Abstract
The dynamics of a satellite involves orbit and attitude motion. Both orbit and attitude motion are required to be controlled for achieving any mission objectives. This thesis examines both of these motion with a focus on formation flying and attitude stabilization using aerodynamic drag or solar radiation pressure. The concept of satellite formation flying involves the distribution of the functionality of a single satellite among several smaller, cooperative satellites. Autonomous multiple satellite formation flying space missions offer many promising possibilities for space exploration. A large quantity of fuel is typically required onboard any conventional satellite to carry out its attitude and orbital positioning, and satellite formation flying has a higher fuel requirement. As on-board fuel is a scarce commodity, it is important to have control methods requiring little or no fuel. Keeping this in mind, this thesis presents the results of using aerodynamic drag or solar radiation pressure for satellite formation flying. This methodology has potential to have significant commercial advantage as it pertains to almost negligible fuel requirements. A leader/follower formation architecture is considered for the formation flying system. The control algorithms are derived based on adaptive sliding mode control technique. Aerodynamic drag is used to accomplish multiple satellite formation flying in low Earth orbit whereas solar radiation pressure is used in geostationary orbit. Due to the nature of the aerodynamic drag, in-plane control can only be accomplished by the suitable maneuvering of the drag plates mounted on the satellites. Solar radiation pressure is able to accomplish in-plane and out-of-plane control by maneuvering of the solar flaps. Efficacy of the control methodology in performing various scenarios of formation flying including formation reconfiguration is validated by numerical simulation in both the cases. The numerical results demonstrate the effectiveness of the proposed control techniques for satellite formation flying using aerodynamic drag or solar radiation pressure. Formation flying accuracies of less than 5 m are achieved in both the cases. Next, this thesis investigates the use of aerodynamic drag or solar radiation pressure for satellite attitude control. In the case of the aerodynamic drag stabilized satellite, the drag plates are considered to be attached to the satellite while the solar flaps are fixed to the satellite in the case of the solar radiation pressure stabilized satellite. In both the cases, the control algorithm is developed based on adaptive sliding mode control technique. The effectiveness of this methodology is numerically evaluated under various scenarios including the pressure of failure/fault in the solar flaps or drag plates attached to the satellite. The satellite attitude is stabilized within reasonable limits in all the cases thereby demonstrating robust performance in the presence of external disturbances.
Highlights
Autonomous formation flying is currently one of the most important areas of research in satellite dynamics and control
Key challenges involved in these missions include autonomous control of the satellites which are influenced by the different disturbing forces, and to achieve it with minimum fuel consumption
This thesis investigates the efficacy of "propellant-less" method based on aerodynamic drag or solar radiation pressure for multiple satellite formation flying or attitude control, and develops innovative control algorithms with the goal of achieving a low cost AOCS which is able to exhibit superior performance
Summary
Autonomous formation flying is currently one of the most important areas of research in satellite dynamics and control. Active stabilization methods require expenditure of propellant or energy, leading to an increase in weight and space requirements in the satellite, whereas passive/semi-passive methods depend on natural/environmental forces and Chapter 1 Introduction they make use of spin stabilization, dual spin, gravity gradient, solar radiation pressure (SRP), aerodynamic drag, and Earth’s magnetic field to achieve the desired performance. These methods are less costly and their advancement may provide a viable solution to the development of low cost AOCS for satellites. This thesis investigates the efficacy of "propellant-less" method based on aerodynamic drag or solar radiation pressure for multiple satellite formation flying or attitude control, and develops innovative control algorithms with the goal of achieving a low cost AOCS which is able to exhibit superior performance
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