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Distributed Control System (DCS)
Published in Chanchal Dey, Sunit Kumar Sen, Industrial Automation Technologies, 2020
It is not the only requirement to meet the features mentioned above. For secure and reliable exchange of data in industrial automation networks, what is needed is a common platform which should be independent and must ensure seamless flow of information among devices from multiple vendors. In this regard, OPC (Open Platform Communications) standard plays a pivotal role, which has a series of specifications developed by industry vendors, end-users, and software developers. These specifications define the interfaces between clients and servers, including access to real-time data, monitoring of alarms and events, access to historical data, and other applications. Initially, OPC standard was restricted to the Windows operating system (OS). As such, the acronym OPC was borne from OLE (object linking and embedding) for Process Control. Windows-dependent OPC standard is known as OPC Classic, which was adopted by a cross section of industries. Later on, OPC UA (Unified Architecture) overcame this dependence on Windows OS and presently industries are adopting this standard. This eliminated the vendor dependence when it comes to procuring instruments and devices from different sources.
Linking Factory Floor and the Internet
Published in Richard Zurawski, Industrial Communication Technology Handbook, 2017
OPC (originally OLE for Process Control, nowadays the abbreviation no longer has an official meaning) has become a de facto standard for interconnecting fieldbus systems and local area networks. Although the basic intention of OPC is to provide a comprehensive middleware, it is commonly used only for direct access to fieldbus data. This also fits the discussion of remote access possibilities to fieldbus gateways: the OPC server itself is the gateway; various OPC modules already implement most of the functionalities desired from a gateway and listed in Section 22.1. Like with all middleware approaches, there are no stand-alone client applications available. The objective of an OPC client is to provide communication and data exchange functionalities to other applications like SCADA or configuration tools [46]. From the viewpoint of vertical integration, it is important to notice that OPC has become a building block for many MES products [47]. In all these applications, OPC serves as a kind of driver to the fieldbus integrated in the application software. Alternatively, there can be an additional layer in the architecture, and OPC can be the fieldbus driver for a gateway, which in turn connects to the actual application via any other protocol, such as HTTP [39].
Networked Control Systems for Manufacturing: Parameterization, Differentiation, Evaluation, and Application
Published in Richard Zurawski, Networked Embedded Systems, 2017
James R. Moyne, Dawn M. Tilbury
OPC is an open communication standard that is often used in industry to connect SCADA systems and human–machine interfaces (HMIs) to control systems and fieldbus networks [24, 38, 62]†. It is based on the Microsoft DCOM standard [51] and is the dominant factory-floor application layer protocol utilized for diagnostics and is beginning to be used for sequential control [50]. The main benefit of OPC is that it allows any products that support the standard to share data. Although OPC actually consists of many different communication specifications, its most commonly used form is called Data Access, which supports both client–server and publisher–subscriber communication models. The server maintains a table of data values, and the client can read or write updates. The overhead associated with OPC (and DCOM in general) is significant, as shown in Figure 23.11. Most of this delay is due to the software implementation of the OPC protocol; OPC was never intended for a real-time environment. However, it is very useful to push data up from the low-level controls to the higher-level supervisors or diagnostic systems. It can also be used to send commands down from the HMIs to the control systems. Its high level of interoperability enables the connection of multiple control systems from different vendors in a unified manner. However, when OPC is used to send control data, the additional delay caused by the higher-level application layer protocol must be considered.
Digital twin for smart manufacturing: a review of concepts towards a practical industrial implementation
Published in International Journal of Computer Integrated Manufacturing, 2021
Luca Lattanzi, Roberto Raffaeli, Margherita Peruzzini, Marcello Pellicciari
A first issue in deploying the Digital Twin vision is related to production resources data access. Synchronization and consistency between the physical and the virtual worlds must be ensured. How to implement proper two-way communication protocols still represents an open issue, strictly related to the need for standardized connection and communication means, so to unify data formats, as well as their representation and exchange. OPC Unified Architecture (OPC-UA) is a well-known and widespread machine-to-machine communication protocol for information exchange among industrial automation systems and equipment, that targets the definition of an integral information model for data collection and control.
Digitalisation and servitisation of machine tools in the era of Industry 4.0: a review
Published in International Journal of Production Research, 2023
OPC UA (OPC Foundation 2019), first released by the OPC Foundation in 2008, is an open, platform-independent, and standardised communication protocol for industrial automation. OPC UA can be used for a variety of industrial automation devices including CNCs, PLCs, robots, AGVs, sensor, actuators, and so forth. Since it is not specifically designed for machine tools, only a few machine tool brands (e.g. Siemens and DMG Mori) provide off-the-shelf OPC UA support. Nevertheless, the OPC Foundation and the German Machine Tool Builders’ Association are jointly developing an OPC UA companion specification for CNC systems to broaden its support for machine tools.
Knowledge integration via the fusion of the data models used in automotive production systems
Published in Enterprise Information Systems, 2019
Rafal Cupek, Adam Ziebinski, Marek Drewniak, Marcin Fojcik
OPC UA (IEC 62541) is a service-based, client-server architecture that supports communication via Web Services or a modified TCP/IP protocol. It is primarily used for the vertical communication between real-time devices, Human-Machine Interfaces (HMI) (Mahnke 2009) and MES (Rafal Cupek et al. 2016). OPC can not only be used to exchange information to/from sensors, actuators, remote control or visualisation systems but can also support additional information about the system features including a description of the available services (Cupek et al. 2017a). OPC is maintained by the OPC Foundation and is recommended by the Industry 4.0 guidelines. OPC UA is based on an object-oriented model. The OPC UA address space (R Cupek, Ziebinski, and Fojcik) contains information about the organisation of the available information, which can be shared with connected clients. Using this mechanism, clients have the possibility to discover the object data structures that are managed by the servers. The units that organise the data into a structure are called types. They can be used to declare subtypes and for type inheritance. Types are used for variables, objects, data and reference definitions. OPC UA services are organised into ten Service Sets: Discovery, Session, NodeManagement, SecureChannel, View, Query, Attribute, Method, Subscription and MonitoredItem. The exchange of information begins with establishing a secured connection between the Client and the Server. A Client can query or browse the server’s address space to search for data. The OPC UA address space can include many servers and clients. If part of the information is stored on another server, a connection can be realised by references. To determine whether the information is important to a given client, the connection can be realised in a specific mode, which is called a subscription. Such a communication model permits both flexible and efficient communication in open systems.