Traditional standby system models have mostly assumed that each element can be online and used once during the mission time. In practice especially when a long mission task is performed, it is beneficial to reactivate some used elements to enhance the mission success probability. This paper proposes a new standby system model, where non-periodic preventive replacements (PR) are conducted to mitigate operating elements’ accumulated deterioration and an element may be activated several times to be online executing the mission task. Moreover, each used element undergoes idle time dependent protection or maintenance actions before its next reactivation. The mission is successful if during the specified mission time no activated element fails while online and operating or before its activation. The mission success probability is evaluated using a probabilistic approach proposed in this paper. The optimal PR scheduling problem is further formulated and solved, which determines the element activation/reactivation schedule maximizing the mission success probability. Examples of homogeneous and heterogeneous standby systems are provided to examine influences of several model parameters and their interactions on the mission success probability as well as on optimal PR schedules. The application of the proposed model to the element sensitivity analysis is also illustrated through example analysis.

传统的备用系统模型主要假设每个元素可以在线使用，并且在任务期间只能使用一次。在实践中，尤其是当执行长任务任务时，重新激活一些用过的元素以提高任务成功概率是有益的。本文提出了一种新的备用系统模型，在该模型中进行了非定期预防性更换（PR）以减轻操作元件的累积损坏，并且可以多次激活一个元件以在线执行任务任务。而且，每个使用过的元件在其下一次重新激活之前都要经历与空闲时间有关的保护或维护动作。如果在指定的任务时间内没有激活的元素在联机和运行中或在激活之前发生故障，则表明该任务成功。使用本文提出的概率方法评估任务成功概率。进一步制定和解决了最佳PR调度问题，该问题确定了使任务成功概率最大化的元素激活/重新激活调度。提供了同类和异类备用系统的示例，以检查几个模型参数及其相互作用对任务成功概率以及最佳PR计划的影响。通过实例分析还说明了该模型在元素敏感性分析中的应用。提供了同类和异类备用系统的示例，以检查几个模型参数及其相互作用对任务成功概率以及最佳PR计划的影响。通过实例分析还说明了该模型在元素敏感性分析中的应用。提供了同类和异类备用系统的示例，以检查几个模型参数及其相互作用对任务成功概率以及最佳PR计划的影响。通过实例分析还说明了该模型在元素敏感性分析中的应用。