camilla.compton@LIGO.ORG - posted 12:03, Tuesday 04 February 2020 - last comment - 09:20, Friday 07 February 2020(54887)
Recent FSS oscillating cases hopefully reduced
Jason, Sheila, Camilla
In an effort to speed up the FSS relocking, we have edited the PSL_FSS node to wait for the FSS to be resonant before checking if the FSS is oscillating.
This is because, during FSS_OSCILLATING(#-10) state, we saw the temperature controller seemingly pulling the FSS off resonance in an effort to stop it oscillating and then repeating this, see image taken after a recent lockloss. We hope that by waiting for the FSS to be resonant before allowing PSL_FSS to enter the FSS_OSCILLATING state, we shouldn't get stuck in the state. Testing showed quicker locking, see after image where the gain is not changed until FSS is resonant.
Niko should accept the H1:PSL-FSS_TEMP_MANUAL= 0.35 SDF diff, this is just locking set point we changed in testing and shouldn't make any difference to locking.
Images attached to this report
Comments related to this report
It seems that this change didn't help at all during relocking from a fresh lockloss. Both Patrick and Jeff had to toggle the autolocker last night to stop the FSS oscillating (alog 54914 and 54916).
I don't think the change has made anything worse so shouldn't need to be reverted. A new fix will need more thought, maybe the GRD toggling the autolocker (band aid solution) or checking the autolocker code to see what it is doing.
Tagging PSL for future reference/search.