This paper proposes a new framework of automatic interpretation for equipment drawings, which consist of lines, symbols, and characters, such as electric drawing distribution diagrams.
There are three stages. First stage is segmentation and recognition for primitive components. Second stage is line interpretation using probabilistic relaxation. The last stage is elimination of ambiguity using fuzzy integral.
When interpreting lines, there are two difficulties. First, symbols and characters, which are important information, cannot be recognized with complete accuracy. Second, a meaning of a line must be decided, not only by analyzing neighboring objects, but also by analyzing global relationship. Therefore, it is difficult to interpret each line in a deterministic way. In order to solve these difficulties, an interpretation problem was newly formulated for lines as a probabilistic relaxation labeling problem.
Only relaxation method has a limit to accuracy of line identification. It is difficult for the relaxation method to deal with local structures. Ambiguous labels of lines are determined by fuzzy integral based on analyzing local structural features.
An interpretation system has been developed and applied to several electric distribution diagram. Experimental results showed that over 85% of the lines were labeled correctly.