Open Controller

  • Thread starter leonardo chacon
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Thread Starter

leonardo chacon

Can I say that an OPEN CONTROLLER is a hardware able to support the instalation of different kind of operating systems like Windows NT, CE, 2000, Linux, etc.?

Can I use a personal computer or a server with an OS like Windows or Unix for process control and or it is better to use a PLC for it?

Which is the operating system of a PLC like Allen Bradlley, Siemens. Are these PLC able to support all the commercial operating systems?

I hope someone can understand my doubt.

Thanks a lot.
 
About your questions, I have my own concept above open controller and it is related when there is feedback of the system or close loop, generally represented by sensors or similar advices.

For me open controller isn't related with the O. S.

About the use of PLC or PC, that depends of your application....... a PLC is commonly used on automation, because have a lot af advantages.

I have worked with Allen bradley PLCs, on NT, but don't support linux. for additional information go to www.ab.com

good luck.....


sarosero
 
V

Vladimir E. Zyubin

Hello List,

The word "open" is nothing, but an ads trick.
Get the docs and read the parameters of the controllers.
If you like, the word "open" means "with the capabilities from the docs".
(If the docs reflect the reality, heheheh ;)

Best regards,
Vladimir mailto:[email protected]
 
C

Curt Wuollet

> Can anybody tell me what is the real meaning of an OPEN CONTROLLER.

Right now, it doesn't mean much. The term is applied to any controller that marketing declares open, with or without any justification. Folks like OMAC use it for anything that runs on a Windows PC.

> Can I say that an OPEN CONTROLLER is a hardware able to
> support the instalation of different kind of operating systems like
> Windows NT, CE, 2000, Linux, etc.?

No, not yet, most of the folks using the term mean you can run any OS you want as long as it's Microsoft. I am working on a controller design that would meet your criteria. It will be intended
for Linux and the LPLC, but, being _truly_ open, there should be no problem running the others. The only existing Open Controller would be a generic PC carefully selected so it contains no Winjunk that is, no components that only run on Windows. These are getting more rare, but since the "reccomendations" that Intel and MS cook up are often ignored, they can still be had. It's easiest to buy them as "Linux PC's"

> Can I use a personal computer or a server with an OS like
> Windows or Unix for process control and or it is better to use a PLC
> for it?

That depends entirely on the situation. But, Yes, PC's can be used successfully and have been for many years. The situation has gotten worse lately, IMHO, with wider application and
misapplication of products that are less than industrial strength.

> Which is the operating system of a PLC like Allen Bradlley,
> Siemens. Are these PLC able to support all the commercial
> operating systems?

No, not likely either. They typically use a small custom executive or occasionally a commercial RTOS. The hardware is becoming more "PC-like" with more power and integration.

> I hope someone can understand my doubt.

I understand, the intent seems to be to confuse the whole issue.

Curt W
 
S
For many companies and groups, OPEN can be a hollow term used and abused by the marketing folks.

At least one group put its code where its mouth is: the EtherNet/IP Developers Toolkit is available free for the download from WWW.ODVA.ORG and it INCLUDES all the protocol stuff you need above WINSOCK -- you just write your applications.

And there is a sample Server Appplication -- with SOURCE.

And a sample client to test the Server.

And a network analyzer that decodes the packets....

Now that is a different use of "OPEN"..... Backed by CODE!

Cheers! steve
----------------------------------------------------------------
Steven B. Cliff title: VP, Research & Development
Control Technology, Inc. email: [email protected]
5734 Middlebrook Pike web: http://www.controltechnology.com
PO Box 59003 voice: (865) 584-0440
Knoxville, TN 37950 fax: (865) 584-5720
 
J
I think the term you are reaching for is "open *LOOP* controller". All you did here was to cloud the issue even further....

--Joe Jansen
 
J
An OPEN CONTROLLER is anything that the individual hardware company's marketing department thinks it should mean. It has
very little bearing on the equipment's capability.


-> Can I say that an OPEN CONTROLLER is a
hardware able to -> support the instalation of different kind of
operating systems like -> Windows NT, CE, 2000, Linux, etc.?

No. That would be just about every PC in the world. A proprietary SCADA or DCS package running on top of a proprietary Operating System would not represent an open system (in my, and several others opinion anyway!)

-> Can I use a personal computer or a server with an OS like
-> Windows or Unix for process control and or it is better to use a
-> PLC for it?

Depends on what you want to do, and who you ask. PC based control for anything critical is generally considered a "bad thing" by most, due to OS instability. Also, you would definitely want a dedicated machine.

-> Which is the operating system of a PLC like Allen Bradlley,
-> Siemens. Are these PLC able to support all the commercial
-> operating systems?

PLC's do not support ANY of the commercially (or freely) available OS's. A PLC runs its own proprietary "OS" of sorts that scans the program and controls the IO. If you mean what is available for programming an AB or Siemens, then you are looking at windows. As far as what controls the PLC however, you only get what is
embedded.
 
R
> > Can I say that an OPEN CONTROLLER is a hardware able to
> > support the instalation of different kind of operating systems like
> > Windows NT, CE, 2000, Linux, etc.?
>
> No, not yet, most of the folks using the term mean you can run
> any OS you want as long as it's Microsoft

Actually things are generally far more specific, like NT4.0 SP4 or SP5 but not SP6.

> > Can I use a personal computer or a server with an OS like
> > Windows or Unix for process control and or it is better to use a PLC
> > for it?

PC hardware is capable (allthougth hardware wise PLC's are often better adapted). OS's are not. The type of scheduling and message queueing that works best on servers and desktop systems is pretty incompatible with what is desired in real time control. Solutions that use 'normal' OS's such as NT and Linux for real time control do so
by running a mini RTOS (real time OS) in paralell with the main OS, with processor time being split between the two OS's by time slicing. Normal
applications must 'interface' to the RTOS based code as if it were remote - too all intents and purposes it is like having two computers.

So, the short answer is 'No normal OS is particularly good at doing control, but run it in paralell with an RTOS and you will add RTOS
functionality (which is pretty much the same regardless of the OS).

As for choice of host OS then, there is little to choose from the control point of view, because that code runs on the RTOS virtual machine.

Using an NT base, you could also run Microsoft office on the same machine that is controlling your 3 axis controller.

Using Linux you cannot run office, but you do get the network inteconnectivity and remote access features of UNIX in a package that can fit in a flash memory disk.

Actually, there is another consideration, using standard OS's in industrial control requires interfacing to pretty obscure hardware. It is notoriously difficult to write device drivers for some OS's, whilst others make things absurdly simple. Ironically, and maybe contrary to what one might expect, it is NT that is difficult and Linux which is easy. SUN, however, is also difficult from a driver point of view, whilst PicoBSD should be fairly simple (but I am guessing here).
 
C

Curt Wuollet

Hi Roger
I don't disagree with your assessment on OS suitability for control, but I would add that Linux is much more than RedHat, Caldera, etc. Since I am working on the Linux PLC and I want it to run on SBC's and embedded platforms, when I say Linux, I am including the versions done by Monta Vista (Hard Hat Linux) and LynuxWorks (Blue Cat Linux) as well as Lineo and several others. These versions are intended specifically for embedded and realtime applications and replace the features that make a great general
purpose OS with those suitable for low latency interrupts, realtime scheduling ordered priorities and the like. This alternative to running Linux as the lowest priority task of a real time executive makes it much easier to code applications that have stringent time requirements and integrate them with "normal" Linux applications. There is so much work going on in this area that new announcements are coming out every day. And true to its Linux roots, almost all of it is also free and GPL'd. So while desktop Linux shares the deficiencies of using general purpose OS's for control, there is no longer any need to do so. In addition, the new (2.4) kernel may include "rescheduling points" that have reduced the latencies of regular Linux to below those of NT and in the same neighborhood as Beos. This will make any Linux a good candidate for control with the added hard realtime facilities available when actually needed. And it's not very hard to keep it small enough to run out of flash memory for Hi Rel.
Making a fast ultra reliable Linux PLC all of a sudden got a lot easier.

Regards
 
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