Research On ECT System To Forward Problem And Image Reconstruction Methods

Electrical capacitance tomography is studied earlier in process tomography technology. It measures the capacitance value between plate around the pipe, then according to image reconstruction algorithm to solve permittivity distribution. Due to its non-contact, good real-time, and non-pollution, making electrical capacitance tomography by its the superior of safety and economy to be used widespread at two-phase flow's visualization detection system. The successful application of ECT technique is based on solving the two problems:the effective forward problem solving methods which laid a foundation for image reconstruction. An improved image reconstruction algorithm improved the precision of image, and provided an effective way for monitoring of industrial multiphase flow system.In this paper, a large number of literatures at home and abroad are referred. Using the basic principles of ECT system, completes the study of the forward problem and the inverse problem of ECT. The project contains several tasks as follow:1. Based on the definition of ECT and the commonly used capacitance methods, using the finite difference method and gauss integral method to solve forward problem. Firstly introduced the basic principle of ECT forward problem and solving methods in common use. Then based on the basic principle of the finite difference method structuring difference formula. Combined with the theory that the potential value of pixels links with its surrounding the potential value, it will use the iterative formula and open initial value to solve potential distribution. At the same time. the gauss integral formula will be used to solve the capacitance value according to the potential value of test plate around. Finally verified by simulation experiments, the method in this paper to solve the capacitance value is superior to other methods. So it is a kind of effective forward problem solving method.2. In view of the problem that the uneven distribution of sensitivity field seriously affects the precision of the reconstruction image, to solving image transform coefficient method is proposed based on the existing sensitivity field. Firstly outlined the definition of sensitivity field and analysed the reasons of uneven distribution. Then the sensitivity matrix is solved using the existing method. It will be used to solve the image transform coefficients and applied to the iteration of image reconstruction algorithm. Finally the results of simulation experiment show that the application of image transform coefficient effectively improve the accuracy of the central region of the reconstruction image.3. In view of the existing ECT problems of reconstruction image low resolution and fuzzy boundaries, proposed an ECT image reconstruction improved algorithm. Firstly, introduced the basic principle and image reconstruction algorithm commonly used. Then the capacitance value and image transform coefficient of above is used in Landweber algorithm to obtain initial images. For it using morphological filtering method to estimate the may boundaries of original image. Finally combined with BSA to process the boundaries of the image iteration step by step, and obtain the optimal reconstruction image. The simulation results show that, comparing with the traditional algorithm, By using the method for the reconstruction of the image in this paper, error value and phase relationship value are great improved, and the boundaries of image reconstruction are clear. So it is a kind of effective and higher accuracy ECT image reconstruction method.The forward problem solving method is proposed in this paper, and the image reconstruction improved algorithm based on this, which effectively realized the solution image reconstruction of ECT system. The simulation results show that the proposed method was feasible and effectively improved the precision of ECT system imaging.