This thesis investigates various active control aspects of large aperture telescopes; both Earth-based and space telescopes are considered.The first part proposes a concept of piezoelectric adaptive thin shell reflector for future space telescopes; it exhibits excellent areal density and stowability, and thus, paves the way to future large aperture space telescopes. Controlling the surface figure of spherical or parabolic shell with in-plane stresses induced by a piezoelectric layer raises two problems: (i) Doubly curved shells are significantly stiffer than flat plates (especially for the optical modes associated with hoop strains) and (ii) When using segmented electrodes with different voltages, the surface figure is subject to edge fluctuations with a characteristic length depending on the reflector curvature R_c and thickness t according to sqrt(R_ct). Accurate surface figure corrections require that the electrode size D_e satisfies D_e<sqrt(R_ct). This results in a very large number of electrodes, leading to ill-conditioning in the Jacobian matrix of the system; to solve this, a hierarchical approach is proposed to inverse the Jacobian, based on Saint-Venant's principle. This chapter also proposes a petal configuration which aims at reducing the hoop stiffness and improving the foldability of the reflector. A small scale technology demonstrator has been manufactured in the framework of the ESA-GSTP project Multilayer Adaptive Thin Shell Reflectors for Future Space Telescopes (MATS). The demonstrator includes a polymer substrate (PEEK) and a spin-coated PVDF-TrFE piezoelectric layer activated by independent electrodes; it is used to validate the manufacturing process and the independent actuation of the electrodes.The second part deals with control-structure interaction in flat deformable mirrors for Adaptive Optics. The problem arises because of the increasing size of AO mirrors, leading to lower resonance frequencies, and the control bandwidth requirements to achieve a good wavefront error compensation. This chapter studies the conditions for spillover instability and highlights the main parameters controlling the phenomenon: the ratio between the control bandwidth and the resonance frequency and the modal damping. Two methods for damping augmentation are discussed, one passive, using inductive shunting of piezoelectric elements, and the other active, using the wavefront sensor and the array of control actuators as a modal filter.The third part focuses on the field stabilization control of the tip/tilt mirror under wind disturbances of the E-ELT telescope (a distinctive feature of the E-ELT as compared to other smaller telescopes is that it will be a wind-limited instead of a seeing-limited telescope). A literature survey is conducted of the spectral content of the wind disturbances on large telescopes, with a special attention on the high frequency decay rate. The analysis confirms the adequacy of a decoupled design of the field stabilization (M5) control loop. However, the reaction torques necessary to control the tip/tilt mirror M5 have been found to depend critically on the asymptotic decay rate of the wind tilt disturbance. These torques act as a disturbance on the telescope structure and, if the wind disturbance does not decay fast enough with the frequency (a>-3), it may generate significant wavefront errors in the primary mirror M1, in a frequency range (30-100Hz) which may be difficult to eliminate by Adaptive Optics. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

Made available in DSpace on 2016-03-15T19:32:43Z (GMT). No. of bitstreams: 1 Carlos Cristiano Poltronieri.pdf: 1170540 bytes, checksum: cce966d18d021a91f5d58fb358a04766 (MD5) Previous issue date: 2012-08-15 / This study was aimed at investigating the internal controls in the Small and Medium-Size Enterprises (SMEs) of information technology. Responses were sought on: How adherent is the said SMEs to the conceptual framework proposed by COSO? Our assumptions were based on the studies conducted in other countries, which expatiated on the quality and effectiveness of internal controls. By adopting a qualitative method interviews were focus on those responsible financial statements of seven IT-Based SMEs in the region of Campinas. Of these, six had independent auditors. The research methodology used was content analysis, being operated through the Nvivo Sofware for Qualitative Analysis, Version 9. The results show eleven categories, with eighty-six units of meaning. Research suggests that internal control is perceived by those responsible for financial statements in IT-Based SMEs as instruments or operational processes, and, in many situations the control environment, among other aspects are left aside. The surveyed companies are seeking knowledge on the subject in consulting and literature. Two aspects indicate that a forward-looking strategy positively affect internal controls, a situation applicable to IT company in view of the instability of its existing operations and growth in a short time. Concerning the aspects proposed by COSO, most of the SMEs are adherent to the framework, however, in respect to actions of the board of directors, quality of information systems, existence of internal audit, these are still in the process of improvement or even lacking. / O estudo objetivou investigar os controles internos nas pequenas e médias empresas de tecnologia da informação. Buscaram-se respostas quanto à indagação: Quão aderente é a estrutura conceitual proposta por COSO às pequenas e médias empresas de TI? Partiu-se de pressupostos presentes em pesquisas realizadas em outros países, as quais estudaram qualidade e efetividade dos controles internos. Adotando-se um enfoque qualitativo foram realizadas entrevistas com responsáveis pelas áreas financeiras de sete pequenas e médias empresas de tecnologia da informação, sendo que dessas, seis possuem auditoria externa independente. A metodologia da pesquisa utilizada é a análise de conteúdo, sendo operacionalizada através do NVIVO, versão 9. Os resultados apresentam onze categorias, dentre as oitenta e seis unidades de significado. A pesquisa sugere que a percepção dos responsáveis pelos controles internos em pequenas e médias empresas de TI como instrumentos ou processos operacionais, sendo que, em muitas situações o ambiente de controle, entre outros aspectos são deixados de lado. As empresas pesquisadas buscam conhecimento sobre o assunto em consultorias e na literatura. Dois dos aspectos apontam que uma estratégia prospectiva influenciam positivamente os controles internos, uma situação aplicável as empresa de TI tendo em vista a instabilidade de suas operações e os crescimentos existentes em curto espaço de tempo. Dentre os aspectos propostos por COSO, os aspectos relacionados com a atuação do conselho de administração, qualidades dos sistemas de informação, existência de auditoria interna, ainda estão em fase de aprimoramento ou mesmo, ainda inexistentes.

Made available in DSpace on 2016-03-15T19:32:47Z (GMT). No. of bitstreams: 1 Jorge da Silva Krening.pdf: 839422 bytes, checksum: 55407cba3675d45dbd4436f048b32596 (MD5) Previous issue date: 2014-02-19 / Since its creation in the beginning of the nineteenth century, the credit union has played an essential role in the global economy. Due to actions based on the less favoured class in the past, the cooperatives have always embraced the idea of solidarity and unity, something that is deeply rooted in its principles. Throughout its history, there was the need for improvement, maturity and evolution in its way of managing and directing, mainly due to the big growth of the segment which occurred after the mid-1990. By having the financial intermediation as their main focus, the credit unions keep playing a fundamental role in the sustainable development of Brazil, particularly because of their ability to fund consumption and production. Some issues such as the huge dependence on the spread in order to cover operational costs, and also its vulnerabilities, contribute to make the cooperatives become less competitive if compared to the other institutions. Some particularities involving its structure and culture end up creating some conflicting interests, mainly among cooperative members (owners) and managers. In order to describe the legal structure that rules the credit unions in Brazil regarding the decision on the internal controls model, Resolution CMN 2.554/98 and Government Circular CMN 3.467/09 has been drawn up. Both are considered as clear and formal in the acceptance of conceptual structure COSO as internal controls framework. It is clear that the action of Central Bank of Brazil in following up the international trends that involve standardization through international recommendations imply in their compliance and observance. This study is aimed at investigating the acceptance by the credit unions of Sao Paolo state to the government Circular CMN 3.467/09. The answers to the matter have been searched: Are the cooperatives of Sao Paulo state checking the relevant aspects contained in the Government Circular CMN 3.467/09? By using qualitative and quantitative approaches, interviews and data colleting have been conducted through an electronic form on the internet. Using the qualitative approach, agents and people in charge of internal control were interviewed in 8 of a 159 credit unions affiliated to Sicoob Central Cecresp, since they have been considered as large ones if using the criteria established by this Central. By using the quantitative approach, the 151 cooperatives have received an electronic form. Based on the effected analysis, we conclude that the researched credit unions adopt the relevant and intrinsic aspects of Circular CMN 3.467/09. Through the quantitative analysis, it was possible to evidence the adherence of the control components. Finally, in the qualitative aspects, we perceive the need for a more involvement of the management particularly concerning question of control culture and formalizing policies and procedures. / Desde sua criação no início do século dezenove que o cooperativismo de crédito vem desempenhando papel fundamental na economia mundial. Apoiado em ações voltadas para uma classe menos favorecida no passado, o cooperativismo sempre empunhou a bandeira da solidariedade e união, algo enraizado de forma profunda em seus princípios. Durante sua trajetória, houve a necessidade de aprimoramento, amadurecimento e evolução da sua forma de gestão e administração, muito em função do grande crescimento do segmento, que ocorreu principalmente a partir de meados dos anos noventa. Tendo como foco principal a intermediação financeira, as cooperativas de crédito continuam exercendo um papel fundamental para o desenvolvimento sustentável do Brasil, muito em função da sua capacidade de financiar o consumo e a produção. Alguns problemas como a voraz dependência do spread para cobrir custos operacionais, e ainda, fragilidades inerentes, contribuem para que as cooperativas se tornem menos competitivas, comparado as demais instituições. Particularidades envolvendo sua estrutura e culturas acabam por gerar alguns conflitos de interesse, principalmente entre os cooperados (proprietários) e gestores. Para descrever o arcabouço legal que rege as cooperativas de crédito no Brasil no que tange à determinação do modelo de controles internos, recorre-se a Resolução CMN 2.554/98 e Circular CMN 3.467/09. Ambas são tidas como exemplos claros e formais da adoção da estrutura conceitual COSO como framework de controles internos. Ficam evidentes as ações do Banco Central do Brasil em acompanhar as tendências internacionais que envolvem padronização, através das recomendações internacionais, implicando seu cumprimento e observância. Esse estudo objetivou investigar a adoção pelas cooperativas de crédito do estado de São Paulo à Circular CMN 3.467/09. Buscaram-se respostas quanto à indagação: As cooperativas do estado de São Paulo estão observando os aspectos relevantes contidos na Circular CMN 3.467/09? Adotando-se um enfoque quantitativo e qualitativo, foram realizadas entrevistas e coleta de dados por meio de formulário eletrônico via web. De forma qualitativa foram entrevistados agentes e responsáveis pelos controles internos em oito das cento e cinquenta e nove cooperativas de crédito, filiadas a Sicoob Central Cecresp, por serem consideradas de grande porte, por critérios estabelecidos por esta Central. Com base nas análises efetuadas conclui-se que as cooperativas pesquisadas estão adotando os aspectos relevantes e intrínsecos contidos na Circular CMN 3.467/09. Através da análise, quantitativamente, foi possível estabelecer a aderência dos componentes de controle. Finalmente, dos aspectos qualitativos, percebe-se a necessidade de um maior envolvimento da administração, principalmente no quesito cultura de controle e formalização de políticas e procedimentos.

Yes / In this paper, a performance enhancement scheme has been investigated for a class of stochastic nonlinear systems via set-point adjustment. Considering the practical industrial processes, the multi-layer systematic structure has been adopted to achieve the control design requirements subjected to random noise. The basic loop control is given by PID design while the parameters have been fixed after the design phase. Alternatively, we can consider that there exists an unadjustable loop control. Then, the additional loop is designed for performance enhancement in terms of the tracking accuracy. In particular, a novel approach has been presented to dynamically adjust the set-points using the estimated states of the systems through extended Kalman filter (EKF). Minimising the entropy criterion, the parameters of the set-point adjustment controller can be optimised which will enhance the performance of the entire closed-loop systems. Based upon the presented scheme, the stochastic stability analysis has been given to demonstrate that the closed-loop tracking errors are bounded in probability one. To indicate the effectiveness of the presented control scheme, the numerical examples have been given and the simulation results imply that the designed systems are bounded and the tracking performance can be enhanced simultaneously. In summary, a new framework for system performance enhancement has been presented even if the loop control is unadjustable which forms the main contribution of this paper.

The problem of designing control systems for entire plants is studied. A review of previous works, available techniques and current research challenges is presented, followed by the description of some theoretical tools to improve plantwide control, including the proposal of an augmented lexicographic multi-objective optimization procedure. With these, an augmented hierarchical plantwide control design technique and an optimal multi-objective technique for integrated control structure selection and controller tuning are proposed. The main contributions of these proposed techniques are the inclusion of system identification and optimal control tuning as part of the plantwide design procedure for improved results, support to multi-objective control specifications and support to any type of plant and controllers. Finally, the proposed techniques are applied to industrial benchmarks to demonstrate and validate its applicability. / O problema de projetar sistemas de controle para plantas inteiras é estudado. Uma revisão de trabalhos anteriores, técnicas disponíveis e atuais desafios de pesquisa é apresentada, seguida da descrição de algumas ferramentas teóricas para melhorar o controle plantwide, incluindo a proposta de um procedimento de otimização multi-objetivo lexicográfico aumentado. Com tais elementos, são propostas uma nova técnica hierárquica aumentada de projeto de sistemas de controle plantwide e uma técnica multi-objetivo para seleção de estrutura de controlador integrada à sintonia ótima do controlador. As principais contribuições das técnicas propostas são a inclusão de identificação de sistemas e sintonia ótima de controladores como parte do procedimento de projeto de controle plantwide para melhores resultados, suporte a especificações multi-objetivo e suporte a quaisquer tipos de plantas e controladores. Finalmente, as técnicas propostas são aplicadas a benchmarks industriais para demonstrar e validar sua aplicabilidade.

Many control systems of practical importance are multivariable. In such systems, each manipulated variable (input signal) may affect several controlled variables (output signals) causing interaction between the input/output loops. For this reason, control of multivariable systems is typically much more difficult compared to the single-input single-output case. It is therefore of great importance to quantify the degree of interaction so that proper input/output pairings that minimize the impact of the interaction can be formed. For this, dedicated interaction measures can be used. The first part of this thesis treats interaction measures. The commonly used Relative Gain Array (RGA) is compared with the Gramian-based interaction measures the Hankel Interaction Index Array (HIIA) and the Participation Matrix (PM) which consider controllability and observability to quantify the impact each input signal has on each output signal. A similar measure based on the <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Cmathcal%20H_2" /> norm is also investigated. Further, bounds on the uncertainty of the HIIA and the PM in case of uncertain models are derived. It is also shown how the link between the PM and the Nyquist diagram can be utilized to numerically calculate such bounds. Input/output pairing strategies based on linear quadratic Gaussian (LQG) control are also suggested. The key idea is to design single-input single-output LQG controllers for each input/output pair and thereafter form closed-loop multivariable systems for each control configuration of interest. The performances of these are compared in terms of output variance. In the second part of the thesis, the activated sludge process, commonly found in the biological wastewater treatment step for nitrogen removal, is considered. Multivariable interactions present in this type of bioreactor are analysed with the tools discussed in the first part of the thesis. Furthermore, cost-efficient operation of the activated sludge process is investigated.

Abstract Energy production in combustion power plants is a significant source of anthropogenic carbon dioxide emissions. The targets of international climate agreements call for utilizing all available technologies to achieve rapid and cost-effective emission reductions. Carbon capture and storage is one of the possible technical solutions applied in combustion power plants. Circulating fluidized bed boilers have gained increasing popularity due to advantages in availability, emission control, fuel flexibility and option for using challenging fuels, and the possibility of using high-efficiency steam cycles. In the novel process of oxy-combustion, combustion air is replaced by a mixture of oxygen and recycled flue gas to facilitate the capture of carbon dioxide from the flue gas flow. Additional degrees of freedom become available for combustion control as the gas flow and composition can be controlled separately for fluidization and combustion purposes. In the research for this thesis, self-optimizing control was applied for the control structure design of a circulating fluidized bed boiler. Self-optimizing control offers a systematic tool for the early phases of control design, in which decisions have traditionally been made based on intuition, heuristics and previous experience. The self-optimizing control approach searches for controlled variables without a need for constant setpoint optimization when the process is affected by disturbances and implementation errors. Results presented in the thesis show that self-optimizing control can be applied in the control structure design of circulating fluidized bed combustion. A range of control structure alternatives were evaluated using steady-state approximations of a validated process model. For the novel oxy-combustion process, promising control structures were identified and could be dynamically demonstrated. / Tiivistelmä Energiantuotanto polttovoimalaitoksissa on merkittävä hiilidioksidipäästöjen lähde. Kansainväliset ilmastotavoitteet edellyttävät kaikkien käytettävissä olevien teknologioiden hyödyntämistä päästövähennysten aikaansaamiseksi nopeasti ja kustannustehokkaasti. Hiilidioksidin talteenotto on yksi mahdollisista teknisistä ratkaisuista polttovoimalaitoksissa. Kiertoleijukattilat ovat saavuttaneet kasvavaa suosiota etuinaan hyvä käytettävyys, tehokas päästöjen hallinta, soveltuvuus erilaisten haastavienkin polttoaineiden hyödyntämiseen ja mahdollisuus tehokkaiden höyrykiertojen käyttöön. Uudessa happipolttoprosessissa palamisilma korvataan hapen ja kierrätetyn savukaasun seoksella, mikä mahdollistaa hiilidioksidin talteenoton savukaasuista. Kiertoleijupolton säädön kannalta vapausasteet lisääntyvät, sillä leijutukseen ja polttamiseen käytettävän kaasun määrää ja koostumusta voidaan säätää erikseen. Väitöstutkimuksessa käytettiin itseoptimoivaa säätöä kiertoleijukattilan säätörakenteiden suunnitteluun. Itseoptimoiva säätö tarjoaa systemaattisen menetelmän säätösuunnittelun alkuvaiheeseen, jossa päätöksenteko on perinteisesti tehty esimerkiksi intuition, heuristiikan ja aiempien ratkaisujen perusteella. Menetelmän tavoitteena on löytää säädettävät muuttujat, joiden asetusarvot eivät vaadi jatkuvaa optimointia, vaikka prosessiin vaikuttavat erilaiset häiriöt ja mittausvirheet. Väitöstutkimuksen tulokset osoittavat, että itseoptimoiva säätö soveltuu kiertoleijupolton säätörakenteiden suunnitteluun. Erilaisten säätörakenteiden toimivuutta arvioitiin käyttäen validoidun prosessimallin tasapainotilan approksimaatioita. Uudelle happipolttoprosessille löydettiin lupaavia säätörakenteita, joiden toimintaa voitiin demonstroida myös dynaamisesti.

The thesis contains analysis of organization and control structure of the agricultural enterprise and analysis of some logistics branches such as material-flow, manipulation with material, storing and relation between customers and suppliers. According to the realized analyses, arrangements are suggested to solve problems and to improve the contemporary situation in analyzed branches.

The problem of designing control systems for entire plants is studied. A review of previous works, available techniques and current research challenges is presented, followed by the description of some theoretical tools to improve plantwide control, including the proposal of an augmented lexicographic multi-objective optimization procedure. With these, an augmented hierarchical plantwide control design technique and an optimal multi-objective technique for integrated control structure selection and controller tuning are proposed. The main contributions of these proposed techniques are the inclusion of system identification and optimal control tuning as part of the plantwide design procedure for improved results, support to multi-objective control specifications and support to any type of plant and controllers. Finally, the proposed techniques are applied to industrial benchmarks to demonstrate and validate its applicability. / O problema de projetar sistemas de controle para plantas inteiras é estudado. Uma revisão de trabalhos anteriores, técnicas disponíveis e atuais desafios de pesquisa é apresentada, seguida da descrição de algumas ferramentas teóricas para melhorar o controle plantwide, incluindo a proposta de um procedimento de otimização multi-objetivo lexicográfico aumentado. Com tais elementos, são propostas uma nova técnica hierárquica aumentada de projeto de sistemas de controle plantwide e uma técnica multi-objetivo para seleção de estrutura de controlador integrada à sintonia ótima do controlador. As principais contribuições das técnicas propostas são a inclusão de identificação de sistemas e sintonia ótima de controladores como parte do procedimento de projeto de controle plantwide para melhores resultados, suporte a especificações multi-objetivo e suporte a quaisquer tipos de plantas e controladores. Finalmente, as técnicas propostas são aplicadas a benchmarks industriais para demonstrar e validar sua aplicabilidade.

This report delves into the early developmental phase of an autonomous vehicle designed for defense applications. Navigating diverse terrains, this unmanned ground vehicle (UGV) poses unique challenges, particularly in the absence of clearly defined directives found in typical traffic scenarios. The analysis employs the Systems-Theoretic Process Analysis (STPA) to identify and anticipate risks inherent in the conceptual stage of product development. Beyond the specific UGV case, the report explores the broader landscape of validating autonomous systems. It discusses prevalent methods, emphasizing adaptability to different contexts and stages of development. By shedding light on the risks and challenges of autonomy in vehicles and examining effective validation strategies, this report aims to contribute valuable insights to the ongoing discourse surrounding autonomous vehicle development.