Error correction method for zero magnetic device vector magnetic sensor based on improved dot product invariant method

Abstract

This invention discloses an error correction method for vector magnetic sensors in zero-magnetic devices based on an improved dot product invariance method. This invention primarily addresses the correction of vector magnetic sensors in zero-magnetic devices. First, an error model is established based on the error sources of the vector magnetic sensor. Then, the improved dot product invariance method is used to calculate error parameters, thereby correcting the vector magnetic sensor. This invention utilizes magnetic shielding technology to generate a zero-magnetic environment. Two sets of triaxial Helmholtz coils are then installed inside and outside this zero-magnetic environment to generate two constant magnetic field vectors. These replace the fixed geomagnetic field vector and another auxiliary constant vector used in the traditional dot product invariance method for correcting vector magnetic sensors. This allows for flexible selection of the angle between the two constant vectors and avoids geomagnetic interference present in the traditional dot product invariance method. This invention avoids problems such as insufficient fitting parameters, the introduction of human error due to moving the vector magnetic sensor during the correction process, and low calibration accuracy caused by a fixed selection of calibration vectors, which are common in traditional vector magnetic sensor calibration methods.

Description

Technical Field

[0001] This invention belongs to the field of error correction of vector magnetic sensors, and specifically relates to an error correction method for zero-magnetic-device vector magnetic sensors based on an improved dot product invariance method. Background Technology

[0002] Magnetism is one of the fundamental physical properties of matter, and magnetic fields are an important way to describe its existence. From molecules and atoms to outer space, everything contains rich magnetic field signals. Magnetic fields can be qualitatively classified into environmental magnetic fields, strong magnetic fields, and weak magnetic fields. Weak magnetic field environments and even near-zero magnetic field environments have attracted much attention from researchers. Near-zero magnetic field environments have broad application prospects in fields such as biomagnetic signal measurement, fundamental physics exploration, national strategic security, deep space exploration, and "zero magnetic science" research.

[0003] Most methods for measuring magnetic fields use magnetic sensors, with vector magnetic sensors, such as triaxial fluxgate sensors, being the most widely used. As the primary sensor used in magnetic field measurement, the accuracy of vector magnetic sensors directly affects the accuracy of the measurement results and the overall evaluation of the magnetic field. Therefore, vector magnetic sensors should always maintain high resolution. However, due to factors such as machining precision, internal circuit characteristics, and environmental influences, the measured values ​​of vector magnetic sensors may differ from their nominal values. Therefore, before leaving the factory and after a period of use, vector magnetic sensors need to undergo experiments to obtain the relationship between the actual and measured values. This process is called sensor calibration, and its purpose is to correct the measured values ​​and reduce the error in magnetic field measurement. The main sources of system error in vector magnetic sensors are as follows: (1) non-orthogonality error of the three axes; (2) different sensitivities of the three axes, i.e., proportional coefficient error; (3) zero magnetic bias caused by residual magnetism inside the sensor; (4) alignment error where the sensor standard does not correspond to the actual value. Traditional vector magnetic sensor calibration methods include ellipsoid fitting, twelve-position method, and dot product invariance method. While the traditional ellipsoidal fitting method is widely used, it can only provide a maximum of nine independent error parameters, which is far from sufficient for high-precision vector magnetic sensors. The traditional twelve-position method, although capable of identifying twelve error parameters, is directly affected by the errors of external hexahedral tooling and requires a high-precision three-axis turntable, introducing errors from manual rotation and increasing costs. Furthermore, the traditional dot product invariance method typically operates in the Earth's magnetic field, using instruments such as accelerometers to provide another constant vector. This not only introduces positional errors but also imposes a fixed angle between the two vectors, severely limiting the accuracy of the dot product invariance method. Therefore, researching a vector magnetic sensor calibration method that avoids sensor movement and offers flexible selection of calibration vectors is of great significance for high-precision vector magnetic sensors. Summary of the Invention

[0004] To address the problems of insufficient fitting parameters in traditional vector magnetic sensor calibration methods, which are unsuitable for high-precision vector magnetic sensors, the introduction of human error by moving the vector magnetic sensor, and low calibration accuracy due to the relatively fixed selection of calibration vectors, this invention provides an error correction method for zero-magnetic device vector magnetic sensors based on an improved dot product invariant method. This method avoids human error introduced by moving the vector magnetic sensor during the calibration process and allows for convenient control of the two vectors used in the dot product invariant method, thus providing a prerequisite for the normal use of vector magnetic sensors.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for error correction of a zero-magnetic-device vector magnetic sensor based on an improved dot product invariance method includes the following steps:

[0007] Step 1: Establish the error parameter model of the vector magnetic sensor:

[0008] The errors of the vector magnetic sensor include zero bias error, proportional coefficient error, non-orthogonality error, and alignment error. Considering the error factors of zero bias error, proportional coefficient error, non-orthogonality error, and alignment error, the error parameter model of the vector magnetic sensor is established as follows:

[0009] B r =K al K or K p (B m +b)

[0010] In the above error parameter model, B r K represents the ideal triaxial magnetic field matrix; al K represents the Euler angle transformation matrix, i.e., the alignment error matrix; or K represents the non-orthogonal error matrix; p b represents the proportionality coefficient error matrix; b represents the zero bias error matrix; B m This represents the output matrix of the vector magnetic sensor;

[0011] in

[0012] Among them, B rx B ry B rz B represents the X, Y, and Z axis components of the actual magnetic field in the external environment; mx B my B mz These represent the output values ​​of the vector magnetic sensor along its three axes: X0, Y0, and Z0, respectively; b x b y b zThese represent the zero-bias errors of the X0, Y0, and Z0 axes, respectively; the X0, Y0, and Z0 coordinate systems are the actual coordinate systems.

[0013] Simplifying the above error parameter model yields the final error model:

[0014] B r =K al K or K p B m +K al K or K p b = LB m +v

[0015] in,

[0016] Among them l 11 ,l 12 ,l 13 ,l 21 ,l 22 ,l 23 ,l 31 ,l 32 ,l 33 v1, v2, and v3 are the twelve error parameters that need to be solved in the final error model of the vector magnetic sensor. They have no specific meaning and their values ​​are obtained by matrix multiplication in the above formula.

[0017] Step 2: Establish two constant vectors based on the improved dot product invariance method:

[0018] A zero-magnetic environment is created by a magnetic shielding chamber. A three-axis Helmholtz coil is placed inside and outside the magnetic shielding chamber. The geomagnetic field vector is simulated by passing a current through the three-axis Helmholtz coil outside the magnetic shielding chamber, and a current is passed through the three-axis Helmholtz coil inside the magnetic shielding chamber as an auxiliary constant vector.

[0019] Three currents were passed through a three-axis Helmholtz coil outside the magnetically shielded cabin to obtain the simulated geomagnetic field vector B generated by it at the center of the zero magnetic environment. out ;

[0020] Three currents are passed through a triaxial Helmholtz coil inside a magnetically shielded chamber, resulting in an auxiliary constant vector B at the center of a zero-magnetic environment, used to improve the dot product invariance method. in ;

[0021] According to B out B in Since the result of the dot product calculation is a constant, the twelve error parameters mentioned in step one are then determined.

[0022] Step 3: Based on the error model established in Step 1 and the two constant vectors established in Step 2, complete the error correction of the vector magnetic sensor. The error correction process is as follows:

[0023] Step 1: Set the angle between the two constant vectors established in Step 2;

[0024] Step 2: Set the simulated geomagnetic field constant vector B respectively. out And another auxiliary constant vector B in After being converted into current according to the relationship between magnetic field and current, it is input into the three-axis Helmholtz coil inside the magnetic shielding cabin and the three-axis Helmholtz coil outside the magnetic shielding cabin;

[0025] Step 3: Simultaneously set the simulated geomagnetic field constant vector B out And another auxiliary constant vector B in Rotate 30° vertically around the center of the zero magnetic environment and record the output of the vector magnetic sensor;

[0026] Step 4: Repeat Step 3 12 times to complete one cycle around the center of the magnetic field environment;

[0027] Step 5: Simulate the constant vector B of the geomagnetic field out And another auxiliary constant vector B in Rotate 30° horizontally around the vertical axis passing through the center point of the zero magnetic environment;

[0028] Step 6: Simultaneously allow the simulated geomagnetic field constant vector B to be... out And another auxiliary constant vector B in Rotate 30° vertically around the center of the zero magnetic environment and record the output of the vector magnetic sensor;

[0029] Step 7: Repeat Step 6 12 times to complete one cycle around the center of the magnetic field environment;

[0030] Step 8: Repeat Steps 5-7 a total of 6 times to complete the simulation of the constant vector B of the geomagnetic field. out And another auxiliary constant vector B in Rotate 180° around the vertical axis that passes through the center point of the zero magnetic environment;

[0031] Step 9: Substitute the 72 sets of data obtained in the first eight steps into u T B r =u T (LB m The fitting process, using +v)=const, yields twelve error parameters, where B... in Substituting u into the above formula, we can change B. out Substituting B into the above formula r ;

[0032] By going through Steps 1 to 9 above, the twelve error parameters mentioned in Step 1 can be obtained, thus completing the error correction of the vector magnetic sensor.

[0033] Furthermore, the three current expressions for the triaxial Helmholtz coil outside the magnetically shielded cabin in step two are denoted as follows:

[0034] I outx =ρ out sinηcosψ

[0035] I outy =ρ out sinηsinψ

[0036] I outz =ρ out cosη

[0037] Where, ρ out The current amplitude is η, and ψ determines the direction of the first vector. All three parameters are set manually.

[0038] In step two, the simulated geomagnetic field vector B generated by the three-axis Helmholtz coil outside the magnetically shielded cabin at the center of the zero magnetic environment... out Recorded as:

[0039]

[0040] Among them, B outx B outy B outz These represent the triaxial magnetic fields generated by the triaxial Helmholtz coils outside the magnetically shielded cabin at the zero magnetic center, K. outx K outy K outz These are the proportional coefficients of the three-axis Helmholtz coils outside the magnetically shielded cabin;

[0041] The three current expressions for the triaxial Helmholtz coil inside the magnetically shielded cabin in step two are denoted as follows:

[0042] I inx =ρ in sinσcosδ

[0043] I iny =ρ in sinσsinδ

[0044] I inz =ρ in cosσ

[0045] Where, ρ in The current amplitude is σ, and δ determines the direction of the second vector. All three parameters are set manually.

[0046] In step two, the auxiliary constant magnetic field vector B generated by the triaxial Helmholtz coil in the magnetically shielded cabin at the center of the zero magnetic environment is... in Recorded as:

[0047]

[0048] Among them, B inx B iny B inz These represent the triaxial magnetic fields generated by the triaxial Helmholtz coils at the zero magnetic center within the magnetically shielded chamber, K. inx K iny K inz These are the proportional coefficients of the three-axis Helmholtz coils inside the magnetically shielded cabin.

[0049] Compared with existing technologies, the advantages of this invention are as follows: This invention proposes an error correction method for a vector magnetic sensor of a zero-magnetic device based on an improved dot product invariance method. By obtaining two controllable constant vectors, it avoids the problem of assuming constant vector invariance in the traditional dot product invariance method, and also solves the problem of a single constant vector selection in the traditional dot product invariance method. By moving the positions of the two constant vectors, it avoids moving the position of the vector magnetic sensor, reduces human error, and improves the correction accuracy. In addition, it also solves the problem of the influence of geomagnetic field fluctuations and magnetic interference on the correction of the vector magnetic sensor. Attached Figure Description

[0050] When considered in conjunction with the accompanying drawings, the invention will be better understood and its accompanying advantages readily apparent from the following detailed description. However, the accompanying drawings, which are provided to further illustrate the invention and constitute a part of this invention, wherein:

[0051] Figure 1 A schematic diagram showing the angular representation of non-orthogonal error coordinates;

[0052] Figure 2 A schematic diagram of Euler angle representation for alignment error coordinates;

[0053] Figure 3 A schematic diagram of the hardware structure for error correction of a vector magnetic sensor;

[0054] Figure 4 This is a flowchart of the error correction method for a vector magnetic sensor with a zero magnetic device based on the improved dot product invariance method of the present invention;

[0055] Figure 5 This is a schematic diagram showing the selection of points for the constant vector of the magnetic field. Specific implementation methods

[0056] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the protection scope of the present invention.

[0057] like Figure 1 The diagram shows the angle representation of the non-orthogonal error coordinates, where angle α is the angle between the projection of the X0 axis onto the OXY plane and X, angle β is the angle between the X0 axis and OXY, and angle γ is the angle between the Y0 axis and the Y axis. The X, Y, Z coordinate system is the ideal coordinate system, and the X0, Y0, Z0 coordinate system is the actual coordinate system.

[0058] like Figure 2 The diagram shows the Euler angle representation of the alignment error coordinates, where the X, Y, Z coordinate system is the ideal coordinate system, the X0, Y0, Z0 coordinate system is the actual coordinate system, and the three Euler angles θ are... φ represents the rotational transformation between the two coordinate systems.

[0059] like Figure 3 The diagram shows a hardware structure for error correction of a vector magnetic sensor. The hardware structure includes a magnetically shielded chamber 1, a vector magnetic sensor 2, a triaxial Helmholtz coil 3 inside the magnetically shielded chamber, and a triaxial Helmholtz coil 4 outside the magnetically shielded chamber. The vector magnetic sensor 2 is positioned at the center of the magnetically shielded chamber 1. The triaxial Helmholtz coil 3 inside the magnetically shielded chamber 1 is located inside the magnetically shielded chamber 1, and the triaxial Helmholtz coil 4 outside the magnetically shielded chamber 1 has three pairs of coils each, arranged along the X, Y, and Z axes.

[0060] like Figure 5 The diagram shows a selection of points for the constant magnetic field vector, where B... out The constant vector of the simulated geomagnetic field generated by the three-axis Helmholtz coil 4 outside the magnetically shielded cabin, where B in λ is the constant vector of the auxiliary magnetic field generated by the triaxial Helmholtz coil 3 inside the magnetically shielded cabin, and λ is the angle between the two magnetic field vectors.

[0061] like Figure 4 As shown, the error correction method for a vector magnetic sensor with a zero magnetic device based on the improved dot product invariance method of the present invention specifically includes the following steps:

[0062] Step 1: Establish the error parameter model of the vector magnetic sensor:

[0063] The errors of vector magnetic sensor 2 generally fall into the following four categories:

[0064] (1) Zero bias error, the expression of its model is as follows:

[0065] B rx =B mx +b x

[0066] B ry =B my +b y

[0067] B rz =B mz +b z

[0068] Among them, B rx B ry B rz B represents the X, Y, and Z axis components of the actual magnetic field in the external environment; mx B my B mz These represent the output values ​​of the vector magnetic sensor 2 along its X0, Y0, and Z0 axes, respectively; b x b y b z These represent the zero-bias errors of the X0, Y0, and Z0 axes, respectively.

[0069] (2) The proportional coefficient error, the expression of which is as follows:

[0070] B rx =K px ×B mx

[0071] B ry =K py ×B my

[0072] B rz =K pz ×B mz

[0073] Among them, K px K py K pz These are the scaling factors for the X0, Y0, and Z0 axes of the vector magnetic sensor 2, respectively.

[0074] (3) Non-orthogonal error, the expression of its model is as follows:

[0075] B rx =B mx ×cosβ×cosα

[0076] B ry =B mx ×cosβ×sinα+Bmy ×cosγ

[0077] B rz =B mx ×sinβ+B my ×sinγ+B mz

[0078] Wherein, angle α is the angle between the projection of the X0 axis onto the OXY plane and the X axis, angle β is the angle between the X0 axis and the OXY plane, and angle γ is the angle between the Y0 axis and the Y axis. For angle representation and coordinate system, please refer to the appendix of the instruction manual. Figure 1 The X, Y, Z coordinate system is the ideal coordinate system, and the X0, Y0, Z0 coordinate system is the actual coordinate system.

[0079] (4) Alignment error, the expression of its model is as follows:

[0080]

[0081] Among them, the three Euler angles θ, φ represents the rotational transformation between the two coordinate systems. For angle representation and coordinate systems, see [link to documentation]. Figure 2 The X, Y, Z coordinate system is the ideal coordinate system, and the X0, Y0, Z0 coordinate system is the actual coordinate system.

[0082] In summary, considering the four error factors—zero bias error, proportional coefficient error, non-orthogonality error, and alignment error—the error parameter model of vector magnetic sensor 2 is established as follows:

[0083] B r =K al K or K p (B m +b)

[0084] Among them, B r K represents the ideal triaxial magnetic field matrix; al K represents the Euler angle transformation matrix, i.e., the alignment error matrix; or K represents the non-orthogonal error matrix; p b represents the proportionality coefficient error matrix; b represents the zero bias error matrix; B m This represents the output matrix of the vector magnetic sensor.

[0085] in

[0086] Further simplifying the above error parameter model, we obtain the final error model as follows:

[0087] B r =K al K or K p Bm +K al K or K p b = LB m +v

[0088] in

[0089] Among them, l 11 ,l 12 ,l 13 ,l 21 ,l 22 ,l 23 ,l 31 ,l 32 ,l 33 v1, v2, v3 are the twelve error parameters of the final error model of the vector magnetic sensor 2. They have no specific meaning and their values ​​are obtained by matrix multiplication in the above formula.

[0090] Step 2: Establish two constant vectors based on the improved dot product invariance method:

[0091] The traditional dot product invariance method uses a known constant auxiliary vector to perform a dot product operation with the Earth's magnetic field, which is considered a constant vector over a short period of time, as shown in the following formula:

[0092] u T B r =u T (LB m +v)=const

[0093] Among them, u T Given a known 1×3 vector, B is provided using instruments such as accelerometers. r Let be the Earth's magnetic field as a constant vector, where `const` represents a constant. Based on the fact that the product of two vectors is a constant, the twelve error parameters of the final error model in step one can be calculated. These two vectors not only have positional errors, but the angle between them is also fixed, limiting the accuracy of the dot product invariance method.

[0094] This invention uses magnetic shielding technology to create a zero-magnetic environment. Inside and outside the magnetic shielding chamber 1, a three-axis Helmholtz coil 3 and an outside three-axis Helmholtz coil 4 are placed. Current is passed through the outside three-axis Helmholtz coil 4 to simulate the geomagnetic field vector, and current is passed through the outside three-axis Helmholtz coil 3 as an auxiliary constant vector.

[0095] The magnitude of the central magnetic field is controlled by controlling the current in the triaxial Helmholtz coil. The relationship between the current and the magnetic field is as follows:

[0096] B x =K x ×I x

[0097] B y =K y ×I y

[0098] B z =K z ×I z

[0099] Among them B x B y B z The magnetic field generated at the center of the triaxial Helmholtz coil; I x I y I z These represent the currents flowing through the triaxial Helmholtz coils; K x K y K z These are the proportional coefficients of the magnetic field and current of a three-axis Helmholtz coil, respectively.

[0100] By passing three currents through the triaxial Helmholtz coil 4 outside the magnetically shielded cabin, a constant vector simulating the Earth's magnetic field can be generated at the center of the magnetically shielded cabin 1. The parameter expressions for the three currents are as follows:

[0101] I outx =ρ out sinηcosψ

[0102] I outy =ρ out sinηsinψ

[0103] I outz =ρ out cosη

[0104] Where ρ out The current amplitude is η, and ψ determines the direction of the first vector. All three parameters are set manually.

[0105] Substituting the above current expression into the expression for the relationship between current and magnetic field, we obtain the simulated geomagnetic field vector B generated by the three-axis Helmholtz coil 4 outside the magnetic shielding cabin at the center of the magnetic shielding cabin 1. out Its expression is as follows:

[0106]

[0107] Among them, B outx B outy B outz These represent the triaxial magnetic field generated by the triaxial Helmholtz coil 4 outside the magnetically shielded cabin at the center of the magnetically shielded cabin 1, K. outx K outy K outzThese are the proportional coefficients of the three-axis Helmholtz coil 4 outside the magnetically shielded cabin.

[0108] By passing three currents through the triaxial Helmholtz coil 3 inside the magnetically shielded chamber, an auxiliary constant vector for the dot product invariance method can be generated at the center of the magnetically shielded chamber 1. The parameter expressions of the three currents are as follows:

[0109] I inx =ρ in sinσcosδ

[0110] I iny =ρ in sinσsinδ

[0111] I inz =ρ in cosσ

[0112] Where, ρ in The current amplitude is σ, and the direction of the second vector is determined by δ. All three parameters are set manually.

[0113] Substituting the above current expression into the expression for the relationship between current and magnetic field, we obtain the auxiliary constant vector B generated by the triaxial Helmholtz coil 3 at the center of the magnetically shielded cabin 1. in Its expression is as follows:

[0114]

[0115] Among them, B inx B iny B inz These represent the triaxial magnetic field generated by the triaxial Helmholtz coil 3 at the center of the magnetically shielded chamber 1, respectively, and K. inx K iny K inz These are the proportional coefficients of the three-axis Helmholtz coil 3 inside the magnetically shielded cabin.

[0116] According to B out B in Multiplying two constant vectors yields a constant, from which the twelve error parameters of the final error model in step one can be obtained, thus enabling the correction of the error of vector magnetic sensor 2.

[0117] Step 3: Based on the error model established in Step 1 and the two constant vectors established in Step 2, perform error correction on the vector magnetic sensor 2. Create a zero-magnetic environment using passive magnetic shielding and active magnetic compensation techniques. Then, install the triaxial Helmholtz coil 3 inside the magnetic shielding chamber and the triaxial Helmholtz coil 4 outside the magnetic shielding chamber 1, placing the vector magnetic sensor 2 at the center of the magnetic shielding chamber 1. The error correction process is as follows:

[0118] Step 1: Set the angle between the two constant vectors established in Step 2;

[0119] Step 2: Set the simulated geomagnetic field constant vector B respectively. out After being converted into current according to the relationship between magnetic field and current, it is input into the three-axis Helmholtz coil 4 outside the magnetically shielded cabin, and another auxiliary constant vector B is used. in After being converted into current according to the relationship between magnetic field and current, it is input into the three-axis Helmholtz coil 3 in the magnetic shielding cabin;

[0120] Step 3: Simultaneously set the simulated geomagnetic field constant vector B out And another auxiliary constant vector B in Rotate 30° vertically around the center of the zero magnetic environment and record the output of the vector magnetic sensor;

[0121] Step 4: Repeat Step 3 12 times to complete one cycle around the center of the magnetic field environment;

[0122] Step 5: Simulate the constant vector B of the geomagnetic field out And another auxiliary constant vector B in Rotate 30° horizontally around the vertical axis passing through the center point of the zero magnetic environment;

[0123] Step 6: Simultaneously allow the simulated geomagnetic field constant vector B to be... out And another auxiliary constant vector B in Rotate 30° vertically around the center of magnetic shielding chamber 1 and record the output of the vector magnetic sensor;

[0124] Step 7: Repeat Step 6 12 times to complete one cycle around the center of the magnetic shielding chamber 1;

[0125] Step 8: Repeat Steps 5-7 a total of 6 times to complete the simulation of the constant vector B of the geomagnetic field. out And another auxiliary constant vector B in Rotate 180° around the vertical axis that passes through the center point of magnetic shielding chamber 1;

[0126] Step 9: Substitute the 72 sets of data obtained in the first eight steps into u T B r =u T (LB m The fitting process, using +v)=const, yields twelve error parameters, where B... in Substituting u into the above formula, we can change B. out Substituting B into the above formula r .

[0127] By using Steps 1 to 9 above, the twelve error parameters mentioned in Step 1 can be obtained, thus completing the error correction of the vector magnetic sensor 2.

[0128] By following steps one, two, and three above, error modeling and error correction of vector sensor 2 in magnetic shielding chamber 1 can be achieved.

[0129] The contents not described in detail in this specification are prior art known to those skilled in the art. Those skilled in the art will readily understand that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for error correction of a zero flux device vector magnetic sensor based on an improved dot product invariant method, characterized by , comprising the following steps: Step one, establishing a vector magnetic sensor error parameter model; Step two, establishing two constant vectors based on the improved dot product invariant method; including: A zero magnetic environment is created by a magnetic shielding cabin, and a three-axis Helmholtz coil inside the magnetic shielding cabin and a three-axis Helmholtz coil outside the magnetic shielding cabin are placed inside and outside the magnetic shielding cabin. The three-axis Helmholtz coil outside the magnetic shielding cabin is simulated by passing current through the three-axis Helmholtz coil outside the magnetic shielding cabin to simulate the geomagnetic field vector, and the three-axis Helmholtz coil inside the magnetic shielding cabin is passed through the current as an auxiliary constant vector; In the magnetic shielding cabin outside the three-axis Helmholtz coil, three currents are passed to obtain the simulated geomagnetic field vector generated at the center of the zero magnetic environment ; In the three-axis Helmholtz coil in the magnetic shield cabin, three currents are passed to obtain an auxiliary constant vector at the center of the zero magnetic environment for improving the dot product invariant method ; According to , The dot product calculation results in a constant, and twelve error parameters are found. Step three, according to the error model established in step one and the two constant vectors established in step two, complete the error correction of the vector magnetic sensor; The error correction includes the following steps: Step 1: Set the angle between the two constant vectors established in step two; Step 2: The set constant vector of the simulated geomagnetic field and another auxiliary constant vector are converted into currents according to the magnetic field and current relationship and input into the three-axis Helmholtz coils in the magnetic shielding cabin and the three-axis Helmholtz coils outside the magnetic shielding cabin. Step 3: Rotate the simulated geomagnetic field constant vector and another auxiliary constant vector 30° around the center of the zero magnetic environment to the vertical direction, record the vector magnetic sensor output; Step 4: Repeat Step 3 to complete a one-week cycle around the center of the magnetic field environment; Step 5: the analog geomagnetic field constant vector and another auxiliary constant vector rotating in the horizontal direction around the vertical axis of the zero magnetic environment center point ; Step 6: Rotate the simulated geomagnetic field constant vector and the other auxiliary constant vector around the center of the zero magnetic environment by 30° in the vertical direction, and record the vector magnetic sensor output; Step 7: Repeat Step 6 to complete a one-week cycle around the center of the magnetic field environment; Step 8: Repeat Step 5-7 to complete the simulation of the geomagnetic field constant vector and another auxiliary constant vector Rotation around the vertical axis bypassing the zero magnetic environment center point ; Step 9: Substitute the data from the previous eight steps into Twelve error parameters are obtained by fitting, where the auxiliary constant vector is substituted into the above equation The simulated geomagnetic field constant vector is substituted into the above equation ; represents the ideal three-axis magnetic field matrix, represents the vector magnetic sensor output matrix, is a known 1x3 vector provided by the accelerometer, represents a constant; the superscript T represents the transpose of a matrix; Through the above Step 1 to Step 9, twelve error parameters are obtained, and the error correction of the vector magnetic sensor is completed.

2. The error correction method for a zero flux device vector magnetic sensor based on the improved dot product invariant method according to claim 1, characterized in that: The step one includes: The vector magnetic sensor error includes zero offset error, proportional coefficient error, non-orthogonal error and alignment error, and the error factors of zero offset error, proportional coefficient error, non-orthogonal error and alignment error are considered to establish the error parameter model of the vector magnetic sensor as follows: ； In the error parameter model above, denotes the ideal three-axis magnetic field matrix; denotes the Euler angle conversion matrix, i.e. the alignment error matrix; denotes the non-orthogonality error matrix; denotes the scale factor error matrix; denotes the bias error matrix; denotes the vector magnetic sensor output matrix; wherein , , ; wherein, , , respectively represent the three-axis components of the actual magnetic field in the external environment; , , ; , , respectively represent the output values of the three-axis of the vector magnetic sensor; , , ; , , respectively represent the zero-offset errors of the three-axis; , , ; , , the coordinate system is the actual coordinate system; The above error parameter model is simplified, that is, the final error model is obtained: ； wherein , ; wherein, are the twelve error parameters to be solved in the final error model of the vector magnetic sensor.

3. The error correction method for a zero flux device vector magnetic sensor based on the improved dot product invariant method according to claim 2, characterized in that: The three current expressions of the three-axis Helmholtz coil outside the magnetic shielding cabin in step two are recorded as: ； wherein, is the current amplitude, and determines the direction of the first vector, all three parameters are set by the user; In the second step, the magnetic shielding cabin outside the three-axis Helmholtz coil generates an analog geomagnetic field vector at the center of the zero magnetic environment Noted: ； wherein, , , Bx, By, Bz are the three-axis magnetic field generated by the magnetic shielding outside the three-axis Helmholtz coil at the zero magnetic center, , , are the proportional coefficients of the magnetic shielding outside the three-axis Helmholtz coil, respectively. The three current expressions of the three-axis Helmholtz coil inside the magnetic shielding cabin in step two are recorded as: ； wherein, is the current amplitude, and determine the direction of the second vector, all three parameters are set by the user. In the second step, the auxiliary constant magnetic field vector generated by the three-axis Helmholtz coil in the magnetic shielding cabin at the center of the zero magnetic environment is denoted as: ； wherein, , , are the three-axis magnetic fields generated by the three-axis Helmholtz coils in the magnetic shielded room at the zero magnetic center, respectively, , , are the scale factors of the three-axis Helmholtz coils in the magnetic shielded room, respectively.

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