Although there has been several reports of various different schemes of self-tuning PI (STPI) and PID (STPID) controller in recent years, the application of this type of controller is still limited. The capabilities of this type of controllers to control real physical processes need to be proven in more detail. In this paper, an application of a STPI controller proposed by Cameron etal (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 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 selfhning controller plus an added advantage of having a P1 like structure. Moreover, the STPI coiltroller performs better than the conventional PI controller especially when there are changes in the process dynamics.Keywords: self-tuning PI(P1D) controller, temperature control process, parameter estimation, and tuning parameters.
IntroductionThe domination of PI and PID controllers in the process control industries is the main driving force towards the escalation in the theories and practice of STPI and STPID controllers. Although self-tuning controller is more flexible and provide a more systematic way of dealing with uncertainties, non-linearities and time varying plant parameters, its applications in the process control industries is still not very encouraging. Self-tuning controllers can be viewed as performance oriented in that, the closed loop performance are specified by the user and the algorithm sets out to attain this performance eventhough the plant parameters or the drifts are unknown. Indeed, this implies that the desired performance of the plant can only be achieved given the saturation characteristics of the control actuator and the skill of the plant engineers is crucially impoirant. A progressive step is
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