Gregorian motor torques

dec08

Links:
gr motor names/locations
dec08: Gregorian motor torques while galfacts scanning at meridian.

Motor names/locations (top)

There are 8 Gregorian motors numbered uphill to downhill: 11,12,21,22,31,32,41,42 They are located at:

gr motor locations

Aux mode allows you to disable 1 motor and continue running
The hydraulic brake slows the dome when it moves downhill.

07dec08 motor torques during galfacts scanning

Project a2130 (galfacts) scans the telescope along the meridian at .0234 degs/sec moving from za=2 to 20 (about). They do this continuously for 6 hours at a time. Data from 06,07,08dec08 was used to look at the Gregorian torques during this motion.

Histogram torque vs velocity (.ps) (.pdf) :

Each motor is color coded.
HB (hydraulic brake) is connected to motor pairs (11/12 and 31/32).
Most of the velocity is at +/-.0234. Some of the velocity bins have 0 counts so the torque values for these velocity bins are not shown.
Top: motor torques histogram binned by velocity (51 bins over .1 deg/sec)
2nd: avg torques for motors 11,12,21,22
3rd: avg torques for motors 31,32,41,42
4th: histogram of counts in each velocity bin.

The dashed red line is at .0234 deg/sec is where most of the motion occurs.

Gregorian torques vs Za (.ps) (.pdf) :

Each panel shows 2 motors. Black,green is moving uphill, red/blue is moving downhill
The speed is abs(.0234) deg/sec
When moving downhill the torque goes to 0 between 10 and 15 deg za then it begins to rise again.

We only measure the absolute value of the torque.
When the down torque goes through 0, it is changing the direction from the motors pushing uphill (gt 15deg) to the motors pushing down hill (against the hydraulic brake).

Top: motors 11,12
2nd: motors 21,22
3rd: motors 31,32
4th: motors 41,42

SUMMARY:

The torque histogram versus velocity looks different for mot31 moving downhill. It is working harder than the others. This only shows up in the bins with fewer counts (when the velocity was changing) so it may not be real.
Moving uphill the slope of tq vs za is different for the each motor pair. The downhill motor of each pair is working harder at low za.
Moving downhill the motors have to start pushing downhill between 10-15 deg za.

The uphill motor of each pairs starts to push downhill sooner than the downhill motor.
This is consistent with the uphill measurements.

processing: x101/081209/AGC2130.pro

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