Research On Key Technology Of Knowledge Based Aircraft Assembly Process Planning

Process planning, which is condition-and experience-concerned, is a typical hardwork. For the complexity of aircraft assembly, aircraft assembly process planning(A2P2 for short) is usually considered as an "art" to be undertaken by good qualityand high technique. Consequently, the rules are not acquired easily or represented well,the reasoning is complex and the knowledge adaptation is difficult in developing theexpert systems of A2P2. With the implement of advanced manufacturing technologyin aeronautical enterprise, how to develop the intelligent systems of A2P2 to help toplan aircraft assembly process efficiently has become one of pivotal problems to beresolved. Aiming at this problem, a mechanism of Knowledge Based A2P2 isproposed in this paper. In this mechanism, assembly process planning of sub-assemblyand component is chosen as the research object, Ontology, Knowledge Engineering,Case Based Reasoning (CBR) are adopted as key technologies and XML is adopted asenabling technology, A2P2 knowledge's representation, similarity measurement andadaptation are studied, a prototype (KBA2P2) is developed. To meet the advancementof A2P2, the main research issues and achievements in this paper are as follows:Ontology for A2P2 Knowledge One methodology of constructing ontology isproposed. Under the direction of this methodology, the course of A2P2 is analysed,plenty of data of A2P2 have been collected. With the help of experts in A2P2, theanalysis of these data is done, and the elements affecting A2P2 are separated, thenative knowledge framework of A2P2, which can't be represented well and must beformalized, is gotten. After the transformation and reassembly of native knowledgeframework, the technical terms of A2P2, which can be represented in computerlanguage, are formed, and their relationship is set up. Based on these terms, theontology for A2P2 knowledge is constructed. This ontology lays the foundation ofrepresentation, reasoning and adaptation of A2P2 knowledge.XML-based Representation of A2P2 Knowledge and Construction ofRepository Based on Framework and XML, the representation of A2P2 knowledgeis researched, the BNF and the XML Schema of A2P2 knowledge are given. Theadvantage and disadvantage between XML and RDB (Relational Data Base) iscompared, the conclusion of combining XML with RDB to construct repository isdrawn, and Oracle XML DB is selected as the foundation database of repository. Thestrategy of data storage and mapping between XML and RDB is studied, a hybridstorage strategy of A2P2 knowledge is proposed, and the logical storage structure ofrepository is designed. The mechanism of repository index is researched, a specialstrategy of assembly structure feature of A2P2 knowledge is proposed, and the indexof repository is compiled. With the application of XML and RDB, the key problem ofA2P2 knowledge's representation, organization and management is solved. Similarity Measurement of A2P2 Knowledge Based on the reasoning strategy ofFramework and the Nearest Neighbor,~☉the strategy and algorithm of similaritymeasurement of A2P2 knowledge is proposed. With the use of Delphi and AHP, theweight of knowledge feature in similarity measurement is calculated. After theanalysis of assembly structure feature described as tree model, a similaritymeasurement algorithm, which base on structure-and semantic-constraint of assemblystructure feature, is proposed, it can measure the similarity of assembly structurefeature efficiently. After the analysis of assembly tolerance feature, two similaritymeasurement strategies are proposed, and the mathematic models concemed arepresented. A mechanism of thesaurus to measure similarity of symbol assemblyfeature is proposed, the configuration of thesaurus and the algorithm concerned arepresented, this methodology can measure the conceptional similarity of char data typeknowledge feature. The A2P2 knowledge's reasoning, retrieving and conflict strategy,which correspond to knowledge representation and repository structure, are planned.A2P2 Knowledge Adaptation and A2P2 Knowledge Learning Based on thehuman-machine hybrid intelligence, the adaptation and learning of A2P2 knowledge isresearched. An index strategy based on knowledge retrieving and adaptation ispresented, it uses Result Mark and Time Stamp to raise measurement efficiency andmanage A2P2 knowledge.BOM-based System Integration The evolvement of BOM (Bill of Material) ofproduct life cycle is studied, the relationship between MBOM and A2P2 knowledgefeature is researched, the acquirement strategy of A2P2 knowledge feature is studied,the algorithm to acquire assembly feature from MBOM is given. It proves that BOM isthe bridge of system integration.Finally, a prototype system, KBA2P2 (Knowledge Based Aircraft Assembly ProcessPlanning), is designed and realized to validate the whole thoughts and the keyalgorithms proposed. The prospect of the implement of KBA2P2 is forecasted.