Aimed at the deficiencies of resources based time Petri nets （RBTPN） in doing scheduling analysis for distributed real-time embedded systems, the assemblage condition of complex scheduling sequences is presented to ...Aimed at the deficiencies of resources based time Petri nets （RBTPN） in doing scheduling analysis for distributed real-time embedded systems, the assemblage condition of complex scheduling sequences is presented to easily compute scheduling length and simplify scheduling analysis. Based on this, a new hierarchical RBTPN model is proposed. The model introduces the definition of transition border set, and represents it as an abstract transition. The abstract transition possesses all resources of the set, and has the highest priority of each resource; the cxecution time of abstract transition is the longest time of all possible scheduling sequences. According to the characteristics and assemblage condition of RBTPN, the refinement conditions of transition border set are given, and the conditions ensure the correction of scheduling analysis. As a result, it is easy for us to understand the scheduling model and perform scheduling analysis.展开更多
研究了Petri网在柔性制造系统中的故障诊断问题。针对柔性制造系统中工业机器人故障率高且部分关键信息无法通过传感器获取的问题,利用时间Petri网在实时系统中的重要作用,结合部分可观时间Petri网和状态类图(state class graph,SCG),...研究了Petri网在柔性制造系统中的故障诊断问题。针对柔性制造系统中工业机器人故障率高且部分关键信息无法通过传感器获取的问题,利用时间Petri网在实时系统中的重要作用,结合部分可观时间Petri网和状态类图(state class graph,SCG),提出构建修正状态类图(modified state class graph,MSCG)的方法。首先根据执行机构是否可观分为可观测变迁和不可观测变迁并结合变迁触发关系(同步、异步)修正各变迁时间区间建立系统的修正状态类图(MSCG)。然后根据提出的故障诊断算法,寻找所有满足可观测变迁触发时间和序列信息的路径,判断所有路径组成的集合是否包含故障变迁,诊断系统是否发生故障。最后以某柔性制造系统为例,结合零件加工过程中各执行机构可观测状态,建立Petri网模型,对系统不可观部分进行故障诊断,验证了算法的有效性。展开更多
文摘Aimed at the deficiencies of resources based time Petri nets （RBTPN） in doing scheduling analysis for distributed real-time embedded systems, the assemblage condition of complex scheduling sequences is presented to easily compute scheduling length and simplify scheduling analysis. Based on this, a new hierarchical RBTPN model is proposed. The model introduces the definition of transition border set, and represents it as an abstract transition. The abstract transition possesses all resources of the set, and has the highest priority of each resource; the cxecution time of abstract transition is the longest time of all possible scheduling sequences. According to the characteristics and assemblage condition of RBTPN, the refinement conditions of transition border set are given, and the conditions ensure the correction of scheduling analysis. As a result, it is easy for us to understand the scheduling model and perform scheduling analysis.
文摘研究了Petri网在柔性制造系统中的故障诊断问题。针对柔性制造系统中工业机器人故障率高且部分关键信息无法通过传感器获取的问题,利用时间Petri网在实时系统中的重要作用,结合部分可观时间Petri网和状态类图(state class graph,SCG),提出构建修正状态类图(modified state class graph,MSCG)的方法。首先根据执行机构是否可观分为可观测变迁和不可观测变迁并结合变迁触发关系(同步、异步)修正各变迁时间区间建立系统的修正状态类图(MSCG)。然后根据提出的故障诊断算法,寻找所有满足可观测变迁触发时间和序列信息的路径,判断所有路径组成的集合是否包含故障变迁,诊断系统是否发生故障。最后以某柔性制造系统为例,结合零件加工过程中各执行机构可观测状态,建立Petri网模型,对系统不可观部分进行故障诊断,验证了算法的有效性。
