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Entry  Mon Feb 2 12:24:27 2015, Jenne, Update, ASC, POP QPD centered 
    Reply  Tue Feb 3 04:07:49 2015, Jenne, Update, Modern Control, Measured PRM -> POP QPD TFs PIT_measured_TF.pngYAW_measured_TF.png
Message ID: 10967     Entry time: Tue Feb 3 04:07:49 2015     In reply to: 10963
Author: Jenne 
Type: Update 
Category: Modern Control 
Subject: Measured PRM -> POP QPD TFs 

Today (after centering the POP QPD), I measured the PRM to POP QPD transfer functions.  I am suspicious that this was part of my problem last week.  Since most of the angular noise is coming from the folding mirrors, but I can't actuate on them, I need to know (rather, the Wiener calculator needs to know) how actuating on the PRM will affect the spot at the POP QPD.

For the plots below, I have cut out any data points that have coherence less than 0.95. I may want to go back and fill in a little bit some of the areas (particularly around 3Hz) that I had trouble getting coherence in.

Using these to prefilter my witness data, I am failing to calculate a Wiener filter.  I have tried the Levinson algorithm, as well as brute-forcing it, but I'm too close to singular for either to work.  I am able to calculate a set of Wiener filters without the prefiltering, or with a dummy very simple prefilter, so it's not inherently in the calculators.  Separately, I can plot my vectfit-ed actuator TFs, and I can convert them to a discrete fiilter with the bilinear transform, and then use sosfilt to filter some white noise data, which comes out with the shape I expect.  So.  It's not inherently the filters either.  More work to do, when it's not 4am.

Here are the measured actuator transfer functions.  They were measured as usual with DTT, but since the measurement kept getting interrupted (MC unlock, or I wanted to add more integrations or more cycles), these are several different DTT files stitched together.  In both cases I am acuating PRM's ASC[pit, yaw] EXC point, and looking at the POP QPD.


Attachment 1: PIT_measured_TF.png  105 kB  Uploaded Tue Feb 3 14:00:55 2015  | Hide | Hide all
Attachment 2: YAW_measured_TF.png  107 kB  Uploaded Tue Feb 3 14:01:32 2015  | Hide | Hide all
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