Research On Sampling Strategy And Profile Error Evaluation Method For Sculptured Surface

With the development of modern manufacturing technology, the parts made ofsculptured surface play an important role in the fields of aerospace, automobile,shipbuilding, precision dies, etc. Processing quality of sculptured surface becomes akey factor affecting the performance of the whole system. In order to realize thequality information detection and error evaluation for the sculptured surface, theadaptive sampling method and profile error evaluation algorithm for sculpturedsurface were studied in this paper.First of all, the adaptive sampling algorithm for sculptured surface based on theCAD model was proposed. According to the decomposition order of "surface–curves-point set", the extracting algorithm of discrete theoretical points was presented,which transformed the sculptured surface into curves. Furthermore, the cubic uniformB-spline interpolation was utilized to acquire the parameter expression of each sectioncurve. The curvature measure function was defined on the basis of the curvature andthe spline mass was determined taking the curvature measure as density. A newsampling method dividing the spline mass equally was presented. And the number ofsampling points was determined adaptively based on sampling precision bycomparing the deviation between the theoretical curve and the interpolated curve fromthe sampling points. On this basis, the sampling process for surface was formulated,which realized the adaptive distribution of sampling points for surface.Secondly, the profile error evaluation method based on the adaptive immunegenetic algorithm and coordinate rotation was proposed. According to the definitionof surface profile error, a mathematical model of surface profile error evaluation wasestablished in accordance with the minimum zone requirement. For sculptured surfacewhose mathematical model was unknown, the algorithm calculating the shortestdistance from the space point to the sculptured surface was proposed based on theSTL model. Then, on the basis of the standard genetic algorithm (SGA), biologicalimmune mechanism and adaptive regulation strategy were introduced. The matchingbetween measured points set and the theoretical surface was completed with theadaptive immune genetic algorithm (AIGA), combined with coordinate alternation (CA) in the search of optimal solution in the small area near the approximated truevalue to evaluate the profile error precisely.Finally, using the MATLAB GUI module, the user interfaces of adaptivesampling algorithm and profile error evaluation method were developed. Based onVisual C++and COM technology of MATLAB, the surface sampling and errorevolution modules were integrated into the "on machine verification system forsculptured space-type surface” independently developed by Tianjin University, whichextended the error detection and evaluation functions for sculptured surface of thissystem. Meanwhile, an experiment was illustrated to invalidate the feasibility of thissystem for surface sampling and error evaluation.