Relay Feedback Identification with Additional Integrator

This paper presents a relay feedback technique for identification of dynamical systems for control purposes. The proposed technique uses a biased relay test with an added integration to determine three frequency response points for a phase lag in the range from 0 to 180 from a single experiment. This approach is based on a recently published method called "shifting method". The additional integrator helps to improve the position of the frequency points obtained by the shifting method. The three frequency response points can be used for fitting up to five parameters of a process transfer function with various structures. The paper provides explicit formulas for determining the parameters of the second order model with a time delay from the obtained frequency response points. This approach can be used for the purpose of the controller design. The method is demonstrated on lag dominated, balanced and delay dominated processes. Matlab/Simulink programming environment was used for all experiments. (C) 2019, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.