A Calibration Method for Optimal Arrangement and Calibration of Magnetic Fields of Three-dimensional Helmholtz Coils

Abstract

The invention provides a three-dimensional Helmholtz coil magnetic field optimal arrangement and calibration method, which establishes a differential linear equation group between the output of the three-axis magnetometer and the magnetic field to be measured; the crowd search algorithm is used to optimize the condition number of the coefficient matrix function; and generate the optimal layout value of the magnetic field in turn, record the output of each three-axis magnetometer in a total of three groups of arrays after stabilization, and construct a differential equation system by making a difference with the output when the coil is not powered, and obtain the three-axis magnetic intensity The axial scale factor and the inter-axial coupling coefficient of the meter; rotate the array, record the output of each three-axis magnetometer during the two rotations, and average the two outputs to obtain the zero bias of each three-axis magnetometer . The invention can not only calibrate the axial scale factor, the inter-axial coupling coefficient and the zero offset of the three-axis magnetometer array with strong coupling between the axes, but also the algorithm is simple and fast, the calibration accuracy is high, the efficiency is high, the process is simple, and the array does not need a full attitude space Rotation eliminates the effects of zero bias and constant background magnetic field.

Description

technical field [0001] The invention belongs to the technical field of three-axis magnetometer array calibration, and in particular relates to a three-dimensional Helmholtz coil magnetic field optimal arrangement calibration method. Background technique [0002] Scalar magnetic sensors used for total field and total field gradient measurements include optical pump magnetometers, proton magnetometers, atomic magnetometers, etc., but these magnetometers are large in size, high in power consumption, and high in price, making it difficult to integrate them into an array on a large scale. The three-axis magnetometer array composed of multiple three-axis magnetometers can measure more magnetic field physical quantities and their spatial multi-point distribution, which is helpful for magnetic characteristic analysis and measurement data interpretation of magnetic bodies, and is also a One of the ways to achieve single-measurement positioning. Three-axis magnetometers such as tunne...

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Problems solved by technology

However, these estimation methods tend to fall into local extreme values ​​for the estimation of the measurement coefficients of the three-axis magnetometer with large inter-axis coupling, which affects the calibration accuracy; the geomagnetic field during calibration is a DC constant magnetic field, and the geomagnetic field calibration method is also impossible. The transfer function of the three-axis magnetometer array is calibrated, so it is necessary to use the artificial magnetic field calibration method to calibrate the transfer function of the three-axis magnetometer array

The artificial magnetic field calibration method mostly uses three-dimensional Helmholtz coils for calibration, but the existing literature seldom clearly describes its calibration theory and experiments, and only gives a rough calibration idea sporadically: first, by generating a certain space The uniform magnetic field in the interior cancels the background magnetic field to calibrate the zero bias, and then changes the three-dimensional Helmholtz coil current to generate different coil magnetic fields to calibrate other coefficients; the accuracy of this calibration method greatly depends on the effect of the three-dimensional Helmholtz coil magnetic field on the background The offset degree of the magnetic field, a large residual zero magnetic field will cause a large calibration error of the zero bias of the three-axis magnetometer, and this calibration error will affect the calibration accuracy of other coefficients through the next calibration process

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