JPS63113309A - Method for processing data of earth magnetism sensor - Google Patents

Abstract

PURPOSE:To prevent the reception of the disturbance due to the external magnetic field, by calculating new correction data on the basis of the output data at two points and correcting the output data of an earth magnetism sensor on the basis of said correction data. CONSTITUTION:An earth magnetism sensor 1 is mounted on a vehicle at a predetermined angle with respect to the fore-and-aft or left-and-right direction of the vehicle and operation is performed on the basis of the output data from the detection elements in both of the north and east directions to detect the azimuth of the vehicle. In this case, the sampling of data is performed with respect to the output data of the earth magnetism sensor 1 within a predetermined time and, when the variation of said data is within a tolerable range and the data at least at two points separated by a predetermined angle or more from each other are obtained, correction data is calculated on the basis of the data at two points and used for correcting the output of the sensor 1. By this method, without receiving the disturbance due to the external magnetic field, highly reliable azimuth data can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a data processing method for a geomagnetic sensor in an on-vehicle navigation device.

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, and its output data may be affected when a vehicle passes a railroad crossing, a railway bridge, or when a large vehicle (such as a truck or bus) passes by the vehicle. will contain a large error.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned points, and aims to more accurately detect the direction of the vehicle and perform highly accurate navigation by increasing the reliability of the direction data obtained by the geomagnetic sensor. The purpose of this study is to provide a data processing method for a geomagnetic sensor.

A geomagnetic sensor data processing method according to the present invention samples output data of a geomagnetic sensor within a predetermined period of time, and obtains data from at least two points whose variation is within an allowable range and which are separated by a predetermined angle or more. When all the data are collected, correction data is obtained based on the data of at least two points, and this correction data is used as new correction data.

Example Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a vehicle-mounted navigation device to which a geomagnetic sensor data processing method 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.
A ROM (read-only Q) in which various processing programs and other necessary information for the CPU 7 are written
Memory) 8, RAM (Random Access Memory) 9 in which information necessary for executing programs is written and read, and so-called CD-ROMs, IC cards, etc., which are digitized (numerical). A recording medium 10 on which map information has been recorded, and a V-RAM (Vid
a graphic memory 11 consisting of a
Graphic data such as a map sent from the CPU 7 is drawn in the graphic memory 11 and CR as an image.
It is comprised of a graphic controller 13 that controls the display 12 such as T. 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 SL), 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 85).

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 510).

In addition, 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, which is an auxiliary direction sensor, at fixed time intervals, as shown in FIG. 3, by interrupt processing by a timer (step Sll,
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 determines the origin O of the UV orthogonal coordinate system as shown in FIG.
The locus of a circle I centered at is drawn. Therefore, for example, the clockwise azimuth θ from the north (U axis) at point P (U+, V+) is calculated by the following equation (1).

θ−t an' (U/V)−=−(1) Therefore, such a geomagnetic sensor 1 is attached to a vehicle at a predetermined angle with respect to the front and rear or left and right directions of the vehicle, and both U and V By performing the calculation of equation (1) based on the output data from the detection element, the direction of the vehicle can 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 value Umx, V beast and minimum value U 1n , V
w is determined, and from these, the coordinates of the center Q are calculated using the following equation (2).

Uo = (U kick + Uiln) / 2)...
(2) V□ - (V order + Vmn) / 2 The calculated values UO and VO become correction data for the output data of the geomagnetic sensor 1, and each magnetic detection is performed using the correction data UO and VO according to the following equation (3). Element output value U, V
is corrected, and the direction is calculated from the corrected U- and V''.

U″-U-UO ) (3) V--V-V.

Next, the procedure of the geomagnetic sensor data processing method according to the present invention executed by the CPU 7 will be explained according to the flowchart of FIG. Note that this routine is called and executed from the main routine at regular time intervals or at regular mileage intervals. In addition, the CPU 7 also performs interrupt processing as shown in FIG. 6 every unit traveling distance or every unit time.
.

(2) is saved in the set array on the memory (RAM 9) (step 520), and the pointer and counter are updated (step 521).

In FIG. 5, the CPU 7 first calculates variations in the sampled output data of the geomagnetic sensor 1 (step 530). As mentioned earlier, the output data of the geomagnetic sensor 1 is two-dimensional data U, V in the X, Y coordinate system.
Here, the deviation of each of the output data U and V is determined to determine the variation. Further, the data variation may be determined by the correlation between U and V. Then, it is determined whether the obtained variation is within the set range, that is, whether the data is valid or not (step 531).
If the data is outside the setting range, that is, if the data is invalid, it is determined that the geomagnetic sensor 1 has received a disturbance and its output data has fluctuated greatly, and the process proceeds to step S40. In step S40, the previously determined orientation data or the output data of another auxiliary orientation sensor such as the angular velocity sensor 2 is used as the orientation data.

In other words, in such a case, it is a temporary fluctuation in the output data of the geomagnetic sensor 1 due to a disturbance, so instead of using that data, it is more reliable than the previously determined azimuth data or the output data of the geomagnetic sensor 1 at that point. By using, for example, the output data of the angular velocity sensor 2, which is considered to have high accuracy, as the azimuth data, the reliability of the azimuth data can be increased.

On the other hand, if the data variation is within the set range,
The average value is used as estimated azimuth data, and it is determined whether this data falls on the hypothetical circumference defined by the center values Uo, Vo and radius r (step 532). The determination here is made by determining whether the difference between the distance from the center values Uo and vo of the orientation data and the radius r is within a predetermined range. If it is within the predetermined range, step s3
7, the azimuth is calculated using the data, the center values UO, vo, and the radius r, as determined azimuth data, and a flag, which will be described later, is reset. If it is outside the predetermined range, it is determined that the vehicle body is magnetized, and the process proceeds to step S3B.

That is, when a vehicle passes, for example, a railroad crossing, the vehicle body is magnetized by the strong magnetic field at the railroad crossing, and as a result, the output data of the geomagnetic sensor 1 has a DC component, and as shown in FIG. Since a value shift occurs, it is no longer possible to correctly determine the direction. If the vehicle body is magnetized in this way and the center value deviation is large, the difference between the distance from the center value UQ, vo and the radius r will not fall within the predetermined range. In this case, in step 833, it is determined whether or not it has missed for the first time by checking a flag indicating this fact. If it is off for the first time, that is, the flag is not set, please set the flag in step 5.
38), and then proceeds to step S40.

If it is determined in step S33 that the flag is set, it is determined whether or not there is data a certain period of time after the first deviation (step 534).

If there is no such data, compare data will be created when this step is passed after a certain period of time (step 539), and then the process will proceed to step S40. If it is determined that there is data after a certain period of time, it is determined whether the current data is separated by a predetermined angle or more from the comparison data (step 535); if data at a different angle is obtained, step S36). Proceed to. If data separated by a predetermined angle or more is not obtained, the process advances to step S40.

In step S36, an equation of a circle with radius r is determined from data of two points separated by a predetermined angle or more. Two equations for a circle can be found, and which equation to use is determined based on the positional relationship between the last point on the circumference and the first point off the circumference. The center value of the circle obtained in this way U O
* Use VO as new correction data and update the value of the correction data. From then on, the updated center value (correction data) Uo
,V.

The azimuth is calculated using , the azimuth is determined as confirmed azimuth data, and the flag is reset (step 537).

In other words, the amount of deviation between the center value of the circle after the update and the center value of the circle before the update becomes the magnetization vector amount when the vehicle body is magnetized, and as described above, the deviation amount of the center value of the circle after the update is the amount of the magnetization vector when the vehicle body is magnetized. ), it is possible to reliably correct the variation in the output data of the geomagnetic sensor 1 due to the magnetization of the vehicle body, and it is possible to obtain highly reliable azimuth data.

In addition, in the above example, the equation of the circle and its center are determined from the data of two points separated by a predetermined angle or more, but the equation of the circle is not limited to this. Of course, it is also possible to find the center.

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, output data of a geomagnetic sensor is sampled within a predetermined period of time, and at least two samples are sampled within a permissible range and separated by a predetermined angle or more. When the point data is complete,
By obtaining new correction data based on the data of at least two points and correcting the output data of the geomagnetic sensor using this correction data, highly reliable azimuth data can be obtained without being affected by disturbance magnetic fields. This makes it possible to more accurately detect the direction of the vehicle and achieve highly accurate navigation.

[Brief Description of the Drawings] Fig. 1 is a block diagram showing the configuration of an in-vehicle navigation device to which the geomagnetic sensor data processing method according to the present invention is applied, and Figs. 2 and 3 are executed by the CPU in Fig. 1. Flowchart showing the basic steps to be performed, Part 4
The figure is a line diagram showing the trajectory drawn by the output data of the geomagnetic sensor.
5 is a flowchart showing the procedure of the data processing method of the geomagnetic sensor according to the present invention executed by the CPU in FIG. 1; FIG. 6 is a flowchart showing the procedure of the interrupt processing executed by the CPU in FIG. 1; FIG. 7 is a diagram showing a state in which the locus drawn by the output data of the geomagnetic sensor has a center value shift. Explanation of symbols of main parts

Claims (1)

[Claims] A data processing method for a geomagnetic sensor that corrects variations in output data of a geomagnetic sensor that detects the traveling direction of a vehicle using correction data to obtain azimuth data, the method comprising sampling data within a predetermined time regarding the output data of the geomagnetic sensor. When the fluctuation of the data is within the allowable range and the data of at least two points separated by a predetermined angle or more are obtained, correction data is obtained based on the data of these at least two points, and this correction data is used as a new one. A data processing method for a geomagnetic sensor, characterized in that the data is processed as correction data.