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TC4 - Communication
PLCopen and OPC Foundation combine their technologies
The technical specification "OPC UA Information Model for IEC 61131-3", version 1.00 is now available. Click here to download the specification. PLCopen and the OPC Foundation joined forces in 2008 to combine their technologies to a platform and manufacturer-independent information and communication architecture. A combined working group was started, focused to the mix of OPC Unified Architecture (UA) and IEC 61131-3, which creates interesting options for the realization of automation structures. The objective of the combined technologies is to increase the efficiency of the engineering process and information exchange. Today there are many historically grown data exchange protocols used in various industries. They offer little possibility to transport complex data and the extensibility is very limited. OPC Unified Architecture however, offers the basis for universal, secure and reliable network communication, i.e. provides the monitoring of configurable timeouts and connecting interruptions and encrypted communication. To use this communication as a standard for the IEC 61131 environment will lead in many industries to a new form of information exchange: if an industry has defined a specific profile e.g. a data structure or a function block, then the question of secured and efficient data exchange and the reusability of the visualization objects is already solved. With the combination of PLCopen and OPC UA, an additional level of interoperability is standardized on top of IEC61131-3. The first step of the joined working group was the mapping of the IEC 61131-3 software model to the OPC UA information model, leading to a standard way how OPC UA server-based controllers expose data structures and function blocks to OPC UA clients like HMIs. This first step was achieved in a very short time followed by first implementations demonstrated at the SPS/IPC/Drives 2009 in Nuremberg, Germany.
A new working item is Manufacturing Execution
System (MES) connectivity, defined as the
integration of machine and process data for
utilisation by MES based on OPC UA and PLCopen.
The aims of this joint working group focus on two main topics:
Based on the OPC UA communication mechanisms any desired information can be exchanged between the control level and MES systems. It is assumed that the content can be adjusted on a project-specific basis in the products (e.g. controllers). For example, in an IEC 61131-3 based control system the controller programmer can define the content and program the processes through suitable data structures and function blocks.
Nevertheless, it makes sense to
define the content further. To this end, common
semantics that are understandable for all
participants are defined and specified with the aid
of clear information model definitions. Where
appropriate, generic profiles with general key data
can be found or defined with sector-specific
profiles. These profiles can then be realised
through a standardised PLCopen block library, for
example.
Read more about the cooperation between PLCopen and OPC Foundation:
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