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Drag Minimization of an Active Flexible Wing with Multiple Control Surfaces
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
(English)Article in journal (Other academic) Submitted
Abstract [en]

In this study, the performance of a highly flexible wing with multiplecontrol surfaces is optimized for different flight conditions. A windtunnel model with 20 independent control surfaces is used as the testobject. The problem is posed as a nonlinear optimization problem withthe measured drag as the objective. Constraints include keeping the liftconstant, as well as having bounds on the control surface deflections. Nocomputational estimation of the drag is performed. Instead, experimentalmeasurements of the drag are used to perform the optimization in realtime using a generating set search method (GSS). The algorithm makesthe wing adapt to the current flight condition to improve performanceand the experimental evaluation of the method shows that the drag issignificantly reduced within a wide range of flight conditions. A study onthe number of control surfaces needed is also included, and the resultsshow that, if chosen properly, only three control surfaces distributed overthe wing are needed to reduce drag significantly.

National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-7269OAI: oai:DiVA.org:kth-7269DiVA: diva2:12228
Note
QS 20120327Available from: 2007-06-01 Created: 2007-06-01 Last updated: 2012-03-27Bibliographically approved
In thesis
1. Aeroelastic Concepts for Flexible Aircraft Structures
Open this publication in new window or tab >>Aeroelastic Concepts for Flexible Aircraft Structures
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

In this thesis, aeroelastic concepts for increased aircraft performance are developed and evaluated. Active aeroelastic concepts are in focus as well as robust analysis concepts aiming at efficient analysis using numerical models with uncertain or varying model parameters.

The thesis presents different approaches for exploitation of fluid-structure interaction of active aeroelastic structures. First, a high aspect ratio wing in wind tunnel testing conditions is considered. The wing was developed within the European research project \textit{Active Aeroelastic Aircraft Structures} and used to demonstrate how structural flexibility can be exploited by using multiple control surfaces such that the deformed wing shape gives minimum drag for different flight conditions. Two different drag minimization studies are presented, one aiming at reduced induced drag based on numerical optimization techniques, another one aiming at reduced measured total drag using real-time optimization in the wind tunnel experiment. The same wing is also used for demonstration of an active concept for gust load alleviation using a piezoelectric tab. In all studies on the high aspect ratio wing, it is demonstrated that structural flexibility can be exploited to increase aircraft performance.

Other studies in this thesis investigate the applicability of robust control tools for flutter analysis considering model uncertainty and variation. First, different techniques for taking large structural variations into account are evaluated. Next, a high-fidelity numerical model of an aircraft with a variable amount of fuel is considered, and robust analysis is applied to find the worst-case fuel configuration. Finally, a study investigating the influence of uncertain external stores aerodynamics is presented. Overall, the robust approach is shown to be capable of treating large structural variations as well as modeling uncertainties to compute worst-case configurations and flutter boundaries.

Place, publisher, year, edition, pages
Stockholm: KTH, 2007. 31, 24, 16, 16, 16, 23 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2007:29
Keyword
aeroelasticity, active aeroelastic aircraft structures, aeroelastic control, wind-tunnel testing, flutter analysis, robust flutter analysis, worst-case configuration
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-4419 (URN)978-91-7178-706-4 (ISBN)
Public defence
2007-06-15, F3, Lindstedtsvägen 26, Stockholm, 13:15
Opponent
Supervisors
Note
QC 20100713Available from: 2007-06-01 Created: 2007-06-01 Last updated: 2010-07-13Bibliographically approved
2. Real Time Drag Minimization
Open this publication in new window or tab >>Real Time Drag Minimization
2006 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis focuses on the use of multiple redundant control surfaces to increase performance during flight. There is no clear-cut definition of performance. It may differ between applications, but here, the amount of drag for a given flight condition is used. The work is concentrated on minimizing drag with the use of measurements instead of numerical simulations. Measured data contains noise and there are problems with repeatability and hysteresis. These difficulties are considered and a method for drag minimization during flight is presented.

In the first study the drag minimization algorithm is discussed. Focus is put on describing the implemented method and the treatment of constraints to the optimization problem. The constraints include keeping the lift constant as well as having bounds on the control surface deflections.

In the second work, a more complex wind tunnel model is used to validate the drag optimization algorithm. Drag reduction for different flight conditions is studied, as well as the impact of the number of control surfaces. Different layouts of the control surfaces are also tested. The results show that the constraints are satisfied and that the drag is reduced substantially.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. 27 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2006:62
Keyword
Aeronautics, optimization, experimental verification
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-4114 (URN)
Presentation
2006-10-11, S40, Teknikringen 8, b.v., Stockholm, 13:00
Opponent
Supervisors
Note
QC 20101116Available from: 2006-09-22 Created: 2006-09-22 Last updated: 2010-11-16Bibliographically approved

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