Access Simulink logging data during a simulation run

Is there a way to programatically access Simulink logged data during a simulation run? (i.e before the simulation has completed)

I am fully aware of the Simulation Data Inspector, which is a nice tool for visualising the data, but in this context I would like to have access to the raw data itself to process in some other way (for example, to send via. HTTP request to an external visualisation tool).

I have been unable to find any documentation that indicates this is possible - all documentation seems to assume the simulation has completed or the output datasets already exist. In this case, my simulation runs for several days, and so accessing the data during the run is important for monitoring. The SDI itself clearly has a way to access the data - I wondered if it was possible utilise whatever method it uses?

thanks

Answer 1

[Nathan Hardenberg]

This is possible. The Code below shows a possibility to do this with one signal. Obviously you have to replace 'my_model' and 'my_block' appropriately. When getting the data in the loop you can select the Output-Port.

This is only possible, when the signal is actually selected for logging, otherwise an error is thrown.

% Open the Simulink model
open_system('my_model');

% Get real time block object
rto = get_param('my_model/my_block','RuntimeObject');

% Loop until end of simulation
while ~strcmp(get_param('my_model', 'SimulationStatus'), 'stopped')
    % Get the logged data
    data = rto.OutputPort(1).Data
    
    % Process the data as needed
    % ...
    
    % Wait for a short time before checking again
    pause(0.1);
end

If you also want to automatically log all signals selected for logging, look here. There is the following code shown. With your own adaptation you should be able to extract all logged signals

mdlsignals = find_system(gcs,'FindAll','on','LookUnderMasks','all',...
        'FollowLinks','on','type','line','SegmentType','trunk');
ph = get_param(mdlsignals,'SrcPortHandle')
for i=1: length(ph)
    get_param(ph{i},'datalogging')
end

[William Stokes]

Thanks for this answer, really helpful.

My investigations into this seem to suggest the following

• Blocks must be non-virtual. Selecting the "Treat As Atomic Unit" option was needed to force this, otherwise the get_param call simple returned an empty array.
• If I want to run the model in rapid accelerator mode this runtime object capability appears to not be available.

Do you have any comment on these two points?

Thanks for this suggestion though, has opened up an interesting area to look at.

[Nathan Hardenberg]

Sadly I am not so deep into the topic. For testing I simply used a few basic components where the "Treat as atomic Unit" is not even available.

I also did not know abour rapid accelerator mode before. From googling I found:

"Rapid Accelerator Mode

Rapid accelerator mode creates a rapid accelerator standalone executable from your model. This executable includes the solver and model methods, but it resides outside of MATLAB and Simulink. It uses external mode (see External Mode Communication (Simulink Coder)) to communicate with Simulink." [link]

Since the simulation is extern it seems logical that the implementation may not work. But if the "Simulation Data Inspector" still works there might be another way of getting the data. But as you might guess, I don't know it :D

[William Stokes]

No problem, thank you for your help. I suspected that Rapid Accelerator mode might prove an issue because, as you correctly say, it involves externally compiling the model and so accessing stuff at runtime because more difficult.

Thank you again for your help.