A multicriteria optimisation model for reliability design of series‐parallel systems: part 1

Purpose – Reliability is a major quality characteristic which has grown in importance as products/systems have become ever more sophisticated. Neglecting it could spell great losses in terms of patronage, revenue, and even lives. The purpose of this paper is to present a multi‐criteria optimisation model and methodology for the Pareto optimal assignment of reliability to the components of a series‐parallel system in order to maximise its reliability. Design/methodology/approach – The subsystems' reliabilities are maximised independently but simultaneously in order to maximise the overall system reliability, while a penalty function modelling cost of reliability improvement is minimised. The resultant continuous and nonlinear optimisation problem is scalarised by a convex combination of the criteria and the MATLAB Optimisation Toolbox is used to generate the solutions. Findings – The results for an illustrative example problem extracted from the literature show that: higher reliabilities could be assigned to the components, in order to achieve or exceed target system reliability; cost increased sharply with slight improvements in the component reliabilities, and the model was stable under the weighting scheme used. Originality/value – The novelty of this work is in: the multi‐criteria optimisation view taken of the design problem; the focus on the subsystems' reliabilities and cost as the criteria to be optimised; the use of the two aforementioned qualities for the purpose of Pareto assignment of component reliabilities in a system's design; and the use of the model and methodology in the context of series‐parallel systems.