Design Of FPGA-based ECT/ERT Dual-Modality System

Electrical Capacitance Tomography (ECT) and Electrical Resistance Tomography (ERT) are the two most developed electrical tomography methods nowadays. They have a broad developing potential in the field of multiphase flow parameters measurement, due to the advantages of low cost, rapid response, non-intrusiveness and non-radiation. ECT reconstructs the dielectric constant distribution of the measured object in the sensitive field, and ERT only reconstruct the conductivity distribution of the measured object. Actually, there are both dielectric constant distribution and conductivity distribution for multi-phase flow. Effective integration of the two kinds of system to construct a dual-modal system can broaden its scope of application of multiphase flow parameters for more information and also to improve the measurement accuracy.This paper starting from the points of real-time and digitization, designed a new type of FPGA-based dual-mode tomography system for the integration of ECT and ERT. And on this basis, its hardware and software platform were completed. This paper also finished the test and experiment of the system.The main research works are as follows:(1) Undertaken a detailed study of the principles and development of dual-modality system, and analyzed the structure and performance of intrinsic ECT/ERT single-mode system in detail. Discussed the technology bottleneck which limited real-time and imaging reconstruction precision. Based on this, the dual-modality system based on FPGA was presented.(2) On the basis of overall scheme, this paper analyzed the design schemes of each parts of the system with practical factors. The dual-modality sensor, excitation generator, measurement circuits, the array of analog switch, A/D circuit and UART module were designed.(3) Designed the data acquisition and preprocess system based on FPGA, completed its basic function, such as UART, memory management, analog switch array control, and also designed digital signal process module, which help to bring the the parallelism of FPGA into full play, improved real-time and stability of the system, realized the digitization of the dual-modality system initially.(4) Analyzed consistency problem between channels caused by parallel acquisition pattern in detail, and gave the hardware solution based on FPGA. The rate of data acquisition system could up to714.3FPS in ECT/ERT single mode or357.1FPS in dual-modal mode, far more than52.3FPS and14.6FPS of the original system.(5) The software platform was developed with Qt Creator. The software of man-machine interface was completed. A new method to refresh graphics with QGraphicsView framework was presented, and the LBP imaging reconstruction algorithm was programmed.(6) In this paper, a dual-modality ECT/ERT system was designed and established. The experimental results proved the performance of stability and repeatability of this system.(7) Relevant image experiments were complete on the system which was designed in this paper. In the static imaging experiments, the space resolution of reconstructed image could up to3%, when the air is continuous phase. In the dynamic imaging experiments, the speed of image reconstruction could up to80FPS.