J. Kissel, [Corroborated by J. Wright and J. Driggers]
WP 11797
While upgrading the OMCS_MASTER.mdl library part for the OMC Suspension (which now lives in the h1susifoout.mdl top-level model), I found two distressing things:
(1) The OMC ASC signals that are sent from the h1omc.mdl model -- running at 2kHz -- are not anti-imaged at all before being sent to the OMC SUS DAC -- running at 16 kHz. So, we're sending unnecessary imaging noise to the SUS DAC.
(2) The OMC ASC L, P, amd Y signals are being sent through a filter bank that does NOT past through the DRIVEALIN matrix, rendering 2019's attempt at diagonalization (LHO:47488) unused.
These bugs have been long standing.
I see it now as I touch the h1susifoout.mdl and the OMCS_MASTER library part for watchdog upgrades, but I'd previously identified the issue when
- I was upgrading the front-end models for O4 (i.e. when the OMC SUS transitioned from the h1susomc.mdl to the h1susifoout.mdl) in 2021 (LHO:59652), and
- When we were identifying which SUS models used the broken "TrueRMS" bloick -- there's a preceding note in the simulink model that suggests this has been around since 2015 or earlier.
We can fix this tomorrow, with *only* a change to the h1susifoout.mdl and OMCS_MASTER.mdl models, and we're already doing that anyways for the SUS watchdog upgrade.
Attached are several series of screenshots showing:
(1) The signal path from the h1omc.mdl model where the OMC ASC control signals begin, to where they land in the OMC SUS driving in the EULER basis (again WITHOUT going through the DRIVEALIGN MATRIX)
(2) MEDM Screens showing that in practice we only drive L, P, and Y (as one should for an ASC signal) and we don't use T, V, or R drive and likely never will.
(3) The existing filters that will need to be copied over, and the DRIVEALIGN gain values that will likely need to be re-addressed -- since effectively we've NOT been using them.
Note -- I checked on how this is done at LLO, and they *do* drive through the LOCK banks and DRIVALIGN banks (BUT they don't have any anti-imaging filters in pace either, even though their ISCINF FM1 banks are ON... whoops)...
So, when we change the OMCS_MASTER library part, this won't affect them.