In this paper two Unscented Kalman Filters (UKF) are implemented to solve the estimation of a satellite's position in orbit and its orientation relative to Earth's Centered Inertial frame. Their aim is to see if an absolute position accuracy of less than 1 km and an orientation estimation to less than 1 0 are possible for a 3U CubeSat with GPS, sun sensors, magnetometers and a star tracker as sensors. The orbit UKF is based on a Runge Kutta 7(8) th-order integration method for orbit propagation. The dynamic model uses perturbational accelerations due to Earth's geopotential, the gravity of the Moon and the Sun, atmospheric drag and solar pressure. The state of the lter is identical to the observation vector and consists of position and velocity vectors of the satellite. The GPS receiver is used for measurements. Emphasis has been put on the sampling rate of the GPS receiver as its availability is constrained by the satellite's power limitations. The state of the attitude UKF consists of an error quaternion, angular velocities and magnetometer bias. The sun sensors, magnetometers and the star tracker are used for measurements. Dierent sensor combinations have been simulated with the purpose of determining their inuence on the estimated attitude. The results of the simulations indicate that an absolute position error of less than 1 km is feasible for sampling times of 15 minutes or less (approximately 6 per orbit). Furthermore an accuracy of less than 1 0 is achieved by using the star tracker for attitude determination either alone or in combination with the other sensors.

Sudoku is a discrete constraints satisfaction problem which is modeled as an underdetermined linear system. This report focuses on applying some new signal processing approaches to solve sudoku and comparisons to some of the existing approaches are implemented. As our goal is not meant for sudoku only in the long term, we applied approximate solvers using optimization theory methods. A Semi Definite Relaxation (SDR) convex optimization approach was developed for solving sudoku. The idea of Iterative Adaptive Algorithm for Amplitude and Phase Estimation (IAA-APES) from array processing is also being used for sudoku to utilize the sparsity of the sudoku solution as is the case in sensing applications. LIKES and SPICE were also tested on sudoku and their results are compared with l1-norm minimization, weighted l1-norm, and sinkhorn balancing. SPICE and l1-norm are equivalent in terms of accuracy, while SPICE is slower than l1-norm. LIKES and weighted l1-norm are equivalent and better than SPICE and l1-norm in accuracy. SDR proved to be best when the sudoku solutions are unique; however the computational complexity is worst for SDR. The accuracy for IAA-APES is somewhere between SPICE and LIKES and its computation speed is faster than both. / Sudoku är ett diskret bivillkorsproblem som kan modelleras som ett underbestämt ekvationssystem. Denna rapport fokuserar på att tillämpa ett antal nya signalbehandlingsmetoder för att lösa sudoku och att jämföra resultaten med några existerande metoder. Eftersom målet inte enbart är att lösa sudoku, implementerades approximativa lösare baserade på optimeringsteori. En positiv-definit konvex relaxeringsmetod (SDR) för att lösa sudoku utvecklades. Iterativ-adaptiv-metoden för amplitud- och fasskattning (IAA-APES) från gruppantennsignalbehandling användes också för sudoku för att utnyttja glesheten i sudokulösningen på liknande sätt som i mättillämpningen. LIKES och SPICE testades också för sudokuproblemet och resultaten jämfördes med l1-norm-minimiering, viktad l1- norm, och sinkhorn-balancering. SPICE och l1-norm är ekvivalenta i termer av prestanda men SPICE är långsammare. LIKES och viktad l1-norm är ekvivalenta och har bättre noggrannhet än SPICE och l1- norm. SDR visade sig ha bäst prestanda för sudoku med unika lösningar, men SDR är också den metod med beräkningsmässigt högst komplexitet. Prestandan för IAA-APES ligger någonstans mellan SPICE och LIKES men är snabbare än bägge dessa.

Real-time detection and extraction of visual features in wireless sensor networks is a challenging task due to its computational complexity and the limited processing power of the nodes. A promising approach is to distribute the workload to other nodes of the network by delegating the processing of different regions of the image to different nodes. In this work a solution to optimally schedule the loads assigned to each node is implemented on a real visual sensor network testbed. To minimize the time required to process an image, the size of the subareas assigned to the cooperators are calculated by solving a linear programming problem taking into account the transmission and processing speed of the nodes and the spatial distribution of the visual features. In order to minimize the global workload, an optimal detection threshold is predicted such that only the most significant features are extracted. The solution is implemented on a visual sensor network testbed consisting of BeagleBone Black computers capable of communicating over IEEE 802.11. The capabilities of the testbed are also extended by adapting a reliable transmission protocol based on UDP capable of multicast transmission. The performance of the implemented algorithms is evaluated on the testbed.

Geomagnetically induced currents (GIC) are a natural phenomenon which arises due to solar storms. During a solar storm, large amounts of magnetized plasma are ejected from the surface of the sun. When this plasma reaches earth, it causes fluctuations in the geomagnetic field. Such 　fluctuations may induce DC over-currents in long transmission lines. These currents affect the transmission system several dierent ways; In particular high voltage transformers are sensitive to GIC. When the over-current flows through the transformer windings the reactive power absorption of the transformer increases, which may lead to voltage instability in the power system. For this project, the main issue has been to determine whether or not an increase in the size of the transformer core leads to the reactive power absorption being less sensitive to GIC. In order to investigate this issue a recently developed transformer model has been used; the Hybrid transformer model. This model combines the principle of duality with a matrix representation of the transformer. The Hybrid transformer model, which has recently been implemented in the power system simulations software PSCAD, has been used to simulate GIC events in transformers of varying core sizes. The results from these simulations indicate that a larger transformer core is associated with a smaller increase in reactive power absorption during a GIC event. It is also clear that the reactive power absorption as a function of GIC magnitude is a non-linear function when the Hybrid transformer model is applied. This function has previously been considered a linear function. / Geomagnetiskt inducerade strömmar (GIC) är ett naturfenomen som uppstår till följd av solstormar. Vid en solstorm kastas stora mängder magnetiserad plasma ut från solens yta, och när denna plasma når jorden uppstår 　uktuationer i det jordmagnetiska fältet. Detta kan leda till att DCstr ömmar induceras i långa transmissionsledsningar. Dessa överströmmar påverkar kraftsystemet på 　era olika sätt, bland annat har de en stor påverkan på transformatorer. Då överströmmen 　yter genom transformatorlindningarna ökar det reaktiva eektuttaget för transformatorn, vilket kan leda till spänningsinstabilitet i systemet. En fråga som legat till grund för detta projekt är huruvida en ökning av transformatorkärnans storlek gör transformatorns reaktiva eektuttag mindre känsligt för GIC. För att undersöka detta har en ny transformatormodell använts; den såkallade hybridmodellen som kombinerar dualitetsprincipen med en matrisrepresentation av transformatorn. Denna modell, som nyligen implementerats i simuleringsprogrammet PSCAD, har använts för att simulera GIC i transformatorer med kärnor av olika storlekar. Resultaten från dessa simuleringar indikerar att större transformatorkärna medför mindre förändring av det reaktiva eektuttaget när transformatorn utsätts för GIC. Det är även tydligt att det reaktiva eektuttaget som funktion av GIC är en icke-linjär funktion när hybridmodellen används. Denna funktion har tidigare ansetts vara linjär.

Performing visual feature extraction in a network of processing nodes is challenging and requires the development of algorithms that perform the allocation and delegation of computational tasks, of protocols responsible for the correct transmission of data, etc. This report starts working from the implementation of a testbed for the evaluation of distributed processing of visual features and extends its functionality. The testbed is implemented in C++ us- ing credit-card sized computers and ZigBee USB units. Communi- cation between nodes is carried out through ASN.1 defined types. The first part of the thesis work consists of enabling the system to work with two different feature extraction schemes. The first one is the already implemented SURF algorithm from OpenCV and the second one is the original implementation of BRISK. The user must be capable of choosing indifferently between them. The second part of the work consists of modifying the transmission aspects of the system including the necessary classes to provide reliability via the design of a retransmission protocol. The reliable transmission protocol used is a version of a Stop-and-Wait scheme. The system’s performance is evaluated detailing the time needed to complete each step of the feature extraction process, presenting a comparison between the SURF and BRISK detection and ex- traction times, and computing the frame loss rate and achievable throughput once the retransmission protocol is implemented.

This work investigated the effect of partial discharges (PD) on the complex permittivity of PVC, PC, PTFE, PE and PA6. The material samples were subjected to prolonged PD activity and the complex permittivity of the material was measured by dielectric spectroscopy (DS) before and after the sample was aged. The results showed a change in the loss factor for the tested materials, some were more affected than others and showed different behaviors when subjected to the PD aging. Hence it was not possible to find any general trend in the complex permittivity of the tested materials. Several of the materials exhibited a loss factor with -1/2 slope at low frequencies corresponding to diffusion. The -1/2 slope implies that the loss factor and the dynamic component of the real permittivity should be equal, which could not be seen. Therefore it is uncertain whether what was observed is a diffusion process or not. The results could suggest that PD aging causes a change in the trapping characteristics of the material. Furthermore, space charges deposited on the cavity wall from the PD activity could diffuse into the bulk of the material where some of the charges are trapped. If a DS measurement is performed before the trapped charges have had time to recombine or be conducted away, it could affect the complex permittivity. This was demonstrated by performing another DS measurement on an aged PC sample which had been left to rest for 35 days. The measurement showed that the complex permittivity had returned to almost the same state as before aging. Measurement problems were encountered which affected the measurements in this work. The problems are believed to be caused by the measurement electrodes used for the DS measurements not being heavy enough to eliminate small unwanted air-gaps between the electrodes and sample. Furthermore, incomplete results were obtained for some measurements which was believed to be due to the capacitance of the sample being at the limit of what the measurement instrument was able to measure. / Det här arbetet undersökte effekten av partiella urladdningar (PD) på den komplexa permittiviteten i PVC, PC, PTFE, PE och PA6. Materialproverna utsattes för långvarig PD aktivitet och materialets komplexa permittivitet mättes med hjälp av dielektrisk spektroskopi (DS) före och efter att provet åldrats. Resultaten visade en förändring i förlustfaktorn i de testade materialen, några påverkades mer än andra och de uppvisade olika beteenden när de blev utsatta för PD åldring. Det var därför inte möjligt att hitta någon generell trend i den komplexa permittiviteten för de olika testade materialen. Flera av materialen uppvisade en förlustfaktor med -1/2 lutning vid låga frekvenser vilket motsvarar diffusion. -1/2 lutningen medför att förlustfaktorn och den dynamiska komponenten av den reella permittiviteten borde sammanfalla, vilket inte kunde ses. Det är därför osäkert huruvida det som observerats är en diffusionsprocess eller inte. Resultaten kan tyda på att PD-åldring orsakar en förändring i potentialfällors egenskaper i materialet. Således skulle rymdladdningar som deponeras på väggarna i kaviteten på grund av PD-aktiviteten kunna diffundera in i materialet där en del av laddningarna fastnar. Om en DS mätning görs innan de fångade laddningarna har fått tillräcklig tid att rekombinera eller ledas iväg, kan det påverka den komplexa permittiviteten. Detta visades genom att genomföra en DS mätning på ett åldrat prov av PC som fått vila i 35 dagar. Mätningen visade att den komplexa permittiviteten hade återgått till nästan samma tillstånd som innan den åldrades. Mätproblem påträffades vilket påverkade mätningarna i detta arbete. Problemen antas vara orsakade av att mätelektroderna som användes till DS mätningarna inte var tillräckligt tunga för att eliminera små oönskade luftgap mellan elektroderna och provet. Dessutom erhölls ofullkomliga resultat för några av mätningarna vilket tros bero på att provets kapacitans befann sig på gränsen för vad mätinstrumentet kunde mäta.

Free Space Optical (FSO) communications are an emerging technology. Multiple resources around the world are being dedicated to the study and implementation of associated technologies. The possibility of high data rates, lower masses and more power efficient antennas are the expected advantages of these systems. However FSO channels are highly vulnerable. Atmospheric perturbations as well as pointing misalignments compromise the integrity of the transmitted data. Besides, current data protection architectures for FSO communication systems are not powerful enough to protect the data due to the nature of the perturbations. Therefore, Deutsches Zentrum für Luft- und Raumfahrt (DLR) is working on the implementation of a communication protocol (Laser Ethernet Transceiver protocol, LET) capable of transmitting high bit rates reliably. LET has to overcome the multiple errors induced by the disturbances in the channel (fades in the signal induced by the atmosphere and miss-pointing) and data stream misalignments during transmission. In addition, LET has to provide a framework for transmitting 1GbE (Gigabit Ethernet) payloads. Thus the focus of this MSc Thesis is on the definition and implementation of the abovementioned algorithms and hardware structures. These hardware structures are developed for their integration on Field Programmable Gate Arrays (FPGA) in VHDL language. At the end of this MSc Thesis, a significant improvement of 3.5 dB in the optical gain has been achieved with a Bit-Level Forward Error Correction (BLFEC) implementation. Some of the hardware structures have also been implemented and tested for the next steps. An analysis of the synchronization problems that will affect the system has been done and a technical solution has been provided. Additionally, an improvement of the channel throughput has been achieved in order to comply with the 1GbE Standard.

In this master thesis, a mathematical model of a hydraulic servo system for a manipulator robot is completed by using several different methodologies. The models proposed are particularly tuned for the DeLaval VMS robotic arm. The parameter identification of the robotic arm is accomplished by dividing the model into several subsystems and investigating each system separately by using catalogue data, experimental data and construction drawings. Furthermore, the assumptions are proposed based on the literature review and the expertise of in-house engineers. After completion of parameter identification several different mathematical models including linear and nonlinear methodologies are introduced. It is demonstrated that the improvednonlinear model can successfully mimic the movement of the robotic arm with relatively small errors and it is found to be fairly reliable. Moreover, the errors incurred when chamber pressures are compared with experimental data are found to be relatively small. Furthermore, the improved linear model have successfully delivered an accurate position estimation especially for the medium valve opening, while the chamber pressures are relatively less accurately predicted. The study further carries out sensitivity (uncertainty) analyses to investigate the crucial parameters of the model since it is sometimes very problematic to precisely estimate these parameters. It is found out that the flow coefficient and supply pressures have remarkable impact on the results of the simulations. Therefore, it is strongly advised that these parameters should be very carefully evaluated during the modeling process. Finally the bulk modulus models are compared and the influence of the bulk modulus is revealed.

Power system harmonics are a topic of significant concern when considering power quality issues in systems containing Variable Speed Drives. The extent to which grid-connected power electronics based motor drives affect power quality is tightly enforced through standards, and must be adhered to. To ensure compliance, harmonic models of Variable Speed Drives and relevant components of the connected power system are evaluated. When necessary, analysis results can be used to aid the design of additional harmonic mitigation measures. Harmonic assessments are most commonly carried out using time-domain models. This thesis details the fundamentals of harmonic assessment and mitigation measure design. Matlab implementations of those fundamentals are discussed, with comments regarding the accuracy and limitations of each. State of the art analytical harmonic models for Voltage Source Variable Speed Drives are analyzed and compared, from which a new model for 3-level inverter Variable Speed Drives is proposed. The new model can be implemented in any numerical computing environment and is thought to generate a harmonic current spectrum for an approximate judgement of harmonic compliance based on the current injection method. / Övertoner i kraftsystem innehållande frekvensomriktare är ett viktigt ämne när el-kvalité behandlas. Den grad nätanslutna elektroniska motorsystem påverkar el-kvalitén är noggrant upprätthållen av standarder och måste följas därefter. För att säkerställa att standarder upprätthålls utvärderas modeller för frekvensomriktare och relevanta komponenter. När det anses nödvändigt kan resultaten vara vägledande för design av ytterligare övertonsminskande åtgärder. Utvärdering av övertoner görs i allmänhet med hjälp av modeller i tidsdomän. Denna uppsats går igenom grunderna för bedömning av övertoner och design av övertonsminskande åtgärder. Matlab-modeller av dessa diskuteras i termer av precision och begränsningar. De främsta analytiska modeller for frekvensomriktare undersöks och jämförs, varefter en ny modell av en växelriktare med 3 nivåer föreslås. Denna modell kan med enkelhet implementeras i numeriska datormiljöer och framställer ett frekvensspektrum av strömmen för en approximativ bedömning av el-kvalité baserad på ströminmatningsmetoden.

This thesis addresses the issues of (inter)harmonics propagation on electrical grids. More specifically it concerns two different kinds of studies. The first one is the harmonic impact of the integration of new technologies such as Electric Vehicle charging parks which generate harmonic voltages. The second one is the propagation on these grids of communication signals such as the pricing signal. These two kinds of voltages behave a priori the same way since they are superimposed to the fundamental feeding voltage, with a higher frequency. However, their main structural difference is that, while harmonic voltages generated by electric cars are unwanted on electrical grid, the pricing signal is intended at certain points of the grid. For the first kind of studies, concerning harmonics generated by Electric Vehicles, the aim of this project was to determine the problems that may appear on electrical grids when electric car parks are connected thereto. To do so, laboratory measurements on several Electric Vehicle models, separately or simultaneously, were performed. From their results, different models of EVs have been drawn up enabling to perform simulations on an existing car park. Some measurements were then carried out on this car park in order to conclude on its impact on the Power Quality of the grid. The second study is about the pricing signal propagation. It focuses on different ways of modeling grid components, especially loads, in simulation tools at the specific frequency of this signal. For Medium Voltage grids, several load models can be found in the literature and are compared in this report. For Low Voltage grids, a model based on the results of recent measurements is suggested in the report.