CN107024673B - Three axis magnetometer total error scaling method based on gyroscope auxiliary - Google Patents

Abstract

The present invention proposes a gyroscope-assisted three-axis magnetometer full-error calibration method, which is suitable for strapdown inertial navigation systems, mobile phones and other portable navigation devices. The sensor combination module uses the cuboid frame and the sensor combination module to calibrate the soft magnetic error, hard magnetic error, zero offset error, scale factor error, non-orthogonal error and installation error of the magnetometer. In a magnetic environment, the output data of the three-axis magnetometer and the three-axis gyroscope can be obtained by changing the orientation and rotation of the cuboid frame. The first step is to obtain the magnetometer interpolation output with equal rotation angle interval with the aid of the gyroscope output, and the second step is to obtain the error coefficient matrix and the calibration value of the zero offset vector by the linear operation of the magnetometer interpolation output. The method of the invention has the advantages of low equipment requirements, simple operation, short calibration time, small calculation amount and high precision.

Description

Full error calibration method of three-axis magnetometer based on gyroscope

technical field

The invention relates to the technical field of three-axis magnetometer calibration, in particular to a gyroscope-assisted full-error calibration method for a three-axis magnetometer.

Background technique

Due to the manufacturing error and assembly error of the three-axis magnetometer, as well as the interference of the external ferromagnetic object to the magnetic field, the accuracy of the measurement of the geomagnetic field is low. The error of the magnetometer comes from the environmental interference and the error of the magnetometer itself. Environmental interference includes hard magnetic interference and soft magnetic interference. The main errors of the magnetometer itself include zero bias error, scale factor error, non-orthogonal error, and installation alignment error. These errors seriously affect the accuracy of the magnetometer used in heading determination and attitude measurement. It needs to be calibrated to obtain the error coefficient and then compensate the original output of the magnetometer.

At present, there are many calibration methods, mainly including:

1. The magnetometer rotates once in the horizontal plane, and the maximum and minimum output values of the magnetometer are used to complete the calibration of the scale factor error and zero bias error of the 2-axis magnetometer. However, this method can only complete the 2-axis magnetometer calibration, and can only calibrate part of the error terms, and the accuracy is low.

2. Through the ellipsoid fitting calibration method of the rotating magnetometer in three-dimensional space, it cannot calibrate the rotation error term caused by soft magnetic interference, non-orthogonal error, and installation error, and the compensation effect is limited. The ball fitting process is computationally expensive.

3. Use a high-precision non-magnetic turntable to determine the direction, and obtain the magnetic field data through a higher-precision magnetometer, and determine the error coefficient through experiments. The correction accuracy is high, but the equipment requirements are high and the operation is complicated.

4. Fix the magnetometer in the cube, and solve the error coefficient of the magnetometer through 12 different placement orientations. However, this method has high requirements on the accuracy of the 12 orientations, and relies on fewer data points. When the random noise is large, it is easy to generate a large calibration error.

In general, the current related calibration methods have the disadvantages of high equipment requirements, complicated operations, complicated calculations, only completing the calibration of part of the error terms, and only suitable for the calibration of 2-axis magnetometers.

SUMMARY OF THE INVENTION

The present invention aims to solve at least one of the above-mentioned technical problems.

Therefore, the purpose of the present invention is to propose a gyroscope-assisted three-axis magnetometer full error calibration method, which has the advantages of low equipment requirements, simple operation, short calibration time, small calculation amount and high precision.

In order to achieve the above purpose, an embodiment of the present invention proposes a gyroscope-assisted three-axis magnetometer full error calibration method, comprising the following steps: S1: a three-axis gyroscope and a three-axis magnetometer are fixedly connected to form a The sensor combination module is installed in the cuboid frame, and the six sides of the frame are numbered 1 to 6 respectively. The numbering rule is: 1 and 2 are opposite and perpendicular to the z-axis of the sensor combination module, and 3 and 4 are opposite. And perpendicular to the y-axis of the sensor combination module, faces 5 and 6 are opposite, and perpendicular to the x-axis of the sensor combination module; S2: Set the number of rotations n, and place the frame number 1 on a smooth, non-magnetic plane. Rotate the frame around the axis perpendicular to the plane for more than n turns, and obtain a set of output data from the three-axis magnetometer and three-axis gyroscope; S3: Place the faces numbered 2 to 6 on a smooth, non-magnetic plane, respectively, and wind them around The axis perpendicular to the plane rotates the frame more than n turns, and obtains another 5 sets of output data of three-axis magnetometer and three-axis gyroscope; S4: Set the interpolation interval angle Δθ, and set the number k of the frame facing upward; S5 : The output of the gyroscope through the sensitive axis perpendicular to the plane of rotation Integrate to obtain the rotation angle θ _j of each sampling point, and stop the integration when θ _j ≥ 360n, and save the rotation angle θ of each sampling point; S6: According to the rotation angle θ of each sampling point and the output m of the three-axis magnetometer of each sampling point ^k , calculate the three-axis magnetometer interpolation output at equal angular intervals; S7: change the number k of the upward face of the frame, repeat steps S5 to S6, obtain another 5 sets of three-axis magnetometer interpolation output, and finally obtain the three-axis magnetometer Strong meter interpolation output i=1～360n/Δθ, k=1～6; S8: Calculate the zero bias error vector according to the finally obtained three-axis magnetometer interpolation output; S9: Obtain the magnetic field component h _⊥ perpendicular to the plane; S10: According to the three-axis Calculate the error coefficient matrix between the magnetometer interpolation output and the magnetic field component h _⊥ ; S11: Perform error compensation on the original output of the three-axis magnetometer according to the obtained zero bias error vector and the error coefficient matrix.

In addition, the gyroscope-assisted three-axis magnetometer full error calibration method according to the above embodiments of the present invention may also have the following additional technical features:

In some examples, in S6, the equiangularly spaced three-axis magnetometer interpolation output is calculated by the following formula:

In some examples, in the S8, the zero bias error vector is calculated by the following formula:

In some examples, in the S9, the magnetic field component h _⊥ is preset, or the magnetic field component h _⊥ is obtained by calculation through a preset formula.

In some examples, the preset formula is:

In some examples, in the S10, the error coefficient matrix is: K=[K ₁ K ₂ K ₃ ], wherein,

In some examples, in the S11, the method of performing error compensation on the raw output of the three-axis magnetometer is:

in, It is the output of the three-axis magnetometer after compensation.

In some examples, in the S5, the angle θ _j is the relative rotation angle.

In some examples, in the S4, the interpolation interval angle Δθ is a common divisor of 360.

The gyroscope-assisted three-axis magnetometer full error calibration method according to the embodiment of the present invention has the following advantages:

1. The implementation of this method has low requirements on equipment, and only needs to use a non-magnetic cuboid frame, and the sensor combination module in which the three-axis magnetometer and the three-axis gyroscope are fixedly connected is very common;

2. The method is simple to operate, and there is no requirement for north alignment for the flip of the magnetometer. The rotation process does not need to control the precise rotation angle, and there are no special requirements for the rotation speed and rotation direction;

3. This method is simple to calculate. The magnetometer interpolation output of equal angular intervals is obtained through linear interpolation, and then the magnetometer interpolation output is used to obtain the error coefficient matrix and zero-bias error vector through a linear equation. Solving problems such as systems of linear equations;

4. The method is simple to operate and simple to calculate, so that the time required for the calibration process is short;

5. The method effectively utilizes the gyroscope in the strapdown inertial navigation equipment to assist in completing the full error calibration of the magnetometer.

Additional aspects and advantages of the present invention will be set forth, in part, from the following description, and in part will be apparent from the following description, or may be learned by practice of the invention.

Description of drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of embodiments taken in conjunction with the accompanying drawings, wherein:

Fig. 1 is a three-axis magnetometer full error calibration method based on gyroscope assistance according to an embodiment of the present invention;

FIG. 2 is a schematic diagram showing the development of each side of a rectangular parallelepiped frame according to an embodiment of the present invention;

3 is a schematic diagram of the alignment relationship between a rectangular parallelepiped frame and a sensor mode sensitive axis according to an embodiment of the present invention;

4 is a schematic diagram of a rotating operation process according to an embodiment of the present invention;

5 is a schematic diagram of output values of three-axis magnetometers before and after calibration according to an embodiment of the present invention;

6 is a schematic diagram of the output values of the x and y-axis magnetometers before and after calibration according to an embodiment of the present invention;

7 is a schematic diagram of the output values of the x and z-axis magnetometers before and after calibration according to an embodiment of the present invention;

8 is a schematic diagram of the output values of the y and z-axis magnetometers before and after calibration according to an embodiment of the present invention;

FIG. 9 is a schematic diagram of the angle measurement error of the magnetometer before and after calibration according to an embodiment of the present invention.

Detailed ways

The following describes in detail the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary, only used to explain the present invention, and should not be construed as a limitation of the present invention.

The following describes a method for calibrating the full error of a three-axis magnetometer assisted by a gyroscope according to an embodiment of the present invention with reference to the accompanying drawings.

FIG. 1 is a flowchart of a method for calibrating the full error of a three-axis magnetometer based on a gyroscope according to an embodiment of the present invention. As shown in Figure 1, the method includes the following steps:

Step S1: Install the sensor combination module composed of the three-axis gyroscope and the three-axis magnetometer fixedly connected in the non-magnetic cuboid frame, and number the six faces of the frame as 1 to 6, wherein the numbering rule is: 1 Opposite to 2 and perpendicular to the z-axis of the sensor combination module, 3 and 4 are opposite and perpendicular to the y-axis of the sensor combination module, 5 and 6 are opposite and perpendicular to the sensor combination module x-axis, such as Figure 2 and Figure 2 3 shown.

Step S2: Set the number of rotations n, place the frame numbered 1 on a smooth and non-magnetic plane, and rotate the frame around the axis perpendicular to the plane for more than n turns to obtain a set of three-axis magnetometers and three-axis magnetometers. The gyroscope outputs data, and the specific rotation process is shown in Figure 4.

Step S3: Place the surfaces numbered 2 to 6 on a smooth, non-magnetic plane with the faces numbered 2 to 6 facing upwards, and rotate the frame around the axis perpendicular to the plane for more than n turns to obtain the output of another 5 sets of three-axis magnetometers and three-axis gyroscopes. data.

It should be noted that, in an embodiment of the present invention, in the above steps S2 and S3, there is no requirement for the levelness of the smooth surface, and there is no requirement for the orientation of the side when the magnetometer is placed. There is no requirement for the rotation direction of the hour hand, no requirement for the operation sequence of the upward face of the cuboid frame, and no requirement for the rotation speed.

Step S4: Set the interpolation interval angle Δθ, and set the number k of the frame facing upward.

Specifically, in an embodiment of the present invention, the interpolation interval angle Δθ is a common divisor of 360.

Step S5: Pass the output of the gyroscope perpendicular to the rotation plane through the sensitive axis The rotation angle θ _j of each sampling point is obtained by integration, and when θ _j ≥ 360n, the integration is stopped and the rotation angle θ of each sampling point is saved.

Specifically, in an embodiment of the present invention, the angle θ _j is a relative rotation angle.

Step S6: According to the rotation angle θ of each sampling point and the triaxial magnetometer output m ^k of each sampling point, calculate the triaxial magnetometer interpolation output at equal angular intervals.

Specifically, in one embodiment of the present invention, the three-axis magnetometer interpolation output of equal angular intervals is calculated by the following interpolation formula:

Step S7: Change the number k of the face of the frame facing upward, and repeat steps S5 to S6 to obtain another 5 sets of three-axis magnetometer interpolation output, and finally obtain the three-axis magnetometer interpolation output as: i=1～360n/Δθ, k=1～6.

Step S8: Calculate the zero bias error vector according to the finally obtained three-axis magnetometer interpolation output.

Specifically, in an embodiment of the present invention, the zero bias error vector is calculated by the following formula:

Step S9: Obtain the magnetic field component h _⊥ perpendicular to the plane.

Specifically, in an embodiment of the present invention, the magnetic field component h _⊥ is preset, or the magnetic field component h _⊥ is obtained by calculation through a preset formula. In other words, through known data, set the magnetic field component h _⊥ perpendicular to the plane, or calculate and obtain the magnetic field component h _⊥ perpendicular to the plane through a preset formula.

More specifically, the preset formula is, for example:

Step S10: Calculate the error coefficient matrix according to the interpolation output of the three-axis magnetometer and the magnetic field component h _⊥ .

Specifically, in an embodiment of the present invention, the error coefficient matrix is: K=[K ₁ K ₂ K ₃ ], where,

Step S11: Perform error compensation on the original output of the three-axis magnetometer according to the obtained zero bias error vector and error coefficient matrix.

Specifically, in an embodiment of the present invention, the method of performing error compensation on the original output of the three-axis magnetometer is:

in, It is the output of the three-axis magnetometer after compensation. Further, the reference value of the rotation angle is provided by the turntable, and the angle error calculated by the magnetometer before and after the calibration is compared. As a specific example, the output values of the three-axis magnetometer before and after calibration are shown in Fig. 5; the output values of the x and y-axis magnetometers before and after calibration are shown in Fig. 6; the output values of the x and z-axis magnetometers before and after calibration are shown in Fig. 7; the output values of the y and z-axis magnetometers before and after calibration are shown in Figure 8; the angle error of the three-axis magnetometer before and after calibration is shown in Figure 9. The angle measurement error of the strong meter is significantly reduced.

To sum up, the gyroscope-assisted three-axis magnetometer full error calibration method according to the embodiment of the present invention has the following advantages:

1. The implementation of this method has low requirements on equipment, and only needs to use a non-magnetic cuboid frame, and the sensor combination module in which the three-axis magnetometer and the three-axis gyroscope are fixedly connected is very common;

2. The method is simple to operate, and there is no requirement for north alignment for the flip of the magnetometer. The rotation process does not need to control the precise rotation angle, and there are no special requirements for the rotation speed and rotation direction;

3. This method is simple to calculate. The magnetometer interpolation output of equal angular intervals is obtained through linear interpolation, and then the magnetometer interpolation output is used to obtain the error coefficient matrix and zero-bias error vector through a linear equation. Solving problems such as systems of linear equations;

4. The method is simple to operate and simple to calculate, so that the time required for the calibration process is short;

5. The method effectively utilizes the gyroscope in the strapdown inertial navigation equipment to assist in completing the full error calibration of the magnetometer.

In order to facilitate a better understanding of the present invention, the following detailed exemplary description of the method for calibrating the full error of a three-axis magnetometer based on the gyroscope-assisted embodiment of the present invention is given in conjunction with specific embodiments.

Example 1

In this embodiment, the gyroscope-assisted three-axis magnetometer full error calibration method includes the following steps, for example:

a) Select the SBG IG-500N three-axis gyroscope and three-axis magnetometer sensor combination module, process the non-magnetic cuboid frame, and install the sensor module in the frame.

b) Install the sensor combination module of the three-axis magnetometer and the three-axis gyroscope in the cuboid frame, number the six sides of the frame from 1 to 6, and the numbering rule is: 1 and 2 are opposite, perpendicular to the sensor combination module z Axis; faces 3 and 4 are opposite and perpendicular to the y-axis of the sensor combination module; faces 5 and 6 are opposite and perpendicular to the x-axis of the sensor combination module.

c) Set the number of rotations n=2. Place the frame numbered 1 face up on a smooth, non-magnetic plane, rotate the frame around the axis perpendicular to the plane for more than n turns, and save the output data of a set of three-axis magnetometers and three-axis gyroscopes.

d) Place the numbered 2 to 6 faces on a smooth and non-magnetic plane respectively, and rotate the frame around the axis perpendicular to the plane for more than n turns to obtain the output data of another 5 sets of three-axis magnetometers and three-axis gyroscopes.

e) Set the interpolation interval angle Δθ=1°, and set the number k=1 of the face of the frame facing upward.

f) The output of the gyroscope through the sensitive axis perpendicular to the plane of rotation Integrate to obtain the rotation angle θ _j for each sample point. When θ _j ≥ 360n, stop the integration and save the rotation angle θ of each sampling point.

g) According to the rotation angle θ of each sampling point and the output m ^k of the three-axis magnetometer of each sampling point, the following interpolation formula is used:

Get the three-axis magnetometer interpolation output i=1 to 360n/Δθ.

h) Change the number k of the upward face of the frame, take k = 2 to 6 respectively, repeat steps e to f, and obtain another 5 sets of three-axis magnetometer interpolation outputs, and finally get i=1～360n/Δθ, k=1～6.

i) Calculate the zero bias error vector by the following formula:

j) Set the magnetic field component perpendicular to the plane h _⊥ , or calculate the magnetic field component perpendicular to the plane by the following formula:

k) Calculate the error coefficient matrix K=[K ₁ K ₂ K ₃ ] through the following formula, wherein,

l) Perform error compensation on the original output of the magnetometer from the zero bias error vector and error coefficient matrix obtained in step h and step j, and obtain the output after compensation:

m) Use the turntable to provide the reference value of the rotation angle, and compare the angle error calculated by the magnetometer before and after calibration.

To sum up, the gyroscope-assisted three-axis magnetometer full error calibration method according to the embodiment of the present invention has the following advantages:

1. The implementation of this method has low requirements on equipment, and only needs to use a non-magnetic cuboid frame, and the sensor combination module in which the three-axis magnetometer and the three-axis gyroscope are fixedly connected is very common;

2. The method is simple to operate, and there is no requirement for north alignment for the flip of the magnetometer. The rotation process does not need to control the precise rotation angle, and there are no special requirements for the rotation speed and rotation direction;

3. This method is simple to calculate. The magnetometer interpolation output of equal angular intervals is obtained through linear interpolation, and then the magnetometer interpolation output is used to obtain the error coefficient matrix and zero-bias error vector through a linear equation. Solving problems such as systems of linear equations;

4. The method is simple to operate and simple to calculate, so that the time required for the calibration process is short;

5. The method effectively utilizes the gyroscope in the strapdown inertial navigation equipment to assist in completing the full error calibration of the magnetometer.

In the description of this specification, description with reference to the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples", etc., mean specific features described in connection with the embodiment or example , structure, material or feature is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Although embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, The scope of the invention is defined by the claims and their equivalents.

Claims (9)

1. A gyroscope-assisted three-axis magnetometer total-error calibration method is characterized by comprising the following steps:

s1: install the sensor composite module that three-axis gyroscope and three-axis magnetometer linked firmly and constitute in the cuboid frame to six faces to the frame number respectively for 1 ~ 6, wherein, the numbering rule is: the 1 and 2 faces are opposite and vertical to a z axis of the combined sensor module, the 3 and 4 faces are opposite and vertical to a y axis of the combined sensor module, and the 5 and 6 faces are opposite and vertical to an x axis of the combined sensor module;

s2: setting the number of rotation turns n, placing the surface with the frame number 1 on a smooth and clean nonmagnetic plane, rotating the frame around an axis vertical to the plane for more than n turns to obtain 1 group of output data of the three-axis magnetometer and the three-axis gyroscope;

s3: respectively placing the surfaces with the numbers of 2-6 upwards on a smooth and clean non-magnetic plane, and rotating the frame around an axis vertical to the plane for more than n circles to obtain output data of the other 5 groups of three-axis magnetometers and three-axis gyroscopes;

s4: setting an interpolation interval angle delta theta and setting a number k of a face with the frame facing upwards;

s5: output of a gyroscope with sensitive axis perpendicular to the plane of rotationThe rotation angle theta of each sampling point is obtained by integration_jAnd when theta is_jStopping integration when the number is more than or equal to 360n, and storing the rotation angle theta of each sampling point;

s6: according to the rotation angle theta of each sampling point and the output m of the three-axis magnetometer of each sampling point^kCalculating the interpolation output of the triaxial magnetometer with equal angular intervals;

s7: changing the number k of the face with the frame facing upwards, repeating the steps S5 to S6 to obtain the interpolation output of the other 5 groups of the three-axis magnetometers, and finally obtaining the interpolation output of the three-axis magnetometers

S8: calculating a zero offset error vector according to the finally obtained interpolation output of the triaxial magnetometer;

s9: obtaining a magnetic field component h perpendicular to the plane_⊥；

S10: according to the interpolation output of the three-axis magnetometer and the magnetic field component h_⊥Calculating an error coefficient matrix;

s11: and according to the obtained zero offset error vector and the error coefficient matrix, carrying out error compensation on the original output of the triaxial magnetometer.

2. The gyroscope-assisted triaxial magnetometer-based full-error calibration method according to claim 1, wherein in the step S6, the interpolated output of equiangularly spaced triaxial magnetometers is calculated by the following formula:

3. the gyroscope-assisted three-axis magnetometer-based full-error calibration method according to claim 2, wherein in the step S8, the zero-offset error vector is calculated by the following formula:

4. the gyroscope-assisted three-axis magnetometer-based full-error calibration method according to claim 3, wherein in S9, the magnetic field component h_⊥The magnetic field component h is preset or calculated by a preset formula_⊥。

5. The gyroscope-assisted three-axis magnetometer-based full-error calibration method according to claim 4, wherein the preset formula is as follows:

6. the gyroscope-assisted three-axis magnetometer-based full-error calibration method according to claim 5, wherein in the step S10, the error coefficient matrix is: k ═ K₁ K₂ K₃]Wherein

7. the gyroscope-assisted three-axis magnetometer-based full-error calibration method according to claim 6, wherein in the step S11, the error compensation method for the original output of the three-axis magnetometer is as follows:

wherein,is the compensated output of the triaxial magnetometer.

8. The gyroscope-assisted three-axis magnetometer-based full-error calibration method according to claim 1, wherein in the step S5, the angle θ is_jIs a relative rotation angle.

9. The gyroscope-assisted three-axis magnetometer-based full-error calibration method according to claim 1, wherein in S4, the interpolation interval angle Δ θ is a common divisor of 360.