Collaborative Assembly Sequence Planning Under Distributed Environment

As the key supporting technology of concurrent engineering and computer integratedmanufacturing, computer aide assembly planning is one of the important issues to digitalpre-assembly that determines the production cost to a great extent. Along with the increase ofparts in products, assembly sequence planning is more and more difficult. In addition, thenetworked manufacturing pattern requires collaborative pre-assembly technology. So adistributed and integrated framework for cooperative design for assembly is presented, andthe collaborative assembly sequence planning method for complex products is investigated. Based on analysis of general assembly configuration design and informationrequirements of assembly model for collaborative sequence planning, the idea of assemblymodeling that contains intents, process and results of assembly design is put forward. Aknot-based assembly relation graph and a shared-part-based hierarchical tree of local productstructures for sequence planning are investigated and constructed. The information of parts,knots and management, which are the elements of assembly model for collaborative sequenceplanning, is clarified. An ant colony system based cooperative algorithm is presented and realized for assemblysequence generation and optimization of local structures adopting assembly by disassemblyscheme. In the algorithm, the implicit sequence space is built dynamically by disassemblycomplete graph and the starting nodes are set on initially feasible disassembly operations. Thegeometric feasibility reasoning of assembly process based on integrated disassembly matrix isused to restrict the search and ensure the validity of sequences. The characteristics of thealgorithm are discussed and the comparisons to other intelligent assembly optimizationalgorithms are analyzed. According to the hierarchical tree, the synthesis process of local sequences based onshared parts involving adjustment, combination, elimination of redundant constraints, andsearch of sequences in a bottom-to-up manner is investigated. The adjustment rules to localsequences are discussed. A spatial blocking graph is proposed to express global assemblyprecedence relations among parts of different local structures, and an algorithm to erase theredundant information in merged sequences is given. The reference product assemblysequences are gained by searching the resulted precedence graph of products based on thefounded assembly experience and knowledge repository. Aiming at the collaborative decision making of assembly scheme under networked IIenvironment among disperated multi-users, a 5-tuple model of collaborative assembly activityis proposed. The mechanisms comprising a token model of operation right, replicativesynchronization of virtual scene, and the description, transfer, and parsing of collaborativeassembly communication protocol based on assembly operation event are discussed in details.By separating application and visualization aspects, a master assembly model based collisioncheck mode is given to suit assembly activities under networked environments. A staticdocument and dynamic model method of assembly visualization for multi-clients isexpatiated. The general architecture of prototype system for collaborative assembly sequenceplanning and decision-making is given. By using VC++, Java, VRML, Socket, Protoolkits,and Open API, four functional models including assembly modeling for collaborativesequence planning, ant colony assembly sequence optimization, assembly sequence synthesis,and networked platform for collaborative assembly decision are implemented. The practicalproduct assemblies are used to validate the correctness and effectiveness of the researchresults. In the end of the dissertation, conclusions have been drawn and the future directions inthe field are given.