Abstract: Mechanical systems is vulnerable under the influence of its structure and human factors due to its subsystems， components and the complex relationship between each unit，thus mechanical systems can cause the mechanical systems fail，which severely affects the reliability of the mechanical systems． From safety，intermediate and failure three aspects，3- level working model of“safety，intermediate，failure”is introduced to reflect the reliability ( functioning fully) of mechanical systems，intermediary transition between reliable and failure，failure ( can not work) based on Petri net models of mechanical systems analysis． Through using the operation and exchange algorithms of random incident，and considering the different values of related parameters among basic events which causes failure that impacts on the reliability of mechanical system，the calculation of mechanical system reliability vector with the intermediate state is established．

Key words: mechanical systems, reliability vector, intermediate state, failure relevance, Petri net

摘要： 机械系统因其各子系统、各部件、各单元之间的相互复杂关系，容易受到自身结构与人为因素的影响，导致其 发生失效，严重影响了机械系统的可靠性。在利用Petri 网模型对机械系统分析的基础上，并引入“安全—中介— 失效”3 级工作模式，从安全、中介、失效3 个方面来反映机械系统的可靠( 完全正常工作) 、可靠与失效的中介过 渡、失效( 完全不能工作) 。通过采用随机事件的交、并运算法则，同时考虑引起失效的基本事件间的相关参数λ 的 不同取值对系统的可靠性的影响，最终建立具有中介状态的机械系统可靠性向量的计算方法。

关键词: 机械系统, 可靠性向量, 中介状态, 失效相关, Petri 网