Concurrency control of collaborative assembly system under web environment

Based on the analyses of collaborative assembly operations under the web environment, five types of concurrency assembly conflicts were summarized, which are the inconsistent results produced by multi-clients, multi-clients grasping the wrong parts simultaneously, multi-clients assembling the same parts or subassembly in parallel, feasible concurrent subassembly operations being prevented and conflicts of assembly constraints. A hierarchical hybrid concurrency conflicts control model (HCM) was proposed, comprising two control layers and integrating four kinds of concurrency control strategies. The two former concurrency conflicts were eliminated effectively with the concurrency control strategy based on global assembly sequence integrated in the upper control layer. The rest three concurrency conflicts were resolved by the serialization strategy of assembly operations, server-locked and client-unlocked strategy and the strategy of designing assembly constraints library respectively which were integrated in the lower control layer. Finally, a prototype system has been implemented to test the concurrency control strategies, and the results show that the system is flexible and efficient.