Determining Line Replaceable Units in Multi-Level Systems

摘要

This talk deals with a maintenance optimization problem of multi-level systems. Multi-level systems consist of modules and components with hierarchical structure (Yun and Kim (2004), Yun et al. (2007)). When the system fails, we follow the hierarchical path to replace components failed. One critical optimization problem of the multi-level systems is to determine the line replaceable units (LRU) among modules and components in the hierarchical structure (Dandotyia et al., 2008). If components are determined as LRU, we can reduce the repair cost at system failures but system repair takes long time. If the units (modules) in the high level are determined as LRU to reduce repair times, the repair cost is high. Recently, Puig and Basten (2015) proposed an optimization model to determine LRUs of multi indenture systems. The total cost is minimized while the availability constraint is met. But they do not consider the repair costs and times in detail. Thus, we want to find the optimal LRUs in multi-level systems and the expected maintenance cost rate and the system availability are used as optimization criteria. We consider repair costs and times in detail and the expected maintenance cost rate and the system availability are obtained in case that the failures of components in the system follow Exponential distributions. A simple heuristic method is used to find the optimal LRU units and some numerical examples are studied to evaluate the influence of the parameters to the optimal solutions. Some extended problems are also studied in this paper. For example, we consider preventive maintenance to replace the failed units together (Yun and Park (2017) and Han et al. (2015)).