Research And Development Of System For Comparison Inspection Algorithm Between ICT Images&CAD Model

Work-pieces’ manufacture error analysis is an important part evaluation for theirmanufacturing process. Several digital measuring equipment provide conditions formanufacturing error analysis and become the main method of evaluation formanufacturing precision. Industrial computed tomography (CT) technology is anadvanced nondestructive inspection technology. This paper developed a3D comparisonsoftware system (Match_ICT), which was based on industrial CT images and CADmodel. This system realized the comparison using the registration technology, thenrealized the work-pieces’ manufacture error analysis.In order to realize comparison, we need to extract the feature sets of two modelsfirst. In this paper, CAD models used the STL format; we quantized the STL model toget the CAD point sets, as for the industrial CT images,3D edge surface and3D cornerswere extracted to be the feature sets.The registration method of this paper was divided into two phases: roughregistration and precise registration. Rough registration make the deviation of positionbetween the CT data model and CAD model smaller; Precise registration make thembeing in the best fitting state.In the process of rough registration, the oriented bounding boxes (OBB) of twomodels were calculated using the rotating projection method presented in this paper.The rotation matrix R and translation matrix T of the rough registration were calculatedby the two OBBs. Through rough registration, the deviation of position between twomodels had been smaller, so rough registration solved two problems when the preciseregistration was preceded directly: the low convergence speed, falling into the localconvergence easily. The OBB of CT calculated using corner sets, accelerated thecalculation speed obviously.In the process of the precise registration, we used SVD-ICP algorithm. First of all,CT corner sets and CAD point sets were registered by the SVD-ICP algorithm, reducingthe deviation of position further, and then used the CT edge sets and CAD point sets toregister using the algorithm of the SVD-ICP. It improved the efficiency of theregistration.We calculated manufacture error between every point of the CT edge sets and thetriangles after rough and precise registration process. And then the error distribution was displayed by three methods: gray cloud display, color cloud display and range errordisplay, realizing the analysis of manufacture error.Finally, the proposed algorithms were integrated to the software. And, to improvethe practicality, this software system realized several interactive operation functionssuch as rotation, translation, zoom, scaling, and so on.