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Introduction to Industrial Automation
automation equipment, there exist more than 20 industrial networks today, addressing all lev-
els of industrial production, which are examined in Chapter 8. Industrial networks differ quite
significantly from traditional enterprise networks due to their specific operational requirements.
More specifically, industrial networking concerns the implementation of communication proto-
cols between field equipment, digital controllers, various software suites, external systems, and
graphical user interfaces. In general, by allowing the connection of digital industrial controllers,
the industrial network offers mainly the possibility of sensing messages and control commands
through a decentralized approach, which can be geographically spanned. Thus, today the control-
ler of a specific production process could sample the information from another part of the factory
automation or control the operation of a machine in a remote part of the industrial field. Since
this concept can be fully generalized on the full automation floor, the ability to control the whole
industrial process and to have a complete overview of the ongoing sub-processes has been made
more achievable than ever before, and thus the concept of supervisory control and data acquisition
(SCADA) has been introduced. Furthermore, today’s industrial networks can interconnect indus-
trial controllers from different producers, converging in a similar way as the well-known “open
communications” demand.
The SCADA concept has been introduced from the real need to gather data and supervision-
like control subsystems on a large industrial process plant in real time. Regardless of its initial
definition, the term SCADA today represents a combined hardware and software system, includ-
ing the remote field devices, the network, the central station equipment and the software platform.
This software platform, in the case of SCADA, offers the user all the functionality required to
receive or send data, represent data graphically, manage alarm signals, perform statistic calcula-
tions, communicate with other databases or software applications, schedule control actions, print
various reports, and many other user facilities. Although the focus of SCADA systems is data
acquisition and presentation on a centralized human machine interface (HMI), it also allows for
high-level commands to be sent through the network to the control hardware, for example, for the
command to start a motor or change a set point in a remote place. A characteristic example of a
SCADA system is presented in Figure 1.15.
Similar to SCADA systems are distributed control systems (DCS), even if these systems existed
before the era of SCADA systems, especially in the cases of the oil and gas refiners’ industries. The
DCS system consists of a strong dedicated network and advanced process controllers, often with
very powerful processors, while implementing multiple, closed-loop controls of critical importance.
In general, it should be highlighted that there is some confusion about the differences between
these two types of automation systems, mainly due to the numerous common characteristics that
these systems possess. A basic difference is the fact that the DCS is process-oriented, as opposed to a
general-purpose software suite, and generally focused on presenting a steady stream of process infor-
mation. This means that although the two systems appear similar, their internal operations may be
quite different. SCADA systems, on the other hand, does not have the control of processes as a pri-
mary role, even if they have all the capabilities to apply limited closed-loop control and automation.
The main focus of the SCADA system is the monitoring and the supervision of a process, which has
been geographically distributed, most commonly through a multi-network communication struc-
ture. In contrast, the DCS is not concerned with determining the quality of data and visualization
approaches, as communication with the corresponding control hardware is much more reliable. Even
if the boundaries between these systems seem to be more blurred as time goes by, the computer and
network technologies have become an intimate part of control and automation system engineering.
Based on the technology of industrial networks and the powerful computational automation
units, the optimal implementation of the concept of computer integrated manufacturing (CIM)
