UAV airplane control system design via time-scale separation technique

The problem of UAV airplane trajectory tracking control system design is treated in the presence of uncertain aerodynamics and unknown external wind disturbances. The cascaded control system structure is considered where the feedback loop of the each cascade is designed by inducing of two-time-scale motions in the closed-loop system such that the controller dynamics is a singular perturbation with respect to the airplane dynamics. The time-scale separation method is used to analyze of fast and slow motions in the closed-loop system and in order to get explicit expressions for evaluation of the controller parameters. Stability of fast-motion transients is maintained by selection of controller parameters while the slow motion behavior of such controlled variables as Euler angels and angular velocities exhibit the desired transient's performances for a large range of aerodynamic characteristics variations and external wind disturbances. Simulation results are included to validate the effectiveness of the discussed design methodology.