Research On Key Technology Of Horizontal Magnetic Gradient Measurement For Optical Pump Based On Rotor UAV

The UAV is more suitable for aeromagnetic anomaly detection of small range and high precision with its characteristics of low flying height,small volume and flexible movement,while magnetic gradient detection can restrain external interference and highlight magnetic anomaly information in a better way when compared with traditional geomagnetic total field detection.Making gradient detection with UAV can make aeromagnetic detection of small scale and high precision,which is a supplement for aeromagnetic detection of unmanned aerial vehicle,can reflect the characteristics of regional magnetic field in a better way and is of important significance for magnetic anomaly detection,unexploded exploring and antisubmarine early warning etc.This dissertation analyzes current research situation of aeromagnetic gradient measurement of UAV,designs horizontal magnetic gradient measurement system of optical pump that is suitable for multi-rotor UAV;system composed of MCU,FPGA,optical pump,INS and other modules accomplishes synchronous acquisition,display and storage of magnetic field,attitudes,coordinates and other information.According to the accuracy and consistency requirement of horizontal magnetic gradient measurement system for optical pump,it improves existing frequency measurement method,improves system sampling accuracy with adoption of phase shift and interpolation combination method under the premise of ensuring system consistency.The measurement accuracy of single channel magnetic field is 0.0014 n T.For the measurement error caused by autitude in aviation total horizontal gradient measurement,magnetic dipole anomaly model has been adopted to make simulation analysis;the measurement error caused by posture change is at 30%.Two different correction methods have been offered;it has been verified through combination of experiment and simulation that the improvement ratios of two methods can reach 3.28 and 9.68.Experiment has been made to test the magnetic interference characteristics of adopted six-rotor UAV.It has divided magnetic interference into permanent magnetic interference,high frequency interference and bias interference and proposes corresponding filter processing compensation method.Through comparing compensation processing result and geomagnetic base station data,the measurement result error after compensation is 2.27 n T.Compare gradient measurement results during flying with ground gradient experiment,the magnetic anomaly positioning error is 1.33 m.