Output intersampling approach to direct closed-loop identification

A direct closed-loop identification scheme that used the output intersampling technique was proposed. In this method, the plant output was sampled at a higher rate than the control input. It was also suggested that only one inter-sampling of the plant output could remove the restrictive identifiability condition required in the ordinary closed-loop identification methods. Under the scheme the closed-loop was identifiable under a low-order controller, designed for a reduced-order nominal plant, without introducing external test signals.