Development of new approaches for tuning process controllers

Abstract

In this thesis, relay-based approaches towards controller design are developed. Firstly, a new relay feedback technique is proposed here, which yields significantly improved accuracy over the conventional relay feedback in determining the ultimate frequency and ultimate gain. The proposed technique improves the accuracy by boosting the fundamental frequency in the forced oscillations, using a preload relay. Next, a new method is proposed for closed-loop automatic tuning of PID controller based on a new RC approach. The proposed approach is applicable to process control applications where there is usually a time-delay/lag phenomenon, and where non-repetitive step changes in the reference signal are far more common than repetitive ones.Lastly, a new method is proposed for automatic tuning of the Smith predictor controller based on another new RC approach. The proposed approach is applicable to process control applications with a long time-delay where conventional PI controller will typically yield a poor performance.