Josefin Berner

Improved relay autotuning using normalized time delay

The relay autotuner provides a simple way of finding PID controllers of sufficient performance. By using an asymmetric relay function the excitation of the process is improved. This gives better models, and hence a better tuning, without increasing the time consumption or complexity of the experiment. Some processes demand more accurate modeling and tuning to obtain controllers of sufficient performance. These processes can be singled out by their normalized time delays and be subject to further modeling efforts. The autotuner proposed in this paper provides a simple way of finding the normalized time delay from the experiment, and uses it for model and controller selection. The autotuner has been implemented and evaluated both in a simulation environment and by industrial experiments.

Implementation of an asymmetric relay autotuner in a sequential control language

Control applications contain both logic, sequencing, and control algorithms. A holistic view of this is seldom presented in teaching and papers. One reason is the separation of communities - automation groups typically come from the Programmable Logic Controller (PLC) world while control engineers primarily come from the Distributed Control System (DCS) world. Both logic, sequencing, and control algorithms are, however, well integrated in todays control systems since DCS systems now contain logic and sequencing and PLCs now contain control algorithms. This paper shows that both logic, sequencing, and control algorithms can be integrated seamlessly in a sequential control language. The particular application considered is a PID controller with a relay autotuner. The presented autotuner implementation yields good controller parameters and is freely available.

Practical evaluation of a novel multivariable relay autotuner with short and efficient excitation

In this paper we propose an autotuning method that combines a setup for decentralized relay autotuning of two-input two-output systems with an identification method that uses short experiments to estimate up to second-order time-delayed systems. A small modification of the experiment gives better low-frequency excitation and improved models. The method is successfully demonstrated in simulations and on a quadruple tank process.