Order Reduction of State-Space Aeroelastic Models Using Optimal Modal Analysis

Abstract

An efficient time-domain reduced-order aeroelastic model is presented based on the Roger's state-space rational function approximation model and the frequency-domain Karhunen-Loeve method. Using frequency responses of the Roger's model, the method generates a real, orthogonal set of aeroelastic modes. These Karhunen-Loeve modes are optimal in the solution space with a minimum possible number of modes. When invoked with the Galerkin's error minimization, they generate a reduced-order aeroelastic model. The proposed method is demonstrated using an aeroelastic model of a representative commercial airplane with 638 state variables. It is shown that the aeroelastic results of the reduced-order model match extremely well the results obtained from the full-order model in both open-loop and closed-loop analyses. The new aeroelastic model can be efficiently used in repeated analysis of dynamic loads, optimization, and closed-loop designs.