Stability limits of a Smith controller in simple systems containing a time delay

Abstract

The stability of time delay systems incorporating a Smith controller is discussed. It is shown that a system, which gives optimum response for perfect matching of the plant model and plant, may become unstable if a mismatch occurs. The stability boundaries are given for variations in gain, time constant and time delay of models and plant having the general form The regions of stability are of sufficient size to justify the use of Smith controllers in practical systems and further it is shown that optimum response in the ITAE sense is obtained with the model delay greater than that of the plant.