Flight Control Law Design for a Civil Aircraft using Robust Dynamic Inversion

Abstract

A Robust Dynamic Inversion (RDI) flight control law is designed for a large civil aircraft. Classical Dynamic Inversion (CDI) consists of a nonlinear part that linearizes the nominal system dynamics, and a linear part, basically PID control, that imposes the desired closed-loop dynamics. However, CDI controllers have very poor robustness properties since they rely on exact availability of the system dynamics. It is well-known that within the Structured Singular Value (SSV), or µ-framework one can explicitly deal with systems subject to uncertainties. This holds for both, the analysis as well as for the synthesis problem. It is shown that µ-synthesis in combination with Dynamic Inversion (DI) provides robust control solutions that are also gain-scheduled. We first design a CDI controller. The exact robustness deterioration is quantified by a parameter sensitivity study using µ-analysis and nonlinear simulations. Next, an RDI controller is designed. The achieved robustness improvements are demonstrated using µ-analysis and nonlinear simulations.