Design Of Dual-mode Ultrasonic Process Tomography System Based On Industrial Bus

UPT(Ultrasonic Process Tomography)is based on the propagation characteristics of ultrasonic waves in different fluids.Ultrasonic sensor array is used to transmit ultrasonic signals to the measured area to construct acoustic sensitive field.At the same time,the attenuation and TOFs of ultrasonic waves due to the uneven distribution of acoustic impedance are obtained.And then the image reconstruction algorithm is used to reconstruct media distribution image of the measured field.The UPT has the advantages of non intrusive,low cost,rapid response and real-time visualization.It can effectively utilize the transmission and reflection effects of ultrasonic in multiphase flow,and can accurately and comprehensively realize the visual reconstruction of phase distribution of multiphase flow and the estimation of distribution parameters.At present,ultrasonic tomography imaging systems still have problems of single-mode and low digital integration.In order to meet the requirements of high-speed,scalability and multi-mode compatibility in the field of industrial multiphase flow testing,a set of 16-channel transmission/refection dual-mode ultrasonic process tomography system is designed and implemented.And a dual-mode imaging reconstruction method is proposed.The specific research work includes:(1)A dual-mode ultrasonic tomography system based on the CPCI(Compact Peripheral Component Interconnect)industrial bus standard is designed and implemented.The system includes sensor array,standard sinusoidal voltage excitation module,multiplexed switch module,data acquisition analog front end module,digital demodulation module and CPCI data transmission module.Currently,this system could achieve data acquisition speed of 625 frames per second with an average SNR of 52 dB at the frequency of 1MHz.(2)A dual-mode UPT excitation source real-time control and demodulation method based on FPGA(Field-Programmable Gate Array)is designed and implemented.In FPGA,the voltage excitation source with adjustable amplitudeand frequency is implemented.And synchronous parallel demodulation processing and extraction of transmission amplitude attenuation data and reflection transit time data are realized by digital multiplication demodulation and first echo maximum value extraction method.(3)A transmission/reflection dual-mode fusion image reconstruction algorithm based on projection path is designed,and the dual-mode ultrasonic tomography system was experimentally tested.The system static experiments were carried out by using copper rods and PVC rods are acted as measured objects of different acoustic impedance.And the transmission-reflection dual-mode fusion image reconstruction algorithm based on projection path was applied to realize ultrasonic transmission imaging,ultrasonic reflection imaging and ultrasonic dual-mode imaging.Designed UPT system applied dual-mode algorithm improves the image reconstruction accuracy,and provides a solution for industrial process tomography problems.