基于多层次表示的三维同步建模方法分析-analysis of three-dimensional synchronous modeling method based on multi-level representation.docx

针对同步建模中CAD模型约束驱动所面临的欠约束问题，提出基于虚几何的约束驱动方法，从MLR中有哪些信誉好的足球投注网站与驱动对象相关的形状与关系特征，通过这些特征到约束对象及约束的映射，借助虚元素使约束方向与约束对象定义方向（如法矢）相一致，以建立可求解的初始约束有向图；以此为基础，自驱动对象开始，沿约束传播方向依次对各结点进行自由度分析以定位欠约束结点，以最小几何拓扑变更为准则对所需约束进行几何推理，自适应地为欠约束结点增补相应虚几何约束，并通过混合约束求解，使驱动结果更为符合设计意图要求。基于上述研究，开发三维同步建模原型系统InteModel，实现产品CAD模型的快速构建、特征提取与约束驱动，以支持产品形状的重用与再设计。最后通过工程设计应用实例，验证了本文研究成果的正确性和有效性。关键词：三维同步建模，多层次表示，特征提取，约束驱动AbstractTheefficiencyofproductdesigncanbeimprovedbyreusingCADmodels.3Dsynchronoustechnologyisanimportantapproachformodelreuseandrapiddesign,whichsupportsthefeatureextractionandconstraintdrivenwithsatisfyingdesignintent.Thedesignintenthasbecomediversifiedsincetheshapeofproductismoreandmorecomplicated.Therefore,someimprovedmethodsoffeatureextractionandconstraintdrivenneedbepresentedforefficientsynchronousmodeling.Inthisdissertation,amultilevelrepresentationbased3Dsynchronousmodelingmethodisproposed.Byanalyzingdesignintentimpliedin3Dshape,themultilevelrepresentationofCADmodelsispresented.Basedonthehintsoftopologyvariation,facefeature,genericshapefeatureandshaperelationfeaturewillberecognizedtoexpresssimpledesignintent.Accordingtothehierarchyofthesefeatures,amultilevelrepresentation(MLR)ofCADmodelisintroducedusingamulti-treestructure.Inthemulti-tree,treenodescorrespondtofeatures,anddifferentcombinationsoftreenodesexpressdiversifiedcomplexdesignintent.Amethodforextractingcomplexshapefeaturesthataredifficultlydefinedbyspecificmodeispresentedbasedonheuristicshapematching.Anenhancedattributedgraph(EAG)isintroducedtoreflecttheshapeinformationofsimplefeaturesinaMLRbyenhancedattributes.TheEAGsoffeaturetemplateandtargetmodelareconstructedbyconvertingtheirMLRs.Thenthecorrespondingsub-partoftemplateisfoundoutfromtargetbygraphmatching.Duringgraphmatching,atabulistofpossibleimpropermatchesisbuilttoreducethesearchspacesothattheoptimalmatchingresultcanbeefficientlyobtained.Anddifferentenhancedattributescorrespondingtolevelsofsimplefeaturesareutilizedtoachievevariousmatchingresultssatisfyingdiversifieddesignintent.Tosolvetheund