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Comparison of Control Approaches for Formation Flying of Two Identical Satellites in Low Earth Orbit / Jämförelse av reglermetoder för formationsflygning med två identiska satelliter i låg jordbanaBasaran, Hasan January 2020 (has links)
Formation flying of satellites describes a mission in which a set of satellites arrange their position with respect to one another. In this paper, satellite formation flying guidance and control algorithms are investigated in terms of required velocity increment Delta-v, and tracking error for a Chief/Deputy satellite system. Different control methods covering continuous and impulsive laws are implemented and tested for Low Earth Orbit (LEO). Sliding Mode, Feedback Linearization and Model Predictive Controllers are compared to an Impulsive Feedback Law which tracks the mean orbital element differences. Sliding Mode and Feedback Linearization controllers use the same dynamic model which includes Earth Oblateness perturbations. On the other hand, Model Predictive Control with Multi-Objective Cost Function is based on the Clohessy–Wiltshire equations, which do not account for any perturbation and do not cover the eccentricity of the orbit. The comparison was done for two different missions both including Earth Oblateness effects only. A relative orbit mission, which was based on the Prisma Satellite Mission and a rendezvous mission, was implemented. The reference trajectory for the controllers was generated with Yamanaka and Ankersen’s state transition matrix, while a separate method was used for the Impulsive Law. In both of the missions, it was observed that the implemented Impulsive Law outperformed in terms of Delta-v, 1.2 to 3.5 times smaller than the continuous control approaches, while the continuous controllers had a smaller tracking error, 2 to 8.3 times less, both in terms of root mean square error and maximum error in the steady state. Finally, this study shows that the tracking error and Delta-v has inversely proportional relationship. / Formationsflygning av satelliter innebär att en grupp satelliter flyger tillsammans och anpassar sina relativa lägen i förhållande till varandra. I detta examensarbete studerades regleralgoritmer för formationsflygande satelliter med fokus på bränsleförbrukning och positionsavvikelse genom ”Chief & Deputy”-metoden. Olika reglermetoder har studerats, t.ex. Sliding Mode- och Feedback Linearization-reglering för formationsflygningsfall i låg jordbana med J2-störning samt en Model Predictive-reglering för fall med relativ rörelse baserad på Clohessy-Wiltshire-ekvationerna. Vidare studerades en reglermetod baserad på impulsframdrivning. De fyra reglermetoderna implementerades på två olika rymduppdrag. Först ett uppdrag baserat på Prisma-satelliterna för två satelliter i relativ omloppsbana och sedan ett Rendezvous-uppdrag. Referensbanan för alla reglermetoder, utom för implusmetoden, har tagits fram med hjälp av Yamanakas och Ankersens tillståndsmatris. Resultaten visar att den implementerade impulsmetoden presterar bättre med avseende på bränsleförbrukning, medan de kontinuerliga reglermetoderna producerade mindre relativ positionsavvikelse, både med avseende på kvadratiskt medelvärde och maximalt värde.
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Modelling and controlling a bio-inspired flapping-wing micro aerial vehicleSmith, David Everett 17 January 2012 (has links)
The objective of this research is to verify the three degree of freedom capabilities of a bio-inspired quad flapping-wing micro aerial vehicle in simulation and in hardware. The simulation employs a nonlinear plant model and input-output feedback linearization controller to verify the three degree of freedom capabilities of the vehicle. The hardware is a carbon fiber test bench with four flapping wings and an embedded avionics system which is controlled via a PD linear controller. Verification of the three degree of freedom capabilities of the quad flapping-wing concept is achieved by analyzing the response of both the simulation and test bench to pitch, roll, and yaw attitude commands.
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An Anti-Skid Brake Controller For A Fighter Aircraft With An Elastic StrutKumar, V V Nagendra 04 1900 (has links)
This thesis deals with the design of an anti-skid brake controller for a generic fighter aircraft. Antiskid brake controllers prevent wheel locking and maximize the coefficient of friction between the tyre and the ground, resulting in lower stopping distance and time. The frictional force is maximized by regulating the slip. A model for the landing gear is first developed, which consists of the translational and rotational motions of the wheel, the equation for the slip and the elastic landing gear strut dynamics. The elastic behaviour of the landing gear is characterized through its modal frequencies, obtained from a Finite element analysis. As the governing equations are nonlinear, with linear elastic deformations of the strut, feedback linearization is used to design the anti-skid controller. The brake controller is found to work well. Its stability is verified through numerical simulations. Both the plant parameters and the sensor measurements are perturbed up to 10% from their nominal values. It is seen that the feedback linearization tolerates these variations quite well. The system is exceptionally tolerant to sensor noises. The torsional stiffness of the strut is found to be more critical than the longitudinal stiffness. Limits on the torsional stiffness that can be tolerated by the controller are found. This determines the limits on the stiffness of the landing gear beyond which gear walk may appear. The thesis concludes with suggestions for future work in this exciting field.
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[en] MODELING AND NON LINEAR CONTROL OF A GROUND VEHICLENULLS STEERING / [pt] MODELAGEM E CONTROLE NÃO-LINEAR DA DIREÇÃO DE UM VEÍCULO TERRESTREALEXANDRE DE LIMA SPINOLA 30 June 2004 (has links)
[pt] Modelagem e Controle Não Linear de um Veículo Terrestre
sobre Suspensão descreve um estudo em dinâmica veicular no
qual inicialmente apresenta-se um modelo analítico para
representar a geração de forças longitudinais e laterais no
contato do pneu com o solo. Em seguida é desenvolvido, para
um automóvel de passeio terrestre sobre suspensão, um
modelo não linear de 4 graus de liberdade (velocidades
longitudinal, lateral, de guinada e de rolagem), e a sua
linearização. Expande-se esse modelo para um de 8 graus de
liberdade, no qual inclui-se o movimento de rotação axial
de cada uma das quatro rodas, e consideram-se os movimentos
do veículo somente no plano, sem efeitos de pitch ou
bounce, mas apresentando alguma relação de distribuição de
cargas devido ao roll. Descrevem-se ainda modelos em Grafos
de Ligação para os três dinâmicas de um veículo terrestre
(longitudinal, lateral e vertical) e seus acoplamentos,
visando futuras análises mais detalhadas desse sistema.
Todos os modelos em malha aberta são validados através
simulações computacionais em diversas condições típicas de
operação. Na segunda parte desse trabalho é apresentada a
estratégia proposta para o tratamento do problema de
controle direcional do veículo em uma manobra qualquer,
empregando a metodologia da linearização por realimentação,
tendo como base o modelo linear de 4 graus de liberdade.
São analisados os resultados encontrados através de
simulação computacional para a malha fechada com diferentes
combinações de parâmetros, empregando os modelos não
lineares de 4 e 8 graus de liberdade. Conclui-se discutindo
a possibilidade de generalização deste procedimento para
diferentes aplicações em Dinâmica Veicular. / [en] Modeling and Non Linear Control of a Ground Vehicle's
Steering describles a study in vehicle dynamics, which
presents an analytic model representing the generation of
longitudinal and lateral forces at the contact patch
between tire and ground. Next it is developed, for a
typical passenger car, a non-linear model with four degrees
of freedom (longitudinal, lateral, yaw and roll
velocities), and its linearization. This model is then
expanded to another one with eight degrees of freedom,
which includes the axial rotation of each one of the four
wheels, and considers the vehicle's movement only at a
known plane, whithoud pitch and bounce effects, but
including some load distribution among the wheels, due to
roll. Computational simulation in varius typical operation
condition validate all open loop models. The second part of
this work presents the proposed strategy for directional
control of a vehicle at any type of manoeuvre, using the
feedback linearization methodology, directly applied to the
linear four degrees of freedom model. Theresults obtained
trhough computational simulation for a closed loop model
with different parameters are analysed using both nonlinear
four and eight degrees of freedom models. The possibility
of generalizing this procedure to distinct applications in
Vehicle Dynamics is, then, discussed.
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Moderní struktury řízení servosystémů se střídavými pohony / Modern Algorithms of AC Servo-drives ControlHrnčárek, Martin January 2010 (has links)
This master thesis deals with the modern algorithms of the asynchronous induction machine and permanent magnet induction machine. It focuses at vector control, direct torque control and input-output feedback linearization. It also describes a library creation and its usages in the Matlab – Simulink environment. The final part of this thesis contains an implementation of chosen algorithms on the DSC Freescale 56F800E family.
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