TABLE OF CONTENTS This chapter discusses how to extend the design method outlined in the previous chapter to ?-synthesis and full six-degree-of-freedom aircraft models. It is based on work accomplished for the U.S. Air Force, Wright Laboratories, Flight Dynamics Directorate, Dayton, Ohio, under contract F33615 92 C 3607, "Application of Multivariable Control Theory to Aircraft Control Laws" (MCT).76 , 77 The objective was to develop design guidelines for the application of multivariable control theory to aircraft control laws. A similar study was conducted starting two years later by GARTEUR (Group for Aeronautical Research and Technology in EURope).78 In the U.S. Air Force study, flight control systems were developed for three different aircraft executing four different maneuvers using three different multivariable control design methods ( ?-synthesis, dynamic inversion, and eigen-structure synthesis). 79 81 Full nonlinear databases were used to satisfy nonlinear simulation requirements. Specifically covered in this chapter are the ?-synthesis multivariable control designs. This design work includes system performance validation using linear and nonlinear models and non-real-time nonlinear simulation. The RCAM (Research Civil Aircraft Model) and the HIRM (High Incidence Research Model) aircraft models were used for the GAUTEUR study.
The basic advantage for this approach is that multiple control loops are closed simultaneously, meeting a performance criterion. When using classical design methods, successive single-loop closures are performed, whereby the desirable characteristics achieved in the first closure may be lost in the second. This advantage is very important with the advent of control-configured vehicles and strong cross-coupling between vehicle axes.
