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Open Platform Communications

April 12, 2024

Open Platform Communications (OPC) is a series of standards and specifications for industrial telecommunication. They are based on Object Linking and Embedding (OLE) for process control. An industrial automation task force developed the original standard in 1996 under the name OLE for Process Control. OPC specifies the communication of real-time plant data between control devices from different manufacturers.

After the initial release in 1996, the OPC Foundation was created to maintain the standards.[1] Since OPC has been adopted beyond the field of process control, the OPC Foundation changed its name to Open Platform Communications in 2011.[1] The name change reflects the applications of OPC technology for applications in building automation, discrete manufacturing, process control and others. OPC has also grown beyond its original OLE implementation to include other data transportation technologies including Microsoft Corporation's .NET Framework, XML, and even the OPC Foundation's binary-encoded TCP format.

History edit

The OPC specification' was based on the OLE, COM, and DCOM technologies developed by Microsoft Corporation for the Microsoft Windows operating system family. The specification defined a standard set of objects, interfaces e.g. IDL and methods for use in process control and manufacturing automation applications to facilitate interoperability. The most common OPC specification is OPC Data Access, which is used for reading and writing real-time data. When vendors refer to "OPC" generically, they typically mean OPC Data Access (OPC DA). OPC DA itself has gone through three major revisions since its inception. Versions are backwards compatible, in that a version 3 OPC Server can still be accessed by a version 1 OPC Client, since the specifications add functionality, but still require the older version to be implemented as well. However, a client could be written that does not support the older functions since everything can be done using the newer ones, thus a DA-3-compatible client will not necessarily work with a DA 1.0 Server.

In addition OPC DA specification, the OPC Foundation maintains the OPC Historical Data Access (HDA) specification. In contrast to the real time data that is accessible with OPC DA, OPC HDA allows access and retrieval of archived data.

The OPC Alarms and Events specification is maintained by the OPC Foundation, and defines the exchange of alarm and event type message information, as well as variable states and state management.[2] By 2002, the specification was compared to Fieldbus and other previous standards.[3]

An OPC Express Interface, known as OPC Xi, was approved in November, 2009, for the .NET Framework.[4] OPC Xi used Windows Communication Foundation instead of DCOM, so it can be configured for communication across the enhanced security of network address translation (NAT).[5]

About the same time, the OPC Unified Architecture (UA) was developed for platform independence.[5] UA can be implemented with Java, Microsoft .NET, or C, eliminating the need to use a Microsoft Windows platform of earlier OPC versions. UA combined the functionality of the existing OPC interfaces with new technologies such as XML and Web services to deliver higher level manufacturing execution system (MES) and enterprise resource planning (ERP) support. The first working group for UA met in 2003, version 1.0 was published in 2006.[6]

On September 16, 2010, The OPC Foundation and the MTConnect Institute announced cooperation to ensure interoperability and consistency between the two standards.[7]

Design edit

OPC was designed to provide a common bridge for Windows-based software applications and process control hardware. Standards define consistent methods of accessing field data from plant floor devices. This method remains the same regardless of the type and source of data. An OPC Server for one hardware device provides the same methods for an OPC client to access its data as any other OPC Server for any hardware device. The aim was to reduce the amount of duplicated effort required from hardware manufacturers and their software partners, and from the supervisory control and data acquisition (SCADA) and other human-machine interface (HMI) producers in order to interface the two. Once a hardware manufacturer had developed their OPC Server for the new hardware device, their work was done with regards to allowing any 'top end' to access their device, and once the SCADA producer had developed their OPC client, it allowed access to any hardware with an OPC compliant server.

OPC servers provide a method for different software packages (as long as it is an OPC client) to access data from a process control device, such as a programmable logic controller (PLC) or distributed control system (DCS). Traditionally, any time a package needed access to data from a device, a custom interface or driver had to be written. There is nothing in the OPC specifications to restrict the server to providing access to a process control device. OPC Servers can be written for anything from getting the internal temperature of a microprocessor to the current temperature in Monument Valley.[citation needed]

Once an OPC Server is written for a particular device, it can be reused by any application that is able to act as an OPC client. OPC servers can be linked and communicate to other servers. OPC servers use Microsoft's OLE technology (also known as the Component Object Model, or COM) to communicate with clients. COM technology permits a standard for real-time information exchange between software applications and process hardware to be defined.

Some OPC specifications are published, but others are available only to members of the OPC Foundation. So while no company "owns" OPC and anyone can develop an OPC server whether or not they are a member of the OPC Foundation, non-members will not necessarily be using the latest specifications. It is up to each company that requires OPC products to ensure that their products are certified and that their system integrators have the necessary training.[citation needed]

See also edit

References edit

  1. ^ a b "What is OPC?". OPC Foundation web site. Retrieved October 7, 2021.
  2. ^ OPC A&E specification
  3. ^ Li Zheng and H. Nakagawa (2002). OPC (OLE for process control) specification and its developments August 5, 2002. Vol. 2. IEEE. pp. 917–920. doi:10.1109/SICE.2002.1195286. ISBN 0-7803-7631-5. S2CID 114855720. {{cite book}}: |work= ignored (help)
  4. ^ "OPC Xi Interface Approved". Automation World. December 1, 2009. Retrieved October 7, 2021.
  5. ^ a b Gary Mintchell (November 20, 2009). . Feed Forward blog. Archived from the original on May 16, 2010. Retrieved October 7, 2021.
  6. ^ "History". OPC Foundation web site. Retrieved October 7, 2021.
  7. ^ . Press release. OPC Foundation. October 21, 2010. Archived from the original on June 16, 2011. Retrieved October 7, 2021.

External links edit

  • FatRat Library - free OPC server developers toolkit
  • OpenOPC - Open Source OPC client development in Python
  • OPC Foundation
  • OPC Programmers' Connection
  • OPC Unified Architecture Address Space e-book
  • prOpc Library - Open Source OPC server/client toolkit in Delphi

April 12, 2024
open, platform, communications, series, standards, specifications, industrial, telecommunication, they, based, object, linking, embedding, process, control, industrial, automation, task, force, developed, original, standard, 1996, under, name, process, control. Open Platform Communications OPC is a series of standards and specifications for industrial telecommunication They are based on Object Linking and Embedding OLE for process control An industrial automation task force developed the original standard in 1996 under the name OLE for Process Control OPC specifies the communication of real time plant data between control devices from different manufacturers After the initial release in 1996 the OPC Foundation was created to maintain the standards 1 Since OPC has been adopted beyond the field of process control the OPC Foundation changed its name to Open Platform Communications in 2011 1 The name change reflects the applications of OPC technology for applications in building automation discrete manufacturing process control and others OPC has also grown beyond its original OLE implementation to include other data transportation technologies including Microsoft Corporation s NET Framework XML and even the OPC Foundation s binary encoded TCP format Contents 1 History 2 Design 3 See also 4 References 5 External linksHistory editThe OPC specification was based on the OLE COM and DCOM technologies developed by Microsoft Corporation for the Microsoft Windows operating system family The specification defined a standard set of objects interfaces e g IDL and methods for use in process control and manufacturing automation applications to facilitate interoperability The most common OPC specification is OPC Data Access which is used for reading and writing real time data When vendors refer to OPC generically they typically mean OPC Data Access OPC DA OPC DA itself has gone through three major revisions since its inception Versions are backwards compatible in that a version 3 OPC Server can still be accessed by a version 1 OPC Client since the specifications add functionality but still require the older version to be implemented as well However a client could be written that does not support the older functions since everything can be done using the newer ones thus a DA 3 compatible client will not necessarily work with a DA 1 0 Server In addition OPC DA specification the OPC Foundation maintains the OPC Historical Data Access HDA specification In contrast to the real time data that is accessible with OPC DA OPC HDA allows access and retrieval of archived data The OPC Alarms and Events specification is maintained by the OPC Foundation and defines the exchange of alarm and event type message information as well as variable states and state management 2 By 2002 the specification was compared to Fieldbus and other previous standards 3 An OPC Express Interface known as OPC Xi was approved in November 2009 for the NET Framework 4 OPC Xi used Windows Communication Foundation instead of DCOM so it can be configured for communication across the enhanced security of network address translation NAT 5 About the same time the OPC Unified Architecture UA was developed for platform independence 5 UA can be implemented with Java Microsoft NET or C eliminating the need to use a Microsoft Windows platform of earlier OPC versions UA combined the functionality of the existing OPC interfaces with new technologies such as XML and Web services to deliver higher level manufacturing execution system MES and enterprise resource planning ERP support The first working group for UA met in 2003 version 1 0 was published in 2006 6 On September 16 2010 The OPC Foundation and the MTConnect Institute announced cooperation to ensure interoperability and consistency between the two standards 7 Design editOPC was designed to provide a common bridge for Windows based software applications and process control hardware Standards define consistent methods of accessing field data from plant floor devices This method remains the same regardless of the type and source of data An OPC Server for one hardware device provides the same methods for an OPC client to access its data as any other OPC Server for any hardware device The aim was to reduce the amount of duplicated effort required from hardware manufacturers and their software partners and from the supervisory control and data acquisition SCADA and other human machine interface HMI producers in order to interface the two Once a hardware manufacturer had developed their OPC Server for the new hardware device their work was done with regards to allowing any top end to access their device and once the SCADA producer had developed their OPC client it allowed access to any hardware with an OPC compliant server OPC servers provide a method for different software packages as long as it is an OPC client to access data from a process control device such as a programmable logic controller PLC or distributed control system DCS Traditionally any time a package needed access to data from a device a custom interface or driver had to be written There is nothing in the OPC specifications to restrict the server to providing access to a process control device OPC Servers can be written for anything from getting the internal temperature of a microprocessor to the current temperature in Monument Valley citation needed Once an OPC Server is written for a particular device it can be reused by any application that is able to act as an OPC client OPC servers can be linked and communicate to other servers OPC servers use Microsoft s OLE technology also known as the Component Object Model or COM to communicate with clients COM technology permits a standard for real time information exchange between software applications and process hardware to be defined Some OPC specifications are published but others are available only to members of the OPC Foundation So while no company owns OPC and anyone can develop an OPC server whether or not they are a member of the OPC Foundation non members will not necessarily be using the latest specifications It is up to each company that requires OPC products to ensure that their products are certified and that their system integrators have the necessary training citation needed See also editModbus RTU Lonworks KNX standard IEC 61850 MTConnectReferences edit a b What is OPC OPC Foundation web site Retrieved October 7 2021 OPC A amp E specification Li Zheng and H Nakagawa 2002 OPC OLE for process control specification and its developments August 5 2002 Vol 2 IEEE pp 917 920 doi 10 1109 SICE 2002 1195286 ISBN 0 7803 7631 5 S2CID 114855720 a href Template Cite book html title Template Cite book cite book a work ignored help OPC Xi Interface Approved Automation World December 1 2009 Retrieved October 7 2021 a b Gary Mintchell November 20 2009 OPC Xi Updated Feed Forward blog Archived from the original on May 16 2010 Retrieved October 7 2021 History OPC Foundation web site Retrieved October 7 2021 OPC Foundation and MTConnect Institute Announce a Memorandum of Understanding Press release OPC Foundation October 21 2010 Archived from the original on June 16 2011 Retrieved October 7 2021 External links editFatRat Library free OPC server developers toolkit OpenOPC Open Source OPC client development in Python OPC Foundation OPC Programmers Connection OPC Unified Architecture Address Space e book prOpc Library Open Source OPC server client toolkit in Delphi Retrieved from https en wikipedia org w index php title Open Platform Communications amp oldid 1181850137, wikipedia, wiki, book, books, library,

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