On subspace identification of cascade structured systems

Subspace identification has proven useful when identifying identifying multi-input multi-output systems. It is, however, important in many applications to take a priori structural information into account in the identification, something that is difficult when using subspace methods. Here will study how to incorporate a special structure, a cascade structure with two subsystems. Two new methods are derived for estimating system with this structure. The problem when using subspace identification on cascade structured system is that the states from the first subsystem is mixed with states from the second subsystem via a unknown similarity transform. Hence after the identification the subsystems cannot directly be recovered. The first indirect method finds a similarity transform that takes the system back to a form such that the subsystems can be recovered. In the first step, the subspace method forms a estimate of the extended observability matrix, from this the state space matrices can ...

• Type: Journal
• Year: 2010
• Where: CDC
• Authors: Per Hagg, Bo Wahlberg, Henrik Sandberg
• Keywords: CDC 2010, Control Systems, Extended Observability Matrix, State Space Matrices, Subsystems