JPH0323490A - On-vehicle navigator - Google Patents

Abstract

PURPOSE:To detect any abnormality in outputted data by finding the first running direction based on the outputted data of a geomagnetic sensor and the second running direction based on outputted data of GPS device, and when the observed absolute value of difference in directions exceeds a specified value, judging that the outputted data of the geomagnetic sensor is abnormal. CONSTITUTION:Sensor direction based on the outputted data of the geomagnetic sensor 1 and GPS direction based on outputted data from the GPS device 4 are each sought, the absolute value of the difference in directions of each detected direction is monitored, and when this absolute value of the difference in directions exceeds the specified value, judgement is carried out to decide that the outputted data from the geomagnetic sensor 1 is abnormal. Thus, when the vehicle body is magnetized by the vehicle passing through a railroad crossing, and the outputted data of the geomagnetic sensor is abnormal due to that, this fact can be detected accurately.

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 that reads a group of map data from a storage medium from a storage medium and displays it on a display as a map of the area around the vehicle's current location, and also displays the position of the own military, which indicates the vehicle's current location, on the map in white motion, and is put into practical use. It is becoming more and more popular.

Such in-vehicle navigation devices are 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 the 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 necessarily be different from the actual driving position. Therefore, there will be an error. 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 susceptible to disturbance magnetic fields, and the vehicle body is magnetized when the vehicle passes, for example, a railroad crossing, so that it is no longer possible to accurately detect the running direction due to the influence of this magnetization.

SUMMARY OF THE INVENTION Therefore, one object of the present invention is to provide an on-vehicle navigation device that can detect an abnormality in the output data of a geomagnetic sensor after a vehicle passes a railroad crossing.

In the car carpet navigation device according to the present invention, the first driving direction is determined based on the output data of the geomagnetic sensor.
The second traveling direction is determined based on the output data of the PS device, the absolute value of the difference in direction of each of these traveling directions is monitored, and when the absolute value of the difference in direction exceeds a predetermined value, the output data of the geomagnetic sensor is The system is designed to determine that there is an abnormality.

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 Positioning System restoration)
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 connects to an interface 6 which processes the detection outputs of each sensor (device) 1 to 4 manually and processes such as A/D (analog/digital) conversion, and processes various image data and sequentially sends the data from the interface 6. A CPU (central processing unit) 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 and a ROM (read-only) in which various processing programs and other necessary information for the CPU 7 are written in advance.
8 and a RAM (Random Access Memory) 8 into which information necessary for executing programs is written and read.

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-ROMs and DATs, but non-perishable storage media such as IC cards can also be used. 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 such as the vehicle's current location coordinates that was stored in the RAM 9 immediately before is supplied to the DAT encoder 12 via the DAT encoder/decoder 13 as backup data, and is stored in the DAT. When the power is turned on, the DA
The stored information of T is read out by the DAT deck 12. The read information is sent to the DAT encoder/decoder 13
RAM by being sent to bus line L via
9 is stored.

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 15 and supplied as ttti 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. 19
Display 17 based on the image data output from
It also includes a display controller 20 that controls the display of 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 the elements of the pair 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 centered around the origin O of the UV orthogonal coordinate system, as shown in Figure 2. You can draw a trajectory. Therefore, if PJ is the point P (U
The counterclockwise azimuth θ from the east (■ axis) is calculated from the following formula: It's possible.

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 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,
Plot the output obtained by rotating the magnetic detection element once. Considering that the distance between the center of the drawn circle and the coordinate origin is due to the influence of body magnetization, the center of the drawn circle is The output data obtained from both detection elements is corrected so as to move to the origin, and the influence of body magnetization is removed.

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 U[, VIEI
X and the minimum values LTw, vvvn are determined, and from these, the coordinates of the center Q are calculated using the following equation (2).

Uo − (Um+Own)/2 } ...... (2) Vo = (Vmx+VNn) / 2 Using the calculated center values UO and vQ, 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 UV-.

U-U-Uo ...... (3) V''-V-Vo Note that the center values U○, VO, and radius r are based on the so-called one-rotation compensation at the time of system startup, that is, the geomagnetic sensor. It can be determined in advance by rotating the vehicle equipped with it once.

Next, the processing procedure for detecting an abnormality in the output data of the geomagnetic sensor executed by the CPU 7 will be explained according to the flowchart 1 in FIG. Note that this subroutine recognizes the current location of the vehicle, reads out a group of map data for a certain area including the current location from the CD-ROM, displays it on the display 17 as a map around the current location of the vehicle, and displays the data on the map. It is assumed that the main routine (not shown) is called and executed at predetermined intervals Ta during execution of a main routine (not shown) that performs processes such as displaying the own vehicle position indicating the current location of the vehicle.

The CPU 7 first takes in the output data (hereinafter referred to as sensor data) MX, MY of the geomagnetic sensor (step S31), and then reads the output data (hereinafter referred to as GPS data) of the geomagnetic sensor 4 based on the output data (hereinafter referred to as GPS data). Direction obtained from GPS data by finding the absolute direction of
(referred to as azimuth) Gθ (step S32)
, j'? with the captured sensor data MX, MY and one rotation correction. Center value (corrected value) MXoJi
Speaking of Yo (corresponding to the Q coordinate in Figure 2), from the following equation (4), MY − M Yo Mθ - tan → ( ) ...
(4) M
Step S33).

Next, the CPU 7 calculates the GPS direction Gθ and the sensor direction k1θ.
It is determined whether the azimuth difference from
In step S35), it is determined whether the count value Na becomes equal to or greater than a predetermined value Nth+ (step S36). If Na≧N th+, IGθ−Mθl
>THD has continued for a predetermined period (1 TxNth+), so the CPU 7 determines that the sensor orientation Mθ is ambiguous (inaccurate), in other words, the influence of celadon on the vehicle body caused by passing through a railroad crossing, etc. When the sensor data MX, MY are determined to be sharp, an abnormality detection flag is set (step S37), and then the counter I is reset (step S38). With the above, a series of processes for detecting an abnormality in sensor data MX, -IY is completed, and the program returns to the main routine. In step 534, IGθ−MθI≦T H D c! : ? l
1, the program moves directly to step S38, and in step S36 it is determined that Na≧N th+ and 1+1
If so, the program returns directly to the main routine.

In the main routine, the CPU 7 monitors whether or not the abnormality detection flag is set at every predetermined period Tb, and if it is determined that the abnormality detection flag is set, the CPU 7 sets the center value M o, M
The process moves to a subroutine for correcting Y o.

In the flowchart of FIG. 4, the CPU 7 first takes in the sensor data MX and MY (step S41), and calculates the rate of change for each of the sensor data MX and MY.
That is, it is determined whether the absolute value of the difference between the current value and the previous value of the sensor data MX, MY is less than a certain value (steps S42, S43). If both conditions are satisfied, the CPU 7 increments the counter ■ that counts the number of times (step S44), and then determines whether the count value Nb has exceeded the predetermined value Nth2 (step S45). ). If Nb≧Nth2, it means that the rate of change of each of the sensor data MX, MY has been below a certain value for a predetermined period (-TbxNth2), so the CPU 7 changes the sensor data MX, MY
is stable, calculates the GPS orientation Gθ from the GPS data (step S46), uses this GPS orientation Gθ and the current values of sensor data MX, MY as captured data,
From the radius r of the circle determined in advance by these captured data and one rotation correction, MXo −MX − r − cosGθ} ・・
(5) Find the center value based on the precalculation formula MYo - IIMY - r - slnGθ and correct it as new center values MXo, MYo (step S47);
Next, the current values of the sensor data MX and MY are set as the previous values (step S48), and the counter ■ and the abnormality detection flag are each reset (step S349).
). As described above, a series of processes for correcting the center values MXo, MYo due to the detection of an abnormality in the sensor data MX, MY is completed, and the program returns to the main routine. If it is determined in steps S42 and 943 that the rate of change of each of the sensor data MX and MY is not less than a certain value, the program moves directly to step 348, and in step S45
If it is determined that b<Nthz, the program directly returns to the main routine.

Thereafter, in the main routine, the output data of the geomagnetic sensor is corrected based on the new corrected center values MXo, MYo.

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.

Note that in the above embodiment, the center value MXo. Myo
Although we have explained the case where the correction is made based on the absolute bearing Gθ obtained from GPS data, the present invention is not limited to this. For example, the angle of a road line segment obtained from map data can be obtained as the driving direction of the current location. Using the direction of the lever, new center values MXo, MYo may be obtained from equation (5), or the obtained center values MXo, MYo may be used as provisional center values, and while monitoring fluctuations in these provisional center values, multiple provisional values may be calculated. It is also possible to determine the standard deviation of the center values, and when this standard deviation becomes less than a predetermined value, to determine the average value of a plurality of provisional center values to obtain new center values M X o and M Y o.

Effects of the Invention As explained above, in the in-vehicle navigation device according to the present invention, the sensor direction is determined based on the output data of the geomagnetic sensor, and the GPS direction is determined based on the output data of the GPS device.
The configuration is such that each direction is determined, the absolute value of the direction difference of each of these detected directions is monitored, and when the absolute value of this direction difference exceeds a predetermined value, it is determined that the output data of the geomagnetic sensor is redundant. Therefore, if the vehicle body is magnetized when the vehicle passes through a railroad crossing, and the output data of the geomagnetic sensor becomes constant due to this, this can be reliably detected.

[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 process for detecting abnormalities in the output data of the geomagnetic sensor. Flowchart showing the procedure. FIG. 4 is a flowchart showing the processing procedure for correcting the center values MXo and MYo. Explanation of the symbols of the main parts 1... Directional sensor (geomagnetic sensor) 5...
... System controller 10 ... CD ROM driver 16 ... Display device 17 ... Display

Claims (2)

[Claims] (1) A geomagnetic sensor that detects the running direction of the vehicle, a GPS device that detects the absolute position of the vehicle, and a display means that displays an image according to the supplied display information signal, each in a plurality of regions. a reading means for reading a plurality of corresponding map data groups from a storage medium in which the plurality of map data groups are stored; and a reading means for reading a plurality of corresponding map data groups from a storage medium while recognizing the current location of the vehicle and extracting from the storage medium a map data group for a certain area including the current location. an in-vehicle navigation device comprising: control means for controlling the extracted map data group and current location information to the display means as the display information signal to display a map around the current location of the vehicle and the current location; The means calculates a first running direction based on the output data of the geomagnetic sensor and a second running direction based on the output data of the GPS device, and calculates each of the first and second running directions. An in-vehicle navigation device characterized in that the absolute value of the difference is monitored, and when the absolute value of the azimuth difference exceeds a predetermined value, it is determined that the output data of the geomagnetic sensor is abnormal. (2) The control means determines that the output data of the geomagnetic sensor is abnormal when the absolute value of the orientation difference exceeds a predetermined value for a predetermined period of time. In-vehicle navigation device.