Optimeringsdriven design vid Saab Aerosystems

Jönköping, 7 Oktober, 2010Torsten Bråmå

Content

� Background

� Gripen

� Spacecraft adapter

� Aerodynamic optimization

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� Aerodynamic optimization

� Airbus A380

� Clean Sky – Smart Fixed wing aircraft

� Gripen NG

� Role of optimization in the design process

Complete aircraft responsibility

Gripen – multi-role fighter

Neuron – unmanned demonstrator in European cooperation, Dassault et al.

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Complete aircraft responsibility

Saab 2000 FE model

Saab 2000 AEW&C

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Saab 2000 FE model

FE model Gripen one and two seater versions

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Bakgrundverktyg för optimering av kompositvingar

För att utnyttja potentialen som finns i användningen av komposit i vingstrukturer behövs datorbaserade stöd för att klara jobbet.

Under perioden 1975-90 utvecklades sådana av flera tillverkare:• USA – TSO, ASTROS m.fl. (F16, F18, F22, F35 etc)• Storbritannien – Stars, ECLIPS (Eurofighter, Gripen vinge)• Frankrike – ELFINI (Mirage, Rafale, Neuron)• Tyskland – Lagrange (Eurofighter)

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• Tyskland – Lagrange (Eurofighter)• Sovjet – Argon (?)• Sverige – OPTSYS (Gripen vinge, fena, roder mm)

Under 90-talet började kommersiella verktyg utvecklas.

Idag finns Nastran Sol 200 som kan hantera en hel del av det ovanstående program klarar.

Bakgrundverktyg för strukturanalys och optimering på Saab

Omkring 1980 valdes FE-systemet ASKA för användning i projekten Gripen och Saab 340.

1983 påbörjades utvecklingen av OPTSYS (Saab, KTH, FFA), ett system för strukturoptimering integrerat med ASKA.

Under 1990-talet introducerades FE-systemet UAI-Nastran på Saab parallellt med ASKA. Nastran blir nära nog standard inom flygindustrin (undantag Dassault). Optsys integrerades med UAI-Nastran.

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Optsys integrerades med UAI-Nastran.

Saab går över till MSC-Nastran (Gripen Demo, Airbus, Boeing). (MSC köper upp UAI)

MSC-Nastran kan inte integreras med Optsys men har utvecklat egen optimering i form av Sol 200.

2007-2008 genomförs utvecklingsprojekt för att kunna använda Nastran Sol 200t.ex i projekten Gripen NG och Clean Sky.

Objective: Minimum weight

Constraints:• Free from flutter within flight envelope

• Control surface efficiency to assure aircraft performance

• Strain in carbon fibres

Gripen wing: Problem formulation

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• Panel buckling

• Design rules

Design variables:• Number of 0, 90 and +-45 degree composite layers

Composite material design variables:

90o � x2

0o � x1

+45o � x3

-45o � x3Total thickness

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� 3 design variables controlling each layup

symmetric

thickness

Composite material design rules included as constraints:

• Layer thickness treated as a discrete or continuous variable.

• Stack assumed to be well mixed, no explicit layup treated.

• Each layer direction between 10% and 70% of total panel thickness.

• Minimum / maximum total panel thickness

• Fiber strain < 0.43%

• Panel buckling criteria:

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• Panel buckling criteria:

Using in-house software integrated into Nastran.Panel layup and boundary loads received from Nastran.Additional input of panel size and boundary conditions required.

• Inner elevon deflected to achieve roll moment, Mx, at Mach 0.9

• Mx is reduced due to aeroelastic wing deformation

Gripen wing, control surface efficiency

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wing deformation

• Efficiency=Mx(elastic) / Mx(rigid)

• A to flexible wing can result in zero or negative efficiency

Structural analysis

MassFibre strain

Panel buckling

g(X) , dg/dX

Minimize Objective(X)

Gradient based optimization

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Flutter damping

Control efficiency

g(X) < gmax

Xmin < X < Xmax

Xn+1

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Objective: Minimum weight

Constraints:• Frequencies of first lateral and axial mode

• Static axial load distribution in lower joint

• Strain in carbon fibres

Spacecraft adapter: Problem formulation

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• Strain in carbon fibres

• Stress in upper aluminum ring

Design variables:• Thickness in upper aluminum ring (29 variables)

• Number of 0 and +-45 degree composite layers (96 variables)

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Event Date

Concept study Aug-Sep 1998

Request for proposal Oct 1998

Opt. Iteration #1 Oct 1998 (~ 3 weeks)

Contract awarded Dec 1998

Opt. Iteration #2 Jan 1999 (~ 4 weeks)

Spacecraft adapter: Schedule / Milestones

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Opt. Iteration #2 Jan 1999 (~ 4 weeks)

Hardware manufacturing May-Aug 1999

Test activities Oct 1999

Delivery to customer Nov 1999

Lift

Moment

• Objective function: minimize Drag

• Physical Constraints: - Constant Lift- Constant Pitching Moment- Flow Equations (transonic flow)

Aerodynamic shape optimizationIn-house progran Cadsos, ref. Per Weinerfelt

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Drag

Moment- Flow Equations (transonic flow)

• Geometrical Constraints:- Prescribed volume- Given wing thickness at specified locations

Aerodynamic Shape OptimizationAerodynamic Shape Optimization

XXX

KkMXCMXC

KkMXCMXC

MXCMin

kMkM

kLkL

kD

K

kk

≤≤=≥

=≥∗

∗

=∑

,...,1),,(),(

,...,1),,(),(

),(

maxmin

1

λ

Drag minimization under lift, moment and geometrical constraints

original

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equationsflowStokesNavierEuler

XXX

−≤≤

/maxmin

λk are weights, X design parameters and Mkdifferent Mach numbers

Saab has participated in the EU-projectAeroshape.(Aerodynamic Shape Optimization)

Pressure distr. over an original and optimized SCT

optimized

Coupled Structure/Aerodynamic OptimizationCoupled Structure/Aerodynamic Optimization

)()( 21 XCXwMin Dλλ +

StructureFE-models

FlutterUnsteady aero

model

Drag and weight minimization under physical and geometrical constraints

Design variables X:•Wing thickness•Wing twist •Wing profile •Structural dimensions

Steady

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X

ff

∂∂

,

Static aeroelasticityNeutral model

Redesign1+nX

Saab has experience from the EU-projectsMDO and MOB. Also applied for internal military aircraft wing studies.

•Structural dimensions

Constraints:•Lift and moment•Stress, panel buckling•Flutter, control surface efficiency•Manufacturing requirements•Geometry

Steady Aerodynamics

AIRBUS A380

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AIRBUS A380

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Optimization study: Track Rib 10 (A380-800)

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Programvara: Altair HyperWorks

HyperMesh• Geometrimodifiering, uppstädning

• Meshning och meshmodifiering (2D, tet, hex mm.)

• Översättning av indatafiler mellan program

• Definition av optimeringsproblem för exekvering i OptiStruct (målfunktion, bivillkor etc.)

• Applicering av formvariabler (Mesh Morphing)

• Postprocessor (mest HyperView)

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• Postprocessor (mest HyperView)

OptiStruct• Inbyggd linjär Fe-lösare

• Bygger på Nastran kod

• Linjär statik, egenfrekvens, linjärbuckling, gap-element

• Inbyggd optimerare – gradientmetod med störningsvektor som opererar på styvhetsmatrisen

ComparisonOriginal Track Rib 10 Topology optimized Track Rib 10

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Size and shape optimizationResults, part 3

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Clean Sky - Smart Fixed Wing Aircraft

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Key Smart Fixed Wing Aircraft technologies

Innovative Powerplant Integration� Technology Integration

� Large Scale Flight Demonstration

Smart Wing Technologies�Technology Development

�Technology Integration

� Large Scale Flight Demonstration

� Natural Laminar Flow (NLF)

� Hybrid Laminar Flow (HLF)

� Active and passive load control

� Novel enabling materials

� Innovative manufacturing scheme

SAGE ITD – CROR engine

SGO – Systems for Green Operation

Input connecting to:

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� Large Scale Flight Demonstration

� Impact of airframe flow field on Propeller design (acoustic, aerodynamic, vibration)

� Impact of open rotor configuration on airframe (Certification capabilities, structure, vibrations...)

� Innovative empennage design

TE– SFWA technologies for a Green ATS

Output providing data to:

ICAS conference Nice, 19.-24.Sept. 2010

SFWASFWA-- High Speed Demonstrator Passive High Speed Demonstrator Passive (HSDP)(HSDP)

Smart Passive Laminar Flow Wing� Design of an all new natural laminar wing

� Proof of natural laminar wing concept in wind tunnel tests

� Use of novel materials and structural concepts

� Exploitation of structural and system integration together with tight tolerance / high qualitymanufacturing methods in a large scale ground test demonstrator

� Large scale flight test demonstration of the laminar wing in operational conditions

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Port wing

Laminar wing structure concept option 2

Starboard wing

Laminar wing structure concept option 1

ICAS conference Nice, 19.-24.Sept. 2010

Worksharing to design and build the “HSDP” Smart Wing demonstrator

Wing Tip: Aernnova

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Aileron structure (INCAS)

Integrated upper cover (SAAB)

Integrated upper cover with structural concept (SAAB)

ICAS conference Nice, 19.-24.Sept. 2010

Clean Sky SFWA: FE model (Nastran)

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Clean Sky SFWA, Nastran SOL200 results,thickness distribution in composite upper panel and rear spar

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Gripen Demo

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Problem formulation

Parametric design

Role of optimization in the design process

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Analyses

OptimizationObjective function – to maximize

Constraints – to satisfy

Variables – parameters to modify

WeightCostSafety

Performance

• Weight reduction

• Finding feasible designs

• Evaluating and comparing design concepts

Role of optimization in the design process

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• Investigation of Cost–Performance relation

• Model updating with respect to test results

Examples of engineering tasks where optimization tools have proved to be useful

www.saabgroup.com

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