Sn. Patnaik et al., A CASCADE OPTIMIZATION STRATEGY FOR SOLUTION OF DIFFICULT DESIGN-PROBLEMS, International journal for numerical methods in engineering, 40(12), 1997, pp. 2257-2266
A research project to evaluate comparatively ten different non-linear
optimization algorithms was completed recently. A conclusion was that
no single optimizer could successfully solve all the 40 structural des
ign problems in the test-bed, even though most optimizers successfully
solved at least one-third of the problems. We realized that improveme
nts to search directions and step lengths, available in the ten optimi
zers compared, were not likely to alleviate the convergence difficulti
es. For the solution of those difficult problems we have devised an al
ternate approach called, the cascade optimization strategy. The strate
gy utilizes several optimizers, one followed by another in a specified
sequence, to solve a problem. A pseudo-random dumping scheme perturbs
the design variables between the optimizers. The cascade strategy has
been tested out successfully in the design of supersonic and subsonic
aircraft configurations and air breathing engines for high-speed civi
l transport applications. These problems could not be successfully sol
ved by an individual optimizer. The cascade optimization strategy, how
ever, generated feasible optimum solutions for both aircraft and engin
e problems. This paper presents the cascade strategy, solution of airc
raft and engine problems along with discussions and conclusions. (C) 1
997 by John Wiley & Sons, Ltd.