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Parameter Identifiability in Finite Element Model Error Localization
Chalmers University. (Maskinteknik)ORCID iD: 0000-0002-4404-5708
Chalmers. (Strukturdynamik)
2003 (English)In: Mechanical systems and signal processing, ISSN 0888-3270, E-ISSN 1096-1216, Vol. 17, no 3, 579-588 p.Article in journal (Refereed) Published
Abstract [en]

A fundamental question in finite element model updating and error localisation is whether sufficient identifiability of model parameters is at hand for a given set of test data. Under certain conditions, the dynamic properties (to be compared with test data) of a structural model, may change similarly when a certain model parameter or a combination of other parameters are modified. Since low confidence in identified parameters can also be expected for marginally identifiable systems, due to the omnipresent noise when real test data are used, one should seek such states so as to avoid them. Should the problem lack identifiability, then before a meaningful error localisation can be made; either complementary test data have to be added or new parameters chosen for the model. The latter is studied in this paper. An index, the orthogonality/colinearity index, was developed to facilitate finding the best way to reduce the number of parameters when there is low identifiability The use of the index is demonstrated on a six-degree-of-freedom system in a numerical example. The example shows that error localisation or model updating using a parameterisation which has insufficient parameter identifiability is pointless.

Place, publisher, year, edition, pages
Elsevier, 2003. Vol. 17, no 3, 579-588 p.
Keyword [en]
Parameter Identifiability Finite Element Model Updating
National Category
Mechanical Engineering
Research subject
Technology (byts ev till Engineering), Mechanical Engineering
Identifiers
URN: urn:nbn:se:lnu:diva-34216DOI: 10.1006/mssp.2002.1522OAI: oai:DiVA.org:lnu-34216DiVA: diva2:717844
Available from: 2014-05-18 Created: 2014-05-18 Last updated: 2015-05-24Bibliographically approved
In thesis
1. Test Design for Finite Element Model Updating: Identifiable Parameters and Informative Test Data
Open this publication in new window or tab >>Test Design for Finite Element Model Updating: Identifiable Parameters and Informative Test Data
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

It is important to predict structural phenomena, such as noise and fatigue, stemming from vibra- tions. To do this, reliable structural dynamic models are needed. To be useful the models have to compare well with reality in the validation against test data; if not, the models should be mod- ified. The thesis research is in the field of computational model updating, which is, more often than not, the updating of uncertain parameters of a finite element model to better correlate to test data. This is a specialization that started to grow in the 1970s, and since then much research has been done. The work presented here concerns the design of tests for model updating, which is one of several model updating sub-tasks.

 For a test to be useful for model updating, the test data set must be such that the model param- eters are sufficiently well identifiable. The dynamic properties of a structure to be compared with test data may under certain conditions change similarly when one parameter or a set of other parameters is changed. When this happens, there is lack of identifiability and, before a meaningful model updating can take place, either complementary test data have to be added or a re-parameterization of the model must be made. An index was developed, the Orthogonality- Co-linearity Index (OCI), that helps to find the best way to reduce the number of parameters when there is low identifiability. For the model updating, test data also need to be informative with respect to the parameters to be tuned. The data informativeness depends on the test design, i.e. the choice of stimuli and the placement of the actuators and sensors. A data informativeness index that supports the design of an informative test is proposed. Procedures were also worked out to make the test design robust with respect to parameter uncertainties. The study is limited to linear and time-invariant systems.

Place, publisher, year, edition, pages
Göteborg: Chalmers tekniska högskola, 2003. 33 p.
Series
Doktorsavhandlingar vid Chalmers tekniska högskola, ISSN 0346-718X
Keyword
Test Design Finite Element Model Updating Informativeness Identifiability optimization Fisher information modal tests
National Category
Applied Mechanics
Research subject
Technology (byts ev till Engineering), Mechanical Engineering
Identifiers
urn:nbn:se:lnu:diva-34602 (URN)91-7291-393-2 (ISBN)
Public defence
2004-02-13, Chalmers, Göteborg, 15:20 (English)
Supervisors
Note

Avhandlingen var framlagd vid Chalmers tekniska högskola

Available from: 2014-06-09 Created: 2014-06-03 Last updated: 2015-05-24Bibliographically approved

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