Output intersampling approach to direct closed-loop identification

A new direct closed-loop identification method, which uses the output intersampling technique, is proposed in this note. By using the intersampled plant input--output data, the proposed method removes the traditional restrictive identifiability condition, and does not require an external persistently exciting (PE) test signal. Index Terms--Closed-loop identification, identifiability, inter-sampling, persistently exciting (PE).