A Reduced-Order Model for LCO Dependence on Mach Number in F16 Flight Tests

Nayfeh, Ali H.; Hajj, Muhammad R.; Nayfeh, Samir A.; Chabalko, Christopher; Beran, Philip S.

doi:10.2514/6.2008-1755

Cited by 2 publications

(2 citation statements)

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“…For aeroelastic systems, such as wing/store configurations, the development of reduced-order models is not straightforward due to the additional aerodynamics and structural aeroelastic aspects associated with the store and their effects on the wing characteristics (Gern and Librescu, 1998; Melville, 2002; Toth et al, 2002; Johnson and Denegri, 2003; Khot et al, 2003; Beran et al, 2004a; Attar et al, 2005; Bennani et al, 2005; Byreddy et al, 2005; Denegri and Dubben, 2005; Parker et al, 2006; Kurdi et al, 2007; Terashima and Fujii, 2007; Thomas et al, 2007; Abbas et al, 2008). On the aerodynamic side, flow patterns over the store may result in loads that may excite different aeroelastic responses in different flow regimes (Cunningham, 1998; Nayfeh et al, 2008). From a structural perspective, the presence of stores certainly varies the mode shapes, adds nonlinear aspects, and would thus have an impact on the wing instabilities.…”

Section: Introductionmentioning

confidence: 99%

Discretization effects on flutter aspects and control of wing/store configurations

Nayfeh

Hammad

Hajj

2011

Journal of Vibration and Control

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Two discretization approaches are considered for the prediction of the flutter characteristics of the Goland+ wing with a store. In one approach, referred to as an uncoupled-mode approach, the common notion that neglects the store when generating the basis functions is considered. This approach results in uncoupled mode shapes of the bending and torsion motions. In the second approach, referred to as semi-coupled-mode approach, coupling between the bending and torsion motions due to the shear force and moment exerted by the store at the tip of the wing are taken into account. It is found that the two approaches yield different instability parameters and characteristics. Through comparison with the exact solution, it is found that the semi-coupled-mode approach correctly predicts the natural frequencies of the wing/store system and the speed and type of the instability, whereas the uncoupled-mode approach fails to predict the natural frequencies of the structure, overestimates the instability speed, and fails to predict the type of instability. The usefulness of a physics-based discretization approach used to assess control schemes and effects of gains on the flutter speed and type of instability is demonstrated.

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Section: Introductionmentioning

confidence: 99%

Discretization effects on flutter aspects and control of wing/store configurations

Nayfeh

Hammad

Hajj

2011

Journal of Vibration and Control

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“…In fact, virtually all real systems behave nonlinearly if their inputs are large enough. There is increasing interest in nonlinear dynamic phenomena in automotive, aerospace [1][2][3], micro [4,5] and biological systems [6].…”

Section: Introductionmentioning

confidence: 99%

System Identification of Dynamic Systems With Cubic Nonlinearities Using Linear Time-Periodic Approximations

Allen

Sracic

2009

Volume 4: 7th International Conference on Multibody Systems, Nonlinear Dynamics, and Control, Parts A, B and C

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This work develops methods to identify parametric models of nonlinear dynamic systems from response measurements using tools for Linear Time Periodic (LTP) systems. The basic approach is to drive the system periodically in a stable limit cycle and then measure deviations of the response from that limit cycle. Under certain conditions, the resulting response can be well approximated as that of a linear-time periodic system. In the analytical realm it is common to linearize a system about a periodic trajectory and then use Floquet analysis to assess the stability of the limit cycle. This work is concerned with the inverse problem, using a measured time-periodic response to derive a nonlinear dynamic model for the system. Recently, a few new methods were developed that facilitate the experimental identification of linear time periodic systems, and those methods are exploited in this work. The proposed system identification methodology is evaluated by applying it to a Duffing oscillator, demonstrating that the nonlinear force-displacement relationship can be identified without a priori knowledge of its functional form. The proposed methods are also applied to simulated measurements from a cantilever beam with a cubic nonlinear spring on its tip, revealing that the model order of the system and the displacement dependent stiffness can be readily identified.

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A Reduced-Order Model for LCO Dependence on Mach Number in F16 Flight Tests

Cited by 2 publications

References 4 publications

Discretization effects on flutter aspects and control of wing/store configurations

Discretization effects on flutter aspects and control of wing/store configurations

System Identification of Dynamic Systems With Cubic Nonlinearities Using Linear Time-Periodic Approximations

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