【作者】 张红武；

【导师】 孙立镌；

【作者基本信息】 哈尔滨理工大学 ， 计算机应用技术， 2005， 硕士

【摘要】 特征造型技术是面向制造全过程的,是CAD 发展的一个重要里程碑,它使CAD/CAPP/CAM 的真正集成化成为可能,为解决产品从设计到制造的一系列问题奠定了理论和技术基础。语义特征造型是一种可以声明的造型方法,它不但能提供定义良好的特征语义的详细描述,同时能有效地维护造型过程的整个语义。事实上,语义特征造型系统一个基本思想就是在一个特征模型中把形状信息与功能信息有机地联系在一起,共同构成特征的语义。Bidarra, R. 等人研究了特征语义即特征类的详细描述并指出语义特征造型系统的最终目的是维护特征模型的有效性。特征语义的详细描述是由三部分组成的:(1)特征的参数化形状:由特征形状的元素、参数和属性构成;(2)特征的有效性条件:由各种约束,即代数约束、尺寸约束、语义约束、相互作用约束组成;(3)用户输入数据的接口:由几何约束、依附约束组成,它们用来确定该特征的方向和位置。在特征类中嵌入有效性标准使得特征具有可调整性,提供形状继承和形状组合机制,使复合特征及自定义特征能正确生成,从而提高了系统设计效率,增强了特征造型能力。特征模型有效性维护是为了保证模型中所有的特征必须符合特征类中描述的特征语义而进行的对每个造型操作的监测过程。有效性维护的两个基本原则是:(1)一个被认为是有效的造型操作应该产生一个满足所有约束的特征模型,这样才能保证模型中的每个特征都体现了那一时刻设计者的设计意图;(2)当一个无效的造型操作后,用户应该收到用于解决约束冲突的帮助。维护特征模型的有效性即特征语义的有效性是借助于使用有效性约束来进行的,这些约束是特征定义的一部分,在创建特征和随后的造型阶段,通过检查这些约束是否满足即约束之间是否发生冲突来说明该特征是否有效,而许多有效性冲突即约束冲突都是由特征相互作用引起的。因此在语义特征造型系统中,特征相互作用起着非常重要的作用,无论是特征类的描述还是特征模型的有效性维护都离不开特征相互作用。针对以上分析,本课题通过对新一代的语义特征模型的分析,参考Bidarra 等的研究成果,运用有效性标准,确立语义特征造型中相交特征识辨的方法,借助于约束解决方案,建立相交特征识辨机制的理论,维护特征更多还原

【Abstract】 Feature modeling is product-oriented and it is an important milestone of CAD development, which really makes integrated CAD/CAPP/CAM possible. It is also the theory and technological foundation of solving products problems. Semantic feature modeling is a declarative feature modeling approach that not only provides a well-defined specification of feature semantics, but also effectively maintains this semantics during the modeling process. In fact, one of the basic ideas of feature–based modeling is the ability to associate functional information to shape information in a feature model, which form the semantic of the feature together. Bidarra,R. researches feature semantics, e.g. the detailed description of feature class, and describes that validity maintenance of semantic feature models is its final aim. Feature class specification is classified into three categories: (1) specification of feature parameterized shape that encapsulates elements, parameters and natures of feature shape; (2) specification of feature validity conditions that involves a variety of constraints such as algebraic constraint, dimension constraint, semantic constraint and interaction constraint; (3) interface of user-supplied data to the feature model that determines the appropriate normal positions and orientations such as attach constraint and geometric constraint. Embedding validity criteria in each feature class makes feature adjustable, provide the mechanism of shape inheritance and shape composition in order to achieve the user-defined and compound feature. So it enhances the efficiency of designing process and improves the ability of modeling. Feature model validity maintenance is the process of monitoring each modeling operation in order to ensure that all features in feature model conform to the semantics specified in their respective classes. The basic principles of validity maintenance can be summarized as follows: (1) A modeling operation, to be considered as valid, should yield a feature model that conforms to all constraints. This ensures that every feature in the model conforms to the designer intent explicitly specified up to that moment. (2) After an invalid modeling operation, the user should be assisted in overcoming the constraint violations in order to recover model validity again. Maintaining feature model validity, e.g. feature semantic validity is by means of validity constraints that is the member in the definition of feature. At the creation of a feature and later modeling step, validity checking, whether those constraints are valid, indicates feature validity. Many validation violations, e.g. constraint violations are caused by feature interaction. So feature interactions play a major role in semantic feature modeling system, either the specification of feature class or validity maintenance of feature model. To the above analysis, this paper analysis the semantic feature modeling of new generation, consult research results of Bidarra, etc and use validity criterion, establish recognition methods of intersecting feature to semantic feature modeling. This paper bases on the solution of restriction, set up the theory of intersecting feature recognition mechanism, maintain validity of feature model, thus to make product model editing easier. Based on research results, we do further improvement and perfection to the owner-copyright industry modeling system (HUST-CAIDS) that is developed independently, make the product design of CAID meet project designer’s needs even more. CAID system faces the industrial shape-designing software system of the engineering products, it has shortened the design cycle of product development, have improved the added value of the products. Through further investigation in the aspects of subject, this paper offers a new theory and method for key technology of the semantic feature modeling and domestic CAD software development. It can make CAID software system user -oriented need for enormous economic benefits and social benefit.更多还原