LMS Flutter Testing - ?· Gvt/Flutter/FEC LMS Flutter Analysis. ... 20 copyright LMS International -…

  • View
    213

  • Download
    0

Embed Size (px)

Transcript

  • Aerospace Testing 2011, Hamburg, Germany, April 6 2011Jan Debille Solutions Manager Aerospace & Defense

    Industrial solutions for in-flight & offline experimental flutter analysisA. Lepage, P. Naudin, J. Roubertier, A. Cordeau ONERAM.A. Oliver-Escandell, S. Leroy, AIRBUSJan Debille, LMS

  • 2 copyright LMS International - 2010

    Presentation outline

    Flutter testing: What, When and How?

    Validation

    Required technology

    Industrial implementation

    1

    5

    2

    3

    Conclusions

    4

  • 3 copyright LMS International - 2010

    What is Flutter?

    Flutter is an aero-elastic phenomenonUnstable self-excited vibrationStructure extracts energy from the air stream

    Flutter starts to occur at a certain speedNegative damping start to occur at flight points

    where two modes are coupled in an unstable wayTypical coupling: wing bending/torsion, wing

    torsion/control surface, wing/engine

  • 4 copyright LMS International - 2010

    Component CAE Component Physical Test

    Subsystem CAE Subsystem Physical Test

    Full Virtual Prototype Full Physical Test

    Perfo

    rman

    ce Ex

    plorat

    ion

    Perfo

    rman

    ce Ex

    plorat

    ion

    Component

    Concept Validation & Target

    Concept Validation & Target

    Cascading

    Cascading

    Certi

    ficati

    on

    Certi

    ficati

    on

    Upfront Engineering Detailed Engineering Refinement Engineering

    Full Aircraft

    Models &Loads

    Subsystem

    Feasibility Definition InServiceConcept Development

    Marke

    t Stud

    yCo

    ncep

    t Sele

    cted

    Agree

    ment

    With

    Prim

    ary Pa

    rtners

    Autho

    rity T

    o Offe

    rPr

    ogram

    Laun

    ch Major

    Asse

    mblie

    s

    Entry

    Into

    Servi

    ce

    Certi

    ficati

    on

    First

    Fligh

    t

    Major

    Bod

    y

    Secti

    ons

    Comp

    onen

    t De

    sign

    GVT/Flutter/FEC

    Stages of Aircraft Development & Flutter: When?

  • 5 copyright LMS International - 2010

    Flight Envelope Clearance

    Flutter in the design process flow

    Pre-Test & De-Risking

    Ground Vibration Test

    Identify & ValidateModes

    CorrelateModel

    GO-NO/GO First Flight

    Update / refine Models

    Virtual PrototypeFE Model

    Analytical Modal Model

    Physical Prototype

    Flutter Simulation &

    Prediction

    Define Flight Envelope

    Flight Envelope Opening

    Flight Envelope Expansion

    Feasibility Definition InServiceConcept Development

    Marke

    t Stud

    yCo

    ncep

    t Sele

    cted

    Agree

    ment

    With

    Prim

    ary Pa

    rtners

    Autho

    rity T

    o Offe

    rPr

    ogram

    Laun

    ch Major

    Asse

    mblie

    s

    Entry

    Into

    Servi

    ce

    Certi

    ficati

    on

    First

    Fligh

    t

    Major

    Bod

    y

    Secti

    ons

    Comp

    onen

    t De

    sign

    Gvt/Flutter/FEC

    LMS Flutter Analysis

  • 6 copyright LMS International - 2010

    Aero-elastic simulation and in-flight flutter testing

    FE Model Test Model (GVT) Aerodyn. Panel Model Physical prototype

    0)()()()( =++ xFtKxtxCtxM a&&&

    Traditional FEM, GVT-updated FEM, or direct GVT

    Aerodynamic panel method

    Due to presence of aero-dynamic term, modes of structural system are changing with airspeed and altitudeFlutter analysis = assessing evolution of modes (zero-crossing of damping value)

  • 7 copyright LMS International - 2010

    Flutter procedure: extract from NASA technical memo

    Fly at several stabilized speedsIncreasing dynamic pressureIncreasing MACH number

    Ref: NASA Technical Memorandum 4720, A Historical Overview of Flight Flutter Testing, October 1995

  • 8 copyright LMS International - 2010

    Flight flutter testing & in-flight modal analysis

    Background Testing Analysis

    s

    Rea

    l( m

    /s2)

    Dam

    ping

    Airspeed

    Flutter

    Ampl

    itude

    g2

    Telemetry link

    Hz-180.00

    180.00

  • 9 copyright LMS International - 2010

    Flutter testing procedure

    Find frequency and damping of critical modesFor increasing Speeds increases the dynamic loadAt different Altitudes the lower the altitude, the higher the dynamic loadAt different MACH values

    True Air Speed(knots)

    Altitude (feet)

    40,000

    30,000

    20,000

    10,000

    100 200 300 400 500

    MACH 0.95

    MACH 0.90

    MACH 0.85

  • 10 copyright LMS International - 2010

    Presentation outline

    Flutter testing: What, When and How?

    Validation

    Required technology

    Industrial implementation

    1

    5

    2

    3

    Conclusions

    4

  • 11 copyright LMS International - 2010

    Flutter testing requirements

    Get accurate damping estimate in an operational situationAccuracy

    Waiting Time is Money aircraft is airborne during the analysis

    Waiting Time is Dangerous during the analysis time, the aircraft may be exposed to near-flutter conditions!

    Speed

    Modal Analysis on operational (output-only) dataModal Analysis

  • 12 copyright LMS International - 2010

    EUREKA project FLITE2 Structural testing and modal analysis for aeronautics and space applications

    Airbus FranceDassault AviationLambert Aircraft EngineeringPZL Mielec

    LMS

    ILOTINRIAONERASOPEMEA

    University of Brussels (VUB)University of Krakau (AGH)University of Leuven (KUL)University of Manchester (UMAN)

    LMS Net Funding in FLITE2:378 kEUR

  • 13 copyright LMS International - 2010

    EUREKA project FLITE2 Structural testing and modal analysis for aeronautics and space applications

    Faster testing for GVTSmart combination of broadband / sweep / stepped

    Assessment of non-linear behavior using multi-sinesModal parameter estimation: iterative methods using noise information and yielding uncertainty bounds on estimates (PolyMAX results as starting values)Flight flutter testing: OMAX identification framework, i.e. combination of known and unknown excitation (EMA + OMA)Use of GVT for flutter safety prediction

    Aerodynamic panel model

    Hz

    dB( (

    m/s

    2)/N

    )

    0.00

    1.00

    Ampl

    itude

    /

    F FRF0F Variance0B COH0

  • 14 copyright LMS International - 2010

    Stable, robust and reliable modal analysison operational data

    Identification of modal parameters from response data (accelerations) measured in operating conditions

    EigenfrequenciesDamping ratiosMode shapes

    Operational modal analysis = identifying HBased on YWithout knowing U(BUT white noiseassumption) White noise

    HU Y

    White noise + harmonic

  • 15 copyright LMS International - 2010

    Output only: artificial vs. natural excitation

    Operational Modal Analysis: Output-only analysis no FRFs but Crosspowers between responses and reference responsesReference responses: wing tips, tail tips, nose; in general: well excited pointsOperational PolyMAXRequires natural, operational excitation!

    OMA with artificial excitationOnly operational responses are consideredbut: all modes are well-excited due to force input!and: additional operational excitation used

    0 . 0 0

    0 . 1 0

    Log

    ( g/N

    )

    H z- 1 8 0 . 0 0

    1 8 0 . 0 0

    Phas

    e

    PolyMAXPolyMAX

    NASA

  • 16 copyright LMS International - 2010

    Modal analysis LMS PolyMAX - theory & implementation

    Step 1:Denominator matrix

    polynomial (in z-domain)Poles and participation factors

    Step 2:Stabilisation diagram

    Step 3:LSFD to estimate mode

    shapes and upper/lower residues from selected poles

    [ ] [ ][ ] [ ] [ ] [ ] "")()()(0

    01

    11 zzzABHp

    pp

    p

    +++==K

    00

    11 zzz

    pp

    pp

    +++ K

    [ ]

    [ ][ ]

    [ ]0))(,( 1

    0

    =

    p

    HML

    [ ] { } { } URLRlvlvHn H

    iiTii +

    > increasing dynamic pressure

    Constant MACH

    0

    1000

    2000

    3000

    4000

    5000

    6000

    7000

    8000

    9000

    10000

    870 880 890 900 910 920 930 940

    Speed (km/h)

    Alti

    tude

    (m)

    MeasuredMACH 0.8

  • 29 copyright LMS International - 2010

    ONERA Flutter Simulatorsample time data (1)

    4 channels per flight point16 seconds per flight point32 seconds for near-flutter 4000 m set

  • 30 copyright LMS International - 2010

    ONERA Flutter Simulatorsample time data (2)

    Evolution vs. altitudeDecrease in damping clearly visible in response

  • 31 copyright LMS International - 2010

    ONERA Flutter Simulatorevolution of modes vs. flight conditions

    Flutter analysis

    0

    5

    10

    15

    20

    25

    30

    35

    40

    475.0 480.0 485.0 490.0 495.0 500.0 505.0 510.0

    CAS (knots)

    Freq

    uenc

    y (H

    z)

    Mode 1: 9.79HzMode 2: 10.05HzMode 3: 16.76HzMode 4: 19.03HzMode 5: 27.75HzMode 6: 34HzMode 7: 34.02Hz

    Flutter analysis

    0

    2

    4

    6

    8

    10

    12

    14

    475.0 480.0 485.0 490.0 495.0 500.0 505.0 510.0

    CAS (knots)

    Dam

    ping

    (%)

    Mode 1: 9.79HzMode 2: 10.05HzMode 3: 16.76HzMode 4: 19.03HzMode 5: 27.75HzMode 6: 34HzMode 7: 34.02Hz

    7 modes in modelModes 1 & 2