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Entry  Mon Mar 10 21:14:58 2014, ericq, Summary, LSC, Composite Error Signal for ARms (3) model.pngsimSweep.pdfalsSweep.pdf
    Reply  Wed Mar 26 11:16:59 2014, ericq, Summary, LSC, Composite Error Signal for ARms (3) simlink.pdfsimulatedCESARLock.pdf
Message ID: 9751     Entry time: Wed Mar 26 11:16:59 2014     In reply to: 9710
Author: ericq 
Type: Summary 
Category: LSC 
Subject: Composite Error Signal for ARms (3) 

Extending the previous model, I've closed a rudimentary CESAR loop in simulink. Error signals with varying noise levels are combined to bring a "cavity" to lock.  

simlink.pdf

There are many things that are flat out arbitrary at this point, but it qualitatively works. The main components of this model are:

  • The "Plant": A pendulum with f0 = 2Hz, Q = 10
  • Some white force noise, low passed at 1Hz before input to the plant.
  • The Controller: A very rough servo design that is stable...
  • ALS signal: Infinite range Linear signal, with a bunch of noise
  • Transmission and PDH signals are computed with some compiled C code containing analytic functions (which can be a total pain to get working), have less noise than ALS
  • Some logic for computing linearized PDH and SqrtInv signals
  • A C code block for doing the CESAR mixing, and feeding to the servo

And it can lock! 

simulatedCESARLock.pdf

 

Right now, all of the functions and noise levels are similar to the previous simulation, and therefore don't tell us anything about anything real...

However, at this point, I can tune the parameters and noise levels to make it more like our interferometer, and thus maybe actually useful. 

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