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
Entry  Wed Mar 7 04:08:48 2012, kiwamu, Update, SUS, BS SIDE gain was too low 
    Reply  Wed Mar 14 03:34:44 2012, kiwamu, Update, SUS, Adjustment of BS suspension output matrix : coupling from SIDE to POS Untitled.png
Message ID: 6409     Entry time: Wed Mar 14 03:34:44 2012     In reply to: 6369
Author: kiwamu 
Type: Update 
Category: SUS 
Subject: Adjustment of BS suspension output matrix : coupling from SIDE to POS 

[Rana / Kiwamu]

 We put some elements in the BS output matrix to mitigate the actuator coupling from SIDE to POS.

As a result the degree of the coupling reduced by a factor of 2 or so.

Rana did the "Q of 5" test on the SIDE damping servo after putting the elements and set the gain to be 40.

 

The attached screen shot is the new elements that we put in the suspension output matrix.

Untitled.png

 

(How to)

  • Excite the SIDE motion by AWG at 3 Hz.
  • Monitor the POS signal in DTT
  • Try some numbers in the matrix elements until the peak at 3 Hz in the POS signal is minimized

Quote from #6369

The BS SIDE damping gain seemed too low. The gain had been 5 while the rest of the suspensions had gains of 90-500.

I increased the gain and set it to be 80.

 

I did the "Q of 5" test by kicking the BS SIDE motion to find the right gain value.

However there was a big cross coupling, which was most likely a coupling from the SIDE actuator to the POS motion.

Due to the cross coupling, the Q of 5 test didn't really show a nice ring down time series. I just put a gain of 80 to let the Q value sort of 5.

I think we should diagonalize the out matrices for all the suspensions at some point.

 

ELOG V3.1.3-