Process identifier and its application to industrial control

Many industrial controllers use the relay experiment to estimate the system ultimate data for three-term controller tuning. However, for some systems the relay experiment describing function analysis can produce poor estimates. The paper reports a new and more accurate method of finding system frequency response data including the system ultimate data. A full demonstration of the accuracy attainable by the new method is presented. The new method was motivated by a phase-locked loop concept. The additional flexibility to find gain and phase margins, or the peak resonance frequency is demonstrated. The paper includes the application of the module to closed-loop system identification and a brief discussion of the LabVIEW implementation