Mode Acceleration Based Random Gust Stresses in Aeroservoelastic Optimization

The present paper describes a method for obtaining accurate design-oriented stress and stress-sensitivity information from reduced-order linear-time-invariant state-space models of integrated aeroservoelastic systems, using Lyapunov’s Equation for calculating covariance matrices of the displacement and stress responses. A complete formulation of the reduced-order stress gust response problem for aeroservoelastic design synthesis, tailored toward integration with control-system design techniques based on modern control, is presented. It includes an adaptation of the mode-acceleration method, reduced-order analytic sensitivities of stress covariances, and efficient approximations to be used in a nonlinear programming/approximation concepts approach to design optimization. Ar ealistic aeroservoelastic model of a typical passenger airplane is used as a test case, and the paper includes results of convergence studies for the assessment of order-reduction effects on the accuracy of the integrated structure/aerodynamic/control models.

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