存在共模故障的载荷均担共载冗余系统的可靠性研究

Reliability of a Redundant System with Load-sharing and Common Mode Failure

共模故障的存在极大地降低了冗余系统的可靠度,使其失效概率大于预测值一、两个或者更高的数量级。笔者在分析了共模故障相关性及传统可靠性模型局限性的基础上,以零件强度和环境载荷的特征及其相互关系为背景,讨论了载荷均担共载冗余系统的失效机理,建立了载荷随零件失效数增加而增大的载荷均担共载冗余系统的可靠性模型。该模型全面考虑了系统零件之间的相关性,把零件失效看成独立失效和共模失效相互作用的结果,将系统可靠度定义为零件强度最大次序统计量大于载荷的概率。以四零件组成的载荷均担共载冗余系统为例,研究了系统可靠度随零件失效数的变化规律,并运用Monte Carlo方法进行了仿真实验,验证了模型的正确性。

The reliability of a redundant system is reduced when common mode failure exists. Common mode failure makes the true value of failure rate one or two order of magnitude higher than the predicted value. We first analyze the correlation of common mode failure and the limitation of traditional reliability model. Then, considering the characteristics and interrelations of component strength and environment load, we study the failure mechanism of the redundant system with load-sharing and build up a reliability model of the redundant system with load-sharing where the load is increased with the increase of broken-down components numbers. In the process of modeling, parts dependence is taken into account and parts failure is regarded as the results of interaction between independent failure and dependent failure. The system reliability is defined as the probability when the maximal order statistics of strength exceeds the load in this model. We also studied the variation law of system reliability with parts failure numbers, taking the redundant system with load-sharing composed of four parts for example. Finally, the validity of this model was verified by comparing with the Monte Carlo simulation result.