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

57
OPC UA
Tuan Dang
EDF Research and
Development
Renaud Aubin
EDF Research and
Development
57.1 Introduction..................................................................................... 57-1
57.2 Overview of OPC UA System Architecture................................ 57-2
UA Client Application Architecture. •. UA Server Architecture
57.3 Overview of UA AddressSpace..................................................... 57-5
57.4 Overview of UA Services................................................................ 57-7
General Services. •. Discovery Service Set. •. SecureChannel Service
Set. •. Session Service Set. •. NodeManagement Service Set. •. View
Service Set. •. Query Service Set. •. Attribute Service Set. •. Method
Service Set. •. MonitoredItem Service Set. •. Subscription Service Set
57.5 Implementations and Products................................................... 57-10
57.6 Conclusion...................................................................................... 57-10
References.................................................................................................. 57-10
57.1 Introduction
OPC Unified Architecture (OPC UA) is the new standard of the OPC Foundation [1] providing
interoperability (e.g., Microsoft DCOM technology is not used anymore) in process automation and
beyond. By defining abstract services, OPC UA provides a service-oriented architecture (SOA) for
industrial applications from factory-floor devices to enterprise applications. Since the first introduction
of OPC in 1996, OPC UA represents a tremendous achievement, which started at the end of
2003, that proposes to integrate the different flavors of the former OPC specifications (DA, HDA, DX,
XML-DA…) into a unified address space accessible with a single set of services including IT security.
This chapter gives an overview over the architecture of OPC UA, its address space model and its services,
as well as different implementation flavors. For an in-depth study of OPC UA, it is advised to
get the specifications from the OPC Foundation Web site [2], which offers a lot of information about
implementations and product availability. It is interesting to know that the OPC Foundation is working
with bodies such as MIMOSA [3], ISA [4], and OMAC [5] to extend the UA standard to batch,
asset management, and other areas. Another important thing to know is that OPC UA provides support
for the electronic device description language (EDDL) [6] so that it is possible to make device
data parameters available to a large domain of applications through OPC UA. In this way, it gives an
alternative to the Web Services for Devices (WS4D) initiative [7] that proposes to specify and implement
WS4D using the Devices Profile for Web Services (DPWS) specification [8] that is the successor
of the Universal Plug and Play (UPnP) protocol.
Typical use of OPC UA concerns the middleware services that offer an abstraction layer between
devices (e.g., programmable logic controller [PLC], sensors, actuators,…) and plant-floor applications
(SCADA, MES,…), as shown in Figure 57.1.
57-1
© 2011 by Taylor and Francis Group, LLC