To rapidly develop and present competitive products to the market in the manufacturing area, it is necessary to effectively utilize the cumulative technical materials such as design scheme of the existing products. For this purpose, the engineering drawings should be effectively managed and retrieved so as to quickly find the required information from a large number of existing design schemes. We develop the content-based 2D-CAD drawing/3D-CAD model retrieval system, which enables both traditional text-based management (such as file name of designs, designer and department information) and content based retrieval. With this system, a user can directly find the required design scheme by the shape of the products or components, thus the efficiency is improved and the design cost is reduced. This technology has been successfully applied in some Japanese companies.
For 2D-CAD engineering drawings, we develop a retrieval system by using the graphical elements and text elements in the drawing. Firstly, the layout of the drawing is analyzed and the graphic area and text table in the drawing are automatically extracted; Next, these two parts are processed separately, i.e., graphic descriptors are constructed by using the shape of the device components, the characters in the table are recognized. When a drawing query is input, the similar drawings are found from the drawing database by using the graphic descriptors. In case of text query, however, it is directly matches with the recognized characters. Thus, the system can retrieve the engineering drawing by the drawing and text.
For 3D-CAD model, we develop a matching method based on projected images: (1) normalize the 3D-CAD models and compute the main directions; (2) Project the model along the above main directions to get 3 pairs of images; (3) Convert 3D model comparison to 2D image pair matching. This method can realize high-speed retrieval by reducing feature dimension. For the database with 40000 models, the time for once retrieval is less than 1 s.
Yu Hao: firstname.lastname@example.org
Liu Rujie: email@example.com
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