The development of a hardware-in-the-loop platform for the attitude determination and control testing of a small satellite

Junaid, Muhammad (2015-12)

Thesis (MEng)--Stellenbosch University, 2015.

Thesis

ENGLISH ABSTRACT: The launch costs for satellites are extraordinarily high. This emphasizes the importance of thorough unit and subsystem level testing to minimize the risk of failure after launch. The project was aimed at developing a hardware-in-the-loop (HIL) platform capable of testing the attitude determination and control system (ADCS) of small satellites. An Earth observation nanosatellite carrying an imaging payload was considered for testing purposes. The ADCS hardware suite was selected based on the mission requirements for the satellite, after which the necessary electronics for interfacing with the chosen sensors and actuators were designed and developed. The in-orbit performance of the designed ADCS was evaluated using a simulation platform based on realistic ADCS models. Simulation results confirmed that the designed ADCS algorithms met the in-orbit performance requirements using the selected hardware suite. The HIL platform integrates a fine sun sensor (FSS), a magnetometer, three reaction wheels (RW), three magnetorquers, an inertial measurement unit (IMU), an on-board data handler (OBDH), and a wireless communication module. The test setup consists of an air-bearing table placed inside a Helmholtz cage and a sun simulator. The air-bearing table allows full freedom of rotation in yaw and limited rotation in pitch and roll. The magnetometer was calibrated in the Helmholtz cage using the recursive least squares (RLS) method, as used for in-orbit magnetometer calibration. The magnetic field vector generated by the Helmholtz cage allowed testing of the B-dot and the stable spin magnetic controllers on the HIL platform. The B-dot controller damped the initial body rates to values less than 0.5°/s. A Rate Kalman Filter (RKF) was implemented to estimate the body angular rates from magnetometer measurements. The TRIAD method was used for attitude determination based on the magnetometer and the FSS output vectors. A quaternion feedback RW controller was tested on the HIL platform for yaw pointing. The pointing error observed was within ± 0.2°. In the final stage of HIL testing, the RW controller was combined with the magnetic controllers. The RW controller maintained the reference pointing in yaw and the magnetic controllers maintained the reference angular momentum of the wheel on the air-bearing table.

AFRIKAANSE OPSOMMING: Satelliet lanseringskostes is merkwaardig hoog. Daarom is deeglike eenheids- en substelselvlak toetse noodsaaklik om die risiko van na-lanseringsmislukkings te verminder. In hierdie projek is ‘n hardeware-in-die-lus (HIL) platform vir die toets van ‘n klein satelliet se oriëntasiebepaling- en beheerstelsel (OBBS) ontwikkel. ‘n Aardwaarnemingsnanosatelliet, wat ‘n kamera as loonvrag dra, is vir toetsdoeleindes oorweeg. Die keuse van OBBS hardeware komponente is op die satelliet missie se vereistes gebasseer. Daarna is die elektronika wat nodig is om met die sensore en aktueerders te koppel ontwerp en ontwikkel. Die OBBS se in-wentelbaan vermoëns is d.m.v. simulasies, wat op realistiese OBBS komponentmodelle gebasseer is, geëvalueer. Dié simulasies het bevestig dat die OBBS algoritmes se in-wentelbaan vermoëns die vereistes te verwagte van so ‘n stelsel bevredig. Die HIL platform bestaan uit ‘n fyn sonsensor (FSS), ‘n magnetometer, drie reaksiewiele (RW), drie magneetstange, ‘n inersieële metingseenheid, ‘n aanboord datahanteerder (ABDH) en ‘n draadlose kommunikasie module. Die toetsomgewing bestaan uit ‘n sonsimuleerder en ‘n luglaer binne in ‘n Helmholtz hok. Volle rotasie om die gier-as word deur die luglaer toegelaat, maar duik- en rol rotasies word beperk. Die magnetometer is d.m.v. ‘n rekursiewe kleinstekwadraat metode, wat ook vir in-wentelbaan kalibrasies gebruik word, in die Helmholtz hok gekalibreer. B-dot en stabiele spin magnetiese beheer kon m.b.v. die Helmholtz hok se opgewekte magneetveld getoets word. Die B-dot beheerder kon die oorspronklike liggaamhoeksnelhede tot minder as 0.5°/s demp. ‘n Hoektempo Kalman Filter (RKF) is geïmplementeer om die liggaam se hoeksnelhede vanaf die magnetometer lesings af te skat. Die TRIAD metode, wat op die magnetometer en FSS uittree vektore gebasseer is, is vir oriëntasiebepaling gebruik. Gier-as rigtinvermoë is in die HIL omgewing getoets met ‘n Quaternioon RW terugvoerbeheerder. Die maksimum rotasiehoekfout het nie 0.2° oorskry nie. In die finale HIL fase is die RW beheerder met die magnetiese beheerders gekombineer. Die RW beheerder het die gier-as oriëntasie onderhou, terwyl die magnetiese beheerders momentumontlading van die wiel uitgevoer het.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/97881
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