Structure Modeling And Its Applications In Mechanical 3D-CAD System

A novel 3D modeling technology, named structure-modeling technology (SMT), isproposed in this dissertation, which is on the basis of the feature modeling technology(FMT). It is realized by taking advantages of generating object-oriented hierarchicalstructural feature (SF) system with mating, coupling etc. engineering constraints'characteristics in accordance with the attributes and status of the structures of themechanical devices. It supports to carry out 3D modeling in assembly and integrates partmodel with assembly model. The National High Tech R&D Program of China (863Program) supported the research with financial aids. This dissertation defines the concept of the SMT, and illustrates the principles of it howeffectively and consistently maintains the intent and semantic of a specific design.Compared with the FMT, the SMT can reflect the design intent in a higher lever by meansof acquiring and predefining the SFs existing commonly in the mechanical structures, andthus satisfy the practical requirement with them. Due to introduction to the SMT, thedisadvantages of the FMT can be prevented from generating the complicated constraintfeature model between the part model and assembly model; meanwhile the merits ofapplying the SMT can be realized, such as perfecting representation method of featuremodel, supplementing construction and representation method of geometric entity, and thenimproving design quality and efficiency. A three-element representation scheme, F(Active SF, Passive SF, EngineeringConstraints), is introduced for the structure-feature definition by means of inheriting andextending the current feature system. Therefore, an extending scheme of the SF is givenbased on the three-elements model, which consists of three tiers: basic tier, compound tierand extending tier. One way, named Macro Language Scheme (MLS), is explicated, that isused to store and manage the product feature liaison relation graph and data of the SF. Associated issues of the SF family generation and management have been discussed inthis dissertation, including creation methods for the SF library and design process model.The translation algorithm of the SF defined with MLS is developed, which resolves theproblems of calling predefined SFs from the library. Also, the dissertation discusses themanagement and maintaince strategies of the feature model based on the SMT byintroducing History Dependency Graph of Structural Feature (SDGSF). The applications of the SMT to collaborative design and computer aided assembly IIsequence planning (CAASP) have been decribed with two practical instances, and then theconcerned crucial issues of them are discussed at the same time. In order to completecollaborative design, a "PUSH" collaborative design mode is illustrated by generating theproduct layout design feature model (PLDFM) with the parametric datum in space at theconceptual design stage under the PDM system platform, which supports automaticmaintaincing and updating the part models and assembly models during redesigns causedby PLDFM modifications. In CAASP, the system can access the engineering constraintspre-defined in the SF of the design model, which can be used to generate automatically theassembly sequence liaison constraint model. It proves the SMT is suitable to CAASPsystem. In the process of software development, the author is taking charge of architecturalsystem design and the key algorithm studies. As a result, a commercial mechanical 3DCAD system, named KMCAD3D, has been developed, which has been passed the fruitappraisal by Wuhan Sci&Tech Bureau and the acceptance testing by National Software TestCenter (China) before it entered market. The feasibility and practicability of the SMT areproved by both software development and marketing promotion.