Research On Design And Optimization Of Planar Capacitive Sensors For Defect Detection Of Non-metallic Materials

As a new type of non-destructive testing method,planar array electrical capacitance tomography technology has attracted much attention.It has the advantages of rapid response,low cost,and non-invasiveness.It mainly relies on the planar array capacitance to obtain the change of relative permittivity caused by the measured object,and then the changed capacitance value is measured and sent to the PC terminal for imaging processing.Planar array electrical capacitance tomography started late.Although it is developing rapidly,the current imaging effect is not satisfied.Misjudgments,missed judgments,blurred edges of the measured object,and cluttered backgrounds often appear in the imaging results.Therefore,this article conducts in-depth research for the purpose of innovation of measurement methods and optimization of planar array structure.First of all,we propose a measurement method that uses the original capacitance value to directly reflect the dimensional information of the measured object.This can solve the problem that the existing planar array capacitance imaging process is complicated and introduces too much interference to results.In this method,based on a pair of electrodes,the capacitance data is obtained by sweeping measurement.After the capacitance data is normalized,the concept of special points is introduced to directly reflect the side length of the measured object.In addition,the factors that affect the measurement of this method,such as the moving step length,electrode width,and electrode gap width,are studied and corresponding conclusions are drawn.Secondly,in order to meet the requirements of visualization of measurement results,a method of using a differential shielding structure to replace the original interelectrode shielding structure in array capacitive sensor is proposed.This way can solve the problems of the existing 12-electrode planar array imaging results with clutter and poor image quality.After simulating the new planar shielding structure,it is concluded that in planar array electrical capacitance tomography,the differential shielding electrode can replace the original inter-electrode shielding electrode structure.And the data is more stable and the image quality is more stable after using the differential shielding electrode structure.Finally,in order to further optimize the imaging effect of the planar array electrode sensor using the differential shielding electrode structure,it is proposed to apply the Orthogonal Matching Pursuit to reconstruct the image.The Orthogonal Matching Pursuit has never been used in planar array electrical capacitance tomography.