Closed-loop identification via time and frequency domain approaches

The direct closed-loop identification problem is considered in the paper. In the closed-loop, the unknown plant is managed by a digital feedback controller, so the ordinary identifiability conditions depend on the external test signal or the controller structure. We will develop both the time and frequency domain approaches by applying the output inter-sampling scheme and illustrate that the ordinary identifiability conditions. The effectiveness of the proposed approaches is demonstrated through some numerical examples.