JP2000356519A - Magnetic direction sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic direction sensor which can detect a direction precisely even when a moving body is tilted. SOLUTION: A three-axis magnetic sensor 12 which measures respective components in three-axis directions of geomagnetism by using three geomagnetic sensors 15a to 15c arranged in three orthogonal axes is provided. A posture angle sensor 13 which measures the posture angle of a moving body is provided. A direction computing part 14 which computes a magnetic direction on the basis of the output of the three-axis magnetic sensor 12 and on the basis of the output of the posture angle sensor 13 is provided. Three axes of the three- axis magnetic sensor 12 are constituted so as to be deviated from the vertical axis in a state that the three-axis magnetic sensor 12 is installed at the moving body. In a state that the three-axis magnetic sensor 12 is installed at the moving body, all output sensitivities and all offset biases of the three geomagnetic sensors 15a to 15c can be adjusted easily.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic direction sensor mounted on a moving body such as an automobile.

[0002]

2. Description of the Related Art As a conventional magnetic azimuth sensor of this type, 3
There is a configuration in which three geomagnetic sensors are arranged on three orthogonal axes, the three geomagnetic sensors measure each component in the three orthogonal geomagnetic directions, and the magnetic azimuth is calculated from the measured components. In this magnetic azimuth sensor, the geomagnetic sensor is arranged on three axes of two orthogonal axes and a vertical axis in a horizontal plane.

In order to correct (adjust) the magnetic azimuth sensor, the whole moving body is rotated once in a horizontal plane in a state where the magnetic azimuth sensor is installed on the moving body, or a turntable which rotates in a horizontal plane is provided on the moving body. This is performed by measuring the change in geomagnetism with respect to the change in direction by rotating the turntable once with the magnetic direction sensor mounted, and based on this measurement,
The output sensitivity has been corrected and the offset bias generated due to the constituent material and structure of the moving body has been corrected.

[0004]

As described above, it has been conventionally performed to correct the sensitivity and the offset bias by rotating the magnetic azimuth sensor while mounted on a moving body. In the conventional magnetic azimuth sensor having the configuration as described above, the azimuth sensor arranged on the vertical axis does not change its azimuth even if rotated, that is, the terrestrial magnetism does not change. In this respect, there is a problem in the detection accuracy of the magnetic azimuth.

An object of the present invention is to provide a magnetic azimuth sensor capable of accurately detecting a magnetic azimuth in view of this problem.

[0006]

According to the present invention, a magnetic azimuth sensor is installed on a moving body and measures each component of terrestrial magnetism in three axial directions by three terrestrial magnetic sensors arranged on three orthogonal axes. An axis magnetic sensor, an attitude angle sensor for measuring the attitude angle of the moving body, and an azimuth calculation unit for calculating the magnetic azimuth from the output of the three-axis magnetic sensor and the output of the attitude angle sensor are installed on the moving body. In this state, all three axes of the three-axis magnetic sensor are deviated from the vertical axis.

[0007]

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention. In this example, a magnetic azimuth sensor 11 includes a three-axis magnetic sensor 12, an attitude angle sensor 13, and an azimuth calculation unit 14.

The three-axis magnetic sensor 12 has three geomagnetic sensors 15a, 15b, and 15c arranged on three orthogonal axes, and can measure each component of the earth magnetism in the three orthogonal axes. I have. Magnetic sensors 15a to 15
c is input to the signal processing unit 16 and the signal processing unit 16
Converts the magnetic flux detected by each of the magnetic sensors 15a to 15c into a voltage and outputs the voltage.

The attitude angle sensor 13 measures and outputs the attitude angle (pitch angle and roll angle) of the moving body. The attitude angle sensor 13 uses a gyro, for example. By using the gyro, the posture angle can be accurately detected even when the moving body is performing an acceleration movement. In addition,
A simple inclinometer may be used. Direction calculation 14
Calculates the magnetic azimuth from the output of the three-axis magnetic sensor 12 and the output of the attitude angle sensor 13 and outputs it. In this example, as shown in the figure, the azimuth calculation unit 14 has an input interface (input I / F) 17 to which output signals from the three-axis magnetic sensor 12 and the attitude angle sensor 13 are input, and the CPU 1 that performs calculation processing.
8. Output interface (output I /
F) The memory 20 is constituted by 19 and the memory 20.
May also be provided with a non-volatile memory for recording the correction value obtained by calculation.

The magnetic azimuth sensor 11 is mounted on a moving body 21 such as an automobile. At this time, the three-axis magnetic sensor 12 is installed as follows. That is, as shown in FIG. 2A, three line segments O adjacent to the apex angle O of the cube
When A, OB and OC are a-axis, b-axis and c-axis respectively,
In the figure, the geomagnetic sensor 15a is in the a-axis direction, and the geomagnetic sensor 15b is in the b-axis direction.
It is assumed that c is arranged in the c-axis direction, this cube is cut at the surface ABC, and the cut surface ABC is fixed on the horizontal plane of the moving body 21 as shown in FIG. At this time, when viewed from directly above, a
The axial direction (line segment OA) is set to overlap.

That is, in this example, three axes (a, b, c) detected by the three-axis magnetic
Axis) are all displaced from the vertical axis. Next, the operation of the magnetic azimuth sensor 11 configured as described above will be described. First, the geomagnetic sensors 15a-1
The correction (adjustment) of 5c will be described.

As shown in FIG. 3, a local horizontal plane at a certain point on the earth is considered, and the horizontal component (horizontal component) of the geomagnetic vector _BE at this point is represented by B _Lmax and the vertical component (vertical direction). Component) is B _Z. In the horizontal plane, when the azimuth angle に 対 し て is a clockwise angle with respect to the direction below the vertical axis with respect to magnetic north, the direction and magnitude of the geomagnetism in the horizontal plane, that is, the horizontal component B of the geomagnetism when rotated about the vertical axis _L (ψ) is represented by the following equation.

B _L (ψ) = B _Lmax · cosψ (1) FIG. 4 shows the relationship between B _L (ψ) and ψ.
On the other hand, the angle (dip) between the geomagnetic vector _BE and the horizontal plane
Let I be I, the vertical component B _{Z of} geomagnetism is expressed by the following equation. B _Z = B _Lmax · tanI (2) Here, assuming that the geomagnetic sensor whose detection axis is shifted from the vertical axis by an angle α is rotated around the vertical axis, the geomagnetism B input to this geomagnetic sensor is obtained. _R ([psi) is to become _{B R (ψ) = B L} (ψ) · sinα + B Z · cosα ··· (3). However, when the geomagnetic sensor is actually attached to the moving body and rotated about the vertical axis as a rotation axis, for example, the geomagnetism B _M (ψ) measured by the geomagnetic sensor due to the structure of the moving body is expressed by the following equation. It will be.

B _M (ψ) = {B _R (ψ)} · SF + BIAS (4) where SF: output sensitivity (1 if there is no error) BIAS: output offset bias Therefore, rotation around the vertical axis The sensitivity and the offset bias when the geomagnetic sensor is mounted on the moving body can be obtained by estimating the equation (4) by measuring at several places while performing the measurement.

For example, data may be obtained while rotating the moving body 360 degrees or more in a horizontal plane, and the SF may be obtained from the maximum value and the minimum value, or the SF may be obtained using the least square method. . If SF is obtained, BIAS can be easily obtained from the relationship between Expressions (3) and (4). In this way, the sensitivity error and the offset bias error of each of the three geomagnetic sensors 15a to 15c arranged on the three axes a, b, and c are obtained by rotating the moving body only once in the horizontal plane. Can be.

Next, three geomagnetic sensors 15a to 15c
The calculation of the magnetic azimuth in a state where the moving body 21 is tilted, that is, in the state where the pitch angle θ and the roll angle φ exist, will be described from the values measured in the above. The forward direction of the moving body is X, the right direction is Y, and the downward direction is Z, and three orthogonal axes of X, Y, and Z are referred to as moving body axes. At this time, since the relationship between the three orthogonal axes of the three geomagnetic sensors attached to the moving object and the axis of the moving object is invariable, conversion is performed using a rotation matrix RM of three rows and three columns.

[0017] _{Here, B a, B b, B} c geomagnetic sensor 15a~15
c _x and B _x , B
_Y and B _Z indicate geomagnetism (three rows) converted to the moving body axis.

When the moving body is inclined at a roll angle φ and a pitch angle θ, the moving body axis is converted into a horizontal and vertical plane by a rotation matrix RA (φ, θ) of 3 rows and 3 columns, and the moving body forward direction ( The horizontal projection component B _HX of the X axis) and its orthogonal component B _HY are obtained by the following equation. The orientation の (magnetic orientation) of the geomagnetic direction in the horizontal plane is
It can be obtained from _HX, B _HY by the following equation.

Ψ = tan ⁻¹ (B _HX / B _HY ) The azimuth calculation unit 14 performs the calculation in the correction of the magnetic sensors 15a to 15c and the calculation of the magnetic azimuth described above. The rotation operation for correcting the magnetic sensors 15a to 15c in each place is performed by rotating the whole of the moving body 21 once in a horizontal plane, or by providing a turntable on the moving body 21 and three axes on the same as in the conventional case. This is performed by mounting the magnetic sensor 12 and rotating the turntable once.

[0020]

As described above, according to the present invention, since the three orthogonal axes of the three-axis magnetic sensor are all displaced from the vertical axis in a state where they are installed on the moving body, for example, Is rotated once in the horizontal plane,
The correction value of the output sensitivity and the correction value of the offset bias of each of the three geomagnetic sensors arranged on the axis can be obtained, that is, the output sensitivity and the offset bias of all three geomagnetic sensors can be adjusted.

Therefore, a magnetic azimuth sensor having excellent detection accuracy can be obtained, and in particular, the azimuth can be accurately detected even when the moving body is tilted.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a diagram for explaining a method of installing a three-axis magnetic sensor on a moving body.

FIG. 3 is a diagram for explaining geomagnetic components and directions.

FIG. 4 is a graph showing a relationship between a horizontal component of terrestrial magnetism and an azimuth angle.

Claims (1)

[Claims] 1. A three-axis magnetic sensor which is installed on a moving body and measures each component of geomagnetism in three axial directions by three geomagnetic sensors arranged on three orthogonal axes, and measures an attitude angle of the moving body. An attitude angle sensor; and an azimuth calculating unit that calculates a magnetic azimuth from the output of the three-axis magnetic sensor and the output of the attitude angle sensor. A magnetic azimuth sensor wherein all axes are shifted from a vertical axis.