Shane AO  

Problem: ShaneAO WFS Steering Motor

Manifestation:

• In Shane AO motor control GUI, WFS steer indicates red cross and/or found to be in Halt mode.
• Moves fine in the positive direction, but has trouble in the negative direction, giving off-on-errors almost immediately when near the forward limit.
• Error message of the form:

   
     Error setting steer1ryraw: steer1ryraw: ERR_ENCODERS_DISAGREE (-5059) Motor and 
     load encoders disagree (*ENC != *ENE) 
     while executing 
     "exec modify -s saomot steer1rxraw=$s1rx steer1ryraw=$s1ry steer2rxraw=$s2rx ste 
     er2ryraw=$s2ry" 
     (procedure "fieldsteer" line 26) 
     invoked from within 
     "fieldsteer $e $n $lr $ud" 
     (procedure "calcNE" line 5) 
     invoked from within 
     "calcNE -$dSx2 0" 
     (file "saoBxy4tmpNGS" line 193) 
     

Solution/Recovery:

• 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
  • If the foregoing is unsuccessful, try Re-calibrate.
• 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 fieldsteer GUI:
  • Apply a Back On-Axis.
• 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, exercise stage(s) in Jog Engr mode (with motor powered On) at various speeds, first at low speed (e.g. +/-500) then at successively higher speeds (up to a maximum of circa +/-8000 when there were no off-on-errors at the lower speed.

For certain stages (e.g. WFS steer 1Rx there may have been grit or something that was impeding motion along part of the shaft as it now (2017-05-10) moves trouble free.

For WFS steer 2Ry one might expect continuing intermittent problems with homing (this procedure has been attempted in the past with varying results, mostly just getting lucky when it calibrates successfully). However, a specific recovery procedure for WFS steer 2Ry was derived 2017-07-10.

Once calibrated and in its normal range for operations in NGS mode, the stage seems to move fine, so most of the trouble is near the forward limit.

Intervention:

• Consider lubricating motor stage and/or associated limit switches, in accordance with WFS Steering Mirrors Maintenance Prodecure.

Cause:

• Possible binding of actuator, mount and/or associated limit switches. Proposed lubrication maintenance interval: circa 30 operational ShaneAO nights.

Associated Issues:

• Issue 9695 (WFS steer 2 Ry motor).
  Issue 10309 (WFS steer 2 Ry motor won't calibrate).
  Issue 11017 (WFS steering mirror 1Rx load encoder mechanism binding).
  Issue 11121 (WFS steer 1 Ry motor errors).
  Issue 11182 (STEER1RYMSP cannot be set higher than 2000).
• 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:

2018-02-02: Updated.

2017-11-28: Updated.

2017-10-06: Updated.

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

2017-07-10: Updated.

2017-05-10: Updated.

2017-03-10: Updated.

2016-11-20: Updated.

2014-12-09: First version.