Flight-Test Results of Autonomous Airplane Transitions Between Steady-Level and Hovering Flight

Copyright © 2007 by Eric N. Johnson, Allen Wu, James C. Neidhoefer, Suresh K. Kannan, and Michael A. Turbe. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission.Digital Object Identifier: 10.2514/1.29261Linear systems can be used to adequately model and control an aircraft in either ideal steady-level flight or in ideal hovering flight. However, constructing a single unified system capable of adequately modeling or controlling an airplane in steady-level flight and in hovering flight, as well as during the highly nonlinear transitions between the two, requires the use of more complex systems, such as scheduled-linear, nonlinear, or stable adaptive systems. This paper discusses the use of dynamic inversion with real-time neural network adaptation as a means to provide a single adaptive controller capable of controlling a fixed-wing unmanned aircraft system in all three flight phases: steadylevel flight, hovering flight, and the transitions between them. Having a single controller that can achieve and transition between steady-level and hovering flight allows utilization of the entire low-speed flight envelope, even beyond stall conditions. This method is applied to the GTEdge, an eight-foot wingspan, fixed-wing unmanned aircraft system that has been fully instrumented for autonomous flight. This paper presents data from actual flighttest experiments in which the airplane transitions from high-speed, steady-level flight into a hovering condition and then back again