Robust Output Command Tracking for Linear Systems with Nonlinear Uncertain Structure with Application to Flight Control

The problem of asymptotic robust output command tracking is studied for the case of linear systems with nonlinear uncertain structure. The problem is solved using a compensator with static state feedback, unity output feedback and integral action. The controller is restricted to be independent from the uncertainties. The output of the closed loop system tracks polynomial type reference signals. Sufficient conditions for the problem to have a solution are established. The result of asymptotic robust output command tracking is applied to control the short period longitudinal motion of an aircraft. In the mathematical description of the aircraft an uncertain stability derivative is included. The steps to determine the controller are analytically presented. The effectiveness of the controller over a wide range of the system uncertainty, wind disturbances and actuator failure is illustrated through simulation to the nonlinear model.