Integrated Planning of Usage-Based Maintenance and Load Sharing Under Resource Dependence

In many systems, functionally interchangeable units are used together to meet a common demand or production target. Such examples include parallel machines in production facilities, engines of a vessel, and fleets of ships, airplanes, or trucks. These units typically receive large-scale maintenance dependent on their usage (such as overhauls) and therefore, the timing of their maintenance is directly affected by the policy that determines how the total demand is allocated to the units. We assume that there is a limit on how many units can get maintenance simultaneously because of the limited resources that are involved (e.g., a dry-dock, hangar, or specialized workforce) and/or because the demand needs to be met at all times. In this study, the problem of integrated planning of usage-based maintenance and load sharing (i.e., the allocation of total demand to different units) for multi-unit systems is mathematically analyzed. Also, a mathematical model is built to minimize the total maintenance costs during the
finite lifetime of the units (which is generally 10 to 40 years). An asymptotically near-optimal policy is proposed, and its performance is compared with the performance of the optimal policy.