Mechanical Engineering Graphics Retrieval Technology Research

The design quality can be improved and the development speed can be accelerated obviously by applying successful design methods of similar products to the development of new product. Engineering technicians like to query design data of relevant products in the process of developing a new product, by this means, they can refer previous designing methods and experiences. Engineering drawing, the main carrier of design, producing and installation information, is one of the important technical document that used wildly in manufacturing. It is a practical problem that how the designers to retrieve design drawing of similar products from a large number of drawing files and obtain useful reference for new design.Though computer technology have be wildly used in product design currently, the information generation manner and storage form of engineering drawing are distinctly different to those of before, the problem how to retrieve required engineering drawing from drawing library still has not been solved perfectly. The technology, which is researched in context-based visual information retrieval and computer data management, gives some reference to this problem. Taking advantage of the researching production in those two fields, it is possible to achieve retrieving queried engineering drawing from many drawing files quickly.Based on analyzing the particularity of mechanical engineering drawing and previous research results, this thesis researches the correlative aspects of mechanical engineering drawing retrieval and presents corresponding resolvents.By analyzing the structure and the context of engineering drawing, this thesis ascertains the research emphasis of drawing shape retrieval is shape information. The fundamental framework of engineering drawing shapes retrieval system is presented and the ways to implement the functions of main modules are advanced as well.In order to assure the contour is complete, for some representations that may destroy the integrity of contour view, the characteristic of views are analyzed and the ways to resume incomplete contours are presented. Based on describing the data storage structure of CAD engineering drawing, an application that can extract required contour shapes from CAD drawing under AutoCAD environment was developed by ObjectARX interface function library.Based on analyzing the characteristic of the shape structure of engineering drawing, this thesis presents the methods to describe the complex contour by hierarchical structure that consist of compound shape, chain shape and simple shape. The extracting methods of three shapes put forward in above are presented. By this way, the context of complex contour shape is described by spatial combination of those three shapes.At the end of the thesis, the methods to record and organize the describing information of shapes are researched. The criterion and the math expression of similarity metric for estimating the comparability among shape are given. The strategy to retrieve similar shape bymatching description information is presented as well.This research develops the retrieval technology of engineering drawing and presents the implement methods and process of mechanical drawing retrieval which give reference to the practical application of engineering drawing retrieval.