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VIS (EY)
terrence.tsang - 15:25 Wednesday 19 January 2022 (19507) Print this report
ETMY Tower transfer function models

See figures for the fitted transfer functions for the IP, GAS filters, and the BF.
For the BF, I only modeled L, T, and Y DoFs, which are the DoFs that we might want to control.
For IP L and T, they are somehow coupled to the yaw chain mode at 0.023 Hz. I ignored them when modeling the transfer functions.
As usual, GAS filters and BF LVDTs have huge coil2LVDT coupling at higher frequencies (typically above 10 Hz).
These are not modeled. The peaks at higher frequencies, which are physical resonances, are not modeled as well.

The measurements can be found in /kagra/Dropbox/Subsystems/VIS/vis_commissioning/etmy/transfer_function/
The fit can be reproduced at /kagra/Dropbox/Subsystems/VIS/vis_commissioning/etmy/notebook/transfer_function_fit/

The modeled transfer functions are put into FM10 of the control filters. (DCCTRL for the IP, DAMP for others).

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