Model identification and PID control of long time-delay processes

A relay feedback identification auto-tuning of PID/PI controller is proposed in this paper, which is capable of controlling long time-delay processes. The real process is approximated via FOPDT or SOPDT models, whose parameters are specified through a modified relay feedback identification method. Applying the zero-pole cancellation principle, the PID/PI controller is tuned according to the specified amplitude and phase margins. Model identification and controller parameter tuning are done online without much influence on the normal operation. This algorithm also has many other advantages such as a fast setpoint response, strong robustness and good disturbance rejection ability.