PID controllers of two degrees of freedom structure were implemented by Teng and Sirisena (1988). However, they may not be suitable in practice because their structure may not be understood easily by process engineers in industry. In this paper the enlarged least-square estimator in Teng and Sirisena (1988) is combined with the popular discretised classical PID controller. A Smith predictor is added to the controller for the control of dead-time process. The enlarged least-square estimator cope well with time-varying dead time owing to its adaptive nature. Simulation and experimental results verify that the new controller performs satisfactorily.
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