Abstract
The loading level applied during a system's operation can greatly affect the system's productivity and time-tofailure distribution. The optimal loading problem aims to determine loading levels leading to the best system performance. While this problem has been solved for many types of technical systems, very little work was devoted to production systems (PSs) with storage and the existing model assumed the storage is fully reliable and failed to consider effects of the storage's loading levels. This paper makes contributions by solving the optimal loading problem for an imperfect PS having an unreliable storage with possibility to choose different load levels that determine the storage's uploading and downloading paces and load levels that determine the productivity of the PS. Moreover, the downloading load level is chosen dynamically depending on the beginning time of the storage downloading. We evaluate and minimize the expected cumulative unsupplied demand (EUD) during the mission, and perform a detailed case study of a water supply system to demonstrate the proposed model and optimal loading policy solutions. Influences of several model parameters (mission time, PS's reliability, storage's reliability, capacity and initial filling) and their interactions on the EUD and optimization solutions are also examined through examples.