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I am building a prototype for an antenna tracking system. The following animation will make it slightly easier to understand what I have in mind:

https://youtu.be/DZ0LRf6_Zew

The two antennas are: https://www.wimo.com/xquad-antennas_e.html

  • 2.3kg each (5lbs)
  • 1.46m long (less than 5 ft)
  • They will have to be placed 2.8m apart (just above 9ft).

I intend to mount them on the horizontal mast so they are balanced.

I have what I believe is a good guidance algorithm that uses an IMU (a small sensor with magnetometer, accelerometer, gyroscope) that does not require feedback from the motors (azimuth and elevation).

The installation of this antenna will be temporary for a few hours at a time and I'd rather NOT use a designated antenna rotator like the Yaesu G5500 for this prototype.

I would like a mechanical resolution of roughly 1degree. I do not have strict values for speed, ideally it should take less than 10-15 seconds for the first move to track the satellite. After tracking has started, a full rotation typically takes several minutes, however I'd like to avoid mechanical oscillations. This will be used outdoors in controlled conditions, but there might be some wind. I am not too worried about rain at this point.

My question is: where do I start to size the motor and possibly a gearbox for this? Being a hobby prototype I am not ready to invest a huge sum of money for top notch motors, and I see that the internet has relatively cheap NEMAxx motors available, with options for a planetary or wormgear reduction, from 1:3 to 1:100. At this point, I don't know how to size the mechanical components, and before I commit hundreds of dollars in motors, gearboxes, drivers, I'd like to hear from somebody that has more experience.

Alessio Sangalli
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    "I'd rather NOT use a designated antenna rotator like the Yaesu G5500 for this prototype." - but if you _did_ use it, would it have the desired speed, torque, and resolution? – Bruce Abbott Aug 27 '19 at 01:56
  • According to the G5500 spec, it has 14kg*m (really? kg*m?) or 101ft*lbs elevation torque and 6kg*m or 44ft*lbs azimuth torque. Braking torque is even higher at 40kg*m or 289ft*lbs. These values are probably much more than I need but I see what you mean, I can use those to spec my own system. I consider the G5500 a bit slow so I guess I can trade off some for speed. Pointing accuracy is defined as "±4 percent" which... is almost 30 degrees? I find that hard to imagine. – Alessio Sangalli Aug 27 '19 at 03:10
  • Source for the G5500 specs: https://www.yaesu.com/downloadFile.cfm?FileID=8814&FileCatID=155&FileName=G%2D5500%5FIM%5FENG%5FE12901004.pdf&FileContentType=application%2Fpdf – Alessio Sangalli Aug 27 '19 at 03:14
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    I am not an expert on mechanical engineering, but it sounds like the G5500 would be overkill for your project. I would build the antenna system first, then operate it manually and measure the torque required to move it. From there you can calculate the required motor torque and speed. – Bruce Abbott Aug 27 '19 at 03:38
  • I second @BruceAbbott 's point. Measuring the actual necessary torque is very useful, if you have the opportunity. – bitsmack Aug 27 '19 at 04:15
  • Yeah in fact it's probably not a bad idea. I have a digital strain gauge with peak detection that should work OK and this would allow me to take into account the "hidden torque losses" causes by bearings etc. Still, if anybody with experience in a system similar to this wants to tell me their perspective... :) – Alessio Sangalli Aug 27 '19 at 04:15

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