Design-Oriented Structural-Model Order Reduction of Strain-Actuated Flight-Vehicle Structures

This paper assesses the accuracy of a number of structural-model order-reduction techniques as applied to strain-actuated (“smart”) flight-vehicle structures modeled with finite elements (FE). Model order reduction is an essential facet when working in a designoriented optimization environment. Therefore, to eventually build a design-oriented multidisciplinary optimization (MDO) capability for large-scale strain-actuated structures (e.g., aircraft, spacecraft), insight into the affects of model order reduction on the accuracy of design constraints and sensitivities must first be gained. In this paper reduced-order models are solved using mode displacement (MD) and mode acceleration (MA) methods. Furthermore, the effect of the chosen reduction bases on model accuracy is also investigated. Specifically, the total number of basis modes used is varied. Fictitious masses (FMs) may be added to areas of the structure where local effects predominate, and massnormalized static solution vectors (Ritz vectors) of important actuation modes may be appended to the bases. By examining the convergence of design constraints and their sensitivities for a variety of model order-reduction approaches (solution methods and reduction bases), valuable insight is gained into the technical challenges that must be addressed when creating a robust MDO capability for strain-actuated structures.