Control-System Behavior Expressed as a Deviation Ratio

In order to bridge the gap between process-control practice and modern control theory, an attempt is made to reduce this theory to its bare essentials. A simple picture is drawn of what control does and how it does it, use being made of the familiar concepts of resonance and damping. Thus a theoretical background is provided for commonsense judgments on control quality and controller settings. The picture given is applicable to both feedback and feedforward control.