Optimal protection and maintenance policy for complex systems

For the complex system subject to external detrimental factors and internal wear failures, both the proper protection and efficient maintenance activities on the system elements should be considered in order to maintain a desired level of system availability. A maintenance strategy consisting of preventive replacement and minimal repair is introduced, and the probability of destruction by external impacts is modeled by a contest success function. The system cost and availability are modeled using a universal generating function technique, and an optimization problem is formulated to find the optimal protection and maintenance strategy so that the system cost is minimized and the availability requirement is satisfied. In order to show the procedures, the complex system is assumed to have a series-parallel structure. A numerical example is proposed to show the application of the models.