The Research Of Unexploded Ordnance Detection With Portable Transient Electromagnetic System

Unexploded ordnance refers to bombs and mines that have not been detonated during the war and still have explosive and biochemical hazards.These ammunitions threaten the production and life of mankind.In response to this phenomenon,researchers have developed a variety of geophysical methods for unexploded ordnance detection.Among them,the transient electromagnetic method has the advantages of strong anti-interference performance and strong target recognition ability and has been widely used.This paper is based on the portable transient electromagnetic detection system to carry out the response forward and inverse calculations and actual measurement analysis of the unexploded projectile under the three-dimensional dipole model.First of all,the laboratory self-made portable single-transmit and five-receive detection system is introduced to introduce the sensor and system structure,and the lateral line and plane detection modes are given;the principle of system transient superposition and channel superposition is described in detail,and a high signal-to-noise ratio signal is obtained.;The sideline response analysis of 122 mm grenade and 130 mm mortar shells shows that the detection depth of the system is about 1.5 m when the superposition time is 64 s;Secondly,a three-dimensional single dipole model of the unexploded projectile is established,and the transient electromagnetic response of the unexploded projectile is equivalent to the transient electromagnetic response of the dipole,and then the primary and secondary field response expressions of the unexploded projectile are calculated;The plane test of the 82 mm mortar shell was carried out,and the time domain response,lateral response and plane response of the unexploded shell were obtained,and the derivation of the unexploded shell forward model was completed;Then,the differential evolution algorithm and its parameter settings are introduced in detail.A two-step unexploded ordnance response inversion method is obtained through matrix transformation,that is,the unexploded ordnance position parameters are inverted first,and then the unexploded ordnance characteristic response parameters are inverted.Through the inversion analysis of the measured response of the 82 mm mortar shell,the differential evolution algorithm can invert the unexploded ordnance parameters accurately and quickly,and establish an unexploded ordnance inversion model;Finally,9 types of unexploded bombs and 4 types of unexploded bomb analogues of different types are measured on the plane response and the position and characteristic response inversion are carried out.The test results show that the differential evolution algorithm can invert the unexploded ordnance position response very well,the error is not more than 6 cm,and the characteristic response inversion result is consistent with the actual;in the 5×5 m large-area field detection,the system can capture all targets.The body responds and achieves a successful capture,and the single-point position inversion error is within 14 cm.