American Institute of Aeronautics and Astronautics 1 Residualization of an Aircraft Linear Aeroelastic Reduced Order Model to Obtain Static Stability Derivatives Brian P. Danowsky * , Peter M. Thompson, PhD, † Systems Technology, Incorporated, Hawthorne, CA, 90250 Charbel Farhat, PhD ‡ CMSoft, Inc., Palo Alto, CA 94306 and Chuck Harris, Ph.D. § 412 TW/ENTT, Air Force Flight Test Center, Edwards AFB, CA, 93524 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. I. Introduction In today’s modern high performance aircraft, adverse aeroservoelastic (ASE) interaction is a problem that warrants investigation both analytically and experimentally. Aeroservoelasticity is the field of study that describes the interaction between four disciplines: aerodynamics, structural dynamics, actuator dynamics and an active flight control system (Figure 1). In some descriptions the actuator dynamics are grouped with the flight control system to make up three disciplines. The incorporation of FCS dynamics, which includes control laws, actuators, sensor dynamics, and control surface mechanics, is the newer addition to the classical field of study of aeroelasticity. The complete dynamic system includes aspects from all of the four disciplines so an accurate system representation should include the influence of each discipline. This becomes especially important when the frequencies of the dynamics for each system are within close proximity to each other. When analyzing modern ASE problems, the higher frequency * Senior Research Engineer, Member of AIAA. † Chief Scientist, Member of AIAA. ‡ President, AIAA Fellow. § Aerospace Engineer. AIAA Atmospheric Flight Mechanics Conference and Exhibit 18 - 21 August 2008, Honolulu, Hawaii AIAA 2008-6370 Copyright © 2008 by Systems Technology, Inc. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. Downloaded by STANFORD UNIVERSITY on December 14, 2015 | http://arc.aiaa.org | DOI: 10.2514/6.2008-6370