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Entry  Mon Sep 12 20:15:22 2016, Lydia, Update, SUS, Diagonalization in air ITMY_fit.jpgBS_diag.jpg
    Reply  Tue Sep 13 19:18:43 2016, Lydia, Update, SUS, Diagonalization in air ITMY_diag.jpg38.png
       Reply  Wed Sep 14 20:27:03 2016, Lydia, Update, SUS, Diagonalization ETMY_diag.png
          Reply  Thu Sep 15 18:37:20 2016, Lydia, Update, SUS, Diagonalization ETMY_osemspec.pngITMY_osemspec.png
             Reply  Fri Sep 16 19:14:27 2016, Lydia, Update, SUS, Diagonalization ETMY_yawdrivedefault.pngETMY_yawdrivenew.pngETMY_yawdriveold.png57.png
Message ID: 12497     Entry time: Thu Sep 15 18:37:20 2016     In reply to: 12495     Reply to this: 12499
Author: Lydia 
Type: Update 
Category: SUS 
Subject: Diagonalization 

[Teng, Lydia]

  • We fixed the 60Hz filter on ITMY. This improved the phase problems somewhat but one coil (UL) is still about 12 degrees out of phase compared to the others for all the dofs. Is there some other place where a filter coule be applied to just one coil sensor? I pressed the "Load coefficients" button for UL, so maybe that will have helped.
  • We want to interpret the coil signals to have an accurate measurement of each dof. This means what the input matrix should describe is the dependence of each dof on the OSEM signals, which is found by inverting the matrix which describes the sensitivity of each OSEM to changes in that degree of freedom.
    • We looked at the spectra of the individual coils for ITMY and ETMY (See attachment 1 & 2). The coupling between some coils and applicable resonance peaks is very weak (~0.1 times the sensitivity of the other coils).
    • However, when a certain degree of freedom, e.g. pitch, is deliberately driven using awggui, the response of the ITMY coils is clear on the StripTool and is about the same magnitude for all of the face OSEMS. So, it seems like the diagonalization script does not always succeed at measuring the relative sensitivity of the OSEMs to the degrees of freedom.
    • This may be because the fundamental swing modes experienced by the free swinging pendulum are not the same as what we measure as pitch, yaw, etc. This could be possible if the wire tension is not the same on both sides. For ITMY, the spectra imply that the funamdental frequencies are actually at some linear combinations of pitch and yaw, swinging about a diagonal axis that results in a much weaker response for some of the OSEMS. Calling these peaks pitch and yaw may be inaccurate. Certainly they do not indicate the true relative sensitivity of the coils.
    • We propose an alternate approach to measuring this sensitivity: drive one dof at a time with awggui, take a spectrum (less resolution is ok because we already know the drive frequency), and measure the sensing matrix values for that dof the same way as before, but using a spectral peak that decribes motion that we know is purely pitch. Repeat this for all 4 dofs that we can actuate on, then compile these results into a sensing matrix and take the inverse.
Attachment 1: ETMY_osemspec.png  31 kB  | Hide | Hide all
Attachment 2: ITMY_osemspec.png  26 kB  | Hide | Hide all
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