PI Controller using Ziegler Nichols Tuning

The results of the of the experiments carried out for the self tuning PI controller using Ziegler Nichols tuning method are shown. The upper plot shows the variations of the set point temperature (the black line) and the actual temperature (the green line) in the SBHS. The lower plot shows the control effort.

Figure 9.18: Result for self tuning controller designed using Ziegler Nichols Tuning for set point going from 32$^0$C to 37$^0$C

Although there are oscillations, the temperature remains near the set point. The result for a higher value of set point change is also shown.

Figure 9.19: Result for self tuning controller designed using Ziegler Nichols Tuning for set point going from 35$^0$C to 45$^0$C

For this experiment, the controller is able to make the temperature follow the set point closely. The fluctuations may be due to noises and the surrounding conditions.The plot for result of an experiment with another value of set point change is also shown.

Figure 9.20: Result for self tuning controller designed using Ziegler Nichols Tuning for set point going from 40$^0$C to 45$^0$C

In this experiment too, the controller is able to keep the temperature close to the set point and it stabilises fast.
For comparison, results of experiments done with conventional PI controller designed using the Ziegler Nichols method are also shown.

Figure 9.21: Result for conventional controller designed using Ziegler Nichols Tuning for set point going from 32$^0$C to 37$^0$C

Figure 9.22: Result for conventional controller designed using Ziegler Nichols Tuning for set point going from 35$^0$C to 45$^0$C

Figure 9.23: Result for conventional controller designed using Ziegler Nichols Tuning for set point going from 40$^0$C to 45$^0$C

For set point change from 40$^0$C to 45$^0$C, the self tuning controller showed small oscillations, but the conventional controller shows bigger oscillations.