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Multiple-Timescale Nonlinear Control of Aircraft with Model Uncertainties

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This paper develops a multiple-timescale slow state tracking nonlinear controller to accomplish large-amplitude combined longitudinal and lateral/directional maneuvers of a nonlinear, nonstandard six-degree-of-freedom aircraft model in the presence of uncertain inertias, control derivatives, and an engine time constant. The control synthesis uses the evolution of the slow states, slow actuators, fast states and fast actuators in a total of four different timescales. Multiplicative and additive uncertainties in the evolution of the slow and the fast states are accounted for, as well as multiplicative uncertainties in the slow and fast actuator dynamics. The controller is designed with insights from geometric singular perturbation theory, and it is supported by update laws selected via a composite Lyapunov analysis. The boundedness of the tracking errors, manifold errors and parameter estimation errors is proven; and the magnitudes of the tracking errors, parameter estimation errors, and control signals can be modulated by appropriate choices of gains. The results presented in the paper using a nonlinear six-degree-of-freedom simulation show improved velocity control for the multiple-timescale nonlinear controller as compared to a cascaded nonlinear dynamic inversion controller.


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