Research On Measuring Method Of Adhesive Thickness Of Solid Propellant Grain Surface By The Grating Projection

Solid propellant grain’s surface coating a liner, and the quality of the adhesion betweengrain and liner has directly affects on the solid propellant’s emission properties, while theadhesive thickness is one of the major factors to affect the quality of the adhesion betweengrain and liner. Therefore, study an automatic detection of the adhesive thickness bynon-contact method is significantly important for ensuring the performance of solid propellantgrain.Grating projection method is a method for3D profile reconstruction by using structurelight, we extend this method to the thickness measurement, and the solid propellant grainsurface’s adhesive thickness measurement with grating projection method is presented.The detection principle of the3D profile reconstruction with grating projection method isintroduced, and the feasibility of the thickness measurement method for solid propellant grainsurface’s adhesive is verified. According to the requirements of measurement principle andfield environment, the optical structure based on triangle method is designed, which ensureshigh-precision and high-stability of the detection system.The research highlighted processing of the digital fringe images by Fourier transformprofilometry method(FTP), and improved the traditional method for making the imageprocessing algorithm to better meet the requirement of the measurement system, such as thenonlinear correction of fringe by the least square curve fitting method, the spectrum analysisof fringe image by Gabor transform, the extraction of fundamental frequency by the flattenedgauss filter,and a new height-calibrating method is applied in the height calculation of solidpropellant grain.The detection system is stable working during the simulation experiments, and thesemeasurement results are close to the standard value, the maximum error is less than0.02mm,and shows that the system has better repeatability and consistency. Meanwhile,the detection system can measure the adhesive thickness of solid propellant grain with different sizes, andindicates its universality.