Error Analysis And Method Improvement Of Fluxgate Magnetometer Calibration Based On Zero Magnetic Environment

Magnetic field information is closely related to human life.The accurate measurement of magnetic field information is of great significance to the exploration in the fields of earth sciences,aerospace,resource exploration,life sciences,transportation and communications,national defense construction,and earthquake prediction.As a highprecision vector magnetic sensor,the three-axis fluxgate magnetometer has been widely used in various fields.However,due to the limitations of machining accuracy and electronic circuit design,the three-axis fluxgate magnetometer has its own error,which affects the improvement of its measurement accuracy.Therefore,it is necessary to calibrate its error parameters before using the flux gate to correct its display.For the traditional method of calibrating fluxgate magnetometer,due to the existence of factors such as the drift of the geomagnetic field and the interference of various ferromagnetic substances in the environment,the calibration accuracy cannot be further improved.The magnetic shielding device provides a clean magnetic field environment,and a three-axis uniform magnetic field coil is installed in the device as a standard magnetic source to calibrate the fluxgate magnetometer,which can avoid most of the magnetic field changes and magnetic field interference in the environment.The influence of the magnetometer calibration improves the calibration accuracy.However,based on the fact that the zero magnetic environment has a unique impact on the calibration accuracy of the fluxgate magnetometer calibration method,this article analyzes these specific problems and proposes corresponding improvement methods to improve the calibration accuracy.In the calibration method of the fluxgate magnetometer based on the zero-magnetic device,the calibration magnetic field modulus can be adjusted according to the needs,while the traditional error calibration model is only suitable for the calibration magnetic field of the magnitude of the earth’s magnetic field or greater than the magnitude of the earth’s magnetic field.In this paper,a nonlinear error calibration model is proposed by analyzing the error source of the fluxgate magnetometer.Compared with the traditional error calibration model,the error calibration accuracy under various levels of calibration magnetic field modulus is improved.The fluxgate magnetometer calibration method based on the zero-magnetic device needs to calibrate the three-axis uniform magnetic field coil and the fluxgate magnetometer to be calibrated successively,and there is a deviation in the position of the magnetic sensor measurement point during the two calibration processes.Also,because the uniform magnetic field coil is not absolutely uniform,the position deviation will introduce the magnetic field deviation and cause the calibration accuracy to decrease.This paper proposes a magnetic sensor measuring point positioning method based on a gradient magnetic field coil,and combines a zero magnetic device to propose a gradient magnetic field coil design method to improve the positioning accuracy,thereby improving the calibration accuracy of the fluxgate magnetometer.The magnetic shielding material of the zero magnetic device is a ferromagnetic material,which has a coupling effect with the magnetic field of the coil.Coupling will cause the magnetic field of the coil to change,and change the residual static magnetic field in the zero-magnetic device,resulting in a decrease in the calibration accuracy of the fluxgate magnetometer.This paper proposes to use a momentless coil to reduce the coupling between the magnetic field of the coil and the magnetic shielding material,and proposes an optimized design method for the momentless coil in a zero-magnetic device to improve the calibration accuracy of the fluxgate magnetometer.Through the research of each improvement method,a simulation and experiment platform is built to prove the effectiveness of each method.Combining all the improved methods,the calibration relative error of each error parameter has been reduced by more than ten times compared with that before the improvement.