Identification of Time Domain Structural Responses under Operating Condition. 2nd Report. Case of a System with Unsteady State.

Abstract

This paper is concerned with the estimation of the ODSs (Operating Deflection Shapes) of a system with unsteady state. It is usually difficult to identify the ODSs, because the responses under operating condition are not always in steady state. Therefore, the adaptive identification scheme of the ODSs for non-stationary signal has several needs. This paper present a new type of subspace method which can identify well-excited frequencies and the ODSs corresponding to those frequencies. In order to prove the adaptability of this scheme for time-varying signals, we demonstrate its performance on artificially generated responses. Then we use the responses of an actual structure and show the effectiveness of this scheme with real data. These results are in good agreement with analytical ones and lead us to believe that the proposed scheme can be successfully used for the identification of time-varying signals.