Research On Embedded ECT System Based On Linux

ECT technology(Electrical Capacitance Tomography,ECT for short)is an electrical tomography based on the principle of capacitive sensitivity.ECT technology allows for the visual measurement of dielectrics in industrial pipes or enclosed vessels.A typical application of ECT technology is the real-time monitoring of multiphase flows in pipes.When the concentration and distribution of the components in the pipeline change,the dielectric constant of the multiphase fluid mixture changes,and the measured capacitance value between the plates changes accordingly.The magnitude of the capacitance reflects the concentration and distribution of the phase concentration of the multiphase flow medium,so that the distribution information of the medium in the pipeline can be obtained by measuring the capacitance between the plates.ECT technology has the advantages of simple structure,no radiation,non-intrusive,fast response and low cost.In the field and other work sites,the ECT system is required to have stable working performance,high integration,intelligence,and portability.To this end,this paper combines embedded system and ECT technology to study embedded ECT system based on Linux.The embedded ECT system designed in this paper is mainly composed of 8-electrode sensor system,projection data acquisition system and image reconstruction unit based on ARM development board.The projection data acquisition system adopts an AC excitation type C/V conversion circuit with high signal-to-noise ratio and strong anti-interference ability,and adopts a digital quadrature demodulation scheme which is not affected by the initial phase and has high execution efficiency and low resource occupation.After setting up the embedded Linux cross-compilation environment,compile and configure the Linux kernel and customize the embedded ECT-specific system.The serial communication program is designed in the embedded system to realize the communication function between the collected data and the host computer.A Qt-based human-computer interaction interface is programmed to control sensor data acquisition,normalization of capacitance data,and image reconstruction.The entire process supports touch screens.It embodies the simplicity,convenience and efficiency of the embedded system.This paper studies image reconstruction based on linear back projection algorithm.Using the multiphysics coupling software Comsol Multiphysics,the finite element model ofthe ECT sensor is established,and the sensitivity matrix required for image reconstruction and the corresponding annular flow,core flow,bubble flow and laminar flow in the two-phase flow are obtained.Projection data.Then,in the embedded image reconstruction unit,the linear back-projection algorithm is used to reconstruct the four types of images,and the ideal reconstruction effect is obtained.In this paper,the embedded ECT system is actually tested.A core stream at different locations was simulated by adding quartz sand to a hollow PVC rod.The test results show that the system has good real-time performance and can detect the position of the high dielectric constant region in the sensor in real time,which has the potential to be applied in the industrial field.The work of this paper is conducive to the promotion of portable applications of ECT technology.