Multi-Input MultiOutput Model-Following Control Design Methods for Rotorcraft

Abstract

Two methods of multi-input multioutput (MIMO) command-model-following control design are compared for rotorcraft flight control. The first, explicit model following (EMF), employs single-input single-output inverse plants with a dynamic decoupling matrix, which is a purely feed-forward approach to inverting the plant. The second is dynamic inversion (DI), which involves both feed-forward and feedback path elements to invert the plant. The EMF design is purely linear, while the DI design has some nonlinear elements in vertical rate control. For each of these methods, an architecture is presented that provides angular rate model following with selectable vertical rate model following. Implementation challenges of both EMF and DI are covered, and methods of dealing with them are presented. These two MIMO model-following approaches are evaluated regarding (1) fidelity to the command model and (2) turbulence rejection. Both are found to provide good tracking of commands and reduction of cross coupling.