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Real Time Drag Minimization
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
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.
Trita-AVE, ISSN 1651-7660 ; 2006:62
Keyword [en]
Aeronautics, optimization, experimental verification
National Category
Vehicle Engineering
URN: urn:nbn:se:kth:diva-4114OAI: diva2:10796
2006-10-11, S40, Teknikringen 8, b.v., Stockholm, 13:00
QC 20101116Available from: 2006-09-22 Created: 2006-09-22 Last updated: 2010-11-16Bibliographically approved
List of papers
1. Real time drag minimization using redundant control surfaces
Open this publication in new window or tab >>Real time drag minimization using redundant control surfaces
2006 (English)In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 10, no 7, 574-580 p.Article in journal (Refereed) Published
Abstract [en]

A method for minimizing the drag of a wind tunnel model with multiple control surfaces is presented. The minimization is performed in the wind tunnel and measurements are performed in real time. Real time measurements introduce difficulties such as noise in the signals, hysteresis and problems with repeatability of the function evaluations. The lack of a numerical function to minimize therefore puts certain demands on the optimization method, and hence a derivative free method, often referred to as a generating set search method, is used. The proposed method is generalized to take both linear equality constraints as well as linear inequality constraints into account. The generating set search method is implemented in the wind tunnel and tests show that the drag can be decreased while satisfying the constraints.

Performance optimization, Real time computing, Wind tunnel testing, Direct search method
National Category
Vehicle Engineering
urn:nbn:se:kth:diva-10953 (URN)10.1016/j.ast.2006.05.002 (DOI)000241577500003 ()2-s2.0-33749664340 (ScopusID)
QC 20100720Available from: 2009-08-27 Created: 2009-08-27 Last updated: 2010-12-06Bibliographically approved
2. Drag Minimization of an Active Flexible Wing with Multiple Control Surfaces
Open this publication in new window or tab >>Drag Minimization of an Active Flexible Wing with Multiple Control Surfaces
(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
urn:nbn:se:kth:diva-7269 (URN)
QS 20120327Available from: 2007-06-01 Created: 2007-06-01 Last updated: 2012-03-27Bibliographically approved

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