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Open Network Options
Real Openness and Some New OPC Glue Enable Industrial Network Interoperability
ControlDeisgn.com
By Paul Miller and Joe Feeley, Editor in Chief
Truly open networking solutions are important to both end user and manufacturer.
For the user, an open solution allows selection of best-in-class components, since many suppliers will try to provide additional, unique features that make them stand out.
“Since the connectivity and communication level is well-defined, these differences tend to focus on true usability enhancements like better LEDs, additional diagnostics via LCD displays or higher quality housings and connectors,” says Helge Hornis, Ph.D., manager, intelligent systems, Pepperl+Fuchs. “Because a truly open networking solution allows the relatively easy exchange of one manufacturer’s product with those from another manufacturer, end users gain a level of security and long-term availability simply not possible with proprietary equipment.”
There are reasons why manufacturers favor open solutions, too. “A well-defined open solution makes strictly defined interoperability testing a part of the device requirements,” adds Hornis. “This means that products for all participating vendors will work together.” That’s another advantage for the user.
Sometimes, however, interoperability needs some assistance. The new direction that OPC UA takes should help with that.
The next generation of integration standards from the OPC Foundation, OPC Unified Architecture (UA), abandons the Microsoft–based structure of its much-criticized, DCOM-based, OPC DA predecessor and embraces open, vendor-independent Web Services. OPC UA ties together functions from earlier OPC specifications—data access (DA), historical data access (HDA) and alarms & events (A&E)—and enables a common services-oriented architecture (SOA) environment.
The backward-compatible OPC UA looks to cross-platform interoperability and supports a much richer set of data and information.
The initial OPC UA specs were released to early adopters in 2006 and the first OPC UA-enabled products just now are beginning to hit the market.
Most of the OPC UA questions the OPC Foundation receives from users and automation vendors address problems with existing OPC products, says Jim Luth, OPC Foundation technical director. “This includes getting rid of DCOM, which is difficult to configure and has firewall issues,” he adds. OPC UA, says Luth, is built on Internet protocol (IP) technology. “UA is designed to be both cross-platform and transportable,” he states. “You’ll see UA in devices and places where you’d never see DCOM-based applications.”
With industrial networking technologies from OPC, PNO, HART, FF and FDT all coming together, factory automation is the next target. “Once we add on the capabilities of DeviceNet, ControlNet and EtherNet/IP, we’ll essentially have one way for doing configuration, diagnostics and run-time operation for any device, regardless of the network it’s on,” says Tom Burke, OPC Foundation president.
The foundation aims to have a robust third-party compliance program in place before UA products ship in any quantity. A new independent certification test lab at Ascolab’s main facility in Erlangen, Germany, is staffed by experienced designers and developers of OPC certification tools, says Burke. The program means users should expect reduced installation costs and products that perform reliably in multi-vendor installations.
Since UA involves a richer information set, across plant networks and between plant and enterprise networks, it will be important to follow best practices for networked applications.
“We’ll have to design networks that route the information where and when it’s needed,” says Stephen Briant, product manager at Rockwell Automation. “We need to use best practices to prevent unintended devices or packets from showing up on our wires. I don’t see best practices, relative to firewalls, traffic limitations and so on, changing all that much. We need to consider the impact that new, open devices will have on network design to assure that it remains performant and secure.”
Barriers between engineers and IT personnel actually might come down. “The goal is to keep things simple enough so points of confrontation don’t develop,” comments Keith Jones, product marketing manager at Wonderware. “Examples can include opening ports, firewalls or user accounts. OPC UA addresses these points of conflict by being easy to engineer, performant and interoperable. The OPC UA discovery service, for example, helps monitor network performance. UA also is very easy to connect into PLCs, alarming applications, ERP systems and the like.”
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