On-line identification and control methods for PID controllers

The aim of this paper is to present a method for on-line tuning of PID controller for stable processes. Without breaking closed-loop control, an explicit process model is developed from a single relay test and then controller gains are re-tuned non-iteratively to improve the performance. An explicit tuning rules are derived with special emphasis on minimizing the control efforts. Examples are given to illustrate the simplicity and superiority of the proposed method compared with some existing ones.