40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  40m Log  Not logged in ELOG logo
Message ID: 4646     Entry time: Thu May 5 17:19:21 2011
Author: Leo Singer 
Type: Configuration 
Category: SUS 
Subject: Tuning notch filters for bounce mode suspensions 

I am tuning the notch filters for the bounce modes in the suspensions, starting with the ITMs and ETMs.  I'll do the MCs, the PRMs, and the SRMs next.

 

I noticed that the filter for ITMX (in the file C1SUS.txt, the module ITMX_SUSPOS, the selection BounceRoll) that the filter was composed of two bandstops (and a constant gain).  It looked like this:

 

ellip("BandStop",4,1,40,11.4,12.2)ellip("BandStop",4,1,40,16.7,17.5)gain(1.25872)

 

Valera said that one of these was for the roll mode and the other for the bounce mode.  However, looking at the spectra that Kiwamu and I made this week, I don't perceive a resonance between 11.4 and 12.2 Hz.  So, we're taking a guess that this was for a mode that has moved due to new pendulum designs.  For many of the suspensions, in the free swinging test we noticed a line around 23 Hz; we thought we might as well re-use one of these elliptical filters to avoid exciting this line.  Of course, if this line does *not* result from excitation of an uncontrolled degree of freedom, this will not help and could be detrimental.  When we talk to Valera again, we can review this decision and at that point we might decide just to take out that bandstop.

 

ITMX is done.  I'll continue tomorrow.  I've attached closed-loop spectra for before the tuning (itmx-before.pdf) and after (itmx-after.pdf).

 

(Update: the following day, I took closed loop spectra with (itmx-withbounceroll.pdf) and without (itmx-nobounceroll.pdf) the bandstops.  It looks like the bandstops made the bounce mode slightly worse, but the roll mode slightly better.)

 

 

Attachment 1: itmx-before.pdf  7 kB  Uploaded Fri May 6 14:53:45 2011  | Hide | Hide all
itmx-before.pdf
Attachment 2: itmx-before.pdf  7 kB  Uploaded Fri May 6 14:53:54 2011  | Hide | Hide all
itmx-before.pdf
Attachment 3: itmx-withbounceroll.pdf  7 kB  Uploaded Fri May 6 15:14:15 2011  | Hide | Hide all
itmx-withbounceroll.pdf
Attachment 4: timx-nobounceroll.pdf  6 kB  Uploaded Fri May 6 15:14:24 2011  | Hide | Hide all
timx-nobounceroll.pdf
ELOG V3.1.3-