PID auto-tuning by a composed structure

It is proposed in this paper to reduce the excessive overshoot produced by the tuning of Ziegler-Nichols method and to obtain better rise times that tuning Angstrom strom method by using a structure called composed structure and by weighting the three actions of the PID controller by three factors. These last factors F-p, F-i, F-d are determined in function of the system parameters so as to guarantee a specified overshoot in closed-loop. The usual parameters (K, T-i, T-d) of the PID are fixed by the tuning of Ziegler-Nichols (Z-N) method, which provides a good rejection of the load disturbance. The auto-tuning of this method can be easily obtained by using relay method [1], [9],[11] for the determination of Ziegler-Nichols frequency model parameters.