<p> This study is a search for an analytical framework within which the structural factors constraining the Nigerian development process can be highlighted.</p> <p>We examine the input-output method and its relationship to planning a less developed country. The input-output table available for Nigeria is analysed using conventional techniques. Certain indices are derived in an attempt to throw some light on the evaluation of the development process. 'Ihe importance of designing an input-output table within the context of the particular problem to be solved is emphasized. </p> <p> A comparative analysis is made of the Nigerian table and an input-output table for Zambia, to highlight the relationship between the design and the use of an input-output table in the planning process. Furthermore, the elements involved in designing a table that would come to grips with the question of structural transformation, are discerned. In particular, the need to relate the classification of economic activities in an input-output matrix to the planning problem emerges.</p> <p> The data provided in the Nigerian table are used to illustrate the sort of basis on which an input-output table could be built if there is to be a link between a formal description of the economy and the simulation of change.</p> <p> The study illustrates the extent to which the development process depends on the planners' recognition of the relationship between the problem of transformation and the nature of structural constraints in the economy. In this way, it is possible to isolate systemic malfunctions in the economy and identify in connection with these, the areas of weakness in the planning process.</p> <p> It is also seen that if the input-output model is to be useful in planning structural transfoTmation, it must be able to accommodate radical changes in the structure of production and a normatively determined pattern of demand. The scope of the conventional model must be broadened to allow the planner to emphasize target groups of people in relating the structure of production to the pattern of demand.</p> / Thesis / Doctor of Philosophy (PhD)

No description available.

Conditions under which compositions of component systems form a well-defined system-of-systems are here formulated at a fundamental level. Statement of what defines a well-defined composition and sufficient conditions guaranteeing such a result offers insight into exemplars that can be found in special cases such as differential equation and discrete event systems. For any given global state of a composition, two requirements can be stated informally as: (1) the system can leave this state, i.e., there is at least one trajectory defined that starts from the state; and (2) the trajectory evolves over time without getting stuck at a point in time. Considered for every global state, these conditions determine whether the resultant is a well-defined system and, if so, whether it is non-deterministic or deterministic. We formulate these questions within the framework of iterative specifications for mathematical system models that are shown to be behaviorally equivalent to the Discrete Event System Specification (DEVS) formalism. This formalization supports definitions and proofs of the afore-mentioned conditions. Implications are drawn at the fundamental level of existence where the emergence of a system from an assemblage of components can be characterized. We focus on systems with feedback coupling where existence and uniqueness of solutions is problematic.

Šiame darbe analizuojamos pasaulinio semantinio tinklo technologijos dalykinės srities žinioms užrašyti ir valdyti. Darbo metu buvo papildyta dalykinės srities ontologija bei sukurta nauja sistėminė vartotojo sąsajos formavimo ontologija, kuri palaiko daugiakalbystę. Realizuotos ir aprobuotos užklausos ir automatizavimo procesai dirbantys su minėtomis ontologijomis. Darbo vykdymo metu sukauptos žinios buvo surinktos, susistemintos ir pateikiamos kaip darbo metodika. Remiantis šia metodika sukurta eksperimentinė sistema, skirta padėti identifikuoti su BIOS klaidomis susijusias problemas ir/arba operacinių sistemų (OS) sutrikimo priežastis ir jas spręsti. Apie sukurtą sistemą buvo perskaitytas pranešimas konferencijoje „Mokslas ir studijos 2010: teorija ir praktika“, kuri įvyko Šiaurės Lietuvos kolegijoje. Metodiką galima pritaikyti bet kokiai dalykinei sričiai, tiek realizuojant e-mokymo(si) sistemose probleminio mokymosi principus, tiek paramos paslaugų teikimo prekės ar produkto vartotojui sferoje. / This work examines the global semantic web technologies in the subject area knowledge and record management. Work was completed in the subject area and Ontology, a new user interface making systemic ontology, which supports multilingualism. Realized and dealer inquiries, and automate processes in working with these ontologies. Work during the accumulated knowledge has been collected, systematised and presented as a working methodology. Based on the methodology developed an experimental system designed to help identify errors in the BIOS-related problems and / or operating systems (OS) and cause disruption to solve them. This system of notification was read in the conference of "Education and training 2010: Theory and Practice", which took place in Northern Lithuania College. The approach can be applied to any subject area, and implement e-learning (learning) problem of learning the principles of systems and support services or goods to the consumer product area.

The integration of Multiple Input Multiple Output (MIMO) and Orthogonal Frequency Division Multiplexing (OFDM) techniques has become a preferred solution for the high rate wireless technologies due to its high spectral efficiency, robustness to frequency selective fading, increased diversity gain, and enhanced system capacity. The main drawback of OFDM-based systems is their susceptibility to impairments such as Carrier Frequency Offset (CFO), Sampling Frequency Offset (SFO), Symbol Timing Error (STE), Phase Noise (PHN), and fading channel. These impairments, if not properly estimated and compensated, degrade the performance of the OFDM-based systems In this thesis, a system model for MIMO-OFDM that takes into account the effects of all these impairments is formulated. Using this system model, we de-rive Cramer-Rao Lower Bounds (CRLBs) for the joint estimation of deterministic impairments in MIMO-OFDM system, which show the coupling effect among different impairments and the significance of the joint estimation. Also, Bayesian CRLBs for the joint estimation of random impairments in OFDM system are derived. Similarly, we derive Hybrid CRLBs for the joint estimation of random and deterministic impairments in OFDM system, which show the significance of using Bayesian approach in estimation. Further, we investigate different algorithms for the joint estimation of all impairments in OFDM-based system. Maximum Likelihood (ML) algorithms and its low complexity variants, for the joint estimation of CFO, SFO, STE, and channel in MIMO-OFDM system, are proposed. We propose a low complexity ML algorithm which uses Compressed Sensing (CS) based channel estimation method in a sparse fading sce-nario, where the received samples used for estimation are less than that required for a Least Squares (LS) or Maximum a posteriori (MAP) based estimation. Also, we propose MAP algorithms for the joint estimation of the random impairments, PHN and channel, utilizing their statistical knowledge which is known a priori. Joint estimation algorithms for SFO and channel in OFDM system, using Bayesian framework, are also proposed in this thesis. The performance of the estimation methods is studied through simulations and numerical results show that the performance of the proposed algorithms is better than existing algorithms and is closer to the derived CRLBs.

Elektrohydraulische Steuerungen mit getrennten Steuerkanten stellen komplexe, mechatronische Systeme dar, welche durch ein enges Zusammenspiel der beteiligten Komponenten, ihrer strukturellen Anordnung, der notwendigen Sensorik und Elektronik, sowie den funktionsgebenden Algorithmen charakterisiert sind. Die vielfältigen Umsetzungsvarianten in den jeweiligen Gebieten und speziell im Bereich der Steuer- und Regelalgorithmen erschweren eine zielgerichtete Entwicklung, Bewertung und Auswahl. Neben ökonomischen Randbedingungen bildet vor allem eine beherrschbare Komplexität der Steuerungen, im Sinne der Robustheit und Handhabbarkeit, ein wesentliches Merkmal. Im Kern der Arbeit steht die Frage, welche Systemarchitektur für eine spezifische Maschinen- bzw. Arbeitsaufgabe aus Funktions- und Effizienzsicht optimale Eigenschaften aufweist. Dafür ist es notwendig, den Betrachtungsraum über alle Hierarchieebenen hinweg mit ihren jeweiligen Abhängigkeiten zu berücksichtigen. Ein strukturierter und iterativer Entwicklungsprozess, welcher dieWechselwirkungen der Einzellösungen frühzeitig einbezieht, dient dabei als Vorgehensmodell. In jeder Ebene sind Synthese,Analyse und Validierungsschritte notwendig, um die resultierenden Systemeigenschaften bewerten zu können. Ein Schwerpunkt liegt dabei auf einer Einbindung der Steueralgorithmen und einem stufenweisen Test mithilfe simulativer und experimenteller Untersuchungen. Die vorliegende Arbeit stellt eine Struktur- und Schaltungssystematik, zur zielgerichteten Ableitung von Strukturvarianten unter Berücksichtigung der Art und Anordnung der beteiligten Komponenten, zur Verfügung. Für die als Grundstruktur oder Basiskonfiguration bezeichnete Systemvariante, bestehend aus vier proportional verstellbaren Einzelwiderständen in Brückenanordnung, erfolgt eine regelungstechnische Analyse des vorliegenden Mehrgrößensystems. Zusätzlich zum Streckenverhalten (offene Steuerkette) ist das resultierende Verhalten der Kombination Strecke und Steuerung von Interesse. Den Schwerpunkt bilden insbesondere die Analyse des Führungs- und Störverhaltens, sowie die Kopplungseigenschaften des resultierenden Gesamtsystems. Um das funktionale Verhalten der gewählten System- und Steuerungsstruktur tiefgreifender analysieren und ihre Funktionsfähigkeit nachzuweisen zu können, wird ein Labordemonstrator in Form eines Baggerarmprüfstandes genutzt. Hierbei erfolgen jeweils eine virtuelle Untersuchung in einer Systemsimulationsumgebung, als auch der messtechnische Nachweis. Ein analoges Vorgehen wird für die Untersuchung des funktional-energetischen Verhaltens im Gesamtmaschinenkontext gewählt. Das simulativ ermittelte und optimierte Verhalten wird durch umfangreiche Untersuchungen am Maschinendemonstrator, im Rahmen von Maschinenmessungen verifiziert. Die dabei gewonnen Erkenntnisse dienen als Randbedingungen für eine weitreichende simulationstechnische Gegenüberstellung mit alternativen Antriebstechnologien. Erst diese Maßnahme ermöglicht die Einordnung der erzielten Ergebnisse des Untersuchungssystems.:1 Einleitung 1 2 Stand der Wissenschaft und Technik 3 2.1 Aufbau und Funktionsweise von Erdbaumaschinen 3 2.2 Steuerungssysteme mobiler Arbeitsmaschinen 6 2.2.1 Ventilgesteuerte Systeme in Open-Center Ausführung 9 2.2.2 Ventilgesteuerte Systeme in Closed-Center Ausführung 11 2.2.3 Verdrängergesteuerte Systeme 15 2.2.4 Hydraulische Hybridsysteme 18 2.3 Systeme mit getrennten Steuerkanten 21 2.3.1 Ventilstrukturen und Betriebsmodi 22 2.3.2 Aufbau und Funktionsweise proportionaler Sitzventile 28 2.3.3 Steuerungs- und Regelungskonzepte 31 3 Motivation und Zielsetzung 38 4 Entwurf und Systematisierung von Schaltungsvarianten 41 4.1 Methodik im Systementwurf 42 4.2 Varianten der Ventilstrukturen 45 4.3 Varianten der Ventilsteuerung 51 4.4 Varianten der Versorgungs- und Gesamtsysteme 53 5 Übertragungseigenschaften von Mehrgrößensystemen 58 5.1 Charakterisierung Mehrgrößenbegriff 58 5.2 Mathematische Beschreibung des ventilgesteuerten Zylinderantriebs 62 5.3 Herleitung des nichtlinearen, modellbasierten Vorsteuergesetzes 71 5.4 Analyse Zusammenhänge in Mehrgrößensystemen 74 5.4.1 Analyse des statischen Koppelfaktors 76 5.4.2 Analyse der dynamischen Kopplungseigenschaften 80 6 Untersuchungen am Labordemonstrator 87 6.1 Struktur und Aufbau des Labordemonstrators 87 6.2 Untersuchungsmethodik 89 6.3 Modellentwicklung des Labordemonstrators 92 6.3.1 Modellierung der Ausrüstungsmechanik und Prozessbelastung 93 6.3.2 Modellierung des Antriebssystems 95 6.3.3 Umsetzung der Ansteuerung - Software in the Loop 97 6.4 Validierung des Gesamtantriebsmodells 98 6.5 Beschreibung und Analyse der Steuerung 100 6.5.1 Statisches Verhalten im Einzelverbraucherbetrieb 103 6.5.2 Dynamisches Verhalten im Einzelverbraucherbetrieb 105 6.5.3 Statisches Verhalten im Mehrverbraucherbetrieb 108 6.5.4 Dynamisches Verhalten im Mehrverbraucherbetrieb 110 6.6 Zusammenfassung und Bewertung 114 7 Integration und Funktionstest am Maschinendemonstrator 115 7.1 Aufbau und Funktionsweise des Standardantriebssystem 116 7.2 Entwicklung und Integration des Antriebsprototyps 121 7.3 Modellentwicklung des Maschinendemonstrators 130 7.3.1 Ausrüstungs- und Fahrzeugmechanik 131 7.3.2 Verbrennungsmotor 133 7.3.3 Verstellpumpen 135 7.3.4 Steuerventile 136 7.3.5 Proportional-Sitzventil 137 7.3.6 Drehwerkssteuerung 139 7.4 Validierung und simulative Erprobung des des Gesamtsystems 140 7.5 Experimentelle Erprobung und Analyse des GSK-Systems 149 7.6 Zusammenfassung und Bewertung 157 8 Modellgestützte Analyse und Vergleich der Energieeffizienz 159 8.1 Modellgestützte Effizienzanalyse in mobilen Arbeitsmaschinen 159 8.1.1 Vollständige Zyklenspiele 161 8.1.2 Standardzyklus 164 8.1.3 Äquivalente Referenzzyklen 165 8.1.4 Fazit 166 8.2 Entwicklung und Beschreibung von Antriebssystemvarianten 168 8.2.1 Mehrkreis Drosselsteuerung 3K-OC-DS 170 8.2.2 Mehrkreis Load-Sensing Steuerung 2K/3K-CC-LS 172 8.2.3 Mehrkreis Verdrängersteuerung 3K/4K-DC 174 8.2.4 Systemvarianten mit getrennten Steuerkanten 2K/3K-IM 176 8.2.5 Mehrkreis Hybridsysteme 3K-Hy 180 8.3 Ergebnisse der Effizienzanalyse 188 8.3.1 Mehrkreis Drosselsteuerung 3K-OC-DS 188 8.3.2 Mehrkreis Load-Sensing Steuerung 2K/3K-CC-LS 193 8.3.3 Mehrkreis Verdrängersteuerung 3K/4K-DC 194 8.3.4 Systemvarianten mit getrennten Steuerkanten 2K/3K-IM 196 8.3.5 Hybridsystemvarianten 3K-Hy / 3K-CP 198 8.3.6 Gesamtsystemvergleich 200 9 Zusammenfassung und Ausblick 203 10 Literaturverzeichnis 209 A Anhang 233 A.1 Systematisierung von Schaltungsvarianten 233 A.1.1 Metrik zu Ermittlung der Schaltungseffizienz 233 A.2 Untersuchungen Mehrgrößensystem 242 A.2.1 Linearer Signalflussplans eines Systems mit vorgeschalteter Druckwaage 242 A.2.2 Darstellung der Systemmatrizen des ventilgesteuerten Zylinderantriebs 243 A.2.3 Kopplungsanalyse der offenen Steuerkette 243 A.2.4 Kopplungsanalyse der dezentralen Einfachregelung 245 A.2.5 Kopplungsanalyse linearer Entkopplungsfilter 246 A.2.6 Kopplungsanalyse nichtlineare Vorsteuerung 248 A.3 Untersuchungen am Systemprüfstand 250 A.3.1 Kinematikgleichungen 250 A.4 Untersuchungen am Demonstrator 251 A.4.1 Modellierung Mehrkörperstruktur 251 A.4.2 Werkzeug-Boden-Kontakt 252 A.4.3 Dynamische Vermessung Porportional-Sitzventil 253 A.5 Sytemvergleich 254 A.6 Methoden und Verfahren der Effizienzermittlung 254 A.6.1 Validierung Referenzsystem 259 A.6.2 Ergebnisse Effizienzanalyse 260

[ES] Los esquemas de antenas de múltiples entradas y múltiples salidas (MIMO) pueden maximizar la eficiencia espectral de los sistemas de Televisión Digital Terrestre (TDT) para la provisión de contenidos de gran capacidad, como los servicios emergentes de televisión de ultra alta definición (UHDTV), en el cada vez más escaso y limitado espectro radioeléctrico de la TDT debido a la creciente demanda de servicios inalámbricos de banda ancha (4G y 5G). Las tecnologías MIMO han sido desarrolladas inicialmente en la especificación técnica de TDT DVB-NGH (Digital Video Broadcasting Next Generation Handheld) y estandarizadas en el último estándar de TDT, ATSC 3.0 (Advanced Television Systems Committee 3rd Generation). Sin embargo, no hay despliegues comerciales MIMO de TDT. Por otro lado, la industria móvil ha desarrollado una tecnología de radiodifusión móvil, conocida como hoy en día como 5G Broadcast, basado en LTE (Long Term Evolution). Aunque LTE incorpora MIMO para transmisiones unicast punto a punto, 5G Broadcast sólo utiliza una única antenna en transmisión. Esta tesis doctoral tiene como objetivo evaluar el rendimiento de MIMO para radiodifusión (terrestrial broadcast) para sistemas inalámbricos de radiodifusión de nueva generación, tanto TDT como sistemas celulares. Durante la estandarización de los sistemas MIMO TDT, el diseño inicial tiene en cuenta condiciones de recepción perfectas, por ejemplo, demoduladores óptimos, información de estado del canal (CSI) perfecta, estimación perfecta de la potencia del ruido, etc. El objetivo principal de esta tesis doctoral es evaluar y optimizar el rendimiento de las transmisiones de radiodifusión MIMO en escenarios realistas. Esta tesis doctoral propone nuevos modelos de canales de propagación MIMO terrestres basados en medidas de campo que pueden utilizarse para la evaluación del rendimiento del sistema MIMO TDT. Además, también optimiza las diferentes configuraciones de transmisión y recepción MIMO, como la estimación de los canales MIMO en el receptor, y el procesado de señal. El escenario considerado en la tesis son torres de alta potencia con recepción fija, característico de las redes de TDT. Los resultados de esta tesis han contribuido al foro de estandarización ATSC, al sector de radiocomunicaciones de la Unión Internacional de Telecomunicaciones (UIT-R) y al proyecto nacional japonés de investigación sobre el sistema TDT de próxima generación. / [CA] Els esquemes d"antenes de múltiples entrades i múltiples sortides (MIMO) poden maximitzar l"eficiència espectral dels sistemes de Televisió Digital Terrestre (TDT) per a la provisió de continguts de gran capacitat, com els serveis emergents de televisió d"ultra alta definició (UHDTV) , en el cada vegada més escàs i limitat espectre radioelèctric de la TDT a causa de la creixent demanda de serveis sense fil de banda ampla (4G i 5G). Les tecnologies MIMO han estat desenvolupades inicialment en l'especificació tècnica de TDT DVB-NGH (Digital Video Broadcasting Next Generation Handheld) i estandarditzades a l'últim estàndard de TDT, ATSC 3.0 (Advanced Television Systems Committee 3rd Generation). No obstant això, no hi ha desplegaments comercials MIMO de TDT. D'altra banda, la indústria mòbil ha desenvolupat una tecnologia de radiodifusió mòbil, coneguda com avui dia com a 5G Broadcast, basat en LTE (Long Term Evolution). Tot i que LTE incorpora MIMO per a transmissions unicast punt a punt, 5G Broadcast només utilitza una única antena en transmissió. Aquesta tesi doctoral té com a objectiu avaluar el rendiment de MIMO per a radiodifusió (terrestrial broadcast) per a sistemes sense fil de radiodifusió de nova generació, tant TDT com sistemes cel·lulars. Durant l'estandardització dels sistemes MIMO TDT, el disseny inicial té en compte condicions de recepció perfectes, per exemple demoduladors òptims, informació d'estat del canal (CSI) perfecta, estimació perfecta de la potència del soroll, etc. L¿objectiu principal d¿aquesta tesi doctoral és avaluar i optimitzar el rendiment de les transmissions de radiodifusió MIMO en escenaris realistes. Aquesta tesi doctoral proposa nous models de canals de propagació MIMO terrestres basats en mesures de camp que es poden utilitzar per a l'avaluació del rendiment del sistema MIMO TDT. A més, també optimitza les diferents configuracions de transmissió i recepció MIMO, com l'estimació dels canals MIMO al receptor, i el processament de senyal. L'escenari considerat a la tesi són torres d'alta potència amb recepció fixa, característic de les xarxes de TDT. Els resultats d"aquesta tesi han contribuït al fòrum d"estandardització ATSC, al sector de radiocomunicacions de la Unió Internacional de Telecomunicacions (UIT-R) i al projecte nacional japonès de recerca sobre el sistema TDT de propera generació. / [EN] Multiple-Input Multiple-Output (MIMO) antenna schemes in Digital Terrestrial Television (DTT) systems aim to maximize the spectral efficiency for the provision of large capacity contents in the scarce and limited DTT Radio-Frequency (RF) channel. The delivery of the emerging Ultra-High Definition TV (UHDTV) services as well as the continuous broadcast spectrum shortage due to the rapidly growing demand for wireless broadband services (4G and 5G) are the motivations for this proposal. MIMO technologies have been firstly developed in the DTT technical specification DVB-NGH (Digital Video Broadcasting Next Generation Handheld) and standardized in the latest DTT standard, ATSC3.0 (Advanced Television Systems Committee 3rd Generation). However, MIMO broadcasting has not been commercialized due to the additional investment for both service providers and receivers. On the other hand, mobile industry has developed mobile broadcast technologies known today as 5G Broadcast based on LTE (Long Term Evolution). Although LTE incorporates MIMO for point to point unicast, 5G Broadcast only uses a single antenna in transmission at the moment. The Ph.D. aims at assessing the performance of MIMO for broadcasting (terrestrial broadcast) for next-generation wireless broadcasting systems, including next-generation wireless broadcasting systems, both DTT and cellular system. During the standardization of MIMO DTT systems, the initial design accounts for perfect reception conditions, e.g., optimal demodulators, perfect Channel State Information (CSI), perfect noise power estimation. The main goal of this PhD is to assess and optimize the performance of MIMO wireless broadcast transmissions in realistic scenarios. This PhD proposes new models of terrestrial MIMO propagation channels based on field measurements which can be utilized for the evaluation of MIMO DTT system. Furthermore, it also optimizes the different MIMO transmission and reception configurations, such as broadcast MIMO channel estimation and signal processing. The scenarios considered in the thesis are high-power high-tower transmitter with fixed reception and characteristics of DTT networks. The results of the PhD have contributed to the ATSC standardization forum, International Telecommunication Union Radiocommunication Sector (ITU-R), and the Japanese national research project on next generation DTT system. / Shitomi, T. (2023). Evaluation and Optimization of Multiple-Input Multiple-Output Antenna Schemes for Next-Generation Wireless Broadcasting [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/202598

This dissertation addresses novel techniques in determining gyroless micro-satellite attitude and attitude rate. The main objective of this thesis is to explore the possibility of using commercially available low cost micro-light star sensor as a stand-alone sensor for micro-satellite attitude as well as attitude rate determination. The objective is achieved by developing accurate and computationally efficient algorithms for the realization of onboard operation of a low fidelity star sensor. All the algorithms developed here are tested with the measurement noise presented in the catalog of the sensor array STAR-1000. A novel accurate second order sliding mode observer (SOSMO) is designed for discrete time uncertain linear multi-output system. Our design procedure is effective for both matched and unmatched bounded uncertain ties and/or disturbances. The bound on uncertainties and/or disturbances is assumed to be unknown. This problem is addressed in this work using the second order multiple sliding modes approach. Second order sliding manifold and corresponding sliding condition for discrete time system is defined similar on the lines of continuous counterpart. Our design is not restricted to a particular class of uncertain (matched) discrete time system. Moreover, it can handle multiple outputs unlike single out-put systems. The observer design is achieved by driving the state observation error and its first order finite difference to the vicinity of the equilibrium point (0,0) in a finite steps and maintaining them in the neighborhood thereafter. The estimation synthesis is based on Quasi Sliding Mode (QSM) design. The problem of designing sliding mode observer for a linear system subjected to unknown inputs requires observer matching condition. This condition is needed to ensure that the state estimation error is a asymptotically stable and is independent of the unknown input during the sliding motion. In the absence of a matching condition, asymptotic stability of the reduced order error dynamics on the sliding surface is not guaranteed. However, unknown bounded inputs guarantee bounded error on state estimation. The QSM design guarantees an ultimate error bound by incorporating Boundary Layer (BL) in its design procedure. The observer achieves one order of magnitude improvement in estimation accuracy than the conventional sliding mode observer (SMO) design for an unknown input. The observer estimation errors, satisfying the given stability conditions, converge to an ultimate finite bound (with in the specified BL) of O(T2), where T Is the sampling period. A relation between sliding mode gain and boundary layer is established for the existence of second order discrete sliding motion. The robustness of the proposed observer with respect to measurement noise is also analyzed. The design algorithm is very simple to apply and is implemented for two examples with different classes of disturbances (matched and unmatched) to show the effectiveness of the design. Simulation results show the robustness with respect to the measurement noise for SOSMO. Second order sliding mode observer gain can be calculated off-line and the same gain can work for large band of disturbance as long as the disturbance acting on the continuous time system is bounded and smooth. The SOSMO is simpler to implement on board compared to the other traditional nonlinear filters like Pseudo-Linear-Kalman-filter(PLKF); Extended Kalman Filter(EKF). Moreover, SMO possesses an automatic adaptation property same as optimal state estimator(like Kalman filter) with respect to the intensity of the measurement noise. The SMO rejects the noisy measurements automatically, in response to the increased noise intensity. The dynamic performance of the observer on the sliding surface can be altered and no knowledge of noise statistics is required. It is shown that the SOSMO performs more accurately than the PLKF in application to micro-satellite angular rate estimation since PLKF is not an optimal filter. A new method for estimation of satellite angular rates through derivative approach is proposed. The method is based on optic flow of star image patterns formed on a star sensor. The satellite angular rates are derived directly from the 2D-coordinates of star images. Our algorithm is computationally efficient and requires less memory allocation compared to the existing vector derivative approaches, where there is also no need for star identification. The angular rates are computed using least square solution method, based on the measurement equation obtained by optic flow of star images. These estimates are then fed into discrete time second order sliding mode observer (SOSMO). The performance of angular rate estimation by SOSMO is compared with the discrete time First order SMO and PLKF. The SOSMO gives the best estimates as compared to the other two schemes in estimating micro-satellite angular rates in all three axes. The improvement in accuracy is one order of magnitude (around1.7984 x 10−5 rad/ sec,8.9987 x 10−6 rad/ sec and1.4222 x 10−5 rad/ sec in three body axes respectively) in terms of standard deviation in steady state estimation error. A new method and algorithm is presented to determine star camera parameters along with satellite attitude with high precision even if these parameters change during long on-orbit operation. Star camera parameters and attitude need to be determined independent of each other as they both can change. An efficient, closed form solution method is developed to estimate star camera parameters (like focal length, principal point offset), lens distortions (like radial distortion) and attitude. The method is based on a two step procedure. In the first step, all parameters (except lens distortion) are estimated using a distortion free camera model. In the second step, lens distortion coefficient is estimated by linear least squares (LS) method. Here the derived camera parameters in first step are used in the camera model that incorporates distortion. However, this method requires identification of observed stars with the catalogue stars. But, on-orbit star identification is difficult as it utilizes the values of camera calibrating parameters that can change in orbit(detector and optical element alignment get change in orbit due to solar pressure or sudden temperature change) from the ground calibrated value. This difficulty is overcome by employing a camera self-calibration technique which only requires four observed stars in three consecutive image frames. Star camera parameters along with lens (radial and decentering) distortion coefficients are determined by camera self calibration technique. Finally Kalman filter is used to refine the estimated data obtained from the LS based method to improve the level of accuracy. We consider the true values of camera parameters as (u0,v0) = (512.75,511.25) pixel, f = 50.5mm; The ground calibrated values of those parameters are (u0,v0) =( 512,512) pixel, f = 50mm; Worst case radial distortion coefficient affecting the star camera lens is considered to be k1 =5 x 10−3 .Our proposed method of attitude determination achieves accuracy of the order of magnitude around 6.2288 x 10−5 rad,3.3712 x 10−5 radand5.8205 x 10−5 rad in attitude angles φ,θ and ψ. Attitude estimation by existing methods in the literature diverges from the true value since they utilize the ground calibrated values of camera parameters instead of true values. To summarize, we developed a formal theory of discrete time Second Order Sliding Mode Observer for uncertain multi-output system. Our methods achieve the desired accuracy while estimating satellite attitude and attitude rate using low fidelity star sensor data. Our methods require lower on-board processing requirement and less memory allocation; thus are suitable for micro-satellite applications. Thus, the objective of using low fidelity star sensor as stand-alone sensor in micro-satellite application is achieved.

[pt] Na primeira parte desta tese, são desenvolvidos dois esquemas de detecção por listas para sistemas MIMO multiusuário. As técnicas propostas usam uma única transformação de redução de reticulado (LR) para modificar a matriz de canal entre os usuários e a estação base (BS). Após a transformação LR, um candidato confiável do sinal transmitido é obtido usando um detector de cancelamento sucessivo de interferências (SIC). No detector em múltiplos ramos com redução de reticulado e cancelamento sucessivo de interferências (MB-LR-SIC) proposto, um número fixo de diferentes ordenamentos para o detector SIC gera uma lista de possíveis candidatos para a informação transmitida. O melhor candidato é escolhido usando o critério maximum likelihood (ML). No detector por listas de tamanho variável (VLD) proposto, um algoritmo que decide se o candidato atual tem uma boa qualidade ou se é necessário continuar procurando por um candidato melhor nos ordenamentos restantes é utilizado. Os resultados numéricos mostram que os esquemas propostos têm um desempenho quase ótimo com uma complexidade computacional bem abaixo do detector ML. Um esquema de detecção e decodificação iterativa (IDD) baseado no algoritmo VLD é também desenvolvido, produzindo um desempenho próximo a um sistema mono usuário (SU) livre de interferências. Na segunda parte desta tese, uma técnica de detecção desacoplada de sinais (DSD) para sistemas MIMO massivo é proposta. Esta técnica permite que o sinal composto recebido na BS seja separado em sinais independentes, correspondentes a diferentes classes de usuários, viabilizando assim o uso dos procedimentos de detecção propostos na primeira parte desta tese em sistemas MIMO massivos. Um modelo de sinais para sistemas MIMO massivo com antenas centralizadas e/ou antenas distribuídas operando em redes heterogêneas de quinta geração é proposto. Uma análise baseada na soma das taxas e um estudo de custo computacional para DSD são apresentados. Os resultados numéricos ilustram o excelente compromisso desempenho versus complexidade obtido com a técnica DSD quando comparada com o esquema de detecção conjunta tradicional. / [en] In the first part of this thesis, we introduce two list detection schemes for the uplink scenario of multiuser multiple-input multiple-output (MUMIMO) systems. The proposed techniques employ a single lattice reduction (LR) transformation to modify the channel matrix between the users and the base station (BS). After the LR transformation, a reliable candidate for the transmitted signal vector, provided by successive interference cancellation (SIC) detection is obtained. In the proposed multi-branch lattice reduction SIC (MB-LR-SIC) detector, a fixed number of different orderings, generates a list of SIC detection candidates. The best candidate is chosen according to the maximum likelihood (ML) selection criterion. For the proposed variable list detection (VLD) scheme, an algorithm to decide if the current candidate has good quality or if it is necessary to further explore different orderings to improve the detection performance is employed. Simulation results indicate that the proposed schemes have a near-optimal performance while keeping its computational complexity well below that of the ML detector. An iterative detection and decoding (IDD) scheme based on the VLD algorithm is also developed, producing an excellent performance that approaches the single user (SU) scenario. In the second part of this thesis, a decoupled signal detection (DSD) technique which allows the separation of uplink signals, for each user class, at the base station (BS) for massive MIMO systems is proposed. The proposed DSD allows to implement the detection procedures proposed in the first part of this thesis in massive MIMO scenarios. A mathematical signal model for massive MIMO systems with centralized and distributed antennas in the future fifth generation (5G) heterogeneous cellular networks is also developed. A sum-rate analysis and a study of computational cost for DSD are also presented. Simulation results show excellent performance of the proposed DSD algorithm when combined with linear and SIC-based detectors.