Virgo Logbook

AdV-SAT (Suspension control upgrade)

Boschi, Ruggi - 12:44 Thursday 18 April 2019 (45675)

50 Hz FeedForward after calibration

After the calibration shift the integrators used by the feedforward, needed for 50 Hz active removal, that is running on WI mirror DSP, were over-charged. This apparently caused a slow deacrease of the horizon during the night. The FF has been opened, the integrators discharged. The loop is now closed again. To avoid the issue, in the future the FF should opened using the FF_ENBL gname before calibrating.

Comments to this report:

boschi, carbognani - 12:26 Tuesday 23 April 2019 (45705)

In order to avoid those problems related to the 50 Hz FeedForward after calibration, during this morning maintenance the ITF_STATUS automation node has been modified in order to disable this feature during calibration.
So those lines have been added on the main() of CALIBRATION:
# Disable 50Hz feed-forward to avoid overcharging of relevant integrators
WI.FF_ENBL = 0
and those lines added on the main() of TRANSITING:
# Re-enable 50Hz feed-forward disabled during calibration
WI.FF_ENBL = 1

The code has been reloaded on the node without errors and fake transitions in and out of calibration performed. Full testing will be performed at the next real calibration execution.

carbognani - 12:13 Tuesday 07 May 2019 (45838)

> I ask this also because I find it confusing that ITF_STATUS may change the machine configuration, given also the fact that the TRANSITING state may be reached in a multitude of ways and it may not be straightforward to avoid all corner cases (see Graph).

This is a relevant remark.

We have removed the lines added into ITF_STATUS for this purpose waiting for a deeper analysis of the functionality we want to implement. For sure it is better that ITF_STATUS node doesn't change anything on the ITF configuration.