While talking to people about OPC-UA they usually say "Why change now? - everything I have is working great." In this, they make a good point and I'm always the first to say "If it ain't broken - don't try to fix it." But there are some important aspects you should be aware of so you can make informed choices moving forward.Legacy OPC is based on Microsoft's COM technology which has been deprecated for years now (The software definition of deprecation is "software features that are superseded and should be avoided") . Due to the large install base of programs that use the technology Microsoft still supports it. But moving forward Microsoft has signaled neither continued support nor intention not to do so.
The COM technology that legacy OPC depends on has also proven to be a huge security issue. This is so much the case that it has undergone a massive evolution to try to mitigate the factor and in doing so programs that once worked sometimes cease to work after an OS upgrade or patch. This is such a headache that one company delivered seminars around the country teaching people how to deal with COM/DCOM. In fact, the OPC tunnelers offered by a number of companies are a solution to this COM quagmire.
OPC-UA was designed to address these issues and a number of others. It leverages modern security and performance techniques. It can be scaled down to embedded devices or up to the enterprise level. Soon you could expect to connect to PLCs, barcode scanners, flowmeters and practically any other plant floor device directly using native OPC-UA protocol. That would get rid of the headache of a gazillion device drivers. Embedded device manufactures can buy the OPC-UA stack for embedded devices if writing their own stack seems formidable. I believe it's only a matter of time before we see this happen. That's how legacy OPC came to be.
OPC-UA offers IT industry standard authentication and encryption. This is a particularly important consideration when you consider the fact that plant floors increasingly are no longer islands. Consider the recent Stuxnet virus that specifically targets Siemens HMIs.
Unlike legacy OPC, OPC-UA can run on any OS, which might not seem important now, but in the future could be an important factor. We've run into an increasing number of US companies that refuse to run industrial applications on Windows and some of these are large companies. I'm not advocating one way or the other - I'm just commenting on what I see.
COM and DCOM go back to 1994 and there are roots even earlier. OPC-UA is a "now" technology which will probably have longevity since it is based on proven IT standards.
So what should you do moving forward? Clearly, new installations should be OPC-UA or you risk doing it twice. But what about those legacy installations? Sure, if it's working then leave it alone. But be very cautious of any OS upgrades or patches. One customer had automatic updates turned on and in the morning not one single HMI terminal worked, effectively shutting down a large company for the better part of a day.
That next project probably presents the most opportune time to made the move to OPC-UA.
2 comments:
I've been doing my finances on paper, why use a spreadsheet or specialized application? A shovel worked in the past, why use a back hoe? Any power tool for that matter?
My CRT TV works great. Sure, then keep it around. But why spend hundreds of $$$ to fix it if it breaks? Don't. And certainly don't buy a new one.
OPC-UA is where it's at! OPC-DA and COM were clunkers. There simply isn't a compelling reason to go into the future with "what you're used to". Do your research and make an educated decision before you buy.
Ditching traditional opc is a no brainer i agree, but i think it's sad that we have still not learned and made it an open standard. Ideally i would not want to touch it for that reason, but in the real world I may not have any choice...
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