SEP-OCT 2017

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AUTOMATION BASICS INTECH SEPTEMBER/OCTOBER 2017 41 of an industrial application. Older Windows versions became unsupported and eventually unavailable, and the costs to upgrade (deploy- ment, testing, downtime, new PCs) became unacceptable. In manufacturing, automation processes are built to last, and it is common to build production processes for diapers, soap, tea, and hundreds of other products that run for five, 10, or 20 years. There was a strong desire to run OPC Classic servers with longer lives, stable hardware, and smaller, embedded platforms. Companies asked, "Why do I have to be tied to Microsoft?" With devices like flowmeters, drives, programmable controllers, and other field de vic- es becoming smarter, users asked, "Why can't they be an OPC server?" There was also dissatisfaction that OPC re- quired multiple layers of networks and com- puters to communicate field device data to all those data-hungry factory automation, histo- rian, and enterprise servers. Further, since there is no metadata that provides the semantics and definition of units, scaling and strict configura- tion control had to be maintained, making sys- tems brittle. Every time a new piece of data was added, you had to reconfigure multiple systems without breaking any of them. "Yuck" is the technical term for it. More recently, OPC does not have a direct way to communicate with the Internet and cloud applications. OPC UA to the rescue The answer to the problems is OPC Unified Ar- chitecture (UA), referred to as UA throughout this article. UA is the next generation of OPC technology. It is a more secure, open, and reli- able mechanism for transferring information between servers and clients. It provides more open transports, better security, and a more comprehensive information model than OPC Classic. UA has a very flexible and adaptable mechanism for moving data between enterprise systems and automation, controls, monitoring devices, and sensors that interact with real- world data. OPC UA overcomes the limitations of OPC Classic with: n Scalability and platform independence: It can be supported on high-end servers and on low-end sensors. UA uses discoverable pro- files suitable for tiny embedded platforms as servers. n Flexible address space: Address space is orga- nized around the concept of an object, which is an entity consisting of variables and meth - ods. It is a standard way for servers to transfer information to clients. n Common transports and encodings: Standard transports and encodings make sure connec- tivity is easily achieved in embedded and en terprise environments. n Security: A sophisticated security model for authentication of clients, servers, users, and communication integrity. n Internet capability: Fully capable of moving data over the Internet. n Robust set of services: Full suite of services, in cluding managing events, alarming, read- ing, writing, and discovery. n Certified interoperability: UA certifies defined profiles to guarantee connectivity between a client and server. n Sophisticated information model: UA profiles more than just an object model, enabling true information sharing between clients and servers. n Sophisticated alarming and event management: UA has a highly configurable mechanism for providing alarms and event notifications to interested clients. Alarming and event mecha- nisms go well beyond the standard change-in- value type alarming found in most protocols. n Integration with standard industry-specific data models: The OPC foundation is working with many industry trade groups that define specific information models for their indus- tries to support those information models within UA. COM interface OPC DATA Proprietary driver Serial, Ethernet, CAN Device X OPC SERVER MICROSOFT COM Application COM interface Application COM interface Application COM interface } Figure 1. OPC Classic using Microsoft COM

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