| Due to the potential advantages of the micro-satellites formation flying system, such as cost reduction, flexibility, observational baseline increase, and reliability improvement, numerous formation related missions have been proposed and seriously studied. Along these many potential benefits, come a variety of challenges. Dynamics and control of the multi-satellites in the formation is one of these issues and is addressed in this dissertation. To date, most formation flying dynamics and control studies are based on the linear Clohessey-Wiltshire equations and none address the problem with a coupling between the attitude and orbit motions. Furthermore, commercial software, such as STK and FreeFlyer, is not capable of feedback control simulation. These observations motivate this research to develop a generalized coupled attitude-orbit relative motion and to design controllers based on this model.; The developed generalized dynamics model is based on the leader-follower structure and the desired attitude is coupled with the real time relative position due to the formation mission requirement. This nonlinear model is applicable to any closed reference orbit cases and incorporates a coupling between the attitude and orbit. Also, atmospheric drag and J 2 perturbations are included.; The formation flying control system can be regarded as a two-tiered architecture. In the lower level, continuous controllers are designed to meet the objectives of each vehicle, and in the higher level, discrete time event determines the formation configuration and reconfiguration. After comparison with LQR, Hinfinity/mu synthesis, and feedback linearization strategies, sliding mode control is chosen as the basic control method for the lower level in this dissertation. Furthermore, boundary layer control and genetic algorithm are implemented in order to reduce chatters with the implementation of the sliding mode control and reduce the fuel consumption. In the upper level, perceptive frame concept is adopted for the discrete event determination. It is demonstrated that the proposed control architecture is capable of tracking and maintaining the desired position and attitude under different formation missions. |
