Development Of Synchronous Acquisition Technology Of Electromagnetic Signal And Attitude Full-waveform For GAFEM

The ground-airborne frequency-domain electromagnetic method is a method that emits current with a ground sourse and receives the amplitude and phase of mixed signals of primary field and secondary field in the z(vertical axis)direction in the air by the hanging coil from the unmanned aerial vehicles(UAV).However,the source in the process of practical electromagnetic detection can stimulate the earth to produce x(horizontal axis),y(longitudinal axis)and z three directions of electromagnetic fields,when uav in the air changes flight direction,speed or oscillation of the coil,the magnetic of z-component of field detection is mixed with other component of the magnetic field.This case brings the attitude error into the coil,and seriously affect the detection results.In view of this,a full waveform acquisition system of ground-airborne electromagnetic signals in frequency domain with attitude measurement function is developed.The main research contents are as follows:1.In this paper,we studied the characteristics of the magnetic field response in the ground-space frequency domain and the influence of the attitude angle,and defined the index requirements of the electromagnetic receiving and attitude measurement system.We established Two-dimensional magnetic response model.We analyzed the air of electric dipole source frequency domain electromagnetic detection method for the forward modeling.Get the instrument background noise is lower than100 nV,angle measurement accuracy pitch and roll is 0.1°,yaw is 1 °.2.We developed a low noise electromagnetic receiving system to measure the magnetic field data in the air.According to the expected performance index of receiving system,we designed a multi-channel receiving system and made man-machine interaction can be realized by writing upper computer software.3.We designed a triaxial attitude angle measurement system composed of STM32 and FPGA.The device is fixed on the receiving coil to record the storage time,pitch,roll and yaw.The design of attitude data reading software can display coil attitude and corresponding magnetic field data information.4.We tested the technical index and performance of the designed frequency domain full-waveform receiver,designed the data acquisition experiment,and verify the validity of the whole system data with the attitude measurement system.A field test was carried out in Yunnan province,and the comparison of the correction effect of the measured data proved the application value and development prospect of the system as a whole.