SYSTEM RELIABILITY OPTIMIZATION WITH k-OUT-OF-n SUBSYSTEMS

Abstract

Optimal solutions to the redundancy allocation problem are determined for systems designed with multiple k-out-of-n subsystems in series. The objective is to select the components and redundancy levels to maximize system reliability given system-level constraints. The individual subsystems may use either active or cold-standby redundancy, or they may require no redundancy. Previously, optimization methods for this problem either pertained to k-out-of-n systems consisting of a single subsystem or to series–parallel systems (k=1). Additionally, it had generally been assumed that only active redundancy was to be used. In practice design problems can vary appreciably from these restrictions and the design process may consider more complex system configurations. Unfortunately, available optimization algorithms are inadequate for many of these design problems. The methodology presented here is specifically developed to accommodate the case with k-out-of-n subsystems. Optimal solutions to the problem are found by an equivalent problem formulation and integer programming. The methodology is demonstrated on a well-known test problem with interesting results. The availability of this tool fills a void and should result in more reliable and cost-effective engineering designs.