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Dynamic path following controllers for planar mobile robotsAkhtar, Adeel 13 October 2011 (has links)
In the field of mobile robotics, many applications require feedback control laws that provide perfect path following. Previous work has shown that transverse feedback linearization
is an effective approach to designing path following controllers that achieve perfect path following and path invariance. This thesis uses transverse feedback linearization and
augments it with dynamic extension to present a framework for designing path following controllers for certain kinematic models of mobile robots. This approach can be used to
design path following controllers for a large class of paths. While transverse feedback linearization makes the desired path attractive and invariant, dynamic extension allows the
closed-loop system to achieve the desired motion along the path. In particular, dynamic extension can be used to make the mobile robot track a desired velocity or acceleration
profile while moving along a path.
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Weapon-target Allocation And Scheduling For Air Defense With Time Varying Hit ProbabilitiesGulez, Taner 01 June 2007 (has links) (PDF)
In this thesis, mathematical modeling and heuristic approaches are developed for surface-to-air weapon-target allocation problem with time varying single shot hit probabilities (SSHP) against linearly approaching threats. First, a nonlinear mathematical model for the problem is formulated to maximize sum of the weighted survival probabilities of assets to be defended. Next, nonlinear objective function and constraints are linearized. Time varying SSHP values are approximated with appropriate closed forms and adapted to the linear model obtained. This model is tested on different scenarios and results are compared with those of the original nonlinear model. It is observed that the linear model is solved much faster than the nonlinear model and produces reasonably good solutions. It is inferred from the solutions of both models that engagements should be made as late as possible, when the threats are closer to the weapons, to have SSHP values higher. A construction heuristic is developed based on this scheme. An improvement heuristic that uses the solution of the construction heuristic is
also proposed. Finally, all methods are tested on forty defense scenarios. Two fastest solution methods, the linear model and the construction heuristic, are compared on a large scenario and proposed as appropriate solution techniques for
the weapon-target allocation problems.
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Linearization Of Rf Power Amplifiers With Memoryless Baseband Predistortion MethodKolcuoglu, Turusan 01 May 2011 (has links) (PDF)
In modern wireless communication systems, advanced modulation techniques are used to support more users by handling high data rates and to increase the utilization efficiency of the limited RF spectrum. These techniques are sensitive to the nonlinear distortions due to their high peak to average power ratios. Main source of nonlinear distortion in transmitter topologies are power amplifiers that determine the overall efficiency and linearity of the transmitter. To increase linearity without sacrificing efficiency, power amplifier linearization techniques may be a choice. Baseband predistortion technique is known to be one of the optimum methods due to its relatively low complexity and its convenience for adaptation. In this thesis, different memoryless baseband signal predistortion methods are investigated and analyzed by simulations. Look-Up Table(LUT) and Polynomial approaches are compared and LUT approach is found to be better in performance. Parameters, like indexing, training sequences and training duration are evaluated. An open loop testbench is built with a real amplifier and a different
LUT predistortion method that is based on amplifier modeling is offered. It is evaluated by using two tone test and adjacent channel power suppression with 8PSK data. Also, some
Look-Up Table parameters are re-investigated with the proposed method. The performances of the proposed method in dierent amplifier classes are observed. Along with these studies,
a list of prerequisites for design of a predistortion system is determined.
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Control of Unmanned Aerial Vehicles using Non-linear Dynamic Inversion / Design av styrlagar för obemannade farkoster med hjälp av exakt linjäriseringKarlsson, Mia January 2002 (has links)
<p>This master's thesis deals with the control design method called Non-linear Dynamic Inversion (NDI) and how it can be applied to Unmanned Aerial Vehicles (UAVs). In this thesis, simulations are conducted using a model for the unmanned aerial vehicle SHARC (Swedish Highly Advanced Research Configuration), which Saab AB is developing. </p><p>The idea with NDI is to cancel the non-linear dynamics and then the system can be controlled as a linear system. This design method needs much information about the system, or the output will not be as desired. Since it is impossible to know the exact mathematical model of a system, some kind of robust control theory is needed. In this thesis integral action is used. </p><p>A problem with NDI is that the mathematical model of a system is often very complex, which means that the controller also will be complex. Therefore, a controller that uses pure NDI is only discussed, and the simulations are instead based on approximations that use a cascaded NDI. Two such methods are investigated. One that uses much information from aerodata tables, and one that uses the derivatives of some measured outputs. Both methods generate satisfying results. The outputs from the second method are more oscillatory but the method is found to be more robust. If the signals are noisy, indications are that method one will be better.</p>
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Dynamic path following controllers for planar mobile robotsAkhtar, Adeel 13 October 2011 (has links)
In the field of mobile robotics, many applications require feedback control laws that provide perfect path following. Previous work has shown that transverse feedback linearization
is an effective approach to designing path following controllers that achieve perfect path following and path invariance. This thesis uses transverse feedback linearization and
augments it with dynamic extension to present a framework for designing path following controllers for certain kinematic models of mobile robots. This approach can be used to
design path following controllers for a large class of paths. While transverse feedback linearization makes the desired path attractive and invariant, dynamic extension allows the
closed-loop system to achieve the desired motion along the path. In particular, dynamic extension can be used to make the mobile robot track a desired velocity or acceleration
profile while moving along a path.
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Localisation d'une flotte de véhicules communicants par approche de type SLAM visuel décentralisé / Location of a fleet of communicating vehicles using a decentralized visual SLAM approachBresson, Guillaume 21 February 2014 (has links)
La localisation d’un véhicule via les techniques de SLAM (Simultaneous Localization And Mapping pour cartographie et localisation simultanées) a connu un essor important durant les 20 dernières années. Pourtant, peu d’approches ont tenté d’étendre ces algorithmes à une flotte de véhicules malgré les nombreuses applications potentielles. C’est ici l’objectif de cette thèse. Pour ce faire, une approche de SLAM monoculaire pour un seul véhicule a d’abord été développée. Celle-ci propose de coupler un filtre de Kalman étendu avec une représentation cartésienne des amers afin de produire des cartes de faible densité mais de qualité. En effet, l’extension à plusieurs véhicules nécessite des échanges permanents par l’intermédiaire de communications sans fil. Avec peu d’amers dans les cartes, notre approche s’accommode bien du nombre de véhicules de la flotte. Des capteurs peu onéreux ont aussi été privilégiés (une unique caméra et un odomètre) afin de réduire le coût d’une extension multivéhicule. Des correctifs ont été proposés afin d’éviter les problèmes de divergence induits par les choix précédents. Des expérimentations ont montré que la solution de SLAM produite était légère et rapide tout en fournissant une localisation de qualité. La dérive, inhérente à tout algorithme de SLAM, a également fait l’objet d’une analyse. Celle-ci a été intégrée au SLAM par l’intermédiaire d’une architecture dédiée et d’un modèle dynamique. Le but est de pouvoir rendre consistante la localisation fournie par le SLAM, même en l’absence d’estimation de la dérive. Cela permet d’effectuer des fermetures de boucle ou encore d’intégrer des informations géo-référencées de manière naturelle tout en conservant l’intégrité de la solution. En multivéhicule, cet aspect est un point clef puisque chaque véhicule dérive différemment des autres. Il est donc important de le prendre en compte. Enfin, le SLAM a été étendu à plusieurs véhicules. Une structure générique a été prévue afin que notre approche monoculaire puisse être remplacée par n’importe quel algorithme de SLAM. Notre architecture décentralisée évite la consanguinité des données (le fait de compter deux fois une même information) et gère les défaillances réseau, que cela soit des ruptures de communication ou encore des latences dans la réception des données. La partie statique du modèle de dérive permet également de prendre en compte le fait que les positions initiales des véhicules d’une flotte puissent être inconnues. L’intégrité est ainsi maintenue en permanence. Enfin, notre approche étant entièrement décentralisée, elle a pu être testée et validée en simulation et avec des expérimentations réelles dans diverses configurations (convoi en colonne ou en ligne, avec 2 ou 3 véhicules). / The localization of a vehicle with the use of SLAM techniques (Simultaneous Localization And Mapping) has been extensively studied during the last 20 years. However, only a few approaches have tried to extend these algorithms to a fleet of vehicles despite the many potential applications. It is the objective of this thesis. First of all, a monocular SLAM for a single vehicle has been developed. This one proposes to pair an Extended Kalman Filter with a Cartesian representation for landmarks so as to produce accurate low density maps. Indeed, the extension of SLAM to several vehicles requires permanent communications inside the fleet. With only a few landmarks mapped, our approach scales nicely with the number of vehicles. Cheap sensors have been favored (a single camera and an odometer) in order to spread more easily the use of multi-vehicle applications. Correctives have been proposed in order to avoid the divergence problems induced by such a scheme. The experiments showed that our SLAM is able to furnish good localization results while being light and fast.The drift affecting every SLAM algorithm has also been studied. Its integration inside the SLAM process, thanks to a dedicated architecture and a dynamic model, allows to ensure consistency even without an estimation of it. Loop closures or the integration of geo-referenced information becomes straightforward. They naturally correct all the past positions while still maintaining consistency. In a multi-vehicle scenario, it is a key aspect as each vehicle drifts differently from one another. It is consequently important to take it into account. Our SLAM algorithm has then been extended to several vehicles. A generic structure has been used so as to allow any SLAM algorithm to replace our monocular SLAM. The multi-vehicle architecture avoids data incest (double-counting information) and handles network failures, be they communication breakdowns or latencies when receiving data. The static part of the drift model allows to take into account the fact that the initial positions of the different vehicles composing the fleet might be unknown. Consistency is thus permanently preserved. Our approach has been successfully tested using simulations and real experiments with various settings (row or column convoy with 2 or 3 vehicles) in a fully decentralized way.
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Engine thermal management with model predictive controlAbdul-Jalal, Rifqi I. January 2016 (has links)
The global greenhouse gas CO2 emission from the transportation sector is very significant. To reduce this gas emission, EU has set an average target of not more than 95 CO2/km for new passenger cars by the year 2020. A great reduction is still required to achieve the CO2 emission target in 2020, and many different approaches are being considered. This thesis focuses on the thermal management of the engine as an area that promise significant improvement of fuel efficiency with relatively small changes. The review of the literature shows that thermal management can improve engine efficiency through the friction reduction, improved air-fuel mixing, reduced heat loss, increased engine volumetric efficiency, suppressed knock, reduce radiator fan speed and reduction of other toxic emissions such as CO, HC and NOx. Like heat loss and friction, most emissions can be reduced in high temperature condition, but this may lead to poor volumetric efficiency and make the engine more prone to knock. The temperature trade-off study is conducted in simulation using a GT-SUITE engine model coupled with the FE in-cylinder wall structure and cooling system. The result is a map of the best operating temperature over engine speed and load. To quantify the benefit of this map, eight driving styles from the legislative and research test cycles are being compared using an immediate application of the optimal temperature, and significant improvements are found for urban style driving, while operation at higher load (motorway style driving) shows only small efficiency gains. The fuel consumption saving predicted in the urban style of driving is more than 4%. This assess the chance of following the temperature set point over a cycle, the temperature reference is analysed for all eight types of drive cycles using autocorrelation, lag plot and power spectral density. The analysis consistently shows that the highest volatility is recorded in the Artemis Urban Drive Cycle: the autocorrelation disappears after only 5.4 seconds, while the power spectral density shows a drop off around 0.09Hz. This means fast control action is required to implement the optimal temperature before it changes again. Model Predictive Control (MPC) is an optimal controller with a receding horizon, and it is well known for its ability to handle multivariable control problems for linear systems with input and state limits. The MPC controller can anticipate future events and can take control actions accordingly, especially if disturbances are known in advance. The main difficulty when applying MPC to thermal management is the non-linearity caused by changes in flow rate. Manipulating both the water pump and valve improves the control authority, but it also amplifies the nonlinearity of the system. Common linearization approaches like Jacobian Linearization around one or several operating points are tested, by found to be only moderately successful. Instead, a novel approach is pursued using feedback linearization of the plant model. This uses an algebraic transformation of the plant inputs to turn the nonlinear systems dynamics into a fully or predominantly linear system. The MPC controller can work with the linear model, while the actual control inputs are found using an inverse transformation. The Feedback Linearization MPC of the cooling system model is implemented and testing using MathWork Simulink®. The process includes the model transformation approach, model fitting, the transformation of the constraints and the tuning of the MPC controller. The simulation shows good temperature tracking performance, and this demonstrates that a MPC controller with feedback linearization is a suitable approach to thermal management. The controller strategy is then validated in a test rig replicating an actual engine cooling system. The new MPC controller is again evaluated over the eight driving cycles. The average water pump speed is reduced by 9.1% compared to the conventional cooling system, while maintaining good temperature tracking. The controller performance further improves with future disturbance anticipation by 20.5% for the temperature tracking (calculated by RMSE), 6.8% reduction of the average water pump speed, 47.3% reduction of the average valve movement and 34.0% reduction of the average radiator fan speed.
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Controle não linear aplicado a malhas de controle com válvulas de alto atrito. / Nonlinear control applied to control loops with high friction valves.João Rostaizer Baeza 18 February 2013 (has links)
As válvulas de controle são elementos finais muito importantes na indústria de processos, pois são as responsáveis por controlar a pressão em dutos ou vazão dos fluidos de processo, impactando diretamente na qualidade do produto final. Por serem elementos mecânicos móveis estão sujeitas ao atrito, uma não linearidade que quando excessiva, pode causar oscilações e erros na abertura da válvula. A presença de oscilações nas malhas de controle aumenta a variabilidade das variáveis de processo, o desgaste dos componentes e o consumo de energia, além de provocar o desperdício de materiais. O desenvolvimento de novas técnicas de compensação de atrito é fundamental para melhorar o desempenho das malhas de controle, sendo, portanto, de grande interesse para a indústria de processos industriais. Este trabalho apresenta o estudo de cinco compensadores não lineares: controlador rastreador de trajetória, controlador por modos deslizantes, controlador por modos deslizantes integrador, controlador por modelo interno não linear e controlador PI não linear, os quais são desenvolvidos desde a teoria à implementação prática em uma válvula de controle real. Os resultados obtidos, mostram que os controladores projetados apresentaram desempenho bastante satisfatórios, sendo que o controlador por modos deslizantes e por modos deslizante integrador apresentaram os melhores desempenho. / Control valves are very important final elements in process industry, due they are the responsible to control the pressure in pipelines and the flow of the process fluids, directly impacting in the quality of the final product. Due to the mechanical mobile elements, they are subjected to friction, a nonlinearity that can generate oscillations and errors in the valve aperture. Oscillations in the control loops increase the process variability, wear in the actuators and the power consumption, besides generating raw material waste. The development of new friction compensation techniques is very important to increase the control loops performance, therefore, it is of great interest for the process industry. This work presents the study of five nonlinear compensators: Trajectory tracking controller, sliding mode controller, sliding mode controller integrator, nonlinear internal model controller and nonlinear PI controller, which ones are developed from theory to practical implementation in a real control valve. The results show that the controllers presented satisfactory performance, where the sliding mode controller and sliding mode control integrator presented the best performance.
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Linearization of a transmitter using an IC digital/analog cartesian feedback in 65nm CMOS for advanced communication standards / Linéarisation d'un émetteur mixte (analogique et numérique) utilisant une boucle cartésienne en technologie CMOS 65nm pour les communications mobiles avancéesDelaunay, Nicolas 20 December 2012 (has links)
Depuis la première génération de téléphone mobile, de nombreuses fonctions et outils ont été intégrés dans nos terminaux. Il y a vingt ans, nous utilisions nos téléphone pour émettre des appels et envoyer/recevoir des messages. Aujourd’hui, l’accès à internet, la radio, l’appareil photo, des jeux et de la musique sont des fonctionnalités que l’on retrouve dans nos téléphones mobiles.Dans un contexte de téléphonie pouvant adresse plusieurs standards, l’objectif de cette thèse est de concevoir et de réaliser l’implémentation d’une architecture capable d’améliorer la linéarité de notre émetteur pour le standard 3G, utilisant des composants analogiques et numériques. Pour cela, notre étude se concentrera sur l’amélioration de la linéarité, tout en maintenant une consommation la plus faible possible mais également tout en évitant d’augmenter la taille d’une puce 3G. Nous allons démontrer qu’il est possible d’intégrer une technique de linéarisation tout en maintenant une consommation et une surface en silicium.Le premier chapitre présente différentes architectures d’émetteurs et des techniques de linéarisation avec leurs avantages et inconvénients. Il est également présenté des moyens d’évaluer l’efficacité d’un émetteur par des simulations ou des mesures. L’objectif de cette partie est de choisir une technique de linéarisation à laquelle nous associerons une architecture d’émetteur afin de répondre le plus rigoureusement à notre application et ces contraintes émanant.Le second chapitre détaille le fonctionnement du système complet, la partie numérique et la partie analogique, s’appuyant sur des études théoriques. Nous commencerons en détaillant les contraintes et les précautions qui doivent être prises en compte par le concepteur afin d’étudier l’instabilité et le bruit produit par l’émetteur. Nous décrierons alors deux algorithmes numériques permettant de réaliser la correction des signaux. Des simulations au niveau système de la boucle Cartésienne seront également présenté utilisant, dans un premier temps un amplificateur de puissance idéal, pour ensuite utilisé un amplificateur de puissance réalisé en technologie BiCMOS, et finalement un amplificateur de puissance conçu en technologie CMOS, qui est celle choisie pour notre étude.Le troisième chapitre présente la synthèse de la partie numérique en technologie CMOS des deux algorithmes précédemment cités, elle prend en compte toutes les étapes ; du code VHDL jusqu’au layout, permettant de réaliser un circuit numérique. Ensuite, il est décrit chaque composant de la boucle cartésienne, avec leurs propres simulations ou mesures. De plus, il est important de garder à l’esprit que l’objectif de cette thèse repose sur l’intégration du système complet (partie analogique et numérique) en technologie CMOS 65nm de STMicroelectronics, démontrant ainsi la faisabilité de la solution.Dans un premier temps, nous décrirons la partie numérique permettant de réaliser les étapes de correction de phase et de soustraction des signaux en technologie ASIC. L’algorithme de CORDIC a pour avantage de minimiser la consommation et l’occupation en Silicium de la partie analogique. Par la suite, l’architecture et les spécifications de chaque brique de base constituant la partie analogique seront présentées. Dans notre cas, la chaîne directe est composée de filtres, de mélangeurs, et d'un amplificateur de puissance. Notre objectif est de réaliser ces trois fonctions avec le minium de consommation et une surface du circuit la plus faible possible, ceci permettant une intégration plus aisée.Finalement, les simulations système seront présentées utilisant le logiciel de simulation ADC (Advanced Design Software) d’Agilent pour la partie analogique. Des co-simulations ont été réalisées sur le système complet, utilisant SystemVue pour la partie numérique. Les simulations réalisant ADS nous ont fourni les performances de chaque brique de base s’appuyant sur les caractéristiques des transistors. / Since the first generation of mobile phones, a lot of functions, standards and tools have been integrated on handsets. Twenty years ago, consumers could use their mobile phones only to call and to send messages. Nowadays, internet access, radio, cameras, games and music are included and available as options for every mobile phone.All of these new services make the cost of production for a cellular phone more expensive. Despite that, industry has to find a solution to maintain their products the most attractive as possible including the large range of integrated functions.In the context of interaction with other standards, the aim of this thesis is to design and implement a chipset able to improve the linearity of a transmitter for third generation mobile phones, using both digital and analog technologies. For this purpose, the study will focus on the improvement of the linearity, keeping the consumption and the die area of the circuit as small as possible. We will prove that linearization on an integrated circuit is possible with almost the same consumption and die area occupation compared to a classic transmitter.The first chapter presents the different architectures used for a transmitter and various linearization techniques with their advantages and drawbacks. Some metrics are also presented in order to evaluate these architectures. The goal of this part is to choose a linearization technique associated to a transmitter in order to fit with our application and constraints.The second chapter explains the complete system, digital and analog parts, with theoretical studies. We will start by detailing the constraints and precautions that must be taken into account by the designer to study the instability and the noise generated by the transmitter. We will describe how two algorithms make signal corrections. In the last part we will show system level simulations of the Cartesian Feedback using, first, an ideal power amplifier (PA), then, a PA in a BiCMOS technology, and finally, a PA in a CMOS technology that will be used for the final integrated circuit.The third and last chapter shows the digital synthesis in a CMOS technology of the two algorithms previously mentioned, considering all steps, from the VHDL code until the layout of the digital part. We will describe and simulate each analog building block of the Cartesian Feedback, with the measurement results for some of them. Each chapter will be working towards the goal of this study, demonstrated in this part: to make an integrated system, with its complete solution and simulations.This chapter presents the integration of the analog and digital Cartesian Feedback described previously in 65nm CMOS technology from STMicroelectronics. First, the digital part generating the phase correction and subtraction will be shown in ASIC technology, with a CORDIC algorithm to reduce its consumption and size. Secondly, the architecture and specification of building blocks will be shown. In our case, the direct path is composed of filters, RF modulator and a Power Amplifier. Our objective is to design these three functions to minimize the consumption and the silicon area of the integrated architecture. Finally, system level simulations will be presented using the ADS (Advanced Design Software) from Agilent for the analog part. Co-simulations have been done to analyze the whole system, with SystemVue for the digital part. The simulations using ADS will provide the performance of each building block on the transistors level.
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[en] A COMPARATIVE STUDY OF METHODOLOGIES FOR MODELLING COMPLEX SURVEYS MODELLING - AN APPLICATION TO SAEB 99 / [es] UN ESTUDIO COMPARATIVO DE LAS METODOLOGÍAS DE MODELAJE DE DATOS PROVENIENTES DE MUESTREOS COMPLEJOS UNA APLICACIÓN AL SAEB 99 / [pt] UM ESTUDO COMPARATIVO DAS METODOLOGIAS DE MODELAGEM DE DADOS AMOSTRAIS COMPLEXOS - UMA APLICAÇÃO AO SAEB 99MARCEL DE TOLEDO VIEIRA 23 July 2001 (has links)
[pt] A consideração do desenho amostral é fundamental e
indispensável em trabalhos que têm como objetivo a análise
e modelagem de dados selecionados através de desenhos
amostrais complexos. Desta forma torna-se possível a
produção de resultados realmente úteis e confiáveis para os
gestores de políticas públicas. O principal objetivo desta
dissertação é chamar a atenção para a importância da
utilização das técnicas adequadas ao tratamento de
dados amostrais complexos, discutindo também as
conseqüências de sua não adoção. As metodologias adequadas
para a análise de dados amostrais complexos podem ser
agrupadas em duas abordagens. A primeira, denominada de
abordagem agregada, se baseia na incorporação de pesos e
efeitos do plano amostral no ajuste dos modelos
estatísticos. Através da outra abordagem, que é denominada
de abordagem desagregada, a lógica de modelagem é
modificada, incorporando os efeitos devidos à amostragem
complexa. Isto pode ser feito através do uso de modelos
lineares hierárquicos, ou multinível. Os dados analisados
nesta dissertação foram coletados pelo Sistema Nacional de
Avaliação da Educação Básica (SAEB) no ano de 1999. Esta
pesquisa compreende um exame de conhecimentos e um
levantamento sobre condições sócio-econômico-demográficas
de mais de 200.000 alunos, suas escolas, professores e
diretores. A amostra do SAEB 99 foi selecionada a partir de
um plano amostral complexo. O desenho amostral do SAEB 99
considera amostragem aleatória estratificada de unidades
conglomeradas, com múltiplas etapas. A estimação pontual de
estatísticas descritivas a partir de dados amostrais
complexos não apresenta grandes dificuldades na medida em
que se utiliza de forma adequada os pesos na expansão da
amostra. Será ilustrada, através de um exemplo, a
importância dos pesos amostrais na estimação. Será
verificado que sua não adoção no cálculo da média, na
situação em questão, poderia gerar resultados
superestimados. Nesta dissertação serão apresentados
aspectos teóricos das técnicas (adequadas a dados amostrais
complexos) de estimação pontual de parâmetros de modelos de
regressão e de suas respectivas variâncias. Também é
realizada uma discussão sobre o efeito do plano amostral,
intervalos de confiança e testes de hipóteses, e sobre o
pacote SUDAAN. Serão apresentados os resultados da
aplicação das técnicas estudadas. Paralelamente, será
conduzido um estudo dos determinantes da proficiência dos
alunos. Ainda, serão apresentadas e analisadas as
conseqüências de não se considerar o desenho amostral na
estimação dos parâmetros dos modelos e de suas respectivas
variâncias, para o SAEB 99. Será realizada uma
interpretação educacional dos resultados apresentados. / [en] It is very important to consider the sample design in the
analysis and modelling of complex survey data. It permits
the production of correct results, which can be used for
public political decision making and evaluation. The main
objective of this dissertation is to give information about
the importance of the use of the techniques for complex
survey data. The methodologies for complex survey data
analysis can be divided in two different approaches. The
first is based on incorporating weights and design effects
in the fitting of usual statistical models, such as
contingency tables, regression, etc. This approach is called
aggregated approach. The other approach, called
disaggregated approach, modifies the model attempting to
incorporate the complex population structure and/or design
effects, for example using hierarchical (or multilevel)
linear models. The data analysed in this dissertation were
collected by the Brazilian National System of Basic
Education Assessment (SAEB), in 1999. This survey applies
an exam and asks social-economic-demographic information
about more than 200.000 students, schools and teachers. The
SAEB 99 sample were selected by a complex survey design,
considering stratification and conglomeration, with
multiples steps. There is not any problem in estimation of
descriptive statistics, such as means, correlation and
regression coefficients, provided that we correctly use the
sample weights to expand the data. An example will be
presented to verify the importance of the use of the
sample weights. The theoretical aspects of the techniques
for the estimation of regression model parameters and their
variances will be presented. The design effect, confidence
intervals, significance tests, and SUDAAN characteristics
will also be discussed. The application of these techniques
will be presented. It will be also conducted a study
of the determinants of the student proficiency. It still
will be presented and analysed the consequences of the non-
consideration of the sample design in the estimation of
parameters and their variances, for SAEB 99 data. The
results will be educationally interpreted. / [es] La consideración del diseño muestral es fundamental e
indispensable en trabajos que tienen como objetivo el
análisis y modelaje de datos selecionados a través de
diseños muestrales complejos. De esta forma es posible la
producción de resultados realmente útiles y confiables para
los gestores de políticas públicas. EL objetivo principal
de esta disertación es llamar la atención para la
importancia de la utilización de las técnicas adecuadas al
tratamiento de datos muestrales complejos, discutiendo
también las consecuencias de no adoptarlas. Las
metodologías adecuadas para el análisis de datos muestrales
complejos pueden ser agrupadas en dos abordajes. La
primera, denominada de abordaje agregado, consiste en la
incorporación de pesos y efectos del plano muestral en el
ajuste de los modelos estadísticos. A través del otro
abordaje, denominado de abordaje desagregado, se modifica
la lógica, incorporando los efectos debidos al muestreo
complejo. Esto puede realizarse a través del uso de modelos
lineales jerárquicos, o multiníveles. Los datos analizados
en esta disertación fueron colectados por el Sistema
Nacional de Evaluación de la Educación Básica (SAEB) en el
año de 1999. Esta investigación comprende un exámen de
conocimientos y un levantamiento sobre condiciones
socioeconómicas-demográficas de más de 200.000 alumnos, sus
escuelas, profesores y directores. La muestra del SAEB 99
fue seleccionada a partir de un diseño muestral complejo.
El diseño muestral del SAEB 99 considera el muestreo
aleatório estratificado de unidades conglomeradas, con
múltiples etapas. La estimación puntual de estadísticas
descriptivas a partir de datos muestrales complejos no
presenta grandes dificuldades si se utiliza de forma
adecuada los pesos en la expansión de la muestra. Se
ilustrará, a través de un ejemplo, la importancia de los
pesos muestrales en la estimación. Será verificado que la
no adopción de estos pesos en el cálculo de la media,
podería generar resultados superestimados. En esta
disertación serán presentados aspectos teóricos de las
técnicas (adecuadas a datos de muestras complejas) de
estimación puntual de parámetros de modelos de regresión y
de sus respectivas varianzas. Se discute también el efecto
del diseño muestral, intervalos de confianza y testes de
hipótesis, y el paquete SUDAAN. Serán presentados los
resultados de la aplicación de las técnicas estudiadas.
Paralelamente, se estudian los determinantes de la
proficiencia de los alumnos. Se presentan y analizan
también, las consecuencias de no considerar el diseño
muestral en la estimación de los parámetros del modelos y
de sus respectivas varianzas, para el SAEB 99. Será
realizada una interpretación educacional de los resultados
presentados.
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