OLE for process control
Encyclopedia
OLE for Process Control which stands for Object Linking and Embedding
(OLE) for Process Control
, is the original name for a standards
specification developed in 1996 by an industrial automation industry task force
. The standard specifies the communication of real-time
plant data between control devices from different manufacturers.
After the initial release, the OPC Foundation
was created to maintain the standard. Since then, standards have been added and names have been changed. As of June, 2006, "OPC is a series of standards specifications". (Seven current standards and two emerging standards.) "The first standard (originally called simply the OPC Specification"), is "now called the Data Access Specification", or (later on the same page) "OPC Data Access
", or OPC Data Access Specification.
While OPC originally stood for "OLE for Process Control", the official stance of the OPC Foundation is that OPC is no longer an acronym and the technology is simply known as "OPC". One of the reasons behind this is while OPC is heavily used within the process industries, it can be, and is, widely used in discrete manufacturing
as well. Hence, OPC is known for more than just its applications within process control.
The OPC Specification was based on the OLE
, COM
, and DCOM
technologies developed by Microsoft for the Microsoft Windows
operating system family. The specification defined a standard set of object
s, interfaces
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 to read and write real-time data. When vendors refer to OPC generically, they typically mean OPC Data Access. OPC DA itself has gone through 3 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, so a DA 3 compatible Client will not necessarily work with a DA 1.0 Server.
----
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 and every other OPC Server for that same and any other hardware device. The aim was to reduce the amount of duplicated effort required from hardware manufacturers and their software partners, and from the SCADA and other 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 to allow any 'top end' to access their device, and once the SCADA producer had developed their OPC Client their work was done to allow access to any hardware, existing or yet to be created, with an OPC compliant server.
OPC servers provide a method for many different software packages (so long as it is an OPC Client) to access data from a process control device, such as a PLC
or DCS
. Traditionally, any time a package needed access to data from a device, a custom interface, or driver, had to be written. The purpose of OPC is to define a common interface that is written once and then reused by any business, SCADA
, HMI
,
or custom software packages.
There is nothing in the OPC Specs. 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.
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 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.
It is important to note that some OPC specifications are published, others are available only to member of the OPC Foundation. So whilst 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. Anyone can integrate OPC products, and there is no pre-requisite for the system integrator to belong to any organization. It is therefore up to each company that requires OPC products to ensure that their products are certified and that their system integrators have the necessary training.
(UA) has been specified and is being tested and implemented through its Early Adopters program. It can be implemented with Java
, Microsoft .NET, or C
, eliminating the need to use a Microsoft Windows
based platform of earlier OPC versions. UA combines the functionality of the existing OPC interfaces with new technologies such as XML
and Web Services to deliver higher level MES and ERP
support.
On September 16, 2010, The OPC Foundation and the MTConnect
Institute announced a cooperation to ensure interoperability and consistency between the two standards.
Object Linking and Embedding
Object Linking and Embedding is a technology developed by Microsoft that allows embedding and linking to documents and other objects. For developers, it brought OLE Control eXtension , a way to develop and use custom user interface elements...
(OLE) for Process Control
Process control
Process control is a statistics and engineering discipline that deals with architectures, mechanisms and algorithms for maintaining the output of a specific process within a desired range...
, is the original name for a standards
Standardization
Standardization is the process of developing and implementing technical standards.The goals of standardization can be to help with independence of single suppliers , compatibility, interoperability, safety, repeatability, or quality....
specification developed in 1996 by an industrial automation industry task force
Task force
A task force is a unit or formation established to work on a single defined task or activity. Originally introduced by the United States Navy, the term has now caught on for general usage and is a standard part of NATO terminology...
. The standard specifies the communication of real-time
Real-time computing
In computer science, real-time computing , or reactive computing, is the study of hardware and software systems that are subject to a "real-time constraint"— e.g. operational deadlines from event to system response. Real-time programs must guarantee response within strict time constraints...
plant data between control devices from different manufacturers.
After the initial release, the OPC Foundation
OPC Foundation
The Object Linking and Embedding for Process Control Foundation is an industry consortium that creates and maintains standards for open connectivity of industrial automation devices and systems, such as industrial control systems and process control generally...
was created to maintain the standard. Since then, standards have been added and names have been changed. As of June, 2006, "OPC is a series of standards specifications". (Seven current standards and two emerging standards.) "The first standard (originally called simply the OPC Specification"), is "now called the Data Access Specification", or (later on the same page) "OPC Data Access
OPC Data Access
The OPC Data Access Specification is the first of a group of specifications known as the OPC Specifications.OPC Data Access is a group of standards that provides specifications for communicating real-time data from data acquisition devices such as PLCs to display and interface devices like...
", or OPC Data Access Specification.
While OPC originally stood for "OLE for Process Control", the official stance of the OPC Foundation is that OPC is no longer an acronym and the technology is simply known as "OPC". One of the reasons behind this is while OPC is heavily used within the process industries, it can be, and is, widely used in discrete manufacturing
Discrete manufacturing
Discrete manufacturing varies from Process Manufacturing. In discrete manufacturing, the manufacturing floor works off orders to build something. Examples include toys, medical equipment, computers and cars. The resulting products are easily identifiable...
as well. Hence, OPC is known for more than just its applications within process control.
Origin and uses
The OPC Specification was based on the OLE
Object Linking and Embedding
Object Linking and Embedding is a technology developed by Microsoft that allows embedding and linking to documents and other objects. For developers, it brought OLE Control eXtension , a way to develop and use custom user interface elements...
, COM
Component Object Model
Component Object Model is a binary-interface standard for software componentry introduced by Microsoft in 1993. It is used to enable interprocess communication and dynamic object creation in a large range of programming languages...
, and DCOM
Distributed component object model
Distributed Component Object Model is a proprietary Microsoft technology for communication among software components distributed across networked computers. DCOM, which originally was called "Network OLE", extends Microsoft's COM, and provides the communication substrate under Microsoft's COM+...
technologies developed by Microsoft for the Microsoft Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
operating system family. The specification defined a standard set of object
Object (computer science)
In computer science, an object is any entity that can be manipulated by the commands of a programming language, such as a value, variable, function, or data structure...
s, interfaces
Interface (computer science)
In the field of computer science, an interface is a tool and concept that refers to a point of interaction between components, and is applicable at the level of both hardware and software...
and methods
Method (computer science)
In object-oriented programming, a method is a subroutine associated with a class. Methods define the behavior to be exhibited by instances of the associated class at program run time...
for use in process control and manufacturing automation applications to facilitate interoperability
Interoperability
Interoperability is a property referring to the ability of diverse systems and organizations to work together . The term is often used in a technical systems engineering sense, or alternatively in a broad sense, taking into account social, political, and organizational factors that impact system to...
. The most common OPC specification is OPC Data Access
OPC Data Access
The OPC Data Access Specification is the first of a group of specifications known as the OPC Specifications.OPC Data Access is a group of standards that provides specifications for communicating real-time data from data acquisition devices such as PLCs to display and interface devices like...
, which is used to read and write real-time data. When vendors refer to OPC generically, they typically mean OPC Data Access. OPC DA itself has gone through 3 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, so a DA 3 compatible Client will not necessarily work with a DA 1.0 Server.
----
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 and every other OPC Server for that same and any other hardware device. The aim was to reduce the amount of duplicated effort required from hardware manufacturers and their software partners, and from the SCADA and other 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 to allow any 'top end' to access their device, and once the SCADA producer had developed their OPC Client their work was done to allow access to any hardware, existing or yet to be created, with an OPC compliant server.
OPC servers provide a method for many different software packages (so long as it is an OPC Client) to access data from a process control device, such as a PLC
Programmable logic controller
A programmable logic controller or programmable controller is a digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or light fixtures. PLCs are used in many industries and machines...
or DCS
Distributed control system
A distributed control system refers to a control system usually of a manufacturing system, process or any kind of dynamic system, in which the controller elements are not central in location but are distributed throughout the system with each component sub-system controlled by one or more...
. Traditionally, any time a package needed access to data from a device, a custom interface, or driver, had to be written. The purpose of OPC is to define a common interface that is written once and then reused by any business, SCADA
SCADA
SCADA generally refers to industrial control systems : computer systems that monitor and control industrial, infrastructure, or facility-based processes, as described below:...
, HMI
Human-machine interface
Human-machine interface is the part of the machine that handles the Human-machine interaction- Overview :In complex systems, the human-machine interface is typically computerized. The term Human-computer interface refers to this kind of systems....
,
or custom software packages.
There is nothing in the OPC Specs. 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.
Once an OPC server
Opc server
An OPC Server is a software application that acts as an API or protocol converter. An OPC Server will connect to a device such as a PLC, DCS, RTU, or a data source such as a database or User interface, and translate the data into a standard-based OPC format...
is written for a particular device, it can be reused by any application that is able to act as an OPC client. 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.
It is important to note that some OPC specifications are published, others are available only to member of the OPC Foundation. So whilst no company "owns" OPC and anyone can develop an OPC server, whether or not they are a member of the OPC Foundation
OPC Foundation
The Object Linking and Embedding for Process Control Foundation is an industry consortium that creates and maintains standards for open connectivity of industrial automation devices and systems, such as industrial control systems and process control generally...
, non-members will not necessarily be using the latest specifications. Anyone can integrate OPC products, and there is no pre-requisite for the system integrator to belong to any organization. It is therefore up to each company that requires OPC products to ensure that their products are certified and that their system integrators have the necessary training.
Future
The OPC Unified ArchitectureOPC Unified Architecture
OPC Unified Architecture is the most recent OLE for process control specification from the OPC Foundation and differs significantly from its predecessors. The first version of Unified Architecture was released in 2006, after 3 years of specification work and another year of prototyping...
(UA) has been specified and is being tested and implemented through its Early Adopters program. It can be implemented with Java
Java (programming language)
Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities...
, Microsoft .NET, or C
C (programming language)
C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
, eliminating the need to use a Microsoft Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
based platform of earlier OPC versions. UA combines the functionality of the existing OPC interfaces with new technologies such as XML
XML
Extensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....
and Web Services to deliver higher level MES and ERP
Enterprise resource planning
Enterprise resource planning systems integrate internal and external management information across an entire organization, embracing finance/accounting, manufacturing, sales and service, customer relationship management, etc. ERP systems automate this activity with an integrated software application...
support.
On September 16, 2010, The OPC Foundation and the MTConnect
MTConnect
MTConnect is a manufacturing industry standard to facilitate the organized retrieval of process information from numerically controlled machine tools. The initiative began as a result of lectures given by David Edstrom of Sun Microsystems and Dr...
Institute announced a cooperation to ensure interoperability and consistency between the two standards.