Hardware Design Of Electrical Tomography Fusion System

The electrical tomography technology has been widely used in areas of industrial process detection and biomedical diagnosis for its advantages of radiationless,non-invasive and real-time visualization.Nowadays,the most two developed ET methods are electrical resistance tomography and electrical capacitance tomography.They are very similar in mathematical model,forward and inverse problem,and data acquisition system.In order to improve the reconstruction image quality,some researchers are trying to combine these two technologies.In Europe,led by university UMIST and LEEDS,many research institutes have studied this.But it is difficult to reflect the distribution of material at the same section because sensors are located in different sections,therefore the fusion degree is limited.However,the fusion of different excitation patterns can not only avoid this problem,but also can increase the amount of data,so as to improve the quality of reconstruction images.So this article embarks from the basic physical model of ET technology to study the measuring principles,advantages and disadvantages of eight different excitation patterns,and then completed the digital hardware system design.Main work and results are as follows:1.The different excitation patterns fusion's principle,significance and key difficulties have been studied based on the principle and main problems of electrical resistance tomography.Using COMSOL software simulation to get the electrical characteristics parameter of the hardware system and the sensitivity coefficient matrix of image reconstruction algorithm.2.A digital data acquisition system has been designed based on Xilinx Spartan-6 type FPGA chip and TI 28335 type DSP chip.System excitation signal is generated by FPGA DDS module and the D/A conversion circuit;Using digital signal processor to control the multi-channel strobe,adjust the PGA gain and communicate with PC;Data acquisition and digital phase sensitive demodulation was implemented by FPGA and A/D chip.This digital system has the advantages of flexible and extensible structure,high measurement precision and fast response speed,etc.3.This paper analyzed the key problem in the process of demodulation which causes errors and limits system speed.The phase sensitive demodulation method is redesigned based on FPGA to minimize demodulation error and improv the precision of demodulation system.Optimization of the holding-zero switching scheme is applied to improve the speed of data acquisition system.