| This dissertation enriches our knowledge of attitude control methodologies that are suitable for solar sails, and in particularly large solar sails. In chapter 1, the fundamental physics of solar sails and existing solar sail attitude control methodologies are reviewed. In chapter 2, an attitude control methodology (Tip Displacement Method) that is suitable for large solar sail is presented. In the proposed method, the sail wing-boom attachment points are allowed to move, and under solar radiation pressure, the sail membrane sags into a curved profile. A mathematical model of this curved profile is built, and analytical solutions of solar radiation body torque based on the curved wing is derived. It is shown that this methodology along can generate enough body toque in all three body axis directions for attitude control of large solar sails. In chapter 3, the propose method is further investigated, and the effect of incident solar radiation direction on solar radiation pressure body torque generation is studied. The effect of sail shape is also studied a step further, mainly by relaxing previously made cylindrical assumption on the shape of the wing. Based on an optimization process, algorithms for determining the shape of the wing are given, and solar radiation body torques are developed for the shape of the wing. One finding is that for small tip displacements, the cylindrical sail wing model is sufficient in estimating the solar radiation body torque. In chapters 2 and 3, the analyses are carried out based on the assumption that the wing shape is of a generalized cylinder. In chapter 4 a theoretical basis is provided for this assumption.;Using the mathematical model of the single wing for the proposed tip displacement attitude control strategy, in chapter 5 a whole square solar sail model is built, and the system controllability is studied for linearized system states. The system is found to be robust because of the many actuators used, and is controllable even under certain wing failure scenarios. In chapter 6, a reorientation scheme for large angle orientation change using the tip displacement attitude control method is developed. Based on a sequence of three Euler angle rotations, a detailed algorithms for this reorientation scheme is given, and simulation results for reorientation cases are presented. Lastly, in chapter 7, the results of this work and future research directions are discussed. |
