A Study on Recognition and Understanding of Mechanical Drawings : Representation and Rule-Based Understanding of Individual Projection

Abstract

An intelligent translating system which is under development extracts the CAD (Computer-Aided Design) data from mechanical drawings. The system consists of three modules: image processing, image recognition and image understanding. By scanning the geometric structure of the drawing, the image recognition module tries to identify visible lines, dimension lines, extension lines, broken lines and center lines. In the image understanding module, vector data are modeled on the chemical bond. Feature points and vectors are interpreted as atoms and molecules, respectively, and the degree of understanding is equivalent to the coupling force. The representation of the drawing is a hierarchical structure composed of end points, segments of lines, and front, side, and top views. Expert rules detect and correct errors in recognition to arrive at complete understanding.