Dynamic Modeling of Large-Scale Morphing Aircraft

Abstract

The dynamics of morphing flight, in which large changes in structural geometry may occur, include various components that are not apparent in the standard rigid flight equations. The additional terms include parameter and/or time varying aerodynamic forces and inertial forces due to relative motion. Here we study the importance of the inertial forces and moments, in particular those involving rate terms, with the goal of reducing the dynamics that must be considered in a flight control design. The dynamics are analyzed within the framework of the standard longitudinal flight assumptions and an example is given, constructed to be typical of a modern large-scale morphing aircraft. I. Introduction Modern aircraft are capable of large payload transport, extreme-maneuverability, high speeds, high altitudes, and long ranges; they are capable of stealth, vertical take-off and landing, and unmanned flight. Of course, no one design possesses all of these qualities. In fact, aircraft designs may be radically different depending on the operational requirements. The reason for varying aircraft designs is that, due to atmospheric interactions, mission capability is dictated predominantly by structural geometry. As a result, while a rigid aircraft may be designed to perform exceptionally in some given flight regime, another can be found in which the performance is relatively poor. An apparent remedy to this situation is to provide the necessary shape altering capability that would enable a single aircraft to encompass a larger range of performance. Morphing aircraft are flight vehicles that alter their shape to effectuate a change in either mission performance and/or to provide control authority for maneuvering. Aircraft with morphing capability promise the distinct advantage of being able to fly multiple types of missions and to perform extreme maneuvers not possible with conventional aircraft designs. The most current US sponsored morphing program is DARPA’s Morphing Aircraft Structures (MAS) program. This program was initiated with goal of researching larger wing shape changes than have been previously investigated. Under the MAS program a morphing aircraft was defined as a multirole platform that: • Changes its state substantially to adapt to changing mission environments.