ROBUST LONGITUDINAL AXIS FLIGHT CONTROL FOR AN AIRCRAFT WITH THRUST VECTORING

A full conventional envelope longitudinal axis control design is presented for a fighter aircraft capable of thrust vectoring. An inner-outer loop modular control structure is used to provide good flying quantities in the presence of highly structured uncertainty across a wide flight envelope. Simple, low-order control laws are designed for a version of an F-18 aircraft model augmented with thrust vectoring nozzles. A minimal-order H-infinity design algorithm is used to aid in the design of an inner loop equalization controller. Structured singular value synthesis is used to design outer loop implicit model-following controllers. Different control laws are found for high and low dynamic pressure conditions, and controller commands are blended for a small region of dynamic pressure. Daisy-chaining is used to blend elevator and thrust vectoring commands. Structured singular values are used to analyze stability robustness to structured parametric uncertainty, actuator and sensor unmodeled dynamics, and structured uncertainty corresponding to controller blending. A nonlinear simulation is used to show that the aircraft performs well across the Right envelope during outer loop controller blending and thrust vectoring actuation.