A self-tuning PID controller and its application for an ethylene cracking furnace

PID control schemes based on classical control theory have been widely used for real control systems up to now, since we can consider the control parameters as PID gains of proportional, integral and differential actions. Furthermore, there are many researches have been carried out regarding the tuning method of PID gains, since the control performance depends on these gains. Also several self-tuning and auto-tuning techniques in the PID control systems have been reported for systems with unknown parameters. However, there is so far no result on discrete-time systems with unknown time-delays. On the other hand, the pole-assignment control scheme has been reported as a useful self-tuning control technique for unknown time-delay systems. In this paper, we present a self-tuning PID control algorithm for unknown time-delay systems, based on the relationship between PID and pole-assignment control schemes