Robust closed-loop controller auto-tuning

In this paper, a simple yet robust closed-loop identification method is proposed, and an auto-tuner is then constructed. Using the fast Fourier transform (FFT), the process frequency response is first calculated from the recorded process input and output time responses to the closed-loop test. The process step response is then constructed using the inverse FFT. A general second-order plus dead time model is thus obtained using our newly developed technique on robust identification of process transfer function from step responses. Simulation examples and real time test show its effectiveness.