Journal of Aeronautics, Astronautics and Aviation, Series A, Vol.38, No.1, pp.027 - 034 (2006) 27
Flutter Control Synthesis of Thin Plates Using Active
Lumped Vortex Excitations
*
Li-Jeng Huang ** and Te Jen
Department of Civil Engineering, National Kaohsiung University of Applied Science No. 415, Chien-Kung Road, Kaohsiung 807, Taiwan, R.O.C.
ABSTRACT
This paper presents a numerical study on the flutter suppression of a two-degrees-of-freedom typical section in two-dimensional incompressible flow using active lumped vortex excitations. Unsteady aerodynamic loads induced by structural deformations and active lumped vortex excitations are calculated by the lumped vortex method (LVM). The computational unsteady aerodynamic loads are checked with Theodorsen analytical solutions and Bratt’s experimental results. Unsteady pressure difference distributions, lift and pitching moment variations due to active lumped vortex excitations located at various positions were studied. Finally, state-feedback control of flutter was tested using different proportional gains and vortex excitation positions. The results show that fluttering plate can be effectively controlled using active lumped vortex excitation with appropriate chosen feedback gains and excitation locations. The mechanism of flutter suppression is the lumped vortex excitations induced secondary unsteady aerodynamic loads effectively alleviate the structural motions induced primary flow fields through the Biot-Savart law and the satisfaction of Kelvin condition.
Keywords: Aero-servo-elastic analysis, Active lumped vortex excitations, Lumped vortex method (LVM)
*
Manuscript received, Dec. 01, 2004, final revision, Apr. 20, 2005
** To whom correspondence should be addressed, E-mail: [email protected]
I. INTRODUCTION
Aero-servo-elastic analysis has become an important task in design of elastic structures with slender cross section such as thin airfoils of aircrafts in aeronautical engineering and suspension bridge decks in civil engineering. Recently, various passive and active control techniques are developed for suppression of vibration and/or flutter of elastic structures. Passive methods include mass balancing, stiffness tuning, speed restriction and aero-elastic tailoring [1]. Active control technologies such as active tendon, tuned mass and damper system, active appendage, etc., have been widely employed in the vibration suppression of structures subjected to wind loadings in civil engineering applications [2]. On the other hand, the aerodynamic control surfaces (leading- and trailing-edge flaps, ailerons, spoilers, and additional vanes) [3,4], active acoustic excitations [5-8], etc. have
also been successfully applied to flutter suppression and gust load alleviation. However, these classical flutter control devices using aerodynamic control surfaces require large power for activating the hydro-servo systems and are usually sluggish in response to high-frequency oscillations; while flutter control using active acoustic excitations possesses the intrinsic noise problem though it was proved to be effective.
In this paper we attempt to propose an innovative active control technique using lumped vortex excitation for flutter suppression of thin plates. The control input can be obtained by the use of a pair of jet flow with reversal directions at the upper and lower surface of thin plate. In the first stage we consider the suppression of flutter of a typical section model oscillating in two-dimensional incompressible flow regime. A correct analysis of unsteady aerodynamics induced by the structural deformations and active lumped vortex
