| Electromagnetic tomography (EMT) is one kind of the process tomography technologies which bases on electromagnetic induction principle. It adopts external AC excitation magnetic field to sweep the space which contained the electrically conductive and magnetically permeable materials. The magnetically permeable materials form induction magnetic field and the electrically conductive materials generate electric eddy current. They modulate the original excitation field. Therefore, the spatiotemporal distributions of the electrically conductive and magnetically permeable materials in the measured field could be reconstructed by detecting the boundary magnetic induction of the researched space.The sensor of EMT system has the advantages of non-invasion, non-contact and non-hazard, and is also sensitive to both the electrically conductive and magnetically permeable materials. So it has many potential applications in industrial fields, such as mining industry processing, chemical industry processing, foreign body detection, multi-phase flow measurement, biomedical research, and geologic exploration. In present, the development of EMT technology is in the stage of applied research. Appling the EMT technology into practical production field is the object of many scientists.This paper based on the fundamentals of EMT technology, researched the model of EMT's forward and inverse problem. And the forward problem of coil excitation model was analyzed by simulation. The forward analyze results were verified by image reconstruction experiment.The main achievements made in this thesis are as followed:1. According to fundamentals of EMT technology and radon transformation principle, the theoretical mode of EMT's forward and inverse problem was studied. And the interactions between the magnetic field and conductive or ferromagnetic materials were investigated. The mathematic representation of EMT's forward and inverse problem was deduced from electromagnetic field fundamentals.2. Finite element (FEM) simulation on the coil excitation field was finished based on model of EMT's forward problem. The magnetic induction distribution of the empty field with this excitation model has been acquired. The influence of objects with different permeability, conductivity, and positions on the excitation sensing field was analyzed. And the different conditions of object distributions were analyzed by simulation method.3. The factors which influenced on image reconstruction of EMT system were investigated. And the image reconstruction simulations, which using the sensitivity based linear back projection (LBP) algorithm, have been done. Then, the image reconstruction simulation results of different object distribution conditions were acquired, and the reason that why errors generated in image reconstruction was simply analyzed. |
PDF Full Text Request