| UK Astronomy Technology Centre | Chris Tierney |
| Royal Observatory, Edinburgh | 31st March 2001 |
The NCU beamsplitter is driven into (or out of) the optical path to the wavefront sensor by a steppermotor.
The "in beam" position is considered to be the upper limit of travel (at the upper limit switch), whilst
out-of-beam is at the lower limit. Any position between these two is also selectable by the user, although
this would not normally be required.
Safety
All the NAOMI mechanism control screens display two buttons - a red "Emergency" button
and a green "Safe" button - in the top right corner of the screen.
Left clicking an "Emergency" button will immediately stop any motion by any part of the wavefront sensor or calibration unit. Thereafter, any demands for motion are rejected, until the user left clicks on any of the "Safe" buttons. Many mechanisms will then demand to be re-indexed before allowing the execution of any other motions.
Note: This safety feature has no effect on the motion of the Durham deformable mirror (DM) or fast beam-steering mirror (FSM), nor any component of the electronics associated with NAOMI.
For more information, see the NAOMI mechanism software
safety page.
Commands to the beamsplitter assembly
Before any other use, the assembly must be initialised by clicking the Mode button "Init",
followed by the Directive "Start". The user should see the status display "Command accepted -
record state is busy". The record state will return to "idle" when initialisation is complete.
For all commands, in normal operation the user should see the status display "Command accepted - record state is busy" when the command starts. When the command is complete, the record state should change to "idle".
A status of "Command rejected" indicates that the command was not started. A status of "record state is error" indicates that the command did not complete succesfully. In both cases an error message will indicate the cause of the failure. The mechanism can be moved if the "Move" Mode button is clicked. The "Start" Directive will initiate the motion, whilst "Stop" will bring the mechanism to a controlled stop if desired.
Note: The "Index" Mode button has not been included on this screen, as motion to the in-beam
and out-of-beam positions is implemented as an index to the upper and lower limit switches, respectively. The
record will disallow any standard move to an intermediate position unless a previous move to "in" or "out"
(see below) has been executed, thus ensuring that the mechanism is indexed.
Parameter input/output
Demand position and Demand Velocity can be input by the user, in units of mm.
Current Position is updated as any motion progresses.
In normal operation, the stage will be moved between two locations, which can be input into the Demand position field as:
Status and Higher displays menus give access to further assembly information and the top-level screens, respectively.