Conductivity based PID tuning for long time delay process using simulation technique

Abstract

In the Ziegler-Nichols method of PID controller tuning the ultimate gain and the ultimate period were determined by closed loop test. In practice it is very difficult to conduct a closed loop test in process industries. Moreover the ultimate gain and period cannot be easily determined by closed loop test if the process has a long time delay, on-off control or if an integrating element present in the process. To overcome this difficulty, the ultimate gain and period were determined by simulation of the process model obtained from open loop test. The PID tuning parameters were then calculated by making use of Ziegler-Nichols relation.