【作者】 强大壮；

【导师】 颜华；

【作者基本信息】 沈阳工业大学 ， 检测技术与自动化装置， 2012， 硕士

【摘要】 电容层析成像(Electrical Capacitance Tomography,简称ECT)技术是基于测量电容来获得电介质的介电常数分布的一种非侵入性成像技术。它利用放置在被测管道、容器周围的传感器阵列,获取被测非导电物场在不同观测角度下的投影数据,即电容测量值,用适当的图像重建算法,重建被测物场的介质(介电常数)分布。这门技术具有成本低、响应速度快、易于实现、非侵入测量方式、安全性能好、适用范围广等优点,使其具有广阔的应用前景。直接三维ECT技术,需要在被测管道上布置多层测量极板,不但测量同层极板对间的电容值,还要测量不同层极板对间的电容值,三维图像直接在图像重建过程中产生,不经过二维断层成像这一有误差的中间环节,可获得更高质量的三维重建图像。具有很大的研究价值。本文利用有限元仿真软件,进行了大量仿真实验。从直接三维ECT传感器研究和图像重建算法两个方面对电容层析成像直接三维图像重建技术进行了研究。本文提出轴向分四层,每层四个极板,相邻层之间的旋转角度分别是0°和45°的两种16极板直接三维ECT传感器结构。作者从空满管电容值、灵敏度分析和图像重建质量等方面进行比较,确定出较优的传感器结构。另外,作者提出一种用多元线性回归方法建立正问题模型,用改进的Landweber迭代算法求解逆问题的直接三维ECT图像重建算法。并与LBP算法、Landweber迭代算法进行了比较研究。结果显示,多元线性回归方法建立的ECT正问题模型模化矩阵病态更小,新算法的重建质量也优于LBP算法和Landweber迭代算法。更多还原

【Abstract】 Electrical Capacitance Tomography (ECT) is a non-destructive imaging technique that aims at visualization of the permittivity distribution of a dielectric object based on the measured capacitance. Through the appropriate image reconstruction algorithm, it seeks to reconstruct the distribution of medium (permittivity) in the measured object field using the measured capacitances, which are obtained from the sensor arrays laid on the measured pipeline or vessel. This technique has the advantages of low in cost, fast in response, easy to implement, non-invasive measurement, safety in performance and wide range in application, so it has wide application prospects.Direct 3D ECT needs to arrange multi-layer electrodes around the measured pipeline, and measures the capacitances between not only the same layer but also the different layers of electrodes. The 3D images directly generate in the image reconstruction process, not through the two-dimensional tomography with error, 3D reconstruction images of higher quality is obtained . So this technique has great research value.In this paper, finite element simulation software is used for a large number of simulation experiments. The author studies the direct 3D ECT image reconstruction technique from the direct 3D ECT sensor as well as image reconstruction algorithm. Direct 3D ECT imaging based on 16 electrodes is researched. These electrodes are arranged in four planes. Every four electrodes on each plane are rotated 0(?) or 45(?) with reference to the previous. The author compares the two sensor structures from the capacitance value of the empty and full pipe, sensitive analysis and image reconstruction quality, then determines the optimum sensor structure.Furthermore, the author presents ECT forward model established by multiple linear regression method, and also uses the improved Landweber iterative algorithm to solve the ECT inverse problem, and compares with LBP and Landweber algorithm on researching. The result shows that the forward problem model established by multiple linear regression method has lighter ill-conditioned modular matrix, and the reconstruction quality obtained by the new algorithm is better than that obtained by LBP algorithm and Landweber iterative algorithm.更多还原