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Typical design challenges for Unmanned Aerial Vehicles (UAVs) require low aerodynamic drag and structural weight. Both of these requirements imply that these aircraft are considerably more flexible than conventional aircraft and their stability analyses are more complex since they require models unifying rigid body and elastic dynamics. This paper aims to built such a model for a generic UAV. The model is then used to address stability in terms of divergence and flutter.

An outer loop guidance architecture was designed to control autonomous aerial refueling mission from the trail aircraft side. The design utilized bank, yaw rate, velocity and climb rate commands implemented using a previously developed adaptive trajectory concept. The concept was based on position error feedback that was used to control trail aircraft overshoot and tracking about the lead aircraft refueling point. To demonstrate this application, an open loop linear trail aircraft model at a given flight condition was selected. Inner loop control laws were designed using Linear Quadratic Regulator feedback controller and Balanced Deviation theory. The outer loop guidance architecture was then added to implement the application. The performance of the system was then evaluated for a selected position error, and disturbance.

An adaptive trajectory concept that exploits the capabilities of a fixed-gain set 6-DOF autopilot was developed for autonomous aerial refueling. The concept was based on differential position error feedback that was used to control overshoot and tracking speed about the tanker refueling point. To demonstrate this concept, an automatic aerial refueling flight system simulation for a conventional receiving aircraft was developed. The performance of the system was then evaluated for a selected differential position, flight condition, and atmospheric disturbance.