Reconstruction Algorithm And Experimental Research Of Thermal Insulation Defect Detection Based On Planar Capacitance Imaging

The thermal protection on the surface of the spacecraft plays an important role in the safe operation of the aircraft.At present,adhesive is usually used to bond the thermal insulation material to the aircraft’s substrate,in order to reduce the damage of aircraft caused by a large amount of heat generated by the friction between the aircraft shell and the atmosphere.If the bonding quality of insulation material is poor,it can easily lead to the destruction of thermal protection structures during flight task,casing loss to the unpredictable.In order to solve the above-mentioned security risks,the design and implementation of defect detection for porous thermal insulation materials based on Electrical Capacitance Tomography(ECT)technology is studied.Mainly from the following aspects:First of all,through the research on non-destructive testing technology of composite materials,and analyzing the principle of detecting the adhesion defect of thermal insulation materials,a method based on planar array ECT technology is developed.Analyze the mathematical description of ECT and study the positive and negative aspects of ECT technology.In addition,a complete set of planar array capacitance tomography detection system is built for the plane structure characteristics of aerospace thermal insulation materials.The hardware foundation is provided for the subsequent completion of bond defect detection.Secondly,considering the problem of unstable capacitance data,small order of magnitude and susceptible to the detection environment,a planar array capacitance imaging algorithm based on FCM algorithm optimization is proposed.By sampling and convergence of the capacitance values,the algorithm makes the distribution of capacitance values closer to the real location of the target,it not only retains the effective capacitance change due to the presence of defects,but also reduces the error interference caused by the external detection environment to the measured capacitance value,making the capacitance data more stable and accurate.The optimized imaging algorithm is applied to two common defect samples at last,simulation experiments were performed to verify the superiority of the proposed algorithm.Finally,by analyzing the ECT principle and the traditional image reconstruction algorithm to reconstruct the shortcomings of low image resolution,a planar array capacitance imaging algorithm based on Kalman filter is proposed.Apply Kalman filter for linear minimum variance estimation to image reconstruction.Combined with the imaging principle of ECT,the mathematical model of ECT based on Kalman filter is established,which continuously approximates the real value by continuous measurement and constant estimation,provides a new approach for image reconstruction algorithm.And by reducing the dependence on the initial value of the iteration,the quality of image reconstruction and the imaging precision are further enhanced.