PI tuning for large dead-time processes with a new robustness specification

A simple PI controller tuning method for large dead-time processes is presented. First, a first-order plus deadtime model is identified on the basis of relay feedback experiments, which Nyquist curve is very close to that of large dead-time processes over a wide frequency range. With the model available, PI controller is designed with a new robust specification. Simulation examples show the effectiveness and feasibility of the presented PI tuning method for large dead-time processes.