While Travis was working on initial alignment earlier today, we found that we were once again having trouble turning on the ASC for the X green arm.  I think the trouble was that the DC centering loops' error signals (from the green ITMX camera) were a little bit too large.  This isn't something that happens too often, but it definitely caused the ASC to pull the arm away from resonance.  Engaging the ASC without the DC centering was fine, so it's definitely something with that pair of loops.

By hand, I turned the gain on the DOF 3 loop for both pitch and yaw (which handles the DC centering) to half of the nominal value.  Once the error signals were closer, I put the gain back up at the nominal value for both loops.

Since this is a particularly tricky problem to troubleshoot, I've tried to handle it in the ALS Arm guardians. The modifications were made in the "generator" states, so they are the same for each arm.  The actual gain values for each arm are stored in the alsconst.py file, which is already loaded by the generator states. 

• In the ENABLE_WFS state, if the DOF3 error signal is large for either pitch or yaw, it'll turn the gains for DOF3 on to half of nominal.  If the error signal is not too large, carry on as usual, with the nominal gain.
• In the LOCKED_W_SLOW_FEEDBACK state, if the gain is not at its nominal value (i.e., it has been turned on at half of nominal), it will wait in the run state until the DOF3 error signals are small-ish, then it will ramp the gain up to the nominal value, and allow the guardian to continue.

I have loaded this new code, but it has not been fully tested, since we have not done initial alignment since I loaded it (and that's where it'll get used).  I've tried to test the logic in the guardian shell and that all seems to be fine, but there's no test like doing it live.  If it is giving errors that seem insurmountable, I did an svn checkin of the as-found code before I started modifying it (as well as another checkin after my edits), so we can go back one svn version.