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Title:L1 adaptive control for nonlinear and non-square multivariable systems
Author(s):Lee, Hanmin
Director of Research:Hovakimyan, Naira
Doctoral Committee Chair(s):Hovakimyan, Naira
Doctoral Committee Member(s):Voulgaris, Petros G.; Stipanovic, Dusan M.; Salapaka, Srinivasa M.
Department / Program:Aerospace Engineering
Discipline:Aerospace Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Adaptive control
Robust adaptive control
L1 adaptive control
Nonlinear system
Non-square system
Aerospace applications
Abstract:This research presents development of L1 adaptive output-feedback control theory for a class of uncertain, nonlinear, and non-square multivariable systems. The objective is to extend the L1 adaptive control framework to cover a wide class of underactuated systems with uniform performance and robustness guarantees. This dissertation starts by investigating some structural properties of multivariable systems that are used in the development of L1 adaptive output feedback controllers. In particular, a state-decomposition is introduced for adaptive laws that only depends on the output signals. The existence of the decomposition is ensured by defining a virtual system for underactuated plants. Based on the mathematical findings, we propose a set of output feedback solutions for uncertain underactuated systems. In adaptive control applications, a baseline control augmentation is often preferred, where the baseline controller defines the nominal system response. Adaptive controllers are incorporated into the control loop to improve the system response by recovering the nominal performance in the presence of uncertainties. This thesis provides a solution for L1 output feedback control augmentation. Stability and transient performance bounds are proven using Lyapunov analysis. To demonstrate the benefits of the L1 adaptive controllers we consider a missile system and an inverted pendulum, which are both underactuated systems. Finally, we propose a filter design framework in the frequency domain. A new sufficient condition is presented to ensure stability of the closed loop and the reference systems, which is subsequently used in the optimal filter design. Existing H-infinity optimization techniques are leveraged to address the performance and robustness trade-off issues.
Issue Date:2017-07-14
Rights Information:Copyright 2017 Hanmin Lee
Date Available in IDEALS:2017-09-29
Date Deposited:2017-08

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