A real-time approach for dead-time plant transfer function modeling based on relay autotuning

In this article, a modified relay feedback experiment for the generation of sustained oscillations in a class of dead-time plants and their mathematical modeling is presented in a real-time fashion. For the ease of calculation, an equivalent gain of the relay is considered using well-known describing function method and further utilized in the derivation of a set of simple analytical expressions for the estimation of plant model parameters. Simulation studies are considered to show the validation of the proposed models with the model obtained from Matlab System Identification Toolbox (SIT) and literature through integral absolute error index. Yokogawa distributed control system is considered as an experimental platform to conduct the relay autotuning test for the identification of a real-time liquid level control system in-terms of dead-time transfer function models. Finally, the accuracy of proposed models is demonstrated through frequency response plots as well as relay response plots in comparison with models obtained from Ziegler–Nichols tests and Matlab SIT.