Research On On-line Calibration Method Of Geomagnetic Vector Under The Background Of Geomagnetic Matching Navigation

The geomagnetic vector on-line calibration can simultaneously calibrate the magnetic measurement errors caused by the factors of the three-axis magnetic sensor,the carrier and the environmental changes of the geomagnetic field,so as to improve the accuracy of geomagnetic vector measurement.and then improve the accuracy and success rate of geomagnetic matching navigation.For this reason,in order to solve the problems of carrier attitude limitation and slow variation of geomagnetic field when calibrating magnetic measurement errors on-line,this paper systematically studies the on-line calibration method of geomagnetic vector under the background of geomagnetic matching navigation based on optimization theory.The main contents and achievements of this paper are as follows:(1)The geomagnetic vector calibration method based on improved LM(Levenberg-Marquard,LM)algorithm is studied.With reference to the total geomagnetic field measured by the high precision proton magnetic sensor,the error of the three-axis magnetic sensor is calibrated by using the improved LM algorithm,and the misalignment error between the three-axis magnetic sensor coordinate system and the accelerometer coordinate system is calibrated by using the constraint relation that the dot product is constant under the condition that the geomagnetic field and gravity field are constant.Finally,the ridge regression algorithm is introduced to solve the morbid or singular problem of coefficient matrix when the carrier attitude is limited by the ordinary least square algorithm to solve the misalignment error parameters.(2)The on-line calibration method of geomagnetic vector under the background of geomagnetic matching navigation is studied.An on-line calibration scheme of geomagnetic vector is designed to calibrate the magnetic measurement error in the slowly varying region of the geomagnetic field and to carry out geomagnetic matching navigation in the abnormal area.Based on the comprehensive consideration of the three-axis magnetic sensor error and the carrier soft and hard iron interference error,the nonlinear least square residual function model is modified,and taking the geomagnetic field reference value stored in the navigation computer as a reference,the improved LM algorithm is used to calibrate the three-axis magnetic sensor error and the soft and hard iron interference error,and a recursive least square algorithm which meets the real-time requirement is proposed to solve the misalignment error parameters.(3)The geomagnetic vector calibration experiment is carried out.The experimental results of geomagnetic vector calibration method based on improved LM algorithm show that after error calibration,the absolute error limit of total geomagnetic field is reduced from 943.6nT to 441.0 nT,the root mean square error of total geomagnetic field is reduced from 470.9nT to 189.9 nT,and the absolute error limit of heading angle measurement is reduced from 8° to 2.5°.It shows that the high precision geomagnetic field vector in accelerometer coordinate system can be obtained on the carrier without magnetic turntable.The experimental results of the on-line calibration method of geomagnetic vector under the background of geomagnetic matching navigation show that after the magnetic measurement error calibration,the absolute error limit of the total geomagnetic field is reduced from 3755.OnT to 710.5nT,the root mean square error is reduced from 1767.7nT to 328.2nT,and the absolute error limit of heading angle is reduced from 8° to 1.9°.It shows that the high precision geomagnetic field vector in accelerometer coordinate system can be obtained online on the carrier with soft and hard iron interference.