The author develops a nonlinear longitudinal model of an aircraft modeled byrigid fuselage, tail, and wing, where the wing is attached to the fuselage with a torsionalspring. The main focus of this research is to retain the full nonlinearitiesassociated with the system and to perform gust load alleviation for the model bycomparing the impact of a proportional-integral- lter nonzero setpoint linear controllerwith control rate weighting and a nonlinear Lyapunov-based controller. Thefour degree of freedom longitudinal system under consideration includes the traditionallongitudinal three degree of freedom aircraft model and one additional degreeof freedom due to the torsion from the wing attachment. Computational simulationsare performed to show the aeroelastic response of the aircraft due to a gust loaddisturbance with and without control. Results presented in this thesis show thatthe linear model fails to capture the true nonlinear response of the system and thelinear controller based on the linear model does not stabilize the nonlinear system.The results from the Lyapunov-based control demonstrate the ability to stabilize thenonlinear response, including the presence of an LCO, and emphasize the importanceof examining the fully nonlinear system with a nonlinear controller.
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