Not many people know but we have an piece of open source software for controlling an Antenna Tracker.  It's been built by Tridge (Arduplane lead developer) for use in the outback challenge.

Sadly we have no documentation and, as far as I know, nobody except Tridge has used it.  Still given Tridge's track record on building great software I suspect it works well and if it doesn't, I'm sure we can fix it.  So to not let this piece of code go to waste, I'd like some help from people who are interested to give it a try and help me figure out how it works.

Here's the little that I know:

  • It runs on any of our supported board (APM1, APM2, PX4, Pixhawk, Flymaple and perhaps VRBrain)
  • For APM1/APM2 users building the code is as easy as opening our hacked ArduinoIDE and selecting File > SketchBook > Tools > AntennaTracker and then building in the normal way.  For PX4/Pixhawk, our autobuilder doesn't automatically build a binary but I can provide one if people are interested.
  • It can control a Pan and Tilt gimbal like this or this found on servocity.com.
  • It may or may not require a GPS
  • It must somehow receive vehicle position updates from the ground station which has the telemetry radio that is connected to the vehicle. Maybe through a USB cable.  Tridge probably uses the python ground station, MAVProxy, to passthrough the vehicle position data to the AT but perhaps we can get MichaelO to build out a similar feature in Mission Planner.
  • I imagine this antenna tracker could also be used to keep a camera focused on the vehicle which might be good for easing the burden on creating videos of our vehicles.

So if you want to give it a try please do and stick any findings, questions or issues below. Alternatively Issues can go into the issues list.

I'll start sticking things into the wiki as they become clear.

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Hi Patrick,

Are you connected with this Pixhawk lite to mission planner ? This would help you to see what is happening and also would give you access to the "Actions" tab underneath the HUD display. In this actions tab you will find a button to arm and change mode.

To troubleshoot, first go in manual mode. Then go in the configuration menu to change the sliders (roll/pitch) manually. You should see your tracker move to the ordered position. If this does not work, it would confirm your servos are not receiving power adequately or do not receive the PWM signal from Pixhawk's outputs.

Can you share your wiring diagram so we can take a look at what is going wrong ?

@Hugues,  I was able to get the servos to respond, the pinout schematic I was using from ebay was wrong and I had connected to the wrong outputs.  

However I have another issue.  When the tracker starts tracking, the pan servo overshoots and oscillates very slowly.  The pitch servo is stable.  Could compass error/incorrect calibration cause this?   I am using continous rotation servos with a gearbox so they move fairly slowly.  The pitch is stable so I am not sure what is going on.

Thanks,

Patrick

Good you have the servos working now.

About the oscillation, I would first think of a PID problem. Have you tried to modify the P,  D gains on the pan servo (through mission planner) ? If it oscillates, could be D too low for a given P value, or could be P too high.
 
Patrick Duffy said:

@Hugues,  I was able to get the servos to respond, the pinout schematic I was using from ebay was wrong and I had connected to the wrong outputs.  

However I have another issue.  When the tracker starts tracking, the pan servo overshoots and oscillates very slowly.  The pitch servo is stable.  Could compass error/incorrect calibration cause this?   I am using continous rotation servos with a gearbox so they move fairly slowly.  The pitch is stable so I am not sure what is going on.

Thanks,

Patrick

Isn't it about time for a new version. Seams like the current version needs a few improvements.

@Hugues,  I got it to work, the oscillation was because I had inadvertently set the servo type incorrectly when I was testing and forgot to put it back. In any case, it's working now.  I did have to adjust the gain to tune the servos though. 

Here's a picture of the finals product.  It uses a Ubiquity Nanobeam M5, 5Ghz WiFi dish. I could get 15km with my previous tracker, so I am hoping this one is more accurate and it will go further. The mounts are 3-d printed.

Hi Patrick,

Your tracker looks great! I'm glad you got things ironed out. The Pixhawk Lite does have several incorrect pinout diagrams so the images below are for others that may want to use this $47 low cost controller for their tracker. The images are from Mike Kelly's blog here. I also started a thread on RCG here.

great!

Patrick Duffy said:

@Hugues,  I got it to work, the oscillation was because I had inadvertently set the servo type incorrectly when I was testing and forgot to put it back. In any case, it's working now.  I did have to adjust the gain to tune the servos though. 

Here's a picture of the finals product.  It uses a Ubiquity Nanobeam M5, 5Ghz WiFi dish. I could get 15km with my previous tracker, so I am hoping this one is more accurate and it will go further. The mounts are 3-d printed.

Anybody have issues with the compass errors being large with the tracker? I have a PixHawk lite board, with external compass=GPS.

I see errors as big as 15 degrees around the circle and have tried re-calibration multiple times with no change.  I am using continous rotation servos, so I am assuming I must use the compass to position the yaw. Any ideas on how to fix?

I had that problem. It was because of all the electronics and other metal parts. I put the mag and GPS up on a wood stick, now all is good.

@Mike, thanks for the tip.  

Hi All, we have built our tracker and it works fantastically. We have two telemetry modules on the tracker which is controlled by a pixhawk.

The Antenna Tracker Pixhawk is able to pick up the plane and point to it.

The problem we have is that when we connect the telem2 output to mission planner, the control is for the antenna tracker, not the plane. (i.e.what comes out of the antenna tracker telemetry is control of the tracker, not control of the plane.)

How do we relay the telemetry from the plane received by the antenna tracker pixhawk to Mission planner.

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