The use of TMD and TLCD in openfast

[sffgd]

Hello everyone，
I encountered some issues when using the StC_test_OC4Semi case file （https://github.com/OpenFAST/r-test/tree/main/glue-codes/openfast/StC_test_OC4Semi）:
This test case illustrates four different Stuctural Controls in use. There are 4 Stc positions：1. StC at blades 2.StC at nacelle 3.StC at tower 4. StC at substructure

Q1：I am using OC3 spar dll as the controller and v3.0 of the openfast_x64.exe file. I am not sure if this is correct. Can Stc be enabled? (I can provide the running file if necessary.)

Q2：Does StC_DOF_MODE=1/2 indicate TMD? When I want to call TLCD, I select StC_DOF_MODE=3？

Q3：The contents of these four Stc input files are very similar. How should I set ‘StC_P_X’, ‘StC_P_Y’ and “StC_P_Z” in ‘StC LOCATION’ in different input files? and which position does the ‘reference origin’ in ‘relative to the reference origin of component attached to’ represent in the four control measures?

Q4：I would like to know“ StC_X_KS - Stop spring stiffness in the X direction (N/m)
0 StC_Y_KS - Stop spring stiffness in the Y direction (N/m)
0 StC_Z_KS - Stop spring stiffness in the Z direction (N/m) [Used only when StC_DOF_MODE=1 and StC_Z_DOF=TRUE]
0 StC_X_CS - Stop spring damping in the X direction (N/(m/s))
0 StC_Y_CS - Stop spring Y-direction damping (N/(m/s))
0 StC_Z_CS” When would these be used? Can I set all of them to 0?

Q5：I would like to know if the fourth control method, ‘StC at substructure: Two vertical StCs located at (0,0,0) and (14,25,0),’ involves placing the TMD on a floating platform.

Best regard！

[jjonkman]

Dear @sffgd,

Here are my responses:

1. Yes, the Structural Control (StC) submodel of ServoDyn is available in OpenFAST v3. But I would also suggest upgrading to the newest version of OpenFAST (currently v4.1.1), unless you have a strong reason to use older versions of the software.
2. Yes, StC_DOF_MODE switch between TMDs (1, 2), TLCD (3), and user-specified loads (4, 5)
3. The origin of the StC at-rest locations depend on which component the StC is placed, i.e., at the blade root for blade-based STCs, at the yaw bearing for nacelle-based StCs, at the tower base for tower-based StCs and at the platform reference point for substructure-based StCs.
4. The stop-spring stiffness is a user-defined value.
5. In this example, there are two vertical-oriented TMDs at different vertical locations in the substructure.

Best regards,