Development And Application Of The Dimension Model Based On The Functional Semantics

In this dissertation, on the basis of the analysis of the dimension effect of engineering drawings, a dimension model based on functional semantics is advanced. A new scheme for constructing and adjusting the initial dimension model is put forward, meeting the dimensioning requirement of integrality and rationality.In chapter 1, the thesis discusses the meaning and current research status of automatic dimensioning. Then a three-level strategy of automatic dimensioning based on the dimension model is proposed, and the significance and feasibility of the dimension model based on functional semantics are explained.In chapter 2, the thesis discusses differences and connections between the dimension model and the dimensioning model. On the basis of the analysis of functional semantics of dimensions, a dimension model based on functional semantics is developed, and its four levels are defined in detail: shaping level of functional semantics, locating level of functional semantics, machining level of functional semantics, assembly level of functional semantics. In the shaping level, the connection between the shaping dimensions and topological structures of basic entities is set up; In the locating level, the influence of geometric elements and engineering structures on locating dimensions is expressed.In chapter 3, by identifying of geometric features of all basic entities, the shaping information of all basic entities of a part is recognized, and the carrier information for constructing dimension model is extracted. According to interrelations of all basic entities, and connections between shaping dimensions and topological structures of basic entities, a new method is presented to identify disappearing dimensions caused by interacting features. At the same time, a new strategy to create locating constraint dimensions and convert locating constraint dimensions to locating dimensions is introduced.In chapter 4, integral dimensions are added to the initial dimension model, and the necessity for adjusting the dimension model is explained. The nonlinear dimensions are decomposed into several sets of linear dimensions, and the 3D dimension chain is projected into dimension chains of three individual directions, namely, X-coordinate direction, Y-coordinate direction and Z-coordinate direction. Every individual dimension chain is checked with an improved algorithm of dimension testing, and the conflicting dimension is adjusted by the mechanism of dimension rank and the principle for adjusting the dimension model.In chapter 5, the structure of prototype is presented and some examples of the application of dimension model to automatic dimensioning are gived.In chapter 6, the work of this paper is summarized and the future research work is put forward.