Abstract
Electromagnetic tomography technology is a new process tomography technology. The aim of this study is to develop a new image reconstruction algorithm suitable to electromagnetic tomography and verify its convergence. The advantages and development of electromagnetic tomography technology and image reconstruction algorithms are introduced briefly. Based on conjugate gradient algorithm, modified conjugate gradient algorithm for Electromagnetic Tomography (EMT) is proposed. Convergence of the modified conjugate gradient algorithm is analyzed. In the light of the lab electromagnetic tomography system, modified conjugate gradient algorithm for reconstructing images is verified. By evaluation of image error and the relevance, regularization algorithm, Landweber algorithm, conjugate gradient algorithm and modified conjugate gradient algorithm are compared. It can draw the conclusion that for different flow patterns, modified conjugate gradient algorithm is superior to other algorithms in the 8 coils electromagnetic tomography lab system.
Highlights
Electromagnetic Tomography (EMT) technology is one of process tomography technology developed in the 1990s based on the principle of electromagnetic induction (Peyton et al, 1996) and is suitable for testing and to reproduce available electrical conductivity or magnetic permeability material space
Sensor array and structure parameters of the object field: For 8 coils monolayer HF EMT system, 8 coils act as the excitation coil or the detection coil alternately
Excitation signal is amplified to 10 MH 40 W sinusoidal AC signal by the preamp power driver amplifier and the last stage power amplifier and dual power supply, 27 V 8A switch power supply and 12 V 3A switch power supply, which is shown in Fig. 2 and 3 is a sectional view of the sensor array, where the space radius of the object field is R1 = 140 mm, the inner diameter of the shield layer is R2 = 165 mm and the shield outer diameter is R3 = 170 mm
Summary
Electromagnetic Tomography (EMT) technology is one of process tomography technology developed in the 1990s based on the principle of electromagnetic induction (Peyton et al, 1996) and is suitable for testing and to reproduce available electrical conductivity or magnetic permeability material space. The same with other electrical tomography technology, the EMT system is use of more incentives and multidetection measurement mode. EMT technology applied to many fields including medical field, mineral processing and separation, nondestructive testing, food processing, textiles and manufacturing industry (Korzhenevskii and Cherepenin, 1997; Korjenevsky et al, 2000). Al-Zeibak and Saunders (1993) first developed two-coil EMT hardware systems and applied to the biomedical field. Korzhenevskii and Cherepenin (1997) developed a very good two-coil EMT theoretical model and put forward the phase measurement to replace the amplitude measurement method. Yu et al (1992, 1993, 1994) developed the parallel incentive EMT system, which greatly improved the accuracy and speed of the sampling rate. Al-Zeibak and Saunders (1993) first developed two-coil EMT hardware systems and applied to the biomedical field. Korzhenevskii and Cherepenin (1997) developed a very good two-coil EMT theoretical model and put forward the phase measurement to replace the amplitude measurement method. Yu et al (1992, 1993, 1994) developed the parallel incentive EMT system, which greatly improved the accuracy and speed of the sampling rate. Scharfetter et al (2008) proposed a parallel field excitation of an adjustable excitation frequency EMT system, whose excitation frequency bandwidth is 50 kHz-1.5 MHz
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