Research On The Key Technologies Of Mobile Three-dimensional Model For Assembly Site Of Complex Product

The definition information of a product is the basis of the design and manufacture stages inthe product development life cycle. Whether the product development activities can besuccessfully accomplished greatly depends on the effective delivery of the definitioninformation through those stages. With the wide application of model based definition (MBD)technology in the development process of modern complex product, the3D models integratedwith complete definition information can be delivered smoothly as the single source ofproduct data through most of the development stages. This promotes the integration of thedesign and manufacturing activities. However, the assembly activity of complex product, suchas the aircraft, aerospace product and ship, is typical discrete assembly activity, which iscurrently still implemented by assembly operators under the guidance of2D paper basedassembly process documents. Consequently, it has failed to deliver the3D models of aproduct to its final assembly stage, i.e., the3D assembly process information cannot bedelivered to the forefront of assembly site to provide intuitional guidance for assemblyoperators. In order to address this issue, this dissertation will devote itself to investigateseveral key technologies regarding mobile3D model for assembly site of complex product, byadopting the emerging computing mode. Therefore, the3D models of a product can bedelivered to the assembly stage, and accordingly, it will improve the efficiency and quality ofthe assembly activity of the product. The main contents of this dissertation are summarized asfollows.First of all, Chapter1analyses the requirement of assembly process information in the mobileform for the assembly site of complex product, and it defines the concept of mobile3D model.The research background and significance has also been dissussed. After reviewing the relatedresearch status, it presents the critical issues demanding to be promptly studied for thepurpose of mobile3D model construction and delivery.Chapter2describes the outline and architecture of this dissertation. The framework of mobile3D model construction and delivery for the assembly site of complex product is proposedbased on the general cognitive and information transfer model. Then, the logical relationshipbetween the components of this framework is analyzed and the key technologies according tothe components are presented respectively.Chapter3proposes a dynamic assembly simplification approach for virtual assembly processof complex product, in order to provide input for the organization and construction of3Dassembly process information in the subsequent chapter. Firstly, the proposed approachregards the virtual assembly process of complex product as an incremental growth process ofdynamic assembly. Based on this assumption, assembly model simplification method with appearance preservation is investigated. Secondly, CAD model simplification method withassembly features preservation is developed according to the following process. The notion of"conjugation" is incorporated into the definition of assembly features. Subsequently, theproblem of assembly features recognition is translated into the problem of conjugatedsubgraphs matching based on subgraph isomorphism. Several algorithms, including theimproved Ullmann‘s algorithm, a heuristic algorithm and a MapReduce based algorithm, aredesigned to address the problem. Thirdly, the flow of dynamic assembly simplificationapproach is presented for the purpose of implementation. Finally, the proposed approach hasbeen tested on several cases and the results show its feasibility and superiority.Chapter4investigates the construction and delivery method of3D assembly processinformation for the assembly site of complex product. The augmented reality (AR) cloudframework for the delivery of3D assembly process information is designed. Under thisframework, augmented reality based assembly order (ARAO) templates are constructed basedon the geometric and engineering semantics. Then, paper based AO describled by a series ofassembly procedures is transformed into ARAO, which is composed of of virtual3Dassembly steps, by taking3D models of the product and tools, the assembly sequence andARAO templates as input. In order to deliver the3D assembly process information to theassembly site, SIFT based features tracking and registering algorithm is designed and furherimplemented under the MapReduce framework, so that ARAO can be registered in the realassembly scene to indicate the assembly position of the next to-be-assembled component ofthe product. The implementation process of the proposed AR cloud system for assembly siteis presented and a case is studied by comparing ARAO with regular3D assembly processinformation which also demonstrates the assembly process of the experimental object.Chapter5discusses the architecture design approach for cloud service of mobile3D model, inorder to provide supporting environment for the construction process and application ofmobile3D model in the enterprises of complex product. Based on the system requirementsengineering theory, an architecture design approach for cloud service of mobile3D model isproposed. After verifying the proposed approach by using the data accumulated in engineeringpractices, a reference architecture for cloud service of mobile3D model is presented.Computing resources allocation strategy for the application of cloud service of mobile3Dmodel is investigated by establishing the computing resources allocation model, anddesigning corresponding algorithm based on ant colony optimization (ACO) algorithm.