| Geomagnetic vector contains more abundant information than total geomagnetic because geomagnetic field is vector.Geomagnetic vector measurement can significantly improve the performance of geomagnetic navigation,magnetic target detection and geological exploration when used effectively.The strapdown geomagnetic vector measurement system mainly includes a magnetic sensor,an attitude sensor and a processing unit.The magnetic sensor provides the three-component information of the magnetic field,the attitude sensor provides the attitude information of the measurement system,and the processing unit calculates the geomagnetic vector.However,the strapdown geomagnetic vector measurement system has large dynamic errors when carried on the moving platform for dynamic measurement.In view of the above problems,the thesis analyzes the dynamics errors of the geomagnetic vector measurement system from two aspects: the dynamic error of the magnetic sensor and time synchronization error between magnetic data and attitude data and research the methods to improve the dynamic measurement accuracy of geomagnetic vector.The main research work of the article is as follows:Firstly,in order to solve the problem of the three-axis magnetic sensor,the dynamic characteristic measurement system is built.The amplitude-frequency and phasefrequency response curves are obtained.And The results show that when the dynamic range of the magnetic field is 0.01-10 Hz,the measurement error of the geomagnetic vector can be up to 170 nT.The error caused by the time synchronization error to the dynamic measurement of the geomagnetic vector is evaluated by simulation.When the time synchronization error is 10 ms,the error can be up to 80 nT.Secondly,in order to compensate the dynamic error of magnetic sensors,a dynamic compensator parameter solution method based on genetic algorithm-simulated annealing algorithm hybrid optimization is proposed.The influence of the order of the dynamic compensator on the compensation effect is analyzed,and the optimal order is determined to be the second order.Different types of input signals are verified,which still has a good compensation effect.The dynamic compensation experiment of the magnetic sensor was carried out.For the sinusoidal magnetic field within 10 Hz,the maximum attenuation of the amplitude is reduced from 0.24% to 0.10%,and the error of geomagnetic vector is reduced to within 79.35 nT.Thirdly,in order to reduce the synchronization error of magnetic data and attitude data,the source of the time synchronization error in the strapdown geomagnetic vector measurement system is analyzed and a low-latency magnetic and attitude data synchronous acquisition scheme is proposed.At last,the software and hardware design of the data synchronization acquisition system is carried out,and the time synchronization error can be reduced from 9.28 ms to less than 0.4ms and the error of geomagnetic vector is reduced to within 8.33 nT.Finally,a strap-down geomagnetic vector measurement system is formed by magnetic sensor,inertial navigation module and data acquisition module.The dynamic measurement experiment of geomagnetic vector based on truss is carried out,and the jitter frequency is mainly concentrated within 6Hz.After dynamic compensation,the error standard deviation of the geomagnetic vector(north,east,and vertical)was reduced from 17.22 nT,11.09 nT,23.77 nT to 8.70 nT,6.34 nT,9.50 nT,reduced to 50.5%,57.2%,39.9% of the original;then the aviation geomagnetic vector measurement experiment is carried out.The aircraft attitude jitter frequency is mainly concentrated within 4Hz.The repeatability of airborne magnetic field line is better than 5nT,and the geomagnetic vector map in the 20 km×30 km area is drawn. |
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