Geometry Based Design Automation Applied to Aircraft Modelling

103 Pages·2011·1.83 MB·English

by  Kristian Amadori

LINKÖPING STUDIES IN SCIENCE AND TECHNOLOGY.
DISSERTATIONS, NO. 1418

Geometry Based Design Automation
Applied to Aircraft Modelling and Optimization

Kristian Amadori
Copyright ©Kristian Amadori, 2012
“Geometry Based Design Automation – Applied to Aircraft Modelling and Optimization”
Linköping Studies in Science and Technology. Dissertations, No. 1418
ISBN 978-91-7519-986-3
ISSN 0345-7524
Printed by: LiU-Tryck, Linköping
Distributed by:
Linköping University
Division of Machine Design
Department of Management and Engineering
SE-581 83 Linköping, Sweden
Tel. [phone]
http://www.liu.se
To Isac
A perfection of means, and confusion of aims, seems to be our main problem.
Albert Einstein
ABSTRACT

Product development processes are continuously challenged by demands for increased efficiency. As
engineering products become more and more complex, efficient tools and methods for integrated
and automated design are needed throughout the development process. Multidisciplinary Design
Optimization (MDO) is one promising technique that has the potential to drastically improve
concurrent design. MDO frameworks combine several disciplinary models with the aim of gaining a
holistic perspective of a system, while capturing the synergies between different subsystems. Among
all disciplines, the geometric model is recognized as playing a key role, because it collects most of the
data required to any other disciplinary analysis.
In the present thesis, methodologies to enable multidisciplinary optimization in early aircraft design
phases are studied. In particular, the research aims at putting the CAD geometric model in the loop.
This requires the ability to automatically generate or update the geometric model, here referred to
as geometry-based design automation.
The thesis proposes the use of Knowledge Based Engineering (KBE) techniques to achieve design
reuse and automation. In particular, so called High Level CAD templates (HLCts) are suggested to
automate geometry generation and updates. HLCts can be compared to parametric LEGO® blocks
containing a set of design and analysis parameters. These are produced and stored in libraries, giving
engineers or a computer agent the possibility to first topologically select the templates and then
modify the shape of each template parametrically.
Since parameterization is central to modelling by means of HLCts, a thorough analysis of the subject
is also performed. In most of the literature on MDO and KBE two recurring requirements concerning
the geometrical model are expressed: the model should be flexible and robust. However, these
requirements have never been properly formulated or defined. Hence, in the thesis a mathematical
formulation for geometry model robustness and flexibility are proposed. These formulations
ultimately allow the performance of geometric models to be precisely measured and compared.
Finally, a prototyping and validation process is presented. The aim is to quickly and cost-effectively
validate analytical results from an MDO process. The proposed process adopts different
manufacturing techniques depending on the size and purpose of the intended prototype. In the last
part of the thesis, three application examples are presented. The examples are chosen from research
projects that have been carried out at Linköping University and show how the proposed theoretical
results have been successfully employed in practice.
There's a way to do it better - find it.
Thomas A. Edison
SAMMANFATTNING

Kraven på ökad effektivitet utmanar ständigt produktutvecklingsprocessen. I och med att
ingenjörsprodukter blir allt mer komplexa, växer genom hela utvecklingsprocessen behovet av
verktyg och metoder för integrerad och automatiserad design. Multidisciplinär Design Optimering
(MDO) är en lovande teknik som kan drastiskt förbättra parallell design. I ett MDO ramverk är flera
disciplinära modeller sammankopplade för att uppnå ett holistiskt systemperspektiv, men där
synergierna mellan olika delsystem också kan fångas upp. Bland alla möjliga discipliner spelar
geometrimodellen en central roll, eftersom den innefattar en stor del av all information som är
nödvändig för andra disciplinära analyser.
I avhandlingen studeras ett flertal metoder för att möjliggöra multidisciplinär optimering i de
tidigaste faserna av flygplansdesign. I synnerlighet är forskningen riktad mot att införa geometriska
CAD modeller i designloopen. Det blir därmed nödvändigt att kunna automatiskt generera eller
uppdatera geometriska modeller, vilket i avhandlingen kallas för ”geometribaserad design
automation”.
Avhandlingen förordar att Knowledge Based Engineering (KBE) tekniker används för att
konstruktioner skall kunna automatiseras och återanvändas. Så kallade Hög Nivå CAD mallar (på
engelska High Level CAD templates – HLCts) föreslås för att automatiskt generera och uppdatera
geometrimodeller. HLCts kan jämföras med parametriska LEGO® klossar som innehåller variabler för
design och analys. Mallarna kan samlas i bibliotek; därefter har konstruktörer eller dator agenter
möjligheten att först topologiskt välja en mall och sedan ändra på dess utförande genom utvalda
parametrar.
Eftersom parameterisering är ett centralt begrepp för HLCt principen, föreslås även en fördjupad
analys av ämnet. I stor del av MDO och KBE litteraturen ställs det två återkommande krav på
geometrimodellen: modellen bör vara flexibel och robust. Eftersom dessa krav aldrig har getts en
formell formulering, förordas i avhandlingen en matematisk beskrivning av modellrobusthet och -
flexibilitet. Tack vore formuleringen är det möjligt att noggrant mäta och jämföra till vilken grad
geometriska modeller fungerar.
Slutligen presenteras en valideringsprocess baserad på kostnadseffektiva prototyper som används
för att snabbt bekräfta analytiska resultat från MDO ramverket. Den föreslagna processen nyttjar
olika tillverkningsmetoder, beroende på prototypens tänkta storlek och användning. I sista delen av
avhandlingen presenteras även tre applikationsexempel, valda från forskningsprojekt som har
bedrivits på Linköpings universitet och som visar hur de teoretiska resultaten har kommit till
användning i praktiken.

ACKNOWLEDGEMENTS

The research presented in this thesis was carried out at the Division of Machine Design at Linköping
University. First, I would like to thank my supervisor Prof. Petter Krus for his guidance and for giving
me the opportunity to embark on this long journey. For all discussions, constructive critiques,
suggestions and support, I would also like to express my sincere gratitude to my co-supervisors, Prof.
Johan Ölvander and Dr Christopher Jouannet.

I would like to dedicate a special mention to the co-writers of all the papers I have both listed and
appended to this thesis. Without your contribution my research would certainly have looked very
different. In particular, I owe special thanks to Mehdi Tarkian and David Lundström, with whom I
have worked closely during the final period of my carrier as a Ph.D. student.

I would also like to thank all my colleagues at the University: I could not imagine a better work
environment than the one we have shared. I have received so many suggestions, ideas, hints, and
thoughts and so much good advice from so many of you that I would not even know where to begin
to address them all. Thank you all!

The research project has received funding from the National Aviation Engineering Research
Programme (NFFP) and the ProViking research program, which I hereby gratefully acknowledge.

Last, but certainly not least, I want to thank my wife Ingrid and my wonderful son Isac for motivating
me in anything I do and always being a great source of inspiration.

Linköping, December 2011

Kristian Amadori