| Geomagnetic positioning and navigation has the advantages of low price and stability,and it can still work normally in case of underground or indoor disasters.The variation law of geomagnetic disturbance of underground engineering space point is one of the basic research of geomagnetic emergency positioning.In order to study the disturbance law of spatial point magnetic field value caused by dynamic interference sources in the environment,indoor corridor,outdoor open space and underground horizontal roadway are selected as research areas for experimental study.During the test,fvm-400 magnetometer was selected to collect appropriate magnetic field data in several zonal research areas,and the geomagnetic reference map was established and the magnetic field distribution characteristics of the study area were analyzed.Through the experimental study,the disturbance law of personnel walking,car,transport vehicle,elevator and lifting cage on the monitoring point is analyzed.It is found that these disturbance sources will produce a certain degree of magnetic interference to the nearby points,and all of them belong to instantaneous random magnetic disturbance,but the noise levels are different.When the distance from the monitoring point is nearest,the personnel walking,car,transport vehicle passing,lifting and lowering power are found The results show that the magnetic disturbance generated by the ladder and the lifting cage is about 10 n T,1000 n T,1000 n T,14000 n T and 1000 n T respectively,the disturbance distance is about 2m,35 m,4m,13 m,6m,and the instantaneous disturbance time is about 1 ? 2s,5s,10 s,5s,5s.In order to reduce the interference of these dynamic disturbance sources on the geomagnetic field,the mean filtering,wavelet smoothing and dynamic frequency limiting weighted algorithm are used to denoise the measured magnetic data.It is found that the three denoising algorithms are improved after denoising,but the dynamic frequency limiting weighted algorithm is closer to the true value,less volatility and better stability.In order to verify the accuracy of geomagnetic matching after denoising,referring to the law of noise generated by these dynamic disturbance sources,noise of about 10 n T,1000 n T and 13000 n T are added into 2 ? 3 points of the sequence to be matched.The matching simulation experiment is carried out in the underground horizontal roadway by using MSD and particle swarm optimization algorithm.The simulation results show that when the noise of about 10 n T is added,the matching results before and after smoothing are basically unchanged,and when adding about 10 n T The results show that the matching accuracy of MSD algorithm is significantly lower than that of PSO algorithm when the noise is 1 000 n T or 13 000 n T;the matching probability of the optimized particle swarm optimization is 60? 70% before smoothing;the matching accuracy of MSD algorithm is higher than that of PSO algorithm after smoothing by dynamic frequency limiting weighted filtering,in which the matching probability of MSD algorithm is close to 100%,and that of PSO algorithm is more than 90%.The experimental results show that the instantaneous magnetic disturbance produced by some dynamic interference sources will affect the accuracy of geomagnetic data acquisition,and even lead to virtual positioning.In order to improve the accuracy of underground geomagnetic matching,it is necessary to carry out the research on dynamic interference source,denoising algorithm and particle swarm optimization algorithm.Figure 41;Table 16;Reference 59... |
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