Direct L1-Adaptive Nonlinear Dynamic Inversion Control for Command Augmentation Systems
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© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. Modern high-performance aircraft increasingly use flight control systems based on nonlinear dynamic inversion, which is valid over large flight envelopes and in theory does not require the use of gain scheduling. Dynamic inversion offers perfect tracking of desired dynamics given exact knowledge of the vehicle dynamics and model structure, with perfect measurements and neglecting actuator dynamics. In the real world, implementation of dynamic inversion requires an outer loop for robustness. The use of adaptive control techniques to estimate parameters of the dynamic inversion control law or to augment a baseline dynamic inversion controller offers one solution to the robustness problem. This paper introduces an adaptive nonlinear dynamic inversion control scheme based on the L1adaptive control theory that directly estimates plant parameters used in a nonlinear dynamic inversion control law rather than augmenting a baseline dynamic inversion controller. This controller is used to create a command augmentation system that is demonstrated on a six-degree-of-freedom nonlinear model of an F-16 fighter aircraft. Simulation results presented in the paper show that the controller structure is able to track reference commands for maneuvering flight phases, and that the controller maintains tracking performance in the presence of severe levels of atmospheric turbulence.
author list (cited authors)
Harris, J., & Valasek, J.