Residualization of an Aircraft Linear Aeroelastic Reduced Order Model to Obtain Static Stability Derivatives

Abstract

Adverse aeroservoelastic (ASE) interaction is a problem in modern high performance aircraft that merits continued study and analysis. Interactions between the aircraft structure, the aerodynamics and flight control system can lead to oscillations which can be divergent and cause catastrophic failure. Flight testing is, and will continue to be, an integral part of validating a flight vehicle for adverse ASE prevention. With the increasing speed and efficiency of today's modern computers, higher fidelity analysis of the ASE problem (including CFD and non-linear finite element models) is achievable. However, simulation with these higher fidelity methods is still not rapid enough for flight control system design. A reduced order model (ROM) can be created, which is based on the high fidelity solution linearized around an operating point. This ROM, although simplified, still retains much of the valuable information that the high fidelity computational model provides. The ROM provides a means for much faster simulation, lending itself valuable for FCS design. While providing a means for much more rapid simulation, this ROM also serves other uses and contains a wealth of information. One use of the aeroelastic ROM that is exploited in this study is residualization of the ROM for the extraction of static stability derivatives. Traditional stability derivatives, which are based on a rigid body model, will differ from those that are a result of the residualization process described herein. The stability derivatives that result from this method will include the flexible structure effects that the ROM contains.