2. Introduction to the Principles of Feedback
On simulating the performance of the above control loop for K=1 (see Figure 2.5), we find that the smaller controller gain (K=1) results in a slower response to a change in the mould-level set-point. On the other hand, the larger controller gain (K=5) results in a faster response but also increases the effects of measurement noise as seen by the less steady level control and by the significantly more aggressive valve movements.
Thus, the performance requirements derived in subsection § 2.3.1 appear to be in conflict with each other, at least to some degree.
At this point, a control engineer who does not have a systematic background in control-system design would have a difficult time in assessing whether this conflict is merely a consequence of having such a simple controller or whether it is fundamental. How much effort should be spent in finding a good value for K? Should one choose a more complex controller? Should one spend more effort in modeling the mould-level process?
The remainder of the book is devoted to developing systematic answers to these and other related questions.