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Message ID: 7708     Entry time: Tue Nov 13 21:05:35 2012
Author: Den 
Type: Update 
Category: Adaptive Filtering 
Subject: online and simulation 

For a last few days I've been working on oaf and simulink model to simulate it. First I did online subtraction from MC when MC_L path was enabled. Inside my code I've added a sum of squares of filter coefficients so we can monitor convergence of the filter.

coeff.png     online.png

To to this I've measured path from OAF output to input without AA and AI filters. Then made a vectfit using 2 poles and zeros. Foton command

zpk( [-2.491928e+03;5.650511e-02], [-4.979872e+01;-3.278776e+00], 6.011323e+00)

mag.png    phase.png

My simulink model consists of 3 parts:

  • cavity with seismic noise at low frequencies, 1/f^2 noise at medium frequencies and white noise at high frequencies
  • this cavity is locked using feedback compensation filters that we use to lock arms
  • locked cavity with adaptive filter

Adaptive filter in the model uses online c-code. It is connected to simulink block through an S-function. Sampling frequency of the model is 10 kHz. It works fairly fast - 1 sec of simulation time is computed in 1 sec.

overview.png       af.pngsim.png  sim_coeff.png

I've tested FxLMS algorithm and MFxLMS algorithm that is faster. I plan to test 2 iir adaptive algorithms that are already coded.

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