Application of updating methods on the finite element model of PICARD. Fabrice BUFFE CNES ECSSMMT 2009

Transcription

1 Application of updating methods on the finite element model of PICARD Fabrice BUFFE CNES ECSSMMT 2009

2 Summary 1. Presentation of tests and updating goals 2. Method used for updating 3. Optimization of the location of sensors 4. Analysis of tests results 5. Finite element model updating 6. Conclusion 2

3 1. Presentation of tests and updating goals Qualification test of the Payload QM for the PL (SODISM, SOVAP, PREMOS, PGCU) Plateform STM Environnements Resonnance frequency research Random qualification Shocks Updating performed from the RFR 3

4 1. Presentation of tests and updating goals Instrumentation 91 sensors + 12 pilot sensors 4 on the lateral panels of the PF 15 on the panel +X 5 on the solar array The rest on the PL 4

5 1. Presentation of tests and updating goals Updating goals : Prediction for FM tests Zones which need to be updated : IF between PF and PL PL models have been updated thanks to subsystem tests The PF STM model has been updated from Demeter 5

6 1. Presentation of tests and updating goals Critical dimensionning aspect : fasteners between the PF and the baseplate Modes around 70 Hz Expected secondary notching Sodism Fixed point Baseplate Panel +X Pod 6

7 2. Method used for updating Optimization of the location of sensors Better distinguishability between modes Link with the visibility of the model? Tests results analysis and modal identification Use of Primodal Error localization Criteria based on the Constitutive Equation Error (CEE) Use of AESOP FRF approach or modal approach Model updating Criteria based on the Constitutive Equation Error (CEE) Use of AESOP FRF approach or modal approach Frequencies updating based on sensitivity methods 7

8 2. Method used for updating Optimization of the location of sensors Based on the finite element model only Based on a modal analysis possibility to impose sensors, or to limit the candidate dof n considered modes p measured dof Modal analysis Modal shapes X n * p p Optimal measured dof Conditionning of X n * p minimized Tend to orthogonalize the modal shapes matrix Improvement of the MAC Better distinguishability between modes Link with the visibility of the model? 8

9 2. Method used for updating Preparation of tests results with PRIMODAL Detection of faulty sensors Correction of the direction of sensors Normalization with pilot sensors Modal identification from sine sweep base excitation vibration tests RTMVI (Real Time Modal Vibration Identification) RFP (Rational Fraction Polynomial) SVD (Singular Values Decomposition) Visualisation of modes on «sensors» dof Better comprehension of modes 9

10 2. Method used for updating Error localization (LMT Cachan) Simplified formulation : U K et et exp λ exp M resp. experimental eigenvectors and eigenvalues resp. the stiffness matric and the mass matrix KV KV = λexp If accelerations are measured on all dof of the model : M U Avec U=U exp If acceleration are measured only on some dof, V is define by : t t = λexpm U With U min ( U V ) K( U V ) + ( ΠU U ) K ( ΠU U ) U, V [ ] exp red exp The localization criteria is defined by : e elm = t ( U V ) K ( U V ) elm elm elm elm Erroneous zones are observed where e is important elm 10

11 2. Method used for updating Model updating From the Constitutive Equation Error : Choice of parameters p corresponding to localized zones No need to pair analytical and experimental modes e = t t ( U V ) K( U V ) + ( ΠU U ) K ( ΠU ) exp red U exp Updated model min p ( e) From a sensitivity analysis : Choice of parameters p corresponding to localized zones We kkep those which are most sensitive to eigenfrequency Need to pair analytical abd experimental modes min p [( f f exp) + ( V V exp) ] 11

12 3. Optimization of the location of sensors Constraints imposed on PICARD PL sensors imposed Lateral PF sensors imposed No optimization on the Solar array, because the model is not representative of the ballast Optimization only on the panel +X Constraints on sensors on the panel +X Triaxes Verification of level at the base of each equipment 12

13 3. Optimization of the location of sensors Optimized configuration of sensors 13

14 4. Analysis of tests results Verification of tests data Detection of faulty sensors Verification of the direction of sensors (Low frequency level) Verification of the sign of sensors (Low frequency phase) Preparation of test data Normalization by the mean of pilot sensors First comparison between analytical and experimental FRF 14

15 4. Analysis of tests results Modal identification RTMVI Each mode is identified on one axis 8 modes identified 15

16 4. Analysis of tests results MAC Matrix 3 Rigid body modes 16

17 5. Finite element model updating Errors localization Pod property From modal parameters For each model property Permit to chose easily parameters for updating 17 Mode n 3

18 5. Finite element model updating Updating 1 Adding of rigid elements near fasteners 18

19 5. Finite element model updating MAC Improvement 19

20 5. Finite element model updating Errors localization Solar array 20

21 Updating 2 5. Finite element model updating FEM of the solar array is not representative of the real structure Sensors on the solar array not taken into account Coupled modes Solar array + PL Need to update these modes 21

22 5. Finite element model updating Updating 2 Monte Carlo with 3 variables Variation of CEE Correlation between the CEE and the variable 3 (Thickness of the solar array) Thickness increases CEE decreases Thikness 4.5 mm 5 mm 22

23 5. Finite element model updating MAC improvement 23

24 5. Finite element model updating Error localization 3 Solar array Impossible to update the solar array : The model is not representative enough of the solar array 24

25 5. Finite element model updating Error localization 3 Pod Normalization by the volume of the property 25

26 5. Finite element model updating Updating 3 energie totale 1,85 Variation of the section of the pods Visualization of the CEE Global minimum observed 1,8 1,75 1,7 1,65 1,6 1,55 1,5 1,45 1,4 0,00E+00 1,00E- 03 2,00E- 03 3,00E- 03 4,00E- 03 5,00E- 03 6,00E- 03 7,00E- 03 Section barres Initial value Radius = 3 mm Optimal value Radius = 3.25 mm 26

27 5. Finite element model updating Updating 3 CEE decreases Eigenfrequencies become closer f 3 : 72.8 Hz 75.5 Hz F 4exp = 75 Hz f 4 : 82.5 Hz 83.5 Hz F 4exp = 86.5 Hz Initial value Optimal value 27

28 5. Finite element model updating Impact on FRF Comparison between FRF after updating 1 (rouge) FRF after updating 3 (bleu) FRF tests (noir) 28

29 6. Conclusion CEE method efficient if : Errors are clearly localized Sensors configuration permits to have a good visibility of the model If the visibility is not good enough, the sensitivity method has to be prefered Remarks on errors in the model : Stiffness of the interface, because contact not modelized Difficulties to define modelization rules 29

30 Thank you for your attention Questions? 30