| With the rapid growth of space activities and advancement of aerospace science and technology, many autonomous space missions have been proliferating in recent decades. Control of spacecraft in proximity operations is of great importance to accomplish these missions. The research in this dissertation aims to provide a precise, efficient, optimal, and robust controller to ensure successful spacecraft proximity operations. This is a challenging control task since the problem involves highly nonlinear dynamics. In addition, uncertainties and disturbances make the precise control more difficult. Four control design approaches are integrated to solve this challenging problem. The first approach is the integrated optimization formulation. By considering the spacecraft rigid body translational and rotational dynamics, together with the flexible motion, we established a unified framework so that the overall system performance and constraints can be addressed in one optimization process. The second approach is the indirect robust control method by which we formulate the robust control objectives into an optimal control cost function and prove the equivalency between the robust stabilization problem and the transformed optimal control problem. The third approach is to employ the &thetas;-D optimal control technique to obtain a closed form feedback control law and thus facilitate onboard implementation. The fourth approach is to use the inverse optimal adaptive control method combined with indirect robust control scheme to alleviate the conservativeness of the robust control scheme by using online parameter estimation such that adaptive, robust, and optimal properties can be all achieved.;To show the effectiveness of the proposed control approaches, six degree-of-freedom spacecraft proximity operation simulation is conducted and demonstrates satisfying performance under various uncertainties and disturbances. |
