Research On Key Techniques Of Fixture Intelligent Design Based On Knowledge Reuse

Fixture design is the key link between design and manufacture of product, whichdirectly affects the product’s manufacturing quality and development cycle. Fixture designprocess is a course of accumulation, transformation, reuse on experience and knowledge.To lack of reasonable knowledge representation, acquisition method and effectiveknowledge reuse mechanism of the present digital fixture design process, design knowledgecannot offer an effective support for digital fixture’s intelligent design. Especially in theaviation manufacturing field, efficiency and quality of fixture design is still a bottleneck inrapid response manufacturing. Efficient reuse of fixture design resources and knowledge isa crucial means for realizing digitalization and Intelligence of fixture design. This is themajor research question in lean research and development of product.For fixture intelligent design requirements of3D design and manufacturing integrationenvironment, the paper regards the various stage tasks as the object of study. Theprocedures and features of knowledge reuse in fixture design domain are analyzed, and thekey technologies of fixture intelligent design based on knowledge reuse are studied. thispaper gives a further discussion from the perspective of theory and method on knowledgemodeling of fixture design domain, intelligent setup planning, case-based fixture designand optimization, intelligent design of fixture structure, and so on. In accordance withfixture design process of aircraft structure part, the feasibility and effeetiveness of thetheoretical study is verified.The achievements and innovation of this research are asfollows:（1）Rearsch on knowledge reuse mode of digitized fixture planning and design. Forthe design knowledge cannot effectively support fixture digital planning and design, Amode of fixture intelligent design based on bidirectional task-knowledge driver is proposed.A framework of knowledge reuse of the fixture intelligent design is established, whichintegrates setup planning, fixture planning and fixture structure design. By analyzing theknowledge requirements of fixture planning and design, modeling method of fixturedesign task are build by using CommonKADS method. Knowledge model in fixture designdomain is structured based on domain’s ontology and MOKA method. Meanwhileknowledge model map of setup planning, fixture design and fixture structure design is realized in the fixture design domain.（2）Research on intelligent setup planning supported by knowledge. According tosetup planning of part and manufacturing resources allocation, connotation and the keyinfluencing factors of setup planning are studied. Intelligent setup planning method basedon knowledge reasoning and Memetic algorithm is proposed. Manufacturing feature isdivided into the smallest processing unit, which dispose setup features based on processingcapacity of manufacturing resources. Then, process rules based on tolerance relationshipare built and used to build order constraint relation of processing unit. The sum of the setupattributes similarity between processing units is taken as fitness function of memeticalgorithm, setup schemes are searched in the global scope by partial mapped crossover andinsertion mutation. Based on sequence constraints between units, binary tree sort algorithmis adopted to transform from infeasible solution to feasible solution. Setup scheme of highfitness can be acquired in local search by crossover operation based on fitness rate andmutation operation of no-sequential constraint processing units. After the evolution ofpopulations, optimal setup scheme is generated.（3）Study of digital fixture planning and layout optimization technology. In view ofhow to efficiently reuse fixture case and layout optimization problem of fixture planning, amethod based on fixture planning reuse by semantic and layout optimization is proposed.Semantic information of fixture case is used to describe the knowledge of fixture planningand semantic annotation of existed fixture case is constructed. By studying similaritycalculation methods of semantic information, the two levels similarity evaluation approachof fixture case ontology is proposed to resolve the problem of similarity measurement offixture cases. The similar fixture case will be mapped into the target fixture planning design,which can reuse fixture manners and features of the existed fixture design case. Focus ondeformation of thin-walled parts, the optimizing model of fixture layout and clampingforces simultaneously is developed with objective of reducing machining deformation. Theoptimization of fixture layout is achieved based on particle swarm algorithm and finiteelement method. And proper fixture planning is acquired. Effective reuse of fixture designcase and optimization of fixture layout are realized.（4）Research on fixture structure intelligent design. For the heterogeneity and diversity of knowledge in fixture structure design, an intelligent design method based onknowledge components model is proposed. The model of fixture units is constructed, whichintegrates parameters, rules, solid models and assembly knowledge of fixture units. Basedon fixture element identification and knowledge components model, the key parameters offixture components is determined. The related specifications and all specific parameters offixture units are obtained by key parameter. Solid models are automatically created byparameter of knowledge components model of fixture units. Based on assemblyinformation of the model, the assembly relation among fixture units, fixture componentsand work-piece is automatically built. Fixture design knowledge can support the fixturestructure’s intelligent design seamlessly and rapidly.（5）According to above key technologies, prototype system of fixture intelligentdesign based on knowledge reuse is designed and developed by combining CAA withCATIA, which is oriented to fixture design process of product. The overall architecture ofthe prototype system is introduced, and main function modules and their application ofprototype system are described. To design process of frame, beam type parts of aircraft,prototype system verifies feasibility of the theoretical study.