Research On ECT Image Reconstruction Based On 3D Projection Data

Electrical capacitance-tomography(ECT)is a technology in which metal capacitance-plate is placed on the outer wall of the closed pipeline.The obtained capacitance is used as the projection data,and the dielectric distribution inside the pipeline is inverted through an appropriate algorithm,so as to realize the visualization of the internal information in the closed pipeline.ECT technology has the advantages of simple system structure,fast response,non-invasive,no pollution,no radiation.The research of ECT technology can be divided into two-dimensional ECT technology and three-dimensional ECT technology.At present,most of the research on ECT technology is two-dimensional.As the two-dimensional ECT sensor is only arranged outside the pipe with a measuring plate,the image obtained by it is a cross-section of the pipe.The limitation brought by the two-dimensional ECT technology leads to the inability to obtain the three-dimensional information of the distribution in the pipe.Therefore,3D ECT technology is gradually developed.Compared with the two-dimensional ECT sensor,the three-dimensional ECT sensor has more plate layers arranged outside the pipe in order to obtain more projection data.The three-dimensional ECT technology can reflect the three-dimensional media distribution information inside the pipeline through the three-dimensional projection data,and the reconstruction results are more close to the real distribution.Therefore,3D ECT technology is of great research significance.This paper focuses on the research of ECT image reconstruction based on 3D projection data.The main work of this paper is as follows:1.The effect of combined plate on 3D ECT image reconstruction quality was studied.Due to the small plate size of the 3×8 structure sensor,the measured capacitance value is relatively small.In order to increase the plate area,under the condition that other structural parameters of the control sensor remain unchanged,a pairwise longitudinal combined plate sensor model is designed.The effect of combined plate mode on 3D ECT reconstruction image quality is analyzed by comparing with traditional mode in various performance indexes.2.The influence of removing the farthest plate on the intercapacitance value on the quality of 3D ECT image reconstruction was studied.3×8 structure sensor far away from the electrode pair capacitance value is small,susceptible to noise interference.Removing the capacitance value between the farthest plates can make the imaging effect better.This paper makes a comparison between the mode of eliminating the farthest electrode pair capacitance value and the traditional mode,and analyzes the influence of eliminating the farthest electrode pair capacitance value on the imaging effect.3.Landweber algorithm is the most commonly used image reconstruction algorithm,but it generally requires a large number of iterations to obtain a better reconstructed image.Based on the homotopy perturbation method,a new iterative reconstruction formula for ECT is presented in this paper.To solve the problem that the optimal iteration times are different with different distributions,an adaptive termination condition for iteration is proposed.The effectiveness of the proposed method is verified by the reconstruction results of both the simulation data and the measured data.Compared with Landweber algorithm,the proposed method can provide better reconstruction effect.