Use of Fast-Time Process Analogs in Two-Position Control

It has been shown [1] that use of a ``fast feedback'' loop incorporating a plant model and a two-position controller results in better control of first-order thermal plants with inherent time delay. In this paper such a control scheme is analyzed with a view of adapting it for process control. Both steady-and unsteady-state analyses are carried out for the case where disturbance variations occur during regulatory control. Based on the results obtained, criteria are evolved for the selection of suitable model parameters which result in zero offset in plant output, minimum period of steady-state cycling, and acceptable transient behavior.