Research And Practice Of Dynamic Management Of Geometry Constraint In 2D Parametric Design

Parametric design technology has become more and more important now. Modeling, management and solving of geometry constraint system are the key technologies in this field. But how to maintain the constraint conveniently and effectively had not been achieved well, so it is vital to manage the constraint dynamically in the design procedure. In this thesis the reduction strategy of geometry constraint in parametric design is researched from the dynamic management point of view. On the basis of using graph to describe the geometry constraint, the author expresses the virtual-base technology, and discusses how to check the constraint consistence. Firstly,in accordance with the oriented-object method and the performance of AutoCAD platform, the author analyses the demands of host platform characteristic for geometry constraints during the process of parametric design, and then constructs the calculating model for the dynamic management of geometry constraint system. This model can be implemented on other systems. Secondly,on the foundation of the above model and AutoCAD platform, the author pays much attention to the problem of dynamic management and permanent object storage, and finally builds the dynamic calculating model of geometry constraint. At the same time, the author discusses how to maintain pure complete geometric system and compound complete geometric constraint system under different circumstances. Thirdly,under the condition of maintaining the geometry constraint graph, the author researches how to show, add, delete and modify constraint to geometry constraint system, including the Undo/Redo mechanism. Finally,based on the research above, the author accomplishes a 2D parametric design system with the help of oriented-object thinking to support full-constraint CAD system. This module shows the thinking of dynamic management well.