In his 1995 article, Robert Brooks discussed integration. In particular,
he explored the relative merits of open and proprietary systems,
concluding that, at the time, the proprietary approach still had much to
recommend it. Have his views changed?
Some things have changed hardly at all since I wrote my article in 1995.
It's still reasonable to define integration as linking two or more pieces
of equipment together in ways that bring benefits to the user. And the
objectives of integration are also still much the same: reducing costs.
Systems that are more flexible and functional and which are easier to
commission and then maintain through an effective diagnostics capability,
all help to reduce the costs of ownership.
To achieve this, users are still looking for open connectivity, so that
they can pick the 'best of breed' product from a range of suppliers,
without having to worry about compatibility issues. In reality, ten years
on, are they still typically only trusting products from one vendor when
true integration is their primary objective, and has technology really
moved forward enough to challenge this strategy?
If the basic ideas and objectives have remained unaltered over a decade,
a lot has changed. For example, my original article discussed the use of
Ethernet as an integration technology and concluded that it was often
unsatisfactory, particularly for the control of drives, because of the
unpredictability of message transit time. Today, with Ethernet links
routinely operating at 100Mbit/s, utilising full duplex and with managed
switches, these problems have been largely overcome. For example,
messages are now directed only at the desired node via managed switches,
greatly improving the throughput.
Ethernet technologies have subsequently gained ground in industrial
automation schemes and now form the basis of several new developments on
the industrial networking front, including Modbus on Ethernet, Omron FINS
on Ethernet and Ethernet Powerlink. Also, the Common Industrial Protocol
(CIP) implemented over Ethernet has led to Ethernet/IP (Industrial
Protocol) which will standardise communications over Ethernet as Profibus
and DeviceNet have for done for Fieldbus networks. These developments
give users much more choice in networking solutions.
Other big changes over the decade have been in the areas of data handling
and in communications with higher level systems. Today's automation
installations are required to link directly with factory management and
accounting systems. ActiveX components are one of the tools, which help
with implementing links between the production automation and commercial
levels of a business.
of breed' products, one of the more recent developments is FDT/DTM, or
Field Device Tool/Device Type Manager. This technology is led by a joint
interest group set up in 2002, which includes many of the leading
automation suppliers. FDT/DTM is not concerned with connectivity hardware
- rather it is a tool intended to improve the user configuration
environment, facilitating straightforward integration. It is one of the
modern faces of openness, which is still high on the wish-list of
automation system users.
To explain the functioning of FDT/DTM, it is easiest to think of FDT as a
receptacle and DTM as the link to that receptacle. Where a spreadsheet or
Visual Basic program may be a receptacle for ActiveX control, the FDT
receptacle will more usually be a specially written piece of software
provided by automation vendors.
DTM is a file, which not only allows configuration of a product, such as
a drive, to a Profibus network (the limit ten years ago), but now also
offers the ability to monitor, visualise and even have parameters
uploaded/downloaded from the FDT environment, via the network. This
includes any vendor's product, as any automation vendor can supply DTM
files for their products. The result is a truly