Estimation of order and delay time of the process in a closed-loop control system

This paper proposes a procedure for estimating the order and delay time of the process in a closed-loop control system from its input and output data. There are identifiability conditions that assure uniqueness and unbiasedness of the estimates, but they assume that the order and delay time of the process are known. Therefore, it is of primary importance to estimate the order and delay time of the process in the identification of a closed-loop system. In this paper, the authors first investigate the influence of the closed loop on identification, then propose a procedure for estimating the order and delay time, taking into account their consequences.