Attitude Dynamics And Control Of Solar Sail Spacecraft Orbiting Asteroids

Recently,Solar sail has been focused on by scholars and aerospace research institutes extensively because solar sail could perform space missions without consuming chemical propulsions,instead,it can merely utilize the inexhaustible solar radiation pressure?SRP?force for attitude/orbit control.Therefore,it is reported that some space missions can merely be accomplished by solar sail.Solar sail can also be used for asteroids explorations.The related research is confined to orbit motion and control and the attitude and control is studied seldom.To address this,the thesis investigates solar sail attitude dynamics and control,space tethered system?the sub-satellite is equipped with reflectivity control devices,RCDs,equivalently as solar sail?in-plane chaotic libration and its control around asteroids.The details of the thesis are as follows.?1?The pitch dynamics and control of solar sail orbiting prescribed asteroid orbits are explored.The detailed characteristics of the attitude control actuators,control vanes are analyzed.The envelop of the attitude control torque available,the attitude control torque and the rotation of the control vanes are also presented based on the attitude control scheme proposed in the thesis.The infinite/finite-time asymptotically stable attitude controllers are designed and the validation is performed using numerical simulations.?2?The chaotic in-plane libration of space tethered system is investigated under the condition of complicated irregular gravity filed of asteroids.The libration equation is established using the Lagrange equation method and the C₂₀-C₂₂ Gravity filed is considered.The Melnikov's method is exploited to predict the existence of the chaotic motion.The chaotic motion affected by the eccentricity,the tether's length and the radius of the orbit is studied numerically.The verification of the Melnikov's method is supported by presenting the time history of the libration,the phase plane,the Poincare of the system and the power spectrum density.?3?The chaotic libration control of the space tethered system is studied.Two chaotic motion control methods are proposed.The first one is based on the RBF neural network adaptive sliding mode saturation control scheme and the second one utilizes the combination of inerter and damper to control chaos.The former considers the practical restrictions such as the external disturbance and actuator saturation by improving the traditional chaos control method.The latter is a new method proposed for chaotic libration control of space tethered system.The chaos motion can be controlled from the view of energy dissipation.The validation and performance of the proposed scheme for chaotic libration control of space tethered system in complicated irregular gravity filed of asteroids are demonstrated by numerical simulation.