Software for the mind: A book review of the IEC 61499 function block standard
September 15, 2008
By Jeremy Pollard
While this book is primarily written for academia and for course study, it can very well suit some control engineers and some process guys to allow them to learn more about the IEC 61499 standard. So, for those who have no idea what IEC 61499 is or how it can help you, this book can answer most of your questions.
This IEC standard, as author Valeriy Vyatkin states in the introduction to IEC 61499 Function Blocks for Embedded and Distributed Control Systems Design, was in development for more than 10 years. It was developed as an answer to the question, “How do I protect my intellectual property (IP) in an open automation software solution?” The answer? IEC 61499. The IP is kept beneath a protected function block and the only items that are exposed are the inputs and outputs, along with some data — if the developer allows it.
The author begins the journey with a quick start chapter and a follow-up chapter which explain the “where we came from” scenarios, which is very cool since many younger readers may not realize the history. Being a teaching book, Vyatkin may rely on the guidance of the instructor a bit too much, since he is talking about loading files into software in the quick start chapter without introducing the software itself. There is a footnote at the end of the chapter, but it IS a quick start, one might argue!
He uses a flasher application to describe and to demonstrate the function block approach. The software he uses is a free development tool developed by Dr. James Christensen, a former Rockwell engineer and guru of IEC 61499. You can find it at www.holobloc.com.
The history lesson is very valuable, since the premise of IEC 61499 is a distributed control system. The comparisons he makes are very valid and succinct. There are review questions at the end of each chapter, but the answers don’t form part of the book. Perhaps they do in the instructor’s guide?
Vyatkin does a really good job describing a typical automation sequence and how a normal PLC control system would handle the process, and then breaks it down into a next generation control system requirements. He introduces the concept of portability (of function blocks). This should pique your interest!
The ability of having an agile control system, with the ability to rescue certain blocks in a different application(s), is appealing and is a failure of IEC-61131, the programming standard for some typical control systems, which Vyatkin notes in the book. Although it may sound like a sales pitch, he makes a good case for the application of the standard in future control systems in chapter four.
The real meat and potatoes of the standard are introduced in the following chapters, including the software development platform that Christensen developed.
When Vyatkin diverts into system design and methodologies used, the academia comes out in his writing. While I am sure he didn’t intend it, his vision and opinion on the future of our industry is refreshing.
Have you ever heard of Model-View-Controller (MVC)? I hadn’t. After a quick Google search, I found a wiki page that explained the concept. The terminology used with MVC in the real world says nothing of PLC, automation or control. Vyatkin’s professorial background is a big help here. He takes a rather aged architectural pattern and applies it to something that only a researcher could. He applies it to the object-oriented exposure of IEC 61499 and flows it into design framework. He talks about encapsulation of functions to ‘pretty up’ the function block diagram. Academia at its best, folks!
This book is more than the technical jargon and application of the function block platform. As informative as it is from a technical perspective, it also provides readers with an historical perspective that they wouldn’t find elsewhere. A good mix of academia, practicality, opinion and history provides for a quick read.
But although it is a good reference book that can provide you with a good introduction into the world of distributed control, it falls a bit short of being an actual development guide. You may have to go to holobloc.com or isagraf.com for more detailed application and design implementation information.
Speaking of which, ISaGRAF is the only product that commercially supports the IEC 61499 standard. That website can provide you with additional information on the implementations of the standard.
Both websites have downloadable software for you to play with. It is a worthwhile proposition after you have read this book. Some knowledge of IEC-61131 would be a benefit!
Jeremy Pollard is a 25-year veteran of the industrial automation industry. He has worked as a systems integrator, consultant and an educator in the field. Jeremy can be reached at email@example.com.
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