Estimation of a SOPTD transfer function model using a single asymmetrical relay feedback test

Abstract

Using a single asymmetric relay feedback test, a method is proposed to identify four parameters of a transfer function model. The proposed method is used to identify all the parameters in a second order plus time delay model (SOPTD). The parameters estimated are of adequate accuracy for designing suitable controllers. The estimated SOPTD models have a step response behavior matching that of the actual process. The method can also be used for identifying open loop unstable transfer function models. For unstable systems, the closed loop step responses are compared. Simulation results are given for four case studies.