ABSTRACT
So far we have been concerned with looking at the plant itself to ascertain the conditions that prevail there, which in turn influence the control that can be effected. We have seen the part played by lags and how these can affect the system. In this chapter we shall devote our attention to the effect that a controller has on the process. We shall examine in stages the basis upon which an industrial controller performs its task. Our gradual development of the ideas will refocus on those concepts that were propounded in the Introduction to this book. We will study the scientific reasons for the techniques used. Furthermore, the concept of the individual control terms used in a three-term controller will be explained, and we shall develop the mathematics for each of the terms involved.
