An in-situ calibration method for three-dimensional coils in a three-axis vector atomic magnetometer

Abstract

A method for in-situ calibration of three-dimensional coils in a three-axis vector atomic magnetometer can realize in-situ calibration of the three-dimensional coils in the three-axis atomic magnetometer, correct the coil constant error, non-orthogonality error and zero bias magnetic field error of the three-axis vector atomic magnetometer, help improve the calibration accuracy of the three-dimensional coils in the three-axis vector atomic magnetometer, and reduce the magnetic field coupling and system errors of the three-axis vector atomic magnetometer. It is of great significance to the development of a new generation of ultra-high sensitivity three-axis magnetic field measurement and its applications. In the future, it can serve the fields of quantum navigation, metrology testing, deep space / deep earth magnetic exploration, and biological extremely weak magnetic detection.

Description

Technical Field

[0001] The present invention relates to the field of quantum precision measurement technology, and specifically to an in-situ calibration method for three-dimensional coils in a three-axis vector atomic magnetometer. The method helps to improve the calibration accuracy of the three-dimensional coils in the three-axis vector atomic magnetometer and reduce the magnetic field coupling and system errors of the three-axis vector atomic magnetometer. This method is of great significance for the development of a new generation of ultra-high sensitivity three-axis magnetic field measurement and its applications. In the future, it can serve the fields of quantum navigation, metrology and testing, deep space / deep geomagnetic exploration, and biological extremely weak magnetic detection. Background Art

[0002] Vector atomic magnetometers can significantly improve the magnetic field measurement limit. For example, the atomic magnetometer based on the principle of no spin exchange relaxation has become the magnetometer with the highest measurement sensitivity (theoretical sensitivity can reach aT / Hz). 1 / 2 Order of magnitude). The three-axis vector atomic magnetometer in the vector atomic magnetometer can simultaneously provide the direction and amplitude information of the three-axis vector of the magnetic field. It can be applied to quantum navigation, metrology testing, deep space / deep earth magnetic exploration, biological extremely weak magnetic detection and other fields, and has become the development direction of the new generation of magnetometers. The three-dimensional coil in the three-axis vector magnetometer is used for magnetic field compensation and modulation, and calibration of the magnetometer technical indicators. The calibration error and accuracy of the three-dimensional coil directly affect the working performance of the three-axis vector atomic magnetometer. However, due to the limitations of the production and installation process, the three-dimensional coils in actual application have non-orthogonality errors, coil coefficient errors and zero bias magnetic field error parameters, which lead to magnetic field coupling and system errors in the three-axis vector atomic magnetometer. Therefore, it is necessary to achieve high-precision calibration of the three-dimensional coil in the three-axis vector atomic magnetometer.

[0003] Existing calibration methods for three-dimensional coils in three-axis atomic magnetometers fail to adequately account for error sources, focusing solely on coil constant errors or non-orthogonality errors. Using the least-squares method to solve the calibration problem results in large errors and poor accuracy. Coil constant calibration primarily utilizes a commercial fluxgate magnetometer placed at the coil center for ex-situ measurements. This results in low calibration accuracy and is unsuitable for small three-dimensional coils in small magnetometers. For small three-dimensional coils, coil constants are often directly adopted from simulated coil designs, resulting in significant errors. Existing research on calibration of non-orthogonal angles primarily measures non-orthogonal angles, but does not address error correction through compensation. Therefore, research on in-situ calibration methods for three-dimensional coils in three-axis vector atomic magnetometers is essential. This will facilitate the development of ultra-high-sensitivity vector atomic magnetometers and lay an important foundation for their future application. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the present invention provides an in-situ calibration method for the three-dimensional coil in a three-axis vector atomic magnetometer, which helps to reduce the magnetic field coupling and systematic errors of the three-axis vector atomic magnetometer. It is of great significance and value to the development of a new generation of ultra-high sensitivity three-axis magnetic field measurement and its applications. In the future, it will serve various fields, especially quantum navigation, metrology and testing, deep space / deep earth magnetic exploration, and biological extremely weak magnetic detection.

[0005] The technical solutions of the present invention are as follows:

[0006] An in-situ calibration method for a three-dimensional coil in a three-axis vector atomic magnetometer is characterized by comprising: using the three-dimensional coil in the three-axis vector atomic magnetometer to generate N sets of different calibration magnetic fields, where N is an integer greater than or equal to 4; using the sensitive core of the three-axis vector atomic magnetometer to highly sensitively measure the three-axis vector components of the calibration magnetic field generated by the three-dimensional coil; using a particle swarm algorithm to perform data optimization on the measurement results of the three-axis vector atomic magnetometer to obtain 12 three-dimensional coil error parameters; achieving measurement and correction of the three-dimensional coil non-orthogonality error, coil coefficient error, and zero bias magnetic field error parameters, thereby completing the calibration of the three-dimensional coil.

[0007] The following steps are involved:

[0008] Step 1: demagnetize the magnetic shielding device in the three-axis vector atomic magnetometer and compensate the residual magnetism at the center of the magnetic shielding device to less than 100 pT;

[0009] Step 2: Make the three-axis vector atomic magnetometer work normally, and align the y-measurement direction of the sensitive core of the three-axis vector atomic magnetometer with the uniform magnetic field direction generated by the Y-axis coil of the three-dimensional coil;

[0010] Step 3: Use the signal generator to generate three control currents to drive the uniaxial uniform field coils in the X, Y, and Z directions of the three-dimensional coil to jointly generate a set of calibration magnetic fields B. coil ;

[0011] Step 4: Use the three-axis vector atomic magnetometer sensitive core to measure the calibration magnetic field B generated by the three-dimensional coil with high sensitivity. coil , transfer the measurement result B to the computer, return to step 3, and repeat N times, where N is a positive integer;

[0012] Step 5: Use a computer to optimize and solve the 12 error parameters of the three-dimensional coil based on the particle swarm algorithm: cosη xx ,cosη Xy ,cosη xz ,cosη Zx ,cosη Zy ,cosη Zz ,K X ,K Y,K Z ,B x0 ,B y0 ,B z0 , where η Xx is the angle between the X-axis coil and the x-measurement direction, η Xy is the angle between the X-axis coil and the y-measurement direction, η Xz is the angle between the X-axis coil and the z-measurement direction, η Zx is the angle between the Z-axis coil and the x-measurement direction, η Zy is the angle between the Z-axis coil and the y-measurement direction, η Zz is the angle between the Z-axis coil and the z-measurement direction, K X is the coil constant error coefficient of the X-axis coil, K Y is the coil constant error coefficient of the Y-axis coil, K Z is the coil constant error coefficient of the Z-axis coil, Bx0 is the zero bias magnetic field error in the x-measurement direction, By0 is the zero bias magnetic field error in the y-measurement direction, and Bz0 is the zero bias magnetic field error in the z-measurement direction;

[0013] Step 6: Use the error parameters to obtain the corrected calibration equation, and use the computer to feed the correction result back to the signal generator to drive the three-dimensional coil to generate the calibration magnetic field B. c coil , complete the calibration of the three-dimensional coil.

[0014] Calibration magnetic field B coil =(B coilX ,B coilY ,B coilZ ), where B coilX , B coilY , B coilZ is the effective value of the amplitude of the magnetic field generated by the uniaxial uniform field coil in the X, Y, and Z directions of the three-dimensional coil; the vector magnetic field B measured by the three-axis vector atomic magnetometer is (B x , B y , B z ), where B x , B y , B z is the effective value of the magnetic field amplitude in the three measurement directions of x, y, and z; the calibration magnetic field B generated by the three-axis vector atomic magnetometer on the three-dimensional coil coil The expression of the measurement result B is:

[0015] B=RB coil +B0

[0016] The transformation matrix diag() represents a diagonal matrix, and the zero bias magnetic field B0 = (Bx0, By0, Bz0) if and only if B coil B coilT When is a non-singular matrix, R has a unique solution:

[0017]

[0018] Where T is the matrix transpose operator.

[0019] In order to solve the optimal error parameters of the three-dimensional coil, the residual r equation is established:

[0020] r=||B-(RB coil +B0)||

[0021] Construct the cost equation:

[0022]

[0023] The left side of the equation represents the value of (R, B0) when f(R, B0) takes the minimum value, where m = 1, 2, ..., N is the number of measurements of the three-axis vector atomic magnetometer. To ensure the solution requirements, N is an integer ≥ 4. The optimal solution (R, B0) of the three-dimensional coil error parameters is solved by computer based on the particle swarm algorithm. The cost equation is minimized. At this time, the 12 error parameters (cosη) of the three-dimensional coil in the three-axis vector atomic magnetometer are realized. Xx ,cosη Xy ,cosη Xz ,cosη Zx ,cosη Zy ,cosη Zz ,K X ,K Y ,K Z ,B x0 ,B y0 ,B z0 ) measurement.

[0024] Calculating the non-orthogonal angles of the three-dimensional coil in the X, Y, and Z directions includes:

[0025] The angle β between the X-axis coil and the Y-axis coil xy =η Xy , the angle β between the Z-axis coil and the Y-axis coil yz =η zy , the angle β between the X-axis coil and the Z-axis coil xz :

[0026]

[0027] Optimal solution using conversion matrix and zero bias magnetic field Construct the calibration equation of the three-dimensional coil:

[0028] Among them, B c is the ideal magnetic field required by the three-axis vector atomic magnetometer, The computer transmits the calibration result to the signal generator to drive the three-dimensional coil to generate the calibration magnetic field. At this point, the calibration of the three-dimensional coil is completed.

[0029] The three-dimensional coil is composed of three groups of single-axis uniform field coils arranged along the X, Y, and Z directions. Due to the influence of production technology and installation process, there are non-orthogonal angles in the X, Y, and Z directions of the three-dimensional coil, including the angle β between the X-axis coil and the Y-axis coil. xy , the angle β between the Z-axis coil and the Y-axis coil yz , and the angle β between the X-axis coil and the Z-axis coil xz The existence of non-orthogonal angles causes the three magnetic field directions (X, Y, and Z) generated by the uniaxial uniform field coil of the three-dimensional coil to be not strictly aligned with the three orthogonal measurement directions (X, Y, and Z) of the three-axis vector atomic magnetometer, requiring calibration.

[0030] The three-dimensional coil is located in the magnetic shielding device, and the sensitive core of the three-axis vector atomic magnetometer is located at the center of the three-dimensional coil. The X-axis uniform field coil, the Y-axis uniform field coil, and the Z-axis uniform field coil in the three-dimensional coil are respectively connected to a signal generator. The signal generator is connected to the sensitive core of the three-axis vector atomic magnetometer via a computer. The signal generator generates three control currents for the three-directional coils of the three-dimensional coil, namely, the X, Y, and Z directions. The three control currents enable the three-dimensional coil to generate uniform magnetic fields in the three directions of X, Y, and Z, respectively.

[0031] The three-axis vector atomic magnetometer sensitive core has a high sensitivity better than 1pT / Hz 1 / 2 .

[0032] The magnetic shielding device in the three-axis vector atomic magnetometer needs to be demagnetized to ensure that the residual magnetism at the center is ≤2nT.

[0033] The technical effects of the present invention are as follows: The present invention provides an in-situ calibration method for a three-dimensional coil in a three-axis vector atomic magnetometer, which can realize the in-situ calibration of the three-dimensional coil in the three-axis atomic magnetometer, correct the coil constant error, non-orthogonality error and zero bias magnetic field error of the three-dimensional coil, improve the calibration accuracy of the three-dimensional coil, and help reduce the system error of the three-axis vector atomic magnetometer.

[0034] The advantages of the present invention over the prior art are: (1) This method can measure and correct the non-orthogonality error, coil constant error, and zero bias magnetic field error of the three-dimensional coil in the three-axis vector atomic magnetometer due to the production level and installation process, thereby improving the calibration accuracy of the three-dimensional coil and reducing the magnetic field coupling and system error of the three-axis vector atomic magnetometer. In the application of the three-dimensional coil of the existing three-axis vector atomic magnetometer, there is currently no mature calibration method for measuring and compensating the multi-source errors of the three-dimensional coil. (2) All the components required for the measurement process of this method are the components of the three-axis vector atomic magnetometer itself, and no additional components are required. The in-situ calibration of the three-dimensional coil can be realized, which is conducive to miniaturized application. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The present invention is a schematic diagram of a device structure involved in implementing an in-situ calibration method for a three-dimensional coil in a three-axis vector atomic magnetometer.

[0036] Figure 2 Schematic diagram of the measurement direction of the three-axis vector atomic magnetometer and the magnetic field direction of the three-dimensional coil.

[0037] Figure 3 The present invention is a flow chart of an in-situ calibration method for a three-dimensional coil in a three-axis vector atomic magnetometer. Figure 3 The content includes: Step 1, demagnetizing the magnetic shielding device and compensating the residual magnetism at the center of the magnetic shielding device to less than 100pT; Step 2, ensuring the normal operation of the three-axis vector atomic magnetometer, aligning the y-measurement direction of the sensitive core of the three-axis vector atomic magnetometer with the uniform magnetic field direction generated by the Y-axis coil of the three-dimensional coil; Step 3, using a signal generator to generate three control currents, respectively driving the single-axis uniform field coils in the X, Y, and Z directions of the three-dimensional coil, to jointly generate a set of calibration magnetic fields B coil Step 4: Use the three-axis vector atomic magnetometer sensitive core to measure the calibration magnetic field B generated by the three-dimensional coil with high sensitivity. coil , transfer the measurement result B to the computer, return to step 3, repeat N times, N is a positive integer; step 5, use the computer to optimize and solve the 12 error parameters of the three-dimensional coil based on the particle swarm algorithm, cosη Xx ,cosη Xy ,cosη Xz ,cosη Zx ,cosη Zy ,cosη Zz ,K X ,K Y ,K Z ,B x0 ,B y0 ,B z0 , where η Xxis the angle between the X-axis coil and the x-measurement direction, η Xy is the angle between the X-axis coil and the y-measurement direction, η Xz is the angle between the X-axis coil and the z-measurement direction, η Zx is the angle between the Z-axis coil and the x-measurement direction, η Zy is the angle between the Z-axis coil and the y-measurement direction, η Zz is the angle between the Z-axis coil and the z-measurement direction, K X is the coil constant error coefficient of the X-axis coil, K Y is the coil constant error coefficient of the Y-axis coil, K Z is the coil constant error coefficient of the Z-axis coil, Bx0 is the zero bias magnetic field error in the x-measurement direction, By0 is the zero bias magnetic field error in the y-measurement direction, and Bz0 is the zero bias magnetic field error in the z-measurement direction; Step 6, use the error parameters to obtain the corrected calibration equation, and use the computer to feed back the correction result to the signal generator to drive the three-dimensional coil to generate the calibration magnetic field B c coil , complete the calibration of the three-dimensional coil.

[0038] The accompanying drawings are numeraled as follows: 1 - magnetic shielding device; 2 - three-dimensional coil (composed of three single-axis uniform field coils, namely, an X-axis uniform field coil, a Y-axis uniform field coil, and a Z-axis uniform field coil, which respectively generate uniform magnetic fields in the X, Y, and Z directions); 3 - sensitive core of a three-axis vector atomic magnetometer; 4 - signal generator (generating three control currents for the three-dimensional coils in the X, Y, and Z directions, respectively); 5 - computer; xyz - coordinate axes of the three-axis vector atomic magnetometer or the three-axis vector atomic magnetometer sensitive core or the measurement direction coordinate axes; XYZ is the coordinate axis of the uniform magnetic field direction of the three-dimensional coil; η Xx -The angle between the X-axis coil and the x-measurement direction; η Xy -The angle between the X-axis coil and the y-measurement direction; η Xz -The angle between the X-axis coil and the z-measurement direction; η Zx -The angle between the Z-axis coil and the x-measurement direction; η Zy -The angle between the Z-axis coil and the y-measurement direction; η Zz -The angle between the Z-axis coil and the z-measurement direction. DETAILED DESCRIPTION

[0039] Below is the attached figure ( Figure 1-Figure 3 ) and Examples illustrate the present invention.

[0040] Figure 1 The present invention is a schematic diagram of a device structure involved in implementing an in-situ calibration method for a three-dimensional coil in a three-axis vector atomic magnetometer. Figure 2 Schematic diagram of the measurement direction of the three-axis vector atomic magnetometer and the magnetic field direction of the three-dimensional coil. Figure 3 This is a flow chart of the in-situ calibration method for a three-dimensional coil in a three-axis vector atomic magnetometer. Figures 1 to 3 As shown, an in-situ calibration method for a three-dimensional coil in a three-axis vector atomic magnetometer is provided, which helps to improve the calibration accuracy of the three-dimensional coil in the three-axis vector atomic magnetometer and reduce the magnetic field coupling and system error of the three-axis vector atomic magnetometer. It has important significance and value for the development of a new generation of ultra-high sensitivity three-axis magnetic field measurement and its application. In the future, it will serve various fields, especially inertial measurement, basic physics research, geological exploration, military defense, biomedicine, etc. The method includes the following steps: using the three-dimensional coil in the three-axis vector atomic magnetometer to generate N groups of different calibration magnetic fields, where N is an integer greater than or equal to 4; using the sensitive core of the three-axis vector atomic magnetometer to highly sensitively measure the three-axis vector components of the calibration magnetic field generated by the three-dimensional coil; using the particle swarm algorithm to perform data optimization on the measurement results of the three-axis vector atomic magnetometer to obtain 12 three-dimensional coil error parameters, realizing the measurement and correction of the three-dimensional coil non-orthogonality error, coil coefficient error, and zero bias magnetic field error parameters, and completing the calibration of the three-dimensional coil.

[0041] The three-dimensional coil and the three-axis vector atomic magnetometer sensitive core are both components of the three-axis vector atomic magnetometer. The three-axis vector atomic magnetometer sensitive core is located at the center of the three-dimensional coil, and the three-dimensional coil is located at the center of the magnetic shielding device. The magnetic shielding device needs to be demagnetized to ensure that the residual magnetism at the center is ≤2nT. The three-axis vector atomic magnetometer sensitive core can achieve high sensitivity (better than 1pT / Hz) at its location. 1 / 2 ) Measure the vector of the three-axis magnetic field to obtain the magnetic field component information in the three orthogonal measurement directions of x, y, and z.

[0042] The three-dimensional coil is composed of three groups of single-axis uniform field coils arranged along the X, Y, and Z directions. Due to the influence of production technology and installation process, there are non-orthogonal angles in the X, Y, and Z directions of the three-dimensional coil, including the angle β between the X-axis coil and the Y-axis coil. xy , the angle β between the Z-axis coil and the Y-axis coil yz , and the angle β between the X-axis coil and the Z-axis coil xz The presence of non-orthogonal angles results in the three magnetic field directions (X, Y, and Z) generated by the uniaxial uniform field coil of the three-dimensional coil not being strictly aligned with the three orthogonal measurement directions (X, Y, and Z) of the three-axis vector atomic magnetometer, requiring calibration. The y measurement direction of the three-axis vector atomic magnetometer is aligned with the uniform magnetic field direction generated by the Y-axis coil of the three-dimensional coil.

[0043] like Figure 1An in-situ calibration device for a three-dimensional coil in a three-axis vector atomic magnetometer includes a magnetic shielding device 1, a three-dimensional coil 2, a three-axis vector atomic magnetometer sensitive core 3, a signal generator 4, and a computer 5. Among them, the three-dimensional coil 2 and the three-axis vector atomic magnetometer sensitive core 3 are both components of the three-axis vector atomic magnetometer and are both located inside the magnetic shielding device 1. The three-dimensional coil 2 is located at the center of the three-dimensional coil 2, and the three-dimensional coil 2 is located at the center of the magnetic shielding device 1. The magnetic shielding device 1 is used to provide the three-axis vector atomic magnetometer sensitive core 3 with a weak magnetic field environment required for the three-axis vector atomic magnetometer to work. After demagnetization, the magnetic shielding device 1 can significantly reduce the influence of external magnetic fields such as the earth's magnetic field on the working performance of the three-axis vector atomic magnetometer. The signal generator 4 is used to generate three A control circuit causes the three-dimensional coil 2 to apply three different uniform magnetic fields in the X, Y, and Z directions, further compensating for the residual magnetic field within the magnetic shielding device 1 and generating a calibration magnetic field. The three-axis vector atomic magnetometer sensitive core 3 is used to highly sensitively measure the magnetic field components of the calibration magnetic field generated by the three-dimensional coil 2 in the three orthogonal measurement directions of x, y, and z. A computer 5 reads and processes the magnetic field component information, using a particle swarm algorithm to solve for and correct the 12 error parameters of the three-dimensional coil. The corrected coil parameters are fed back to the signal generator 4 to generate a calibrated three-dimensional uniform magnetic field. This device utilizes a three-axis vector atomic magnetometer to highly sensitively measure the three-axis magnetic field vector components generated by its own three-dimensional coil device. The particle swarm algorithm is then used to optimize the output data to obtain the 12 error parameters for measurement and correction, completing the calibration of the three-dimensional coil.

[0044] Figure 2 This is a schematic diagram of the measurement direction of the three-axis vector atomic magnetometer and the magnetic field direction of the three-dimensional coil. In the three-axis vector atomic magnetometer, the Y-axis coil is aligned with the y-measurement direction of the three-axis vector atomic magnetometer. The deviation angles between the measurement direction of the three-axis vector atomic magnetometer and the magnetic field direction of the three-dimensional coil are as follows: ① The angle η between the X-axis coil and the x-measurement direction Xx ;②The angle η between the X-axis coil and the y-measurement direction Xy ; ③The angle η between the X-axis coil and the z measurement direction Xz ; ④ The angle η between the Z-axis coil and the x-measurement direction Zx ; ⑤The angle η between the Z-axis coil and the y-measurement direction Zy ⑥ Angle η between the Z-axis coil and the z-measurement direction Zz .

[0045] like Figure 3 , an in-situ calibration method for a three-dimensional coil in a three-axis vector atomic magnetometer, comprising the following steps:

[0046] (1) Demagnetize the magnetic shielding device 1 and make the residual magnetism at the center of the magnetic shielding device 1 less than 100 pT.

[0047] (2) To ensure the normal operation of the three-axis vector atomic magnetometer, align the y-measurement direction of the sensitive core 3 of the three-axis vector atomic magnetometer with the direction of the uniform magnetic field generated by the Y-axis coil of the three-dimensional coil 2.

[0048] (3) The signal generator 4 generates three control currents to drive the uniaxial uniform field coils in the X, Y, and Z directions of the three-dimensional coil 2 to generate an effective amplitude value of B. coilX , B coilY , B coilZ The magnetic field of coil =(B coilX ,B coilY ,B coilZ ).

[0049] (4) Using the three-axis vector atomic magnetometer sensitive core 3 to measure the calibration magnetic field B generated by the three-dimensional coil 2 with high sensitivity coil , the vector magnetic field B measured by the three-axis vector atomic magnetometer is (B x , B y , B z ), the effective values ​​of the magnetic field amplitudes in the three measurement directions of x, y, and z are B x , B y , B z The measurement result B is transmitted to the computer 5, and the process returns to step 4 and is repeated N times, where N is an integer greater than or equal to 4.

[0050] (5) The calibration magnetic field B generated by the three-axis vector atomic magnetometer on the three-dimensional coil 2 coil The expression of the measurement result B is:

[0051]

[0052] That is, B=RB coil +B0,

[0053] The transformation matrix diag() represents a diagonal matrix, and the zero bias magnetic field B0 = (Bx0, By0, Bz0). If and only if B coil B coil T ( T When (represents the transpose of the matrix) is a non-singular matrix, R has a unique solution:

[0054]

[0055] In order to solve the optimal error parameters of the three-dimensional coil 2, the residual r equation is established:

[0056] r=||B-(RB coil +B0)||,

[0057] Thus constructing the cost equation:

[0058]

[0059] The left side of the equation represents the value of (R, B0) when f(R, B0) takes the minimum value, where m = 1, 2, ..., N is the number of measurements of the three-axis vector atomic magnetometer. To improve the calibration accuracy, the number of measurements should be as high as possible, and the calibration magnetic field B generated by the three-dimensional coil 2 each time coil To ensure the solution requirements, N is an integer greater than or equal to 4. The computer 5 is used to optimize the cost equation based on the particle swarm algorithm to obtain the optimal solution (R, B0) of the conversion matrix R and the zero bias magnetic field B0. The 12 error parameters (cosη) of the three-dimensional coil 2 can be obtained. Xx ,cosη Xy ,cosη Xz ,cosη Zx ,cosη Zy ,cosη Zz ,K X ,K Y ,K Z ,B x0 ,B y0 ,B z0 ). Thus, the non-orthogonal angles of the three-dimensional coil 2 in the X, Y, and Z directions can also be calculated, including:

[0060] The angle between the X-axis coil and the Y-axis coil

[0061] β xy =η Xy ,

[0062] The angle between the Z-axis coil and the Y-axis coil

[0063] β yz =η Zy ,

[0064] The angle between the X-axis coil and the Z-axis coil

[0065]

[0066] (6) Further correct the error parameters of the three-dimensional coil 2, using the optimal solution of the conversion matrix R and the zero bias magnetic field B0 Construct the calibration equation for the 3D coil 2:

[0067]

[0068] Among them, B c is the ideal magnetic field required by the three-axis vector atomic magnetometer, The computer transmits the calibration result to the signal generator 4, which drives the three-dimensional coil 2 to generate the calibration magnetic field. At this point, the calibration of the three-dimensional coil 2 is completed.

[0069] Any content not described in detail in this specification is prior art known to those skilled in the art. It should be noted that the above description is intended to help those skilled in the art understand the present invention, but does not limit the scope of protection of the present invention. Any equivalent substitution, modification, improvement, and / or simplification of the above description that does not depart from the essence of the present invention shall fall within the scope of protection of the present invention.

Claims

1. An in-situ calibration method for a three-dimensional coil in a three-axis vector atomic magnetometer, characterized in that: include: The three-dimensional coils in the three-axis vector atomic magnetometer are used to generate N different calibration magnetic fields, where N is an integer greater than or equal to 4. The three-axis vector atomic magnetometer's sensitive core is used to highly sensitively measure the three-axis vector components of the calibration magnetic field generated by the three-dimensional coils. The particle swarm optimization algorithm is then used to optimize the measurement results of the three-axis vector atomic magnetometer to obtain 12 three-dimensional coil error parameters. This allows for the measurement and correction of the three-dimensional coil's non-orthogonality error, coil coefficient error, and zero bias magnetic field error parameters, completing the calibration of the three-dimensional coil. The following steps are involved: Step 1: demagnetize the magnetic shielding device in the three-axis vector atomic magnetometer and compensate the residual magnetism at the center of the magnetic shielding device to less than 100 pT; Step 2: Make the three-axis vector atomic magnetometer work normally, and align the y-measurement direction of the sensitive core of the three-axis vector atomic magnetometer with the uniform magnetic field direction generated by the Y-axis coil of the three-dimensional coil; Step 3: Use the signal generator to generate three control currents to drive the uniaxial uniform field coils in the X, Y, and Z directions of the three-dimensional coil to jointly generate a set of calibration magnetic fields B. coil ; Step 4: Use the three-axis vector atomic magnetometer sensitive core to measure the calibration magnetic field B generated by the three-dimensional coil with high sensitivity. coil , transfer the measurement result B to the computer, return to step 3, and repeat N times, where N is a positive integer; Step 5: Use a computer to optimize and solve the 12 error parameters of the three-dimensional coil based on the particle swarm algorithm: cosη Xx ,cosη Xy ,cosη Xz ,cosη Zx ,cosη Zy ,cosη Zz ,K X ,K Y ,K Z ,B x0 ,B y0 ,B z0 , where η Xx is the angle between the X-axis coil and the x-measurement direction, η Xy is the angle between the X-axis coil and the y-measurement direction, η Xz is the angle between the X-axis coil and the z-measurement direction, η Zx is the angle between the Z-axis coil and the x-measurement direction, η Zy is the angle between the Z-axis coil and the y-measurement direction, η Zz is the angle between the Z-axis coil and the z-measurement direction, K X is the coil constant error coefficient of the X-axis coil, K Y is the coil constant error coefficient of the Y-axis coil, K Z is the coil constant error coefficient of the Z-axis coil, Bx0 is the zero bias magnetic field error in the x-measurement direction, By0 is the zero bias magnetic field error in the y-measurement direction, and Bz0 is the zero bias magnetic field error in the z-measurement direction; Step 6: Use the error parameters to obtain the corrected calibration equation, and use the computer to feed the correction results back to the signal generator to drive the three-dimensional coil to generate the calibration magnetic field. Complete the calibration of the three-dimensional coil; Calibration magnetic field B coil =(B coilX ,B coilY ,B coilZ ), where B coilX , B coilY , B coilZ is the effective value of the amplitude of the magnetic field generated by the uniaxial uniform field coil in the X, Y, and Z directions of the three-dimensional coil; the vector magnetic field B measured by the three-axis vector atomic magnetometer is (B x , B y , B z ), where B x , B y , B z is the effective value of the magnetic field amplitude in the three measurement directions of x, y, and z; the calibration magnetic field B generated by the three-axis vector atomic magnetometer on the three-dimensional coil coil The expression of the measurement result B is: B=RB coil +B0 The transformation matrix diag() represents a diagonal matrix, and the zero bias magnetic field B0 = (Bx0, By0, Bz0) if and only if When is a non-singular matrix, R has a unique solution: Where T is the matrix transpose operator; In order to solve the optimal error parameters of the three-dimensional coil, the residual r is established m equation: Construct the cost equation: The left side of the equation represents the value of (R, B0) when f(R, B0) takes the minimum value, where m = 1, 2, ..., N is the number of measurements of the three-axis vector atomic magnetometer. To ensure the solution requirements, N is an integer ≥ 4. The optimal solution (R, B0) of the three-dimensional coil error parameters is solved by computer based on the particle swarm algorithm. The cost equation is minimized. At this point, the measurement of 12 error parameters of the three-dimensional coil in the three-axis vector atomic magnetometer is realized. The 12 error parameters are expressed as follows: (cosη Xx ,cosη Xy ,cosη Xz ,cosη Zx ,cosη Zy ,cosη Zz ,K X ,K Y ,K Z ,B x0 ,B y0 ,B z0 ); Calculating the non-orthogonal angles of the three-dimensional coil in the X, Y, and Z directions includes: The angle β between the X-axis coil and the Y-axis coil xy =η Xy , the angle β between the Z-axis coil and the Y-axis coil yz =η Zy , the angle β between the X-axis coil and the Z-axis coil xz : Optimal solution using the conversion matrix and zero bias magnetic field Construct the calibration equation of the three-dimensional coil: Among them, B c is the ideal magnetic field required by the three-axis vector atomic magnetometer, The computer transmits the calibration result to the signal generator to drive the three-dimensional coil to generate the calibration magnetic field. At this point, the calibration of the three-dimensional coil is completed.

2. The in-situ calibration method for a three-dimensional coil in a three-axis vector atomic magnetometer according to claim 1, characterized in that: The three-dimensional coil is composed of three groups of single-axis uniform field coils arranged along the X, Y, and Z directions. Due to the influence of production technology and installation process, there are non-orthogonal angles in the X, Y, and Z directions of the three-dimensional coil, including the angle β between the X-axis coil and the Y-axis coil. xy , the angle β between the Z-axis coil and the Y-axis coil yz , and the angle β between the X-axis coil and the Z-axis coil xz The existence of non-orthogonal angles causes the three magnetic field directions (X, Y, and Z) generated by the uniaxial uniform field coil of the three-dimensional coil to be not strictly aligned with the three orthogonal measurement directions (X, Y, and Z) of the three-axis vector atomic magnetometer, requiring calibration.

3. The in-situ calibration method for a three-dimensional coil in a three-axis vector atomic magnetometer according to claim 1, characterized in that: The three-dimensional coil is located in the magnetic shielding device, and the sensitive core of the three-axis vector atomic magnetometer is located at the center of the three-dimensional coil. The X-axis uniform field coil, the Y-axis uniform field coil, and the Z-axis uniform field coil in the three-dimensional coil are respectively connected to a signal generator. The signal generator is connected to the sensitive core of the three-axis vector atomic magnetometer via a computer. The signal generator generates three control currents for the three-directional coils of the three-dimensional coil, namely, the X, Y, and Z directions. The three control currents enable the three-dimensional coil to generate uniform magnetic fields in the three directions of X, Y, and Z, respectively.

4. The in-situ calibration method for a three-dimensional coil in a three-axis vector atomic magnetometer according to claim 1, characterized in that: The three-axis vector atomic magnetometer sensitive core has a high sensitivity better than 1pT / Hz 1 / 2 .

5. The in-situ calibration method for a three-dimensional coil in a three-axis vector atomic magnetometer according to claim 1, characterized in that: The magnetic shielding device in the three-axis vector atomic magnetometer needs to be demagnetized to ensure that the residual magnetism at the center is ≤2nT.

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