Inspection policy optimization for hierarchical multistate systems under uncertain mission scenarios: a risk-averse perspective

Most engineered systems intend to perform missions with a pre-specified target success probability to reduce undesirable failure risks. Before executing the next mission, inspection activities are conducted across various physical levels for assessing the probability of mission success. However, due to the randomness of a system’s degradation behavior and the presence of measurement errors, inspection results inevitably contain uncertainty. Meanwhile, the mission duration and acceptable system states may also be uncertain due to uncontrollable factors, such as random operating environments and mission demands. In such a circumstance, it is of great significance to identify the optimal multilevel inspection policy to answer, as great confident as possible, the question that the system can complete the next mission with a target mission success probability. A novel metric is developed to gauge the effectiveness of a multilevel inspection policy to assess if the system can complete the next mission with the target success probability from a risk-averse perspective, based on which an optimization method is put forth to seek an inspection policy under uncertain scenarios with the aim of minimizing the maximum regret of the proposed metric. A stochastic fractal search algorithm, along with two tailored local search rules, is designed to resolve the resulting optimization problem efficiently. Two cases, including a three-component system and a rocket fueling mechanism’s control system, are used to illustrate the efficacy of the proposed approach which is capable of effectively identifying the risk of mission failures by inspection policies.