IDENTIFICATION OF MODAL PARAMETERS FROM MEASURED OUTPUT DATA USING VECTOR BACKWARD AUTOREGRESSIVE MODEL
✍ Scribed by C.F. HUNG; W.J. KO
- Publisher
- Elsevier Science
- Year
- 2002
- Tongue
- English
- Weight
- 368 KB
- Volume
- 256
- Category
- Article
- ISSN
- 0022-460X
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✦ Synopsis
In this paper, a modal identi"cation system that is based on the vector backward autoregressive (VBAR) model has been developed for the identi"cation of natural frequencies, damping ratios and mode shapes of structures from measured output data. The modal identi"cation using forward autoregressive approach has some problems in discriminating the structure modes from spurious modes. On the contrary, the VBAR approach provides a determinate boundary for the separation of system modes from spurious modes, and an eigenvalue "lter for the selection of physical modes is existent in the proposed method. For convenience of application, the backward state equation established from VBAR model is transformed into a forward state equation, which is termed as transformed VFAR model in this paper. In addition, the extraction of equivalent system matrix of state equation of motion for structures from the transformed VFAR model has been developed, and then the normal modes can be calculated from the identi"ed equivalent system matrix. Two examples of modal identi"cation are carried out to demonstrate the availability and e!ectiveness of the proposed backward approach: (1) Numerical modal identi"cation for a three-degree-of-freedom dynamic system with noise level in 20% of r.m.s of measured output data; (2) experimental modal identi"cation of a cantilever beam. Finally, to show the advantage of the proposed VBAR approach on the selection of physical modes, the modal identi"cation by stochastic subspace method was performed. The results from both methods are compared.