Development and flight testing of quantitative feedback theory pitch rate stability augmentation system

The design of a quantitative feedback theory control system to improve the flight handling qualities of an unmanned aerial vehicle (UAV) at relaxed stabilities is illustrated. Aircraft flown at low static margins are significantly more efficient than conventional designs, but without stability augmentation they are difficult if not impossible to control. Longitudinal stability augmentation is achieved by using an onboard computer system to calculate control surface deflection based on the sensed pitch rate of the aircraft and pilot elevator commands. The quantitative feedback theory controller was implemented on this computer system to provide acceptable handling characteristics for a large portion of the UAV's flight envelope. The flight tests of the UAV, which resulted in the successful completion of an entire flight at a 2.5% static margin, are also described.

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