Robust estimation of process frequency response from relay feedback

A method for the robust process frequency response estimation in the presen ce of noise and disturbance is proposed. The effect of noise on the identif ication results is suppressed with the application of the familiar averagin g technique to the input-output samples collected from the limit cycles exh ibited in relay feedback tests, while the effect of linear disturbances is removed by conducting multiple relay tests. Simulations are performed to ve rify the capability of the method through the identification of a simple fi rst order plus dead time process. (C) 1999 Elsevier Science Ltd. All rights reserved.