HIGH-ALPHA APPLICATION OF VARIABLE-GAIN OUTPUT-FEEDBACK CONTROL

This paper describes a recently developed variable-gain, optimal, discrete, output feedback design approach that is applied in a nonlinear flight regime. The flight regime covers a wide angle-of-attack alpha-range that includes the stall region. The paper contains brief descriptions of the variable-gain formulation, the discrete-control structure and flight equations used to apply the design approach, and the high-performance airplane model used in the application. Both linear and nonlinear analyses are shown for a longitudinal four-model integrated design case with alpha = 5, 15, 35, and 60 deg and two flight control modes. Nonlinear simulations show good time response for both a longitudinal pitch-up and pitch-down maneuver and a regulation within 5 deg from the nominal angle during a high-alpha lateral maneuver.