The fieldbus of the future


Dieter Montanez

I think that plain ethernet will be the "fieldbus"
of the future (if something like this will still be necessary). We do already run several power plants all of them intra en extra wired using ethernet topologies (copper, fiber wnd wireless). At the "field level" we use OPC and MMS/UCA protocolls for control intercomunication. At the interplant and corporate level we run plain TCP/IP for SCADA and ERP and CMS integration.

Philippe Dallemagne

> Is TCPIP not the route of the future ?.
> I am under the impression 100MHz ethernet/TCPIP will be the fieldbus of the future.
> It’s cheap, widely used and every kid will know about it from the internet.
> With the right design (switches, hub and routers) will be “deterministic” (it will be so fast it can be classed as deterministic)

I would like to agree, but this last sentence can not be taken seriously, IMHO. Speed and determinism are independent (read "orthogonal") properties. One does not change the value of the other. Of course, in some low-traffic applications, Ethernet can behave correctly.
I agree with Andy P.....What about the FieldBus of the Present?

Take a look at the I/O vendors out there today. Especially ones that aren't directly associated with Allen Bradley or Siemans. Ask yourself what is the common thread in their Fieldbus offerings, and I think you will come up with CAN as the answer. Whether its DeviceNEt, SDS,Canopen, or whatever, they all have CAN chips, connectors, & protocol. In the spirit of this venue, if I was going to bring a Soft PLC to the marketplace, I would first ask "what hardware is available off the shelf?".

Hardware Vendors like Applied Data Systems and others already offer great Linux ready platforms with 2 CAN channels standard.

CAN is plenty fast for any DIO or analog devices. Motion Control can be handled via intelligent devices that have either direct motion capability or are their own producers on some mega network like Firewire.

Leave the HUBS and Switches for Peer-to-Peer Communications!!!!!!!

Frank Tambone

Doug: Do you have any information regarding the cost of individual node installation and startup for each of the solutions? Could you help? Thanks Frank Tambone
Ethernet is not "deterministic" at any load condition. It is by design probabilistic. The
real issue is performance. For many many applications Ethernet provides suitable performance even at higher load levels. The probabilistic nature is drowned out by the performance.

Well you could use full duplex, and a good switch and determinism is close to real. There
are no collisions so you have all the bandwidth twice because of full duplex uses both lines at
the same time. And a good switch is able to forward packets in real time with minimum latency.
The problem is that most plc interfaces dont support full duplex.
There is also the concept of Quality of service
where a router makes decisions on what packet has greater precedence over others on a network making it more deeterministic on high loads.
It seems that these features will be incorporated to the switches on a near future.

> I think that using ethernet TCP/IP for industrial controls has several problems. First,
the media and connectors are not industrial grade. <

Right the connector must be changed, The cable used must also be changed to a shielded one
of greater quality.


Peggy Van Walle, ING

I work in Europe. And here there are 2 types :
1. Profibus DP and PA
2. Eternet.
I believe that Etehrnet will be the future. We see more and more Ethernet in the industry. Also becauwe you can use FO wich has no problems
with EMC, which is here very important.
I have a question for you.
I think that USB (Universal Serial Bus) or something like that, will be the fieldbus for the future. It is based on an open platform (the
PC) that any one can provide products for it. This, joined to softwars standards like OPC and CORBA, will answer all our questions about
industrial automation, due to the highest degree of openness that could be reached (for now on).
Does any one agree with me?
Ing. Miguel A. Serradet
Dept. Automatización Industrial (DAI)
Habana Vieja, CP 10200
C. Habana. Cuba.