Dynamic Tomography Of Particle Distribution In Centrifuge Based On Linear Array Electrodes

In the process of industrial material separation,the material distribution inside the centrifuge cannot be seen intuitively,which often causes the accumulation of internal materials and leads to low separation efficiency.Electrical Impedance Tomography(EIT)is an efficient,economical and non-invasive imaging method without external intervention.As a measurement tool of this technology,the traditional electrical impedance tomography system is difficult to cope with the complex working conditions of material distribution detection inside the centrifuge due to its high cost,large volume and slow imaging rate.In this thesis,the hardware improvement,logic optimization and experimental verification of the linear array electrode electrical impedance tomography system are carried out for the visual detection requirements of the material accumulation on the centrifuge wall under complex working conditions.The main work and research results of this thesis are as follows:1.Aiming at the problems of unstable current source of hardware circuit and low accuracy of acquisition voltage module,the following work is carried out:1)Improve the current source with load capacity and anti-interference ability;2)The built-in voltage is used as the reference voltage of the digital-analog acquisition chip to improve the acquisition accuracy of the system.3)The signal transmission mode of the measurement system is changed to make the signal transmission stable.Through principle verification,circuit simulation and experimental comparison,the circuit has been significantly improved and achieved the following results:The excitation current source can maintain stability and good signal-to-noise ratio from the original 300 KHz to less than 1MHz.The acquisition accuracy of the system is improved from 0.109 mV to 0.061 mV,which enhances the anti-interference ability of the signal acquisition module.The electrical impedance tomography system acquired a clutter-free excitation signal in the experiment,which verified the improvement of the circuit optimization effect.2.Logic optimization is responsible for controlling the corresponding hardware modules,processing data,and communication transmission.Through logical simulation,step-by-step debugging,and comparative verification,the following work has been completed:1)Increasing the number of digital frequency signal input makes the current frequency change more detailed;2)Debug the timing of the acquisition module to collect the noise-free voltage signal;3)The peak search operation is added to the Fourier transform to obtain the maximum voltage peak;4)The multiplexer module is compiled according to the Wenner excitation measurement strategy to make it suitable for the scene of linear array electrode measurement.5)The communication module adopts a more stable transmission serial port.After debugging,the voltage trend diagram conforming to the setting principle is collected,and the accuracy and imaging rate are compared and tested with the impedance meter(LCR)as a reference.In terms of accuracy,the data collected by the electrical impedance tomography system before and after the improvement are compared with the voltage data collected by LCR,and the data correlation is increased from 0.410 to 0.867;In terms of imaging rate,in the case of similar imaging effects,LCR needs 105 s to complete the measurement of one frame of image data,while the improved electrical impedance tomography system can obtain 2 frames of image data in 1 s,and the measurement rate is increased by 210 times.3.A centrifuge rotation experimental platform was built to test the static and dynamic detection performance of the linear array electrode electrical impedance tomography system.In the static experiment,the channel consistency of the electrical impedance tomography system and the ability of the system to distinguish the particle accumulation layer height and flow pattern are verified.In the dynamic experiment,the internal flow pattern resolution ability of the centrifuge at different speeds is realized,and the fluid simulation results are compared with the experimental reconstruction images,and the simulation results are matched with the experimental results.The electrical impedance tomography system has been improved in both hardware and logic control.The collected boundary voltage trend is consistent with the set principle trend,and the image reconstruction effect is good,which achieves the purpose of distinguishing the internal particle imaging of the centrifuge at different speeds.