction operation means for correcting the obtained vehicle position by using the positioning position acquired by the position acquisition means, and the correction operation means, when the road on which the vehicle is traveling can be specified, the GPS receiver. The combination designating means is instructed to adopt the combination of satellites in which the measured position of the vehicle supplied from the vehicle has the smallest error in the direction in which the road extends.

According to the vehicle position detecting device having the above-mentioned configuration, during the course of performing the map matching navigation, the degree of similarity of the vehicle to each road and the vehicle existence probability region in which the vehicle exists with a certain probability or more are evaluated, It is possible to determine whether to use the GPS positioning position for position correction. And G
When it is necessary to use the PS receiver, the positioning position of the vehicle obtained from the GPS receiver is used to correct the vehicle position obtained by the map matching navigation,
It is possible to determine the vehicle position with higher accuracy.

In particular, when the road on which the vehicle is traveling can be specified, a satellite whose error ellipse of the vehicle positioning position supplied from the GPS receiver has a minimum error with respect to the direction in which the road extends. Since it is not known where on the road the vehicle is located, it is possible to specify the vehicle position on the road within a relatively short range of the error ellipse, as shown in FIG. it can. (2) In the vehicle position detection device according to claim 2, when the road on which the vehicle is traveling cannot be identified, the correction calculation means determines that the positioning position of the vehicle supplied from the GPS receiver is the direction in which the road extends. The combination designating means is instructed to adopt a combination of satellites having a minimum error in a direction substantially at right angles.

In this case, there are a plurality of road candidates on which the vehicle travels, and the error ellipse of the vehicle positioning position supplied from the GPS receiver is relative to the direction substantially perpendicular to the direction in which the road extends. Since a combination of satellites having a minimum error is adopted, the vehicle can be distinguished from other adjacent roads based on a relatively short range of the error ellipse as shown in FIG. It becomes easy to identify the road on which to drive.

[0013]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 3 shows a schematic configuration of the vehicle position detection device. The vehicle position detection device includes a console 1, a display 2, a direction sensor 3, a distance sensor 4, map data, a road map memory 5, which stores road network data,
A memory drive 6 for reading data from the road map memory 5, a GPS receiver 7 for receiving radio waves from a set of designated satellites of the orbiting satellites 7a to 7e, for example, 7a to 7c, and the degree of similarity of each vehicle road. , A processing device 8 having a function as a correction calculation means for evaluating the vehicle existence probability and correcting the vehicle position using the positioning position PG acquired by the GPS system in accordance with the evaluation result, and calculating the guide route, Navigation for performing various arithmetic control such as searching / reading a road map in a predetermined range, generating display data for guiding the driver, driving the display unit 2, the voice output device 10, and controlling the processing device 8. It has a controller 9.

More specifically, the console 1
Has a key input board (not shown) for starting / stopping the vehicle position detecting device, moving a cursor on the screen, scrolling a road map displayed on the screen, and the like. The road map memory 5 can use a large-capacity storage medium such as a CD-ROM and a magnetic tape, and the road map memory 5 is divided into meshes and the road form is divided into mesh units. The display map data for graphic display for displaying the coordinate position and the like is stored, and the road network data for map matching is recorded for each mesh unit.

The road network data includes combination data of a node representing a branch point and a link representing a road segment, distance data of the link, required time data for running the link, road type data (highway, highway). , City streets, etc.), road width data, and place name fields, famous facilities, point data for specifying specific points such as railways, and the like.

Further, as the display map data, a plurality of maps having different scales are prepared according to the size of division when the road map is divided into meshes. Display 2
A transparent touch panel is mounted on the screen of a CRT, a liquid crystal panel, or the like. Then, the display 2 displays the initial setting menu supplied from the navigation controller 9, and the driver touches the display position on the screen,
Enter the type of display screen, map magnification, destination, etc. That is, it mediates the dialogue between the navigation controller 9 and the driver.

The azimuth sensor 3 is for detecting a change in azimuth as the vehicle travels, and is a geomagnetic sensor, a gyro, or a turning angle sensor for detecting a turning angle based on a difference in rotational speed between the left and right wheels. Can be used. The distance sensor 4 detects the traveling distance based on the speed of the vehicle, the number of rotations of the wheels, or the like, and a wheel speed sensor, a vehicle speed sensor, or the like can be used.

The navigation controller 9 has a function of obtaining the vehicle position from the processing device 8 and displaying the current position and the destination in an overlapping manner on the map. Specifically, it consists of a microcomputer, graphic processor, image processing memory, etc., and displays menu screens, map searches, scale switching, scrolling, current vehicle position and direction, and destinations and landmarks. Display and display the direction and distance to the destination.

The GPS receiver 7 measures the time of arrival of the radio wave from each satellite by decoding the pseudo noise code received from any combination of three or four GPS satellites, and positions itself on the ground. Calculate the position. The processing device 8 integrates the traveling distance detected by the distance sensor 4 and the traveling direction change amount detected by the azimuth sensor 3, and based on the comparison between the accumulated data and the road network data read by the memory drive 6. In addition to detecting the vehicle position, the vehicle position is appropriately corrected using the data relating to the vehicle positioning position PG obtained by the GPS receiver 7, and the final position and azimuth of the vehicle are output. further,
A combination of satellites used for positioning can be designated for the GPS receiver 7.

The functional blocks of the processing unit 8 are shown in FIG.
The input preprocessing unit 22 inputs the azimuth data sampled from the azimuth sensor 3 and the distance data sampled from the distance sensor 4, and performs calibration and filtering to obtain the optimum estimated azimuth. The current position estimating means 23 calculates the vehicle position by dead reckoning from the optimum estimated azimuth and distance data obtained from the input preprocessing means 22, and
The corrected current position obtained from the position reset means is taken in and the vehicle position is updated. The traveling road estimating means 24 repeatedly calculates the similarity between the road network data obtained from the road map memory 5 and the vehicle position, calculates the vehicle position of the vehicle on the road, and calculates the vehicle existence probability of the calculated vehicle position. Ask. The position reset means 25 corrects the vehicle position in the manner described above.

The management judging means 21 designates the arrangement of satellites used for positioning from a plurality of GPS satellites orbiting, and the positioning position PG acquired by the GPS system in the arrangement of the satellites and the arrangement of the satellites. Or the error ellipse at the positioning position PG obtained based on the status signal indicating the reception state of the satellite radio wave, and the vehicle position, the similarity and the vehicle existence probability at the vehicle position obtained by the traveling road estimating unit 24. The vehicle position is corrected by an algorithm as shown in FIG. 5, and the vehicle position newly obtained based on this is supplied to the position output means 26.

Hereinafter, with reference to the flowchart of FIG.
An algorithm for correcting the vehicle position will be described using the vehicle positioning position PG obtained from the GPS navigation system.
First, the position error between the estimated position of the vehicle obtained from the current position estimation means 23 and the actual vehicle position is plotted on the horizontal axis, and the similarity with the road network data is calculated based on the estimated position to determine that the vehicle position is the road. When the matching probability is plotted on the vertical axis, the correlation as shown in FIG. 6 is obtained. That is, if the position error is small, the vehicle position can be reliably obtained on the road while traveling for a while and repeatedly calculating the similarity between the vehicle position and the road pattern. In other words, the vehicle position can be narrowed down to a specific road. Conversely, if the position error becomes large, the probability that the vehicle position can be narrowed down to a specific road will decrease even if the similarity with the road pattern is calculated, and if the position error becomes considerably large (Fig. 6 ems
Above points), no matter how many times the degree of similarity is calculated, matching with the road cannot be taken. In this case, the position of the vehicle cannot be found on the road, and the road needs to be specified by some method.

Further, even when the position of the vehicle can be found on the road, it is necessary to specify the position of the vehicle on the road. For example, when a vehicle makes a turn at an intersection, the direction of the vehicle changes abruptly. Therefore, if there is an intersection near by judging from the road network pattern, the vehicle can be located at the intersection.
However, when the vehicle is traveling a long distance while the shape of the road changes little (for example, when traveling on a highway), the position of the vehicle cannot be specified, and the error gradually increases. Even in such a case, it is necessary to specify the vehicle position by some method.

Therefore, in order to specify the vehicle position, the management judgment means 21 corrects the vehicle position using the positioning position PG acquired by the GPS receiver 7 under a certain condition,
The corrected position is returned to the current position estimating means 23. First, the traveling road estimation means 24 uses the road map memory 5
The similarity between the road network data obtained from the above and the vehicle position is repeatedly calculated over a certain traveling distance (for example, 2 km or more), and it is determined whether or not a certain degree of similarity is obtained (FIG. 5, step S1). When the vehicle position is calculated with sufficient probability in step S1, YES is selected and the process returns to "return".

If the vehicle position cannot be obtained, NO is selected in step S1 and the process proceeds to step S2.
In step S2, it is determined whether or not the vehicle has traveled a predetermined distance l0 or more since the previous vehicle position was corrected. If the distance l0 is also not advanced, return to "return" to avoid frequent modifications.

If the distance has advanced by more than lo, step S3
Proceed to and determine whether the road can be identified. When the road is identified, the processor 8 adopts the satellite combination A in which the major axis direction of the error ellipse is substantially perpendicular to the road extending direction as shown in FIG. 1 (step S4). ), And obtain the positioning position PG. Therefore, the vehicle position on the road can be specified with high probability within a relatively narrow range.

When the road cannot be specified, a combination B of satellites is adopted in which the major axis direction of the error ellipse is substantially perpendicular to the extending direction of the road as shown in FIG. 2 (step S5). Obtain the positioning position PG. Therefore, the road can be distinguished from other adjacent roads, and the road on which the vehicle travels can be easily identified. And in any case GP
The positioning position PG acquired by the S receiver 7 is set as the vehicle position of the vehicle (step S6). In other words, the vehicle position cannot be obtained with sufficient probability even by map matching.
The vehicle position is replaced using the positioning position PG obtained from the S system.

After that, the corrected vehicle position is set as an initial position, and the position of the vehicle is tracked again using map matching.

[0029]

As described above, according to the first aspect of the present invention, when the road on which the vehicle is traveling can be identified while the map matching navigation is being performed, it is supplied from the GPS receiver. Since the positioning position is obtained by using a combination of satellites where the error ellipse of the positioning position of the vehicle has the smallest error with respect to the direction in which the road extends, the positioning of the vehicle is corrected within a relatively short range, and the accuracy is improved. It is possible to determine a high vehicle position.

According to the second aspect of the present invention, when there are a plurality of road candidates on which the vehicle travels, the error ellipse of the positioning position of the vehicle supplied from the GPS receiver is perpendicular to the direction in which the road extends. Since a combination of satellites that has the smallest error in the direction is adopted, it becomes possible to distinguish from other adjacent roads based on a relatively short range, and it is easy to identify the road on which the vehicle is traveling. become.

Therefore, in any of the inventions, it is possible to prevent the deterioration of the position detection accuracy of the vehicle position obtained only by the map matching process and to continue the stable map matching navigation for a long time. Further, the detection accuracy can be secured even if the road map is somewhat inaccurate.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a method of identifying a vehicle position on a road within a relatively narrow range of an error ellipse.

FIG. 2 is a diagram illustrating a method of identifying a road on which a vehicle travels with reference to a relatively narrow range of an error ellipse.

FIG. 3 is a block diagram showing an overall configuration of an embodiment of a vehicle position detecting device.

FIG. 4 is a block diagram showing a flow of a position detection process of the vehicle position detection device.

FIG. 5 is a flowchart showing a flow of a detection position correction process.

FIG. 6 is a graph showing a success rate of map matching.

FIG. 7 is a diagram showing the arrangement of GPS satellites at a certain time.

[Explanation of symbols]

3 azimuth sensor 4 distance sensor 5 road map memory 7 GPS receiver 8 processing device (combination designation means, position acquisition means, correction calculation means)

Claims (2)

[Claims] 1. A vehicle position is estimated using an azimuth sensor and a distance sensor mounted on a vehicle, the estimated vehicle position is compared with the road network data obtained from a road map memory, and the comparison result is compared. On the basis of the above, in a map matching type vehicle position detecting device for detecting a vehicle position in which the existence probability of the vehicle is added to one or more roads, a combination of satellites used for positioning is selected from a plurality of GPS satellites orbiting the orbit. The position specifying means for acquiring the positioning position of the vehicle in the combination of satellites specified by the combination specifying means from the GPS receiver, and the vehicle position obtained by map matching, Correction arithmetic means for correcting using the positioning position acquired by the position acquisition means, wherein the correction arithmetic means specifies the road on which the vehicle is traveling. If so, the combination designating means is instructed to adopt a combination of satellites in which the positioning position of the vehicle supplied from the GPS receiver has a minimum error in the direction in which the road extends. Vehicle position detection device. 2. A vehicle position is estimated using an azimuth sensor and a distance sensor mounted on the vehicle, the estimated vehicle position is compared with the road network data obtained from a road map memory, and the comparison result is compared. On the basis of the above, in a map matching type vehicle position detecting device for detecting a vehicle position in which the existence probability of the vehicle is added to one or more roads, a combination of satellites used for positioning is selected from a plurality of GPS satellites orbiting the orbit. The position specifying means for acquiring the positioning position of the vehicle in the combination of satellites specified by the combination specifying means from the GPS receiver, and the vehicle position obtained by map matching, Correction arithmetic means for correcting using the positioning position acquired by the position acquisition means, wherein the correction arithmetic means specifies the road on which the vehicle is traveling. If not, the combination designating means is instructed to adopt a satellite combination in which the positioning position of the vehicle supplied from the GPS receiver has a minimum error in a direction substantially perpendicular to the direction in which the road extends. A vehicle position detecting device characterized by: