Research On The Magnetic Target Localization By Optically Pumped Magnetometer Linear Array

With the rapid development of science and technology,the difficulties restricting the development of geomagnetic positioning technology have been overcome through one by one,and the application of geomagnetic positioning technology has gradually become a reality.Geomagnetic positioning technology is a kind of detection technology which uses the magnetic anomaly of magnetic target on the geomagnetic field to locate the target.There is a natural magnetic field in the earth.When the magnetic field generated by a magnetic object or an object magnetized by the geomagnetic field is superimposed on the geomagnetic field,the distribution of the geomagnetic field in the surrounding space will change,resulting in magnetic anomalies.By using magnetometer to measure the geomagnetic field,the magnetic anomaly information of the target can be extracted from the measured value.Through the inversion of magnetic anomaly,we can obtain the location information and magnetic moment information of magnetic target,so as to realize the target location.Geomagnetic positioning technology has great application value in energy survey,underwater pipeline positioning,unexploded ordnance detection,auxiliary navigation and other scenes.The research and application of geomagnetic positioning technology has become a hot spot in both military and civil fields.When using the total field magnetometer to locate the magnetic target,it is usually necessary to use multiple total field magnetometers to form the array.When the target is located on the water surface,the measurement array usually needs to be towed by the ship.At present,the design of total field magnetometer array is mostly cross type,H type,rectangle,which is inconvenient to use.In this study,the linear array of the optically pumped magnetometer is designed so that the magnetometer array can be towed with the ship,so as to improve the practicability of the magnetometer array.In the selection of magnetometer,the basic principles of fluxgate magnetometer,superconducting quantum magnetometer and optically pumped magnetometer are analyzed.The optically pumped magnetometer has the advantages of high precision,low noise,large range,anti-interference,no zero drift,continuous measurement,no strict calibration of attitude,etc.Therefore,the optically pumped magnetometer is selected as the array magnetometer.In the aspect of optimization algorithm,the principles of simulated annealing algorithm,genetic algorithm and particle swarm optimization algorithm are analyzed.Particle swarm optimization(PSO)has the advantages of fast searching speed,high efficiency and being able to jump out of the local optimal solution.In the design process,the main research is to reduce the impact of noise,determine the optimal aperture,and use intelligent algorithm for real-time positioning.Based on the model of magnetic dipole,this paper establishes the model of magnetic anomaly of the total field of geomagnetism,puts forward the method of reducing the influence of the change of geomagnetic field with time and space,solves the optimal aperture of the line array in the experimental environment by simulation,and puts forward the method of solving the target position by particle swarm algorithm.Then,using Python software to simulate the positioning of different arrays.The positioning results of the linear array,T-shaped array and rectangular array are compared and analyzed to preliminarily verify the feasibility of optically pumped magnetometer linear array for magnetic target positioning.Finally,draw the geomagnetic map of the experimental site,select the area where the geomagnetic field changes smoothly to carry out the experiment,design the positioning experiment of the optically pumped magnetometer linear array,and design the positioning experiment of other structured optically pumped magnetometer array as the contrast,analyze the signal-to-noise ratio of the experiment,and verify the feasibility of the optically pumped magnetometer linear array to locate the magnetic target positioning through the comparative analysis.The linear array positioning research by optically pumped magnetometer in this paper provides a reference for the following geomagnetic positioning research.