A Study On Magnetic Interference Compensation Of Magnetic Anomaly Detection Platform And Hardware Implementation

When conducting aerial Magnetic Anomaly Detection(MAD), the magnetic material of the aircraft would generate magnetic interference towards optically-pumped magnetometer equipped in the tail under the effect of earth magnetic field due to the different motion state and flight direction. This would exert a serious effect on MAD. In order to satisfy the requirement of high precision, it is necessary to make some measures to offset the interference of the aircraft towards magnetometer.This thesis focused on elimination of magnetic interference based on field experiment data by the method of background magnetic field detection and software compensation. First, according to the analysis of various types of interference and characteristics in the process of flight, the appropriate mathematical model was set up.Second, coordinate system that the aircraft was regarded as its centroid was chosen as reference. The deficiencies in the mathematical model were analyzed and at the same time some proper methods were applied to diminish these deficiencies. Then, the interference factor was gotten by obtained experiment data. In the next process of detection, the interference magnetic field of the aircraft was offset according to the obtained interference factor. Thus the more accurate background magnetic field could be achieved.The precondition of magnetic compensation is to remove other noises than aircraft maneuver interference. This thesis studied the magnetic field data measured by magnetometer, designed a proper filter to filter the data and obtain the interference factor by ridge estimate and loop iteration. This method can make the magnetic compensation better. With the help of AARC510 magnetic compensation system,hardware-in-the-loop simulation experiment was conducted, which proved the accuracy and stability of compensation algorithm. The experiment result showed that under the superior magnetic field environment, the standard deviation of the mean of four directions after compensating was below 30 p T. Thus, this algorithm improved the accuracy of compensation effectively.This thesis took FPCA as core technology and designs a magnetic compensation acquisition circuit by using High Precision Oven Controlled Crystal Oscillator(OCXO),Time Measurement Chip and A/D Conversion Chip. Based on Labview, Real TimeKinematic Compensation System interface was built with the functions of data presentation, data processing and storage. A simple test of system’s accuracy was taken under experimental condition. The test results indicated that both frequency measurement and simulation voltage measurement met the requirement of the experiment. Thus, the magnetic compensation acquisition circuit could be applied to hardware-in-the-loop simulation experimentIn accordance with studying the type of the aircraft magnetic interference and correlated characteristics, this thesis elaborated fundamental principle of magnetic compensation, provides a compensation algorithm in practical term and conducted myriads of hardware-in-the-loop simulation experiment. Meanwhile, this thesis designed a magnetic compensation acquisition circuit. All this work had some guiding significance in that they made full preparation for the further experiment of real flight.