Research On Image Reconstruction And Development Of Upper-Computer Software For ECT System

Electrical capacitance tomography (ECT) technique has the advantage of being non-intrusive, simple in structure, fast in response, low in cost, wide in application and good in security. It has gained considerable progress in recent years and is making for industry application.Image reconstruction algorithm research and increasing the number of projection data are two important aspects to improve the image reconstruction quality, which is just the key to this paper. At present, linear back-projection (LBP) algorithm and iterative algorithm based on Landweber are two typical algorithms. LBP algorithm has fast speed in image reconstruction and is fit for real-time image reconstruction, but its reconstruction quality is not accurate. Iterative algorithm can obtain more accurate result through modifying the image repeatedly. But more time consuming is its disadvantage. So research on the real-time and more accurate reconstruction algorithm is necessary.A new image reconstruction algorithm based on multiple linear regression (MLR) and improved singular value decomposition (SVD) is proposed. The forward model of ECT is established by MLR method and then the image reconstruction matrix is calculated using improved SVD. The simulation and experiment results show that this new method is a real-time and rather accurate image reconstruction algorithm.Increasing the number of projection data can improve image reconstruction quality, however, placing more electrodes around the pipe will produce smaller capacitances and bring detection difficulties to measuring circuit. Image reconstruction for 16-electrode sensor in combination electrodes mode is investigated in this paper. The simulation research illuminates that combined 16-electrode sensor can produce better image quality than can non-combined 8-electrode sensor, while the detection ability required for combined 16-electrode sensor is similar to that for non-combined 8-electrode sensor. So image reconstruction quality is enhanced without adding detection difficulties.The upper-computer software is developed under the environment of Object-Oriented Visual C++, which implements the functions of receiving real-time data, reconstructing images online, saving capacitance values and history review, and the like. LBP, iterative algorithm and new algorithm proposed in this paper are embedded in the software. A set of 16-electrode ECT system experiment equipment is debugged based on upper and lower computers working in parallel. This system runs well and can monitor the changes of medium distribution in the pipe continuously.