JP2876634B2 - Magnetization correction device for geomagnetic direction sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a geomagnetic azimuth sensor that corrects X and Y data output from a geomagnetic azimuth sensor that detects the traveling azimuth of a moving object such as a vehicle using geomagnetism as an index. And a magnetization correction device.

2. Description of the Related Art Conventionally, there has been known an apparatus which detects a traveling direction of a moving body and detects a traveling position of the moving body by detecting a direction of a geomagnetic field using a geomagnetic direction sensor for detecting a direction of a magnetic field. ing. When the geomagnetic azimuth sensor is mounted on a moving body made of an iron plate such as a vehicle, for example, the X and Y data output from the geomagnetic azimuth sensor is affected by the magnetization of the moving body and the like. When the voltage signals Vx and Vy are offset, an accurate azimuth of the geomagnetism may not be detected.

For example, when the vehicle body is magnetized when passing a train crossing or the like, the influence of this magnetization causes the voltage signals Vx and Vy from the geomagnetic direction sensor to be offset as shown in FIG. The center coordinates of the azimuth circle drawn by the locus of the coordinates of the voltage signals Vx and Vy move to the position of the center coordinates O offset from the original center coordinates Oa. Although the traveling direction of the vehicle is actually changed by the angle θa, the voltage signals Vx and Vy from the geomagnetic direction sensor are directly detected as the direction θ, and an error occurs in the traveling direction.

Therefore, when performing magnetization correction of the terrestrial magnetism azimuth sensor, before starting actual driving, running one revolution so as to draw a circle, the center coordinates of the original azimuth circle are obtained, and in actual driving this The traveling azimuth is detected using the center coordinates of the azimuth circle. Then, when new magnetization occurs in actual traveling and an error occurs in the traveling direction, it is necessary to perform traveling once again to newly obtain the center coordinates of the azimuth circle.
For example, based on the center coordinates Oa of the azimuth circle and the center coordinates O of the newly obtained azimuth circle, an error azimuth vector or the like between the center coordinates is calculated, and the traveling azimuth in the actual running thereafter is corrected. do. However, in this case, the actual traveling must be interrupted and the rotating traveling must be performed, which imposes a heavy burden on the driver and is not practical.

Therefore, as disclosed in JP-A-63-128222, the azimuth change amount of the vehicle is detected by a means for detecting the azimuth change amount of the vehicle, and the output of the geomagnetic azimuth sensor and the azimuth before the azimuth change are detected by the geomagnetic azimuth sensor. There has been proposed an apparatus that detects the output of a geomagnetic azimuth sensor after a change, compares these outputs, and automatically obtains the center coordinates of an azimuth circle when making a turn.

[Problems to be Solved by the Invention] However, in such a conventional device, if the amount of change in the direction of the vehicle cannot be accurately detected, the correction of the geomagnetic direction sensor cannot be performed accurately, and the logical operation for the correction is not performed. There is a problem that it is complicated and the logical operation is difficult with the CPU mounted on the vehicle.

Accordingly, an object of the present invention is to provide a magnetization correction device for a geomagnetic azimuth sensor capable of accurately correcting a traveling azimuth with a simple configuration, with the object of solving the above-described problems.

[Means for Solving the Problems] In order to achieve the object, the present invention has the following configuration as means for solving the problems. That is, as illustrated in FIG.
X detected by the geomagnetic azimuth sensor M1
In a magnetization correction device for a geomagnetic azimuth sensor for correcting the azimuth of the terrestrial magnetism based on the center coordinates of the azimuth circle drawn by the locus of the coordinates of the Y data, a turning direction detecting means M2 for detecting a turning direction of the moving body.
And a data calculating means M3 for calculating two sets of X, Y data separated by the azimuth radius on the azimuth circle drawn by the X, Y data when the moving body turns, calculated by the data calculating means M3 Center coordinate calculating means M4 for calculating the center coordinates of the azimuth circle at the time of turning based on the two sets of X, Y data thus obtained and the turning direction detected by the turning direction detecting means M2. This is the characteristic configuration of the magnetization correction device of the terrestrial magnetism sensor.

[Operation] In the magnetization correction device for a terrestrial magnetism sensor having the above configuration, a terrestrial magnetism sensor M1 is attached to a moving body, detects the azimuth of the terrestrial magnetism by orthogonal X and Y components, and the turning direction detecting means M2 moves. Detect the body turning direction. Then, when the data calculating means M3 turns the moving body, two sets of azimuth circles separated by the azimuth circle radius on the azimuth circle drawn by the trajectory of the coordinates of the X, Y data
X, Y data is calculated, and the center coordinate calculating means M4 calculates the azimuth circle at the time of turning based on the two sets of X, Y data calculated by the data calculating means M3 and the turning direction detected by the turning direction detecting means M2. Calculate center coordinates. The azimuth of the geomagnetism is corrected based on the calculated center coordinates. Thus, accurate correction can be performed even with a simple configuration.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a schematic configuration diagram of a magnetization correction device for a geomagnetic bearing sensor according to one embodiment of the present invention. Reference numeral 1 denotes a geomagnetic azimuth sensor for detecting the azimuth of terrestrial magnetism by orthogonal X and Y components, and is mounted on a vehicle as a moving body in the present embodiment. In this embodiment, the geomagnetic direction sensor 1 is of a flux gate type. As shown in FIG. 3, an exciting winding 4 is provided on a ferromagnetic core 2 and an output winding 6 is provided so as to be orthogonal to each other. 8 are each wound. The excitation winding 4 has
An exciting current of a predetermined frequency is supplied by the AC circuit 10, and voltage signals Vx and Vy as X and Y data proportional to the magnetic field of the magnetic core 2 are induced from the output windings 6 and 8.

The voltage signals Vx and Vy from the terrestrial magnetic azimuth sensor 1 draw a trajectory circle with a radius R as shown in FIG. If the coordinates of two points on the azimuth circle that are separated from each other by the azimuth radius R are known, the center coordinates O (Xo, Yo) of the azimuth circle can be obtained by the following procedure. .

Two points separated by an azimuth radius R are a and b, and the two points have the following relationship.

(Xb-Xa) ² + (Yb-Ya) ² = R ² Assuming that the middle point between the two points a and b is c, the coordinates are ((X
a + Xb) / 2, (Ya + Yb / 2). Point e passes point c and Y
It is the intersection of a straight line parallel to the axis and a straight line parallel to the X axis passing through the point O, and the coordinates are ((Xa + Xb) / 2, Yo). The point f is the intersection of a straight line passing through the point a and parallel to the Y-axis and a straight line passing through the point b and parallel to the X-axis.
a, Yb). The triangle abo is an equilateral triangle whose one side length is equal to the azimuth radius R.

Here, the right triangle abf and the right triangle oce are considered.
At this time, since the line segment af and the line segment ce are both parallel to the Y axis, ∠baf = ∠bce. The sum of the interior angles of the triangle is 180 ° and ∠bco = ∠bce + ∠eco = 90 °, so that ∠bce = ∠coe holds. Therefore, the right triangle ab
It turns out that f and the right triangle oce are similar.

On the other hand, since the triangle abo is an equilateral triangle, Can be said. Therefore, the right triangle oce is the right triangle abf
of It turns out that it is the size of.

 From the above, the following relationship is derived.

Further, in FIG. 4, when the vehicle turns rightward from the point a in the direction of the point b, the center coordinate O (Xo, Yo) of the azimuth circle is derived by the following equation in consideration of the size of the data. .

Conversely, when the vehicle turns left from point b in the direction of point a, the center coordinate O of the azimuth circle is determined in consideration of the size of the data.
(Xo, Yo) is derived by the following equation.

From the above results, the point a (Xa, Ya) is set to the start point coordinate (X
s, Ys) and replace the point b (Xb, Yb) with the end point coordinates (Xe,
Ye), it can be expressed as the following equation.

Becomes

Reference numeral 12 denotes a turning direction detection sensor as turning direction detecting means M2, which detects whether the turning direction of the vehicle is clockwise or counterclockwise, and is constituted by a turn signal of a blinker, a wheel sensor, a steering sensor, a gyro, or the like. I just need.

Reference numeral 14 denotes a map memory, which comprises a large-capacity storage device such as a compact disk. The map memory 4 stores map information, for example, map information of a predetermined range such as Tokyo, Aichi or Tokai region for each page displayed on a display screen of a CRT (not shown). The map information includes data for reproducing a map such as a road shape, a road width, a road name, a building, a place name, and terrain, as well as geomagnetic declination data and geomagnetic intensity data at that point.

These geomagnetic direction sensor 1 and turning direction detection sensor 1
2. The map memory 14 is connected to the electronic control circuit 20. The electronic control circuit 20 includes a well-known CPU 22, a ROM 24 for storing control programs and data in advance, and a readable / writable RAM 26, and an input / output circuit 28 connected to each other via a common bus 30. The CPU 22 inputs signals from the geomagnetic azimuth sensor 1, the turning direction detection sensor 12, and the map memory 14 via the input / output circuit 28, and these signals, RO
M22, CPU 22 based on programs and data in RAM 26
Executes a correction process described later.

When a power switch (not shown) is turned on, the CPU 22 of the electronic control circuit 20 starts executing arithmetic processing according to a program preset in the ROM 24.

Next, the correction control process performed by the electronic control circuit 20 will be described with reference to the flowcharts shown in FIGS.

First, as shown in FIG. 5, in order to obtain the azimuth circle radius R, the vehicle is rotated once to draw an azimuth circle based on the locus of the coordinates of the signals Vx and Vy from the geomagnetic azimuth sensor 1. The turning coordinate is obtained by obtaining the center coordinate O of this azimuth circle (step 10).
0). Then, the radius of the azimuth circle is stored in advance as the azimuth circle radius R (step 110).

The calculation of the azimuth circle radius R is not limited to this case. As shown in FIG. 6, the driver sets the current vehicle position before moving on (step 150). Next, based on the set current position, geomagnetic intensity data corresponding to the current position is read from the map memory 14 (step 160). Then, the azimuth circle radius R at that position is calculated from the read geomagnetic intensity data (step 17).
0). That is, according to the geomagnetic intensity He at that position, the signal Vx,
This is because the magnitude of Vy changes and is proportional to the geomagnetic intensity He, and the following relationship holds.

R = K × He Vx ² + Vy ² = R ² The calculated value is stored as the azimuth circle radius R (step 180).

Next, the actual running is started, and the signals Vx and Vy from the geomagnetic direction sensor 1 are corrected based on the center coordinates of the azimuth circle obtained by executing the above-described processing (step 100). Calculate the traveling direction of the vehicle. When a vehicle travels on a road, the effects of bridges, buildings or guardrails,
The center coordinates of the above-described azimuth circle may be offset by the influence of a magnetic field other than the geomagnetism such as a train crossing or the like or a new magnetization of a vehicle. Therefore, when the traveling direction is calculated based on the center coordinates of the azimuth circle calculated by the above-described process due to such an influence during traveling of the vehicle,
An error occurs in the traveling direction.

Therefore, as shown in FIG. 7, a magnetization correction process is executed during actual running. First, it is determined whether or not the vehicle has started turning during actual running (step 200). This is determined by whether or not the traveling direction detected by the geomagnetic direction sensor 1 has changed, or whether or not a speed difference has occurred between the left and right wheels. When the turning has not been started, the present process is temporarily terminated, and when it is determined that the turning has been started,
The end point calculation value α is temporarily set to the maximum value, and the coordinate values corresponding to the signals Vx and Vy detected by the geomagnetic azimuth sensor 1 at this time are stored as start point X and Y data (Xs, Ys). (Step 210).

Then, it is determined whether or not the turning directions are the same based on whether or not the speed difference between the left and right wheels has been reversed (step 220). This is because if the traveling direction of the vehicle changes from the right to the left during the correction process, for example, the following process cannot be executed properly. Then, the present process ends. If it is determined that the turning directions are the same, the intermediate point X, Y data (Xi, Yi) corresponding to the signals Vx, Vy output from the geomagnetic azimuth sensor 1 read at a fixed sampling cycle is stored (step 230). ).

Next, a distance difference β is calculated from the start point data (Xs, Ys) calculated in step 210 and the intermediate point X, Y data (Xi, Yi) calculated in step 230 by the following calculation formula. I do.

β = | (Xi−Xs) ² + (Yi−Ys) ² −R ² | That is, the start point is obtained from the start point X, Y data (Xs, Ys) and the intermediate point X, Y data (Xi, Yi). If the current position and the current position are exactly separated by the distance of the azimuth circle radius R, the distance difference β becomes O.

Subsequently, it is determined whether or not the distance difference β is smaller than the end point calculation value α (step 250). At first, since the end point calculation value α is the maximum value, the distance difference β is smaller than the end point calculation value α, so the value of the distance difference β is stored in the end point calculation value α. Also, the midpoint X, Y data (Xi, Yi)
Is stored in the end point X, Y data (Xe, Ye) (step 260). Then, the processing after step 220 is repeatedly executed, and the intermediate point X, Y data (X
i, Yi), and when the distance difference β becomes larger than the previous value through the processing of steps 240 and 250, it is determined that the current position has reached the position of the azimuth circle radius R.

Next, the end point calculation value α is set to a predetermined allowable error γ.
It is determined whether or not it is below (step 270). The allowable error γ is the end point X, Y data (X
e, Ye) is a value corresponding to the error amount included in the position,
This is to determine whether the subsequent correction can be performed. If the end point calculation value α is larger than the allowable error γ, it is determined that appropriate correction cannot be performed, and the present process is ended once. If the end point calculation value α is equal to or smaller than the allowable error γ, it is determined that the start point (Xs, Ys) and the end point (Xe, Ye) are separated by the azimuth circle radius R within the range of the error. hand,
Whether the turning direction of the vehicle is right or not is determined based on the turning direction detected by the turning direction detection sensor 12 (step 280).

When the turning direction is the right direction, the above-described calculation at the time of the right turn described above is performed based on the start point X, Y data (Xs, Ys) and the end point X, Y data (Xe, Ye). The center coordinate O (Xo, Yo) of the azimuth circle is calculated by the equation (step 29).
0).

When the turning direction is the left direction, the starting point
Based on the X, Y data (Xs, Ys) and the end point X, Y data (Xe, Ye), the center coordinate O (Xo, Yo) is calculated by the above-described calculation formula at the time of the left turn (step 300). ).

Once the processing of steps 290 and 300 is executed, the correction processing is once ended. The execution of the processing of steps 200 to 270 functions as the data calculation means M3, and the execution of the processing of steps 280 to 300 functions as the center coordinate calculation means M4.

Based on the center coordinates O (Xo, Yo) calculated in this way,
The traveling direction is detected by correcting the signals Vx and Vy output from the geomagnetic direction sensor 1. When turning, if the angle is 60 ° or more, the start point and the end point are obtained. Therefore, as shown in FIGS. 8 and 9, a 90 ° turn is required as in the case of turning left on a right-angled road. Then, within that range, the respective start points a1, a2, a3 ... and the end points b1, b2, b3 ... are calculated for each sampling cycle, and the above-described processing is executed a plurality of times to calculate the respective azimuth circles. Calculate center coordinates. And
By calculating the average value of the center coordinates, for example, instantaneous magnetic disturbance can be removed, and more accurate center coordinates can be calculated.

As described above, the magnetization correction device of the terrestrial magnetism sensor of the present embodiment uses the calculation formula according to the turning direction based on two sets of X and Y data of the start point and the end point separated by the azimuth radius R. To calculate the center coordinates of the azimuth circle.

Therefore, there is no need to detect the azimuth of the vehicle to obtain the azimuth change amount and the like, and it is possible to determine the turning direction and calculate the center coordinates of the azimuth circle using a simple calculation formula. Also, in this calculation, for example, the distance difference β may be calculated as a square value, and can be calculated only by multiplication, subtraction, or the like.

As described above, the present invention is not limited to such embodiments at all, and can be implemented in various modes without departing from the gist of the present invention.

[Effects of the Invention] As described above in detail, the magnetization correction device for a geomagnetic azimuth sensor of the present invention does not need to detect the azimuth of the vehicle to obtain the azimuth change amount and the like, determine the turning direction, It is said that the coordinates can be calculated only by multiplication, subtraction, etc., and the center coordinates of the azimuth circle can be calculated with a simple calculation formula, so that the device is simplified, and it is possible to sufficiently correct the traveling direction even with an in-vehicle CPU. It works.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a basic configuration of a magnetization correction device for a geomagnetic azimuth sensor of the present invention, FIG. 2 is a schematic configuration diagram of a magnetization correction device for a geomagnetic azimuth sensor of the present embodiment, and FIG. FIG. 4 is a schematic configuration diagram of the geomagnetic direction sensor of the present embodiment, FIG. 4 is an explanatory diagram for explaining a relationship between two sets of points separated by an azimuth circle radius on an azimuth circle, and FIG. 5 is an electronic control circuit of the embodiment. 6 is a flowchart showing a radius calculation process of the present embodiment, FIG. 6 is a flowchart showing a magnetization correction process of the present embodiment, and FIG. FIG. 9 is an explanatory diagram for a left turn, and FIG. 9 is an explanatory diagram for calculating center coordinates of a plurality of azimuth circles at the time of a left turn.
The figure is an explanatory diagram when the center coordinates of the azimuth circle change due to magnetization. M1,1… geomagnetic direction sensor M2… turning direction detecting means, M3… data calculating means M4… center coordinate calculating means 12… turning direction detecting sensor, 20… electronic control circuit

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tohru Ito 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Yukihiko Umeda 1 Toyota Town Toyota City, Toyota City Inside Toyota Motor Corporation ( 56) References JP-A-64-38607 (JP, A) JP-A-63-94109 (JP, A) JP-A-63-94108 (JP, A) JP-A-59-100812 (JP, A) (58) ) Surveyed field (Int.Cl. ⁶ , DB name) G01C 17/38

Claims (1)

(57) [Claims] 1. A method according to claim 1, further comprising the step of: detecting a trajectory of X, Y data detected by a geomagnetic azimuth sensor which is attached to a moving body and detects an azimuth of geomagnetism by orthogonal X, Y components, based on a center coordinate of an azimuth circle. In the magnetization correction device for a terrestrial magnetism sensor that corrects the azimuth of terrestrial magnetism, a turning direction detecting unit that detects a turning direction of the moving body, and when the moving body turns, on the azimuth circle drawn by the X, Y data. Data calculating means for calculating two sets of X and Y data separated by the azimuth circle radius; two sets of X and Y data calculated by the data calculating means and the turning direction detected by the turning direction detecting means And a center coordinate calculating means for calculating center coordinates of the azimuth circle at the time of turning based on: