Robust Motion Control of Underactuated Autonomous Surface Craft by Wei Xie Thesis Supervisors: Prof. Carlos Silvestre Prof. Qingsong Xu This thesis addresses the problems of path following and trajectory tracking. By employing the backstepping technique, path following controllers are applied to an underactuated autonomous surface craft, named DELMAC and an underactuated hovercraft. The proposed control laws are capable of driving the vehicles towards, and stay within the neighborhood of a desired path with a desired speed profile, achieving globally practical stability. Using similar methodology, a trajectory tracking control strategy was developed and applied to a model hovercraft. Furthermore, in order to validate the efficacy and performance of the controllers proposed in this thesis, simulations and experimental results are presented.