Towards an advanced nonlinear rotorcraft flight control system design

Traditional rotorcraft flight control designs rely heavily on plant models which have been linearized about various operating set points. These designs are only valid for operating conditions close to the original trim points and suffer performance degradations for significant deviations. Consequently, several linear controllers are designed and scheduled to cover the operational flight envelope. An alternate approach that uses the inherent nonlinearities of the plant model may provide improved performance. Described herein are the initial results of a rotorcraft control design methodology that uses an aircraft-model-based transformation to convert the input-output map of the original nonlinear plant into a linear time-invariant system. The validity of the design technique for attitude stabilization is evaluated in a high-fidelity computer simulation of the UH-60 Black Hawk helicopter