Developer

figuring out the Antenna Tracker

3691139590?profile=originalNot 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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Replies

    • MR60

      Hi Mike,

      experience with ardutracker can vary so much from people to people although using the same firmware, which I believe shows how "green" it still is and how ultra-sensitive it is to setting right a certain combination of parameters : for example, in my case, I have succedded to make the pitch work but only with standard positional servos and only if you define a range of movement no more than 90 degrees (although the servo could do more)  and only with yaw tracking that can only be done within180 degrees  and only without reversal contrarily to how it is supposed to behave. Some people have made it work but it remains a mystery why it sometimes works for some and sometime not for others. I suspect that some combinations of parameters work and some other combinations does not work. For me at the moment it is pure trial and error (it took me months banging my head on the walls to have something working, but still in a very limited way)

      Like you, I would like to replace the yaw position sevo by a continuous rotation one. I believe the servo type in the firmware is set for both pitch & yaw servos, unfortunately not separately configurable.

      Maybe we should call for a group of volunteers, among which some are developers, to develop forward the current Ardutracker firmware base ?


      • We need to talk Randy into coming out with more Beta versions so we can find out what works and what does not. When he releases a beta version he needs to post his exact setup so we will have a starting set of parameters that’s known to work together. I have asked about gains and other things but never get any useful answers.

        I am not a programmer but I do have time to do some beta testing. I have the Servo City mechanics (7:1) with a custom pinion gear to get me 360 on yaw. That works well with the Jakub0.7.2 custom firmware. With that firmware the two telemetry modem option is not supported. I solved that problem by using RFD900+ multi-point setup. It works well but would be a bit of a challenge for someone starting out from scratch.


        .

        • Developer

          It's certainly been a while since the last beta.  Things are stabilizing these days and I actually do hope to do a beta release in the next two weeks which will just include logging of the baro data which should help us determine why some people's trackers always point down.


          • For beta testing it would be good if you could add a new parameter that allows selection of baro or GPS altitude and maybe a blend of the two. That way we could get a wider range of data to see what works and what does not.

            What’s the key difference in the Jakub0.7.2 custom firmware that allows it to work where others don’t? I am not a code guy – maybe someone who has studied the code could enlighten me on that point.

            .

            • Developer

              I think the major difference between Jakub's version and master is that Jakub's uses the GPS altitude.  I'm not sure though, I haven't actually seen the code.

              • It has been a while but as far as I remember there is no GPS altitude in this release. Most differences can be found in mode selection and servo operation. Generally there is nothing special in that firmware. I am unable to jump back to development of this code for now due to lack of tracker and lack of room for that (I recently moved to new appartment). As I always say - I will eventually get to it :)

          • MR60

            excellent news and glad you'll find some time to help us out figuring antenna tracker, because we still have a long way to go !

            The pitch bug is certainly high on the priority list but if we could just have this firmware working correctly for the basic features that are supposed to be included in this current version, I'd already be in heaven (to start with :  parameters that do what they're supposed to do, like reversing a servo movement. I'm not even wishing a correct display of parameters on mission planner, we could do without or with another GCS).

            To help with what I can which is not much I'm compiling some observations following my experiments with the firmware, that I'll post when ready (might take a few weeks)

            Here a short video I made illustrating my current partial successful use of using the firmware,

  • I have a tracker that is working well but it has standard servos. I would like to put a continuous rotation on the yaw and keep my standard servo for pitch. Are there parameter settings that will allow this combo?

    Also what’s the latest on firmware development? I have been using the custom firmware because the pitch never moves with the latest firmware.

    .

  • MR60

    Hello,

    Trying deseperatly to make the antenna tracker firmware work, I succeeded so far to make use of SITL to simulate a vehicle to be able to test the real antenna tracker based on the simulated positions of the vehicle.

    I use a AUAV-X2 boartd on the antenna tracker (same as Pixhawk) and an external compass. GPS position has been fixed for testing.

    I found two blocking issues/bugs in the antenna tracker firmware (in addition to the already known blocking issue the pitch does not track at all):

    • Bug 1 : the reversing of servo movement is without effect. Changing it in the full param list or on the GIU of mission planner does not change the servo rotation direction, rebooting Pixhawk after these change does not solve the issue. Picture below:

    3702238116?profile=original

    • Bug 2 : Yaw tracking stops after reaching the servo position limits. It is supposed to do a 180 deg reversal, but it does not (I sue 180 deg servos in pitch and yaw). See picture:

    3702238179?profile=originalThese three bugs make antenna tracker firmware currently unusable. There does not seem to be any improvements more development follow up on this firmware, a pity.

    I will have a look at the 360openTracker open source solution as an alternative.

    • Hugues,

      I agree with your assessment and I'm glad that you were able to get SITL to simulate a vehicle and test the APM AT.

      Hopefully, we just have to be patient and wait a bit longer. Priorities change so it is up to the community to find others that are interested in the project and have the skills to modify the code. Perhaps we will get lucky and Randy or Jacob will return. One other thing you might consider is to open a ticket with your findings using the Github Issue Tracker.

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