Flight-Path Tracking Control of a Transportation Aircraft: Comparison of Two Nonlinear Design Approaches

For transport aircraft, the primary control objective for an autopilot system engaged during approach and landing is relative to the flight-path tracking on the basis of highly simplified linear models of flight dynamics. The dynamics governing the flight-path of an aircraft are in general highly nonlinear and involve complex physics for which no accurate models are available. In the past decades, some new nonlinear control design techniques appeared of interest for the development of improved control schemes for the flight-path tracking mode. In this communication, two nonlinear control techniques are used for the design of flight-path tracking control laws for a transport aircraft. A first control technique adopts a classical nonlinear dynamic inversion control scheme where enhanced robustness is introduced, and a second control scheme based on the backstepping technique is developed. These two approaches are compared in terms of applicability, complexity and robustness with respect to modeling inaccuracies and external perturbations. Finally, simulation results are displayed and discussed