The transfer functions of the IP are shown in Fig 1-3.
Note that the peak at 0.02 Hz is the yaw mode of the suspension chain, which is coupled to many horizontal sensors for some reason.
This mode is ignored during the modeling of the L and T transfer functions.
The modeled transfer functions are installed in FM10 of the DCCTRL filter bank. (Not IDAMP because LVDTs are more robust for coarse alignment.)
All fits are reproducible using notebooks in /kagra/Dropbox/Subsystems/VIS/vis_commissioning/etmy/notebook/transfer_function_fit/.

I proceed to make control filters for the IP. The methodology is similar to that of 19144.
But, due to the complexity of the Type-A suspensions, I decided to manually override the low-pass filters for IP L and T so to guarantee 45 degrees phase margins.
The OLTFs and the filters are shown in Fig. 4-6.
The control filters are decomposed into DAMP and DC filters and they are put in FM3 and FM4 respectively.
All filters are reproducible using notebooks in /kagra/Dropbox/Subsystems/VIS/vis_commissioning/etmy/notebook/control/.