Optimal nonperiodic inspection scheme for a multicomponent repairable system with failure interaction using A * search algorithm

Abstract

This paper proposes an approach for finding optimal nonperiodic inspection scheme for a multicomponent repairable system with failure interaction. Failure of one component of the system is hard, i.e., as soon as it occurs, the system stops operating. Failures of the other components are soft, namely, they do not cause the system stop, but increase the system operating costs. Soft failures are detected only if inspection is performed. Thus, the components with soft failure are all inspected at the scheduled inspection instances and are minimally repaired if found failed. When the component with hard failure fails, it is also repaired. However, its failure increases the failure rate of the other components. The system’s expected total cost associated to a given inspection scheme includes inspection costs, repair costs, and the penalty costs that are incurred due to the time delay between real occurrence of the soft failures and their detection at inspections. The objective is to determine the optimal inspection scheme that yields minimum expected total cost. In the proposed approach, the expected total cost is formulated in terms of inspection scheme. Then, A * search algorithm, with a proposed heuristic cost function, for calculating lower bounds, is employed to search through alternative inspection schemes to determine the optimal one. The proposed approach is illustrated through a simplified numerical example.