Magnetic north pole measurement three-dimensional compass with split design

Abstract

The invention provides a split type magnetic north pole measurement three-dimensional compass, which comprises a first installation reference surface, an acceleration acquisition operation circuit board, a double-end terminal wire, a second installation reference surface and a magnetic probe circuit board, the acceleration acquisition operation circuit board is arranged on the first installation reference surface, and the double-end terminal wire is arranged on the second installation reference surface. The magnetic probe circuit board is arranged on the second installation reference surface, and the acceleration acquisition operation circuit board is connected to the magnetic probe circuit board through the double-end terminal wire; the space calibration process of the magnetic probe circuit board comprises the following steps: S1, constructing an ellipsoid equation; s2, acquiring a coefficient matrix corresponding to the ellipsoid equation; s3, calculating the center offset of the ellipsoid as a fixed zero point of magnetic field interference; and S4, obtaining a characteristic value after matrix decomposition according to a fixed zero point, and calculating a scale coefficient matrix. The measuring precision of the product can be improved, and the limitation of the product to the installation environment is reduced.

Description

Technical Field

[0001] The invention relates to a three-dimensional electronic compass, in particular to a three-dimensional compass for measuring magnetic north pole with a split design. Background Art

[0002] The three-dimensional electronic compass is also called the three-dimensional digital compass, or three-dimensional compass for short. It is usually composed of a three-axis accelerometer and a three-axis magnetometer with an integrated design. Among them, the accelerometer can measure the specific force of the carrier, which is defined as the non-gravitational external force per unit mass; the magnetometer can measure the magnetic field intensity sensitive to the carrier coordinate system. The three-dimensional compass is installed as a navigation instrument or attitude sensor, and can be applied to the fields of marine navigation and mapping, GPS integrated navigation, antenna servo control, infrared imager, laser rangefinder, map plotter, underwater robot navigation, oceanographic survey instrument, and special occasion robot. In the actual application environment of the three-dimensional compass, the earth's magnetic field is a natural reference field. The direction of the magnetic field points from the geographic South Pole to the geographic North Pole, and its intensity is about 0.5 to 0.6 Gauss, that is, the earth's magnetic field is a relatively weak magnetic field; the geomagnetic axis does not coincide with the earth's rotation axis, and there is an inclination angle of about 11.5° between them. This deviation is called magnetic declination, which is usually 1 to 5° in China, and can reach up to 11° at most. Therefore, it will bring certain errors to the actual measurement. On this basis, since the actual installation environment will inevitably have various interference sources, the existing three-dimensional compass will not be able to meet the actual anti-interference needs well, and there are also problems such as large limitations on the installation environment, which is not conducive to the promotion and application of the product. Therefore, in order to effectively improve the measurement accuracy of the product and reduce the limitations of the product on the installation environment, how to optimize the structure and spatial calibration process of the three-dimensional compass is undoubtedly a technical problem that must be solved for measuring the magnetic north pole through a three-dimensional compass. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a split-design three-dimensional compass for measuring the magnetic north pole, aiming to improve the measurement accuracy of the product and reduce the limitations of the product on the installation environment by optimizing the structure and spatial calibration process of the three-dimensional compass.

[0004] To this end, the present invention provides a split-design magnetic north pole measurement three-dimensional compass, comprising: a first mounting reference surface, an acceleration acquisition operation circuit board, a double-headed terminal line, a second mounting reference surface and a magnetic probe circuit board, wherein the acceleration acquisition operation circuit board is arranged on the first mounting reference surface, the magnetic probe circuit board is arranged on the second mounting reference surface, and the acceleration acquisition operation circuit board is connected to the magnetic probe circuit board through the double-headed terminal line; wherein the spatial calibration process of the magnetic probe circuit board comprises the following steps:

[0005] Step S1, constructing an ellipsoid equation for the magnetic field model of the magnetic probe circuit board;

[0006] Step S2, obtaining a coefficient matrix corresponding to the ellipsoid equation according to the sampling point data of the calibration position;

[0007] Step S3, calculating the ellipsoid center offset according to the coefficients of the ellipsoid equation, and using the ellipsoid center offset as the fixed zero point of the magnetic field interference of the magnetic probe circuit board;

[0008] Step S4, obtaining the eigenvalues ​​of the decomposed matrix according to the fixed zero point of the magnetic field interference, and calculating the scale coefficient matrix of the magnetic probe circuit board according to the eigenvalues.

[0009] A further improvement of the present invention is that in step S1, the formula Ax 2 +By 2 +Cz 2 +2Dxy+2Exz+2Fyz+2Gx+2Hy+2Iz=1 constructs an ellipsoid equation for the magnetic field model of the magnetic probe circuit board, wherein A, B, C, D, E, F, G, H and I respectively represent nine coefficients of the ellipsoid equation, and x, y and z represent the coordinates of the three-axis magnetometer in the magnetic probe circuit board.

[0010] A further improvement of the present invention is that step S2 includes the following sub-steps:

[0011] Step S201, by formula Hk=[x 2 ,y 2 ,z 2 ,2xy,2xz,2yz,2x,2y,2z] 12×9 Calculate the matrix Hk, where Hk represents a 12×9 matrix;

[0012] Step S202, by formula Xk=(Hk T *Hk) T *Hk T *Yk calculates the coefficient matrix Xk, where Xk represents a 9×1 coefficient matrix corresponding to the nine coefficients A, B, C, D, E, F, G, H, and I; the superscript T represents a transposed matrix; Yk represents a 12×1 first-order matrix, which is used to represent the sampling point data of the twelve calibration positions.

[0013] A further improvement of the present invention is that in step S202, the sampling of the twelve calibration positions includes:

[0014] The first calibration position is horizontal placement and static sampling in any direction;

[0015] The second calibration position is placed horizontally and rotated 90° clockwise relative to the first calibration position before static sampling;

[0016] The third calibration position is placed horizontally and rotated 90° clockwise relative to the second calibration position before static sampling;

[0017] The fourth calibration position is placed horizontally and rotated 90° clockwise relative to the third calibration position before static sampling;

[0018] The fifth calibration position is rotated 30° clockwise relative to the fourth calibration position, and the pitch angle is adjusted to 45°±10°, and static sampling is performed;

[0019] The sixth calibration position, maintaining the pitch angle of the fifth calibration position, rotates 90° clockwise relative to the fifth calibration position, and then performs static sampling;

[0020] At the seventh calibration position, the pitch angle of the sixth calibration position is maintained, and after rotating 90° clockwise relative to the sixth calibration position, static sampling is performed;

[0021] The eighth calibration position, maintaining the pitch angle of the seventh calibration position, rotates 90° clockwise relative to the seventh calibration position, and then performs static sampling;

[0022] The ninth calibration position is rotated 30° clockwise relative to the eighth calibration position, and then the pitch angle is adjusted to -45°±10°, and static sampling is performed;

[0023] At the tenth calibration position, the pitch angle of the ninth calibration position is maintained, and after rotating 90° clockwise relative to the ninth calibration position, static sampling is performed;

[0024] At the eleventh calibration position, the pitch angle of the tenth calibration position is maintained, and after rotating 90° clockwise relative to the tenth calibration position, static sampling is performed;

[0025] At the twelfth calibration position, the pitch angle of the eleventh calibration position is maintained, and after rotating 90° clockwise relative to the eleventh calibration position, static sampling is performed.

[0026] A further improvement of the present invention is that the sampling point adjustment process of the twelve calibration positions is realized by a tripod turntable and a dividing plate, and the magnetic probe circuit board is arranged on the tripod turntable through the dividing plate; during the rotation of the angle, the angle error is controlled within 5 to 10°.

[0027] A further improvement of the present invention is that the step S3 is performed by formula The coefficients of the ellipsoid equation are calculated to calculate the ellipsoid center offset Center, and the ellipsoid center offset Center is used as the fixed zero point of the magnetic field interference of the magnetic probe circuit board.

[0028] A further improvement of the present invention is that step S4 includes the following sub-steps:

[0029] Step S401, by formula Obtain the eigenvalue Mat_r after the decomposition matrix, where Center(1:3) represents the first to third vector elements in the ellipsoid center offset Center, and 1:3 represents sequence numbers 1 to 3;

[0030] Step S402, by formula Calculate the ellipsoid axis length Radii of the magnetic field model, where RD represents a diagonal matrix composed of eigenvalues ​​Mat_r, RD(i) represents an eigenvalue element, and i is a natural number from 1 to 3;

[0031] Step S403, taking the minimum axis length min_Radii of the ellipsoid axis length Radii by the formula min_Radii=min(Radii);

[0032] Step S404, by formula The minimum axis length min_Radii is normalized to obtain the normalized scale coefficient Scale, where Radii(i) represents the axis length of the ellipsoid;

[0033] Step S405, by formula mat_Correct = RV*Scale*RV T The scale coefficient matrix mat_Correct of the magnetic probe circuit board is calculated, and RV represents a matrix composed of eigenvectors corresponding to eigenvalues ​​Mat_r.

[0034] A further improvement of the present invention is that the distance between the installation position of the second installation reference surface and the magnetic medium object is controlled to be more than 40 cm, and the magnetic medium object includes any one or more of iron, magnet and engine.

[0035] A further improvement of the present invention is that when the distance between the installation position of the second installation reference plane and the magnetic medium object is less than 40 cm, after fixing the second installation reference plane and the magnetic medium object, the magnetic probe circuit board and the magnetic medium object are controlled to perform synchronous rotation calibration.

[0036] A further improvement of the present invention is that the installation angles of the acceleration acquisition and calculation circuit board and the magnetic probe circuit board are defined as: the azimuth angle refers to the X-axis direction, the measurement range is 0°~360°, it is 0° when pointing to the magnetic north, and clockwise rotation is positive; the pitch angle refers to the Y-axis direction, the measurement range is -90°~90°, it is 0° when horizontal, looking up is positive, and looking down is negative; the roll angle refers to the Z-axis direction, the measurement range is -180°~180°, it is 0° when horizontal, right tilt is positive, and left tilt is negative.

[0037] Compared with the prior art, the beneficial effects of the present invention are: a split design between the acceleration acquisition and operation circuit board and the magnetic probe circuit board is realized through the first installation reference surface, the second installation reference surface and the double-headed terminal line, and an optimized spatial calibration process of the magnetic probe circuit board is provided, thereby not only making the size of the magnetic probe circuit board smaller, but also facilitating installation in any space with a good magnetic field environment to collect magnetic data, while the acceleration acquisition and operation circuit board can be installed in a space in any environment, thereby effectively reducing the limitations on the installation environment, and, through the optimized spatial calibration process, providing a good foundation for improving the measurement accuracy of the product, facilitating the promotion and application of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a structural schematic diagram of an embodiment of the present invention;

[0039] Figure 2 is a schematic diagram of a spatial calibration process of a magnetic probe circuit board according to an embodiment of the present invention;

[0040] Figure 3 is a schematic diagram of sampling placement of twelve calibration positions in one embodiment of the present invention;

[0041] Figure 4 It is a schematic diagram of installation angle definition of an embodiment of the present invention. DETAILED DESCRIPTION

[0042] In the description of the present invention, if it involves a description of orientation, for example, the orientation or position relationship indicated by "upper", "lower", "front", "back", "left", "right", etc. is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. If a certain technical feature is referred to as "set", "fixed", "connected", or "installed" on another technical feature, it can be directly set, fixed, or connected to the other technical feature, or it can be indirectly set, fixed, connected, or installed on the other technical feature.

[0043] In the description of the present invention, if "several" is involved, it means more than one; if "multiple" is involved, it means more than two; if "greater than", "less than", or "exceed" is involved, it should be understood as not including the number itself; if "above", "below", or "within" is involved, it should be understood as including the number itself. If "first", "second", etc. are involved, they should be understood as being used only to distinguish the names of the same or similar technical features, and should not be understood as implying / indicating the relative importance of the technical features, the number of the technical features, or the order of the technical features.

[0044] The preferred embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings.

[0045] like Figures 1 to 4 As shown, this embodiment provides a split-type magnetic north pole measurement three-dimensional compass, including: a first mounting reference surface 1, an acceleration acquisition operation circuit board 3, a double-headed terminal line 5, a second mounting reference surface 7 and a magnetic probe circuit board 9, wherein the acceleration acquisition operation circuit board 3 is arranged on the first mounting reference surface 1, the magnetic probe circuit board 9 is arranged on the second mounting reference surface 7, and the acceleration acquisition operation circuit board 3 is connected to the magnetic probe circuit board 9 through the double-headed terminal line 5; wherein the spatial calibration process of the magnetic probe circuit board 9 includes the following steps:

[0046] Step S1, constructing an ellipsoid equation for the magnetic field model of the magnetic probe circuit board 9;

[0047] Step S2, obtaining a coefficient matrix corresponding to the ellipsoid equation according to the sampling point data of the calibration position;

[0048] Step S3, calculating the ellipsoid center offset according to the coefficients of the ellipsoid equation, and using the ellipsoid center offset as the fixed zero point of the magnetic field interference of the magnetic probe circuit board 9;

[0049] Step S4, obtaining the eigenvalues ​​of the decomposed matrix according to the fixed zero point of the magnetic field interference, and calculating the scale coefficient matrix of the magnetic probe circuit board 9 according to the eigenvalues.

[0050] like Figure 1As shown, in this embodiment, the first mounting reference surface 1 is preferably provided with a mounting hole 2, and the first mounting reference surface 1 is installed and fixed through the mounting hole 2 and the first brass screw 4. The acceleration acquisition and operation circuit board 3 refers to the main circuit board for realizing acceleration acquisition and operation, and preferably adopts an HCM603 circuit board; the double-headed terminal wire 5 preferably adopts an NH1.0-6PIN double-headed terminal wire; the second mounting reference surface 7 is preferably provided with a mounting hole 6, and the second mounting reference surface 7 is installed and fixed through the mounting hole 6 and the second brass screw 8. In order to ensure the measurement accuracy of the product, the first brass screw 4 and the second brass screw 8 are preferably M2 non-magnetic screws, such as M2 brass screws, during installation; the magnetic probe circuit board 9 refers to a magnetometer circuit board for realizing magnetic detection and calibration, and preferably adopts an HM65 circuit board.

[0051] The magnetic north pole measurement three-dimensional compass provided in this embodiment refers to a high-precision three-dimensional electronic compass for separate measurement. In order to solve the problem of uncertain magnetic field interference in the user equipment environment, a technical solution is adopted in which a magnetic probe circuit board 9 (referred to as the magnetic probe) and an acceleration acquisition and operation circuit board 3 (referred to as the acquisition operation circuit or acquisition board) are separated. The two modules of the magnetic probe circuit board 9 and the acceleration acquisition and operation circuit board 3 are connected and transmitted signals through a double-headed terminal line 5 and its cable connection. Since the magnetic probe circuit board 9 (referred to as the magnetic probe) is small in size, it can be conveniently installed in any space with a good magnetic field environment to collect magnetic data; and the acceleration acquisition and operation circuit board 3 (referred to as the acquisition operation circuit or acquisition board) can be installed in any environmental space.

[0052] The magnetic probe circuit board 9 described in this embodiment adopts a hardware circuit board (also called hard magnetism) and software spatial calibration (also called soft magnetism calibration algorithm), so that the product can eliminate the influence of the magnetic field through the matching spatial calibration process in an environment with magnetic field interference. This embodiment integrates three-axis magnetic induction technology, calculates the heading in real time through the central processing unit, and uses a three-axis accelerometer to compensate for the tilt angle in a wide range, ensuring that the compass can provide high-precision heading data even when the tilt angle is as high as ±85°. This embodiment integrates high-precision MCU control and diversified output methods. The standard interface includes RS232 / RS485 / TTL and other interfaces, and other communication interfaces can be customized.

[0053] In addition, this embodiment also has the characteristics of small size and low power consumption, and can be applied in many fields such as antenna stabilization, vehicle and system integration. It has high shock resistance and high reliability, so that the three-dimensional compass can work normally in extremely harsh environments, and is more suitable for today's various high-precision measurement integrated control systems.

[0054] It should be noted that this embodiment is not intended to compensate for and change the magnetic interference of the installation environment, but to optimize the design of the structure and spatial calibration process of the three-dimensional compass, so as to calculate a moderate deviation in a stable magnetic environment, thereby providing an accurate data basis for deviation compensation.

[0055] More specifically, in step S1 of this embodiment, the formula Ax 2 +By 2 +Cz 2 +2Dxy+2Exz+2Fyz+2Gx+2Hy+2Iz=1 constructs an ellipsoid equation for the magnetic field model of the magnetic probe circuit board 9, wherein A, B, C, D, E, F, G, H and I respectively represent nine polynomial coefficients of the ellipsoid equation, and x, y and z represent the three-dimensional coordinates of the three-axis magnetometer in the magnetic probe circuit board 9; the ellipsoid equation model is a quadratic ternary polynomial structure, and A, B, C, D, E, F, G, H and I are the polynomial coefficients of the ellipsoid equation.

[0056] In this embodiment, the data of the sampling points at the twelve calibration positions are preferably substituted into the formula Ax 2 +By 2 +Cz 2 +2Dxy+2Exz+2Fyz+2Gx+2Hy+2Iz=1 can be written into the form of a matrix equation: Yk=Hk*Xk, where Yk represents a 12×1 first-order sampling matrix, Xk represents a 9×1 ellipsoid coefficient matrix corresponding to nine coefficients A~I, and Hk represents a 12×9 ellipsoid sampling matrix.

[0057] Step S2 in this embodiment includes the following sub-steps:

[0058] Step S201, by formula Hk=[x 2 ,y 2 ,z 2 ,2xy,2xz,2yz,2x,2y,2z] 12×9 Calculate the matrix Hk, where Hk represents a 12×9 matrix;

[0059] Step S202, by formula Xk=(Hk T *Hk) T *Hk T *Yk calculates the coefficient matrix Xk, where Xk represents a 9×1 ellipsoid coefficient matrix corresponding to the nine coefficients A, B, C, D, E, F, G, H, and I; the superscript T represents a transposed matrix; Yk represents a 12×1 first-order matrix, which is used to represent the sampling point data of the twelve calibration positions.

[0060] In practical applications, the coefficients in the coefficient matrix Xk can be calculated using the least squares method. To ensure real-time performance, the recursive least squares method can also be used.

[0061] Specifically, Figure 3 As shown, in step S202 of this embodiment, the sampling of the twelve calibration positions includes:

[0062] The first calibration position, i.e. Figure 3 The top view position 1 shown is placed horizontally and sampled statically in any direction; at this time, the azimuth angle of the magnetic north pole measuring three-dimensional compass points to 0°, the pitch angle is 0°, and the roll angle is 0°;

[0063] The second calibration position, i.e. Figure 3 The top view position 2 shown is placed horizontally and is sampled statically after being rotated 90° clockwise relative to the first calibration position; at this time, the azimuth angle of the magnetic north pole measuring three-dimensional compass points to 90°, the pitch angle is 0°, and the roll angle is 0°;

[0064] The third calibration position, i.e. Figure 3 The top view position 3 shown is placed horizontally and is sampled statically after being rotated 90° clockwise relative to the second calibration position; at this time, the azimuth angle of the magnetic north pole measurement three-dimensional compass points to 180°, the pitch angle is 0°, and the roll angle is 0°;

[0065] The fourth calibration position, i.e. Figure 3 The top view position 4 shown is placed horizontally and is sampled statically after being rotated 90° clockwise relative to the third calibration position; at this time, the azimuth of the magnetic north pole measuring three-dimensional compass points to 270°, the pitch angle is 0°, and the roll angle is 0°;

[0066] The fifth calibration position, i.e. Figure 3 The top view position 5 shown is rotated 30° clockwise relative to the fourth calibration position, and the pitch angle is adjusted to 45°±10°, and static sampling is performed; at this time, the azimuth angle of the magnetic north pole measurement three-dimensional compass points to 30°, the pitch angle is 45°, and the roll angle is 0°;

[0067] The sixth calibration position, i.e. Figure 3 The top view position 6 shown maintains the pitch angle of the fifth calibration position, rotates 90° clockwise relative to the fifth calibration position, and then performs static sampling; at this time, the azimuth angle of the magnetic north pole measurement three-dimensional compass points to 120°, the pitch angle is 45°, and the roll angle is 0°;

[0068] The seventh calibration position, i.e. Figure 3The top view position 7 shown maintains the pitch angle of the sixth calibration position, rotates 90° clockwise relative to the sixth calibration position, and then performs static sampling; at this time, the azimuth angle of the magnetic north pole measurement three-dimensional compass points to 210°, the pitch angle is 45°, and the roll angle is 0°;

[0069] The eighth calibration position, i.e. Figure 3 The top view position 8 shown maintains the pitch angle of the seventh calibration position, rotates 90° clockwise relative to the seventh calibration position, and then performs static sampling; at this time, the azimuth of the magnetic north pole measurement three-dimensional compass points to 300°, the pitch angle is 45°, and the roll angle is 0°;

[0070] The ninth calibration position, i.e. Figure 3 The top view position 9 shown is rotated 30° clockwise relative to the eighth calibration position, and then the pitch angle is adjusted to -45°±10°, and static sampling is performed; at this time, the azimuth angle of the magnetic north pole measurement three-dimensional compass points to 60°, the pitch angle is -45°, and the roll angle is 0°;

[0071] The tenth calibration position, i.e. Figure 3 The top view position 10 shown maintains the pitch angle of the ninth calibration position, rotates 90° clockwise relative to the ninth calibration position, and then performs static sampling; at this time, the azimuth angle of the magnetic north pole measurement three-dimensional compass points to 150°, the pitch angle is -45°, and the roll angle is 0°;

[0072] The eleventh calibration position, i.e. Figure 3 The top view position 11 shown maintains the pitch angle of the tenth calibration position, rotates 90° clockwise relative to the tenth calibration position, and then performs static sampling; at this time, the azimuth angle of the magnetic north pole measurement three-dimensional compass points to 240°, the pitch angle is -45°, and the roll angle is 0°;

[0073] The twelfth calibration position, i.e. Figure 3 The top view position 12 shown maintains the pitch angle of the eleventh calibration position, rotates 90° clockwise relative to the eleventh calibration position, and then performs static sampling; at this time, the azimuth angle of the magnetic north pole measurement three-dimensional compass points to 330°, the pitch angle is -45°, and the roll angle is 0°.

[0074] It should be noted that the azimuth angle described above in this embodiment refers to a relative angle. For example, when placed in the first calibration position (i.e., position 1), the azimuth angle of the magnetic north pole measuring three-dimensional compass can point to any angle, such as 42°. When placed in the second calibration position (i.e., position 2), the azimuth angle of the magnetic north pole measuring three-dimensional compass can differ by 90°, that is, it is placed at about 132°, and the angle error is controlled within 5 to 10°, and so on. The pitch angle and roll angle refer to absolute angles, but when placed, the placement angle errors of the azimuth angle, pitch angle, and roll angle can be controlled within ±5°.

[0075] Therefore, in order to facilitate the operation, the sampling point adjustment process of the twelve calibration positions described in this embodiment is realized through a tripod turntable and a dividing plate, and the magnetic probe circuit board 9 is set on the tripod turntable through the dividing plate; during the rotation of the angle, the angle error is controlled within 5 to 10°.

[0076] In this embodiment, the azimuth angle, pitch angle and roll angle are defined as follows: Figure 4 As shown, the azimuth angle refers to the direction angle of the X-axis magnetic sensor, that is, Figure 4 The angle of the NOUTH axis in the measurement range is 0° to 360°. When pointing to the magnetic north, it is 0°, and clockwise rotation is positive. The pitch angle refers to the Y-axis magnetic sensor direction angle, that is, Figure 4 The angle of the PITCH axis in the measurement range is -90° to 90°, 0° when horizontal, positive when looking up, and negative when looking down. The roll angle refers to the Z-axis magnetic sensor direction angle, that is Figure 4 The angle of the HEADING axis in the measurement range is -180°~180°, 0° when horizontal, positive for right tilt and negative for left tilt.

[0077] In short, the installation angles of the acceleration acquisition and calculation circuit board 3 and the magnetic probe circuit board 9 described in this embodiment are defined as: the azimuth angle refers to the X-axis direction, the measurement range is 0°~360°, it is 0° when pointing to the magnetic north, and it is positive when rotating clockwise; the pitch angle refers to the Y-axis direction, the measurement range is -90°~90°, it is 0° when horizontal, it is positive when looking up, and it is negative when looking down; the roll angle refers to the Z-axis direction, the measurement range is -180°~180°, it is 0° when horizontal, it is positive when leaning to the right, and it is negative when leaning to the left.

[0078] In this embodiment, the acceleration acquisition calculation circuit board 3 and the magnetic probe circuit board 9 are installed in the "standard 0°" mode. The three magnetic sensor directions are defined as follows: Figure 4As shown, the direction of the A-axis acceleration sensor is along the length direction, vertically downward is positive; the direction of the B-axis acceleration sensor is along the right direction; the direction of the C-axis acceleration sensor is vertically downward, and the above three directions constitute a right-hand coordinate system. The directions of the three corresponding magnetic sensors are the same as the acceleration sensor directions, the direction of the X-axis magnetic sensor (north is positive) is the same as the direction of the A-axis acceleration sensor, the direction of the Y-axis magnetic sensor is the same as the direction of the B-axis acceleration sensor, and the direction of the Z-axis magnetic sensor is the same as the direction of the C-axis acceleration sensor.

[0079] In this embodiment, step S3 is performed by formula The coefficients of the ellipsoid equation are calculated to calculate the ellipsoid center offset Center, and the ellipsoid center offset Center is used as the fixed zero point of the magnetic field interference of the magnetic probe circuit board 9.

[0080] Through the VD decomposition method, the eigenvectors and corresponding eigenvalues ​​of the matrix Mat_r (1:3, 1:3) are obtained. The matrix Mat_r (1:3, 1:3) represents a three-by-three matrix composed of the first three rows and the first three columns of the matrix Mat_r. The eigenvector matrix RV and the eigenvalue diagonal matrix RD obtained after VD decomposition satisfy the following formula: RV*RD*RV T = Mat_r(1:3,1:3), where RD represents the diagonal matrix composed of the eigenvalues ​​of the matrix Mat_r(1:3,1:3), and RV represents the matrix composed of the eigenvectors corresponding to the eigenvalues. Here, the eig function (matrix analysis function) in MATLAB or the recursive real-time iterative method can be used to obtain it.

[0081] Specifically, step S4 in this embodiment includes the following sub-steps:

[0082] Step S401, by formula Obtain the eigenvalue Mat_r after the decomposition matrix, where Center(1:3) represents the first to third vector elements in the ellipsoid center offset Center, and 1:3 represents sequence numbers 1 to 3;

[0083] Step S402, by formula Calculate the ellipsoid axis length Radii of the magnetic field model, where RD represents a diagonal matrix composed of eigenvalues ​​Mat_r, RD(i) represents an eigenvalue element, and i is a natural number from 1 to 3;

[0084] Step S403, taking the minimum axis length min_Radii of the ellipsoid axis length Radii by the formula min_Radii=min(Radii);

[0085] Step S404, by formula The minimum axis length min_Radii is normalized to obtain the normalized scale coefficient Scale, where Radii(i) represents the axis length of the ellipsoid;

[0086] Step S405, by formula mat_Correct = RV*Scale*RV T The scale coefficient matrix mat_Correct of the magnetic probe circuit board 9 is calculated, and RV represents a matrix composed of eigenvectors corresponding to eigenvalues ​​Mat_r.

[0087] Finally, the raw magnetometer data can be directly used to solve the heading after being compensated by the scale coefficient matrix mat_Correct and the ellipsoid center offset Center. The compensation process is as follows: Compensation is performed using the formula Mag = mat_Correct*(Mag'-Center), where Mag' represents the original uncalibrated three-axis magnetometer vector, and Mag represents the calibrated and compensated three-axis magnetometer vector.

[0088] Since the azimuth of this embodiment uses the geomagnetic principle, the magnetic north pole measurement three-dimensional compass is installed away from iron, magnets, engines and other magnetic objects. More specifically, the magnetic probe circuit board 9 is installed away from iron, magnets, engines and other magnetic objects, which can effectively reduce the magnetic interference of the installation environment. Preferably, in this embodiment, the distance between the installation position of the second installation reference plane 7 and the magnetic medium object is controlled to be more than 40 cm, and the magnetic medium object includes any one or more of iron, magnets and engines. At this time, the measurement effect is the best, and as long as the distance between the installation position of the second installation reference plane 7 and the magnetic medium object is controlled to be more than 40 cm, there are no other installation limitations.

[0089] Of course, in actual applications, sometimes the installation position of the magnetic probe circuit board 9 and the distance between it and the magnetic medium object are not controllable. Therefore, when the distance between the installation position of the second installation reference plane 7 and the magnetic medium object is less than 40 cm, after fixing the second installation reference plane 7 and the magnetic medium object, the magnetic probe circuit board 9 and the magnetic medium object are controlled to perform synchronous rotation calibration, which is equivalent to pre-fixing the magnetic medium object and the magnetic probe circuit board 9 relative to each other, maintaining the relative position and distance between the magnetic probe circuit board 9 and the magnetic medium object, and thus making the magnetic interference brought by the magnetic medium object be used as the basic measurement data for overall calibration from the beginning, so as to ensure the effectiveness of calibration and correction, thereby improving the azimuth angle measurement accuracy of the magnetic compass and maximizing the high-precision measurement performance of the three-dimensional compass.

[0090] To sum up, this embodiment realizes the split design between the acceleration acquisition and operation circuit board 3 and the magnetic probe circuit board 9 through the first installation reference surface 1, the second installation reference surface 7 and the double-headed terminal wire 5, and provides an optimized spatial calibration process of the magnetic probe circuit board 9, which not only makes the size of the magnetic probe circuit board 9 smaller, but also facilitates installation in any space with a good magnetic field environment to collect magnetic data, while the acceleration acquisition and operation circuit board 3 can be installed in any space of any environment, thereby effectively reducing the limitations on the installation environment, and can also provide a good foundation for improving the measurement accuracy of the product through the optimized spatial calibration process, which is convenient for the promotion and application of the product.

[0091] The above content is a further detailed description of this embodiment in combination with specific preferred implementation methods, and it cannot be determined that the specific implementation of this embodiment is limited to these descriptions. For ordinary technicians in the technical field to which this embodiment belongs, several simple deductions or replacements can be made without departing from the concept of this embodiment, which should be regarded as falling within the protection scope of this embodiment.

Claims

1. A three-dimensional compass for measuring magnetic north pole with a split design, characterized in that: include: A first mounting reference surface, an acceleration acquisition operation circuit board, a double-headed terminal line, a second mounting reference surface and a magnetic probe circuit board, wherein the acceleration acquisition operation circuit board is arranged on the first mounting reference surface, the magnetic probe circuit board is arranged on the second mounting reference surface, and the acceleration acquisition operation circuit board is connected to the magnetic probe circuit board through the double-headed terminal line; wherein the spatial calibration process of the magnetic probe circuit board includes the following steps: Step S1, constructing an ellipsoid equation for the magnetic field model of the magnetic probe circuit board; Step S2, obtaining a coefficient matrix corresponding to the ellipsoid equation according to the sampling point data of the calibration position; Step S3, calculating the ellipsoid center offset according to the coefficients of the ellipsoid equation, and using the ellipsoid center offset as the fixed zero point of the magnetic field interference of the magnetic probe circuit board; Step S4, obtaining the eigenvalues ​​of the decomposed matrix according to the fixed zero point of the magnetic field interference, and calculating the scale coefficient matrix of the magnetic probe circuit board according to the eigenvalues.

2. The three-dimensional compass for measuring the magnetic north pole with a split design according to claim 1 is characterized in that: In step S1, the formula Ax is used. 2 +By 2 +Cz 2 +2Dxy+2Exz+2Fyz+2Gx+2Hy+2Iz=1 constructs an ellipsoid equation for the magnetic field model of the magnetic probe circuit board, wherein A, B, C, D, E, F, G, H and I respectively represent nine coefficients of the ellipsoid equation, and x, y and z represent the coordinates of the three-axis magnetometer in the magnetic probe circuit board.

3. The three-dimensional compass for measuring magnetic north pole with a split design according to claim 2 is characterized in that: The step S2 comprises the following sub-steps: Step S201, by formula Hk=[x 2 ,y 2 ,z 2 ,2xy,2xz,2yz,2x,2y,2z] 12×9 Calculate the matrix Hk, where Hk represents a 12×9 matrix; Step S202, by formula Xk=(Hk T *Hk) T *Hk T *Yk calculates the coefficient matrix Xk, where Xk represents a 9×1 coefficient matrix corresponding to the nine coefficients A, B, C, D, E, F, G, H, and I; the superscript T represents a transposed matrix; Yk represents a 12×1 first-order matrix, which is used to represent the sampling point data of the twelve calibration positions.

4. The three-dimensional compass for measuring magnetic north pole with a split design according to claim 3 is characterized in that: In step S202, the sampling of the twelve calibration positions includes: The first calibration position is horizontal placement and static sampling in any direction; The second calibration position is placed horizontally and rotated 90° clockwise relative to the first calibration position before static sampling; The third calibration position is placed horizontally and rotated 90° clockwise relative to the second calibration position before static sampling; The fourth calibration position is placed horizontally and rotated 90° clockwise relative to the third calibration position before static sampling; The fifth calibration position is rotated 30° clockwise relative to the fourth calibration position, and the pitch angle is adjusted to 45°±10°, and static sampling is performed; The sixth calibration position, maintaining the pitch angle of the fifth calibration position, rotates 90° clockwise relative to the fifth calibration position, and then performs static sampling; At the seventh calibration position, the pitch angle of the sixth calibration position is maintained, and after rotating 90° clockwise relative to the sixth calibration position, static sampling is performed; The eighth calibration position, maintaining the pitch angle of the seventh calibration position, rotates 90° clockwise relative to the seventh calibration position, and then performs static sampling; The ninth calibration position is rotated 30° clockwise relative to the eighth calibration position, and then the pitch angle is adjusted to -45°±10°, and static sampling is performed; At the tenth calibration position, the pitch angle of the ninth calibration position is maintained, and after rotating 90° clockwise relative to the ninth calibration position, static sampling is performed; At the eleventh calibration position, the pitch angle of the tenth calibration position is maintained, and after rotating 90° clockwise relative to the tenth calibration position, static sampling is performed; At the twelfth calibration position, the pitch angle of the eleventh calibration position is maintained, and after rotating 90° clockwise relative to the eleventh calibration position, static sampling is performed.

5. The three-dimensional compass for measuring magnetic north pole with a split design according to claim 4 is characterized in that: The sampling point adjustment process of the twelve calibration positions is realized by a tripod turntable and a dividing plate, and the magnetic probe circuit board is arranged on the tripod turntable through the dividing plate; during the rotation of the angle, the angle error is controlled within 5 to 10 degrees.

6. The three-dimensional compass for measuring magnetic north pole with a split design according to any one of claims 2 to 5, characterized in that: The step S3 is implemented by formula The coefficients of the ellipsoid equation are calculated to calculate the ellipsoid center offset Center, and the ellipsoid center offset Center is used as the fixed zero point of the magnetic field interference of the magnetic probe circuit board.

7. The three-dimensional compass for measuring magnetic north pole with a split design according to claim 6 is characterized in that: The step S4 comprises the following sub-steps: Step S401, by formula Obtain the eigenvalue Mat_r after the decomposition matrix, where Center(1:3) represents the first to third vector elements in the ellipsoid center offset Center, and 1:3 represents sequence numbers 1 to 3; Step S402, by formula Calculate the ellipsoid axis length Radii of the magnetic field model, where RD represents a diagonal matrix composed of eigenvalues ​​Mat_r, RD(i) represents an eigenvalue element, and i is a natural number from 1 to 3; Step S403, taking the minimum axis length min_Radii of the ellipsoid axis length Radii by the formula min_Radii=min(Radii); Step S404, by formula The minimum axis length min_Radii is normalized to obtain the normalized scale coefficient Scale, where Radii(i) represents the axis length of the ellipsoid; Step S405, by formula mat_Correct = RV*Scale*RV T The scale coefficient matrix mat_Correct of the magnetic probe circuit board is calculated, and RV represents a matrix composed of eigenvectors corresponding to eigenvalues ​​Mat_r.

8. The three-dimensional compass for measuring magnetic north pole according to any one of claims 1 to 5, characterized in that: The distance between the installation position of the second installation reference surface and the magnetic medium object is controlled to be more than 40 cm, and the magnetic medium object includes any one or more of iron, magnet and engine.

9. The three-dimensional compass for measuring magnetic north pole according to any one of claims 1 to 5, characterized in that: When the distance between the installation position of the second installation reference plane and the magnetic medium object is less than 40 cm, after fixing the second installation reference plane and the magnetic medium object, the magnetic probe circuit board and the magnetic medium object are controlled to perform synchronous rotation calibration.

10. The three-dimensional compass for measuring magnetic north pole with a split design according to any one of claims 1 to 5, characterized in that: The installation angles of the acceleration acquisition calculation circuit board and the magnetic probe circuit board are defined as follows: the azimuth refers to the X-axis direction, the measurement range is 0° to 360°, 0° when pointing to the magnetic north, and positive when rotating clockwise; the pitch angle refers to In the Y-axis direction, the measurement range is -90° to 90°, 0° when horizontal, positive when looking up, negative when looking down; The roll angle refers to the Z-axis direction, and the measurement range is -180° to 180°. It is 0° when horizontal, positive for right tilt, and negative for left tilt.

Images