Research On Constraint Solving Of Semantic Feature Modeling Systems

In recent years, the structure of CAD software is undertaking significant reforms, changing from solid modeling centered systems which are called "geometric CAD" to the feature and constraint based ones, which are called "applied CAD". As an indispensable part in any CAD systems, technology concerning constraint modeling is highly emphasized, and many useful solutions have been raised which encourage the reform and application of CAD systems. At the same time, the new concept and arithmetic of semantic feature is applied to define feature, where the feature can be adjusted, which improves the efficiency of designing process. So, the semantic feature modeling technique has become very important in most CAID systems.HUST-CAID (Computer Aided Industry Design System developed by Harbin University of Science and Technology) is a parametric modeling design system based on feature. This system describes entities based on mixed model of boundary representation,CSG tree and feature description tree(FDT),in which the design of solid model and feature-editing can be completed with rebuilding CSG tree and feature description tree. But, in the feature modeling, with the number of features increasing, the design model becomes more and more complex. The efficiency of designing is decreased.In order to maintain the intent of designers and satisfy them, the concept of the semantic feature modeling is put forward based on old design system. At the same time, in order to settle the problem that over- and underconstrained models is difficult to solve, on the base of researching all kinds of existing constraint-solving mechanism and old constraint solver of HUST-CAID systems, a new freedom analysis technique is presented, and is elementarily applied to constraint modeling of HUST-CAID systems.