Run OpenFAST S-Function from Matlab Script

Wind & Water Controls
1

Hello everyone,

I have read different Forum posts but I could not find anything related.

Of course, I have been able to run the OpenFAST S-Function via Simulink model. There is not any problem doing so.

But what I am looking for is to run the S-Function control development capabilities through a Matlab script.

Is it possible to call the S-Function from a Matlab Script without using the Simulink model?

Or using something similar to what it is done in openfast_library.py for Python: openfast/glue-codes/python at main · OpenFAST/openfast · GitHub

Thank you so much in advance!

JL

2

Hi Javier,

You could try this script/repository: ROSCO/runFAST.m at main · NREL/ROSCO · GitHub

It will require updating some paths and maybe a few fixes along the way. We don’t test it as much as the other parts of the repository, but we keep it up there because it’s useful to some folks.

I hope this helps.

Best, Dan

3

Hello Daniel,

Thanks for your quick response!

I will have a look into it.

Best,

JL

4

Hello again,

I have checked carefully the script that Daniel provides here: ROSCO/runFAST.m at main · NREL/ROSCO · GitHub

And it is not what I am looking for. That script runs a complete simulation of a model with ROSCO controller.

Maybe I need to explain myself a little bit clearer.

The main idea is to develop a controller in a matlab script and call OpenFAST as simulation model each time step. In a simple way, I am providing the inputs of the controller to OpenFAST simulation model and I would like to take the states from it to feedback them to my controller.

So, is there any way to call OpenFAST each time step from a Matlab Script?

In Python this can be done after loading the dynamic library and all the functions within it:

Load OpenFAST library:
LoadLibrary(path + ‘/libopenfastlib.dylib’)

Update the states based on the new control inputs:
fast_update(iTurb, NumInputs, InputAry)

I tried this same structure in Matlab but does not work.

I would appreciate if someone have dealed with this before and could provide me some guide how to solve this.

Best,

JL

5

Hi JL,

I think this is essentially what happens within the Simulink S_Function. You can technically call FAST_SFunc from a Matlab script, but I haven’t heard of many people doing it that way. I think you will need to figure out from the OpenFAST source code and/or the Simulink model what the exact inputs to the S_Function are and there are parameters loaded to the S_Function in Simulink. You’ll need to figure out how to reproduce that to get the OpenFAST inputs to the S_Function.

Best, Dan

>> FAST_SFunc(0,0,0,0)

ans =

           0
           0
           0
           0
           0
           0
           0
           3
           0
           0
           0 ...
6

Dear @Javier.Lopez,

There are two examples of Simulink calling OpenFAST v3.3.0 in the repository here: openfast/glue-codes/simulink at v3.3.0 · OpenFAST/openfast · GitHub. Note that this interface does change between versions (typically with additional control channels).

You will need to compile OpenFAST specifically for coupling to Simulink (vs-build/OpenFAST-Simullink for Windows + Visual Studio, or for CMake builds, add the -DBUILD_OPENFAST_SIMULINK_API=On option to the CMake command and build the openfast target).

There is a create_FAST_SFunc.m provided as well for creating the mex function (you will need the appropriate compilers installed that MATLAB can find).

For further information, there are multiple issues posted with hints on getting the compilation and linking to Simulink working here: Issues · OpenFAST/openfast · GitHub

Regards,
Andy

7

Hello,
I’m trying to run the OpenFAST Simulink test case Run_Test01_SIG for validating the S-Function, but I’m encountering errors in both MATLAB and Simulink. Here’s the full error report:
Errors in MATLAB:

Error while obtaining sizes from MEX S-function ‘FAST_SFunc’ in ‘Test01_SIG/FAST Nonlinear Wind Turbine/S-Function’.
Invalid MEX-file ‘C:\Program Files\openfast-3.5.4\openfast-3.5.4\glue-codes\simulink\examples\FAST_SFunc.mexw64’: Le module spécifié est introuvable.
The expression: u(strmatch(‘LSSGagVxa’,OutList)) in ‘Test01_SIG/Fcn’ has a syntax error.

Errors in Simulink:

S-Function Error:Error while obtaining sizes from MEX S-function ‘FAST_SFunc’ in ‘Test01_SIG/FAST Nonlinear Wind Turbine/S-Function’.
Invalid MEX-file:Invalid MEX-file ‘C:\Program Files\openfast-3.5.4\openfast-3.5.4\glue-codes\simulink\examples\FAST_SFunc.mexw64’: Le module spécifié est introuvable.

thank you

8

Dear @Kaouthar.Othmani,

The syntax error regarding LSSGagVxa has been asked and answered on this forum before, e.g., see: problem in running Test03 to Test25. Does that solve the issue?

Best regards,

9

unfortunately no ,
those are the errors in matlab :
slight_smile: Run_Test01_SIG
Error using Run_Test01_SIG (line 36)
Error due to multiple causes.
Caused by:
Error using Run_Test01_SIG (line 36)
Error while obtaining sizes from MEX S-function ‘FAST_SFunc’ in ‘Test01_SIG/FAST Nonlinear Wind Turbine/S-Function’.
Error using Run_Test01_SIG (line 36)
Invalid MEX-file ‘C:\Program Files\openfast-3.5.4\openfast-3.5.4\glue-codes\simulink\examples\FAST_SFunc.mexw64’: Le module spécifié est introuvable.
Error using Run_Test01_SIG (line 36)
The expression: u(strmatch(‘LSSGagVxa’,OutList))
in ‘Test01_SIG/Fcn’
has a syntax error

10

That is the same error you posted earlier. As asked in the forum post I linked to, does ElastoDyn output LSSGagVxa exist in your OutList?

11

how i can know that?

12

Dear @Kaouthar.Othmani,

OutList is an array generated by the OpenFAST S-Function that should be accessible within MATLAB/Simluink. Is LSSGagVxa in this array?

The OutList array is set in the various OutList sections of the OpenFAST input files for each module. LSSGagVxa is an output that could be added within ElastoDyn.

Best regards,

13

Hello everyone,

I’m new to programming, MATLAB, and OpenFAST, and I’m trying to learn how to use them together for a project. Please forgive me if I’m slow in understanding or if my questions seem basic—I’m still at the beginning of this journey!

I’m encountering a few issues and would really appreciate step-by-step guidance:
About OutList I found an Excel file called OutListParameters, and I noticed that the variable LSSGagVxa isn’t listed there. When I try to check for OutList in MATLAB using disp(OutList);, I get the error:
Unrecognized function or variable ‘OutList’.
I also tried running the FAST_SFunc file directly in MATLAB, but I got the following error:
Invalid MEX-file ‘C:\Program Files\openfast-3.5.4\openfast-3.5.4\glue-codes\simulink\examples\FAST_SFunc.mexw64’: Le module spécifié est introuvable.

Could someone kindly explain:
What exactly OutList is and how I can verify its contents?
If LSSGagVxa is not in the OutList, what should I do to include it in OpenFAST?
How to resolve the FAST_SFunc error? Is it a problem with my OpenFAST installation or a missing dependency?

Please keep in mind that I have a limited background in programming, so simpler, more detailed instructions would really help me.

Thank you so much for your patience and support!

Best regards,

14

Dear @Kaouthar.Othmani,

Just a few comments:

  • Each module of OpenFAST has a set of outputs that module generates, as specified in its OutList at the end of the module input file. When the OpenFAST S-Function is executed, all of these OpenFAST outputs are collected in an OutList array available in the MATLAB workspace.
  • LSSGagVxa is an ElastoDyn output and can be found in the ElastoDyn sheet of the OutListParameters.xlsx spreadsheet.
  • If LSSGagVxa is not in the OutList, you can add to the OutList section at the bottom of the ElastoDyn input file.
  • From your errors, it sounds like MATLAB cannot find the OpenFAST S-Function. Does the FAST_SFunc.mexw64 file exist in the C:\Program Files\openfast-3.5.4\openfast-3.5.4\glue-codes\simulink\examples directory you stated?

Best regards,

15

Dear @Jason.Jonkman ,

I have outlined the key problems I encountered:

  1. MEX File Error

    • While running the Run_Test01_SIG script, MATLAB throws an error stating:
      Invalid MEX-file 'C:\Program Files\openfast-3.5.4\glue-codes\simulink\examples\FAST_SFunc.mexw64': Le module spécifié est introuvable.
    • Despite the FAST_SFunc.mexw64 file being present in the expected directory, MATLAB is unable to load it. I suspect the issue may stem from an unresolved dependency or an improper configuration.

  2. Simulink S-Function Error

    • When opening the Simulink model Test01_SIG.mdl, the following error occurs:
      Error while obtaining sizes from MEX S-function 'FAST_SFunc' in 'Test01_SIG/FAST Nonlinear Wind Turbine/S-Function'.
    • This suggests that the Simulink block is unable to correctly access the S-function provided by the FAST_SFunc.mexw64 file.

  3. Output List Error

    • While running the script, there is an issue with the OutList variable used to define certain parameters. Specifically, the script references a parameter named LSSGagVxa, but this is missing from the output list. This mismatch may be causing additional errors in the script execution.

  4. CMake Configuration Errors

    • I attempted to rebuild the FAST_SFunc.mexw64 file using CMake and MinGW, but encountered multiple issues:
      • The matlab_add_mex command in the CMakeLists.txt file is not recognized by CMake, likely due to a missing or misconfigured MATLAB CMake integration module.
      • Running CMake with the command cmake -G "MinGW Makefiles" -S . -B build -DMATLAB_ROOT="C:\Program Files\MATLAB\R2024b" results in the error:
        Unknown CMake command "matlab_add_mex".
      • Attempts to configure and build the project with MinGW or NMake were unsuccessful due to missing project definitions and unresolved dependencies.

  5. MATLAB Compiler Setup Issues

    • Running mex -setup in MATLAB initially indicated that no supported compilers were available. After installing MinGW, I retried but the integration with OpenFAST’s S-function remains unsuccessful.

Given the above issues, I would appreciate guidance to solve those problems.

Best regards,

16

Dear @Kaouthar.Othmani,

I’m not familiar enough with CMake to answer your compiling questions. But I’m doubtful that you should have to recompile the S-Function.

My guess is your first error is triggering the others. For example, if the S-Function is not loading, the OutList variable will not be generated, which will trigger error (3).

Regarding (1), can you clarify–are you running Windows and is your version of MATLAB 64 bit? If so, can you clarify the steps you are using to download and execute the Run_Test01_SIG.m script?

Best regards,