A New Look at PID-Controller Tuning

The well-known Ziegler-Nichols method for tuning controllers has been used for 50 years. Since it is still popular, the time is ripe for a reappraisal. It is shown that the Ziegler-Nichols settings for PID-controllers have been misapplied by being used indiscriminately with different PID-controller configurations. Computer simulation made on 15 representative processes indicates how these settings should be modified to obtain good response for load step changes. The results are presented in three different forms, for different controller configurations.