JPS63109317A - Data processor of earth magnetism sensor - Google Patents

Abstract

PURPOSE:To detect the accurate azimuth of a vehicle, by preliminarily calculating the data for correcting the variation in the output data of a sensor caused by a disturbance magnetic field. CONSTITUTION:The data correcting the variation in the output data of an earth magnetism sensor 1 caused by a disturbance magnetic field is preliminarily stored in RAM 9. Next, when variation is again generated in the output data of the earth magnetism sensor 1 caused by the disturbance magnetic field, the earth magnetism sensor template formed on the basis of correction data is displayed on the same picture of a display 12 along with the output data up to that time of the earth magnetism sensor 1. Then, the earth magnetism sensor data template displayed on the display 2 is moved corresponding to the input of a cursor and the data forming the earth magnetism sensor data template after movement in response to a movement finish order is set to new correction data. By this method, the reliability of the azimuth data calculated by the earth magnetism sensor 1 can be enhanced without receiving the effect of the disturbance magnetic field and the azimuth of a vehicle can be accurately detected.

Description

TECHNICAL FIELD The present invention relates to a geomagnetic sensor data processing device, and more particularly to a geomagnetic sensor data processing device in a vehicle-mounted navigation system.

Background Art In recent years, in-vehicle navigation devices have been researched and developed that guide a vehicle to a predetermined destination by storing map information in a memory, reading the map information from the memory, and displaying the map information along with the vehicle's current location on a display device. has been done.

Such a navigation device requires a direction sensor that detects the direction of the vehicle, and as this direction sensor, for example, a geomagnetic sensor that detects the direction of the vehicle based on geomagnetism (earth's magnetic field) is used. However, this geomagnetic sensor is easily affected by disturbance magnetic fields. For example, when a vehicle passes a railroad crossing, there is extra magnetic flux due to the magnetization of the body steel plate, etc. After magnetization, accurate direction detection will no longer be possible.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned points, and provides a data processing device for a geomagnetic sensor that enables accurate direction detection of a vehicle by increasing the reliability of direction data obtained by a geomagnetic sensor. The purpose is to

The geomagnetic sensor data processing device according to the present invention obtains in advance correction data for correcting variations in output data of the geomagnetic sensor caused by a disturbance magnetic field, and prevents fluctuations in the output data of the geomagnetic sensor again due to the disturbance magnetic field. When this occurs, the basic figure created based on the correction data is displayed on the same screen of the display together with the previous output data group of the geomagnetic sensor, and the basic figure displayed on the display is changed according to the cursor input. The data for creating the basic figure after movement in response to a movement end command is used as correction data.

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

FIG. 1 is a block diagram showing the configuration of an in-vehicle navigation device to which a geomagnetic sensor data processing device according to the present invention is applied. In the figure, 1 is a geomagnetic sensor for outputting vehicle orientation data based on geomagnetism, 2 is an angular velocity sensor for detecting the angular velocity of the vehicle, 3 is a mileage sensor for detecting the distance traveled by the vehicle, 4 is a GPS for detecting the vehicle's current location from latitude and longitude information, etc.
(Global Positioning System
m) device, and the output of each of these sensors (devices) is supplied to the system controller 5.

The system controller 5 has an interface 6 which inputs the outputs of the sensors (devices) 1 to 4 and performs A/D (analog/digital) conversion, etc., and processes various image data which are sequentially sent from the interface 6. A CPU (central processing circuit) 7 that calculates the amount of movement of the vehicle, etc. based on the output data of each sensor (device) 1 to 4.
and a ROM (read-only) in which various processing programs and other necessary information for the CPU 7 are written in advance.
RAM (random access memory) 9, in which information necessary for executing programs is written and read, and a so-called CD-ROM, an IC card, etc., and is digitized (numerized). A recording medium 10 on which map information has been recorded, and a V-RAM (Vi
Graphic data such as a map sent from the CPU 7 is drawn in the graphic memory 11 and is stored as an image in the graphics memory 11.
It is composed of a graphic controller 13 that controls display on a display 12 such as an RT. The input device 14 consists of a keyboard or the like, and various commands and the like are issued to the system controller 5 by the user's keystrokes.

Next, the basic procedure executed by the CPU 7 will be explained according to the flowchart shown in FIG.

The CPU 7 first initializes the program to execute it (step S1), and then determines whether the current location of the vehicle has been set (step S2). If the current location has not been set, a current location setting routine is executed (step S3), for example, the current location is manually set using the keys on the input device 14. Next, the mileage is set to zero (step S4), and it is then determined whether there is any key input from the input device 14 (step S5).

If there is no key personnel available, a map of the area around the current location is displayed on the display 12, and the current location of the vehicle and its direction are displayed on this map using, for example, a vehicle mark, and when the vehicle moves, the map scrolls as the vehicle moves. Furthermore, when the vehicle position is likely to exceed the range of the map data currently on the graphic memory 11, the necessary map data is read out from the recording medium 10 and displayed on the display 12 (step S6).

If there is key human power, the current location is reset (step S7) and sensor correction (step S8) according to the input data.
, destination setting (step S9), and map enlargement/reduction (step 5IO).

Further, the CPU 7 constantly calculates the direction of the vehicle based on the output data of the geomagnetic sensor 1 and the angular velocity sensor 2 at regular time intervals, as shown in FIG. 3, by interrupt processing using a timer (step S11.512).

By the way, the geomagnetic sensor 1 generally consists of a pair of magnetic detection elements arranged on the same plane with a phase angle of 90'' to each other, and one of the pair of elements is, for example, U
The geomagnetic component in the direction (north direction) is detected, and the other is in the V direction (
It is designed to detect the geomagnetic component in the east direction. When the geomagnetic sensor 1 having 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. The trajectory is drawn. Therefore, for example, point P
The clockwise azimuth θ from the north (U axis) at (U+, V+) is calculated by the following equation (1).

θ−tan→ (U/V)−・−−−−(1) Therefore,
Such a geomagnetic sensor 1 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. This allows the direction of the vehicle to be detected.

Ideally, only magnetic flux due to the earth's magnetic field exists around the geomagnetic sensor 1, but in a vehicle,
Generally, there is extra magnetic flux due to magnetization of the body steel plate. Therefore, in order to remove the influence of magnetization of the vehicle body and perform accurate direction detection,
For example, a method disclosed in Japanese Unexamined Patent Publication No. 57-28208 is proposed. 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 the rain detection element is corrected so that the center of the drawn circle moves to the origin, and 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 output of the rain detection element is located at a position moved from the origin, as shown by ■ in FIG. Therefore, the output U of the rain detection element.

Maximum values Um, Vm and minimum values U mn, V mn of ■
From these, the coordinates of the center Q are calculated using the following equation (2).

Uo = (Umx+Umn) /2 ) ...... (2) vo - (Vmx+Vmn) / 2 Using the calculated values UO and vo, the output values U and V of each magnetic detection element are determined by the following equation (3). is corrected, and the direction is calculated from the corrected U=, V''.

U-=U-U.

) (3) V”-V-V.

Furthermore, in order to increase the reliability of the output data of the geomagnetic sensor 1, a tolerance range (hereinafter referred to as a window) is set based on a certain rule to allow variation in the output data of the geomagnetic sensor 1. In other words, as shown by diagonal lines in Figure 5,
The direction data obtained last time (U n-+ , V n-r
) is set as a reference in the angular direction, and the difference between the azimuth data obtained last time and the azimuth data obtained this time is constantly monitored. In this case, the reliability of the output data of the geomagnetic sensor 1 can be improved by treating the data as an error and replacing it with predetermined data, such as the previous data or the average value of the past number of times (the number of times is arbitrary). enhance Also, since the data output from the geomagnetic sensor 1 is mathematically applicable to the equation of a circle,
Data that does not appear on this equation can also be determined as an error. However, since the data varies due to A/D conversion errors and the like, the window is set with a certain width in the radial direction. In FIG. 5, α represents an angle tolerance, and β represents a radius tolerance.

Note that since the difference in orientation varies depending on the time interval at which the orientation data is obtained, it is also possible to determine it based on the relationship between angular velocity and vehicle speed. For example, if the vehicle speed is 40 [km/h] and the maximum angular velocity is 30 [degrees/s], if the output data of the geomagnetic sensor 1 exceeds this range, it will be considered an error, and the previous data or the past Replace with the average value of the data.

In addition, when setting a window using an angle, it is also possible to set the angle according to changes in vehicle speed.In addition to setting the angle as a linear function relative to vehicle speed, it is also possible to set a window according to vehicle speed by providing a certain hysteresis. This eliminates the need to frequently change the corresponding angle in response to changes.

Next, the procedure of the method of processing the output data of the geomagnetic sensor 1 executed by the CPU 7 will be explained according to the flowchart of FIG. 6.

The CPU 7 first determines whether so-called one-rotation correction has been completed (step 520). If not completed, execute one rotation correction routine (step 521)
. In this one-rotation correction routine, the vehicle equipped with the geomagnetic sensor 1 is rotated once, and the values of Uo, Vo (center value), and radius r are determined. The determined value is stored in RAM9.

Next, an initial orientation is set (step 522).

Since the vehicle is stationary when the engine is started and the orientation of the vehicle should be constant, it is preferable to set the initial value at this time. After setting the initial orientation, the output data of the geomagnetic sensor 1 is taken in (step 523), and it is determined whether or not this output data falls within the aforementioned window (the shaded area in FIG. 5) (step 524). If it is within the window, the direction of the vehicle is calculated based on the above-mentioned equations (1) to (3) from the captured output data of the geomagnetic sensor 1 (step 525). The calculated direction is displayed together with the map on the display 12 in step S6 in the flowchart of FIG.

Next, the count value N of the window error counter that counts the number of times the output data of the geomagnetic sensor 1 is outside the window and the count value E of the center value deviation judgment counter that counts the number of times that the center value deviation has occurred are both set to zero. (step 526), and then returns to step 823. The flow described above is the flow during normal operation when the output data of the geomagnetic sensor 1 is within the window without being affected by the disturbance magnetic field.

On the other hand, if the output data of the geomagnetic sensor 1 is not within the window, the count value N of the window error counter is incremented by '1'' in step 529.
), then it is determined whether the count value N has reached the maximum window error value Nvmx (step 530).
. Then, until the window error maximum value Nvnx is reached, the output data of the geomagnetic sensor 1 that has been imported this time is regarded as an error, and the output data obtained based on the previous value of the output data of the geomagnetic sensor 1 or the average value of several past times is assumed to be an error. Use the direction (step 531), and then return to step 823.

Further, when the count value N of the window error counter reaches the window error maximum value Nw, the count value E of the center value deviation counter is counted up by "1" (step 532), and then the count value E is set to the center value. It is determined whether the maximum deviation determination value Emx has been reached (step 833).

Then, in step 53, a timer is set for a certain period of time until the center value deviation judgment maximum value EaIIX is reached.
4), until it is determined that time is up in step S35,
Import the output data of the geomagnetic sensor 1 (step 53
6) Calculate the orientation based on the data (step 537). That is, if the output data of the geomagnetic sensor 1 does not fit into the window for a certain period of time, the window is temporarily canceled and error processing is not performed for a certain period of time. Through this processing, it is possible to cope with the case where non-standard data is captured due to, for example, a sudden steering wheel.

When the count value E of the center value deviation counter reaches the maximum value Ex for determining center value deviation, it is determined that the center value deviation has occurred.
A center value correction routine is executed to correct the center value deviation (step 538).

This center value correction routine will be described later using the flowchart of FIG. Next, the count value N of the window error counter and the count value E of the center value deviation determination counter are both set to zero (step 539), and then the process returns to step S23.

For example, when a vehicle passes through a railroad crossing, the vehicle body is magnetized by the strong magnetic field at the railroad crossing, which causes the output data of the geomagnetic sensor 1 to have a DC component.
Since a center value shift occurs as shown in FIG. 7, it is no longer possible to correctly determine the orientation from then on. If the vehicle body is magnetized in this way and the center value shifts, the output data of the geomagnetic sensor 1 will not enter the window no matter how long it takes, so by counting the number of times it does not enter the window for a certain period of time, , it can be determined that this state has occurred. If such a situation occurs, center value correction processing, which will be described in detail below, is performed.

In the center value correction routine shown in FIG.
First, the output data group of the geomagnetic sensor 1 in the past stored in step 323 in FIG.
Step 540), followed by plotting the center value (correction data) Uo currently stored in the RAM 9.
,V.

A geomagnetic sensor data template (circle as a basic figure) approximately approximated as an ellipse with the center at is displayed on the same screen as the geomagnetic sensor data plot, as shown in FIG. 9 (step 541). This display allows the user to recognize that the output data of the geomagnetic sensor 1 has changed again due to the disturbance magnetic field. In this state, the user can move the circle displayed on the display 12 vertically and horizontally by operating, for example, a cursor key on the input device 14 such as a keyboard.

The CPU 7 determines whether there is any cursor key input (step 542), and if there is key input, it controls the display position of the circle according to the key input (step 8).
43). At this time, the operator must ensure that at least part of the circle
As shown in Figure 0, enter the keys so that they match the geomagnetic sensor data plot, and if they match, press the end key manually.

The CPU 7 waits for input of this end key (step 544).
), End key If you have the human power, change the center value of the circle (geomagnetic sensor data template) whose part is superimposed on the geomagnetic sensor data plot to the new center value tJo,
The data is stored as vo in the RAM 9 (step 545) and used as correction data when calculating the direction based on the output data of the geomagnetic sensor 1 thereafter.

That is, in the geomagnetic sensor data processing device according to the present invention, a tolerance range is set to allow variations in the output data of the geomagnetic sensor 1, and when a vehicle passes, for example, a railroad crossing, the strong magnetic field at the railroad crossing causes the vehicle body to land. Due to this, the output data of the geomagnetic sensor 1 becomes D.
It monitors whether a center value shift occurs due to the C component, and if a center value shift occurs, the center value UO is determined by having the user perform pattern recognition using a geomagnetic sensor data template.

Correction of vO is performed. According to this, there is no need to automatically correct the center values UO and vo, so the amount of software can be reduced, and for example, when there is no place to turn the vehicle and one revolution correction cannot be easily performed. This will be particularly useful.

As described in detail, according to the present invention, correction data for correcting variations in the output data of the geomagnetic sensor due to the disturbance magnetic field is obtained in advance, and the output data of the geomagnetic sensor due to the disturbance magnetic field is When a change occurs again in the geomagnetic sensor, the geomagnetic sensor data template created based on the correction data is displayed on the same screen as the geomagnetic sensor's previous output data group, and the geomagnetic sensor data displayed on the display is By moving the template in response to cursor input and creating a geomagnetic sensor data template after movement in response to a movement end command as new correction data, the data can be obtained by the geomagnetic sensor without being affected by disturbance magnetic fields. Since the reliability of the azimuth data obtained can be increased, the azimuth of the vehicle can be detected accurately.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an in-vehicle navigation device to which a geomagnetic sensor data processing device according to the present invention is applied, FIG. 2 is a flowchart showing the basic procedure executed by the CPU in FIG. 1, and FIG. The figure is a flowchart showing the timer interrupt processing procedure executed by the CPU in Fig. 1, Fig. 4 is a line diagram showing the trajectory drawn by the output data of the geomagnetic sensor, and Fig. 5 is a line diagram showing the trajectory drawn by the output data of the geomagnetic sensor. A line diagram showing the state in which the window is set, Fig. 6 is a flowchart showing the procedure of the data processing method of the geomagnetic sensor executed by the CPU in Fig. 1, and Fig. 7 shows the trajectory drawn by the output data of the geomagnetic sensor at the center value. A line diagram showing the state where the deviation has occurred, Fig. 8 is a flowchart showing the procedure for center value deviation correction executed by the CPU, and Fig. 9 shows the geomagnetic sensor data plot and geomagnetic sensor data template displayed on the same screen. The figure shown in FIG. 10 is a diagram showing a state in which a geomagnetic sensor data template is matched with a geomagnetic sensor data plot displayed on the same screen. Explanation of symbols of main parts

Claims (1)

[Claims] A data processing method for a geomagnetic sensor mounted on a vehicle and outputting azimuth data of the vehicle based on geomagnetism, the method comprising:
Correction data for correcting the variation in the output data of the geomagnetic sensor due to the disturbance magnetic field is obtained in advance, and when the output data of the geomagnetic sensor again fluctuates due to the disturbance magnetic field, the correction data is calculated in advance. A basic figure created based on the correction data along with a group of output data up to this point is displayed on the same screen of the display, and the basic figure displayed on the display is moved according to the cursor input, and a movement end command is issued. A data processing method for a geomagnetic sensor, characterized in that data for creating the basic figure after movement in response is used as correction data.