Research On Electrical Capacitance Tomography System To Forward Problem And Image Reconstruction Medthods

Electrical Capacitance Tomography (ECT) is a new computed tomography technology, which is used by measuring the capacitance sensor array around the pipeline to calculate the dielectric material within the pipe distribution, mainly measured for industrial pipeline multiphase flow. ECT technology has been used on broad, which is non-invasive, safe and low-priced, that it can be applied for visual monitoring of multiphase flow. The successful application of ECT technique mainly depends on two aspects: First, issues surrounding the establishment of appropriate capacitance is sensitive to field matrix; Second, based on an algorithm to accurately complete the reconstruction of permittivity distribution within the pipe work.Therefore, this article analyzes the basic principles of electrical capacitance tomography,definition of forward problem and image reconstruction algorithm for improving the ideological and concrete realization. Mainly works on the following basic and innovation are as follows:1. Analysis of electrical capacitance tomography system and accordingly the basic principles of simulation. Reading lots of the literature which is based on ECT technology, summarizes the ECT principle and mathematical model. With finite element software COMSOL, that can simulate ECT systems, the establishment of a two-dimensional electric field distribution ECT system model, solution capacitance values and sensitivity field matrix, image reconstruction algorithms for the latter part of the prior information.2. The capacitance sensor has a "soft field" effect, so the output capacitor capacitance sensor and the pipeline between the internal fluid is not a linear relationship. In the traditional method, the estimated value of capacitance sensitivity field and the permittivity distribution using a linear combination of complete, so the estimated value of the capacitor with the calculated value will result in large errors. Based on this, here presents a difference by using the coupling capacitor to overcome the traditional method of compensation is estimated capacitance shortcomings. The method of coupling effect between two adjacent pixels on the basis of the compensation to establish coupling capacitance difference matrix to achieve the estimated value of the traditional capacitor compensation purposes. Finally, a simulation experiment results show that the method can improve the accuracy of capacitance estimates, which also is the problem of electrical capacitance tomography research provided a new direction. 3. Inverse problem of electrical capacitance tomography image reconstruction work is that this key part of the second study. Most image reconstruction algorithms are not high accuracy of the reconstructed image exists shortcomings. Landweber algorithm for solving ill-posed inverse problem iterative method, in the ECT image reconstruction is currently the most common application of an iterative algorithm. However, there are the traditional Landweber algorithm the problem of low accuracy of the reconstructed image. Based on this, here presents a Landweber improved algorithm, which fixed the traditional iterative Landweber algorithm factorαto optimize the algorithm with random numbers and ideas, thus avoiding the image into a local minimum, to improve the accuracy of image reconstruction . Simulation results show the effectiveness of the proposed method papers.