Direct closed-loop identification approach to unstable plant

Deals with the problem of direct closed-loop identification for unstable plant models disturbed by stochastic noise. The unstable plant is stabilized by a digital feedback controller. Then by introducing the output inter-sampling scheme, the plant model is identified from the inter-sampled input-output data of the plant even though the external reference or the test signal does not hold a persistently exciting property. Both time and frequency domain approaches are developed and numerical examples are performed to demonstrate the effectiveness of the proposed approaches