Research On Non-keplerian Orbits Control Of Solar Sail Spacecraft

Diplaced orbit and libration point in solar terrestrial space are ideal positions for solar and cosmic observation.In view of the special solar-terrestrial space environment and the unique propulsion principle of solar sail spacecraft,this thesis studies the stationary control of the non-Keplerian orbits of solar sail spacecraft.To clarify the characteristics of the non-Keplerian orbits of solar sail spacecraft,the two-body and three-body dynamics of solar sail in the solar-terrestrial space are formulated.Two types of non-Keplerian orbits of solar sail in solar-terrestrial space are then derived.The tight coupling between the attitude control and orbit control of the solar sail makes it necessary to allocating the attitude angles during an active orbit control.The propulsion space of solar sail spacecraft is expounded.A relationship between the propulsion and the attitude angles of solar sail is derived.Based on the two-body and three-body dynamics,an attitude condition of the two types of non-Keplerian orbits of the solar sail spacecraft is gained.The thesis first studies the non-Keplerian orbits stationary control of the solar sail spacecraft using solar sail as its only propulsion actuator.Based on the non-Keplerian orbit dynamics of the solar sail spacecraft,a linearized solar sail dynamics model is derived.An optimal control law considering the input constraints is proposed.The orbit control is completed by the control of attitude.The control law is useful in correcting the orbit entry error and the control of unstable orbit.The thesis then studies the hybrid propulsion control of the non-Keplerian orbit of the solar sail spacecraft.Due to the introduction of the thruster,the thrust by control unit should be allocated into thruster and solar sail,not just into the attitude angles of solar sail.Two classes of analytical control allocation methods are proposed.The solar sail is used as the major propulsion actuator for the reduction of fuel consumption.The proposed control allocation methods are achieved by directly solving the allocation equations and finding the extreme value of an index function.Since the controllable attitude angle of the solar sail is of two-dimension,it is a little troublesome to allocate the three-dimension thrust into the two attitude angles.The thesis finally studies the non-Keplerian orbits stationary control based on Reflectance Control Device(RCD)which can provide another thrust dimension by changing the reflectivity of the solar sail.To guarantee the stationary control performance under the presence of disturbances and the high-frequency chattering of the solar sail attitude,a second-order sliding mode control law is proposed,and the corresponding control allocation method is also studied.