JPH0317686A - On-vehicle navigation device - Google Patents

Abstract

PURPOSE:To make more accurate corrections and to perform accurate current position recognition by confirming that the output of an earth magnetic sensor is stable and then correcting the output of the earth magnetic sensor according to its stable output and azimuth information. CONSTITUTION:A CPU 7 finds angle information thetas from the azimuth information which is inputted by a driver and then inputs output data MX and MY of an azimuth sensor (earth magnetic sensor) 1. When it is decided that the sensor data MX and MY are stable, the CPU 7 finds the mean coordinate values MXm and MYm of the sensor data MX and MY which are inputted a specific number of times and then finds new center values MXon and MYon from the coordinate values MXm and MYm, the radius R0 of a circle, and the angle information thetas. Then the CPU 7 uses the new center values MXon and MYon to perform azimuth detection based upon corrected center values while correcting the sensor data, and then corrects the center values.

Description

[Detailed description of the invention] Technical field The present invention relates to an on-vehicle navigation device.

BACKGROUND ART In recent years, map data including road data obtained by digitizing each point on a road on a map is stored in a storage medium such as a CD-ROM, and the current location of a vehicle can be recognized and a certain range including the current location can be stored. An in-vehicle navigation device has been developed and put into practical use that reads map data of the area from a storage medium and projects it on the display as a map of the area around the vehicle's current location, and automatically displays the position of the own military, which indicates the vehicle's current location, on the map. It's coming.

Such an in-vehicle navigation device is configured to use a direction sensor to determine the running direction of the vehicle, and a distance sensor to determine the running distance of the vehicle, and to estimate the current location of the vehicle on a map from the running direction and distance. here,
Both the direction data and distance data obtained by the direction sensor and distance sensor usually contain an error of about several percent, so the current location of the vehicle estimated from these data will inevitably have an error with respect to the actual traveling position. Become what you have.

For this reason, in the vehicle-mounted navigation device, the current location is always corrected by a so-called map matching process that draws the current location of the vehicle onto nearby roads every time the vehicle travels a certain distance (or for a certain period of time).

By the way, as a direction sensor, a geomagnetic sensor that detects the direction of a vehicle based on geomagnetism (earth magnetic field) is known. This geomagnetic sensor is easily affected by a disturbance magnetic field, and cannot detect accurate orientation due to the influence of magnetization of the vehicle body when the vehicle passes, for example, a railroad crossing.

In such a case, the output data of the geomagnetic sensor is corrected. However, if this correction processing is not sufficient or if you drive on a road for which there is no map data, you will be driving for a long time without finding any road segments nearby, and during that time, of course, the map matching process will be performed. Since this is not done, the current location will deviate significantly from the actual driving position and become inaccurate.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an in-vehicle navigation device that can cope with errors in recognizing the current location of a vehicle.

In the in-vehicle navigation device according to the present invention, while recognizing the current location of the vehicle, a group of map data of a certain area including the current location is read from the storage medium and displayed as a map around the current location of the vehicle on the display together with the current location, Obtain road segments near the current location based on road data of a map data group of a certain area, calculate the distance to the neighboring road segment and the angle of the neighboring road segment, and obtain the distance and angle under predetermined conditions. When the above conditions are satisfied, the current location of the vehicle is corrected to a nearby road segment, and when there is no nearby road segment whose distance and angle satisfy the above conditions for a predetermined travel distance or a predetermined travel time, the current location of the vehicle is In addition to displaying that the current location based on recognition is inaccurate, input command information that commands correction input of the vehicle's current location and orientation is displayed, and when orientation information is input according to this input command information, the geomagnetic sensor's After confirming that the output is stable, the output of the geomagnetic sensor is corrected based on the stable output and azimuth information.

Example Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a block diagram showing an embodiment of an in-vehicle navigation device according to the present invention. In the figure, 1 is a direction sensor for detecting the running direction of the vehicle, 2 is an angular velocity sensor for detecting the angular velocity of the vehicle, 3 is a distance sensor for detecting the distance traveled by the vehicle, and 4 is latitude and longitude information. GPS (
Global System)
The detection output of each sensor (device) is supplied to the system controller 5.

As the direction sensor 1, for example, a geomagnetic sensor is used that detects the running direction of the vehicle using geomagnetism (earth's magnetic field).

The system controller 5 receives the detection outputs of the sensors (devices) 1 to 4 as input and processes them such as A/D (analog/digital) conversion. A CPU (Central Processing Circuit) that calculates the vehicle's travel distance, travel direction, current location coordinates (longitude, latitude), etc. based on the output data of each sensor (device) 1 to 4.
7, a ROM (read-only memory) 8 in which various processing programs and other necessary information for the CPU 7 are written in advance, and a RAM (random memory) in which information necessary for executing programs is written and read.・Access memory) 8.

As the external storage medium, a read-only non-volatile storage medium such as a CD-ROM, and a writable and readable non-volatile storage medium such as DAT (Digital Audio Data) are used. In addition,
The external storage medium is not limited to CD-ROM or DAT, but it is also possible to use a nonvolatile storage medium such as an IC card. The CD-ROM stores in advance map data obtained by digitizing (digitizing) each point on a road on a map. Information stored in this CD-ROM is read by a CD-ROM driver 10. CD
- The read output of the ROM driver 10 is decoded by the CD-ROM decoder 11 and sent to the bus line L.

On the other hand, the DAT is used as a so-called backup memory, and information is recorded or read by the DAT deck 12. When the vehicle power supply is cut off, information such as the current position coordinates of the vehicle stored in the RAM 9 immediately before is supplied to the DAT deck 12 via the DAT encoder/decoder 13 as backup data, and is stored in the DAT. DA when inputting
The stored information of T is read out by the DAT deck 12. The read information is DAT. x encoder/decoder 1
3 to the bus line L via l7.
It is stored in AM9.

Turning the vehicle power on and off is detected by a detection circuit 14 that monitors the output level of a so-called accessory switch SW of the vehicle. Vehicle power from a battery (not shown) via an accessory switch SW is stabilized by a regulator 5 and supplied as power to each part of the device. Due to the time constant of the circuit, the output voltage of the regulator 15 does not fall instantaneously when the accessory switch SW is turned off, and backup data is stored in the DAT as a backup memory during this falling period.

When the vehicle is running, the CPU 7 calculates the running direction of the vehicle based on the output data of the direction sensor 1 at a predetermined period by a timer interrupt, and calculates the running distance and The vehicle's current location coordinates are determined from the driving direction, map data of a certain area including the current location coordinates is collected from the CD-ROM, and the collected data is stored in the RAM as a buffer memory.
9 and supplies it to the display device 16.

The display device 16 includes a display 17 such as a CRT, and a V
mdeo)-RAM, etc.; a graphics controller that draws the map data sent from the system controller 5 as image data in the graphic memory 18 and outputs this image data; and from this graphic controller 19. The display controller 20 controls display of a map on the display 17 based on output image data. The input device 21 includes a keyboard or the like, and issues various commands and the like to the system controller 5 through key input by the user.

FIG. 2 shows an example of the arrangement of various operation key groups in the input device 21, and the operation keys are arranged in four directions of the screen, up, down, left, and right of the cursor (not shown) displayed on the display 17. The cursor keys 22υ, 22D, 22L, and 22R of 4gJ give commands to move to , the set key 24 gives commands to reset the ambiguous flag and ambiguous counter, or to correct the current position and direction, which will be described later, and the set key 24 gives commands only to correct the current position. It consists of a clear key 24.

Next, the flowchart in FIGS. 3A and 3B describes the processing procedure executed by the CPU 7 when it is revealed that the current location based on the vehicle's current location recognition is ambiguous (inaccurate). Explain according to Yat. It is assumed that this subroutine is called and executed every time the vehicle travels a certain distance M (or a certain period of time) during the processing of the main routine (not shown). Further, it is assumed that a map of a certain area centered on the current location of the vehicle is displayed on the display l7.

The CPU 7 first obtains the coordinates Ps (Xs.Ys) of the current location based on the output data of the distance sensor 3, and further determines the traveling direction θS based on the output data of the direction sensor 1 (step S1), and then calculates the coordinates Ps (Xs.Ys) of the current location based on the output data of the direction sensor 1 (step S1). As shown, the distance Na to the point Pa (Xa.Ya) on the road segment near the current location and the angle θa of that line segment are determined (step S2), and then the determined distance AtlEIIa is less than or equal to the predetermined value n th. and the deviation of the driving direction of the current location with respect to the nearby road segment, that is, 1θS
It is determined whether the condition that θa1 is equal to or less than a predetermined value θth is satisfied (step S3).

The road line near the current location meets the above conditions, that is, Na5R th
and satisfies the condition 1θS-θa 1≦θth, the CPU 7 determines the current location as a point Pa(Xa
．． Ya) (step S4), and then reset an ambiguity counter, which will be described later (step S5). If the road segment near the current location does not satisfy the above conditions, it is determined that the current location based on current location recognition may be ambiguous, and the count value N of the ambiguity counter that counts the number of times this determination is made is incremented ( Step S6
), then it is determined whether the count value N is greater than or equal to a predetermined value Nth (step S7). If NaNth, the CPU 7 determines that the current location based on current location recognition is ambiguous, and sets an ambiguity flag (step S
8).

After resetting the ambiguity counter in step S5, determining that N<Nth in step S7, or setting the ambiguity flag in step S8, the CPU 7 determines whether the ambiguity flag is set (
Step S9). If the ambiguity flag is not set, the program returns to the main routine. If the ambiguity flag is set, CPU 7
The display device 16 is controlled to display on the screen 7 that the current location is ambiguous (step SIO).

On the display 17, along with a map of a certain range of areas centered on the current location, as shown in Figure 45, the own army mark, direction mark, and a circle with a fixed radius centered on the own army position are displayed, and the step SIO , the display color of a circle that is normally displayed in yellow, for example, is changed to, for example, red to indicate that the current location is ambiguous. Note that the display that the current location is ambiguous is not limited to this display method, and various methods such as displaying a message on the display 17 are possible.

After displaying that the current location is ambiguous, the CPU
7 controls the display device 16 to display a message on the display 17 to instruct the driver to input the current location and direction of the vehicle (step S11), and then key input for inputting the current location and direction. (step S12). When a message instructing the input of the current location and direction is displayed on the display 17, the driver actually moves the vehicle to a location where the location can be easily confirmed on the map displayed on the display 17, and inputs the current location and direction at that location. You will need to input the direction.

This input is performed by key input using the operation key group shown in FIG. 2 so that the own army mark on the display 17 is located at the current location on the map and the orientation mark matches the road orientation at that location. The processing procedure associated with the key input will be shown below.

When determining that there is a key input in step S12, the CPU 7 first determines whether the input key is the set key 23 (step S13), and if it is a set key input, resets the ambiguity flag and the ambiguity counter (step S13). S14), followed by erasing the message for inputting the current location and direction and the display indicating that the current location is ambiguous (step S15). After that, the program returns to the main routine. If the input key is not the set key 23, the CPU 7 uses the cursor keys 22U, 22D, 22L.
, 22R (step S16).

If there is a cursor key input, the CPU 7 moves a cursor (not shown) indicating the position of the own army displayed on the display 17 relative to the displayed map (actually, the map The display device 16 is controlled to cause the display to be executed (by scrolling) (step S17), and then key input is monitored again (step S18). If there is a cursor key input again (step S19), the program returns to step S17 and repeats the process of changing the cursor position according to the key input.

Subsequently, the CPU 7 determines whether the key input after the cursor key input is a set key input (step S2).
0), if it is not a set key input, it is determined whether the key input is a clear key input (step S21).

If there is no clear key input, the program goes to step 3.
Returning to step 18, the above-described process is repeated. If it is a clear key input, the vehicle position on the map is corrected to the cursor position (step S22). After that, the program returns to the main routine. That is, by inputting the clear key after completing the cursor key input, only the process of correcting the current location is performed.

If it is determined in step S20 that a set key input has been made, the CPU 7 corrects the vehicle position on the map to the cursor position (step S23), and then waits for a key input (step S24). If there is a key input, the CPU 7 determines whether the input key is a cursor key (step S
25) If the key input is one input, the direction mark is rotated counterclockwise in the case of the left cursor key 22L and clockwise in the case of the right cursor key 22R according to the key input. The display device 16 is controlled (step S26). After completing the direction input using the cursor keys, the CPU
7 determines whether the subsequent key input is a set key input (step S27).

If the set key is not input, the program goes to step S24.
Return to and repeat the above process. If it is a set key input, the CPU 7 executes direction correction processing (step S2
8) After completing L, the program returns to the main routine. That is, by inputting the set key after the end of the force to Kasoluki, the process moves to a processing routine that corrects the current location and direction.

Therefore, when a geomagnetic sensor is used as the direction sensor 1, if it is determined that the current location is ambiguous after passing through a railroad crossing, it is assumed that the current location has become ambiguous due to inaccurate correction processing of the output data of the geomagnetic sensor. All you have to do is make a judgment and perform a key operation to enter this processing routine.

Here, a method of determining the running direction of the vehicle when a geomagnetic sensor is used as the direction sensor 1 will be explained. A geomagnetic sensor generally consists of a pair of magnetic detection elements arranged on the same plane with a phase angle of 90° to each other, one of these elements detects the geomagnetic component in the U direction (north direction), for example, and the other detects the geomagnetic component in the U direction (north direction). It is designed to detect the geomagnetic component in the V direction (eastward direction). When a geomagnetic sensor with such a configuration is rotated once on a horizontal plane, the output data from both the U and V detection elements generates a circle I centered on the origin O of the UV orthogonal coordinate system, as shown in FIG. You can draw a trajectory. Therefore, the example point P(U+,
The counterclockwise azimuth θ from the east (V axis) at V+)l: can be calculated from the following equation: θ-tan→(U/V)--(1).

Therefore, such a geomagnetic sensor is attached to a vehicle at a predetermined angle with respect to the longitudinal or lateral direction of the vehicle, and based on the output data from both the U and V detection elements (
By calculating the equation 1), the running direction of the vehicle can be determined.

By the way, ideally, only magnetic flux due to the earth's magnetic field exists around a geomagnetic sensor, but in a vehicle,
Generally, there is extra magnetic flux due to magnetization of the body steel plate. Therefore, a method (for example, see Japanese Unexamined Patent Application Publication No. 57-28208) is adopted in which accurate direction detection is performed by removing the influence of magnetization of the vehicle body. In this method, when the U and V magnetic detection elements are fixed to the vehicle and there is no relative displacement between them, the center of a circle drawn by plotting the output that is produced by turning the magnetic detection elements once, Considering that the distance from the coordinate origin is due to the influence of body magnetization, the output data obtained from both detection elements is corrected so that the center of the drawn circle moves to the origin, and the body magnetization is adjusted. We are trying to remove the influence of magnetism.

To be more specific, the center Q of the circle drawn by the outputs of both detection elements is located at a position moved from the origin, as shown in FIG. Therefore, the maximum value Uw of the outputs U and V of both detection elements is determined. ,vlI
IllX and min fif! The U mn , V system is obtained, and from these the coordinates of the center Q are calculated using the following equation (2).

Uo = (Umx+Umn) / 2} ・・・・・・
・ (2) Vo = (Vmx+Vmn) / 2Using the calculated center value UO,v(,), the output values U and V of each magnetic detection element are corrected by the following equation (3), and the corrected center value The direction is calculated from U- and V-.

U-U-Uo } ...... (3) V--V-V
0 Note that the center values UO, vo and radius r are determined in advance by so-called one-turn correction at the time of starting up the system, that is, by rotating the vehicle equipped with the geomagnetic sensor once.

Next, a subroutine for processing direction correction will be explained with reference to the flowchart of FIG.

The CPU 7 obtains angle information θS from the azimuth information input by the driver in the process of step S25 in FIG. 3B (step S71), and then calculates the output data of the azimuth sensor (geomagnetic sensor) 1 (hereinafter referred to as sensor data). )
MX, MY are imported (step S72), and then whether or not the sensor data MX, MY are stable is determined by checking whether the difference between the current value and the previous value of the imported sensor data MX, MY is consecutive for a predetermined number of times. A determination is made based on whether or not it is below a certain value (step S73). Sensor data MX
, MY are stable, the CPU 7 calculates the average coordinate value M X of the sensor data MX, MY that has been captured a predetermined number of times II. Find M Y ta (step S74
), then these coordinate values M X ti , M Y m,
Based on the radius Ro of the circle and the angle information θS, a new center value M X on, MYo as shown in FIG.
Find n (step S75).

MXon-MXa-Ro ◆ COSθS} ・
... (4) MYon-MYs -Ro ◆ sin θS,
The radius Ro of the circle is determined in advance by one rotation capture at the time of system startup. Next, CPU 7 uses a new center value MXo instead of the previous center values MXo and MYo.
While correcting the sensor data using n and MYon, the direction is detected from the corrected center value (step S7
6) Then, a center value correction process is executed (step S77).

After that, the program returns to the main routine.

Next, a subroutine for center value correction processing will be explained with reference to the flowchart of FIG. In addition,
This process is performed to confirm whether the center value is accurate, as there is a risk of incorrect correction if the center value is corrected in one go based on the direction information manually input by the driver. It is done.

The CPU 7 first calculates the angle θ- of the road line segment at the current location on the map data (step S91), then imports the sensor data MX, MY (step S92), and then immediately calculates the current angle θ- of the road line segment. Determining whether the difference between the value and the previous value is less than a certain value (step 593), and whether the difference between the current value and the previous value is less than a certain value for each of sensor data MX and MY (steps S94, S95) Do the following. If both conditions are satisfied, the CPU
7 increments the determination counter (step S96).
), then it is determined whether the count value N is greater than or equal to a predetermined value Nth (step S97). If N<Nth, the program returns to step S91.

If N≧Nth, the CPU 7 uses the sensor data MX, M
Y, the radius Ro of the circle, and the angle information θ Akebono, find the center values M X o and M Y o based on the equation (4) above (
Step 398), then the standard deviation σ of the center values MXo and MYo is determined (step S99), and it is determined whether this standard deviation σ is less than or equal to a predetermined value σth (step SI
OO), if σ≦σth, the current values of the angle information θ1 and sensor data MX, MY are set as the previous values, and the determination counter is reset (step SIOI), and after completing L, the program returns to step S91. Steps S93 to S9
5's? If any of the conditions is not satisfied, the program moves directly to step S101. Step S
100 and it is determined that σ≦σth, the CPU
Step 7 calculates the average of the center values MXo and MYo and uses this as new center values M X o and M Y (step S102).

Effects of the Invention As explained above, in the in-vehicle navigation device according to the present invention, while recognizing the current location of the vehicle, a group of map data of a certain area including the current location is read out from the storage medium. Displayed as a map around the current location along with the current address, road segments near the current location are obtained based on the road data of the map data group of a certain area, and the distance to the neighboring road segment and the neighboring road segment are displayed. , and when the distance and angle satisfy a predetermined condition, the current location is corrected to the neighboring road segment, and the neighboring road segment for which the distance and angle satisfy the condition is a predetermined mileage distance or If the vehicle does not exist for a predetermined running time, it displays a message that the vehicle's current location based on current location recognition is ambiguous (inaccurate), displays information that instructs input to correct the vehicle's current location and direction, and responds accordingly. When azimuth information is input, after confirming that the output of the geomagnetic sensor is stable, the output of the geomagnetic sensor is corrected based on the stable output and the azimuth information.

As a result, if the current location of the vehicle is determined to be ambiguous after passing through a railroad crossing, etc. or after driving on a road with no map data, the driver can make one-turn correction by searching for a large area and turning the vehicle once. This means that the output of the geomagnetic sensor can be corrected simply by inputting current location information and azimuth information. In particular, after confirming that the output of the geomagnetic sensor is stable, the stable output is used to correct the output of the geomagnetic sensor, which enables more reliable correction and more accurate current location recognition. It turns out.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a block diagram showing an embodiment of an in-vehicle navigation device according to the present invention, FIG. 2 is a diagram showing an example of the arrangement of operation keys in an input device, and FIGS. 3A and 3B are A flowchart showing the processing procedure when it is detected that the current location is ambiguous by vehicle current location recognition. FIG. 4 shows the coordinates Ps (Xs, Ys) of the current location, the driving direction θS, and the point P a on the nearby road line Distance Ml to (X a. Y a)
)a and the line segment angle θa, Figure 5 is a diagram showing an example of the structure of the display screen showing the vehicle's position and driving direction, and Figure 6 is drawn by the output data of the geomagnetic sensor. A line diagram showing the locus, Fig. 7 is a flowchart showing the processing procedure for direction correction, Fig. 8 is a diagram showing the relationship between the old center value coordinates and new center value coordinates, and Fig. 9 shows the processing procedure for center value correction. FIG. Explanation of symbols of main parts 1... Orientation sensor 3... Distance sensor 5... System controller 10... CD-ROM driver 16...
... Display device 17 ... Display younger brother 2
Figure 4.4 Inkoho 5 Figure Mirozu■ Hou 8 Figure 7 Figure 7, Figure q

Claims (2)

[Claims] (1) A geomagnetic sensor that detects the running direction of the vehicle, an input means that inputs the vehicle's current location information and direction information, a display means that displays an image according to the supplied display information signal, and road lines on the map. a reading means for reading a plurality of map data groups from a storage medium storing a plurality of map data groups including road data obtained by digitizing each point on the road and corresponding to a plurality of regions, and recognizing the current location of the vehicle. At the same time, the map data group of a certain area including the current location is controlled to be extracted from the storage medium, and the extracted map data group and current location information are supplied to the display means as the display information signal to display information around the current location of the vehicle. a control means for displaying a map and the current location, the control means obtains road segments near the current location based on road data of the map data group of the area in the certain area, and calculates the distance to the neighboring road segment and its distance. An in-vehicle navigation device configured to determine the angle of a nearby road line segment, and control the display means to correct the current location onto the nearby road line segment when the distance and angle satisfy predetermined conditions, The control means displays an indication that the current location based on the current location recognition of the vehicle is inaccurate when a nearby road segment whose distance and angle satisfy the conditions does not exist for a predetermined travel distance or a predetermined travel time. , supplying a display information signal to the display means to display input command information for commanding correction input of the current location and orientation of the vehicle, and the current location information and orientation information are input from the input means in accordance with the input command information. In this case, the in-vehicle navigation device is characterized in that, after confirming that the output of the geomagnetic sensor is stable, the output of the geomagnetic sensor is corrected based on the stable output and the azimuth information. (2) The control means determines that the output of the geomagnetic sensor is stable when the difference between the current value and the previous value of the output of the geomagnetic sensor is less than or equal to a predetermined value for a predetermined number of times. The in-vehicle navigation device according to claim 1.