[evlatests] the ACU and Stowing

[Steven Durand]

This is how I think this works.   The ACU MIB calculates the pointing 
and is told to calculate the pointing for the next X minutes.   Even if 
the network goes down the ACU MIB will continue to talk to the ACU and 
point the antenna for the specified X minutes.  After the X minutes have 
expired, the MIB stops talking to the ACU.  If the ACU is not receiving 
pointing commands, the ACU will auto stow the antenna after a timeout. 
The timeout is determined by an RC time constant and varies from antenna 
to antenna but is usually between 5-20 minutes.

Ken said  “he had a mysterious experience last night …Approximately 40 
minutes later, the antenna 14 stowed itself and corrected the elevation 
limit”

My guess is the ACU MIB stopped talking  so the ACU stowed the antenna.




Rich Moeser wrote:
> 
>>> Approximately 40 minutes later, the antenna stowed
>>> itself and corrected the elevation limit;
>>
>>
>> I had a mysterious experience last night which bears on this.
>> Antenna 14 was again driven into a limit because the antennas
>> were pointed before the script was properly started.  Why that
>> happened is another story.  By the time I was called the
>> antenna had probably been in a limit for some time: the exact
>> time can be found in the monitor data base.  In preparation for
>> getting the antenna out of the limit I asked the operator to be
>> sure that the ACU was getting valid postition commands by hitting
>> the 'go' button while there was a valid elevation in the elevation
>> command box.  He did this several times and reported that the
>> antenna had started moving up in elevation.  It eventually was
>> stowed and secured.  All this without having submitted the limit
>> override command to the ACU.  It seems likely that an antenna
>> that wanders into a limit on its own as has been happening lately
>> will eventually timeout and autostow.  It is not clear whether
>> an antenna which is purposelfully driven into a limit will also
>> do so.  This, perhaps, helps explain the behavior Pat reported
>> above.
>>
>> Does anyone remember if the ACU was actually designed to operate
>> this way?
>>
>> As an aside the operator reports that there is no box in the new
>> ACU screen to type in motor control commands.  Had it been necessary
>> we would have had to use the old ACU screen for the purpose.
> 
> 
> Actually, if you take a look, there are az and el command textfields in 
> the new ACU screen. They are located on the bottom right hand corner of 
> the screen with the other command components. The operator need only 
> enter a value in the textfield and hit 'Enter' (there is no 'go' button 
> on the new screen).
> 
> --Rich
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-- 


Steven Durand, MTS               National Radio Astronomy Observatory
Electronics Division             1003 Lopezville Road
505.835.7103                     Socorro, New Mexico  87801