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

    Another issue I am blocked at in figuring out antenna tracker;

    I have the antenna tracker configured in proxy mode (copter linked via 3DR radio to <-> a pixhawk on the antenna tracker with a second radio connected to <-> mission planner).

    The antenna tracker firmware is the last 0.7x version.

    Both the copter and antenna tracker show up correctly on mission planner's map. All manual, scanning and test servo modes function correctly.

    The only issue I'm experiencing is with the Auto mode that tracks only in yaw, not in pitch.

    I tried to reset, to turn on copter and tracker in different chronological order, still same issue.

    The attached picture shows the status page, where "alt error" is at "infinite" value, which seems weird.

    I wonder if the baro altitude information from the copter is received by antenna tracker ? Is this a known bug ?

    3702130189?profile=original

    https://storage.ning.com/topology/rest/1.0/file/get/3702130189?profile=original
    • It may be possible that you don't really have the latest firmware as previous versions did have a pitch control issue. Try using the "Test" butttons on the Extended Tuning screen to manually position your pitch to verify operation. One other possiblity is that the copter is too close to the AT. You need a good 50 feet (15m) separation.

      • MR60

        Manual servo test are fine with the Pitch, it is only in Auto mode that it does not work.

        I have also configured the parameter that gives the minimum distance to begin tracking and have set it to one meter for my bench tests.

        Worse, Sometimes it works, sometimes it does not. It is like the Auto mode does not trigger in certain circumstances that are undefined and unexplainable.

        I worried that this firmware is still too green and needs to mature for a reliable functionning tracker.

    • I'm closely monitoring satellite antenna tracker project on satnogs.org They are on v3 now and have really nice designed hardware part, It is open source project and most components are 3D printable.

      3702604645?profile=original

      Electronic part is simple and efficient. In V3 they started using geared DC motors instead of stepper motors which made whole thing more electrically efficient. I think we are having some common ground here. V2 is mounted inside of plastic box without the need for aluminium beams.

      Electronic for V3 is still work in progress, but basically whole thing is controlled with Arduino that can be installed on controller board. I guess that same Arduino with addition of GPS/compass module and 9dof imu can run mavlink, drive motors and serve as nice ground station antenna tracker for APM/PX powered vehicles. 

      3702604789?profile=original

      On the other hand they are not using IMU/Compas sensors in their project as unreliable. Possibly they have to check few things at our forum about sensors calibration. It would be definitely nice to see Lead developers on both projects  communicate on the subject.

      SatNOGS
      Open Source global network of satellite groundstations
  • I have been working on the antenna tracking firmware version 0.7.3 for my senior design project. I can get a HITL working with a simulated plane and the antenna following it properly. But I can not get the antenna current heading to align with the direction to the next waypoint. The antenna's heading on mission planner is roughly 30 degrees off the actual antenna direction. I have tried adjusting the compass' yaw to account for this with no luck. Anyone else had this problem?

    • MR60

      I had a 180 degree offset between current heading and next waypoint; I solved it by adjusting (trial and error) the "reverse" parameter of RC1 and RC2. This cnages the direction of rotation of the picth and yaw servos. You have to find the right combination (4 possibilities)...

  • Hello,

    I've been looking for an answer to this question everywhere and was hoping someone would be able to help me. I had seen that the GPS module from 3dr apparently has a 1-2s lag time associated with it. This affects the GPS based tracking function built into mission planner.

    What I'm hoping to find out is:
    1. From anyone's experience is this lag time unavoidable (Sorry I know this isn't related to the AT firmware)
    2. Does this same lag find it's way into the alternative approach that is the AntennaTracker system? Or does it only rely on compass and elevation data to determine location without a GPS based lag?

    Any help from anyone with experience with either of the two systems would be greatly appreciated!:)

  • I just wanted to follow up:  We got the tracker to work just fine this summer with our PixHawk systems.  Many thanks to everyone in the forum for their advice!

    • Would you share your setup, changes you made to parameters, and sequence/order you connect things with the group. I'm still struggling. Thanks
  • MR60

    Hi,

    I do not succeed to make antenna tracker work. I repost here a question raised on APM forum as it seems to be the place for discussing AT matters.

    This is what I tried:


    I follow the wiki instructions to setup an antenna tracker, using a pixhawk (driving the antenna tracker servos). Firmware is installed and configured. This is a "proxy mode" setup with AT in the middle. My objective is to use AT for long distance telemetry link to the GCS.


    I used the connection scheme of the wiki with a 3DR radio link between the vehicle and the antenna tracker's pixhawk. And then I connect mission planner via usb cable to this pixhawk.


    I get in mission planner the icon of the antenna tracker on the map, I get all of the config menus of the antenna tracker.
    But I do not see anywhere the vehicle as if the antenna tracker was not connected to any vehicle.
    I tried CTRL+X to switch vehicles on the MP display but no joy : no copter in the drop down list, only antenna tracker.

    What did I miss ?

    Secondary question : what do these two parameters in the antenna tracker config params mean  : SYSID_TARGET, SYSID_THISMAV? Should I set them to specific values ? Why is SYSID_THISMAV to a value of 2 by default ? 

    3702122122?profile=original

This reply was deleted.

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