Modeling And Simulation Of Projection And Reconstruction Image For Small Module Gears In Industrial CT

As one kind of the key parts,small module gears are widely used in precision reducers in CNC machine tools and robots,aviation instruments,automotive electronics,semiconductor manufacturing equipment,medical instruments,office equipment,etc.Small module gears have the characteristics of small size and small cogging gap,especially small module plastic gears have lower strength and are easy to occur deformations,and it is difficult to use contact measurement methods to obtain the dimensions and accuracy of the gears.Computed tomography(CT)technology is first used in the medical field,which is an image reconstruction technology based on the ray attenuation mechanism combined with the computer.CT technology is called industrial CT technology when it is applied in the industrial field,and it has been widely used in automobiles and railways,aerospace,military defense,materials and other fields.As a non-contact measurement method,industrial CT technology can detect internal defects,structures,geometric dimensions and precision features of complex components.However,at the same time,the industrial CT machine has a complex structure,and there are many error sources in the measurement process of acquiring the projection image.So,it is difficult to analyze and evaluate the measurement uncertainty of CT.For the application of gear measurement on industrial CT and the evaluation of system measurement uncertainty,it is necessary to establish a virtual CT projection image and a mathematical model of the reconstructed image of the measured gear with given parameters.This dissertation researched on the mathematical model and simulation analysis of the projected image and reconstructed image for the small module spur involute cylindrical gears.This dissertation mainly completes the following contents:(1)The mathematical model of projection image and reconstruction image in industrial CT for small module gears is established,the gear end section is divided according to radial distance,the mathematical model of projection value of each part is established in turn,and then the end section projection model is obtained by the combination.(2)The projection image and image for small module gears in industrial CT is simulated by MATLAB.The projection value of the gear end section at different rotation angles are obtained by MATLAB simulation,and the data of projection value in one rotation cycle is combined to be a grayscale image of the projection image.Based on the grayscale image of the projection image,the reconstruction image of the gear end section is obtained,which is binarized to get the gear end section data.(3)The projection value with the same parameter gear in industrial CT is virtually measured in Geant4,and the projection value obtained by MATLAB simulation is compared with the Geant4 virtual measurement,which verifies the accuracy of the mathematical model proposed in this dissertation.(4)Reconstruction image data of the mathematical model by the MATLAB is compared with the standard gear data to further verify the accuracy of the mathematical model,the involute curve part of the reconstruction image is fitted to improve the accuracy.