Optimal maintenance strategy of deteriorating system under imperfect maintenance and inspection using mixed inspection scheduling

An operating system suffers from degradation. Each degradation level can be represented by a state, making the system a multi-state system. In many situations, there are no apparent symptoms indicating the system's state, and system's degradation level can only be known through thorough inspection. Through condition monitoring, the system's state can be estimated with some uncertainty. In this work, we investigated inspection-maintenance schemes for such a system. Our assumptions are that the maintenance is imperfect and the degradation is a continuous-time Markov process. We proposed a strategy that combines both inspection and continuous monitoring to reduce unnecessary thorough inspection and to improve the system's reliability. Optimal maintenance strategy is derived based on an iterative algorithm to minimize the mean long-run cost rate.