As ever, the last people to have their views taken into consideration were the users. They really did want vendor independence based on interoperable, interchangeable devices and didn’t just expect vendors to pay lip service to that concept. However, when they began to make those views known in the clearest possible way by the exercise of their check books, even the world’s largest automation companies had to take notice.
First signs of that came back last spring when it became clear that Emerson, despite earlier protestations to the contrary, was providing DTMs for selected Rosemount instruments Last November the FDT Group announced its intention of opening negotiations with ECT and, at ABB’s Automation World in Florida, we picked up strong hints of a possible “rapprochement” between the rival parties (INSIDER, April 2007) so, when it was announced that the FDT Group and the ECT would be jointly hosting an “Editor Panel” at last month’s Hanover Fair, and when Emerson’s own European PR consultants started sending out the invitations, it seemed likely that something was in the wind.
None of that, however, led us, or indeed many other people, to suspect what was actually announced, which was, in effect, mutual capitulation and the second triumph for common sense and user power in as many weeks. To the sound of swords being beaten into plough shares and hatchets being buried, standing knee deep in olive branches and through huge mouthfuls of humble pie, the representatives of the two organizations announced that they had reached agreement “to combine efforts and work toward a unified solution for device integration that is compatible with both technologies,” a decision which would, they acknowledged, “satisfy one of the most frequent customer requests.”
To that end, the FDT Group is to become the fifth member of ECT and is to work with representatives of the other organizations “to finalize a solution and achieve a common framework that meets the requirements of all parties.” A number of factors seem to have come together to bring about what is certainly, in automation industry terms and, to quote the press release, a “historic opportunity for cooperation.” FDT advocates have long argued that their technology complements rather than replaces EDDL, and Dick Caro, who as chairman of ISA’s SP50 fieldbus committee during the fieldbus wars, learned a thing or two about automation industry infighting, agrees. In an email recently quoted on Walt Boyes’ Sound Off! Blog, he wrote that “The most basic difference between them is that FDT/DTM allows the instrument supplier to format the HMI screen display for that instrument,” while “EDDL allows the HMI supplier (typically the DCS vendor) to format the screen display for all field instruments.”
Most end users he had contacted wanted the DCS supplier to control the look-and-feel of the HMI to ensure consistency for the operator, but some instrument suppliers believed that they couldn’t make some of their diagnostic and calibration displays available via EDDL. “There are many other technical and procedural differences that may be important in competitive situations, but my overall conclusion is that these are complementary technologies,” he wrote.
With most FDT supporters taking that view, it was always going to be difficult for them to resist the notion of combining the two technologies if someone was able to show how that could be achieved without a loss of FDT functionality. Enter Professor Bender of the Institute for Technology in Munich (itm), who last November demonstrated how a combination of FDT, EDDL and the OPC Unified Architecture (UA) could provide a single common model. While there was understandable caution, it was recognized that this field device integration (FDI) model provided a way forward, if problems such as the provision of a migration path for existing DTMs could be overcome.
But then the FDT camp never denied the need for EDDL. Less easy to overcome, one suspects, were the prejudices of those in the EDDL camp who refused to recognize that there was any need for FDT at all. Here, we suspect is where Siemens Process Instrumentation & Analytics Division president Hans-Georg Kumpfmueller came in. He joined the Fieldbus Foundation board early last year and is also now the chairman of ECT. Last year he demonstrated a distinctly unSiemens-like flexibility on the subject of fieldbus by abandoning his company’s long standing policy of refusing to support Foundation fieldbus and entering into a technology sharing agreement with, of all people, Emerson. Under that agreement, Siemens gained access to Emerson’s Foundation fieldbus expertise in exchange for Emerson’s tapping into Siemens’ Profibus-related technology. After that, one might speculate, persuading Emerson Process Management president John Berra that it was time that Emerson accepted the inevitable on FDT would be comparative child’s play.
The final shape of the actual unified FDI model has yet to be determined, but it is clear that it will draw heavily on the itm proposals, using a subset of the OPC UA technology within a client-server architecture. One of the EDDL supporters’ key objections to FDT was its operating system dependence, while the FDT camp objected to the control over how information is displayed which EDDL conferred on the host system. As a result, the agreement specifies that the eventual solution should be operating system-, platform- and host-independent. Device vendors will have complete freedom to define the content of device pages to ensure that access is available to all the functionality of their devices. However, the look and feel will come from the host, although the device vendor will have the freedom to write applications for specific functionality.