Research On Control Strategy Of The Multi-module Shallow Surface Electromagnetic Detection System

Shallow surface is the environmental basis for people to survive.In recent years,as the number of urban infrastructure constructions increases and the importance of shallow surface resources is realized,researches on related technologies of shallow surface has attracted more and more attention.The technology of frequncy domain electromagnetic induction is adopted in this paper to detect cluttered urban underground metal pipes and unexploded explosives in the shallow ground.This paper summarizes the current development status of shallow surface detection instrument both in domestic and abroad.For the field of shallow surface detection in the frequency domain,Jilin University has developed a single-antenna five-channel detection system.On this research basis,in order to expand the detection area and improve the detection efficiency,this paper designs a multi-module electromagnetic detection system prototype.The main works of this paper are as follows:1.The design of the multi-module detection system.The modularization of detection system has great advantages for the practical application of instruments.In order to solve the problems faced by the modular system,two hardware control schemes were designed and implemented.By comparing the testing results of two schemes,a scheme which was more suitable for the multi-module detection system was adopted.2.The study on the mutual interference phenomenon of the multi-module detection system.Since the synchronization of transmitter and receiver is very important in the frequency domain electromagnetic method,the magnetic field changes during the detection of the double coil were analyzed.Comparing the primary field and the secondary turbulence filed,it was concluded that the asynchronization of the transmitter and receiver was the main cause of the mutual interference phenomenon among multiple machines.3.The design of multi-machine launch synchronization control strategy.The synchronization timing of the multi-module detection system was redesigned,and a special synchronization circuit was built on the hardware,which made the transmitting time and intensity fixed.Besides,the mutual interference noises could be reduced by reducing primary magnetic field through software processing.4.The design of multi-machine time slice control strategy.On the basis of multi-machine serial mode,comebined with retained feature of time-division launch,the industrial computer controlled the working process of each module,and parts of working process of adjacent modules on the detection timing were overlapped.As a result,the detection time could be shortened and the multi-machine launch conflict could be avoided,which greatly reduced noises and kept the same synchronization accuracy of both transmitting and receiving as the single-machine mode.5.In the laboratory environment,the functional test of single module and the phenomenon of mutual interference among multiple machines were verified.The systems under the two control schemes were tested dividedly in the field.The results demonstrated that both of the strategies could suppress the mutual interference noise.