JPH01301111A - Car navigation system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an in-vehicle navigation system, and in particular, corrects the map information of the driving trajectory, so-called map matching, even when driving in a place with large geomagnetic disturbances. This invention relates to an in-vehicle navigation system that enables navigation.

(Prior Art) As a conventional vehicle-mounted navigation system, there is one described in Japanese Patent Laid-Open No. 191083/1983.

According to the publication, the travel distance Δl is calculated from the number of pulses N obtained from the wheel rotation angle detector and the travel time Δt,
The direction change Δθ of the automobile is determined from the travel distance Δ1 and the rotation angle φ of the steering wheel using the following equation.

Δθ−k′ tanφ・Δ1 (k is a proportionality constant) Then, add the azimuth change Δθ to the initial azimuth θ,
A new orientation θ is required.

In addition, if the vehicle is equipped with a geomagnetic azimuth sensor, the calculation of the azimuth change Δθ and the addition calculation of θ - θ + Δθ are omitted, and the azimuth itself detected by the geomagnetic azimuth sensor is adopted as the new azimuth θ. has been done.

Then, the current direction θ obtained by one of the above methods and the current position (x,
By comparing and correcting y) with map information,
The travel trajectory is corrected on the map, ie, map matching is performed.

(Problems to be Solved by the Invention) As mentioned above, in conventional navigation systems, pulses obtained from the wheel rotation angle detector and the rotation angle φ of the steering wheel are used to calculate the current direction. but,
This method has the problem that calculations are complicated and errors are large, or map matching errors are likely to occur.

In addition, the method of obtaining absolute orientation information using a geomagnetic orientation sensor has the advantage that the device is inexpensive, but the geomagnetic orientation sensor is vulnerable to disturbances in the earth's magnetic field, and data is often offset under elevated tracks, tunnels, railroad crossings, etc. This will disturb the values. As a result, it has been reported that incorrect map matching occurs when passing through similar-shaped roads such as two-way intersections and parallel roads.

An object of the present invention is to eliminate the problems of the conventional in-vehicle navigation system described above, and to provide a system that is inexpensive, has little error, and can perform navigation and map matching reliably even when passing through areas with turbulent geomagnetism. The goal is to propose the following.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides node information,
an adjacent node table consisting of adjacent node information, nodes, and flags representing geomagnetic conditions between adjacent nodes; means for determining the presence or absence of the flag; The present invention is characterized in that it includes means for selecting one of the orientation sensors that is not affected.

(Operation) In the present invention, the flag is read from the adjacent node table while the automobile is traveling. For example, when the flag is not set, it is determined that there is no disturbance in the geomagnetic direction and the azimuth information from the geomagnetic direction sensor is used.On the other hand, when the flag is set, it is determined that there is a disturbance in the geomagnetic direction, and the direction information from the geomagnetic direction sensor is used. Direction information from a direction sensor that is not affected by disturbances is used.

This allows accurate navigation and map matching even when passing through a point where geomagnetic disturbances are expected.

(Example) The present invention will be described in detail below with reference to the drawings.
“ FIG. 2 shows a hardware configuration diagram of an in-vehicle navigation system to which the present invention is applied.
, receives sensor data from the steering angle sensor 40, respectively. Further, a road data storage device 60 such as a floppy disk or a compact disk stores vector data, place name data, etc. related to roads.

The arithmetic processing unit 10 uses the road data, place name data, etc. to display a road map on an image display device 70 such as a CRT or a liquid crystal display board, and uses the vehicle travel trajectory obtained from the sensor data as vector data. The image display device 70 is superimposed. Further, the arithmetic processing device 10 receives and receives commands input by the user from the operation means 80.

Next, one embodiment of navigation according to the present invention will be described below.

Figure 3 is an example of a road. The road is vector AB, BC
, CD, and the vector BC is a tunnel.

FIG. 4 is an example of the road vector data shown in FIG. 3 in a table. Hereinafter, this table will be referred to as an adjacent node table. The adjacent node table shows the status of the adjacent nodes, and the leftmost data is the X and Y coordinates of the node at the current location. The next data is ((X-coordinate, Y-coordinate of adjacent node), (Geomagnetic disturbance presence/absence flag))... This is repeated. The geomagnetic disturbance presence/absence flag is set to "0" when there is no geomagnetic disturbance, and to "1" when there is geomagnetic disturbance.

In addition, the geomagnetic disturbance 15 no flag will be simply referred to as a flag below.

In the adjacent node table, for example, in the first row, the adjacent node of node A is B, and the flag of vector AB is 01.
In other words, there is no disturbance in the earth's magnetic field in vector AB. Further, the second line indicates that the adjacent nodes of node B are A and C, the flag of vector BA is 0, and the flag of vector BC is 1. In other words, this indicates that there is a disturbance in the geomagnetic field in the vector BC.

Similarly, the third line shows that the adjacent nodes of node C are B and D, the flag of vector CB is 1, and the flag of vector CD is 0, and the fourth line shows that the adjacent nodes of node D are C, indicating that the flag of vector DC is 0.

Note that the adjacent node table in Figure 4 is the simplest example for a single road as shown in Figure 3, and it may consist of a much larger number of data in the case of a complex road including three-way, four-way intersections, etc. Of course.

Next, the operation of this embodiment will be explained with reference to FIG. FIG. 5 is a flowchart showing the operation of the arithmetic processing device 10 of FIG. 2 according to this embodiment.

The explanation will now be made assuming that the car travels in the order of nodes A, B, C, and D in FIG. The arithmetic processing means IO firstly
The user inputs the current position commanded from the operating means 80 (steps S], ). Let this current position be node A. Next, the geomagnetic direction sensor 30 is read to determine the direction in which the vehicle is traveling (step S2). Next, an adjacent node is searched based on the current position and the orientation (step S3). The neighboring node becomes node B.

Subsequently, it is determined whether the flag of vector AB is 1 or 0 (step S4). In this embodiment, the flag is 0,
In other words, since there is no disturbance in the geomagnetic field between nodes AB, the process proceeds to step S5, and the arithmetic processing unit executes the geomagnetic direction sensor 3.
A signal of 0 is read (step S5). Next, the signal from the vehicle speed sensor 20 is read and the travel distance is determined (step S6). Next, the current position is updated from the direction determined in step S5 and the travel distance determined in step S6 (step S?). Next, it is determined whether the vehicle has passed through vector AB (step S8), and if it has not passed yet, step S4 or step S5. Sδ, return to S7,
Update current location.

In step S8, if it is determined that the vehicle has passed vector AB (step S8 is YES), that is, in the case of this embodiment, if it is determined that the vehicle has passed node B, it is determined whether or not to stop the navigation. A determination is made (step S9), and if it is to continue, the steps S2 and 33 are performed.
Returning to , the search for the next adjacent node is performed by referring to the adjacent node table of FIG. In this embodiment, the nodes A and C are adjacent to node B, and the adjacent node is determined to be C based on the direction obtained from the geomagnetic direction sensor.

Next, it is determined in step S4 whether the flag of vector BC is 1 or 0, and if the flag is 1, step SIO
Then, the direction is read from the steering angle sensor 40. Then,
Step S6. S7. 38, and the same processing as above is performed. The subsequent operations until reaching node D are the same as those described above, so detailed explanations will be omitted.

In the flowchart of FIG. 5, when step S8 is NO, the process may return to step S6. Further, steps S8 and 89 may be interchanged. Furthermore, when step S9 is NO, the process may return to step S3 and an adjacent node may be selected based on the direction obtained from the geomagnetic direction sensor or the steering angle sensor.

As described above, according to this embodiment, the azimuth is determined by switching between the geomagnetic azimuth sensor and the steering angle sensor, and the current position is updated from the azimuth and the travel distance determined by the vehicle speed sensor. This has the effect of making navigation possible even in places where the earth's magnetic field is disturbed.

Note that, of course, a vibration gyro, a /X steering angle sensor, etc. may be used instead of the steering angle sensor.

Next, a functional block diagram of the present invention will be explained with reference to FIG. In the figure, 11 is a mileage calculating means, 12 is a current position updating means, 13 is a vector passage determining means, 14 is an adjacent node searching means, 15 is an adjacent node table, 16 is a flag determining means, and 17 is a sensor selecting means. , other symbols indicate the same as or equivalent to those in FIG. Here, the adjacent node table 15 may be provided in the road data storage device 60 of FIG. 2, or may be provided in the arithmetic processing device 10.

In FIG. 1, first, the current position is input from the current position input means 80 to the current position updating means 12 and the adjacent node searching means 14. The adjacent node search means 14 accesses the adjacent node table 15 based on the current position and the direction f5 from the geomagnetic direction sensor 30. As a result, an adjacent node and a flag are determined, and the adjacent node is sent to the current position updating means 12 and the vector passage determining means 13, while the flag is sent to the flag determining means 16.

The flag determining means 16 sends a control signal to the sensor selecting means 17, and when the flag is 0, the geomagnetic direction sensor 30 is selected, and when the flag is 1, the steering angle sensor 40 is selected.

The current position updating means 12 obtains azimuth information from the sensor selected by the sensor selection means 17, and also obtains distance information from the traveling distance calculation means 11, and updates the current position.

The vector passage determining means 13 compares the updated current position with the adjacent node and determines whether the vehicle has passed through the adjacent node. When it is determined that the adjacent node has passed, the adjacent node search means 14 accesses the adjacent node table 15 and further searches for the next adjacent node.

As described above, since the present invention is provided with the adjacent node table 15, the flag discrimination means 16, and the sensor selection means 17, the steering angle sensor 40 can be used in places where the earth's magnetic field is disturbed. Accurate navigation is possible no matter where you are.

Note that the functional block diagram in FIG. 1 shows only one example, and the present invention is of course not limited thereto.

(Effects of the Invention) According to the present invention, a geomagnetic azimuth sensor is used in places where there is no geomagnetic disturbance, and a sensor that is not affected by the geomagnetic disturbance, such as a steering angle sensor or a vibration gyro, is used in a place where there is geomagnetic disturbance. Since the direction in which the vehicle is traveling can be determined using the directional sensor, it is possible to perform reliable navigation in large cities where there are many tunnels, railroad crossings, and elevated roads. It has the effect of drastically reducing

Furthermore, the present invention has the advantage that it is possible to perform more accurate map matching with less cumulative error than a navigation method using only a sensor for determining relative changes such as a steering angle sensor.

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram of the present invention, FIG. 2 is a hardware configuration diagram to which the present invention is applied, FIG. 3 is a diagram showing an example of a road on which a car travels, and FIG. 4 is an example of an adjacent node table. FIG. 5 is a flowchart showing the operation of an embodiment of the present invention. DESCRIPTION OF SYMBOLS 10... Arithmetic processing device, 12... Current position update means, 13... Vector passage determination means, 14... Adjacent node search means, 15... Adjacent node table, 16.
...Flag discrimination means, 17...Sensor selection means, 20
... Vehicle speed sensor, 30 ... Geomagnetic direction sensor, 40
...Rudder angle sensor representative patent attorney Michito Hiraki and 1 other person Figure 2

Claims (2)

[Claims] (1) In an in-vehicle navigation system that includes at least a geomagnetic azimuth sensor, a directional sensor that is not affected by geomagnetic disturbances, and a vehicle speed sensor, node information, adjacent node information, and geomagnetic states between nodes and adjacent nodes. an adjacent node table consisting of a flag representing the flag, a means for determining the presence or absence of the flag, and a sensor selection for selecting one of the geomagnetic azimuth sensor and an azimuth sensor unaffected by geomagnetic disturbances depending on the presence or absence of the flag. An in-vehicle navigation system comprising: means for updating a current position based on azimuth information obtained from a sensor selected by the sensor selection means and information obtained from the vehicle speed sensor. (2) The vehicle-mounted device according to claim 1, wherein the azimuth sensor that is not affected by geomagnetic disturbances is any one of a steering angle sensor, a vibration gyro, and a steering wheel angle sensor. navigation system.