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Dear @HiHoGit, Tower-top acceleration is an output from, not an an input to, OpenFAST. So, "no", such functionality is not directly available in OpenFAST. That said, others have modified OpenFAST to input motion instead of loads (e.g., see: #617, #795). Moreover, other work has used OpenFAST to generate a digital twin that can be used to take measurements and reconstruct other responses that are not measured directly (e.g., see: https://www.nrel.gov/docs/fy20osti/76854.pdf). Best regard, |
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Thank you @jjonkman for the answer. I had a look at the paper and I have a couple of questions. |
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Ok, Thank you for the clarification. Kind regards, |
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Dear @jjonkman, I have a question about OpenFAST linearization and using state-space matrices through a Kalman filter to estimate certain qualities. My governing equation is the simple tower first-order dynamic where I have the tower top fore-aft (FA) acceleration as a measurement (y = Cx + Du + w), and the thrust estimated by a Look-Up Table (LUT) (x' = Ax + Bu + v) as an input. I am attempting to estimate tower states and the tower base bending moment (z = Ex + Fu). Here's what I've done: Initially, I performed linearization for a 2-degree-of-freedom (2DOF) system, obtained the ABCD matrices, and conducted the estimation. In a second approach, I introduced additional degrees of freedom (DOFs) for the tower and blades but kept the tower motion equation the same (2-DOF). I only utilized the associated values of tower stiffness and damping, eliminating other values in the matrices. Following the same procedure and conditions, I observed that the estimation error of the tower top deflection did not change significantly (possibly due to consistent measurement and input). However, the estimation error of the tower base bending moment showed significant improvement. I would appreciate it if you could provide any insight or explanation for this observation. I am somewhat concerned as I am unable to mathematically justify why I can eliminate certain values in the ABCD matrices and only consider what is necessary for the tower FA, even when the linearization is performed using 9DOF! Thank you! |
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Dear @ebranlard, I have a question about OpenFAST linearization and using state-space matrices through a Kalman filter to estimate certain qualities. My governing equation is the simple tower first-order dynamic where I have the tower top fore-aft (FA) acceleration as a measurement (y = Cx + Du + w), and the thrust estimated by a Look-Up Table (LUT) (x' = Ax + Bu + v) as an input. I am attempting to estimate tower states and the tower base bending moment (z = Ex + Fu). Here's what I've done: Initially, I performed linearization for a 2-degree-of-freedom (2DOF) system, obtained the ABCD matrices, and conducted the estimation. In a second approach, I introduced additional degrees of freedom (DOFs) for the tower and blades but kept the tower motion equation the same (2-DOF). I only utilized the associated values of tower stiffness and damping, eliminating other values in the matrices. Following the same procedure and conditions, I observed that the estimation error of the tower top deflection did not change significantly (possibly due to consistent measurement and input). However, the estimation error of the tower base bending moment showed significant improvement. I would appreciate it if you could provide any insight or explanation for this observation. I am somewhat concerned as I am unable to mathematically justify why I can eliminate certain values in the ABCD matrices (possibly due to the inclusion of thrust as an input) and only consider what is necessary for the tower FA, even when the linearization is performed using 9DOF! Thank you! |
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Dear all,
I need to run a fully nonlinear version of OpenFAST as a function in order to get some outputs when I have some others depending on conditions. for example, when I have tower top acceleration, be able to calculate or estimate the deflection or shape function. Does OpenFAST have such a possibility?
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