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

Vertical Integration 13-7
Management
level
Field
level
CEA-852 and BACnet/IP
BACnet
router
BACnet
A
B
CEA-852
router
LonWorks
Network 1 Network 2
C
LonWorks +
BACnet
Multiprotocol
device
IP backbone
Operator
workstation
FIGURE 13.4
Protocol convergence using multi-protocol gateways.
technology (multi-protocol device). This way, the fieldbus node A can directly retrieve process data from
the controller. Nodes B and C, which do not need access to the respective other network technology, can
still be accessed by the operator workstation’s native protocol. No additional gateway is needed as the
area of overlap does contain the needed technologies. A given number of those multi-protocol devices
can be seen as a distributed gateway. This means the SPOF has been eliminated. Also, the complexity of
gateway configuration is reduced as the nodes know already about their data points natively. Clearly, not
all nodes can be equipped with an arbitrary number of networking technologies.
13.4 application View
An important aspect of vertical integration is the interconnection of the software application frameworks
that are needed for the individual levels of the automation hierarchy. From today’s view, the link
between the top-level strategic planning and administration tools usually comprised in ERP systems
and the distributed control systems on the factory floor is to be seen in the MES concepts that translate
the overall, mainly long- and mid-term plans into short-term work and production orders. To achieve
this integration, there is still work to be done [V02]. In the context of enterprise engineering, the current
focus is on efficient modeling languages and techniques, on analysis methods, and advanced computerbased
tools [MPZM03].
An eminent role is played by standardization. The more CIM and its successors found the approval of
industry, the more it became apparent that only concerted actions could finally produce results with a high
application potential. Standards generally provide the basis for durable solutions and finally products,
which is particularly important in such complex areas as the integration of rather diverse functions inside
an enterprise. After all, the problems of enterprise integration in actual practice are not so much the functional
modules as such (the ERP, MES, SCADA systems in all their varieties) but the interfaces between
them. Only standardized interfaces together with appropriate functional models for the application processes
and their data objects ultimately allow for interoperability between solutions from different vendors.
Consequently, work being done in various standardization groups covers all aspects ranging from
the provision of modeling frameworks and languages through concrete reference and data models
for enterprise systems or subsystems down to standards for IT services and infrastructures [CV04].
Among the many standards developed in this context, the two most relevant for this chapter are the
Manufacturing Execution Systems Association (MESA) model and, in particular, the ISA S95 Standard
for Enterprise-Control System Integration, both of which have already been widely adopted as a reference
for the implementation of vertical integration on the higher level of the automation hierarchy [S07].
MESA provided a definition of 11 distinct functional areas of MES that cover the basic information
needed to run any type of plant—much in contrast to ERP systems that have no clearly defined
functionalities. This model has become an essential starting point for many MES tools currently on the
market. The purpose of ISA S95, on the other hand, is to define the interface between control functions
© 2011 by Taylor and Francis Group, LLC