Robust Control Design for a Flexible Unmanned Aerial Vehicle 2007-01-3929

This paper concerns with control of Unmanned Aerial Vehicles (UAVs), which are expected to carry out very critical maneuvers, well in excess of what pilots are able to tolerate. Safety factors for these aircraft are not as high as those for manned aircraft and they are lighter than the manned aircraft. These imply that UAVs are considerably more flexible than the manned aircraft. A newly developed theory for the dynamics and control of maneuvering flexible aircraft is ideally suited for the analysis and design of such aircraft. The control input can be conceived as having two parts, one part designed to steer the aircraft to permit the realization of a desired flight trajectory and another part designed to reduce any deviations from the desired trajectory. Control design for steering the aircraft can be achieved by using the inverse dynamics of quasi-rigid aircraft (aircraft treated as rigid). On the other hand, control design for the deviations requires output feedback control. Note that flexible aircraft are underactuated systems and Linear Quadratic Gaussian (LQG) (Linear Quadratic Regulator (LQR) in conjunction with Kalman Filter) is widely for this type systems. However, it is known that LQG has no guaranteed stability margin. Because aircraft in general and UAVs in particular are highly uncertain systems, it is important that the control design tolerate the uncertainties in the system parameters. In response to this concern, this paper presents an observer-based loop-shaping design for flexible UAVs.