Integrated optimization of redundancy allocation and condition-based loading decisions for parallel systems with mixed standby units

Numerous modern mission-critical systems, comprising multiple units executing missions consecutively, require careful determination of the redundancy allocation structure to improve system reliability by maximizing the utilization of standby units. Since these units deteriorate over time due to internal degradation and external environmental factors, and the deterioration rate of each unit is typically dependent on its workload, adjusting load levels based on the inspected healthy condition of the system becomes critical. Thereby, we introduce the utilization of condition information in the decision-making process for load level adjustment in working units. This study is the first to focus on the integrated optimization of redundancy allocation and condition-based load level adjustment policies for parallel systems with mixed standby units. We further extend the trade-off between fully mission completion and system survival during mission duration by introducing the impact of degradation on mission performance quality. We utilize an event-transition based recursive method to obtain the main performance metrics of mission completion and system survival. We further conduct a numerical example to demonstrate the proposed policy. The benefits of condition-based load level adjustment are demonstrated through policy comparison.