A method is presented for computing multiple-input multiple-output frequency responses of bare-airframe dynamics for systems excited using orthogonal phase-optimized multisines and including correlated inputs arising from control mixing or feedback control. The estimation problem was posed as an underdetermined system of linear equations, for which the additional information needed to determine a solution was obtained from interpolating the frequency responses. A simulation model of the subscale T-2 generic transport airplane was used to investigate the method in open-loop and closed-loop configurations. The method was also demonstrated using flight test data from the X-56A aeroelastic demonstrator, flown with mixing of the control surfaces and operating under closed-loop control. Results demonstrated that the method accurately estimates the bare-airframe frequency responses in the presence of correlated inputs arising from control mixing and feedback control.
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