A relay based on-line tuning method for PID controllers is presented. Due to a new structure to use the relay for identification reasons the method is well appropriate for a large class of linear and non-linear processes which may have load and noise disturbances. The new structure inserts a relay in parallel to a conventional P, PI or PID controller inducing limit cycle oscillations of small amplitude around the process value. With the limit cycle measurements, a transfer function model of the process dynamics is obtained by a robust identification method. Using a model based tuning algorithm the controller settings are retuned to achieve enhanced performance without disrupting the closed-loop control. The performance of the proposed scheme is discussed by different simulations to show the benefits of the new method.
Print ISSN: 0178-2312
Volume: 52, 05/2004
Pages: 202 - 208