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Attitude Determination and Control of the CubeSat MIST
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
2016 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

The ADCS concept in MIST reects the limitations of the CubeSat in terms of space, power and onboard computer computational capability. The control is constrained to the use of only magnetic torquers and the determination to magnetometers and Sun sensors in spite of the the under-actuation and underdetermination during eclipses. Usually small satellites with a similar ADCS and demanding requirements fail, therefore MIST would be a design reference for this kind of concept in the case it succeeds.

The objectives of this thesis work are the feasibility assessment of the concept to meet the nominal requirements in MIST and the consideration of alternatives. Firstly, the importance of gravitational stabilization and di erent congurations for the inertial properties are analyzed based on the linear stability regions for nadir pointing spacecraft. Besides, extended stability regions are derived for the case when a momentum wheel is used to consider alternative options for passive stabilization in terms of the inertial properties. Then a controller based on the Asymptotic Periodic Linear Quadratic Regulation (AP LQR) theory, the currently most extended and e ective for pure magnetic control in small satellites, is assessed. Also a Liner Quadratic Regulator design by means of numerical optimization methods, which has not been used in any real mission, is considered and its performances compared with the AP LQR. Regarding attitude determination a Linear Kalman Filter is designed using the AP LQR theory. Finally, a robustness analysis is conducted via Monte Carlo simulations for those control and determination strategies.

Abstract [sv]

Systemet for attitydstyrning och -bestamning i nanosatelliten MIST reekterar sma satelliters begransningarna i utrymme, elkraft och omborddatorkapacitet. Regleringen ar begransad till styrning med magnetspolar som genererar kraftmoment. For attitydbestamningen anvands magnetometrar och solsensorer trots under-manovrering och -bestamning vid solformorkelse. Vanligtvis misslyckas sma satelliter med liknande reglersystem och hoga krav, sa om MIST lyckas skulle den bli ett referenskoncept. Malen med detta examensarbete ar att utfora en genomforbarhetsstudie av ett reglerkoncept for att mota de nominella kraven for MIST samt undersoka av alternativa reglersystem. E ekten av gravitationsstabilisering och olika masstroghetskongurationer har analyserats med hjalp av linjariserade stabilitetsregioner for en nadirpekande satellit. Stabilitetsregionerna forstoras da ett roterande hjul infors i ett alternativt stabiliseringskoncept eftersom det roterande hjulet paverkar de e ektiva masstroghetsmomentet. Regleringsalgoritmen som utvarderats i detta arbete ar baserad pa teorin om Asymptotisk Periodisk Linjar Kvadratisk Regulering (AP LKR), den som ar mest anvand samt e ektiv for ren magnetisk styrning av sma satelliter. En utformning av ett koncept baserat pa Linjar Kvadratisk Reglering med numerisk optimering, vilket inte tidigare verkar anvants for ett riktigt rymduppdrag, har undersokts och jamforts med AP LKR-regleringen. Nar det galler attitydbestamningen sa har ett linjart Kalmanlter utformats for AP LKR-regleringen. Slutligen sa har en robusthetsanalys gjorts genom Monte Carlo-simuleringar for styrnings- och bestamningsstrategierna.

Abstract [es]

El concepto para el ADCS en MIST reeja las limitaciones de los CubeSats en cuanto a espacio, potencia y capacidad computacional del ordenador a bordo. El control esta restringido al uso de solo magnetopares y la determinacion a magnetometros y sensores de Sol a pesar de la imposibilidad de actuacion segun todos los ejes y el conocimiento incompleto en actitud durante eclipses. Normalmente peque~nos satelites con un ADCS similar y exigentes requisitos fallan, por la tanto MIST sera una referencia de dise~no para este tipo de concepto en el caso de que tenga exito. Los objetivos de este trabajo n de master son la evaluacion de la viabilidad del concepto para cumplir los requisitos nominales en MIST y la consideracion de alternativas. Primero, la importancia de la estabilizacion gravitacional y diferentes conguraciones para las propiedades masicas son analizadas en base a las regiones de estabilidad lineales para vehculos espaciales apuntando segun nadir. Ademas, regiones de estabilidad extendidas son deducidas para el caso en el que una rueda de momento es usada con el n de considerar opciones alternativas de estabilizacion pasiva en terminos de las propiedades masicas. Despues un controlador basado en la teora del Asymptotic Periodic Linear Quadratic Regulation, el actualmente mas extendido y efectivo para control magnetico puro en peque~nos satelites, es evaluado. Tambien un dise~no de LQR por medio de metodos de optimizacion numerica, el cual no ha sido usado en ninguna mision real, es considerado y sus prestaciones comparadas con el AP LQR. En relacion a la determinacion de actitud un Linear Kalman Filter es dise~nado usando la teora del AP LQR. Finalmente, un analisis de robustez es llevado a cabo a traves de simulaciones de Monte Carlo para esas estrategias de control y determinacion.

Place, publisher, year, edition, pages
2016. , p. 31
Series
TRITA-AVE, ISSN 1651-7660 ; 2016:61
National Category
Aerospace Engineering
Identifiers
URN: urn:nbn:se:kth:diva-203284OAI: oai:DiVA.org:kth-203284DiVA, id: diva2:1081973
Examiners
Available from: 2017-03-15 Created: 2017-03-15 Last updated: 2017-03-15Bibliographically approved

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