Design Of Electrical Capacitance Tomography System Based On Industrial Bus Standard

Electrical Capacitance Tomography(ECT)is one of the electrical tomography techniques.The electrical excitation field is injected into the measured area by the sensor array.At the same time,the "projection" signal was generated by the symmetric distribution of dielectric medium,and then some image reconstruction algorithms are used to reconstruct dielectric constant distribution of the measured field.ECT technology has the advantages of non-invasiveness,no radiation,low cost,rapid response and real-time visualization.Meanwhile it has wide application prospect in industrial process online test and visual monitoring.In some multi-phase flow measurement applications,ECT technology does not has the high degree of integration and compatibility.To meet requirements of high speed,flexibility,multi-modality and compatibility for the multi-phase flow measurement,a digital ECT system based on CPCI(Compact Peripheral Component Interconnect)industrial bus standard is designed.It can realize the integrated design of the system on a 6U board and has the advantages of high speed,high precision and high stability.The ECT system is flexible with the existing industrial standard bus system.The specific research work includes:(1)A set of CPCI-based capacitance tomography imaging system is designed and implemented.The hardware system is designed to realize the measurement,demodulation and transmission of the sensor array capacitance data.The system consists of a set of integrated sinusoidal signal voltage excitation source module,multiplexing switch module,C/V conversion module,signal preprocessing and AD demodulation module,CPCI communication module.(2)An ECT real-time control method based on FPGA is designed and implemented.In order to realize the functional requirements of the hardware system,VHDL programming language is used to realize the coordination and cooperation among various modules,such as excitation module with adjustable amplitude and phase,switch drive module,AD acquisition module,digital demodulation module and CPCI communication driver module.(3)The quartz sand and plastic rod are used as the measured object and the Tikhonov regularization method is used as the image reconstruction algorithm for the static experiment of the system.The experimental results show that the ECT system has a good performance and it can be used for gas-solid two-phase flow testing.