J. Kissel

Hugh and Corey have unlocked, balanced, floated, and damped the HAM6 ISI LHO aLOG 41031, so I wanted to see if I could get new, more coherent TFs of the OPOS to better understand if the problems we're seeing are dynamics (rubbing, bad physical parameters, unmodelled but physical cross-coupling), electronics, basis issues, or something else.

The TFs are more coherent (I've also used the same drive filtering and amplitudes used to get the beautifully clean LLO aLOG 37508), but they're still confusing.

The encouraging news: now that I account for
    - The updated dynamical model, as discussed in LHO aLOG 41032
    - The change in transconductance between a v2 and v3 HAM-A driver (I had mistakenly used the -v3 transconductance, which was a factor 10 weaker)
    - The understood-but-not-yet-fixed, factor of 1e-6, unit flaw in the lever arm calculation in L1's OSEM2EUL and EUL2OSEM matrices
the DC scale of all DOFs in L1's TFs line up with the dynamical model exquisitely, and *at least one* of the DOFs of H1's data also line up. 

Also -- a lot of the (apparently incoherent) features in the H1 OPO's 2018-02-27 data that I was trying to explain with dynamics have gone away with the improved drive templates and the unlocking of the ISI.
Now, the response features and shape in L2L, V2V, P2P, and R2R (aside from scale factor issues) TFs look quite similar between L1 and H1.

Progress!

What remains as strange and/or a problem:
    - 5 of 6 H1 DOFs still don't match the DC scale factor of the dynamical model.
    - There remains a good deal of Yaw to Transverse coupling in T2T.
    - Also in T2T -- there's very little actual of the primary transverse model
    - The high-frequency asymptote in P2P seems to have drastically changed. It's unclear if this is dynamical interaction between the floating ISI and the floating OPOS, or if, for some strange reason the well-known electrical cross-coupling between drive and sensor has changed. Comparing pg 17 of 2018-03-16_1652_H1SUSOPO_M1_ALL_TFs.pdf and 2018-02-27_2209_H1SUSOPO_M1_ALL_TFs.pdf, one sees that the source of the change is mostly do to a change in V2's response.

However, now that we understand the DC gain of these transfer functions better, I'll take a look at the damping loops again and check if I can get somewhere by adjusting their gain to match the better understood plant.