# The fieldbus of the future

M

#### Miguel A. Serradet

(Originally posted Mon 10/19/1998) Hello everybody:
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?
Mike.
Ing. Miguel A. Serradet
Dept. Automatización Industrial (DAI)
EC MINBAS
Habana Vieja, CP 10200
C. Habana. Cuba.

J

#### Jeffrey Field

(Originally posted Mon 10/19/1998) I agree with you. I work for a large integrator, and we have developed our own object-based open control software which we are now using on 80% of our jobs. It is NT based, but can run on RTOS (QNX/CE) . It is based on the CORBA distributed object stardard. DCOM, Active X, and JavaBeans are also supported. It also has one common IEC-1131-3 standard programming interface for logic, robots, servos, etc. The open object standards and web-based technologies allow us to reduce programming by more than 60% and eliminate the SCADA middleware like Wonderware, Intellution, Factory Link, etc. Using a regular web-browser and JavaBeans the SCADA level is practically free (and way more connective).

Jeffrey Field
Applications/Marketing Manager

P

#### pir3

(Originally posted Mon 10/19/1998) I’m new to the USB and would like to know how it is different from the old RS-232. Both in hardware and software. Where can we find more information on the USB?

M

#### Mark Chesney

(Originally posted Mon 10/19/1998) I do not disagree with you about the importance of software standards like OPC and CORBA, however, USB does not appear to be a viable fieldbus candidate. While the chipsets are inexpensive (which makes it very attractive), it was designed for use as a high-speed “desktop” bus with very limited cable lengths. This makes it unsuitable for use in a distributed application.

B

#### Bob Old

(Originally posted Tue 10/20/1998) Howdy Mike,

USB would be good, as long as your fieldbus didn’t need to extend further
than 5 meters. See http://www.kavi.com/usb/developers/usbfaq.htm#longusb
What are the requirements for a fieldbus:
1) High speed
2) Deterministic
3) Interface cost less than US$1.00? 4) Inexpensive cable, less than ? per meter 5) Labor to install comm wire (in conduit), less than US$50.00 per meter?
What other factors do the list members consider important? Unpolarized, no topological restrictions?
If the labor to install the wiring is so high, why do we even consider the cost of the cable and interfaces?
Best,
B.O. Oct. 20, 1998
--
Robert Old, System Architecture, [email protected]
Siemens Building Technologies, Inc., Landis Division

J

#### Josué Portal

(Originally posted Tue 10/20/1998) What about ethernet?
Does anybody know something related with using ethernet as fieldbus?

R

#### Rick Daniel

(Originally posted Tue 10/20/1998) Automation Research Corporation and lots of others think it’s going to be Ethernet.

Rick Daniel
Intelligent Instrumentation
http://www.instrument.com

R

#### Rufus

(Originally posted Tue 10/20/1998) I believe Opto-22 now has Ethernet I/O.

R

#### Rob Entzinger

(Originally posted Wed 10/21/1998) 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.
AND
With the right design (switches, hub and routers) will be “deterministic” (it will be so fast it can be classed as deterministic)
Rob Entzinger
Applications Engineer
Schneider Automation (PTY) Ltd South Africa

B

#### Bennet Levine

(Originally posted Wed 10/21/1998) And once you add the cost of the 100BaseTX switches and routers your “cheap” system has grown significantly in price.
Bennet Levine
Contemporary Control Systems, Inc

J

#### Josué Portal

(Originally posted Wed 10/21/1998) Fieldbus Foundation have announced the development of a new high-speed fieldbus based on ethernet, I’m not sure they will use TCP/IP as transport layer of the protocol. Any way, the new standard will be ready by the end of this year and I’m anxious by seeing the replies from the others fieldbus groups. I’m specially interested in to know everything related with the use of ethernet/TCP/IP as fieldbus and to determine if there are other standards technically feasible enough to be use as fieldbus and that they are so open and so cost-effective as ethernet.
I would appreciate any information of any kind.
Thanks
Josué Portal

T

#### Thomas Wuensche

(Originally posted Wed 10/21/1998) I’d agree that Ethernet may be a good solution on the higher layers, networking PLCs, PCs and other complex intelligent devices. It doesn’t seem to be a good solu-tion for the sensor/actor level due to wiring restrictions. For the lower layers a bus like CAN or LON seems more appropriate. These networks are better adopted to the typical properties of the sensor/actor layer like small packets with realtime requirements from a large number of devices.
Best regards,

Thomas Wuensche

C

#### C. Thomas Wiesen

C. Thomas Wiesen
http://www.cae.wisc.edu/~wiesen

M

#### Miguel A. Serradet

(Originally posted Thu 10/22/1998) Thomas Wiesen wrote:
>First, the media and connectors are not industrial grade.
The media will have to be developed/adopted and tested for industrial use.<

That can be easily solved. You have to do that for every
fieldbus you want to develop. Cards, cables, conectors can be created and
certified.
Industrial PC manufacturer are doing it right now. Thats not a problem.

Thomas Wiesen wrote:
>A communication standard needs to be developed to allow standard plug play components (I have heard that someone is working on using the foundation fieldbus (?) protocol over ethernet).<

Why did you say It's impossible to implement plug&play on Ethernet? High Speed Ethernet (HSE) is the next standard promoted by FieldBus Foundation as device level network.(Control & Instrumentation August 1998)

Thomas Wiesen wrote:
>All internet communications are point to point transmissions. This
is grossly inefficient on a large scale when there are users that
want the same data all over the world. Take for instance downloading
of Netscape; a 17MB file that took me over 3 hours to download.
Netscape has lots of servers that are occasionally overloaded in
part because they are repeating 17 MB downloads to individual IP

That can be a big problem IF you are in a point to point Internet comunication. But is not in a Local Area Network where Ethernet (I think) behaves like a multi drop comunication network; and at 100Mhz it is very, very close to a deterministic network. Besides, in an industrial field bus you dont need to transfer that huge amount of data, a few BYTES will be enough.

Ethernet is just like you have mentioned:
cheap, nimble and fuel efficient.

Thomas Wiesen wrote:
>My personal opinion is that these benefits that are
in industrial networks will migrate (in the long run) to large scale
systems and not the other way around.<

I believe that large scale systems (ethernet) will incorporate these benefits, and not the contrary. Ethernet satisfies our technical and economics requirement for the industry, and is so widely extended that seems imposible to me that actual industrial field buses (which are used only by a small sector of the potential users) be able to succesfully contest with such an opponent.
I would like to hear some opinions
Greetings
Miguel
Ing. Miguel A. Serradet
Dept. Automatizacion Industrial (DAI)
EC MINBAS
Habana Vieja, CP 10200
C. Habana. Cuba.

J

#### Jeff Field

(Originally posted Thu 10/22/1998) Sixnet has ethernet I/O.

C

#### C. Thomas Wiesen

(Originally posted Thu 10/22/1998) Thomas Wiesen wrote:
>>First, the media and connectors are not industrial grade.
The media will have to be developed/adopted and tested for industrial use.<<

>That can be easily solved. You have to do that for every
fieldbus you want to develop. Cards, cables, conectors can be created and
certified.
Industrial PC manufacturer are doing it right now. Thats not a
problem.<

Haven’t seen any inexpensive washdown connectors for ethernet, do you have any information?

>Why did you say Its imposible to implement plug&play on Ethernet?
High Speed Ethernet (HSE) is the next standard promoted by FieldBus
Foundation as device level network.(Control & Instrumentation August 1998)<

Didn’t say it was impossible, just not there yet. The evolution of any network, in market terms, has been a number of years after the network has become reliable and proven. The network may arrive, but with all of the other existing networks out there now, there will be a big lag before there is a multitude of input and output devices available.
Its obvious that there is momentum for putting ethernet in manufacturing controls, and I am not really opposed to it. I just think that there should be a better solution than modifying a system that is missing some key features that make industrial networks valuable strictly based on speed. I don’t know exactly what that is.

Thomas Wiesen wrote:
>>All internet communications are point to point transmissions. This
is grossly inefficient on a large scale when there are users that
want the same data all over the world. Take for instance downloading
of Netscape; a 17MB file that took me over 3 hours to download.
Netscape has lots of servers that are occasionally overloaded in
part because they are repeating 17 MB downloads to individual IP

>That can be a big problem IF you are in a point to point Internet
comunication. But is not in a Local Area Network where Ethernet
(I think) behaves like a multi drop comunication network; and at
100Mhz it is very, very close to a deterministic network. Besides,
in an industrial field bus you dont need to transfer that huge amount
of data, a few BYTES will be enough.<

Yes, and in the words of Bill Gates, “640K will be more than anyone needs”. This is the exact reason for the evolution of the higher level control networks (Foundation Fieldbus, ControlNet, etc.). The bar is being raised for the amount of information and diagnostics provided in industrial networks. In a recent project that I worked on, the I/O count for the network was probably 3-4X what a point to point system would have been because the networked devices provided much more information. This system was mainly a discrete control system. Look at an HMI for a machine that is 15 years old (Button panel) compared to a similar modern machine with maintenance and help data available (touch screen) and compare the data transferred. And in the future when the operator interface for a purchased machine, and another HMI for a custom station, a UNIX box for MES, and a terminal to the site LAN (all in one location) are integrated into a single multi purpose unit. Lots of data.
I appreciate your response.

--
C. Thomas Wiesen

T

#### Thomas Wuensche

(Originally posted Thu 10/22/1998) Starting with your last comments: There are industrial fieldbus systems which have installed node count equal to the count of ethernet devices. Specially CAN comes to mind. Being used in automobiles, you’ll soon have >10 CAN nodes in every new car. This means >5 CAN nodes per person in industrialized countries in the near future. CAN controllers integrated with a microcontroller are available below \$3 in the correct volume today. However I would support your statement for the classic device level fieldbusses, here we can in fact observe the use of ethernet.
Regarding cabling: 100MB ethernet will not be usable as bus system on the sensor/actor level due to it’s point-to-point wiring structure. You’re not likely to connect a simple binary input over 100baseT to a hub. At least the idea was saving on installation cost through use of sensor/actor busses, and this would be difficult with 100baseT .
10base2, which would allow true network (line structure) installations, seems not appropriate due to it’s wiring characteristics (or would you feel comfortable installing 10base2 with screw terminals on perhaps unshielded twisted pair).
Ethernet has better characteristics for long messages. Short messages are much better supported by specialized busses (like again CAN).
What I would see for future installations is a sensor/actor level bus for networking (intelligent) components on the sensor/actor level and above that ethernet on the higher levels. Instead of PLCs used now between the sensor/actor and the higher levels, gateways may be used between both systems.
Best regards,
Thomas Wuensche

D

#### Doug Smith

(Originally posted Fri 10/23/1998) Hi !
I just returned from the ISA Houston show, the big hit of the show was
the
“Super Bus” or IEEE 1451, HP was showing a system running on off the
shelf Ethernet that had the ability to Syncronise the NCAP’s (Network
Capable
Application Processors) to within 200 nano seconds, not a miss print 200
ns
Checkout HP’s Industrial ethernet site at www.hpie.com
A survey was taken at the show and the following question was asked
“What final standard for a control network have you installed, intend to
install,
are leaning toward, or wish you had installed?”
The answer for North America and Outside North America :
Ethernet 26% 9%
Serial port 4% 2%
IEEE488 0% 0%
4-20ma 8% 4%
HART 3% 0%
DeviceNet 4% 0%
Interbus-S 0% 1%
Profibus 1% 6%
Foundation Fieldbus 8% 17%

Doug Smith
[email protected]

M

#### Michael Griffin

(Originally posted Thu 10/22/1998)
<clip>
Ethernet satisfies our technical and
economics requirement for the industry, and is so widely extended
that seems imposible to me that actual industrial field buses (which
are used only by a small sector of the potential users) be able to
succesfully contest with such an opponent.
<clip>

A number of the lower end industrial buses are based on CAN, which is actually an automotive network (i.e. used in cars). It was adapted for use in industry because it was cheap, rugged, and readily available. The automotive market is huge, so as this technology is more widely used the production volumes of CAN hardware may become much larger than the ethernet market.
Industrial networking may indeed adapt other commmercial systems to it’s needs, but this doesn’t mean that it will necessarily be the type of stuff you find on your desktop.

Michael Griffin