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Open-Loop Control of LCO Phenomenon Using Magnetorheological Dampers

Open-Loop Control of LCO Phenomenon Using Magnetorheological Dampers Kleber A. L. Castão 1 , Luiz C. S. Góes 1 , José M. Balthazar 2 1 Tecnological Institute of Aeronautics – ITA, 2 São Paulo State University - UNESP. BACKGROUND. RESULTS. Aeroelasticity

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Open-Loop Control of LCO Phenomenon Using Magnetorheological Dampers

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  1. Open-Loop Control of LCO Phenomenon Using Magnetorheological Dampers Kleber A. L. Castão1, Luiz C. S. Góes1, José M. Balthazar2 1Tecnological Institute of Aeronautics – ITA, 2São Paulo State University - UNESP BACKGROUND RESULTS • Aeroelasticity • Aeroelasticity is the dynamic interaction of structural, inertial, and aerodynamic forces. Conventional methods of examining aeroelastic behavior have relied on a linear approximation of the governing equations which describe both the flow field and the structure. The nonlinear aeroelastic systems may exhibit nonlinear dynamic response characteristics such as limit cycle oscillations (LCOs), inter-internal resonances, and chaotic motion, (Lee, et.al., 1999). Flutter and Limit Cycle Oscillations (LCO) • Flutter is a self-feeding and potentially destructive vibration where aerodynamic forces on an object couple with a structure's natural mode of vibration to produce rapid periodic motion. • The flutter phenomena is a very special case in the aeroelasticity study, many authors dedicates years of its research in the resolution of this kind of problem. When a structural nonlinearity is considered in the aeroelastic model, that is, the nonlinearity is sufficiently strong, the flutter phenomenon becomes Limit Cycle Oscillations • MR application • Magnetorheological fluid is a smart material that possess an interesting propriety: it is possible to control the viscosity, passing of the liquid state to the almost solid state in milliseconds, through the control of the applied magnetic field. • when the fluid is inside of a damper, these magnetic particles align themselves in parallel to the magnetic field lines, forming a species of "chain". When the structure is submitted to a vibration, these "chains" break, wasting energy and, the magnetic field cause the resetting of this chains. • Trying to get positive answers in this study, we decided to make a simple application of MR device in a typical wing section, in order to study which would be the effect of this material with relation to the aeroelastic phenomena. The numerical simulations are carried out using the Wagner’s theory to modeling the aerodynamics forces and moments in the airfoil and the lineaar model of the typical section was used to find the nominal flutter velocity an the parameters found in Tang et. al. PURPOSE • The main purpose of this work is show the possibility of change of the LCO's amplitude, and the possibility of control of the velocity that these phenomena occur. • And the use of a Smart Material to obtain this results. PROBLEM FORMULATION CONCLUSIONS • After these simulations, is possible to conclude that the addition of this device in the system increases the flutter velocity, through the increase of the structural damping of the wing. In this case, flutter velocity is the velocity where the system starts to vibrate with large amplitude, then we have the LCO. • Is also possible to conclude, that we need of a closed-loop control to obtain these results in real time and great accuratelly. • is necessary to remember that this study is only theoretical, we do not know if this kind of experiment has been tried by anyone in somewhere, but we know that this experiment is extremely necessary for full acceptance of this study The equations of the problem are the following: Where and BIBLIOGRAPHY • Dyke. S. J., Spencer, B. F., Sain, M. K., Carlson, J. D., 1996, Phenomenological model of a Magneto-rheological damper. ACSE Journal of Engineering Mechanics. • Dowell, E.H., Crawley, E.F., Curtiss Jr., Peters, D.A., H.C., Scanlan, R.H., Sisto, F., 2008, “A Modern Course in Aeroelasticity”, Ed. Springer-Verlag, New York, USA, pp.746. • Fung, Y. C. 1969, An Introduction to the Theory of Aeroelasticity, Dover, NY. • Lee, B. H. K., Price, S. J. & Wong, Y. S. 1999, Nonlinear aeroelastic analysis of airfoils: Bifurcation and chaos, Progr. Aerosp. Sci. 35, 205–334. • Pierrick, J., 2006, Isolation vibratoire par contrôle semi-actif d’amortisseurs magnéto-rhéologiques pour l’interface lanceur/charge utile; Ph.D Thesis, Conservatoire National des Arts et M´etiers, ONERA.

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