Dear Hadi,
The approach you describe all sounds correct.
Regarding your questions:
- The AD user property inputs (UserProp) are standard inputs that can be ignored if not needed. See a related issue on the OpenFAST github page: github.com/OpenFAST/openfast/issues/778.
- I would suggest plotting the azimuth variation of the MBC-transformed A matrix (etc.) to see the periodicity in the signal (before azimuth averaging). It could be that the average is not exactly zero due to numerical round off, but they are likely much small than other dominant terms in the MBC-transformed A matrix. If you are not understanding the linearization output, I would always suggest simplifying the model to debug, e.g., does the result make more sense when you only have one DOF enabled (GenDOF = True; all others DOFs False)?
- Perhaps you’ve applied the inverse MBC transformation incorrectly for the flapwise bending moment? Do other outputs make more sense, e.g., blade flapwise deflection (requires inverse MBC transform), rotor thrust, tower-top deflection, and tower-base moment (the latter three do not require the inverse MBC transform)?
Best regards,