Date

2023-2-13

Author

Yayla, Metehan

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This thesis proposes improvements to Filter-based Model Reference Adaptive Control (MRAC) architectures for uncertain dynamical systems. Standard MRAC cannot guarantee closed-loop stability in the presence of bounded perturbations without restrictive persistent excitation of system signals. Robust modifications have been introduced to increase the robustness of standard MRAC and/or guarantee stability without persistent excitation, but little improvement has been achieved in guaranteed transient response. Recently, filter-based solutions have been introduced, among which CMRAC has gained a significant reputation due to its simplicity in application, superior adaptation performance to external disturbances, and improvements on transient performance. However, filter-based methods suffer from losing information during filtering, which can degrade adaptation performance, and assume the uncertainty lies in the span of the control input, which may not hold for many practical systems. This thesis proposes a method to recover information lost during filtering in filter-based adaptive controllers, extending it to cover systems with unknown control effectiveness, and introducing a command governor-based adaptive controller architecture to guarantee strict tracking performance in the presence of unmatched uncertainty. The proposed information recovery-based model reference adaptive controller (IR-MRAC) is illustrated with an energy-based longitudinal flight controller architecture, which successfully decouples velocity and altitude responses while benefiting from all the advantages of an energy-based controller. The proposed command governor-based adaptive controller is extended to the lateral flight control problem to achieve the desired tracking performance in the presence of both matched and unmatched uncertainties. Closed-loop stability analyses of all proposed methods are illustrated through rigorous Lyapunov's stability analysis, with numerical examples and software-in-the-loop simulations used to validate the proposed methods in a more realistic environment.

Subject Keywords

filter-based adaptive control, closed-loop stability, guaranteed transient performance, low-pass filter, robustness, unmatched uncertainty, command governor

URI

https://hdl.handle.net/11511/102580

Collections

Graduate School of Natural and Applied Sciences, Thesis