A method for calibrating error parameters of a three-axis orthogonal coil

Abstract

The present disclosure relates to a method for calibrating three-axis orthogonal coil error parameters, which is applied to a zero magnetic device, the three-axis orthogonal coil is arranged in the interior of the zero magnetic device and closely adheres to the inner wall of the zero magnetic device, the method comprises: calibrating a uniform magnetic field coordinate system distributed in the zero magnetic device; based on the calibrated uniform magnetic field coordinate system, calibrating a magnetic field generation direction of the three-axis orthogonal coil; establishing an orthogonal error model of the three-axis orthogonal coil, and calibrating error parameters in the orthogonal error model. Thus, by calibrating the uniform magnetic field coordinate system in the zero magnetic device, the error between the uniform magnetic field coordinate system and the orthogonal coordinate system of the magnetic field measuring instrument is eliminated, and on this basis, the magnetic field generation direction of the three-axis coil and the error parameters are calibrated, which is conducive to improving the measurement accuracy.

Description

Technical Field

[0001] This disclosure relates to fields such as magnetocardiography testing, magnetoencephalography testing, space exploration, positioning and navigation, and geological exploration, and in particular to a method for calibrating the error parameters of a triaxial orthogonal coil. Background Technology

[0002] Uniform magnetic fields have wide applications in precision measurement, aerospace, and biomagnetic field measurement. The space magnetic environment is a crucial component of the space field environment, and its simulation is of great significance for the detection and research of the space physical environment. Space science missions exploring space magnetic fields, dynamic plasmas, and energy particles require not only high precision in the magnetic measurement instruments themselves but also that the magnetism of the spacecraft itself does not interfere with the measurement results. Furthermore, in the field of bioelectromagnetism, the atoms, molecules, cells, tissues, and organs that make up living organisms each possess unique intrinsic electromagnetic energy information. A zero-magnetic-field environment can provide an ideal environment for accurately obtaining the magnetic properties of biological tissues, ensuring understanding of the manifestation of biomagnetism in life activities, and thus enabling research on the magnetic properties of organisms. Studying the mechanisms and laws of zero-magnetic and weak-magnetic biological effects is fundamental to human exploration of outer space and simultaneously supports basic research in life sciences.

[0003] The lower the ambient magnetic field, the higher the accuracy of the magnetometer. To achieve extremely high accuracy in magnetic field measurements, a combination of passive magnetic shielding and active magnetic compensation is typically used. However, passive magnetic shielding can only reduce the spatial magnetic field to a certain level. To obtain an even lower ambient magnetic field, a triaxial compensation coil is needed to compensate for residual magnetism. This involves symmetrically installing a pair of coils along the X, Y, and Z axes to form a triaxial magnetic field generator. When current is applied, the triaxial coil generates a uniform magnetic field region in its central area. However, triaxial uniform coils inevitably have installation errors. These errors, along with environmental noise, can lead to inaccuracies in the mapping relationship between the magnetic field and current generated by the triaxial coil, thus affecting measurement accuracy. Summary of the Invention

[0004] To address the aforementioned technical problems, this disclosure provides a method for calibrating the error parameters of a triaxial orthogonal coil.

[0005] This disclosure provides a method for calibrating the error parameters of a triaxial orthogonal coil, applied to a zero-magnetic device. The triaxial orthogonal coil is disposed inside the zero-magnetic device, close to the inner wall of the device. The calibration method includes:

[0006] The coordinate system of the uniform magnetic field distributed within the zero-magnetic device is calibrated;

[0007] Based on the calibrated uniform magnetic field coordinate system, the direction of the magnetic field generated by the triaxial orthogonal coil is calibrated.

[0008] An orthogonal error model for the three-axis orthogonal coil is established, and the error parameters in the orthogonal error model are calibrated.

[0009] Optionally, the uniform magnetic field coordinate system includes a first coordinate axis, a second coordinate axis, and a third coordinate axis;

[0010] The calibration of the coordinate system of the uniform magnetic field distributed within the zero-magnetic device includes:

[0011] The calibrated fluxgate sensor is placed at the center of the zero-magnetic device; wherein the coordinate system of the fluxgate sensor includes a fourth coordinate axis, a fifth coordinate axis, and a sixth coordinate axis that are mutually perpendicular.

[0012] Adjust the position of the fourth coordinate axis of the fluxgate sensor so that the direction of the fourth coordinate axis is aligned with the direction of the largest change in magnetic field value, and determine the direction of the fourth coordinate axis of the fluxgate sensor as the direction of the first coordinate axis of the uniform magnetic field coordinate system.

[0013] Adjust the position of the fifth coordinate axis of the fluxgate sensor while keeping the position of the fourth coordinate axis of the fluxgate sensor fixed during the adjustment process, so that the direction of the fifth coordinate axis is aligned with the direction of the largest change in magnetic field value, and determine the direction of the fifth coordinate axis of the fluxgate sensor as the direction of the second coordinate axis of the uniform magnetic field coordinate system.

[0014] The direction of the sixth coordinate axis of the fluxgate sensor is determined to be the direction of the third coordinate axis of the uniform magnetic field coordinate system.

[0015] Optionally, calibrating the magnetic field generation direction of the triaxial orthogonal coil based on the calibrated uniform magnetic field coordinate system includes:

[0016] The direction of the first magnetic field generated by the triaxial orthogonal coil is determined to coincide with the direction of the first coordinate axis.

[0017] The direction of the second magnetic field generated by the triaxial orthogonal coil is determined to be on the plane formed by the direction of the first coordinate axis and the direction of the second coordinate axis, and the angle between the direction of the second magnetic field generated and the direction of the second coordinate axis is the first deviation angle;

[0018] The angle between the direction of the third magnetic field generated by the triaxial orthogonal coil and the plane formed by the directions of the second and third coordinate axes is defined as the second deviation angle, and the angle between the direction of the third magnetic field generated and the plane formed by the directions of the first and third coordinate axes is defined as the third deviation angle.

[0019] Optionally, establishing the orthogonal error model of the triaxial orthogonal coil and calibrating the error parameters in the orthogonal error model includes:

[0020] Establish the orthogonal error model of the three-axis orthogonal coil and determine the error parameters to be calibrated;

[0021] Three independent high-precision DC power supplies are used to supply a preset current I to the triaxial orthogonal coils. x I y and I z Record the triaxial magnetic field strength B measured by the fluxgate sensor for each set of currents. xf B yf and B zf Among them, the preset current I x I y and I z It is necessary to cover 8 quadrants in space, collect M sample data in each quadrant, and collect N sample data in total, where M and N are positive integers and N is greater than or equal to the number of error parameters;

[0022] Substitute the preset current and the corresponding triaxial magnetic field strength into the orthogonal error model to obtain the calibration value of the error parameter.

[0023] Optionally, a preset current I is applied to the triaxial orthogonal coil using three independent high-precision DC power supplies. x I y and I z Previously, it also included:

[0024] Based on the estimated coil constant k′ of the triaxial orthogonal coil xc 、k′ yc and k′ zc Determine the preset current I x I y and I z The amplitude;

[0025] Among them, the preset current I x I y and I z The magnitude of the generated triaxial vector magnetic field. It equals the preset amplitude.

[0026] Optionally, establishing the orthogonal error model of the triaxial orthogonal coil and determining the error parameters to be calibrated includes:

[0027] Obtain the remanence b of the fluxgate sensor along its three axes in the calibrated uniform magnetic field coordinate system. xf0 b yf0 and b zf0 ;

[0028] Based on the remanence, the orthogonal error model is established;

[0029] The error parameters to be calibrated include the coil constant k. xc k yc and k zc Non-orthogonal error angle α c β c and γ c and zero bias b xc0 b yc0 and b zc0 ;

[0030] Where, k xc k yc and k ac α represents the proportionality coefficient between the magnetic field strength and the current generated by each axis coil. c Corresponding to the first deviation angle, β c Corresponding to the second deviation angle; γ c Corresponding to the third deviation angle; b xc0 b yc0 and b zc0 This indicates the amount of residual magnetism of each shaft coil at the center position of the zero-magnetic device.

[0031] Optionally, establishing the orthogonal error model based on the remanence includes:

[0032] Based on the remanence, the formula for the orthogonal error model is determined as follows:

[0033] B xf =k xc I x cosβ c cosγ c +b xf0

[0034] B yf =k xc I x cosβ c sinγ c +k yc I y cosα c +b yf0

[0035] B zf =k xc I x sinβ c +k yc I y sinα c +k zc I z +b zf0 ;

[0036] Based on the conversion relationship between the remanence and zero bias, the formula for determining the orthogonal error model using the data fitting method is as follows:

[0037]

[0038] Optionally, placing the calibrated fluxgate sensor at the center of the zero-magnetic device includes:

[0039] The preheated fluxgate sensor is fixed to the three-axis non-magnetic turntable inside the zero-magnetic device;

[0040] By adjusting the three-axis non-magnetic turntable, the fluxgate sensor is positioned at the center of the zero-magnetic device, and the coordinate system of the fluxgate sensor coincides with the geomagnetic coordinate system.

[0041] The technical solution provided in this disclosure has the following advantages compared with the prior art:

[0042] This disclosure provides a calibration method for the error parameters of a triaxial orthogonal coil. This calibration method is applied to a zero-magnetic device, where the triaxial orthogonal coil is disposed inside the zero-magnetic device, close to its inner wall. The calibration method includes: calibrating the coordinate system of a uniform magnetic field distributed within the zero-magnetic device; calibrating the magnetic field generation direction of the triaxial orthogonal coil based on the calibrated uniform magnetic field coordinate system; establishing an orthogonal error model of the triaxial orthogonal coil; and calibrating the error parameters in the orthogonal error model. Therefore, by calibrating the coordinate system of the uniform magnetic field within the zero-magnetic device, the error between the uniform magnetic field coordinate system and the orthogonal coordinate system of the magnetic field measuring instrument is eliminated. Furthermore, calibrating the magnetic field generation direction and error parameters of the triaxial coil on this basis helps improve measurement accuracy. Attached Figure Description

[0043] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0044] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1-3 This is a schematic diagram of the zero-magnetic device provided in an embodiment of the present disclosure;

[0046] Figure 4 A flowchart illustrating a method for calibrating error parameters of a triaxial orthogonal coil provided in an embodiment of this disclosure;

[0047] Figure 5 for Figure 4 A detailed flowchart of S110 in the calibration method for the error parameters of the triaxial orthogonal coil is shown.

[0048] Figure 6 for Figure 5 A detailed flowchart of S211 in the calibration method for the error parameters of the triaxial orthogonal coil is shown.

[0049] Figure 7 This is a schematic diagram showing the spatial positions of the geomagnetic coordinate system and the calibrated uniform magnetic field coordinate system (i.e., the fluxgate sensor coordinate system) provided in the embodiments of this disclosure.

[0050] Figure 8 for Figure 4 A detailed flowchart of S120 in the calibration method for the error parameters of the triaxial orthogonal coil is shown.

[0051] Figure 9 This is a schematic diagram of the spatial position of the fluxgate sensor coordinate system and the triaxial orthogonal coil coordinate system provided in the embodiments of this disclosure;

[0052] Figure 10 for Figure 4 A detailed flowchart of S130 in the calibration method for the error parameters of the triaxial orthogonal coil is shown.

[0053] Figure 11 for Figure 10 The diagram shows a refined process flow diagram of S531 in the calibration method for the error parameters of the triaxial orthogonal coil. Detailed Implementation

[0054] To better understand the above-mentioned objectives, features, and advantages of this disclosure, the solutions disclosed herein will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0055] Numerous specific details are set forth in the following description in order to provide a full understanding of this disclosure, but this disclosure may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some, and not all, of the embodiments of this disclosure.

[0056] To address the technical problems raised in the background section, this disclosure provides a calibration method for the error parameters of a triaxial orthogonal coil. This calibration method is applied to a zero-magnetic device, where the triaxial orthogonal coil is disposed inside the device, close to its inner wall. The calibration method includes: calibrating the coordinate system of a uniform magnetic field distributed within the zero-magnetic device; calibrating the magnetic field generation direction of the triaxial orthogonal coil based on the calibrated uniform magnetic field coordinate system; establishing an orthogonal error model of the triaxial orthogonal coil; and calibrating the error parameters in the orthogonal error model. Therefore, by calibrating the coordinate system of the uniform magnetic field within the zero-magnetic device, the error between the uniform magnetic field coordinate system and the orthogonal coordinate system of the magnetic field measuring instrument is eliminated. Furthermore, calibrating the magnetic field generation direction and error parameters of the triaxial coil on this basis improves measurement accuracy.

[0057] The following is combined Figures 1-11 This document provides an exemplary description of a method for calibrating the error parameters of a triaxial orthogonal coil, based on embodiments of the present disclosure.

[0058] Figure 1-3 This is a schematic diagram of the zero-magnetic device provided in an embodiment of this disclosure. (Refer to...) Figure 1-3 The zero-magnetic device includes a shielding device 1 and three orthogonal coils. The shielding device 1 is constructed from multiple nested layers of high-permeability materials, such as permalloy or aluminum alloy. The shielding device 1 divides the space into an internal and external region, using the ferromagnetic boundaries formed by the high-permeability materials to protect the internal region from external magnetic field interference. To reduce residual magnetism within the shielding device 1 and expand the uniform magnetic field region within it, rectangular magnetic field coils are wound along three orthogonal axes at the center of the shielding device 1. Each of the three orthogonal coils carries a direct current in the same direction, generating a controllable magnetic field in the central region of the shielding device 1. This allows control over the central magnetic field of the shielding device 1 to be zero, and expands the range of the zero-magnetic-field uniform region. The three orthogonal coils are designated as first-axis coil 2, second-axis coil 3, and third-axis coil 4, with each pair of coils perpendicular to the others. Figure 1 Only the first shaft coil 2 is shown in the image. Figure 2 Only the second shaft coil 3 is shown in the image. Figure 3 Only the third-axis coil 4 is shown; the three-axis coil is close to the inner wall of the shielding device 1, and its shape and size correspond to the inner surface of the shielding device; by setting each group of coils in the three-axis orthogonal coil to a preset number of turns and pass current in the same direction, the magnetic field outside the coil can be rapidly attenuated, and the magnetic moment of the coil is zero; when working, it will not produce magnetic interference to the environment outside the preset distance, nor will it magnetize nearby magnetic materials, thus avoiding additional errors.

[0059] What is understandable is that Figure 1-3The shielding device 1 is shown as a cuboid only, and does not constitute a limitation on the calibration method for the triaxial orthogonal coil error parameters provided in the embodiments of this disclosure. In other embodiments, the shielding device 1 may also be configured as other shapes, such as a spherical polyhedron or a cylinder, which are not limited herein.

[0060] Under the combined action of shielding device 1 and triaxial orthogonal coils, a uniform magnetic field is formed in the internal region of shielding device 1. The direction of the uniform magnetic field coordinate system is influenced by both the magnetic field generation direction of the triaxial orthogonal coils and the geomagnetic coordinate system (external environment). Ideally, the magnetic field generation direction of the triaxial orthogonal coils coincides with the geomagnetic coordinate system, so that the direction of the uniform magnetic field coordinate system also coincides with the magnetic field generation direction of the triaxial orthogonal coils and the geomagnetic coordinate system, thus achieving high accuracy. However, in reality, the triaxial uniform coils inevitably have installation errors, causing a deviation between the coordinate system direction of the uniform magnetic field and the magnetic field generation direction of the triaxial orthogonal coils. This results in an error in the mapping relationship between the magnetic field and current generated by the triaxial orthogonal coils, which affects the accuracy of the measurement results. Therefore, it is necessary to calibrate the error parameters of the triaxial orthogonal coils.

[0061] Figure 4 This is a flowchart illustrating a method for calibrating the error parameters of a triaxial orthogonal coil according to an embodiment of this disclosure. The calibration method is applied to a zero-magnetic device, where the triaxial orthogonal coil is disposed inside the zero-magnetic device, close to the inner wall of the device, and referenced... Figure 4 The calibration method includes:

[0062] S110. The coordinate system of the uniform magnetic field distributed within the zero-magnetic device is calibrated.

[0063] Specifically, a fluxgate sensor is used to calibrate the uniform magnetic field distributed within the zero-magnetic device. By sequentially adjusting the three coordinate axes of the fluxgate sensor, the coordinate axes of the fluxgate sensor are made to coincide with the corresponding coordinate axes in the uniform magnetic field coordinate system. Thus, the directions of the three coordinate axes of the fluxgate sensor are the directions of the three coordinate axes in the uniform magnetic field coordinate system. The calibrated uniform magnetic field coordinate system is an orthogonal coordinate system.

[0064] S120. Based on the calibrated uniform magnetic field coordinate system, the direction of the magnetic field generated by the triaxial orthogonal coil is calibrated.

[0065] Specifically, using the calibrated uniform magnetic field coordinate system as a reference, the magnetic field generation direction of the triaxial orthogonal coil is calibrated based on its relative position to the orthogonal coordinate system. For example, the first magnetic field generation direction of the triaxial orthogonal coil is defined to coincide with the first coordinate axis of the uniform magnetic field coordinate system; the angle between the second magnetic field generation direction and the second coordinate axis of the uniform magnetic field coordinate system is defined as the first deviation angle; the angle between the third magnetic field generation direction and the plane formed by the third and second coordinate axes of the uniform magnetic field coordinate system is defined as the second deviation angle; and the angle between the third magnetic field generation direction and the plane formed by the third and first coordinate axes of the uniform magnetic field coordinate system is defined as the third deviation angle.

[0066] S130. Establish an orthogonal error model for the three-axis orthogonal coil and calibrate the error parameters in the orthogonal error model.

[0067] The purpose of this calibration method is to reduce or eliminate errors in the mapping relationship between the magnetic field and current generated by the triaxial orthogonal coil. Influencing factors include at least the proportionality coefficient between the magnetic field strength and current generated by each axis coil, the deviation angle between the direction of the magnetic field generated by the triaxial orthogonal coil and the orthogonal coordinate system of the uniform magnetic field (actual magnetic field), and the remanence of the triaxial orthogonal coil at the center position of the zero-magnetic device. The error parameters for determining the orthogonal error model include the coil constant k. xc k yc and k zc Non-orthogonal error angle α c β c and γ c and zero bias b xc0 b yc0 and b zc0 ; where k xc k yc and k zc α represents the proportionality coefficient between the magnetic field strength and the current generated by each axis coil. c β c and γ c These correspond to the deviation angles between the magnetic field generation direction of the triaxial orthogonal coil and the coordinate system of the uniform magnetic field, respectively. xc0 b yc0 and b zc0 This indicates the amount of residual magnetism of each shaft coil at the center position of the zero-magnetic device.

[0068] Specifically, by passing a preset current through a triaxial orthogonal coil and obtaining the corresponding triaxial magnetic field strength, multiple sets of preset currents and corresponding triaxial magnetic field strengths are substituted into the orthogonal error model formula, and the calibration value of the error parameter is obtained by using a data fitting algorithm.

[0069] This disclosure provides a calibration method for the error parameters of a triaxial orthogonal coil. This calibration method is applied to a zero-magnetic device, where the triaxial orthogonal coil is disposed inside the device and close to its inner wall. The calibration method includes: calibrating the coordinate system of a uniform magnetic field distributed within the zero-magnetic device; calibrating the magnetic field generation direction of the triaxial orthogonal coil based on the calibrated uniform magnetic field coordinate system; establishing an orthogonal error model of the triaxial orthogonal coil; and calibrating the error parameters in the orthogonal error model. Therefore, by calibrating the uniform magnetic field coordinate system within the zero-magnetic device, the error between the uniform magnetic field coordinate system and the orthogonal coordinate system of the magnetic field measuring instrument is eliminated. Furthermore, calibrating the magnetic field generation direction and error parameters of the triaxial coil on this basis improves measurement accuracy.

[0070] In some embodiments, such as Figure 5 As shown, Figure 4 The diagram shows a refined flowchart of step S110 in the calibration method for the error parameters of the triaxial orthogonal coil. (Refer to...) Figure 5 The uniform magnetic field coordinate system includes the first coordinate axis Z. o The second coordinate axis Y o and the third coordinate axis X o S110 "Calibration of the coordinate system of the uniform magnetic field distributed within the zero-magnetic device" includes:

[0071] S211. Place the calibrated fluxgate sensor at the center of the zero-magnetic device.

[0072] The coordinate system of the fluxgate sensor includes a fourth coordinate axis Z that is mutually perpendicular to each other. f The fifth coordinate axis Y f and the sixth coordinate axis X f That is, the coordinate system of the fluxgate sensor is a three-axis orthogonal coordinate system.

[0073] A uniform magnetic field is formed under the combined influence of a triaxial orthogonal coil and the external environment. The coordinate system of the magnetic field in the external environment (i.e., the geomagnetic field) is relatively fixed; the geomagnetic coordinate system is defined as a triaxial orthogonal coordinate system. For example, combining... Figure 1-3 The geomagnetic coordinate system X can be defined. g Y g and Z g These represent the width, thickness, and height directions of the zero-magnetic device, i.e., the horizontal direction, the direction perpendicular to the paper, and the vertical direction; the three axes of the geomagnetic coordinate system X-axis. g Y g and Z gThe direction of the magnetic field is unaffected by the triaxial orthogonal coil and fluxgate sensor, and can be considered fixed in this embodiment. The triaxial orthogonal coil is closely attached to the inner wall of the shielding device 1, and its shape and size correspond to the six inner surfaces of the shielding device 1. Under ideal conditions, the magnetic field generated by the triaxial orthogonal coil is perpendicular to the plane where the coil is located, and at this time, the magnetic field generated by the triaxial orthogonal coil coincides with the geomagnetic coordinate system. However, in reality, there will be installation errors in the triaxial orthogonal coil, and the magnetic field generated by the triaxial orthogonal coil will deviate, resulting in the uniform magnetic field coordinate system OX being affected. o Y o Z o With the geomagnetic field coordinate system OX g Y g Z g There is also a deviation angle between them, but the deviation angle is small.

[0074] In this step, the fluxgate sensor is positioned at the center position 5 of the zero-magnetic device, such that the coordinate system OX of the fluxgate sensor is... f Y f Z f and the geomagnetic coordinate system OX g Y g Z g The coordinate axes coincide; thus, in the subsequent calibration of the uniform magnetic field coordinate system, only the coordinate axis positions of the fluxgate sensor need to be finely adjusted to find the coordinate axis directions corresponding to the uniform magnetic field coordinate system.

[0075] It is understood that the present disclosure does not limit the method of setting the fluxgate sensor. All methods known to those skilled in the art can be used to fix the fluxgate sensor at the center of the zero-magnetic device, such as fixing the fluxgate sensor at the center of the zero-magnetic device by a three-axis non-magnetic turntable or a boom.

[0076] In some embodiments, such as Figure 6 As shown, Figure 5 The diagram shows a refined flowchart of step S211 in the calibration method for the error parameters of the triaxial orthogonal coil. (Refer to...) Figure 6 S211 "Place the calibrated fluxgate sensor at the center of the zero-magnetic device" includes:

[0077] S3111. Fix the preheated fluxgate sensor onto the three-axis non-magnetic turntable inside the zero-magnetic device.

[0078] The fluxgate sensor needs to be preheated before use, and the preheating time should meet the time specified in the instruction manual; for example, the preset time is 60 minutes.

[0079] Specifically, the fluxgate sensor is mounted on the sensor adapter, which is fixed to the three-axis non-magnetic turntable. The three-axis non-magnetic turntable is set at the center of the zero-magnetic device. At this time, the fluxgate sensor is roughly located at the center of the zero-magnetic device, resulting in low accuracy.

[0080] S3112. By adjusting the three-axis non-magnetic turntable, the fluxgate sensor is positioned at the center of the zero-magnetic device, and the coordinate system of the fluxgate sensor coincides with the geomagnetic coordinate system.

[0081] Specifically, the three-axis non-magnetic turntable is finely adjusted using the level on the sensor adapter to precisely fix the fluxgate sensor at the center of the zero-magnetic device, and the three-axis angle of the fluxgate sensor is adjusted to coincide with the geomagnetic coordinate system.

[0082] S212. Adjust the fourth coordinate axis Z of the fluxgate sensor. f The position of the fourth coordinate axis Z f Align the location with the direction of the largest change in magnetic field to determine the fourth coordinate axis Z of the fluxgate sensor. f The direction is the first coordinate axis Z of the uniform magnetic field coordinate system. o direction.

[0083] Specifically, based on the estimated coil constant k′ of the first axis coil zc A calibration current I′ of fixed amplitude is passed through the first axis coil of the triaxial orthogonal coil. z The magnetic field strength generated by the coil in the corresponding direction is approximately B. z_cali (B z_cali =k′ zc ×I′ z Manually fine-tune the fourth coordinate axis Z of the fluxgate sensor. f The position of the fluxgate sensor makes the fourth coordinate axis Z... f When the direction is aligned with the direction of the largest change in magnetic field, the fourth coordinate axis Z of the fluxgate sensor is at this point. f The first coordinate axis Z of the uniform magnetic field coordinate system o Coincidence, the fourth coordinate axis Z of the fluxgate sensor f The direction in which it is located is the first coordinate axis Z of the uniform magnetic field coordinate system. o direction.

[0084] S213. Adjust the fifth coordinate axis Y of the fluxgate sensor. f The position of the fluxgate sensor is maintained on the fourth coordinate axis Z during the adjustment process. f With the position fixed, make the fifth coordinate axis Y f Align the location with the direction of the largest change in magnetic field to determine the fifth coordinate axis Y of the fluxgate sensor. f The direction is the second coordinate axis Y of the uniform magnetic field coordinate system.o direction.

[0085] Specifically, based on the estimated coil constant k′ of the second axis coil yc A calibration current I′ of fixed amplitude is passed through the second axis coil of the triaxial orthogonal coil. y The magnetic field strength generated by the coil in the corresponding direction is approximately B. y_cali (B y_cali =k′ yc ×I′ y Manually fine-tune the fifth coordinate axis Y of the fluxgate sensor. f The position is maintained along the fourth coordinate axis Z during fine-tuning. f The position remains fixed, and the fluxgate sensor is positioned along the fourth coordinate axis Z. f Rotation causes the fifth coordinate axis Y of the fluxgate sensor to shift. f The direction it is aligned with is the direction of the largest change in magnetic field value. At this time, the fifth coordinate axis Y of the fluxgate sensor is... f The second coordinate axis Y of the uniform magnetic field coordinate system o Coincidence, the fifth coordinate axis Y of the fluxgate sensor f The direction in which it is located is the second coordinate axis Y of the uniform magnetic field coordinate system. o direction.

[0086] S214. Determine the sixth coordinate axis X of the fluxgate sensor. f The direction of the coordinate system is the third coordinate axis X of the uniform magnetic field coordinate system. o direction.

[0087] Specifically, both the fluxgate sensor coordinate system and the uniform magnetic field coordinate system are orthogonal coordinate systems. In the case where the two coordinate axes completely coincide, the sixth coordinate axis X of the fluxgate sensor... f The third coordinate axis X of the uniform magnetic field coordinate system o They also coincide, the sixth coordinate axis X of the fluxgate sensor f The direction it points to is the third coordinate axis X of the uniform magnetic field. o direction.

[0088] Thus, the calibrated uniform magnetic field coordinate system OX o Y o Z o Coordinate system OX of fluxgate sensor f Y f Z f Coincidence, the directions of the three coordinate axes of the fluxgate sensor (X) f Y f and Z f The coordinate axes (X) represent the directions of a uniform magnetic field. o Y o and Z o).

[0089] like Figure 7 The diagram shown illustrates the spatial positions of the geomagnetic coordinate system and the calibrated uniform magnetic field coordinate system (i.e., the fluxgate sensor coordinate system) provided in this embodiment of the present disclosure. (Refer to...) Figure 7 Geomagnetic coordinate system OX g Y g Z g With the calibrated uniform magnetic field coordinate system OX o Y o Z o (i.e., the fluxgate sensor coordinate system OX) f Y f Z f There is a deviation angle between them.

[0090] In some embodiments, such as Figure 8 As shown, Figure 4 A detailed flowchart of S120 in the calibration method for the error parameters of the triaxial orthogonal coil is shown. Figure 9 This is a schematic diagram illustrating the spatial position of the fluxgate sensor coordinate system and the three-axis orthogonal coil coordinate system provided in an embodiment of this disclosure. (Refer to...) Figure 8-9 S120 "Based on the calibrated uniform magnetic field coordinate system, the direction of magnetic field generation of the triaxial orthogonal coil is calibrated" includes:

[0091] S421. Determine the direction Z of the first magnetic field generated by the triaxial orthogonal coil. c It coincides with the direction of the first coordinate axis.

[0092] Specifically, the direction Z of the first magnetic field generated by the first axis coil in the triaxial orthogonal coil is defined. c The first coordinate axis Z of the uniform magnetic field o The directions coincide; the uniform magnetic field coordinate system is calibrated by a fluxgate sensor, and the calibrated uniform magnetic field coordinate system coincides with the fluxgate sensor coordinate system; thus, the first magnetic field is generated in the direction Z. c The fourth coordinate axis Z of the fluxgate sensor coordinate system f The directions they are in coincidence.

[0093] S422. Determine the direction Y of the second magnetic field generated by the triaxial orthogonal coil. c Located on the plane formed by the first and second coordinate axes, the second magnetic field is generated in the Y direction. c The angle between the first deviation angle and the direction of the second coordinate axis is the first deviation angle α. c .

[0094] Specifically, the direction Y of the second magnetic field generated by the second axis coil in the triaxial orthogonal coil is defined. c The second coordinate axis Y of the uniform magnetic field oBoth are located on the plane passing through the first coordinate axis Z0, and the direction of the second magnetic field is Y. c With the second coordinate axis Y o The included angle is the first deviation angle α c Similarly, the second magnetic field is generated in the direction Y. c The fifth coordinate axis Y of the fluxgate sensor coordinate system f The angle between the directions is also α. c .

[0095] S423. Determine the direction X of the third magnetic field generated by the triaxial orthogonal coil. c The angle between the plane formed by the directions of the second and third coordinate axes is the second deviation angle β. c The angle between the direction of the third magnetic field and the plane formed by the directions of the first and third coordinate axes is the third deviation angle γ. c .

[0096] Specifically, the direction X of the third magnetic field generated by the third axis coil in a triaxial orthogonal coil is defined. c Its coordinates with the second coordinate axis Y of the uniform magnetic field o and the third coordinate axis X o The angle between the planes is the second deviation angle β. c Its relationship with the first coordinate axis Z o and the third coordinate axis X o The angle between the planes is the third deviation angle γ. c Similarly, the direction of the third magnetic field is X. c The fifth coordinate axis Y of the fluxgate sensor coordinate system f and the sixth coordinate axis X f The plane in which it is located (i.e., X) f Y f The angle between the planes is β c The fourth coordinate axis Z of the fluxgate sensor f and the sixth coordinate axis X f The plane in which it is located (i.e., X) f Z f The angle between the planes is γ c .

[0097] In some embodiments, such as Figure 10 As shown, Figure 4 The diagram shows a refined flowchart of step S130 in the calibration method for the error parameters of the triaxial orthogonal coil. (Refer to...) Figure 10 S130 "Establishing an orthogonal error model for a triaxial orthogonal coil and calibrating the error parameters in the orthogonal error model" includes:

[0098] S531. Establish an orthogonal error model for a three-axis orthogonal coil and determine the error parameters to be calibrated.

[0099] Specifically, such as Figure 11 As shown, this step can be broken down as follows:

[0100] S6311. Obtain the remanence b of the fluxgate sensor along its three axes in the calibrated uniform magnetic field coordinate system. xf0 b yf0 and b zf0 .

[0101] S6312. Based on the remanence, establish an orthogonal error model.

[0102] Specifically, based on the remanence, the formula for determining the orthogonal error model is as follows:

[0103] B xf =k xc I x cosβ c cosγ c +b xf0

[0104] B yf =k xc I x cosβ c sinγ c +k yc I y cosα c +b yf0

[0105] B zf =k xc I x sinβ c +k yc I y sinα c +k zc I z +b zf0 ;

[0106] Among them, I x I y and I z B represents the current value on a triaxial orthogonal coil. xf B yf and B zf This represents the magnetic field strength generated by the triaxial orthogonal coil as measured by the fluxgate sensor; k xc k yc and k ac α represents the proportionality coefficient between the current in each axis coil and the actual magnetic field strength generated; c Corresponding to the first deviation angle, β c Corresponding to the second deviation angle; γ c Corresponds to the third deviation angle.

[0107] The remanence of the three axes measured by the fluxgate sensor (b) xf0 b yf0 and b zf0 The zero bias value b of the triaxial orthogonal coil to be calibrated xc0 b yc0 and b zc0 The relationship is:

[0108] b xf0 =b xc0 cosβ c cosγ c

[0109] b yf0 =b xc0 cosβ c sinγ c +b yc0 cosα c

[0110] b zf0 =b xc0 sinβ c +b yc0 sinα c +b zc0 ;

[0111] Therefore, based on the conversion relationship between remanence and zero bias, the formula for determining the orthogonal error model using the data fitting method is as follows:

[0112]

[0113] S6313. Determine the error parameters to be calibrated, including the coil constant k. xc k yc and k ac Non-orthogonal error angle α c β c and γ c and zero bias b xc0 b yc0 and b zc0 .

[0114] Where, k xc k yc and k zc α represents the proportionality coefficient between the current in each axis coil and the actual magnetic field strength generated; c Corresponding to the first deviation angle, β c Corresponding to the second deviation angle; γ c Corresponding to the third deviation angle; b xc0 b yc0 and b zc0This indicates the amount of residual magnetism of each shaft coil at the center position of the zero-magnetic device.

[0115] S532, use three independent high-precision DC power supplies to respectively supply a preset current I to the three-axis quadrature coil. x I y and I z Record the triaxial magnetic field strength B measured by the fluxgate sensor for each set of currents. xf B yf and B zf Among them, the preset current I x I y and I z The system needs to cover 8 quadrants in space, collect M sample data in each quadrant, and collect a total of N sample data, where M and N are positive integers and N is greater than or equal to the number of error parameters.

[0116] Specifically, three independent high-precision DC power supplies are used to supply a preset current I to the three-axis orthogonal coils. x I y and I z A specific magnetic field is generated at the center of the zero-magnetic device, and the reading of the fluxgate sensor is the corresponding magnetic field strength. The preset current and the triaxial magnetic field strength acquired in this step are used as the dataset for calibrating the error parameters of the triaxial orthogonal coil. Since there are nine error parameters to be calibrated, the number of samples in the dataset should be greater than or equal to nine. Theoretically, the more samples in the dataset, the more accurate the calibration values ​​of the error parameters. However, to save calibration costs, selecting an appropriate number of samples can effectively improve calibration efficiency while maintaining the accuracy of the calibration values. For example, based on simulation calculations and confidence requirements, 24 samples in a uniform magnetic field space are selected as the dataset for parameter calibration.

[0117] Optionally, three independent high-precision DC power supplies are used to supply a preset current I to the three-axis orthogonal coils. x I y and I z Previously, it was also necessary to set the preset current I. x I y and I z The amplitude is designed based on the estimated coil constant k of the triaxial orthogonal coil. xc k yc and k zc Determine the preset current I x I y and I z The amplitude of the preset current I x I y and I z The magnitude of the generated triaxial vector magnetic field. Equal to the preset amplitude, that is This ensures that the current passing through the coil is within the allowable range; where R represents the preset amplitude, which is a constant.

[0118] It is understandable that the range of the preset amplitude R can be flexibly set according to the specific requirements of the calibration method for the error parameters of the triaxial orthogonal coil. For example, R can be set to... This is not limited to this.

[0119] Optionally, the calibration method further includes: setting a preset current I. x I y and I z The angle between the direction of the generated triaxial vector magnetic field and the direction of the magnetic field generated by the triaxial orthogonal coil is greater than the preset angle.

[0120] Among them, the preset current I x I y and I z The generated triaxial vector magnetic field needs to be oriented across all eight quadrants of space. The direction of the triaxial vector magnetic field can be chosen randomly in space, but to avoid generating singular values ​​during the solution process, the angle between the direction of the triaxial vector magnetic field and the coordinate axes of the triaxial orthogonal coil is greater than a preset angle. For example, the preset angle is set to 10°.

[0121] S533. Substitute the preset current and the corresponding triaxial magnetic field strength into the orthogonal error model to solve for the calibration value of the error parameter.

[0122] To simplify the calculation, the orthogonal error model formula determined in S531 can be rewritten as follows:

[0123]

[0124] in,

[0125] Representing the above multivariate equations using matrices is more convenient. The matrix expression for the orthogonal error model is as follows:

[0126] B = I T A;

[0127] in, A=[a1, a2, a3, a4, a5, a6, α7, a8, a9] T ,

[0128] Since the output signal of the fluxgate sensor contains noise, its noise ε is added to the orthogonal error model, expressed by the following formula:

[0129] B = I T A+ε;

[0130] Estimating the error vector using the least squares method To obtain the optimal parameters Construct the minimization function:

[0131]

[0132] S(A) can be expressed as:

[0133] S(A)=B′BA′I′BB′IA+A′I′IA=B′B-2A′I′B+A′I′IA;

[0134] Since A′I′B is a 1×1 matrix, i.e., a scalar, and its inverse matrix (A′I′B)... -1 =B′IA are the same scalar, and the least squares estimator must satisfy:

[0135]

[0136] The above formula is reduced to a least-squares normal equation, and its least-squares estimator is:

[0137]

[0138] Having obtained the value of matrix A, the nine error parameters of the triaxial orthogonal coil, namely the coil constant k, can be calculated according to the orthogonal error model formula determined in S531. xc k yc and k zc Non-orthogonal error angle α c β c and γ c and zero bias b xc0 b yc0 and b zc0 .

[0139] This disclosure also provides a triaxial orthogonal coil. Calibration using any of the above-described triaxial orthogonal coil error parameter calibration methods has corresponding beneficial effects, which will not be repeated here to avoid repetition.

[0140] Among them, the triaxial orthogonal coil can be set as any triaxial ideal orthogonal coil used for magnetic field shielding.

[0141] In some embodiments, the triaxial orthogonal coil is a triaxial momentless uniform magnetic field coil.

[0142] Among them, the torque-free coil The magnetic moment is zero. Through A certain number of coil turns for each axis coil andA specific current direction causes the magnetic field outside the coil to decay rapidly; during operation, it will not cause magnetic interference to the environment beyond a preset distance, and it will not magnetize nearby magnetic materials, thus avoiding additional errors. In this way, the coupling relationship between the magnetic field generated by the torque-free coil and the magnetic field of the shielding material is greatly weakened, resulting in a more accurate standard magnetic source.

[0143] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0144] The above description is merely a specific embodiment of this disclosure, enabling those skilled in the art to understand or implement it. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for calibrating three-axis orthogonal coil error parameters, characterized in that, The three-axis orthogonal coil is arranged in the interior of the zero magnetic device and closely adheres to the inner wall of the zero magnetic device. The uniform magnetic field coordinate system distributed in the zero magnetic device is calibrated, and the uniform magnetic field coordinate system comprises a first coordinate axis, a second coordinate axis and a third coordinate axis. The magnetic field generation direction of the three-axis orthogonal coil is calibrated based on the calibrated uniform magnetic field coordinate system. The magnetic field generation direction of the three-axis orthogonal coil is calibrated based on the calibrated uniform magnetic field coordinate system. The first magnetic field generation direction of the three-axis orthogonal coil is determined to coincide with the direction of the first coordinate axis. The second magnetic field generation direction of the three-axis orthogonal coil is determined to be located on the plane formed by the first coordinate axis direction and the second coordinate axis direction, and the included angle between the second magnetic field generation direction and the second coordinate axis direction is a first deviation angle. The third magnetic field generation direction of the three-axis orthogonal coil is determined to have a second deviation angle with the plane formed by the second coordinate axis direction and the third coordinate axis direction, and a third deviation angle with the plane formed by the first coordinate axis direction and the third coordinate axis direction. An orthogonal error model of the three-axis orthogonal coil is established, and error parameters in the orthogonal error model are calibrated, wherein the error parameters include coil constants 、 and non-orthogonal error angles 、 and and zero offset values 、 and wherein, 、 and represent proportional coefficients of magnetic field intensity generated by each-axis coil and current; corresponds to the first deviation angle, corresponds to the second deviation angle; corresponds to the third deviation angle; 、 and represent residual magnetic quantities of each-axis coil at a center position of a zero magnetic device, and the residual magnetic quantities are used to determine the orthogonal error model.

2. The calibration method of claim 1, wherein The uniform magnetic field coordinate system distributed in the zero magnetic device is calibrated, and the uniform magnetic field coordinate system comprises a first coordinate axis, a second coordinate axis and a third coordinate axis. The calibrated fluxgate sensor is placed at the center position of the zero magnetic device. The fourth coordinate axis of the fluxgate sensor is adjusted so that the direction of the fourth coordinate axis is aligned with the direction of the maximum magnetic field change value, and the direction of the fourth coordinate axis of the fluxgate sensor is determined as the first coordinate axis direction of the uniform magnetic field coordinate system. The fifth coordinate axis of the fluxgate sensor is adjusted while keeping the position of the fourth coordinate axis of the fluxgate sensor unchanged, so that the direction of the fifth coordinate axis is aligned with the direction of the maximum magnetic field change value, and the direction of the fifth coordinate axis of the fluxgate sensor is determined as the second coordinate axis direction of the uniform magnetic field coordinate system. The sixth coordinate axis of the fluxgate sensor is determined as the third coordinate axis direction of the uniform magnetic field coordinate system.

3. The calibration method of claim 1, wherein The orthogonal error model of the three-axis orthogonal coil is established, and the error parameters to be calibrated are determined. The orthogonal error model of the three-axis orthogonal coil is established, and the error parameters to be calibrated are determined. Three independent high-precision direct current power supplies are used to supply preset currents to the three-axis orthogonal coils 、 and , and the three-axis magnetic field strengths measured by the fluxgate sensors corresponding to each group of currents are recorded 、 and ; wherein the preset currents 、 and need to cover 8 quadrants in space, M sample data are collected in each quadrant, a total of N sample data are collected, M and N are positive integers and N is greater than or equal to the number of error parameters; The orthogonal error model of the three-axis orthogonal coil is established, and the error parameters to be calibrated are determined.

4. The calibration method of claim 3, wherein Before the three orthogonal coils are respectively given preset currents by three independent high-precision direct-current power supplies 、 and , further comprising: According to the estimated coil constant of the three-axis orthogonal coil , and , the amplitudes of the preset currents , and are determined. wherein the preset current , and the amplitude of the three-axis vector magnetic field generated by the three-axis vector magnetic field generator is equal to the preset amplitude.

5. The calibration method of claim 3, wherein The orthogonal error model is established based on the residual magnetic quantity. Obtaining the residual magnetization of the three axes of the fluxgate sensor in the uniform magnetic field coordinate system after calibration 、 and ; The orthogonal error model is established based on the residual magnetic quantity. determining error parameters to be calibrated including coil constants 、 and non-orthogonal error angles 、 and and bias values 、 and .

6. The calibration method of claim 5, wherein, The orthogonal error model is established based on the residual magnetic quantity. The formula of the orthogonal error model is determined based on the conversion relationship between the residual magnetic quantity and the zero offset value. ； The formula of the orthogonal error model is determined by using a data fitting method based on the conversion relationship between the residual magnetic quantity and the zero offset value.

7. The calibration method of claim 2, wherein, The calibrated fluxgate sensor is placed at the center position of the zero magnetic device. The preheated fluxgate sensor is fixed on the three-axis non-magnetic turntable in the zero magnetic device; The three-axis non-magnetic turntable is adjusted, so that the fluxgate sensor is located at the center position of the zero magnetic device, and the coordinate system of the fluxgate sensor coincides with the geomagnetic coordinate system.

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