Optimal Scheduled-Maintenance Policy Based on Multiple-Criteria Decision-Making

Usually, more than one independent (conflicting) criterion is important in determining the replacement age of a critical item for a maintained system. In this study, mathematical models have been developed for three such criteria: 1) minimum replacement cost-rate, 2) maximum availability, and 3) lower-bound on mission reliability. The solutions are obtained using four methods for multiple criteria decision making: 1) strictest-selection, 2) lexicographic, 3) Waltz lexicographic, and 4) sequential multiple-objective problem-solving technique (SEMOPS). Using an aircraft engine as an example, the optimal replacement age has been found by the four different methods. The results and the implications of the methods are discussed.