Discussion on: 'Closed-Loop Identification of MIMO Systems: A New Look at Identifiability and Experiment Design'

摘要

The paper by Bazanella, et al. answers the question about whether it is necessary to excite all external references in order to identify a MIMO system operating in closed-loop. Closed-loop identification has generated much research interest in the past, a few decades ago, and many results exist on system identifiability. One main result [1] states that for a closed-loop MIMO system to be strongly system identifiable, all reference inputs have to be persistently excited. Since the strong system identifiability implies that the model parameter estimates must converge to the true system for all model structures that can represent the true system, this statement, which is technically true in itself, may lead to the false impression that it is necessary to excite all reference inputs if one wants to identify a system under closed-loop conditions.