Design of helicopter flight control systems using eigenstructure assignment

A flight control system for enhancement of helicopter handing qualities is presented, and its robustness properties are analyzed. A design methodology that uses a combination of eigenstructure assignment and classical techniques to obtain desired dynamic response characteristics for high-performance helicopters is developed. The control laws designed using this methodology yield excellent dynamic response when applied to the design model. Stability robustness is evaluated using structured singular values and evaluation of mathematical models which include substantial variations in the aerocoefficients from their nominal values. The results of these tests reveal that although handling qualities are still acceptable, certain combinations of parameter variations can destabilize the helicopter, and certain commands can saturate the rate limits on the actuators