Research On Detection Technology Of Underwater Ferromagnetic Target Based On Dc Superconducting Quantum Interference Device

In order to enrich the means of underwater ferromagnetic target detection and make up for the lack of sonar detection,magnetic anomaly detection,as the main way of non-acoustic detection,has been paid more and more attention by all countries.As one of the most sensitive magnetic sensors,squid can transform small magnetic field changes into measurable voltage signals,and can improve the sensitivity of magnetic anomaly detection in orders of magnitude.Low temperature DC superconducting quantum interference device(DC-SQUID)is a kind of SQUID which has the characteristics of low noise,high sensitivity and stable structure.Based on DC-SQUID,this paper studies the underwater ferromagnetic target detection technology.The innovations are as follows:Firstly,in this paper,COMSOL software is used to simulate the magnetic characteristics of submarine in the background of geomagnetic field.The distribution characteristics of magnetic anomaly signals around submarine are analyzed.By analyzing and calculating the characteristics of magnetic anomaly signals,the position,speed and other information of the submarine can be obtained.Then,on the premise that the submarine is equivalent to a magnetic dipole,single-stand positioning algorithm based on the magnetic gradient tensor signal is studied.The algorithm is proved to be reliable in MATLAB.Then,after analyzing the detection theory of the magnetic anomaly signal with DC-SQUID,the simulation of DC-SQUID is carried out in PSPICE,and its main parameter characteristics are analyzed.Then,the basic principle of the readout circuit based on the flux-locked-loop is studied,and the direct readout circuit of the DC-SQUID based on the flux-locked-loop is designed.Combined with the supporting hardware and software facilities,including DC-SQUID magnetometer,liquid helium refrigeration environment,data acquisition and recording equipment,a complete magnetic anomaly detection system based on dc-SQUID is finally built.Finally,in order to verify the detection ability of the magnetic anomaly detection system,we have carried out field test with the vehicle as the magnetic anomaly target.The test results are consistent with the COMSOL simulation results,which proves that the magnetic anomaly detection system with a single DC-SQUID magnetometer can work normally and measure the relative change of magnetic induction intensity in a certain direction.This will lay a foundation for the construction of DC-SQUID array which can measure the magnetic gradient tensor in the future.In order to verify the detection ability of the magnetic anomaly detection system,the field test is carried out with the vehicle as the magnetic anomaly target.The test results are consistent with the COMSOL simulation results.It is proved that the magnetic anomaly detection system with a single DC-SQUID magnetometer can measure the n T level magnetic anomaly signals generated by the vehicle to be tested at a distance of 40 m.This will lay a foundation for the construction of DC-SQUID array which can measure the magnetic gradient tensor in the future.Finally,this paper summarizes the main work and achievements,and prospects the next research work.