Aeroelastic design optimization program

Dodd, A. J.; Kadrinka, K. E.; Loikkanen, Matti J.; Rommel, B.; Sikes, G. D.; Strong, R. C.; Tzong, T.

doi:10.2514/3.45977

Cited by 22 publications

(6 citation statements)

References 13 publications

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“…The quadratic scaling parameter is set to 500, and the required damping at the flutter speed, * , is set to 0.2. Using a non-zero * prevents an optimal structure from having a hump mode with a peak damping of nearly 0: a theoretically stable situation, but highly non-robust [30]. Critical !…”

Section: A Open-loop Fluttermentioning

confidence: 99%

Static and Dynamic Aeroelastic Tailoring with Variable-Camber Control

Stanford

2016

Journal of Guidance, Control, and Dynamics

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This paper examines the use of a Variable Camber Continuous Trailing Edge Flap (VCCTEF) system for aeroservoelastic optimization of a transport wingbox. The quasisteady and unsteady motions of the flap system are utilized as design variables, along with patch-level structural variables, towards minimizing wingbox weight via maneuver load alleviation and active flutter suppression. The resulting system is, in general, very successful at removing structural weight in a feasible manner. Limitations to this success are imposed by including load cases where the VCCTEF system is not active (open-loop) in the optimization process, and also by including actuator operating cost constraints. I. IntroductionDistributed control surfaces along the trailing-edge of a wing structure can have a substantial impact upon the aeroelastic stiffness, mass, and damping properties of that structure [1]. The quasi-steady and unsteady deflection patterns/history of these control surfaces may be optimized during an aeroelastic tailoring procedure, alongside more traditional design variables such as structural thicknesses of the skins, spars, ribs, and stringers. Designing both sets of design variables at once allows the optimizer to take full advantage of the strong synergies that exist between the two. Quasi-steady flap deflections may be optimized for maneuver load alleviation and cruise drag (or fuel burn) reduction [2][3]. Unsteady flap deflections (where each control surface oscillates about its mean quasi-steady position) may be used for active flutter control, gust alleviation, ride quality control, etc. [4]- [7].Despite the efficacy of control surface rotations for aeroelastic optimization, two important considerations should be included in the process, in the form of design constraints. The first is rooted in certification concerns: will the aeroelastic response of the wing be sufficiently safe in the unlikely event that the control surfaces are inactive? This risk may be mitigated by increasing the level of importance of open-loop load cases (where control surfaces are not actuated/included) relative to closed-loop cases (where they are) during the optimization process. As is often the case with aerospace systems [8], there is a strong trade-off between this form of risk reduction and overall structural performance (weight, e.g.). Design constraints attached to open-loop cases will dilute the effectiveness of the control surface actuation design variables.A second consideration may be the cost to actuate the control surfaces, measured in terms of the work done by applied hinge moments, or controller cost metrics. Distributed control surfaces are adept at maneuver load alleviation, for example, but maintaining large deflections under strong aerodynamic loading may increase the overall operating costs of the airplane. As above, one may expect a trade-off between these actuation cost metrics and the aeroelastic performance of the control surfaces. In addition to actuation cost metrics, constraints which recognize actuation limitatio...

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Section: A Open-loop Fluttermentioning

confidence: 99%

Static and Dynamic Aeroelastic Tailoring with Variable-Camber Control

Stanford

2016

Journal of Guidance, Control, and Dynamics

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“…The design flutter speed, V fmin , and design divergence speed, V imin , were both set to 250-0 ms-1 at an air density of 1-225 kgnr 3 , and the maximum material stresses are given in Table 4. The aerodynamic pitching moment was calculated using a C mo value of -0-04 and an airspeed of 210 ms-'.…”

Section: Optimisation Resultsmentioning

confidence: 99%

“…Considering the sensitivities for the quadratically linked thickness design variables, see Table 1, the maximum permissible error (i was limited to 1 x 10- 3 . Substituting values of V imin = 250 ms-' and Xj = 1 into Equation (A3) gives, o < -.…”

Section: Appendix: Accuracy and Step Size Selectionmentioning

confidence: 99%

Aeroelastic optimisation of composite wings using the dynamic stiffness method

et al. 1997

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A computer program for use in the conceptual stage of aircraft design has been developed. The program obtains minimum mass designs for high aspect ratio, composite wings, subject to constraints on flutter speed, divergence speed and material stress. The wing is modelled as a series of composite beam elements and both flutter speed and divergence speed are calculated using a normal mode approach. Modal analysis is carried out by applying the Wittrick-Williams algorithm to the dynamic stiffness method, whereas unsteady aerodynamic loads are calculated from strip theory, although an option which uses lifting-surface theory is also presented. A previously published example is given to validate the analysis. Single level optimisation is carried out using a sequential quadratic programming strategy combined with the modified methods of feasible directions optimizer, for which flutter sensitivities are obtained by an efficient determinant interpolation technique. Design variables include topological variables such as spar and engine positions as well as layer thicknesses, which are modelled using quadratic functions. The wing of a regional turboprop aircraft is optimized to illustrate the use of the program. The problem was modelled using 10 elements and had 43 design variables, 162 constraints and required just over 20 minutes of CPU time on a workstation. This, coupled with the fact that a full three-dimensional FE model of the same wing would require over 1000 elements, illustrates the suitability of the dynamic stiffness method to the conceptual design stage.

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“…ADOP (aeroelastic design optimisation program) (Dodd et al 1990) is an interdisciplinary optimisation program for static, dynamic and aeroelastic analysis using finite element structural models. Developed by the Douglas Aircraft Company, ADOP incorporates FSD concepts, static aeroelasticity and flutter constraints in optimisation.…”

Section: Software Toolsmentioning

confidence: 99%

Recent progress in dynamics and aeroelasticity

Upadhya

Panda

1994

Sadhana

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With the emphasis on higher performance, modern aircraft designs aim at lower structural weight, aerodynamically efficient thinner configurations, and reduced or even negative stability margins augmented by automatic flight control system s. These design considerations lead to highly flexible structural designs with associated problems of dynamic and aeroelastic interactions which need to be considered at the preliminary design stage itself. Advent of advanced composites and active control techniques have given the aircraft designer the freedom to use aeroelastic interactions in an advantageous way. This paper reviews the recent research and development efforts in the areas of aeroelastic tailoring, structural optimisation with aeroelastic constraints and aeroservoelasticity, and applications of the same in practical designs. The developments and applications in India in these areas are also highlighted.

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Aeroelastic design optimization program

Cited by 22 publications

References 13 publications

Static and Dynamic Aeroelastic Tailoring with Variable-Camber Control

Static and Dynamic Aeroelastic Tailoring with Variable-Camber Control

Aeroelastic optimisation of composite wings using the dynamic stiffness method

Recent progress in dynamics and aeroelasticity

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