EXPLOITING ALIASING EFFECTS IN THE EIGENSYSTEM REALIZATION ALGORITHM

摘要

Timedomain identification techniques are not immune to the effects of aliasing. Any modes measured with frequencies over the Nyquist frequency appear as modes within the measurement bandwidth. Research has shown that aliased modes can be accurately identified using the Eigensystem Realization Algorithm (ERA). In this work, this fact is utilized to estimate frequency response function stiffness residuals are extract from an ERA generated state-space model. The residual is estimated using modes that have previously been considered due solely to noise. Aliasing is then explored and it is found that accurate, mass normalized modes can be determined for aliased modes. It is realized that identifying an aliased mode can be difficult and requires some a priori knowledge on the frequency bandwidth that the aliased frequency actually lies in. Numerical data is used to demonstrate the proposed techniques.