Optimal Structure in Heterogeneous Multi-state Series-parallel Reliability Systems

The problem of allocating optimum heterogeneous redundancy in multi-state series-parallel reliability structures is addressed in this paper. The objective is to obtain a configuration that minimizes the total cost of system design satisfying the given reliability constraint and the consumer load demand. The demand distribution is presented as a piecewise cumulative load curve and each subsystem is allowed to consist of parallel redundant components of not more than four types to construct a reliable system. The redundant components are capacitated binary and chosen from a list of products available in the market. The components are characterized by their feeding capacity, reliability and cost. A system that consists of elements with different reliability and productivity parameters has the capacity strongly dependent upon the selection of constituent components. A binomial probability based method to compute exact system reliability index is suggested. To analyze the problem and suggest an optimal system structure an ant colony optimization (ACO) algorithm is presented. The solution approach consists of a series of simple steps as used in basic ACO algorithms and is still capable to yield very good solutions with promising time efficiency. A randomly generated problem of power station coal transportation system with initial structure is solved for illustration.