abstract: In this dissertation, we present a H-infinity based multivariable control design methodology that can be used to systematically address design specifications at distinct feedback loop-breaking points. It is well understood that for multivariable systems, obtaining good/acceptable closed loop properties at one loop-breaking point does not mean the same at another. This is especially true for multivariable systems that are ill-conditioned (having high condition number and/or relative gain array and/or scaled condition number). We analyze the tradeoffs involved in shaping closed loop properties at these distinct loop-breaking points and illustrate through examples the existence of pareto optimal points associated with them. Further, we study the limitations and tradeoffs associated with shaping the properties in the presence of right half plane poles/zeros, limited available bandwidth and peak time-domain constraints. To address the above tradeoffs, we present a methodology for designing multiobjective constrained H-infinity based controllers, called Generalized Mixed Sensitivity (GMS), to effectively and efficiently shape properties at distinct loop-breaking points. The methodology accommodates a broad class of convex frequency- and time-domain design specifications. This is accomplished by exploiting the Youla-Jabr-Bongiorno-Kucera parameterization that transforms the nonlinear problem in the controller to an affine one in the Youla et al. parameter. Basis parameters that result in efficient approximation (using lesser number of basis terms) of the infinite-dimensional parameter are studied. Three state-of-the-art subgradient-based non-differentiable constrained convex optimization solvers, namely Analytic Center Cutting Plane Method (ACCPM), Kelley's CPM and SolvOpt are implemented and compared. The above approach is used to design controllers for and tradeoff between several control properties of longitudinal dynamics of 3-DOF Hypersonic vehicle model -– one that is unstable, non-minimum phase and possesses significant coupling between channels. A hierarchical inner-outer loop control architecture is used to exploit additional feedback information in order to significantly help in making reasonable tradeoffs between properties at distinct loop-breaking points. The methodology is shown to generate very good designs –- designs that would be difficult to obtain without our presented methodology. Critical control tradeoffs associated are studied and compared with other design methods (e.g., classically motivated, standard mixed sensitivity) to further illustrate its power and transparency. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2018

Made available in DSpace on 2016-04-26T20:24:16Z (GMT). No. of bitstreams: 1 Debora de Assis Pacheco Andrade.pdf: 1091471 bytes, checksum: f9f98737623e336f649988b3efc20f8b (MD5) Previous issue date: 2016-03-03 / This study analyzes whether the external control exercised by the Brazilian Federal Court of Auditors (Tribunal de Contas da União) on administrative contracts is within its constitutional and infra constitutional competences. The analysis of cases judged the by Brazilian Federal Court of Auditors in the last five years shows that their practice is not fully consistent with the constitutional and legal basis, basically due to the following evidence: decisions on such matters which go beyond the financial-budget issue; which review discretionary choices of the public administrator and that interfere in contractual arrangements concluded between the public authorities and the private parties. Indeed, it was noted that the Brazilian Federal Court of Auditors, imbued with the relevant mission to protect the public treasury and to contribute to the improvement of public administration, has expanded its activities beyond the examination of accounts, trespassing exclusive competes of the executive and legislative powers. On the other hand, a tendency to approximate the public administrator and the contracted party was noted in the Brazilian Federal Court of Auditors, revealing a change in its institutional nature marked by a punitive character to a conciliatory and collaborative approach. This shift in the focus of the Brazilian Federal Court of Auditors can operate as an important inducer of the national economic development, as long as limited to matters within its jurisdiction and respecting administrative choices / O presente estudo avalia se o controle exercido pelo Tribunal de Contas da União sobre os contratos administrativos encontra guarida nas suas competências constitucionais e infraconstitucionais. A análise de julgados prolatados pelo Tribunal de Contas da União nos cinco últimos anos revela que a sua atuação não se coaduna plenamente com as bases constitucionais e legais, em virtude, basicamente, das seguintes evidências: decisões que recaem sobre matéria que extrapolam a temática financeiro-orçamentária; que revisam escolhas discricionárias feitas pelo administrador público e que interferem em cláusulas contratuais celebradas entre o Poder Público e o particular. Com efeito, notou-se que o Tribunal de Contas da União, imbuído da relevante missão de salvaguardar o patrimônio público e de contribuir para o aprimoramento da gestão pública, expandiu a sua atuação para além do exame das contas, invadindo esferas que competem exclusivamente aos Poderes Executivo e Legislativo. Por outro lado, notou-se haver no Tribunal de Contas da União uma tendência de se aproximar do administrador público e do contratado, revelando uma alteração na sua natureza institucional, marcada pelo caráter sancionatório, para uma postura conciliadora e colaborativa. Essa mudança no eixo de atuação do Tribunal de Contas da União, se adstrita às matérias da sua jurisdição e respeitadas as escolhas administrativas, pode operar como um importante indutor do desenvolvimento econômico nacional