Beckhoff IPC Hot Redundancy

ngch · Feb 26, 2020

Hi all gurus! I'm a newbie in automation field, hope to learn from all of you.

Let's go straight to the point.

Currently, I'm implementing automation system using Beckhoff product.
There is an application which required "hot redundancy system".

What I wish to achieve:
1) Two IPCs sharing only one EtherCAT Bus Coupler with IO cards.
2) If the primary controller fails, the backup one should immediately assume control.

I'd contacted my local Beckhoff tech support team for advice.
What they told me is Beckhoff don't support hardware redundancy.
Which I find it unbelievable! Because all other brand have this feature.

Did anyone try to implement something similar using Beckhoff before?
Wish to know is there any possibility to achieve that.
Any input would be appreciated! Thanks in advance!

mad4x4 · Feb 26, 2020

ngch said:
Hi all gurus! I'm a newbie in automation field, hope to learn from all of you.

Let's go straight to the point.

Currently, I'm implementing automation system using Beckhoff product.
There is an application which required "hot redundancy system".

What I wish to achieve:
1) Two IPCs sharing only one EtherCAT Bus Coupler with IO cards.
2) If the primary controller fails, the backup one should immediately assume control.

I'd contacted my local Beckhoff tech support team for advice.
What they told me is Beckhoff don't support hardware redundancy.
Which I find it unbelievable! Because all other brand have this feature.

Did anyone try to implement something similar using Beckhoff before?
Wish to know is there any possibility to achieve that.
Any input would be appreciated! Thanks in advance!

You can do cable redundancy on beckhoff but the MTFB on the CPU and is high. What is your application that requires redundancy at CPU level and why did you opt for the beckhoff platform.

If cpu redundancy is so important I would have thought you would have researched the suitablitity of the controller before purchasing.

ngch · Feb 26, 2020

Hi mad4x4, firstly, thanks for your input!

The company that I working now have been using Beckhoff platform since day one, many things had built on top of it, so I don't really have the freedom to switch platform.

Actually I'm designing a plant-wide automation system.
In short, one Master IPC will control & talks to several sub-station IPCs.
Client request us to include some extent of redundancy, in order to reduce the risk of complete failure.

So I'm exploring the possibilities, I'm considering to implement CPU level Redundancy at Master IPC side & those sub-stations that control critical process.

"Cable Redundancy" is not equal to "CPU Level Redundancy" right?
If I'm not mistaken, cable redundancy just make sure there is another path of data transfer, in case 1 of the data comm cable breakdown.
Is that correct?

mad4x4 · Feb 26, 2020

Cable redundancy is the equivalent of a ring network to make sure all nodes stay on the network .

For your description you have say 5 Machines all running beckhoff and you want to put in a high level system above this talking to the 5 beckhoff machines, and at this level you want redundancy. THis supervisory system is this to be implemeted on Beckhoff visualization or in a SCADA ( Deltav, Wonderware, ect)

So does the Master IPC have to be beckhoff? Beckhoff will talk to anything so put in a pair of Rockwell or Siemens redundant CPU's if the customer want redundancy so bad. Or consider having 2 x SCADA severs set as redundant talking to a single beckhoff machine (data aggregator) on cable redundancy talking to the 5 critical machines.

The whole point of redundancy is to eliminated failure so work out what is the most likely cause of failure and fix that.

mad4x4 · Feb 26, 2020

Try speaking to Beckhoff UK, they should be able to help you design the best system

Andy

AustralIan · Feb 26, 2020

The upstream feature you want is:
https://www.codesys.com/products/codesys-runtime/redundancy-toolkit.html
You could ask beckhoff how much to implement this feature specially for you..
Maybe your team will accept another CODESYS manufacturers controller, interfacing with the Beckhoff Ethercat Bus Coupler?
Also possible would be to ask CODESYS if they can sell you a variant of "CODESYS Control RTE SL (for Beckhoff CX)" or if you're not using the CX, "CODESYS Control RTE SL", with the redundancy component added. Again, your team would need to accept the different programming environment.

Iman · Feb 27, 2020

ngch said:
Hi all gurus! I'm a newbie in automation field, hope to learn from all of you.

Let's go straight to the point.

Currently, I'm implementing automation system using Beckhoff product.
There is an application which required "hot redundancy system".

What I wish to achieve:
1) Two IPCs sharing only one EtherCAT Bus Coupler with IO cards.
2) If the primary controller fails, the backup one should immediately assume control.

I'd contacted my local Beckhoff tech support team for advice.
What they told me is Beckhoff don't support hardware redundancy.
Which I find it unbelievable! Because all other brand have this feature.

Did anyone try to implement something similar using Beckhoff before?
Wish to know is there any possibility to achieve that.
Any input would be appreciated! Thanks in advance!

Beckhoff doesn't support hardware redundancy, but software redundancy is possible. However, the switching time isn't as fast as the hardware redundancy. But there is another problem. since EtherCAT network is used as IO you cannot use this IO network to provide the redundancy in CPU level because in EtherCAT network there is no possibility to have two masters at the same time. I would say, if you must provide redundancy with BECKHOFF you should change the fieldbus network to network such as Profibus that supports two master and also implement software redundancy in CPU level.

ngch · Feb 27, 2020

Iman said:
Beckhoff doesn't support hardware redundancy, but software redundancy is possible. However, the switching time isn't as fast as the hardware redundancy. But there is another problem. since EtherCAT network is used as IO you cannot use this IO network to provide the redundancy in CPU level because in EtherCAT network there is no possibility to have two masters at the same time. I would say, if you must provide redundancy with BECKHOFF you should change the fieldbus network to network such as Profibus that supports two master and also implement software redundancy in CPU level.

Hi Iman, thanks for your sharing!
I never know EtherCAT network cannot have 2 masters (another limitation,sigh).

Can you share more on how to implement "software redundancy"?
How does "software redundancy" work?
Beckhoff got provide any library to achieve that?

(Assuming I can change fieldbus network to other type)

Iman · Feb 27, 2020

Hi ngch,
In software redundancy, you should manage the switch over between CPUs by yourself and there is no library to do this procedure.
However, in case of Profibus network, main transfer procedure is done by profibus master cards such as FC3101. But in your logic, for error management and monitoring the system you should write your own code. You can find more information here in Beckhoff website.
Since in Beckhoff there is no backplane,you won't have hardware redundancy. As far as I know, the only difference between software and hardware redundancy is transfer time.

RocketTester · Apr 17, 2020

In my experience, the Beckhoff processor doesn't know the difference if you swap to an exact same set of I/O modules for which it is configured, as long as they have the same "process image" (same byte stream on EtherCAT). Perhaps you could have 2 CPU's configured for the same I/O and running the same PLC code, but only 1 connected to the I/O via an Ethernet cable. Swap-over would be done by switching the Ethernet cable, either manually or by an automatic switch triggered by a sensor. The PLC code can be written so that when disconnected, the backup CPU knows that (I/O status codes) and its code sits in an idle loop, awaiting valid I/O.

Perhaps the highest way to sense a problem is to use the old K-bus "watchdog timer" module (KL3692 recall). The PLC code needs to poke a variable in it every ~100 msec to keep relays latched. If it loses that poke, the mechanical relays trip, which would then make the Ethernet cable switch. You can integrate that module in an E-bus system w/ and inline adapter (EK1250 recall). We have done that because an engineer wanted to insure we respond to a problem in PLC code too, in addition to problems in the I/O stream. Poking the watchdog is the last line in the code, so if it hangs before that, or doesn't get there due to overloading the CPU, the watchdog trips. Never done all this, but "should work".

ngch · Apr 17, 2020

RocketTester said:
In my experience, the Beckhoff processor doesn't know the difference if you swap to an exact same set of I/O modules for which it is configured, as long as they have the same "process image" (same byte stream on EtherCAT). Perhaps you could have 2 CPU's configured for the same I/O and running the same PLC code, but only 1 connected to the I/O via an Ethernet cable. Swap-over would be done by switching the Ethernet cable, either manually or by an automatic switch triggered by a sensor. The PLC code can be written so that when disconnected, the backup CPU knows that (I/O status codes) and its code sits in an idle loop, awaiting valid I/O.

Perhaps the highest way to sense a problem is to use the old K-bus "watchdog timer" module (KL3692 recall). The PLC code needs to poke a variable in it every ~100 msec to keep relays latched. If it loses that poke, the mechanical relays trip, which would then make the Ethernet cable switch. You can integrate that module in an E-bus system w/ and inline adapter (EK1250 recall). We have done that because an engineer wanted to insure we respond to a problem in PLC code too, in addition to problems in the I/O stream. Poking the watchdog is the last line in the code, so if it hangs before that, or doesn't get there due to overloading the CPU, the watchdog trips. Never done all this, but "should work".

Hi RocketTester, thanks for your suggestion!
The idea of switching Ethernet cable looks promising to me, I never thought of that!

Does anyone know any ready-built device that can switch Ethernet cable connection?

Maybe something like a Network switch with Digital Input Trigger?
If DI = logic 1, forward Ethernet connection to Port 1;
If DI = logic 0, forward Ethernet connection to Port 2;

Any relevant info is welcome!
Thank you!

fran007 · Jul 17, 2020

ngch said:
Hi RocketTester, thanks for your suggestion!
The idea of switching Ethernet cable looks promising to me, I never thought of that!

Does anyone know any ready-built device that can switch Ethernet cable connection?

Maybe something like a Network switch with Digital Input Trigger?
If DI = logic 1, forward Ethernet connection to Port 1;
If DI = logic 0, forward Ethernet connection to Port 2;

Any relevant info is welcome!
Thank you!

Did you found any Network switch with Digital Input Trigger?

Somebody with any similar solution?

Thank You!

Beckhoff IPC Hot Redundancy

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ngch

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