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Axisymmetric mirrors have no collision free radial transport, but such magnetic fields may have problems with plasma stability (the tearing instability in particular). There are some means to improve plasma stability in axisymmetric mirrors by magnetic expander tanks or axisymmetric divertors, but plasma stability can still be a challenge in axisymmetric mirrors. An alternative is to use quadrupolar magnetic fields as a robust method to overcome the stability issues. A price may then be increased radial transport if the magnetic field design is done without strict consideration of asymmetries, which could result from manufacturing errors.The computations have been done with a hybrid reactor scenario in mind. Such a case have less demands for confinement, but the demands are still challenging. Confinement for about 200 longitudinal bounces is required in a hybrid reactor. The computations carried out here have confirmed that axial asymmetry may become dangerous for plasma confinement in quadrupolar mirror machines. Asymmetry in the range of a few percentage relative error will almost surely result in a too strong radial leakage (at least without a radial electric field). The computational results made in this paper may suggest that if the manufacturing error is kept below 0.15% relative error throughout the plasma confinement region, there is then a some margin for sufficient radial confinement quality. Such accuracies ought to be possible to achieve in the manufacturing process, possible combined with compensating magnetic fields to maintain a precise magnetic field design. The precision requirements in the design is still a bit challenging.

In this thesis, a feasibility study will be conducted in order to determine if the usage of acontrol moment gyroscope is a possibility for a micro satellite as its attitude control. Thegoal is to conclude if gyroscopes are suitable replacements for the current reaction wheelswhich are acting as the attitude control for the satellite. In the first part of the thesis thegeneral function of the control moment gyroscope and three different types of arrangementsare displayed with all their respective advantages and disadvantages. Then one ofthem will be designed to fit within the restrictions of 1U. The full design of the pyramidconfiguration was chosen due to its compact size and spherical angular momentum envelope.The full design contains all the components such as motors, flywheels, mounts,frame, screws etc. which provide a cost estimate which is a huge input in determiningthe feasibility of this thesis. In the future the manufacture of the pyramid configurablecontrol moment gyroscopes shall be tested in the future with a more advanced steeringlaw in order to determine the full potential of the attitude control system.

Some modern spacecraft missions require precise knowledge of the attitude, obtained from the ground processing of on-board attitude sensors. A traditional 6-state attitude determination filter, containing three attitude errors and three gyro bias errors, has been recognized for its robust performance when it is used with high quality measurement data from a star tracker for many past and present missions. However, as higher accuracies are required for attitude knowledge in the missions, systematic errors such as sensor misalignment and scale factor errors, which could often be neglected in previous missions, have become serious, and sometimes, the dominant error sources. The star tracker data have gaps and degradation caused by, for example, the Sun and Moon blocking in the filed of view and data time tag errors. Thus, attitude determination based on the gyro data without using the star tracker data is inevitably required for most missions for the period when the star tracker is unable to provide accurate data. However, any gyro-based attitude errors would eventually grow exponentially because of the uncorrected systematic errors of gyros and the uncorrected gyro random noises. An improved understanding of the gyro random noise characteristics and the estimation of the gyro scale factor errors and gyro misalignments are necessary for precise attitude determination for some present and future missions. The 6-state filters have been extended to 15-state filters to estimate the scale factor and misalignment errors of gyros especially during a high-slew maneuver and the performance of theses filters has been investigated. During a starless period, the inevitable drift of the EKF solutions, which are caused by the uncorrected gyro’s systematic errors and the gyro random noises, can be replaced with the batch solutions, which are less affected by the data gap in the star tracker. Power Spectral Density and the Allan Variance Method are used for analyzing the gyro random noises in both ICESat and simulated gyro data, which provide better information about the process noise covariance in the attitude filter. Both simulated and real data are used for analyzing and evaluating the performances of EKF and batch algorithms. / text

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Datorn är ett viktigt verktyg i vår vardag. För rörelsehindrade kan datorn vara en förutsättning för att kunna fungera i vardagen. Datorn har som tekniskt hjälpmedel gett funktionshindrade större möjligheter till meningsfulla aktiviteter, såsom att på egen hand skriva, läsa och kommunicera. Samtidigt är det inte alltid funktionshindrade klarar av att använda vanliga datorer utan behöver alternativa inmatnings- och styrenheter. Målet med denna licentiatavhandling har varit att utveckla tekniker som ska stödja personer med rörelsebegränsningar. Främst har arbetet varit att utveckla alternativa tekniker för att kunna manövrera en dator. Viktiga aspekter i arbetet har varit att göra hjälpmedlen användarvänliga, möjliga att individanpassa, och att ta tillvara de tänkta användarnas synpunkter kring behov och önskemål. Vidare har inmatningsenheten utvärderats av användare och även tillämpats som ett rehabiliteringsverktyg för en mindre patientgrupp med nackskador, så kallade pisksnärtskador. Utöver dessa vetenskapliga mål har produktionsaspekterna varit viktiga. För att säkerställa att enheten ska kunna bli en produkt måste den kunna produceras och säljas till ett rimligt pris och detta måste beaktas under hela utvecklingsprocessen. En alternativ datormus baserad på MEMS-gyroskop har utvecklats. Utvecklingen är gjord utifrån de krav de tilltänka användarna ställde på den alternativa datormusen och enheten är utprovad och förbättrad i en iterativ process mellan utvecklare och användare, så kallad användarcentrerad utvecklingsprocess. MEMS-gyron var den typ av rörelsesensor som bäst svarade mot de krav som ställdes på enheten. De användare som deltog vid ett längre fältprov var samtliga nöjda och ville behålla musen. För att underlätta processen att välja rätt typ av gyro och att kunna utvärdera deras stabilitet under olika omgivningsfaktorer, såsom temperatur och vibrationer, har en testrig för gyron utvecklats. Människors rörelsemönster skiljer sig från industriella tillämpningar och därför behövs en speciell testrigg. Testriggen roterar gyron och mäter sensorsignalen under olika betingelser. Flera gyron kan testas samtidigt och testdatat kan sparas och analyseras i efterhand. Ett interaktivt datorbaserat träningsprogram har utvecklats och utvärderats vid en pilotstudie tillsammans med den alternativa datormusen. Syftet var att låta nackskadade utföra huvudrörelser och få en feedback på att de tränar rätt. Resultatet pekar på att detta kan vara en lovande metod. / Computers are important tools. People with motion disabilities sometimes are dependent on a computer and used as a technical aid the computer has improved the possibilities to perform meaningfull tasks, as writing, reading and communicating. However, disabled often need an alternative input device to control a computer.   The aim with this licentiate theses has been to develope techniques to support persons with motion limitations. Focus has been to develope alternative techniqes to control a computer. Important aspects have been user-friendlieness, possiblilities to perform individual adaptions and incorporatation of specifications from the intended users. Further, the input device has been evaluated by users and applied as a rehabilitation tool for a smaller patient group of persons with whiplash associated disorders.   Further, production aspects are important. To make the unit into a product, it has to be possible to produce and sell to a reasonable price. This has to be considered during the whole development process.   An alternative computer mouse based on a MEMS gyroscope has been developed. The specifications made by the users has been used as a starting point in the development and the unit has been evaluated and improved in an iterative process, so called user centric development. MEMS-gyros were the type of motion sensors most corresponding to the demands. The users that participated in a longer field test were all satisfied and wanted to keep the mouse.   To improve the process to choose right kind of gyro and to be able to evaluate their stability depending on factors as temperature and vibration, a test-rigg for gyros has been developed. Human motion pattern differs from industrial applications and therefor a special test-rigg was needed. The testrigg rotates the gyros and measures the sensor signal. Several gyros can be tested simultaneously and data can be stored and analysed afterwards.   An interactive computerbased training program has been developed and evaluated in a pilot study together with the altrenative computer mouse. The aim has been to let people with neck injuries perform head motions and get feedback that they perform the right kind of training. The result is promising.

As surprising as it may seem, accurate north finding, with an error of only several milli-radian, is still a very difficulttask and has been achieved only with very expensive systems. On the contrary, there are very simple systems that give theazimuth with an angular error five times superior but for a price a hundred times inferior. Moreover, these systems generally arenon-autonomous (i.e. they are environment dependent and can lose their precision in many situations). This assessment leads tothe following relevant question: Is it possible to design a north finding system with good precision, for a moderated cost and thatworks in any situation?This report presents and evaluates a solution which attempts to answer this problem. This solution is based on a gyrocompassingprinciple: a gyro measures the earth’s angular velocity in order to find the azimuth. This solution can be implementedfollowing several methods, this report presents and compares two of these implementations: Maytagging and Carouseling. Thecomparison is made thanks to a theoretical study, a computer simulation and tests on a real model designed for this report.Carouseling allows us, in theory, to reach an accurate azimuth, but puts mechanical constraints on the system. Maytaggingimplementation seems adapted considering trade-off between precision and cost. Further improvements on gyros will certainlymake systems based on gyro-compassing the most efficient autonomous systems for north finding.In this report, precisions reached by the different implementations are not made explicit for confidentiality reasons.

Attitude control laws that use control moment gyros (CMGs) and momentum wheels are derived with nonlinear techniques. The control laws command the CMGs to provide rapid angular acceleration and the momentum wheels to reject tracking and initial condition errors. Numerical simulations of derived control laws are compared. A trend analysis is performed to examine the benefits of the derived controllers. We describe the design of a CMG built using commercial off-the-shelf (COTS) equipment. A mixed attitude control strategy is implemented on the spacecraft simulator at Virginia Tech. / Master of Science

Geodetic measurements with a gyro theodolite are an important technique for establishing control networks in tunnelling projects. The observations are used as a separate control point outside the main network while checking the angle of the tunnels direction as it is difficult to connect the underground network to a superior network outside the tunnel.  This study aims to investigate the usefulness of gyro surveys in tunnel networks and evaluate how much they improve the positional accuracy of underground control networks. The study compares a total of four network simulations (with and without gyro observations) that have been divided into 12 sections. The sections are then compared to each other to determine the influence of gyro observations on the positional uncertainty in the network. Gyro observations were found to contribute to significant improvements in measurement data. Without them the tunnel would have an uncertainty greater than five centimetres within approximately 1000 m. The results provide valuable insights into the impact of gyro measurements on geodetic control network in tunnels and how they can be used to improve measurement data. / Gyromätningar och gyroteodoliter har idag en viktig roll på grund av de höga krav på noggrannhet som ställs inom många av dagens tunnelprojekt vid stomnätsmätning i tunnlar. Gyroobservationerna används för att få en utomstående kontroll av stomnätet då detta på grund av tunnelns utformning är problematiskt att koppla mot ett överordnat nät. Det finns dock inte mycket skrivet om hur dessa bör användas samt hur stor effekt mätningarna har på ett vanligt tunnelbygge idag. Studiens syfte är att undersöka gyromätningar användbarhet i tunnelnät samt utvärdera hur mycket dessa förbättrar noggrannheten på kortare stomnät i tunnelmiljö. I rapporten har sammanlagt fyra nätsimuleringar för en tunnelbana i Stockholm jämförts med varandra där två tillhör byggnätet och två bruksnätet (med och utan gyroobservationer). Dessa har delats upp i totalt 12 sektioner varav 6 stycken innehåller gyroobservationer och 6 är utan gyroobservationer. Sektionerna har sedan jämförts med varandra för att ta reda på hur stor inverkan gyroobservationerna har på osäkerheten i näten samt om det är möjligt att nå upp till en teoretisk osäkerhet i nätet på max fem centimeter. Resultatet visar att den radiella medelosäkerheten minskade från 1,69 cm till 0,93 cm i sektion 1, 1,24 cm till 0,64 cm i sektion 2 och 7,13 cm till 1,64 cm i sektion 3. Vid genomslaget mellan sektion 1 och 2 minskade osäkerheten från 5,10 cm till 1,14 cm i sektion 1 och i sektion 2 från 4,41 cm till 1,48 cm. Sträckan på fackverksnätet innan osäkerheten översteg fem centimeter blev 794m i sektion 1 och 846 m i sektion 3. I sektion 2 översteg aldrig osäkerheten fem centimeter trots att längden på fackverket var 971 m. Sektion 1 och 2 i bruksnätet visade ingen betydande förändring beroende på om gyroobservationer användes eller inte. I sektion 3 minskade dock den radiella medelosäkerheten med 2,29 cm vilket kan förklara genom att stomnätet inte har något anslutningsnät i slutet på denna sektion. Generellt visades gyroobservationerna bidra till stora förbättringar av mätdata i byggnätet och utan dessa skulle tunneln inom ca. 1000 m ha en osäkerhet större än fem centimeter. Resultatet ger en bra inblick i hur stor påverkan gyromätningar har på stomnät i tunnlar samt hur dessa kan användas för att förbättra mätvärden.

Cette thèse propose une analyse mathématique des modèles cinétiques en présence d'un champ magnétique intense.L'objectif de ce projet est le développement d'outils mathématiques nécessaires à la modélisation des plasmas de fusion. Les phénomènes physiques rencontrés dans les plasmas de fusion mettent en jeu des échelles caractéristiques disparates. L'interaction entre ces ordres de grandeurs est un enjeu important et requiert une analyse multi-échelle. Il s'agit d'un problème d'homogénéisation par rapport au mouvement rapide de rotation des particules autour des lignes de champ magnétique. Nous étudions le régime du rayon de Larmor fini pour le système de Vlasov-Poisson, dans le cadre de champs magnétiques uniformes, en appliquant les méthodes de gyro-moyenne. Nous donnons l'expression explicite du champ d'advection effectif de l'équation de Vlasov, dans laquelle nous avons substitué le champ électrique auto-cohérent, via la résolution de l'équation de Poisson moyennée à l'échelle cyclotronique. Nous mettons en évidence la structure hamiltonienne du modèle limite et présentons ses propriétés : conservations de la masse, de l'énergie cinétique, de l'énergie électrique, etc.Nous généralisons ensuite cette étude dans le cadre de champs magnétiques non uniformes. Comme précédemment, les principales propriétés des modèles limites sont mises en évidence : conservations de la masse, de l'énergie, structure hamiltonienne.Nous prenons en compte également les effets collisionnels, en présence d'un champ magnétique intense. Après identification des équilibres et invariants du noyau de collision moyenné, on s'intéresse à la dérivation de modèles fluides. / This thesis proposes a mathematical analysis of kinetic models in the presence of strong magnetic fields.The objective of this project is the development of mathematical tools required for modelisation of fusion plasmas. The physical phenomena encountered in fusion plasmas involve disparate characteristic scales. The interaction between these orders of magnitude is an important issue and requires a multi-scale analysis. We appeal to homogenization techniques with respect to the fast rotation motion around the magnetic field lines.We study the finite Larmor radius regime for the Vlasov-Poisson system, in the framework of uniform magnetic fields, by appealing to gyro-average methods. We indicate the explicit expression of the effective advection field entering the Vlasov equation, after substituting the self-consistent electric field, obtained by the resolution of the averaged (with respect to the cyclotronic time scale) Poisson equation. We emphasize the hamiltonian structure of the limit model and present its properties : conservation of mass, of kinetic energy, of electric energy, etc.Then we generalize this study to general magnetic shapes. As before, the main properties of the limit model are emphasized : mass and energy balances, hamiltonian structure.We also take into account the collisional effects, under strong magnetic fields. After identifying the equilibria and the invariants of the average collision operator, we inquire about fluid models.