wilamowski-b-m-irwin-j-d-industrial-communication-systems-2011

13-10 Industrial Communication Systems
Layer Security (TLS) and is transparent to the application protocol, which therefore can remain mostly
unchanged; it only requires the initialization of a secure channel by negotiating crypto algorithms and
session keys. As soon as the secured connection is established, the application protocol can start.
13.6 trends in Vertical Integration
Vertical integration has come a long way since its first inception in the CIM era. This chapter tried to
shed light on some aspects, by far not all of them. An important recognition is that the recent technological
developments not only stimulated or revived the old idea, they accelerated and tightened the
integration. As a matter of fact, the large-scale introduction of Internet technologies caused the multilevel
automation pyramid to crumble down to at maximum three levels (Figure 13.7). The company level
is the strategic one; a further subdivision according to functional domains like in Figure 13.1 may be
useful; from a technological viewpoint, however, it is no longer necessary, not even in large globalized
enterprises. Internet has already provided the means to fully integrate remote branches in one single
corporate network with one common management or planning framework. From the many operational
levels, only two remain: the actual field level with the process control devices and an intermediate level
typically for controlling purposes.
From the networking point of view, there are in fact only two levels left today. In the office world and
the upper automation level, IP-based networks and Ethernet dominate. Even if fieldbus systems still
have their share on the cell level, they are bound to vanish within the next few years. It is the field level
that will still belong to them, maybe with some additional specialized and low-level local sensor/actuator
systems integrated via controllers acting as simple gateways. Nevertheless, the recent emergence of
real-time Ethernet extensions already sparked new competition in the field. In the long run, real-time
industrial Ethernet will offer a tempting alternative to the classical fieldbus systems and will most probably
make one or the other obsolete.
But, also from the application point of view, there is a trend toward a further reduction of the hierarchy.
In plant automation, which was traditionally strictly centralized in the upper two levels, modular
concepts are becoming popular. The overall goal is to enhance flexibility of planning systems and to
allow for solutions tailored to the needs of the customer. This makes ERP and, especially, manufacturing
execution tools attractive also for smaller companies that so far could not benefit from full-fledged
solutions. One step ahead are approaches to decentralize essential parts of the planning and control
functionality. Ideas like holonic manufacturing systems or agent-based automation practically dissolve
the rigid middle layer of the pyramid, implementing its functionality in software agents attached to the
outer levels of the hierarchy.
This tendency is supported by complementary trends in the control and enterprise field: In the long
run, control devices will resemble standard PCs in terms of computing resources and network interfaces
(Ethernet and IP). Thus, they will be able to run more complex planning tasks. On the other hand,
ERP
and SCM
(company level)
MES and SCADA
(cell level)
Control (PLCs, NCs)
(field level)
ERP
and SCM
(company level)
MES
MES
MES
and SCADA
(Cell MESlevel)
MES
MES
Control (PLCs, NCs)
(field level)
IP-based
networks
Field area
networks
Strategic
level
Operational
levels
FIGURE 13.7
Decentralization of the middle level in a typical industrial automation context.
© 2011 by Taylor and Francis Group, LLC