Shane AO  

Problem: ShaneAO WFS Steering Motor 2 Ry - Uninstalled during 2019/2020 WFS mechanism upgrade

Manifestation:

• In Shane AO motor control GUI, WFS steer 2 Ry indicates red cross.
• Moves fine in the positive direction, but has trouble in the negative direction, giving off-on-errors almost immediately when near the forward limit, or fails to move in negative direction.

Solution/Recovery:

• Much of this issue seems to have been mitigated by the introduction of a regular WFS Steering Mirrors Maintenance Procedure.
• In Shane AO motor control GUI:
  • open detail view panel for affected motor.
  • Set mode to Pos
  • Set relative move to -30000. Stage should move.
  • Allow stage to move away from stuck position.
  • When moving stage, endeavour to NOT drive into a limit. If in a limit, set speed to 200 and allow stage to move out of limit. When out of limit, set speed to 0.
  • Set mode to Pos
• In fieldsteer GUI:
  • Ensure Move Telescope and Auto Close Loops are NOT selected.
  • Ensure Telescope Move value is (re-)set to 0.
  • Apply a Telescope Move (in any direction) of 0.
• In Shane AO motor control GUI:
  • Observe WFS steering motor movement(s) in order to confirm stage has achieved desired position.
• It may be necessary to attempt the above procedure a number of times.

Alternatively, if the above procedure proves unsuccessful, it may be necessary to visit the instrument, locate the affected stage and manually exercise the stage to ensure that there are no obvious problems.

For WFS steer 2 Ry (2017-07-09/10) the stage appeared to have shifted after the intervention. On this occasion, it became necessary to offset the WFS steer 2 Ry by -1300 load encoder counts in order to get proper centering on the WFS camera and get the loops to close properly:

• Re-calibrate WFS steer 2 Ry.
• modify -s saomot steer2ryraw=-39189 - This puts the motor in the proper place for on-axis imaging and closing of the loops.
• modify -s saomot steer2rymod="Pos ENGR" - This puts the motor in position engineering mode.
• modify -s saomot steer2ryzpx=-37888 - This tells the stage it is homed and that the current position -39189 is really the old on-axis motor position of -37888.
• modify -s saomot steer2rymod=Pos - This returns the motor to default position mode.

1. Edit the startup configuration file:

   $LROOT/data/saomot/saomot_dispatch_2.conf

   The line of interest is the "HomePosition" field for STEER2RY, which is line 574 in the configuration file:

    
      556 << Axis A >> 
      [...] 
      559     PrefixName STEER2RY 
      [...] 
      574     HomePosition 0 
      

   Change 0 to (e.g. 1300), and verify the sign and value are correct by observing the behaviour of the system. HomePosition gives the RAW value of the home location, so it should be the same value as you would type in using the ZPX keyword.

2. Notify W. Deich (SPG), so that the new value can be placed into the CVS-controlled file, and rebuild/reinstall the configuration file with the correct value.

Intervention:

• Consider lubricating motor stage and/or associated limit switches.

Cause:

• Extender on the motor actuator wedged in place and will not move. Likely, intermittent drag on this mechanism for extended period.
• Possible binding of motor stage and/or associated limit switches.

Associated Issues:

• Issue 11016 (WFS Steering Mirror 2RY mechanism stuck).
• Issue 11017 (WFS steering mirror 1Rx load encoder mechanism binding).
• Problem most affects NGS field steering. However, all WFS motors MUST be restored to their nominal on-axis positions before transitioning to LGS.

Change Log:

2020-10-27: This motor is no longer installed or used following the 2019/2020 upgrade of the WFS mechanism.

2017-12-04: Added WFS Steering Mirror Maintenance Procedure.

2017-08-05: Updated (binding/lubrication of limit switches).

2017-07-10: First version.