Joint optimization of condition-based operation and maintenance strategy for load-sharing systems subject to hybrid continuous and discrete loads

Load-sharing mechanism is a worldwide redundancy designed to enhance system reliability by distributing the total system load among surviving units. Traditional load-sharing systems typically encounter continuous and constant loads that everlastingly influence the system degradation process. However, practical engineering systems, e.g., power supply systems, may simultaneously withstand both continuous loads and discrete loads, where the latter will also have a certain influence on system reliability. To fill the gap of this innovative load characteristic, this paper examines a novel load-sharing system subject to hybrid continuous and discrete loads. Unit basic degradation process is modelled by a nonlinear Wiener process with a continuous-load-related covariate, while discrete loads, arriving according to a homogeneous Poisson process, cause sudden degradation increments. Lifetime distribution of the presented load-sharing system is analytically derived, serving as the basis for downtime cost analysis related to further condition-based operation and maintenance strategy, which is newly proposed by the introduction of dynamic adjustment of unit loads based on their degradation inspections. The Markov decision process is modelled and formulated for joint optimization of inspection interval, condition-based maintenance and dynamic load reallocation. Compared with traditional condition-based maintenance with equal load allocation, numerical studies are conducted to investigate the effectiveness and robustness of dynamic load allocation.