Managing Surrogate Objectives to Optimize a Helicopter Rotor Design -further Experiments Managing Surrogate Objectives to Optimize a Helicopter Rotor Design { Further Experiments Aiaa Mdo 98-4717

It is common engineering practice to use response surface approximations as surrogates for an expensive objective function in engineering design. The rationale is to reduce the number of detailed, costly analyses required during optimization. In earlier work, we developed a rigorous and eeective scheme for managing the interplay between the use of surrogates in the optimization and scheduled progress checks with the expensive analysis so that the process converges to a solution of the original design problem. In this paper, we will report our latest numerical tests with a helicopter rotor design problem which has proved to be a fruitful laboratory for experimentation. The results given here support the use of an ANOVA decomposition on a DACE model to identify the most important optimization variables in an optimal design problem. Introduction The use of optimization tools with computer simulations to drive engineering design underpins MDO. However, there still are many important problems for which existing methods are either unreliable ad hoc procedures or impractical. Legacy simulation codes that fail on some plausible inputs and run slowly on the rest are far from the clean, innnitely diier-entiable functions for which optimization specialists design and analyze powerful algorithms. A research collaboration, involving Boeing Applied Research & Technology and Rice University, has developed methods that interpose a computationally clean surrogate function between the optimizer and the simulation, to provide a reasonably accurate model of the true simulation and a function that the optimizer can evaluate quickly. The resulting methods have led to new theories and better practical solutions. We present numerical results here for two versions of one of the target problems for our collaboration, the design of a lower vibration helicopter rotor blade.