Application of self-tuning PI(PID) controller to a temperature control system

In this paper, an application of the self-tuning PI (STPI) controller, proposed by Cameron et. al (1983), to a microcomputer controlled water bath system is described. The water bath is an example of an important component in many industrial chemical processes. Experiments are conducted to test the STPI controller and to compare its performance with two other controllers, namely a self-tuning controller (STC) of Clarke and Gawthrop (1975, 1979) and a conventional PI controller. The reliability of the STPI controller is tested by artificially adding load disturbances, simulating a change in the process dynamics, and artificially adding a variable delay time element in the control loop of the process. The results prove that the performance of the STPI controller is as good as a self-tuning controller plus an added advantage of having a PI like structure. Moreover, the STPI controller performs better than the conventional PI controller especially when there are changes in the process dynamics