OPC: at the heart of the Internet of Things
20 June 2014
Suzanne Gill finds out more about OPC developments and the potential role it has to play in the Internet of Things in the industrial environment.
The demand for greater manufacturing efficiency is resulting in a greater push for operational excellence to ensure efficiency throughout the manufacturing process.
The majority of initiatives, which are often instigated at the enterprise level, rely on a steady flow of information from the field, in close to real-time. As such, any operational excellence initiatives need to consider the long-term sustainability of the plant floor data flow which can be problematic given the fact plant controls are regularly updated and changed. This can make plant floor data collection difficult to achieve.
“Because data is collected and stored in many different applications on the plant floor – in databases or historians– bringing it all together at enterprise level can be a complicated procedure. OPC was designed to solve this problem, offering a uniform way of accessing information from plant floor devices,” explained Darek Kominek, marketing manager at MatrikonOPC.
“Traditionally, if you wanted an application to share its data, a driver from the application to the monitoring source was needed. So, for a PLC to share real-time data with an HMI and also supply data to a historian and a vibration monitor, for example, would require three separate dedicated drivers and connections from the PLC to each separate monitoring system,” he continued.
This raises both business and technical problems. Multiple data requests can swamp the controller’s processor with requests, taxing the system. The cost of maintaining all the different versions of driver, and the need to change these if the device is upgraded or changed, also greatly increases lifecycle costs.
An interoperability standard
OPC (originally called OLE for Process Control, where OLE referred to Microsoft’s Object Linking and Embedding technology) was developed to provide an interoperability standard for the secure and reliable exchange of data independent of the vendors the data sources and data consumers came from. The OPC standard consists of a series of specifications, developed by industry vendors, end-users and software developers and which define the interface between OPC clients and OPC servers. This includes access to real-time data, monitoring of alarms and events, access to historical data and other applications.
OPC defines how the data source portion of a driver talks with the client portion – in this way an OPC server for a PLC knows how to get information to and from the device and can pass this on to any other application with an OPC client. This allows OPC-enabled clients to talk directly to the server to get information from the device, allowing the device processor to concentrate on its primary task.
“The original drive for the development of OPC came from the process level,” said Kominek. “To control what was happening in complex process environments, bringing data together at the supervisory layer to enable improved process productivity. OPC is already the defacto standard for connectivity and with its growing use came the realisation that the data could offer benefits at the business level too, for example, providing real-time process productivity dashboards.”
Availability of OPC UA
The latest OPC technology development is the increasing availability of OPC UA (Unified Architecture) compliant devices. “Unlike OPC Classic, which can only be employed in Windows-based machines, OPC UA is platform-independent and can be embedded directly into devices, connecting them to the wider network for data gathering purposes,” enthuses Kominek.
OPC UA offers the ability to model data and is aware of its context, ensuring that only the right information is passed on, from the huge amount of data that a device can provide. All available information visible to an OPC server and whatever information is relevant is passed on to requesting clients. Today the resulting real-time dashboards and data archiving can also help companies meet increasing regulatory requirements and this is becoming an important driver for OPC.
“OPC UA is squarely at the centre of the Internet of Things in the industrial environment,” said Kominek, “making it possible to share data between different systems, and right down to device level. “Because OPC UA can be embedded, native UA devices can now be created and it is no longer just a translation layer. This is a fundamental shift. Instead of OPC residing on a PC, it can reside in the devices themselves, making it less expensive to access data from deeper in the plant floor which, traditionally, may not have been costly effective to setup. “
MatrikonOPC now offers a UA Proxy, designed to make it easy for companies to take advantage of OPC UA, while continuing to use existing OPC classic architectures.
The OPC UA standard is backward compatible with classic OPC from a data perspective, but it does use different technologies to establish connections and transmit OPC data. Using the UA Proxy enables companies to bridge this gap, making it possible for them to maximise their ROI on existing classic OPC architecture and enabling adoption of new OPC UA based product offerings at their own pace.
“Companies using OPC classic have seen the benefits that the adoption of open standards can bring to their business as well as the additional value OPC UA has to offer, but sometimes have concerns about how to go about tying the two technologies together,” said Kominek. “The UA Proxy removes those obstacles – providing a reliable way to seamlessly combine the two OPC technologies.”
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