Optimal inspection and maintenance policy for the multi-unit series system

The optimal inspection and maintenance policy for the multi-unit series system with economical dependence is investigated in this paper. This system is composed of two kinds of units, which are subjected to the deterioration failure and the Poisson failure respectively. Since costs can be saved when several units are jointly repaired instead of separately, the optimal maintenance model for multi-unit system should not limit itself to a simple juxtaposition of the mono-unit models and lead to the complex problem. To solve this problem, a classical opportunistic maintenance policy is extended to coordinate the maintenance of the two kinds of units and minimize the long-run maintenance cost of the system. To get the multi-threshold control-limit policy, the improved Markov decision approach is presented. Finally, a numerical example is put forward to illustrate the implementation of the model and iteration algorithm.