Adaptive Augmentation of a Fighter Aircraft Autopilot Using a Nonlinear Reference Model
A Nonlinear Dynamic Inversion (NDI) baseline control architecture based on a nonlinear reference model and augmented by an adaptive element is developed for an agile modern fighter aircraft. This paper mainly focuses on the nonlinear reference model and on a modified NDI error feedback architecture. The chosen reference model contains the main nonlinear plant characteristics and is therefore able to fully exploit the physical capabilities of the fighter aircraft. Starting with the classical inversion control laws, the implemented NDI-based error feedback baseline controller architecture is tailored according to the modifications motivated by the new reference model. In order to keep closed-loop performance in the vicinity of the nominal case, even in the presence of severe uncertainties and turbulence, the aforementioned baseline controller is augmented by an adaptive layer. The employed control architecture has proven its capabilities and its robustness for a large set of uncertainties and in the presence of turbulence effects.