THE APPLICATION OF SCHEDULED H-INFINITY CONTROLLERS TO A VSTOL AIRCRAFT

This paper applies H(infinity)-designed controllers to a Generic VSTOL Aircraft Model (GVAM) developed by the Royal Aerospace Establishment. The design study motivates the use of H(infinity) techniques, and addresses some of the implementation issues which arise for multivariable and H(infinity)-designed controllers. Controllers designed by the H(infinity) approach can cause more of a problem than classically-designed controllers when it comes to gain scheduling. An approach for gain scheduling H(infinity) controllers from the normalized coprime factor robust stabilization problem formulation used for the H(infinity) design is developed. It utilizes the observer structure of this particular robustness optimization. A weighting selection procedure has been developed for the associated loop-shaping technique used to specify performance. Multivariable controllers pose additional problems in the event of actuator saturations, and a desaturation scheme which accounts for this is applied to the GVAM. A comprehensive control law is developed and evaluated using the Royal Aerospace Establishment piloted simulation facility at Bedford.