[evlatests] Antenna/ACU/servo behavior in OTF mosaic tests

[Bryan Butler]

not that i know of.


Barry Clark wrote on 5/23/16 8:14 :
> Has anybody tried dec +89, moving 2d/sec in RA?
>
> On 05/22/2016 04:44 PM, Vivek Dhawan wrote:
>> An update on ACU behavior during fast tracking (OTF-mode). Issues found
>> in previous tests are listed, with their current status. Plots exist to
>> support these assertions, but are not attached here.
>>
>> 1. Interpolation of commands was incorrect (to all ACUs) near azimuth due
>>     South, when tracking in the counter-sidereal direction.
>>
>>     This was fixed in the executor.
>>
>>
>> 2. Tracking error (deviation from commanded position) had a
>> significant DC
>>     offset plus oscillations, in azimuth, especially on the NEW ACUs
>> ea01,
>>     14, 17, 21. For these units, Doug W. has tuned the bias currents
>> (in AZ
>>     only, I believe) and eliminated most of the oscillation.
>>
>>     The elevation errors remain, ~1’ deviation, and seem to be random,
>> i.e.
>>     they are not antenna or servo resonances. There are differences
>> between
>>     antennas, its likely this too be tuned away: ea01 and 17 have large
>>     EL rms, ea14 and 21 are very much better.
>>
>>     All 4 new ACUs have a DC tracking offset when we calculate the error
>>     = (Position - Command) from the logged pointing data, but do not show
>>     the offset on the error signal that drives the servo. This still
>> needs
>>     to be clarified, it may be another timing issue (distinct from OLD
>> ACUs
>>     in item 3).
>>
>>     The settling time for new ACUs is ~3sec, a factor of  ~2 better than
>>     the old ACUs, and unchanged from before the tuning.
>>
>>
>> 3. OLD ACUs had small tracking errors and no oscillations, but showed
>> jumps
>>     in the calculated error, ascribed to timing slop in labeling the
>> current
>>     command, future command, and measured position (in the MIB).
>>
>>     Hichem has updated the MIB code (on old ACUs) to fix the data
>> handling,
>>     and these timing errors are now eliminated. This code has been tested
>>     on the sky, on a subset of antennas, but is not yet deployed
>> anywhere.
>>
>>
>> 4. The command sequence for OTF rasters was examined in detail, refined,
>>     and tested again on May 19, near transit, 77deg EL, and at ~40deg El.
>>     Bryan is looking at this, I believe it looked good.
>>
>>
>> 5. MCAF (in test version) is writing the pointing table in binary form,
>>     and as of Friday, Rich had successfully read these into CASA.
>>     Promotion of test MCAF to production is expected soon.
>>
>>
>> In summary,
>>
>> OLD ACUs : Look good to go, after the MIB update is deployed.
>>
>> New ACUs : Look good in AZ, need some tuning in EL. DC offset between
>>             external and internal error signals needs to be understood.
>>
>> --------------------------------------------------------------------------
>>
>>
>>
>>
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