Part I: The Elements
Designing and operating an automated process so that it maintains specifications on, for instances, profitability, quality, safety, and environmental impact requires a close interaction between experts from different disciplines. These include, for example, computer-, process-, mechanical-, instrumentation- and control-engineering experts.
Each of these disciplines views the process and its control from a different perspective, so each has adopted different categories, or elements, in terms of which they think about the automated system. The computer engineer, for example, would think in terms of computer hardware, network infrastructure, operating system and application software. The mechanical engineer would emphasize the mechanical components from which the process is assembled; the instrumentation engineer would think in terms of actuators, sensors, and their electrical wiring.
The control engineer, in turn, thinks of the elements of a control system in terms of such abstract elements as signals, systems, and dynamic responses. These elements can be further specified by their physical realization, the associated model, or their properties. (See Table 1)
This book emphasizes the control engineer's perspective, one of process automation; however, the reader should bear the other perspectives in mind, because they form essential elements in a holistic view of the subject.
This first part of the book is the first stage of our journey into control engineering. It gives an introduction to the core elements of continuous-time signals and systems and describes the pivotal role of feedback in control-system design. These are the basic building blocks on which the remainder of the development rests.
Table 1. Systems and signals in a control loop