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The technique of creation of drawings of mechanical parts with application of optical cad subsystem for object recognition


D. A. Roshchin

In article the system of comparison of objects with templates and a way of its application for recognition of the geometrical form of ready details at creation of working drawings is described. The system is constructed on the basis of complex components: technical methodical, software and supply with data base. Use of similar subsystems in CAD allows receiving the primary information on the geometrical form and the sizes of a probduct, and also essentially reduces time for working drawing designing. In article the detailed description of each stage of work of system, and also methodical instructions is given at a choice of scanning modes for the purpose of reception of an exact projection of investigate a test sample. Construction of the drawing of a complete product consists of following stages: Reception of a projection of investigated object, spatial orientation of an image, allocation of a contour of an image, segmentation of separate sites of a contour, contour recognition, construction of the drawing of a detail. Application of methods of digital processing of images for allocation of an image of objects on a non-uniform background is considered. The new method of segmentation of a contour of a projection of details for recognition and the description of their geometrical form is offered. Spatial orientation of an image is made by a method of the principal component analysis. The necessary information on a product is stored in a DB and contains a data set about its form, the sizes, roughness of surfaces and a material of which it is made. The information is represented in the form of drawings of the main and the additional views of a product executed full-scale and sufficient precisely to transfer the form of object. In a DB the information on a functional purpose and operational requirements shown to a product can contain. As the object identifier, its face-to-face projection is used. The two-dimensional second derivative is applied to contour allocation. In the process of detail identification there is its comparison to templates which contain in a DB. If such conformity has been established, the information for drawing creation undertakes from a DB. Otherwise the secondary data on dimensions, the geometrical form and the sizes is taken directly from a detail projection, and the specifying and missing data receives by means of various measuring apparatuses. The primary information is formed by segmentation of contours of a projection. In the beginning the external contour of a detais and then internal areas is recognized. It is supposed that the contour consists of rectilinear sections and arch-line of this sector with various radiuses of curvature. Contour recognition is made on a method of splitting and an increment of sectors of a contour. The methods applied in system of recognition, for allocation of object with use of the histogram of color scale show good results at processing of the image with strongly pronounced color component of object or a background. The system of identification of the objects, constructed with use of a method of the principal component analysis, possesses high sensitivity to deviations of the geometrical form of text sample.

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