Multi-Objective and Multi-Stage Reliability Growth Planning in Early Product-Development Stage

This paper proposes a multi-objective multi-stage reliability growth planning method in the early product-development stage. Multi-stage reliability growth planning is common in practice, and it aligns well with multiple developmental stages of a new product such as concept design, detail design, prototype design, and final production version design. The multi-objective formulation reflects the needs of product development's multiple objectives, such as program cost, schedule, and reliability. Pareto optimal solutions of the multi-objective multi-stage formulation for reliability growth planning are searched using a modified nondominated sorting genetic algorithm (NSGA-II). To reduce the large size of Pareto optimal solutions to a workable size of efficient solutions for plan implementation, both constant return-to-scale and variable return-to-scale data envelopment analysis (DEA) methods are used for determining the efficient solutions. Based on tradeoff and sensitivity analysis, insights and guidelines are presented for choosing appropriate reliability growth plans in terms of optimal allocation of testing time and testing units, and the timing for new technology introduction. The growth rate in each product-development stage and its impact on the development cost, schedule, and reliability are also discussed. An illustrative example is given to demonstrate the approach for planning the reliability growth for a next-generation engine development.