JPH0323487A - On-vehicle navigator - Google Patents

Abstract

PURPOSE:To accurately detect the running direction of a vehicle by correcting outputted data of a geomagnetic sensor after passing through a railroad crossing. CONSTITUTION:The efficiency of outputted data of the geomagnetic sensor 1 is monitored, when the changing rate exceeds a set value, outputted data at the time when changing rate of the outputted data is decreased is taken as corrected data, and compensating the outputted data of the geomagnetic sensor 1 is carried out based on this corrected data. Thus even when a vehicle body is magnetized when it is passed through, the running direction of the vehicle can be accurately detected without carrying out correction of one revolution again.

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 on-vehicle navigation device, the current location is constantly 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 M (or a certain period of time).

As the orientation sensor, a geomagnetic sensor is used that detects the orientation of the vehicle based on geomagnetism (earth's magnetic field). This geomagnetic sensor is easily affected by a disturbance magnetic field, and since the vehicle body is magnetized when the vehicle passes, for example, a railroad crossing, it is no longer possible to accurately detect the running direction due to the influence of this magnetization.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an in-vehicle navigation device that can accurately detect the running direction of a vehicle by correcting output data of a geomagnetic sensor after passing through a railroad crossing.

In the in-vehicle navigation device according to the present invention, the rate of change in the output data of the geomagnetic sensor is monitored, and when the rate of change becomes larger than a set value, the output data at the time when the rate of change in the output data decreases thereafter is monitored. The configuration is such that the output data of the geomagnetic sensor is corrected based on this captured data.

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 Pos1ton1ngSystem)
The detection output of each of these sensors (devices) 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 nonvolatile storage medium such as a CD-ROM, and a writable and readable nonvolatile storage medium such as DAT (digital audio tape) 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 (numerizing) each point on a road on a map. Information stored in this CD-ROM is read by a CD-ROM driver 10. CD-R
The read output of the OM 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 is cut off, the information stored in the RAM 9 immediately before, such as the vehicle's current location coordinates, is stored as backup data in the DAT encoder/
It is stored in the DAT by being supplied to the DAT deck 12 via the decoder 13, and when the vehicle power is turned on, the
The information stored in the AT is read by the DAT deck 12. The read information is sent to DAT encoder/decoder 1
RA by being sent to bus line L via
Stored in M9.

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) that has passed through the accessory switch SW is stabilized by a regulator 15 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
(Video) - A graphic memory 18 consisting of RAM, etc., a graphic controller 19 that draws map data sent from the system controller 5 as image data in the graphic memory 18 and outputs this image data, and this graphic controller. Display 17 based on the image data output from one
It is comprised of a display controller 2o that controls to display a map on the top. The input device 21 consists of a keyboard or the like, and issues various commands and the like to the system controller 5 by the user's keystrokes.

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 (east direction).When the geomagnetic sensor with this configuration is rotated once on a horizontal plane, the output data from both the U and V detection elements is used to detect the geomagnetic component shown in Fig. 2. It is possible to draw a locus of a circle I centered on the origin O of the UV orthogonal coordinate system as shown in the figure. Therefore, for example, the point P(U+, V
+) l: Counterclockwise azimuth θ from the east (V axis) at
can be calculated from the formula: 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 the calculation of equation (1) is performed based on the output data from both the U and V detection elements. By doing this, it is possible to determine the running direction of the vehicle.

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 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 obtained by rotating 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 body magnetization is determined. 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 rmUw. of the outputs U and V of both detection elements. Vw
and the minimum value Uml'l, van, and from these, the coordinates of the center Q are calculated using the following equation (2).

tyo 1 (Ugnx+Um) /2 } ...... (2) Vo 1 (Vmx+Vm)/2 Using the calculated center values UO and VO, the output value U of each magnetic detection element is determined by the following equation (3). , V are corrected, and the direction is calculated from the corrected center value U''V-.

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

Next, the processing procedure for capturing the output data of the geomagnetic sensor, which is executed by the CPU 7 when the vehicle passes a railroad crossing, will be described with reference to the flowchart in FIG. 3. This subroutine recognizes the current location of the vehicle and records map data of a certain area including the current location on a CD-R.
At a predetermined period during the execution of a main routine (not shown) that performs processing such as reading out from the OM and displaying it on the display 17 as a map around the current location of the vehicle, and displaying the exit position indicating the current location of the vehicle on the map. It shall be called and executed every time.

The CPU 7 first imports the output data (hereinafter referred to as sensor data) MX and MY from the geomagnetic sensor (step S31), and then imports the rate of change SY1 of the sensor data MY in the Y direction, for example, among the sensor data MX and MY. The absolute value of the difference between the current value and the previous value of the sensor data MY is calculated (step S32), and after calculating the change rate S
It is determined whether a state determination flag indicating that Y is larger than a first set value THDI, which will be described later, is set (FLG-1) (step S33). In addition,
Among sensor data MX and MY, sensor data M in the Y direction
The reason for determining the rate of change in Y is that the Y direction represents the longitudinal direction data of the vehicle, and when passing through a railroad crossing, the influence of magnetization appears strongly on the longitudinal direction data of the vehicle.

Therefore, if the influence of magnetization can be detected using the sensor data MX in the X direction, it is also possible to determine the amount of change in the sensor data MX.

When entering this routine for the first time, the FLG is 41, so the CPU 7 determines whether the rate of change SY is greater than the first set value THD1 (step S34) and determines that SY>
If it is THDI, it is determined that the vehicle body may have been magnetized due to the vehicle passing through a railroad crossing, and the state judgment flag FLG is set and the sensor data value just before that, that is, the previous sensor data MX, MY, is set. The values are saved as direction data SVM, SVY of the vehicle's current location (step S35), and then the captured sensor data MX,
Set the current value of MY as the previous value (step S3
6). After that, the program returns to the main routine.

If it is determined in step S34 that SY≦THDI,
The program moves directly to step S36.

If this routine is entered in a state where the rate of change SY of the sensor data is greater than the first set value THD1, the CPU 7 determines in step 833 that the rate of change SY of the sensor data is FLG-1, and then determines that the rate of change SY of the sensor data is FLG-1. It is determined whether or not the second set value Tl{D2 has become smaller (step S37), and SY
If <THD2, it is determined that the vehicle has already passed the level crossing and is no longer directly affected by the magnetic field at the level crossing. Normally, the running direction hardly changes before and after passing a railroad crossing, so sensor data before and after passing a railroad crossing can be regarded as data indicating the same running direction. Therefore, the difference between the sensor data before and after passing the railroad crossing, that is, the direction data SVM,S of the current location saved in step S35.
Did you incorporate VY this time? As shown in Figure 4, the difference between the sensor data MX and MY is the deviation amount of the center values MXo and MYo obtained by one-rotation correction at system start-up due to the magnetization of the vehicle body when passing through a railroad crossing. It will be equivalent.

Therefore, when the CPU 7 determines that SY<THD2, the center value MXo. To MY■ (SVM-MX).
(SVY-MY) is added to the new center value MXo.
n, MYon, and the state determination flag is reset (FLG-0) (step S38). After that, the program moves to step S36. Step S37
If it is determined that SY≧THD2, the program directly proceeds to step S36.

Thereafter, in the main routine, the output data of the geomagnetic sensor will be corrected based on the new center values MXon, MYon set in step S38. Therefore, even if the vehicle body is magnetized by passing through a railroad crossing, it is possible to accurately detect the traveling direction without having to perform one-turn correction again.

FIG. 5 is a flowchart showing another processing procedure for correcting sensor data, which is executed by the CPU 7 when the vehicle passes a railroad crossing.

First, the CPU 7 takes in the sensor data MX, MY (
Step S51), then the rate of change S of the sensor data MY
Y is determined (step S52), and it is determined whether the L state determination flag is set (step 953).
, FLG=+1, it is determined whether the vehicle is passing through a railroad crossing (step S54). The fact that a vehicle is passing through a railroad crossing can be detected based on the reception output of a receiver that receives signals from signposts placed near the railroad crossing, or the fact that the vehicle is passing through a railroad crossing can be detected based on the reception output of a receiver that receives signals from sign posts placed near the railroad crossing. Identification can be made by detecting identification data shown in the map data, or by detecting data at the intersection of a road vector and a railroad crossing vector on map data.

If the vehicle is passing through a railroad crossing, the CPU 7 determines whether the rate of change SY of the sensor data MY is greater than the first set value THD1 (step S55), and if SY>THDI,
The vehicle crosses the railroad crossing! It is determined that the vehicle body may have been magnetized due to an accident, and the state determination flag FLG is set.
At the same time, the data θ of the railroad crossing obtained from the map data is saved (step S56), and the current value of the captured sensor data MX, MY is then set as the previous value (step S57). After that, the program returns to the main routine. If it is determined in step S54 that the train is not passing through a railroad crossing, or if it is determined in step S55 that the SY
If it is determined that ≦THDI, the program directly proceeds to step S57.

If it is determined in step S53 that it is FLG-1, the CPU 7 determines that the sensor data change F+ISY is the second
It is determined whether or not it has become smaller than the set value THD2 (step S58), and if SY<THD2, it is determined that the vehicle has already passed the level crossing and the direct influence of the magnetic field at the level crossing has disappeared; Sensor data imported this time MX, M
Y, radius r of the circle determined in advance by one-turn correction
and MX from the orientation data θ saved in step S56
on-MX-r・eosθ} ...... (4) Based on the calculation formula MYon-MY-r-slnθ, calculate new center values MXon and MYon as shown in FIG. 6, and set the state determination flag. Reset (step S59). After that, the program moves to step S57.

If it is determined to be SYkTHD2 with Stesobu 358,
The program moves directly to step S57.

In each of the above embodiments, the driving direction of the overlapping image does not change before and after passing the railroad crossing. However, in rare cases, the running direction of the vehicle may change after passing the railroad crossing.

Therefore, a processing procedure for correcting sensor data that can cope with the case where the running force level of the vehicle changes after passing through a railroad crossing will be explained with reference to the flowchart of FIG. 7.

First, the CPU 7 takes in the sensor data MX, MY (
Step S71), then the rate of change S of the sensor data MY
Y is determined (step S72), and after determining L, it is determined whether the state determination flag is set or not (step 873).
, FLG4], it is determined whether the vehicle is passing through a railroad crossing (step S74). If the vehicle is passing through the railroad crossing, the CPU 7 determines whether the rate of change SY of the sensor data MY is greater than the first set value THD1 (step S75), and if SY>THDI, the vehicle passes the railroad crossing. It is determined that there is a possibility that the vehicle body has become celadon due to this, and the state determination flag FLG is set, and the azimuth data Fθ of the railroad crossing obtained from the map data is saved (step S76), and the steering angle of the vehicle is also set. The vehicle direction change amount data Kθ obtained from the output data of the angular velocity sensor 2 provided as an auxiliary sensor for detecting is saved (step S77), and the current values of the captured sensor data MX and MY are then set as the previous values. (Step S78). After that, the program returns to the main routine. If it is determined in step S74 that the vehicle is not passing through a railroad crossing, or if it is determined in step S75 that SY≦THDI, the program directly proceeds to step 578.

If it is determined in step 573 that it is FLG-1, the CPU 7 selects the sensor data change rate SY or the second set value T.
It is determined whether the size is smaller than HD2 (step S7).
9) If SY<THD2, it is determined that the vehicle has already passed the level crossing and the direct influence of the magnetic field at the level crossing has disappeared, and the level crossing direction data F saved in step 376 is
θ and the vehicle direction change amount data Kθ saved in step S77 are added to obtain corrected azimuth data Jθ (step S77).
80), then the sensor data MX, MY imported this time
, the radius of the circle 'and the corrected orientation data Jθ to MXon-MX - r e cosJ θ}...
(5) Find new center values MXon, MYon based on the calculation formula MYon-MY-r-slnJθ and reset the state determination flag (step S
81). Thereafter, the program moves to step 878. If it is determined in step S79 that it is SYaTHD2, the program moves directly to step S78.

Note that in this embodiment, the angular velocity sensor 2 is used as an auxiliary sensor.
Although the auxiliary sensor is not limited to the angular velocity sensor 2, the key point is to detect the steering angle of the vehicle to obtain the vehicle direction change data Kθ. It is fine as long as it can be done.

Effects of the Invention As explained above, in the in-vehicle navigation device according to the present invention, the rate of change in the output data of the geomagnetic sensor is monitored, and when the rate of change becomes larger than a set value, the subsequent change in the output data is monitored. The output data at the time when the rate decreases is used as correction data, and the output data of the geomagnetic sensor is corrected based on this correction data, so even if the vehicle body is magnetized when the vehicle passes, Even if this happens, the running direction of the vehicle can be accurately detected without having to perform one-turn correction again.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the in-vehicle navigation device according to the present invention, Fig. 2 is a line diagram showing the locus drawn by the output data of the geomagnetic sensor, and Fig. 3 is a block diagram showing the trajectory drawn by the output data of the geomagnetic sensor. A flowchart showing the processing procedure for correction of the output data of the geomagnetic sensor to be executed; FIG. 4 is a diagram showing center value coordinates before and after correction according to the procedure of FIG. 3;
Fig. 5 is a flowchart showing another processing procedure for correcting the output data of the geomagnetic sensor, Fig. 6 is a diagram showing the center value coordinates before and after correction according to the procedure of Fig. 5, and Fig. 7 is a diagram showing the correction of the output data of the geomagnetic sensor. 7 is a flowchart showing another processing procedure for correction. Explanation of symbols of main parts 1... Orientation sensor (geomagnetic sensor) 2...
...Angular velocity sensor 3...Distance sensor 5...
...System controller 10...CD-ROM driver 16...
...Display device 17...Display 2nd picture 3 picture milk 5 picture L Otsu picture brother 6 picture 721

Claims (4)

[Claims] (1) A geomagnetic sensor that detects the running direction of a vehicle, a display means that displays an image according to a supplied display information signal, and a storage medium that stores a plurality of map data groups each corresponding to a plurality of regions. reading means for reading the map data group from the storage medium; and controlling to extract from the storage medium a map data group of a certain range including the current location while recognizing the current location of the vehicle, and displaying the extracted map data group on the display means. An in-vehicle navigation device comprising a control means for displaying a map around the current location of the vehicle by supplying the display information signal as the display information signal, the control means monitoring a rate of change in the output data of the geomagnetic sensor; An in-vehicle navigation device characterized in that the output data at a time when the rate of change decreases is used as correction data, and the output data of the geomagnetic sensor is corrected based on the correction data. (2) The control means holds the output data immediately before the rate of change becomes larger than the first set value as azimuth data of the current location, and the control means holds the output data immediately before the rate of change becomes larger than the first set value, and also holds the output data when the rate of change becomes smaller than the second set value. The in-vehicle navigation device according to claim 1, wherein the output data at a time when the geomagnetic sensor is corrected is corrected data, and the output data of the geomagnetic sensor is corrected based on the corrected data and the azimuth data. (3) When the control means detects that the vehicle is passing through a railroad crossing, the control means obtains azimuth data of the railroad crossing from the map data group, and outputs the geomagnetic sensor based on the azimuth data and the correction data. 2. The in-vehicle navigation device according to claim 1, wherein data is corrected. (4) The in-vehicle navigation device includes an auxiliary sensor that detects the amount of change in the running direction of the vehicle, and when the control means detects that the vehicle is running at a railroad crossing, the control means transmits the azimuth data of the railroad crossing to the The output data of the auxiliary sensor is obtained from a map data group and taken in as vehicle direction change amount data, and the output data of the geomagnetic sensor is corrected based on the correction data, the azimuth data, and the vehicle direction change amount data. The in-vehicle navigation device according to claim 1.