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Optimization modeling of system lifecycle cost with availability constraints and inventory optimization

System availability-based design optimization is closely linked with its economy. Under conditions that the life of components follows Weibull distribution, design cost function, manufacturing cost function and maintenance support cost function are presented respectively for a multi-unit system which is composed of identical units. Based on the principle of cumulative failure probability equality, a system operational availability analysis model is established. And then, a lifecycle cost optimization model under system availability constraints is given. System availability and inventory policy in design and operation periods are comprehensively analyzed by the model. Finally, an example analysis of switching systems of a large-scale facility is shown to demonstrate its feasibility and efficiency. In this case, analyses are conducted on the key influencing factors of the system lifecycle cost. A comprehensive evaluation method of system availability and economy is proposed. It is of great significance to provide solutions and methods for system engineers to design the system.