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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Analysis and Control of Non-Affine, Non-Standard, Singularly Perturbed Systems

Narang, Anshu 14 March 2013 (has links)
This dissertation addresses the control problem for the general class of control non-affine, non-standard singularly perturbed continuous-time systems. The problem of control for nonlinear multiple time scale systems is addressed here for the first time in a systematic manner. Toward this end, this dissertation develops the theory of feedback passivation for non-affine systems. This is done by generalizing the Kalman-Yakubovich-Popov lemma for non-affine systems. This generalization is used to identify conditions under which non-affine systems can be rendered passive. Asymptotic stabilization for non-affine systems is guaranteed by using these conditions along with well-known passivity-based control methods. Unlike previous non-affine control approaches, the constructive static compensation technique derived here does not make any assumptions regarding the control influence on the nonlinear dynamical model. Along with these control laws, this dissertation presents novel hierarchical control design procedures to address the two major difficulties in control of multiple time scale systems: lack of an explicit small parameter that models the time scale separation and the complexity of constructing the slow manifold. These research issues are addressed by using insights from geometric singular perturbation theory and control laws are designed without making any assumptions regarding the construction of the slow manifold. The control schemes synthesized accomplish asymptotic slow state tracking for multiple time scale systems and simultaneous slow and fast state trajectory tracking for two time scale systems. The control laws are independent of the scalar perturbation parameter and an upper bound for it is determined such that closed-loop system stability is guaranteed. Performance of these methods is validated in simulation for several problems from science and engineering including the continuously stirred tank reactor, magnetic levitation, six degrees-of-freedom F-18/A Hornet model, non-minimum phase helicopter and conventional take-off and landing aircraft models. Results show that the proposed technique applies both to standard and non-standard forms of singularly perturbed systems and provides asymptotic tracking irrespective of the reference trajectory. This dissertation also shows that some benchmark non-minimum phase aerospace control problems can be posed as slow state tracking for multiple time scale systems and techniques developed here provide an alternate method for exact output tracking.
2

Automatic Prevention and Recovery of Aircraft Loss-of-Control by a Hybrid Control Approach

Zhao, Yue 04 August 2016 (has links)
No description available.
3

Contribution au pronostic des systèmes à base de modèles : théorie et application / Contribution to nonlinear systems prognosis based on models : theory and application

Gucik-Derigny, David 09 December 2011 (has links)
Cette thèse est une contribution au problème du pronostic des systèmes complexes. Plus précisément, elle concerne l'approche basée modèles et est composée de trois contributions principales. Tout d'abord, dans une première contribution une définition du concept de pronostic est proposée et est positionnée par rapport aux concepts de diagnostic et de diagnostic prédictif. Pour cela, une notion de contrainte temporelle a été introduite afin de donner toute pertinence à la prédiction réalisée. Il a également été montré comment le pronostic est lié à la notion d'accessibilité en temps fini.La deuxième contribution est dédiée à l'utilisation des observateurs à convergence en temps fini pour la problématique du pronostic. Une méthodologie de pronostic est présentée pour les systèmes non linéaires à échelle de temps multiple. Puis, une troisième contribution est introduite par l'utilisation des observateurs par intervalle pour le pronostic. Une méthodologie de pronostic est proposée pour les systèmes non linéaires incertains à échelle de temps multiple. Pour illustrer les différents résultats théoriques, des simulations ont été conduites sur un modèle de comportement d'un oscillateur électromécanique. / This thesis is a contribution to the problem of a complex system prognosis. More precisely, it concerns the model-based prognosis approach and the thesis is divided into three main contributions. First of all, a definition of prognosis concept is proposed as a first contribution and is positionned in reference to the diagnosis and predictive diagnosis concepts. For that, a notion of temporal constraint is introduced to give all pertinence to the prediction achieved. It is also shown how prognosis is linked to the finite time reachability notion. The second contribution is dedicated to the use of finite time convergence observer for the prognosis problem. A prognosis methodology is presented for nonlinear multiple time scale systems. Then, a last contribution is introduced through the use of interval observer for the prognosis problem. A pronognosis methodology is proposed for nonlinear uncertain multiple time scale systems. To illustrate the theorical results, simulations are achieved based on a model of an electromechanical oscillator system.

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