OPC UA node browsing fails if server contains graphical items

I have been working through the Siemens Application Example “Virtual Commissioning with SIMATIC and Simulink” (link: https://support.industry.siemens.com/cs/ww/en/view/109749187 ) following the guides in documents “109749187_DIGI_Usecases_...” to use PLCSIM Advanced, OPC UA and Simulink as the test environment. Simulink however, is not able to see the contents of global data blocks in the PLC system. By using a third party OPC UA Client i have verified that the items are available from the PLC server. I have attached a report with more details, which was also sent to Siemens support. Their answer is quoted here:

" The problem lays in the implementation of the OPC UA Client within Matlab. As you already found out the browse is not working properly in the matlab client. The reason is the following: With FW2.5 we introduced the Node "icon" under each type (e.g.DataBlockGlobal) which represents a TIA icon (for visualization purpose in the clients). Since this change some clients need to adapt as they did not completely fullfil the OPC UA foundation spezifications. What happens is (simplified) the follwoing: If a Browse is executed on a type node like DataBlocksGlobal you will get the icon and a so called ContinuationPoint. If a ContinuationPoint is not null a BrowseNext has to be executed on this ContinuationPoint to get the additional nodes. This is not done in the OPC UA Client."

Is there any solution to this problem?

[Leonard Classen]

Hello Jakob

I have exactly the same problem!

Did you come up with a solution for that?

Did you find an alternative solution? I do not need to use OPC UA. Currently I am looking into alternative methods to communicate between the PLC and Matlab, eg. TCPIP.

best regards

Leo

[Jakob Rasmussen]

Hi Leo

I skipped the direkt OPC UA connection to the Siemen PLC, and sticked with PLCSIM (not advanced), NetToPLCSIM (third party application for network connection to PLCSIM) and trialversion of KEPServerEx OPC server using only OPC DA. This works with Simulink.

Best regards Jakob

Answer 1

[Stefanie Schwarz]

As pointed out, ContinuationPoints are currently not supported by OPC Toolbox. Our developers are aware of this issue and they are considering to fix this in one of the future releases. As of now, there are no workarounds to handle this.

We apologize for any inconvenience caused due to this limitation.

[Jukka Uotila]

Any ideas when this will be supported by OPC Toolbox?

[Stefanie Schwarz]

This feature is currently not scheduled for a future release.

I encourage every customer who is interested in this feature to submit a Technical Support Request explaining your use case. We will directly forward this to development.

Answer 2

[Felipe Ravazzi Iaconis]

Hello,

Browsing of ContinuationPoints is not supported, but you can still access the variables directly:

So we do actually have a workaround for this. Just download the attachment and replace the file in the application example!

Best regards,

Felipe R.

[Jakob Rasmussen]

Thank you Felipe

[altay engtollykhar]

Hello Felipe,

I've tried your code to construct an OPC node in MatLab, but the node type is unknown, and when I try to retrieve the data it says 'Cannot call readValue on unknown node types.'

The OPC server is working fine, I can read and write through UaExpert.

-------------

code:

Var_Node_In = opcuanode(3,'''OpcInterface''.''fanForce''',uaClient);

result:

I don't know what went wrong.

[Felipe Ravazzi Iaconis]

Hello,

What Matlab and OPC Toolbox versions are you using?

BR

Felipe

[altay engtollykhar]

I'm using MatLab R2016b and OPC Toolbox Version 4.0.2(R2016b).