ESI Slit Wheel Move Failed

We have experienced two problems with the slit wheel failing. To determine what the problem is, double-click on the brown box representing the slit mask (upper). This should bring up a "Details" panel showing the three wheels of the triple wheel. Click on the "Diagnostics" button below the slitmask (upper wheel). This will bring up detailed information on every control keyword for the upper wheel.

Note the text in "Slitmask message" line. Does it say that the motor is off? If so, the motor probably hit a torque limit and turned itself off. Follow the recovery instructions below.

Oscillations

If the motor has not turned off, look at the two lines labeled "Slitmask raw position" (near the middle of the list) and "Slitmask raw position target" (about 3/4 of the way down). The "target" is the requested position in raw encoder counts. The raw position is the current value. The tolerance for the difference between these two values is 4 units, corresponding to 20 microns, which is 15 milliarcsec, i.e. tiny!

Is the "Slitmask raw position" hunting back and forth across the "target" value? If so, there are a number of possible problems. One is that the Galil controller is in a funny state. You can go to the Web page describing how to reset a Galil controller and reset controller 0 to try to fix this. Note that after resetting the controller you probably will need to reinitialize the motors. You can still test the upper wheel by choosing a slit and clicking "Move," however. The upper wheel will initialize itself and you can see whether rebooting the Galil has solved the problem.

Another problem may be dirt on the encoder strip on the wheel, a misaligned encoder head, or a dirty encoder head. All of these problems will require some time to fix, and generally cannot be performed at night. You might at this point consider whether you can accept the oscillation while observing. Remember that each encoder unit is only 3.6 milliarcsec. As long as the raw position is not changing too much, you probably can observe with the oscillations happening.

Some tricks may help you stabilize the wheel if you absolutely must have it at its commanded position. You can try rotating the instrument to another position angle. You can try changing elevations (although obviously this implies a change in target). You can try moving first to one extreme of the filter wheel and then back. Sometimes these measures help, sometimes they don't.


Motor has turned off

Probably this has occurred because the motor torque hit a limit. Note that you can monitor the torque via keyword:

cshow -timestamp -s esi slmsktor

Recovery

First, turn off the dispatcher for the Galil. Log onto koki as esieng and type:

esi stop dispatcher2.0

Telnet onto the Galil 0 controller:

telnet 192.168.5.2 2001

Hit a couple of times. You should get a colon prompt, ":". At the prompt type "MOX". This will turn the motor off. At the next prompt type "SHX". This will turn the motor back on and tell it to servo at its present position.

Exit the telnet session by typing "Ctrl-]".

Restart the dispatcher:

esi start dispatcher 2.0

Once the dispatcher is up and running, you should again be able to move motors. However, the flexure compensation system (FCS) will no longer be working properly, because some of its higher-level keywords have been confused. To get it out of this state, set the focus value to 1000 and click "Move" on the GUI. Then reset to your previous value. A look at the collimator details window should show some small, changing numbers in the COLLOFF keywords, zeroes in the COLLUSR keywords, and some numbers in the hundreds or thousands (absolute values). Check the diagnostics panel for the message, too.

Note that if the "MOX/SHX" sequence above does not fix the problem, instead you can reset the entire Galil 0 controller by typing "RS". Wait for the "arriba!" statement on the telnet session. This assures that the controller is done rebooting. However, now the controller has lost information about ALL Galil 0 stages, and you should click the "User Config" button on DashBoard, then click "Initialize Instrument". This will take awhile.

After initialization is complete, click on "TV Guider" and select the "Clear" filter. Click "Go" to start the move. The "Nominal" focus should already be set; you don't need to worry about that.

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