Maintenance Policies for Two-Unit Balanced Systems Subject to Degradation

In this article, we present a novel maintenance policy optimization method for systems with two balanced components. The components in the system are assumed to degrade over time according to a bivariate Wiener process. The maintenance actions aim at eliminating the differences of degradation levels of system components at the cost of aggravating the degradation. Utilizing the Markov decision process, the maintenance model is put forward under both the finite and the infinite planning horizons, from which we find the structural properties of the optimal policies. Backwards dynamic programming and value iteration algorithms are employed to optimize the maintenance decisions. Examples along with sensitivity analysis are presented to facilitate the illustration and insight attainment. We find that the maintenance policies are to a great extent regulated by the absolute degradation difference between the two components.

I. Introduction

Many industrial systems and consuming products contain balanced components, for example, the wheels of trains and the multiple propellers of unmanned aerial vehicles (UAVs). Unlike conventional multicomponent systems, such systems and products generally require a balanced performance provided by each component to fulfill their intended missions. The analyses regarding the reliability and availability of balanced systems have attracted considerable attentions in both the communities of researchers and practitioners [1]. However, extensive review of literature reveals that how to optimize the maintenance policies for balanced systems has been underexplored. For practitioners in reliability engineering, the precise understanding of system reliability is mostly employed to advise decision making problems in order to cut operational cost and improve the system performance. Among these problems, maintenance policy optimization has been a pivotal one, which acts as a long-lasting popular topic in related research areas [2]–[4]. As sensor technologies advance at an immense pace in recent decades, condition-based maintenance (CBM) that utilizes the system health information, which is usually modeled as degradation, to advise maintenance scheduling is playing an increasingly important role to achieve appealing maintenance outcomes at lower costs [5]. The failures of components in many balanced systems can be attributed to degradation, in which case the CBM policy can be applied.