Browsing by Author "Jordaan, Willem Hendrik"

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    Spinning solar sail : the deployment and control of a spinning solar sail satellite
    (Stellenbosch : Stellenbosch University, 2016-03) Jordaan, Willem Hendrik; Steyn, W. H.; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
    ENGLISH ABSTRACT: Solar sailing has become a viable and practical option for current satellite missions. A spinning solar sail has a number advantages above a 3-axis stabilised sail. A spinning sail is more resistant to disturbance torques and the misalignment of the centre of mass and centre of pressure. The spinning sail generates a constant centrifugal force, which reduces sail billowing and makes it possible to use wire booms. The new tri-spin solar sail and tri-spin Gyro satellite configurations are proposed that combines the advantages of the spinning and 3-axis stabilised sail designs. This study focuses on the deployment control of the sail and the orientation control of the satellite. Different deployment methods of a rotating structure are studied. The active deployment method makes use of a separate module with an actuator on the rotating system to deploy the structure. The passive deployment method, deploys the structure by using centrifugal force generated by continually spinning the deployment mechanism. A pulse deployment controller and model estimation methods for the passive deployment mechanism are proposed to improve the controllability of the passive deployment method. The mathematical models of these methods are investigated in simulation. A deployment demonstrator is built, which is able to perform either an active or a passive deployment. The theoretical simulation results show promising correlations to the practical results from the deployment demonstrator. Further experiments are conducted to investigate methods to increase the damping of a wire boom. The orientation control includes the development of an accurate mathematical model of the satellite. This model contains the rigid dynamics of the satellite and the non-rigid dynamics of the rotating wire booms. The moment of inertia of the satellite is used as a cross-coupling parameter between the rigid satellite dynamics and non-rigid wire dynamics. The dynamics of the wire booms are examined and the main parameters to keep the wire booms stable are identified. Attitude manoeuvres for changing the orbit altitude of a satellite in earth- and sun-centred orbits are implemented within an orbital simulation to reveal the change in orbital elements caused by the solar thrust. An attitude determination and control system (ADCS) is designed for the conceptual satellite. The state determination and attitude controllers are designed to perform the needed manoeuvres for a satellite to change its altitude by using solar pressure. The controller design includes a magnetic B-dot, a deployment rate controller, solar tracking controller, aerodynamic controller and momentum dumping controller. The performance of the ADCS design on a tri-spin solar sail satellite are investigated through an in depth simulation, which includes: the dynamic models created for the rigid satellite, the non-rigid wire booms and deployment methods. The simulations reveal that it is feasible to implement the ADCS system on the novel tri-spin solar sail satellite. The tri-spin solar sail satellite is able to perform faster attitude manoeuvres than a standard spinning solar sail making it able to operate in a low earth orbit. This will enable the satellite to change its attitude to produce the required solar thrust to change its orbit.