Simulation Research On ACFM Signal Detection

Currently, the items identification technology, mainly represented by the bar codetechnology, radio frequency identification technology is widely used in production, sale,storage, logistics, security, and other fields. However, the traditional items recognitiontechnology has many problems: it is easy to damage; the paper bar code is easy to becontaminated; high price for radio frequency identification, and many other problems.Moreover, it is hard for the items recognition technology to operate under the heavyenvironment for the long-term, e.g.underwater, underground, space. This thesis involvesin the corresponding research of laboratory project " based on electromagnetic detectiontechnology the metal label information extraction key technology research", for thefurther research in metal tag detection technology.For the detection of metal tag, this thesis adopts the ac electromagnetic fielddetection technology (ACFM). As a new type of nondestructive electromagnetic testingtechnology, ac electromagnetic field detection technology can determine the crack size,conduct the non-contact and non-calibration detection, free from the lift-off effect,material properties and the edge effect, which is also widely used in the various kinds ofdefect detection in such occasions as underwater structure, the underground pipeline,aerospace, and etc. The detection sensor based on ac electromagnetic field detectiontechnology can be used underwater, underground, space.Based on the analysis of the ac induction electromagnetic detection principle, thisthesis applies electromagnetic simulating software ANSYS to establish the finiteelement three-dimensional numerical simulating model, including the incentivesimulating model, the calculating model and metal tag simulating model. Calculationmodel mainly analyses the distribution rule of the induction electromagnetic field inthe metal surface, which also provides the theoretical basis for the calculating modeland metal tag simulating model; Calculation model is mainly used to calculateinformation in the defect magnetic field and accurately simulates electromagneticdisturbance near defects; Metal tag simulation model is mainly responsible for theanalysis of the induction electromagnetic field distribution in the metal surface arrangedin two-dimensional.The traditional goods identification tag, such as product labels, bar code labels,and the widely used wireless radio frequency identification (RFID) tags, exist suchproblems as single recognition symbol and shape, low information density, andnon-automatic identification. Based on the study of the existing label identify shape andarrangement, the tag identification symbols were improved, in which the symbol shapeapplies many kinds of in-erratic graphics (e.g. bar, round, square), and array two-dimensionally before the simulation research by the ac magnetic field detectiontechnology.By solving the space electromagnetic field distribution, metal tag simulationmodel can determine the magnetic field distribution in different pattern, differentgeometric parameters (width, depth, length, etc.) and different metal materials. Bystudying the quantitative relationship between the distribution and main influentialfactors of, this thesis try to establish the optimal coding scheme.