Research On Parametric Design Based On Constraints And Semantic Feature Modeling

To aim at a series of problems in parametric design and feature editing of the traditional CAD, the method of parametric design based on constraints and the idea of history-independent feature modeling are proposed through the research on the parametric design and the theory of feature modeling in developing Harbin university of secience and technology computer aided design system (HUSTCAID). At first every method of constraint solving is presented in this paper. Through comparing the advantages and disadvantages of one method with another the method of constraint solving based geometrical constraint graph in which geometrical constraint system is expressed by graph, and which can deal with over-constraints and down-constraints is proposed. Considering high efficiency and wide range of constraint solving based on number, a method of parametric design based construct point is proposed. The method combines the advantages of two type of methods and improves the efficiency of constraint solving.Feature modeling comes from solid modeling, and gets over the contradictions between geometrical operation of low levels that has no application meaning and design concept and method of high levels of the designers. In this paper the data structure of feature modeling system and the naming mechanism of topology element are presented, and the algorithms of feature designing and feature editing are proposed in HUSTCAID system. To aim at the disadvantages such as no entirety of semantic information and feature editing depending on the order of feature designing, a method that feature description graph express feature model is proposed. According to the method feature modified set is established through the law of the order of feature creating so that the complexity of reconstruct is reduced and the efficiency of feature editing is improved.