Model identification and PID control of long time-delay processes

A relay feedback identification autotuning PID/PI 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 zero-pole cancellation principle, the PID/PI is tuned according to the specified amplitude and phase margins. Model identification and controller parameter tuning are done on-line without much influence on the normal operation. This algorithm also has many other advantages such as fast setpoint response, strong robustness and good disturbance rejection ability.