Tuesday, 24 March 2009

State Based Control

There is a new White Paper on ControlGlobal.com called "The Benefits of State Based Control" written by David A. Huffman from ABB
Walt Boyes calls it a "very important white paper". It is quite good and I recommend readers, specially those working in the Continuous process industries, to download it. You have to register with ControlGlobal to get it, but that is worth doing anyway.
The paper does not claim that SBC is new, and indeed it is not. In fact SBC - or something very similar, has been the basis for a lot of ControlDraw models since CD was first introduced, in the mid 90's, and that itself was based on previous paper based ways of specifying State Based Control.
And in turn these models were often then implemented using SBC, and on a variety of systems.
The paper also suggest that implementing SBC is something that ABB with it's 800ax system has removed barriers to. That may be so, but the paper is short on details. Interestingly one of the systems that CD models have been used to specify (and frequently) is Sattline, now owned by ABB themselves. A little known fact is that 800ax is a direct descendant of Sattline, a system that can probably claim to have been the first object oriented DCS, it has been around since the 90's.
One thing the paper mentions is ISA S88 Part 5, but I cannot really relate the paper to anything in Part 5.

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