Research On Optimization Of Electrical Capacitance Tomography System And Its Application

Electrical capacitance tomography (ECT), a process tomography technology based on capacitance sensors, is widely used in petroleum, metallurgy, chemical industry. Compared to the external electrode capacitance sensors, the inner electrode capacitance sensors have better linearity with materials filled in the sensitivity field and higher sensitivity. ECT system based on inner electrode capacitance sensors were analyzed in this thesis.Structure parameters such as the field angle of the capacitance sensors’plates were analyzed and optimized; imaging algorithms suitable for the inner electrode capacitance sensors were studied; ETC system based on inner electrode capacitance sensors was built in the laboratory; safety judgment method of unknown liquids was studied. The main work of this thesis is showed as follows:(1) The basic principles and the imaging algorithms of electrical capacitance tomography were studied; the positive and negative problems of ECT system as well as their influence factors were analyzed and studied.(2) Capacitance array sensors based on inner electrode capacitance sensors with fine linearity and high sensitivity were studied to substitute the external electrode capacitance sensors with bad linearity and low sensitivity. The capacitance sensors’field angles were optimized according to the condition numbers to improve the sensitivity variation parameters of the sensors; capacitance array sensors based on inner electrodes were made.(3) To overcome the present sensitivity matrixes constructing method’s time-demanding characteristic, the sensitivity matrixes were constructed based on potential distribution; the efficiency of the sensitivity matrixes’ construction was improved.(4) The image reconstruction algorithms of ECT system based on inner electrode capacitance sensors were studied; LBP, Landweber, Tikhonov algorithms’ characteristics were analyzed; LBP and Landweber algorithms based on mean filter were proposed and simulated.(5) Measurement data of liquids based on ECT technology of inner electrode capacitance array sensors were extracted and analyzed; the characteristic parameters of safe liquids and dangerous liquids were studied; judgment model based on support vector machine was built to judge the safety of liquids in bottles.(6) Experiment platform based on PCI-6221 data acquisition card of NI Company was built with software LabView 2009; data filter program, imaging algorithm, and man-machine interaction program were programmed; extracting, display, and warning of liquids’ characteristic parameter were realized to judge the liquids’ safety.High-sensitivity ECT system based on inner electrode capacitance sensors was designed and used to judge the safety of unknown liquid. The accuracies of all the judgments were greater than 96%.