Tuning of fractional PID controllers with Ziegler-Nichols-type rules

In this paper two sets of tuning rules for fractional PIDs are presented. These rules are quadratic and require the same plant time-response data used by the first Ziegler-Nichols tuning rule for (usual, integer) PIDs. Hence no model for the plant to control is needed-only an S-shaped step response is. Even if a model is known rules quickly provide a starting point for fine tuning. Results compare well with those obtained with rule-tuned integer PIDs. (c) 2006 Elsevier B.V. All rights reserved.