Subspace identification algorithms currently emerge as an efficient tool. In this paper, we investigate their use for the output-only identification of the eigenstructure of a linear MIMO system. We focus on the following situation: several successive data sets are recorded, with sensors at different locations in the structure; for doing this, some of the sensors, called the reference sensors, are kept fixed, while the other ones are moved for the different records. The interest of this setup is to emulate a situation in which hundreds of sensors are available, while in fact only, say, ten are actually at hand. This situation is typical in structural analysis in vibration mechanics, a case which motivated our study. One additional difficulty here is that the input, besides being not observed, is turbulent in nature and nonstationary. The purpose of this paper is to show how subspace methods can be adapted to such a situation.
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