State-Space Model Identification for Component Synthesis

A scheme for synthesis of subsystem state-space models to be used for analysis of dynamic behavior of built-up linear structures is presented. Using measurements on each component, subsystem models are identified adopting contemporary system identification methods. The subsystem state-space models are transformed into a coupling form, at which kinematic constraints and equilibrium conditions for the interfaces are introduced. The procedure is applied to a plane frame structure, which is built up of two components. It is found that the non-trivial model order determination constitutes a crucial step in the system identification process. If the model order is incorrect at subsystem level, the synthesized model may radically fail to describe the properties of the built-up structure. Furthermore, we use subsystem models that satisfy certain physically motivated constraints, e.g. reciprocity and passivity. Different approaches and methods to aid the model order determination and the estimation of physically consistent state-space models at subsystem level are discussed.