Experimental study of PID auto-tuning for unsymmetrical processes

The advent of relay auto-tuning of PID controllers got rid of previous troublesome tuning procedure. However, PID control performance didn´t change so much since the tuning rule was the same as the Ziegler and Nichols that only use ultimate gain and ultimate period. In this paper, we propose new tuning rule especially for an unsymmetrical process. The experimental test result showed proposed rule achieved less overshoot and quicker disturbance recovery than conventional tuning rule.