Response and recovery of an MRAC adaptive flight control system to adverse atmospheric encounters

Abstract

Safety in air transport has always been of paramount importance. The very nature of aircraft navigating through the atmosphere brings with it associated risks and dangers. Some of these dangers are manifested in the form of adverse atmospheric disturbances. Two common examples of these atmospheric disturbances are the microburst and the wake vortex. This thesis explores the response and recovery performance of a General Aviation-based Model Reference Adaptive Control (MRAC) control system when subjected to these atmospheric disturbances. For the microburst condition, an existing 3DOF MRAC controller developed through prior research is integrated with nonlinear aerodynamics and an envelope protection scheme that augments the flight envelope of a Beechcraft Bonanza/CJ-144 as it encounters conditions pursuant to a microburst condition. Through simulation, the envelope protection scheme is shown to improve the chances of safe recovery in the event of a microburst encounter, by limiting the amount of total kinetic energy loss as the aircraft enters the microburst. For the wake vortex condition, an existing 6DOF MRAC controller is used as a baseline, to which a custom-developed 3D wake vortex model is added. Nonlinear components are incorporated into the existing linear aerodynamics, along with an envelope protection scheme. Pilot-in-the-loop simulated flight testing is conducted to evaluate recovery performance under three control modes: controller only, controller with pilot, and pilot only without controller. The control modes with the controller active are shown to yield much better recovery performance in the event of a wake vortex encounter. Additional efforts include the complete development of a MATLAB/Simulink-based 6DOF Aircraft Motion Visualizer and an X-Plane-based external simulation interface, both used as tools to aid in analysis of results and simulated flight testing.