CN108088465A - A kind of magnetic heading online calibration method - Google Patents

Abstract

The invention belongs to the technical field of navigation parameter calibration, and in particular relates to an online calibration method for magnetic heading. When the attitude of the carrier changes, the track of the measured magnetic force of the three-axis magnetic sensor in space is a spherical shape. When affected by hard magnetism, the position of its center will change; after being affected by soft magnetism, its spherical shape will be distorted into an ellipse. The method of the present invention utilizes the above principles to measure the trajectory of the magnetic force in space through the rotation of the MEMS integrated navigation system on the UAV, and use the data fitting algorithm to compensate the disturbed ellipse into a circle, which can complete the magnetic sensor parameters. calibration. The present invention needs to solve the technical problems that the traditional calibration method for magnetic sensors mainly adopts the non-magnetic turntable multi-position calibration method, the calibration period is long, and the applicability is poor. It does not need to use a non-magnetic turntable, does not disassemble the MEMS integrated navigation system, and performs online calibration. The magnetic heading angle is calibrated, the calibration period is short, and the adaptability is good.

Description

A method for on-line calibration of magnetic heading

technical field

The invention belongs to the technical field of navigation parameter calibration, and in particular relates to an online calibration method for magnetic heading.

Background technique

The existing navigation systems for UAV flight control mostly use MEMS inertial/satellite/magnetic/air pressure multi-sensor integrated navigation. Due to the low accuracy of the MEMS inertial navigation system, it is impossible to find north, so it is necessary to use the magnetic heading to establish a heading reference for the initial alignment and navigation of the inertial navigation system.

However, there is ferromagnetic interference in the engine and other structural parts inside the UAV, which will cause the magnetic sensor parameters calibrated on the ground to be unusable on the UAV; in addition, many devices are magnetized during long-term use, resulting in the magnetic heading Navigation accuracy deteriorates during long-term use. However, the traditional calibration method for magnetic sensors mainly adopts the non-magnetic turntable multi-position calibration method, which has a long calibration cycle and poor applicability.

Contents of the invention

The technical problem to be solved in the present invention is: the traditional calibration method for magnetic sensors mainly adopts the non-magnetic turntable multi-position calibration method, which has a long calibration period and poor applicability.

Technical scheme of the present invention is as follows:

First, rotate the MEMS integrated navigation system for one circle, and collect 5 sample points during the process; then according to the elliptic equation:

Among them, H _x1i and H _y1i (i=1～5) are the original horizontal magnetic field strength, calculated by the following formula;

H _x1 ＝Mx cosθ+My sinθ

H _y1 ＝Mx sinθsinγ+My cosγ-Mz cosθsinγ

Mx, My, and Mz are the original magnetic field strengths in the three directions of XYZ in the front lower right coordinate system given by the magnetic sensor, where the X axis is forward, the Y axis is right, the Z axis is downward, and γ is the carrier The roll angle of , θ is the pitch angle of the carrier;

Then use the following formula to find the ellipse correlation coefficient:

Among them, σ is the oblateness of the ellipse, B _x and B _y are the positions of the center of the ellipse relative to the origin, K _x and K _y are the semi-major and semi-minor axes of the ellipse;

Then the compensated horizontal magnetic field strength is:

H _x ＝(H _x1 -B _x )/K _x

H _y =(H _y1 -B _y )/K _y

Among them, H _x is the forward magnetic field strength, H _y is the right magnetic field strength; then the magnetic heading angle ψ is calculated by the following formula:

ψ = arctan(H _y /H _x ).

The beneficial effects of the present invention are: the calibration method of the present invention does not need to use a non-magnetic turntable, does not dismantle the MEMS integrated navigation system, and can calibrate the magnetic heading angle online, with short calibration period and good adaptability.

Detailed ways

When the attitude of the carrier changes, the track of the measured magnetic force of the three-axis magnetic sensor in space is a spherical shape. When affected by hard magnetism, the position of its center will change; after being affected by soft magnetism, its spherical shape will be distorted into an ellipse. The method of the present invention utilizes the above principles to measure the trajectory of the magnetic force in space through the rotation of the MEMS integrated navigation system on the UAV, and use the data fitting algorithm to compensate the disturbed ellipse into a circle, which can complete the magnetic sensor parameters. calibration.

The original magnetic field strength in the three directions of XYZ in the front lower right coordinate system given by the magnetic sensor is: Mx, My, Mz, where the X axis is forward, the Y axis is right, the Z axis is downward, and the horizontal direction of the carrier is The roll angle is γ and the pitch angle is θ.

Then the original magnetic field strength in the horizontal direction obtained by attitude decomposition is:

In order to complete the online calibration of the magnetic heading, the MEMS integrated navigation system is first rotated for one revolution, and 5 sample points are collected during the process. Then according to the elliptic equation:

Wherein, H _x1i , _Hy1i (i=1-5) are original horizontal magnetic field strengths calculated by formula (1). Then the elliptic correlation coefficient can be obtained:

Among them, σ is the oblateness of the ellipse, B _x and _By are the positions of the center of the ellipse relative to the origin, K _x and K _y are the semi-major and semi-minor axes of the ellipse.

Then the compensated horizontal magnetic field strength is:

Then complete the magnetic heading solution:

ψ = arctan (H _y /H _x ) (5).

Claims (1)

1. A magnetic heading online calibration method, characterized in that: First, rotate the MEMS integrated navigation system for one circle, and collect 5 sample points during the process; then according to the elliptic equation: <mrow><mfenced open = "[" close = "]"><mtable><mtr><mtd><msub><mi>K</mi><mn>1</mn></msub></mrow>mtd></mtr><mtr><mtd><msub><mi>K</mi><mn>2</mn></msub></mtd></mtr><mtr><mtd><msub><mi>K</mi><mn>3</mn></msub></mtd></mtr><mtr><mtd><msub><mi>K</mi><mn>4</mn></msub></mtd></mtr><mtr><mtd><msub><mi>K</mi><mn>5</mn></msub></mtd></mtr></mtable></mfenced><mo>=</mo><msup><mfenced open = "[" close = "]"><mtable><mtr><mtd><mrow><msub><mi>H</mi><mrow><mi>x</mi><mn>11</mn></mrow></msub><msub><mi>H</mi><mrow><mi>y</mi><mn>11</mn></mrow></msub></mrow></mtd><mtd><msubsup><mi>H</mi><mrow><mi>y</mi><mn>11</mn></mrow><mn>2</mn></msubsup></mtd><mtd><msub><mi>H</mi><mrow><mi>x</mi><mn>11</mn></mrow></msub></mtd><mtd><msub><mi>H</mi><mrow><mi>y</mi><mn>11</mn></mrow></msub></mtd><mtd><mn>1</mn></mtd></mtr><mtr><mtd><mrow><msub><mi>H</mi><mrow><mi>x</mi><mn>12</mn></mrow></msub><msub><mi>H</mi>mi><mrow><mi>y</mi><mn>12</mn></mrow></msub></mrow></mtd><mtd><msubsup><mi>H</mi><mrow><mi>y</mi>mi><mn>12</mn></mrow><mn>2</mn></msubsup></mtd><mtd><msub><mi>H</mi><mrow><mi>x</mi><mn>12</mn></mrow></msub></mtd><mtd><msub><mi>H</mi><mrow><mi>y</mi><mn>12</mn></mrow></msub></mtd><mtd><mn>1</mn></mtd></mtr><mtr><mtd><mrow><msub><mi>H</mi><mrow><mi>x</mi><mn>13</mn></mrow></msub><msub><mi>H</mi><mrow><mi>y</mi><mn>13</mn></mrow></msub></mrow></mtd><mtd><msubsup><mi>H</mi><mrow><mi>y</mi><mn>13</mn></mrow><mn>2</mn></msubsup></mtd><mtd><msub><mi>H</mi><mrow><mi>x</mi><mn>13</mn></mrow></msub></mtd><mtd><msub><mi>H</mi><mrow><mi>y</mi><mn>13</mn></mrow></msub></mtd><mtd><mn>1</mn></mtd></mtr><mtr><mtd><mrow><msub><mi>H</mi><mrow><mi>x</mi><mn>14</mn></mrow></msub><msub><mi>H</mi>mi><mrow><mi>y</mi><mn>14</mn></mrow></msub></mrow></mtd><mtd><msubsup><mi>H</mi><mrow><mi>y</mi><mn>14</mn></mrow><mn>2</mn></msubsup></mtd><mtd><msub><mi>H</mi><mrow><mi>x</mi><mn>14</mn></mrow></msub></mtd><mtd><msub><mi>H</mi><mrow><mi>y</mi><mn>14</mn></mrow></msub></mtd><mtd><mn>1</mn></mtd></mtr><mtr><mtd><mrow><msub><mi>H</mi><mrow><mi>x</mi><mn>15</mn></mrow></msub><msub><mi>H</mi><mrow><mi>y</mi><mn>15</mn></msub>mrow></msub></mrow></mtd><mtd><msubsup><mi>H</mi><mrow><mi>y</mi><mn>15</mn></mrow><mn>2</mn></msubsup></mtd><mtd><msub><mi>H</mi><mrow><mi>x</mi><mn>15</mn></mrow></msub></mtd><mtd><msub><mi>H</mi><mrow><mi>y</mi><mn>15</mn></mrow></msub></mtd><mtd><mn>1</mn></mtd></mtr></mtable></mfenced><mrow><mo>-</mo><mn>1</mn></mrow></msup><mo>&amp;CenterDot;</mo><mfenced open = "[" close = "]"><mtable><mtr><mtd><mrow><mo>-</mo><msubsup><mi>H</mi><mrow><mi>x</mi><mn>11</mn></mrow><mn>2</mn></msubsup></mrow></mtd></mtr><mtr><mtd><mrow><mo>-</mo><msubsup><mi>H</mi><mrow><mi>x</mi><mn>12</mn></mrow><mn>2</mn></msubsup></mrow></mtd></mtr><mtr><mtd><mrow><mo>-</mo><msubsup><mi>H</mi><mrow><mi>x</mi><mn>13</mn></mrow><mn>2</mn></msubsup></mrow></mtd></mtr><mtr><mtd><mrow><mo>-</mo><msubsup><mi>H</mi><mrow><mi>x</mi><mn>14</mn></mrow><mn>2</mn></msubsup></mrow></mtd></mtr><mtr><mtd><mrow><mo>-</mo><msubsup><mi>H</mi><mrow><mi>x</mi><mn>15</mn></mrow><mn>2</mn></msubsup></mrow></mtd></mtr></mtable></mfenced></mrow> Among them, H _x1i and H _y1i (i=1～5) are the original horizontal magnetic field strength, calculated by the following formula; H _x1 ＝Mxcosθ+Mysinθ H _y1 ＝Mxsinθsinγ+Mycosγ-Mzcosθsinγ Mx, My, and Mz are the original magnetic field strengths in the three directions of XYZ in the front lower right coordinate system given by the magnetic sensor, where the X axis is forward, the Y axis is right, the Z axis is downward, and γ is the carrier The roll angle of , θ is the pitch angle of the carrier; Then use the following formula to find the ellipse correlation coefficient: <mfenced open = "{" close = ""><mtable><mtr><mtd><mrow><mi>&amp;sigma;</mi><mo>=</mo><mn>0.5</mn><mi>a</mi><mi>r</mi><mi>c</mi><mi>t</mi><mi>a</mi><mi>n</mi><mrow><mo>(</mo><msub><mi>K</mi><mn>2</mn></msub><mo>/</mo><mo>(</mo><mrow><msub><mi>K</mi><mn>1</mn></msub><mo>-</mo><mn>1</mn></mrow><mo>)</mo><mo>)</mo></mrow></mrow></mtd></mtr><mtr><mtd><mrow><msub><mi>B</mi><mi>x</mi></msub><mo>=</mo><mfrac><mrow><mo>-</mo><mn>2</mn><msub><mi>K</mi><mn>1</mn></msub><msub><mi>K</mi><mn>3</mn></msub><mo>+</mo><msub><mi>K</mi><mn>2</mn></msub><msub><mi>K</mi><mn>4</mn></msub></mrow><mrow><mn>4</mn><msub><mi>K</mi><mn>1</mn></msub><mo>-</mo><msubsup><mi>K</mi><mn>2</mn><mn>2</mn></msubsup></mrow></mfrac></mrow></mtd></mtr><mtr><mtd><mrow><msub><mi>B</mi><mi>y</mi></msub><mo>=</mo><mfrac><mrow><mo>-</mo><mn>2</mn><msub><mi>K</mi><mn>4</mn></msub><mo>+</mo><msub><mi>K</mi><mn>2</mn></msub><msub><mi>K</mi><mn>3</mn></msub></mrow><mrow><mn>4</mn><msub><mi>K</mi><mn>1</mn></msub><mo>-</mo><msubsup><mi>K</mi><mn>2</mn><mn>2</mn></msubsup></mrow></mfrac></mrow></mtd></mtr><mtr><mtd><mrow><msub><mi>K</mi><mi>x</mi></msub><mo>=</mo><msqrt><mfrac><mn>2</mn><mrow><mn>1</mn><mo>-</mo><msub><mi>K</mi><mn>1</mn></msub><mo>-</mo><msub><mi>K</mi><mn>2</mn></msub><mo>/</mo><mi>s</mi><mi>i</mi><mi>n</mi><mrow><mo>(</mo><mn>2</mn><mi>&amp;sigma;</mi><mo>)</mo></mrow></mrow></mfrac></msqrt></mrow></mtd></mtr><mtr><mtd><mrow><msub><mi>K</mi><mi>y</mi></msub><mo>=</mo><msqrt><mfrac><mn>2</mn><mrow><mn>1</mn><mo>+</mo><msub><mi>K</mi><mn>1</mn></msub><mo>+</mo><msub><mi>K</mi><mn>2</mn></msub><mo>/</mo><mi>s</mi><mi>i</mi><mi>n</mi><mrow><mo>(</mo><mn>2</mn><mi>&amp;sigma;</mi><mo>)</mo></mrow></mrow></mfrac></msqrt></mrow></mtd></mtr></mtable></mfenced> Among them, σ is the oblateness of the ellipse, B _x and B _y are the positions of the center of the ellipse relative to the origin, K _x and K _y are the semi-major and semi-minor axes of the ellipse; Then the compensated horizontal magnetic field strength is: H _x ＝(H _x1 -B _x )/K _x H _y =(H _y1 -B _y )/K _y Among them, H _x is the forward magnetic field strength, H _y is the right magnetic field strength; then the magnetic heading angle ψ is calculated by the following formula: ψ = arctan(H _y /H _x ).