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Old March 16th, 2018, 02:50 AM   #1
cardosocea
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OPC UA Performance experience anyone?

Hello,

I'm looking into getting some S7-1500's PLC's installed and was wondering if anyone has integrated one with OPC UA before and how good is the performance.

In my setup the PLC will be talking to iFix and it seems that I already have the IGS OPC UA driver.
I know that the performance will depend on both parts of the communication link, but was wondering if anyone has had hands on experience with it that can share with me.
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Old March 16th, 2018, 05:11 AM   #2
lfe
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I do not know about iFix and the IGS driver but I know a bit about OPC UA.

OPC UA has the potential to read a set of tags (nodes in OPC UA) even faster than very simple protocols such as Modbus TCP and the advantage is that OPC UA can read the value of hundreds and thousands of mixed nodes in one request.
If the IGS driver uses this possibility, then the performance can be high, if it does not use it, the performance will be lower compared for example to Modbus TCP since OPC UA is a much more complex protocol that adds a certain overload.

But I am fully convinced that OPC UA will be the protocol to be used in the future for the connection to the higher level, its advantages are clear, and the main one for me is the security, certificate authentication and encryption it offers.

To compare performance you can use this Android app, I am the author . It can communicate with Step7, Modbus TCP and OPC UA protocols, and I hope with Ethernet/IP soon.
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Last edited by lfe; March 16th, 2018 at 05:19 AM.
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Old March 16th, 2018, 10:20 AM   #3
mk42
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I don't know anything about the iFix side.

I haven't seen any specific numbers for performance benchmarks for the 1500 OPC UA, but I have heard that you get your best performance by accessing data as a big array or a big data type instead of individual tags. It sounds like most of the overhead is finding the data for a tag, and it takes about the same amount of time whether the tag is a REAL or an array of 100 REALs.

Also, there are apparently 3 different access methods in OPC UA, that the client can choose to use (one time read/write, subscription, registered). I've heard they can have very different performance characteristics, and that many OPC UA drivers in SCADA systems don't have settings that allow the user to optimize for performance or select a method.

The setup in the 1500 is really simple (at least until you turn on security). One check box activated, change a dropdown to say you have your license, (download) and all your HMI accessible tags will now work over OPC UA as well.

Last edited by mk42; March 16th, 2018 at 10:25 AM.
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Old March 16th, 2018, 10:32 AM   #4
cardosocea
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Thanks mk42.

My issue is precisely performance. In my experience with iFix, I would just collect an entire DB in one (or a few) go and then iFix would address from the comms driver memory the signals. Considering that the PLC's sent the data over to the SCADA systems via UDP, there was no requesting of data to be concerned about and we could then just split the data into fast data (machine positions and command feedbacks) and slow data like diagnostics, alarms, etc...

This is where I want to be, but the normal drivers don't seem to be that flexible... I'll see if I can get some more information on the iFix side of things then.
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Old March 16th, 2018, 10:49 AM   #5
lfe
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Precisely OPC UA allows you to read many tags of mixed data types in a single request, which is only possible with other protocols if the data is consecutive and has the same data type.

How the OPC UA server gets these data from the internal memory of the PLC is another question, maybe then it goes faster if the data is all in a row as the array you say.

If for example the OPC UA server was an external server running in a Linux or a Windows PC and had to acquire the data form the PLC by modbus or profinet, then it would be much faster for sure to read the data consecutively like an array.

To connect a PLC with SCADA or HMI, the normal is to use request-response method,
OPC UA also can do publish-subscribe which is more used for I/O on the field bus.
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Old March 16th, 2018, 10:59 AM   #6
Pete.S.
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The S7-1500 will be the the bottleneck when it comes to performance if it's a PC on the other side.

Siemens has a page on their website with OPC performance where you can select different CPUs and different amount of data to request and see how long it will take to service that request. Can't remember the link right now but it's there for sure because I had a look a couple of weeks ago.
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Old March 16th, 2018, 11:24 AM   #7
lfe
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Without having even the PLC, you can connect to demonstration servers with simulated data to make tests, two possibilities:

Install a server on a PC, I recommend the OPC UA ANSI C Demo Server here : https://www.unified-automation.com/d...a-servers.html

or connect to some public OPC UA Servers on the internet, a list here : https://github.com/node-opcua/node-o...-OPCUA-servers
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Old March 16th, 2018, 11:34 AM   #8
mk42
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Quote:
Originally Posted by Pete.S. View Post
The S7-1500 will be the the bottleneck when it comes to performance if it's a PC on the other side.

Siemens has a page on their website with OPC performance where you can select different CPUs and different amount of data to request and see how long it will take to service that request. Can't remember the link right now but it's there for sure because I had a look a couple of weeks ago.
I just went searching for that same thing. Unfortunately, it was using an external OPC Server (Simatic Net) not the internal OPC server of the 1500 (which is what I assume cardosocea wanted). I guess that was just my assumption, though. Here's the link; OPC is the 3rd down:

https://support.industry.siemens.com.../view/25209605
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Old March 16th, 2018, 05:37 PM   #9
Pete.S.
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Quote:
Originally Posted by mk42 View Post
I just went searching for that same thing. Unfortunately, it was using an external OPC Server (Simatic Net) not the internal OPC server of the 1500 (which is what I assume cardosocea wanted). I guess that was just my assumption, though. Here's the link; OPC is the 3rd down:

https://support.industry.siemens.com.../view/25209605

It's a bit confusing but it's actually what the OP is looking for.

What you have is:
OPC server (PLC) -> Simatic Net OPC server (PC) -> OPC client (PC)

If you select "local" the OPC server and the OPC client will be on the same PC. So to move the data from the OPC client to the server will only take microseconds.

The Simatic Net OPC server will be an OPC client when it talks to the S7-1500. All communication will be OPC UA to be correct.

This is the direct link to the interactive website: http://www.automation.siemens.com/pe...ion=32&lang=en
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Old March 18th, 2018, 02:07 PM   #10
cardosocea
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Thanks for the help.
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