This paper presents an approach for assembly plan generation from an assembly illustration. Previously, we have already proposed an approach for the assembly plan related information acquisition from an assembly illustration, in which auxiliary lines were taken as clues. However, some ambiguity remains in dynamic information such as assembly operations and their execution order. We have verified through experiments that the ambiguity could be made clear by referring to the feedback information from the completed assemblage after the assembly operations shown in the current illustration. But in fact, in an assembly illustration there are not only the figures of mechanical parts and the auxiliary lines for visualizing their assembly relations, but explanatory words and explanatory lines as well. Explanatory words can basically be classified into two categories: instructions on assembly operations and mechanical part names. The former explicitly describes dynamic information such as the details of assembly operations. The latter also implies dynamic information such as the function of a mechanical part. Explanatory lines are usually drawn for making clear the explanatory relations. Naturally we consider that to integrate the information from explanatory words with that already obtained through the extraction of auxiliary lines will probably enable us to generate an unambiguous assembly plan from the currently observing illustration.

A practical structural representation of a segmented image is presented. The practicalness is defined according to whether or not the representation can be directly generated from its corresponding segmented image. Two structural representations have been proposed in the literature. They are hierarchical structure and relational graph. Because they are defined totally on the basis of human perception, neither of the representations can be directly generated from the corresponding segmented image. The structural representation described in this paper, however, is based on the relations among pattern primitives and generated by applying some human-oriented constraints.