Research On The Parameter In Semantic Feature Modeling

A successful feature modeling system, largely depends on whether it can provide a user-friendly way to specify and change feature models. The operations of specifying and changing feature models are often achieved through the parameters. It is one of the most common operations to change the values of parameters in the system. However, because allowable parameter values are not known to the user beforehand, this is often a trial-and-error process. In the process of modifying the parameters, it is likely to generate invalid geometric model or change the topology structure of the system, because the parameters selected may be inappropriate, thereby whether they can provide reasonable, effective, and can be easily operated parameters has become an issue, in addition, whether it can make use of parameters to facilitate the manipulation of free-form surface feature models is a problem need to be solved urgently.This paper presented a new method for automatically detecting the appropriate range of parameters to the general feature model. Firstly, finding distance constraints and angle constraints by analyzing the topological constraint graph, and adding these constraints to the corresponding geometric constraints, secondly, finding the critical parameter values of sub-problems through decomposition, finally, the exact parameter ranges are determined for which a solution exists, by solving one problem instance for each interval between two subsequent critical values. The determination of the scope of parameters allows the user to get a specific instruction in the course of changing the parameters, which can reduce the iterative process. About the free-form surface models, in this paper, not only the shape parameters, curve parameters, as well as related constraints are explained in detail, but also the dependency graph of feature, feature shape, interactive data structure are described in detail, further more, a new, advanced, multi-level freeform surface feature model was presented. The highest level, called the unevaluated model. The lowest level of the feature model is the evaluated model comprising the geometric model. The multi-level model defines a new intermediate level, called the partially evaluated. The latter links the features at the highest level to the geometric model at the lowest level, but also intersections between features to both their definitions at the highest level and the geometric model at the lowest level. In an interactive design environment, the designer directly interacts with a feature model, the multi-level model provides a user-friendly way in the process of specifying and changing the feature model.