两部件串联系统拟周期预防性维修策略优化

为研究多种随机因素对一类两部件串联系统预防性维修决策的影响，提出一种拟周期预防性维修策略优化模型．假设预防性维修对部件1为完整修，对部件2为保养，预防性活动在实施区间内根据动态计划随机进行；意外更换和预防性更换的竞争结果决定系统的更换，当部件2发生严重故障时引发系统的意外更换，当预防性维修次数达到设定的阈值Ⅳ时实施预防性更换．通过建模和优化分析，给出了最优预防性维修实施区间和最佳维修次数的求解算法，并通过数值案例对模型的优化过程和参数的敏感性做了说明．分析结果表明，在满足实际生产需求的前提下，尽可能地缩短实施区间能提高系统的平均运行时间和降低系统的长期运行成本率．

Optimal quasi-periodic maintenance policies for two-unit series system

To investigate the effects of various random factors on the preventive maintenance （PM） decision-making of one type of two-unit series system, an optimal quasi-periodic PM policy is introduced. Assume that PM is perfect for unit 1 and only mechanical service for unit 2 in the model. PM activity is randomly performed according to a dynamic PM plan distributed in each implementation period. A replacement is determined based on the competing results of unplanned and planned replacements. The unplanned replacement is trigged by a catastrophic failure of unit 2, and the planned replacement is executed when the PM number reaches the threshold N. Through modeling and analysis, a solution algorithm for an optimal implementation period and the PM number is given, and optimal process and parametric sensitivity are provided by a numerical example. Results show that the implementation period should be decreased as soon as possible under the condition of meeting the needs of practice, which can increase mean operating time and decrease the long-run cost rate.