A CPT atomic magnetometer steering error calibration system and method

Abstract

This invention discloses a CPT atomic magnetometer steering error calibration system and method. The system includes a CPT atomic magnetometer, a three-axis vector fluxgate magnetometer, and an electronic control unit. The electronic control unit includes a data acquisition module, a power supply module, and an FPGA magnetic field calibration calculation module. This invention obtains the CPT atomic magnetometer steering error calibration function through ground calibration testing. The angle θ between the magnetic field and the laser direction is measured using the three-axis vector fluxgate magnetometer. θ is then substituted into the steering error calibration function, and the steering error calibration of the CPT atomic magnetometer is achieved through FPGA-based steering error calibration.

Description

Technical Field

[0001] This invention relates to a CPT atomic magnetometer steering error calibration system and method, belonging to the technical field of atomic magnetometers. Background Technology

[0002] The CPT (Coherent population trapping) atomic magnetometer measures magnetic fields by utilizing the Zeeman splitting of atomic energy levels. It features high precision, low energy consumption, omnidirectionality, and good long-term stability, and can be applied to scientific and technological fields such as mineral exploration, geomagnetic mapping, navigation and positioning, and healthcare.

[0003] However, the physical mechanism of the CPT atomic magnetometer causes the measurement results to vary with the angle between the probe laser direction and the magnetic field direction. When the angle varies from 0 to 180°, the peak value of the magnetic field fluctuation is about 5 nT, which cannot meet the requirements of high-precision magnetic field detection under dynamic conditions. Therefore, it is urgent to provide a CPT atomic magnetometer steering error calibration system and method. Summary of the Invention

[0004] The problem solved by this invention is to provide a CPT atomic magnetometer steering error calibration system and method to address the shortcomings and defects of existing technologies. This system corrects the steering error of the CPT atomic magnetometer during dynamic measurement, enabling the CPT atomic magnetometer to have excellent measurement accuracy and a wider range of engineering applications.

[0005] The technical solution of this invention is:

[0006] A CPT atomic magnetometer steering error calibration system includes: a CPT atomic magnetometer, a three-axis vector fluxgate magnetometer, and an electronic control unit;

[0007] The electronic control unit includes a data acquisition module, a power supply and distribution module, and an FPGA magnetic field calibration and calculation module;

[0008] The three-axis vector fluxgate magnetometer and the CPT atomic magnetometer are fixedly mounted on the same fixture, with the Z-axis of the three-axis vector fluxgate magnetometer parallel to the laser direction of the CPT atomic magnetometer. A power supply module provides power, a data acquisition module acquires scalar and vector magnetic field data, and an FPGA magnetic field calibration calculation module processes the acquired magnetic field data to calibrate the CPT atomic magnetometer's steering error. Specifically:

[0009] The steering error of the CPT atomic magnetometer is functionally mapped to the included angle θ, which refers to the angle between the laser direction and the magnetic field direction of the CPT atomic magnetometer probe. The steering error calibration function of the CPT atomic magnetometer is obtained through ground calibration test. The included angle θ is measured by a three-axis vector fluxgate magnetometer calibrated by two iterations. The included angle θ is substituted into the steering error calibration function to perform steering error calibration.

[0010] Furthermore, the initial error parameters of the three-axis vector fluxgate magnetometer are obtained through ground calibration, and a second calibration is performed at the work site. That is, the three-axis vector fluxgate magnetometer is iteratively calibrated using the total magnetic field data output by the CPT atomic magnetometer after the steering error calibration, until the difference between the non-orthogonal angles of the Z-axis calculated by the two calibrations is less than or equal to 0.01°. The parameters of the three-axis vector fluxgate magnetometer after this calibration are used as the initial parameters for the next calibration.

[0011] Furthermore, the steering error is the amplitude of the magnetic field measurement result fluctuating around the true value as the angle θ between the probe laser direction and the magnetic field direction changes.

[0012] Furthermore, the steering error calibration function is obtained by rotating the CPT atomic magnetometer probe 360° in a plane parallel to the magnetic field direction under uniform and constant magnetic field conditions, recording a set of magnetic field data at fixed angles of no more than 15° each time, and then fitting the magnetic field data by difference.

[0013] Furthermore, the angle θ between the laser direction and the magnetic field direction of the CPT atomic magnetometer probe is equal to the angle between the Z-axis of the three-axis vector fluxgate magnetometer and the magnetic field direction, which is calculated using the cosine formula of the vector angle.

[0014] Furthermore, the CPT atomic magnetometer is a total field scalar magnetic field information sensor that converts the total magnetic field scalar magnetic field information into an electrical signal; the three-axis vector fluxgate magnetometer is a magnetic field vector information sensor that converts the total magnetic field vector information into an electrical signal.

[0015] This invention also proposes a method for calibrating the steering error of a CPT atomic magnetometer, comprising:

[0016] (1) Fix the three-axis vector fluxgate magnetometer and the CPT atomic magnetometer on the same fixture, and make the Z-axis of the three-axis vector fluxgate magnetometer parallel to the laser direction of the CPT atomic magnetometer;

[0017] (2) Voltage conversion is achieved through the power supply and distribution module to power the CPT atomic magnetometer, the three-axis vector fluxgate magnetometer and the electronic control unit;

[0018] (3) The scalar and vector magnetic field electrical signals are acquired through the data acquisition module and converted into digital signals and transmitted to the FPGA magnetic field calibration calculation module;

[0019] (4) Obtain the CPT atomic magnetometer steering error calibration function through ground calibration test;

[0020] (5) Perform the first ground calibration of the three-axis vector fluxgate magnetometer: The three-axis vector fluxgate magnetometer is calibrated in a ground environment to obtain the initial error parameters of the fluxgate;

[0021] (6) The included angle θ is measured by the three-axis vector fluxgate magnetometer, and θ is substituted into the steering error calibration function to realize the steering error calibration of the CPT atomic magnetometer;

[0022] (7) Perform secondary calibration of the three-axis vector fluxgate magnetometer: Use the total field data output by the CPT atomic magnetometer after calibration through the steering error to calibrate the fluxgate magnetometer. Stop the iterative calibration calculation when the difference between the non-orthogonal angles of the Z-axis calculated for the three-axis vector fluxgate magnetometer before and after the calibration is less than or equal to 0.01°, and use the parameters after this fluxgate calibration as the initial parameters for the next calibration.

[0023] Furthermore, the CPT atomic magnetometer's steering error is functionally mapped to the included angle θ; the steering error is the amplitude of the magnetic field measurement result fluctuating around the true value as the angle θ between the probe laser direction and the magnetic field direction changes.

[0024] Furthermore, the steering error calibration function is obtained by rotating the CPT atomic magnetometer probe 360° in a plane parallel to the magnetic field direction under uniform and constant magnetic field conditions, recording a set of magnetic field data at fixed angles, with the angle not exceeding 15°, and then performing difference fitting on the magnetic field data.

[0025] Furthermore, the angle θ between the laser direction and the magnetic field direction of the CPT atomic magnetometer probe is equal to the angle between the Z-axis of the three-axis vector fluxgate magnetometer and the magnetic field direction, which is calculated using the cosine formula of the vector angle.

[0026] The beneficial effects of this invention compared to the prior art are:

[0027] (1) This invention solves the problem that the turning error of the CPT atomic magnetometer affects the accuracy of magnetic field measurement under dynamic measurement conditions, and improves the engineering adaptability of the CPT atomic magnetometer under dynamic measurement conditions;

[0028] (2) The CPT atomic magnetometer steering error calibration system of the present invention adopts a combination of a three-axis vector fluxgate magnetometer and a CPT atomic scalar magnetometer. The fluxgate magnetometer provides magnetic field direction information to the CPT atomic magnetometer for steering error compensation, and the CPT atomic magnetometer provides high-precision total magnetic field scalar data to the fluxgate magnetometer for fluxgate zero drift and non-orthogonality calibration. The total magnetic field measurement accuracy is improved by the interaction of data from the two magnetometers.

[0029] (3) The present invention provides a method for calibrating the steering error of a CPT atomic magnetometer. The method adopts an iterative calibration approach, which uses the total field data output by the CPT atomic magnetometer after the steering error calibration to perform iterative calibration and calibration of the fluxgate magnetometer. This solves the problem that the zero-point drift of the fluxgate magnetometer affects the calibration accuracy of the CPT atomic magnetometer steering error. Attached Figure Description

[0030] Figure 1 This invention relates to a CPT atomic magnetometer steering error calibration system.

[0031] Figure 2 This invention describes the installation and fixing method of the CPT atomic magnetometer and the three-axis vector fluxgate magnetometer in the CPT atomic magnetometer steering error calibration system of the present invention;

[0032] Figure 3 This is a schematic diagram of the rotational error of the CPT atomic magnetometer. Detailed Implementation

[0033] The technical solutions of the present invention will now be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention.

[0034] The purpose of this invention is to provide a CPT atomic magnetometer steering error calibration system and method, which solves the problem that steering error affects the magnetic field measurement accuracy of CPT atomic magnetometer under dynamic measurement conditions, and improves the engineering adaptability of CPT atomic magnetometer under dynamic measurement conditions.

[0035] See Figures 1-2 This invention provides a CPT atomic magnetometer steering error calibration system, comprising a CPT atomic magnetometer, a three-axis vector fluxgate magnetometer, and an electronic control unit. The electronic control unit includes a data acquisition module, a power supply module, and an FPGA magnetic field calibration calculation module.

[0036] This invention employs a combination of a three-axis vector fluxgate magnetometer and a CPT atomic scalar magnetometer. The fluxgate magnetometer provides magnetic field direction information to the CPT atomic magnetometer for steering error compensation, while the CPT atomic magnetometer provides high-precision total magnetic field scalar data to the fluxgate magnetometer for fluxgate zero-point drift and non-orthogonality calibration. By fusing data from the two magnetometers, the accuracy of total magnetic field measurement is improved.

[0037] The CPT atomic magnetometer is a total field scalar magnetic field information sensor that converts total field scalar magnetic field information into electrical signals; the three-axis vector fluxgate magnetometer is a magnetic field vector information sensor that converts magnetic field vector information into electrical signals; the power supply module can realize power conversion, supplying voltages that meet the requirements of electronic devices to the circuit boards of the CPT atomic magnetometer, the three-axis vector fluxgate magnetometer, and the electronic control unit; the data acquisition module can realize the acquisition of scalar and vector magnetic field electrical signals and convert them into digital signals for transmission to the FPGA magnetic field calibration calculation module; the FPGA magnetic field calibration calculation module performs steering error calibration calculation, realizing three-axis vector fluxgate calibration calculation, included angle θ calculation, and CPT atomic magnetometer steering error calibration calculation.

[0038] like Figure 3 As shown, the steering error of the CPT atomic magnetometer is functionally mapped to the included angle θ, where included angle θ refers to the angle between the laser direction and the magnetic field direction of the CPT atomic magnetometer probe. The steering error calibration function of the CPT atomic magnetometer is obtained through ground calibration test. The included angle θ is measured by a three-axis vector fluxgate magnetometer calibrated by two iterations. The included angle θ is substituted into the steering error calibration function to perform steering error calibration.

[0039] Steering error calibration function: Under uniform and constant magnetic field conditions, the CPT atomic magnetometer probe is rotated 360° in a plane parallel to the magnetic field direction. At fixed angles, no more than 15°, a set of magnetic field data is recorded. The steering error calibration function can be obtained by fitting the difference of the magnetic field data.

[0040] The three-axis vector fluxgate magnetometer and the CPT atomic magnetometer are fixedly mounted on the same fixture to ensure that the Z-axis of the fluxgate is parallel to the laser direction of the CPT atomic magnetometer.

[0041] The tooling must be non-magnetic and have excellent machinability, such as aluminum alloy.

[0042] The initial error parameters of the fluxgate are obtained through ground calibration. A second calibration is performed at the work site. The fluxgate magnetometer is iteratively calibrated using the total field data output by the CPT atomic magnetometer after the steering error calibration, until the difference between the non-orthogonal angles of the Z-axis calculated by the two calibrations is less than or equal to 0.01°. The parameters after this fluxgate calibration are used as the initial parameters for the next calibration.

[0043] The included angle θ is equal to the angle between the Z-axis of the three-axis vector fluxgate magnetometer and the magnetic field method, and can be calculated using the cosine formula of the vector angle. Substituting θ into the steering error calibration function, the steering error calibration of the CPT atomic magnetometer can be achieved.

[0044] This invention also proposes a method for calibrating the steering error of a CPT atomic magnetometer, comprising the following steps:

[0045] (1) Fix the three-axis vector fluxgate magnetometer and the CPT atomic magnetometer on the same fixture, and make the Z-axis of the three-axis vector fluxgate magnetometer parallel to the laser direction of the CPT atomic magnetometer;

[0046] (2) Voltage conversion is achieved through the power supply and distribution module to power the CPT atomic magnetometer, the three-axis vector fluxgate magnetometer and the electronic control unit;

[0047] (3) The scalar and vector magnetic field electrical signals are acquired through the data acquisition module and converted into digital signals and transmitted to the FPGA magnetic field calibration calculation module;

[0048] (4) Obtain the CPT atomic magnetometer steering error calibration function through ground calibration test;

[0049] (5) Perform the first ground calibration of the three-axis vector fluxgate magnetometer: The three-axis vector fluxgate magnetometer is calibrated in a ground environment to obtain the initial error parameters of the fluxgate;

[0050] (6) The included angle θ is measured by the three-axis vector fluxgate magnetometer, and θ is substituted into the steering error calibration function to realize the steering error calibration of the CPT atomic magnetometer;

[0051] (7) Perform secondary calibration of the three-axis vector fluxgate magnetometer: Use the total field data output by the CPT atomic magnetometer after calibration through the steering error to calibrate the fluxgate magnetometer. Stop the iterative calibration calculation when the difference between the non-orthogonal angles of the Z-axis calculated for the three-axis vector fluxgate magnetometer before and after the calibration is less than or equal to 0.01°, and use the parameters after this fluxgate calibration as the initial parameters for the next calibration.

[0052] Because the three-axis vector fluxgate magnetometer suffers from zero-point drift, affecting the calibration accuracy of the CPT atomic magnetometer's steering error, this invention obtains the initial error parameters of the three-axis vector fluxgate magnetometer through ground calibration and performs a secondary calibration at the work site. Specifically, the total field data output by the CPT atomic magnetometer after steering error calibration is used to iteratively calibrate the three-axis vector fluxgate magnetometer until the difference between the non-orthogonal angles of the Z-axis calculated from the two calibrations is less than or equal to 0.01°. The parameters after this fluxgate calibration are then used as the initial parameters for the next calibration. This invention solves the problem of steering error affecting the magnetic field measurement accuracy of the CPT atomic magnetometer under dynamic measurement conditions, improving the engineering adaptability of the CPT atomic magnetometer under dynamic measurement conditions.

[0053] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention based on the above-disclosed technical content without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A CPT atomic magnetometer steering error calibration system, characterized in that... include: CPT atomic magnetometer, three-axis vector fluxgate magnetometer and electronic control unit; The electronic control unit includes a data acquisition module, a power supply and distribution module, and an FPGA magnetic field calibration and calculation module; The three-axis vector fluxgate magnetometer and the CPT atomic magnetometer are fixedly mounted on the same fixture, with the Z-axis of the three-axis vector fluxgate magnetometer parallel to the laser direction of the CPT atomic magnetometer. A power supply module provides power, a data acquisition module acquires scalar and vector magnetic field data, and an FPGA magnetic field calibration calculation module processes the acquired magnetic field data to calibrate the CPT atomic magnetometer's steering error. Specifically: The steering error of the CPT atomic magnetometer is functionally mapped to the included angle θ, which refers to the angle between the laser direction and the magnetic field direction of the CPT atomic magnetometer probe. The steering error calibration function of the CPT atomic magnetometer is obtained through ground calibration test. The included angle θ is measured by a three-axis vector fluxgate magnetometer calibrated by two iterations. The included angle θ is substituted into the steering error calibration function to perform steering error calibration.

2. The CPT atomic magnetometer steering error calibration system according to claim 1, characterized in that: The initial error parameters of the three-axis vector fluxgate magnetometer are obtained through ground calibration, and a second calibration is performed at the work site. That is, the three-axis vector fluxgate magnetometer is iteratively calibrated using the total magnetic field data output by the CPT atomic magnetometer after the steering error calibration, until the difference between the non-orthogonal angles of the Z-axis calculated by the two calibrations is less than or equal to 0.01°. The parameters of the three-axis vector fluxgate magnetometer after this calibration are used as the initial parameters for the next calibration.

3. The CPT atomic magnetometer steering error calibration system according to claim 1, characterized in that: The steering error is the amplitude of the magnetic field measurement result fluctuating around the true value as the angle θ between the probe laser direction and the magnetic field direction changes.

4. The CPT atomic magnetometer steering error calibration system according to claim 3, characterized in that: The steering error calibration function is obtained by rotating the CPT atomic magnetometer probe 360° in a plane parallel to the magnetic field direction under uniform and constant magnetic field conditions, recording a set of magnetic field data at fixed angles of no more than 15° each time, and then fitting the magnetic field data by difference.

5. The CPT atomic magnetometer steering error calibration system according to claim 1, characterized in that: The angle θ between the laser direction and the magnetic field direction of the CPT atomic magnetometer probe is equal to the angle between the Z-axis of the three-axis vector fluxgate magnetometer and the magnetic field direction, and is calculated using the cosine formula of the vector angle.

6. The CPT atomic magnetometer steering error calibration system according to claim 1, characterized in that: The CPT atomic magnetometer is a total field scalar magnetic field information sensor that converts total magnetic field scalar magnetic field information into electrical signals; the three-axis vector fluxgate magnetometer is a magnetic field vector information sensor that converts total magnetic field vector information into electrical signals.

7. A method for calibrating the steering error of a CPT atomic magnetometer based on the CPT atomic magnetometer steering error calibration system described in claim 1, characterized in that... include: (1) Fix the three-axis vector fluxgate magnetometer and the CPT atomic magnetometer on the same fixture, and make the Z-axis of the three-axis vector fluxgate magnetometer parallel to the laser direction of the CPT atomic magnetometer; (2) Voltage conversion is achieved through the power supply and distribution module to power the CPT atomic magnetometer, the three-axis vector fluxgate magnetometer and the electronic control unit; (3) The scalar and vector magnetic field electrical signals are acquired through the data acquisition module and converted into digital signals and transmitted to the FPGA magnetic field calibration calculation module; (4) Obtain the CPT atomic magnetometer steering error calibration function through ground calibration test; (5) Perform the first ground calibration of the three-axis vector fluxgate magnetometer: The three-axis vector fluxgate magnetometer is calibrated in a ground environment to obtain the initial error parameters of the fluxgate; (6) The included angle θ is measured by the three-axis vector fluxgate magnetometer, and θ is substituted into the steering error calibration function to realize the steering error calibration of the CPT atomic magnetometer; (7) Perform secondary calibration of the three-axis vector fluxgate magnetometer: Use the total field data output by the CPT atomic magnetometer after calibration through the steering error to calibrate the fluxgate magnetometer. Stop the iterative calibration calculation when the difference between the non-orthogonal angles of the Z-axis calculated for the three-axis vector fluxgate magnetometer before and after the calibration is less than or equal to 0.01°, and use the parameters after this fluxgate calibration as the initial parameters for the next calibration.

8. The CPT atomic magnetometer steering error calibration method according to claim 7, characterized in that: The CPT atomic magnetometer's steering error is functionally mapped to the included angle θ; the steering error is the amplitude of the magnetic field measurement result fluctuating around the true value as the angle θ between the probe laser direction and the magnetic field direction changes.

9. The CPT atomic magnetometer steering error calibration method according to claim 7, characterized in that: The steering error calibration function is obtained by rotating the CPT atomic magnetometer probe 360° in a plane parallel to the magnetic field direction under uniform and constant magnetic field conditions, recording a set of magnetic field data at fixed angles, with the angle not exceeding 15°, and then fitting the magnetic field data by difference.

10. The CPT atomic magnetometer steering error calibration method according to claim 7, characterized in that: The angle θ between the laser direction and the magnetic field direction of the CPT atomic magnetometer probe is equal to the angle between the Z-axis of the three-axis vector fluxgate magnetometer and the magnetic field direction, and is calculated using the cosine formula of the vector angle.

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