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

  • OK guys, so reading you comments I come to the conclusion that v1.0 is not good to use??

    I recently replaced my 3kg servos, which were using relative good on some old version... around 0.74 for instance?!?

    I installed 20kg servos... but I cannot get them to move properly! When testing all moves well, but when it has to track... there is a considerable delay in the reaction, and even when it starts moving it is constantly shaking left and right (for pan), and up and down (for tilt). I played around with the params but was unable to fine a setting that would stop this behaviour and would make it work properly! At least the old servos with the old firmware moved and tracked very well... and these right now are almost worthless.

    Would going back to an earlier version of the firmware improve things? Preferably one where the EKF is not used?

  • MR60

    All we need now is find a developper in this community who is able (=question of time and skills. Randy is, as far as i know, the only dev who worked lately on the antenna tracker firmware but he's obviously busy on other things) to take the antenna tracker code re-engineering in hand to build this simple and straightforward tracker. I'm unfortunately not a developer but could assist in the functional analysis and requirements definition to help guide the development.

  • I can confirm the deviations in tracking, as well as delays, as well as pointing correctly if the plane moves from right to left and a big deviation when the plane moves from left to right. It makes it almost useless. Sorry to be so critical, but that is the reality.

    Before the introduction of Mavlink2, I was using Jakub Oller's firmware. It was flawless. Unfortunately, with Mavlink2, there were problems.

    I also feel it is over engineered. I'm not a software engineer, but I totally agree with Hugues. EKF is probably not needed, neither other bells and whistles.

    For me, it should have like an auto tune function, be able to work with 360 degrees servos and point to the plane. Simple and straight forward.
  • MR60

    Hi Patrick,

    I agree with you that EKF to point two servos to a predefined spatial 3D coordinate is not required at all. I suspect that EKF is the cause for the pointing large deviations I noticed because EKF transforms real sensed data into future projections. However we do not need to do that for coordinates : they are what they are and should not be filetred in any way.

    EKF is probably also the cause of the tracking lag we observe as it requires a time delay to compute.

    But I am no developper and we'd better let developpers explain why they chose to use EKF for antenna tracker ?
     
    Patrick Duffy said:

    Well for some reason the developers seems to keep supporting APM on plane. We are talking about a tracker here, is the firmware that advanced it needs pixhawk? I am puzzled.  It's not a multi-rotor that needs more advanced navigation. Well I guess I am stuck having to fork out $60. It all adds up when and you get nickel-and-dimed building this stuff. 

  • Well for some reason the developers seems to keep supporting APM on plane. We are talking about a tracker here, is the firmware that advanced it needs pixhawk? I am puzzled.  It's not a multi-rotor that needs more advanced navigation. Well I guess I am stuck having to fork out $60. It all adds up when and you get nickel-and-dimed building this stuff. 

  • Pixhawks are very reasonable these days. ebay has then for less than $60 with free shipping. I have one if the latest V2.4.8 and have flown it all summer with no problems. APM is very old hardware technology. I upgraded everything a couple of years back.

    Developers just don't have time to continue supporting such old hardware.

    .

  • Shucks, I just bought an old APM thinking it would work. How much horsepower do you need to calculate a position and move two servos? Seems odd that EKF is needed to position the antenna. I think the world has gotten to complex and we end up with Rube-Goldberg machines. NASA went to the moon with 16k of ram. What is going on here? 

  • Developer

    thanks Hugues!

    Hugues said:

    Hi,

    Made this explanation video for Arudpilot's antenna tracker:

  • Developer

    Hi Vladymyr,

    you probably found already that is true. The APM 2.x boards do not have anough horsepower to run thinks like EKF and it takes to much work / time to backport everything to avr branch. Developers resources and time is limited.

    You need a pixhawk (2) or linux board to get latest Antenna tracker working :)

    Cheers

    Vladymyr Kondratiev said:

    Hello Colleagues!

    APM 2 not compatible with Antenna tracker 1.0.0 firmware?

    When I flash my old APM 2.5.2 with Antenna tracker 1.0.0 firmware via Mission Planer and then open terminal I see 0.7.2 version :(

  • MR60

    Hi,

    Made this explanation video for Arudpilot's antenna tracker:

This reply was deleted.

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