Availability and optimal maintenance policy for systems degrading in dynamic environments

Abstract

In both engineering practice and theory, system degradation is often modeled by a stochastic process. When the degradation behavior is significantly affected by environments, a single stochastic process is not suitable to describe the system degrading in different environments any more. In this paper, a model is developed for systems degrading in dynamic environments subject to several imperfect maintenance actions before each replacement, in which the degradation of the system within different environments is governed by different stochastic processes. The evolution of the environments is described by a Markov process. To describe the system performance, system availabilities including instantaneous availability and limiting average availability, and some time distributions of interest are some important indexes which are derived in the paper. Then the problem of optimal maintenance policy is formulated by considering constraints of availability and operating times. The objective of the optimal maintenance policy is to find an optimal number of imperfect maintenance actions between two adjacent replacements. The existence of the optimal solution is proved and the algorithm of calculation is also presented. Numerical examples are given to illustrate the results obtained in the paper.