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Entry  Wed Feb 11 04:08:53 2015, Jenne, Update, LSC, New Locking Paradigm? 
    Reply  Wed Feb 11 22:13:44 2015, Jenne, Update, LSC, New Locking Paradigm - LSC model changes 
       Reply  Thu Feb 12 01:43:09 2015, rana, Update, LSC, New Locking Paradigm - LSC model changes TF.gif
       Reply  Thu Feb 12 11:14:29 2015, Jenne, Update, LSC, New Locking Paradigm - Loop-gebra ALS_REFL_comboLockingCartoon_11Feb2015.PDFALS_REFL_comboLocking_11Feb2015.zip
          Reply  Thu Feb 12 11:59:58 2015, Koji, Update, LSC, New Locking Paradigm - Loop-gebra 
             Reply  Thu Feb 12 19:18:49 2015, Jenne, Update, LSC, New Locking Paradigm - Loop-gebra 
                Reply  Fri Feb 13 03:28:34 2015, rana, Update, LSC, New Locking Paradigm - Loop-gebra 
                   Reply  Sat Feb 14 20:20:24 2015, Jenne, Update, LSC, ALS fool cartoon ALSfool_LoopDiagram.pngALSfool_LoopDiagram.graffle.zip
                      Reply  Tue Feb 17 04:04:32 2015, Jenne, Update, LSC, ALS fool math OpenLoopGainComparison_16Feb2015.pngCancellationTFs_DecouplingIsArefl.png
                         Reply  Tue Feb 17 16:36:08 2015, Jenne, Update, LSC, ALS fool math ALSfool_LoopDiagram_17Feb2015.pngALS_REFL_comboLocking_16Feb2015.nb.zip
       Reply  Thu Feb 12 22:28:16 2015, Jenne, Update, LSC, New Locking Paradigm - LSC model changes, screens modified 
          Reply  Sat Mar 7 19:15:17 2015, Jenne, Update, LSC, Modified zero crossing triggering LatchLogic_6March2015.png
    Reply  Thu Feb 12 03:43:54 2015, ericq, Update, LSC, 3F PRMI at zero ALS CARM Feb12_negativeTR.png
Message ID: 11114     Entry time: Sat Mar 7 19:15:17 2015     In reply to: 11017
Author: Jenne 
Type: Update 
Category: LSC 
Subject: Modified zero crossing triggering 

More work from yesterday. 

Rana and I had discussed on Thursday night that we probably want to be able to use the zero crossing of an error signal to trigger a servo on, but not to un-trigger it.  So, now the zero crossing trigger is latched, using the power trigger to reset the latch. 

Also, the input to the zero crossing trigger is the input to the MC servo, before the triggered switch.  This allows us to look at the normalized error signals rather than just the non-normalized ones, if that's what we're trying to lock on.  This signal is taken before the triggered switch, so that it's looking at whatever is coming out of the input matrix (including normalization).

So.  If the absolute value of the MC error signal goes below the threshold, it outputs a 1, no matter what the arm power is.  If the arm power is high, the power trigger also outputs a 1.  These are AND-ed together, so only if both are 1 do you actually trigger the MC filter bank.  If the zero crossing trigger has been set to 1, it will stay at 1 until the arm power goes low enough to untrigger the power trigger.  So, even if you have a little bit of noise on the error signal and it pops above the threshold momentarily, this won't cause the servo to un-trigger.

This is implemented using a "set-reset latch".  The output of the latch is the zero crossing trigger, which is AND-ed with the power trigger.  This final AND-ing, in addition to doing what we want, solves the ambiguity that is inherent in SR-latches for one combination of inputs. 

The trigger screen has been modified to reflect these model changes.

Here's a screenshot of the model, which includes some notes for anyone who opens the model since it's a bit confusing:

Attachment 1: LatchLogic_6March2015.png  156 kB  | Hide | Hide all
LatchLogic_6March2015.png
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