Optimal Design of Excitation Coil for Transient Electromagnetic Detection Based on Incident Field

To meet the needs of underground metal target detection in modern urban construction, in view of the problem that a single exciting coil in the incident field diverts in space and has poor focusing ability, based on the principle of spatial magnetic field vector superposition, the topology structure of conical focusing coil array is constructed, the analytical model of focusing magnetic field of the coil array is established, and the influence of each structural parameter of the coil array on focusing characteristics is analyzed. An improved particle swarm optimization algorithm based on simulated annealing (SA-IPSO) was designed to solve the optimal solution of coil structure parameters, and a transient electromagnetic (TEM) detection exciting coil array structure with more concentrated magnetic field intensity distribution and better-focusing performance was formed. Experiments have shown that under the optimal parameter solution of the array coil structure, 60% of the high magnetic field energy is concentrated in the magnetic focusing area with a radius of 30 cm, and the maximum magnetic field intensity is $1.1\times 10^{-{4}}$ T. Compared with the unoptimized results, the magnetic field strength has increased by 10%, and the magnetic field focusing range has been reduced by 25%. The excellent focusing effect of the focusing coil array structure has a certain reference value for coil optimization design in TEM detection.