Constrained antiresonance frequencies-based model updating method for better matching of FRFs

Abstract

Most of the finite element model updating methods use resonance frequencies and modeshapes for updating mass and stiffness matrices. These model updating methods are not very accurate as modeshapes cannot be estimated accurately. Whereas, antiresonance frequencies can be estimated accurately from measured frequency response functions (FRFs). In this paper, a new antiresonance-based model updating method is proposed for better matching of FRF by imposing constraint on error in predicted FRF. In the proposed method, mass and stiffness matrices are updated in the light of antiresonance frequencies along with resonance frequencies. Equal weight factors are applied so that there is an equal contribution of resonance and antiresonance frequencies in the updated model. The effectiveness of the proposed finite element updating method is demonstrated by two experimental examples. Firstly, case study of simple fixed–fixed beam structure is presented which is followed by a case study of F-shaped structure, which resembles the skeleton of drilling machine. The proposed method is compared with a standard direct model updating method. The updated results have shown that antiresonance-based model updating method can be used to derive accurate model of the system. This is illustrated by matching of the FRFs obtained from the updated model with that of experimental FRF.