Parametric identification of linear systems operating under feedback control

This paper considers the indirect identification of closed-loop systems wit h colored noise when there exist low-order controllers in the loop. A new f orm of bias-eliminated least-squares (BELS) method is developed which is ba sed on a simple and efficient technique of estimating the colored-noise-ind uced bias through a combined use of the known information about the control ler and a proper number of zero parameters introduced. The main feature of the presented EELS based method is that no prefiltering of sampled data is needed and an unbiased estimate For the closed-loop parameters is given in a direct manner, The presented method is verified via application to indire ct identification of an open-loop unstable plant.