The Image Reconstruction Algorithm Research On Electrical Capacitance Tomography

Electrical Capacitance Tomography (ECT), which is based on capacitance sensingprinciple, is a promising technique of process tomography. It has the advantage ofbeing non-intrusive, low cost, facilitated installment and fast response, which canacquire 2D/3D image information of process parameters. The latest reports havemanifested the technique has a broad application for the detection and control ofindustrial process. The paper mainly discussed the image reconstruction algorithm of ECT, Thecontributions of this dissertation are as follows:(1) For understanding the nature of 'soft field' deeply and optimizing the sensor structure, the author simulate the electromagnetic properties of the sensor by utilizing the 'ANSYS' software.(2) Because the forward problem is the foundation of the algorithm, the author programmed a FEM software specially for the research on the forward problem and the image reconstruction algorithm.(3) On the basis of the optimization theory, the unconstrained conjugate gradient method was introduced. When solving the inverse problem though, where the sensitivity matrix is asymmetric, non-definite and dense, the new algorithm was derived and the excellent image was obtained.(4) For the current research, it is necessary that regularization was employed for solving the ill-posed problems. Considering the Fredholm integral equations of the first kind and its linear operator equations, the three well-posed conditions and the ill-posed finite rank operator were discussed in the metric space. some methods determining the regularized parameter were discussed by utilizing prior and posterior strategy.(5) For solving the ill-posed problem of the ECT, three computational methods such as L-curve, ordinary cross validation and general cross validation were not only proposed which is introduced for determining the regularized parameter, but also IIABSTRACT they are testimonialised each other, otherwise, L-curve method was derived in terms of mathematical theory, its filter function was devised and the method was accounted for reasonably.(6) Employing the gained regularized parameter to unconstrained image reconstruction algorithm, which was standard Tikhonov regularization, some nice image were obtained.