Multistage Reliability-Based Design Optimization and Application to Aircraft Conceptual Design

A new proposal for formulating reliability-based design optimization problems, named the multistage reliability-based design optimization approach, is presented. The classical reliability-based design optimization formulation determines all decision variables here and now in the presence of uncertainty. Nevertheless, in many complex systems design applications, the product development process gradually evolves through time, and decisions at the ensuing milestones are made on the basis of increased knowledge on previously uncertain factors. If the delay leading to such informed resolutions is deemed acceptable to the decision maker, then it would be advantageous to wait and see how the less-urgent design issues run their courses until more concrete insights on the relevant uncertain parameters are obtained. The multistage reliability-based design optimization approach accounts for such follow-on corrective decisions based on the partial realizations of random parameters at selected stages along the engineering design process, thereby further enhancing the practicality of reliability-based design optimization. This paper presents a mathematical formulation of multistage reliability-based design optimization and its application to a conceptual design of a regenerative solar powered high-altitude aircraft, which indicate that the multistage reliability-based design optimization method, reflecting real-world engineering practices, produces more favorable solutions than the classical reliability-based design optimization approach.