Relay Feedback Identification Method for PID Controller Tuning

The shifting method of relay feedback identification is a system identification method based on the frequency behaviour of the system. It allows to identify stable or unstable, oscillatory or non-oscillatory systems describable by a second order time delayed model, if these have stable behaviour in the relay feedback test. This paper demonstrates the use of the shifting method to find models of simulated and real systems, including estimation of static gain, also under static disturbances. Identified models could be used for tuning of PID controllers. The models found are compared with prime identified systems according to frequency responses and step responses. The results of the shifting method are compared with the results of other identification methods to verify the practical benefits of use of this method. All tests were done in the programming environments Matlab/Simulink.