The design capture system : capturing back-of-the-envelope sketches

• Main Author: Hwang, Teng-shang
• Other Authors: Ullman, David G.
• Language: en_US
• Published: 2013
• Subjects: Computer-aided design; Engineering design > Data processing; Engineering design > Computer programs; CAD/CAM systems
• Online Access: http://hdl.handle.net/1957/37152

A system which allows the computer to capture sketches made by a mechanical designer is described. The system not only recognizes basic features as they are sketched, but it also reasons the spatial relationships between features and builds a high level abstract representation (feature model) of the artifact. The temporal nature of the capture, one feature at a time, serves to form a feature graph that allows for parametric design. The system is composed of three subsystems: a two-dimensional freehand sketching subsystem¹ , a three-dimensional features recognition subsystem, and a spatial reasoning subsystem. The freehand sketching subsystem takes the user's input sketching actions and interprets them as simple, two-dimensional geometric elements, such as line segments, circles, and ellipses, etc. The features recognition subsystem interprets the collection of two-dimensional geometric elements to extract three-dimensional information from them and creates high level abstract representations, features. The spatial reasoning subsystem finds relationships between a new feature and existing features and integrates features to form a single part. The work of the Design Capture System is aimed at capturing sketches of a specific application domain: injected molding plastic parts. Twenty injected molding plastic parts were collected and analyzed to understand the distribution of features. Isometric sketching is selected as the basic constructing method for the system. The processes of freehand sketching and computer-aided drafting were studied to find a better scheme for computer-aided sketching. Conclusions are also presented. ¹The Freehand Sketching Subsystem was accomplished by Roger Fang as a Master project in 1987 at the Department of Mechanical Engineering, Oregon State University, Corvallis, Oregon. === Graduation date: 1991