Flexible implementation of approximation concepts in an MDO framework

Abstract

This paper describes the flexible implementation of approximation concepts in an MDO framework offered by the commercial-off-theshelf software package iSIGHT. Three different types of approximation models - Response Surface Modeling, Taylor Series Approximations, and Variable Complexity Modeling - are implemented in such a way that they may be used interchangeably in any combination to approximate any segment of an MDO analysis problem, as well as the complete system analysis sequence as a whole. The novelty of the implementation is in the fact that all approximation models are implemented as smart objects. Each of the objects possesses certain characteristics defined by the tuning parameters specific to each approximation type, and a suite of methods (actions) which operate on the data of each model. The concept of Response Surface Modeling is taken to the extreme of simplicity and efficiency by using a minimum number of design analyses for model construction and then gradually improving the quality of the model following the path of the optimizer The category of Taylor Series Approximations actually spans a whole suite of approximation techniques that are based on using the first derivatives of the response function. Applications demonstrate the utility and flexibility of the approach.