This thesis evaluates an existing state feedback controller designed for the CubeSat MOVE-II. In addition, the control system is further developed and a variety of control strategies are evaluated. The goal is to achieve a pointing accuracy of 5° and a guaranteed convergence to the desired attitude within the domain of the nonlinear system. The evaluated concepts are restricted to low earth orbits for small satellites utilizing magnetic actuation only. Furthermore, a spin stabilization around a non-principal axis of inertia is assumed. The presence of sensor noise and external disturbances, especially the residual magnetic dipole, are considered. The existing controller is analyzed for different orbits and the convergence rate for randomized initial conditions is obtained in a Monte Carlo simulation. A new gain is developed for the state feedback controller under consideration of the system requirements for MOVE-II. Furthermore, the concepts of residual magnetic dipole moment compensation, the use of an Extended Kalman Filter and a new operation point switching strategy are proposed in order to increase the pointing accuracy and convergence rate. Three nonlinear control laws based on different Lyapunov functions are evaluated. One of them is selected as an implementation candidate. A Software-in-the-Loop and a Hardware-in-the-Loop simulation successfully verifies this candidate for use on the flight hardware as part of the control firmware. It is found that the existing controller is sensitive to inclination changes of the orbit. Furthermore, with an average pointing accuracy of 5.8° and a corresponding variance of 4.3 deg^2 it does not fulfill the stated goal. In total, 69% of the evaluated cases converge to the desired attitude. The linear controller with the new gain and extensions attains a pointing accuracy of 3° with a variance of 0.38 deg^2. It converges in 80% of the cases. The nonlinear implementation candidate shows convergence in all Monte Carlo simulation runs and achieves a final pointing accuracy of 3.3° with a variance of 2.3 deg^2. Furthermore, a Hardware-in-the-Loop simulation shows that this controller is stable in the presence of large delays and with low numeric precision. It also shows to be compatible with the existing firmware of MOVE-II. Dynamically updateable control parameters render this implementation interesting to satellite operators.


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    Titel :

    Advancing the Attitude Determination and Control System for the CubeSat MOVE-II


    Beteiligte:

    Erscheinungsdatum :

    2019-08-28


    Medientyp :

    Aufsatz (Zeitschrift)


    Format :

    Elektronische Ressource


    Sprache :

    Englisch



    Klassifikation :

    DDC:    620 / 629




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