Singular entropy-based method to determine the system order in stochastic subspace identification

The operational modal parameter identification is now very active research topic in the system identification of civil engineering structures. As only output is measured, the modal parameter identification therefore bases structural output-only data. Stochastic Subspace Identification is a state-of-the-art technique to identify the structural modal parameters through field operational measurements. To determine the system order, however, is still an issue to be addressed in the data-driven Stochastic Subspace Identification. Based on the concept of the singular entropy, the singular entropy increment and its derivative are proposed in the paper to determine the system order incorporated with the Stochastic Subspace Identification. The corresponding theory and algorithm are described in detail. A simulated 4-strory frame structure and a simply beam tested in the laboratory are presented to illustrate the applicability and reliability of the proposed singular entropy based method to determine the system order. It is demonstrated that the proposed method is effective and applicable.