Abstract: The task reliability level and the basic reliability level are regarded as the constraint conditions, and the development cost of the system is as the object function, so a new system reliability distribution optimization model for redundant design is presented. By means of this model, the system designed can meet the challenge of the task reliability and the basic reliability at a least development cost. Moreover, the least development cost models for the series-parallel and the parallel-series redundancy design are established. At last, all the three models above are verified by several examples and it is shown that the design results given by the system reliability distribution optimization model are more valuable for engineering design.

Key words: system reliability, redundancy design, optimization, basic reliability, task reliability