Availability Evaluation and Maintenance Optimization of Balanced Systems Considering State-Dependent Inspection Intervals

There has been increasing attention to the maintenance optimization of balanced systems in recent years. However, existing studies mostly neglect state-dependent inspection intervals and group maintenance, which inadequately addresses the maintenance challenges of balanced systems. Thus, we propose an availability evaluation and maintenance optimization method for balanced systems considering state-dependent inspection intervals. First, multiple maintenance thresholds are introduced to characterize the maintenance strategy considering preventive maintenance and state-dependent inspection intervals, where the next inspection interval is determined based on the post-maintenance system state. Then, the system availability is evaluated by combining semi-regenerative theory and universal generating functions, where calculations are simplified by merging the same system states. Meanwhile, this study also explores the system availability under group maintenance to better reflect reality. Second, the average maintenance cost per unit of time is calculated using the renewal theory. The optimal maintenance thresholds are given by minimizing the maintenance cost under the constraint of minimum system availability. To improve the optimization efficiency, a tabu list-based two-stage iterative partial optimization algorithm is proposed. Finally, the effectiveness of the proposed method is demonstrated through a numerical example involving a lithium-ion battery pack.