Condition-Based maintenance for a multi-state weighted <i>k</i> -out-of- <i>n</i> : G system considering stochastic dependency

In this article, we investigate a condition-based maintenance (CBM) policy for a multi-state weighted k-out-of-n: G system with stochastic dependency and the competing failures model. In the model, the dependency between components is represented by a copula function, and competing failures exist between the internal degradation and the external shock of the component. Furthermore, the component carries different weights in various states, and the preventive maintenance (PM) actions are imperfect. Based on the above setting, we develop a semi-Markov decision process (SMDP) to optimise the CBM strategy. To simplify the calculation, we discretise the system state and then use the Monte Carlo method to obtain the optimal maintenance threshold and inspection interval. An example of power-generating units is presented to illustrate the proposed strategy, and the impact of the relevant parameters, imperfect maintenance, and the shock process on the maintenance is investigated. Finally, the advantage of the model is further demonstrated through a comparison experiment.