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Entry  Sat Nov 12 03:46:55 2011, Suresh, Update, IOO, MC WFS Servo: Open loop gain  WFS1_PIT_servo_filtershape_20111111_1.pngWFS1_PIT_servo_OLG_20111111_1.pngError_signal_WFS1_PIT_20111111_1.png
    Reply  Sat Nov 12 08:09:47 2011, rana, Update, IOO, MC WFS Servo: Open loop gain  
       Reply  Tue Nov 15 01:44:36 2011, Suresh, Update, IOO, MC WFS Servo: Open loop gain  WFS1PIT_OL_gain.png
Message ID: 5892     Entry time: Tue Nov 15 01:44:36 2011     In reply to: 5884
Author: Suresh 
Type: Update 
Category: IOO 
Subject: MC WFS Servo: Open loop gain  

Quote:

Somehow, I generically don't like the idea of lead filters for the WFS loops. We don't really need so much bandwidth. I think you should include with the servo measurements, a servo model ( on the same plot ) that matches the loop shape.

For example, this means including the 28 Hz ELP in the MC1/3 hardware and MC2 ASCPIT/YAW digital filter banks. BY comparing the model v. measurement we can determine if the cross-coupling due to imperfect output matrix is very serious or not.

In the measurements, the loop with the most low frequency gain looks the most promising.

WFS1_PIT servo replotted with foton data overlaid:

I included the following filters in foton:

1) Integrator: zpk([0.8],[0],0.8,"n")

2) zpk([0.8],[100,100],1,"n")

3) zpk([1:10],[3,30],1,"n")

4) ELP28

I have unwound the phase by adding or subtracting 180 to portions of the phase data.

And here is the plot for WFS1_PIT.  I will repeat this process for the other three WFS loops tomorrow.

WFS1PIT_OL_gain.png

 

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