Optimal preventive maintenance strategy for populations of systems that generate outputs

This is the first study in the reliability literature that discusses optimal maintenance in dynamic populations of statistically identical items. Items that generate an output/gain with a value interpretation, e.g., the performed amount of work, the manufactured product, etc., are considered. The expectation of the overall gain on a cycle of performance defines the corresponding objective function for the preventive maintenance (PM) optimization for a single item, which is also used to develop theory for dynamic populations of items. It is shown that the optimal PM time for dynamic populations of items is larger than that for a single item. Generalizations to the cases when an item is characterized by the major and minor failures and when the output rate is a function of time are considered. It is shown how the framework developed here is relevant to an industrial setting using an example of a fleet of wind turbines. Some numerical results illustrate our findings.