Abstract: A reference observer-based tracking controller is designed to achieve successful docking between the drogue of a tanker aircraft and the probe of a receiver aircraft. A reference trajectory generation module is used to turn the relative position between the drogue and the probe into a smooth reference trajectory. An output tracking observer is designed to estimate the feed-forward control signal and the reference states
to be tracked, and a full state feedback controller provides accurate tracking. Simulation results show that integration of observer and controller is effective for achieving accurate aerial refueling docking.