中文摘要：

针对多级保障系统的建模及其优化问题，基于广义随机Petri网建立了三级维修二级库存保障系统的工作流模型．根据不同等级的维修工作流，提出了广义排队时间的概念，运用扩展的排队模型分析各维修流程的性能等价时间．为了保证单元的可用度，提出了以最小化缺货次数为目标的优化策略．采用随机Petri网分析方法对模型进行规约优化，并构造同构的马尔可夫链，求解稳定状态概率分析系统性能，获得一种单元可用度的新计算方法．

英文摘要：

To model and optimize multi-echelon support systems, workflow models of the support system with a classic structure of three-echelon repair and two-echelon inventory are set up based on generalized stochastic Petri net. According to various maintain processes at different levels, extended queue models with generalized queuing time concept are presented to analyze the performance equivalent time. An optimized strategy of spare parts inventory minimizes the number of backorder for unit＇s operational availability. State spaces of model are reduced and isomorphic Markov chain is constructed by the approach to analyze stochastic Petri net. Moreover, by solving probability of steady state, system performance is analyzed. Finally, a new method to calculate unit＇s operational availability is obtained.