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.
Replies
That is strange, as these settings should be there in the first place. It worked out of the box in most cases. Anyway, good to hear you made it work. I like your design - simple and effective. I see you made use of that green sheet folding machine in the background (I don't know the proper name).
Jakub, Your efforts are good and needed and I think your on the right path. I look forward to your changes when you get time and the weather permits. In the mean time I will continue to learn how this all works and hopefully offer something useful in the future.
Question about the antenna tracker - can you use continuous rotation (no feedback) servos, and can the tracker software support continuous rotation of the tracker its self (IE greater than 360 degrees?). I'm wondering if it uses the manometer for the angle calculations?
Thanks,
Yes you can, this is one of the reasons I got involved in development - I needed CR servo support. My tracker can rotate infinite number of revolutions (I use a slip ring for electrical connections)
This will be at long range, as in gps update rate wouldn't be an issue.
Thanks, it's super helpful of you!
I didn't make any measurements but from my visual observation (I still plan on mounting a camera with large zoom on my tracker) the accuracy should be within 1-2 degrees at long range. The biggest issue is compass that is not as accurate as other sensors, plus it gets affected by wires with current flow (every wire with current flowing through it generates magnetic field around it, thus it is recommended to twist positive and negative wire to zero-out this field). Maybe we could add support for encoder but that would require precise calibration on startup (either aligning the tracker base to true north or simply pointing it "manually" to remote vehicle to compensate the offset). I am assembling a simple tracker right now (I need something for testing) and I may mount a camera on it to evaluate the performance.
Jakub, Did your changes make it into the latest release available in the master-AVR? I don't see any of the changes you have referenced so I don't think they did. Would you be willing to share your source files with me and the community? I tried your version for APM 2.5 and it seems to work very well and I would like to understand what you did to make it work and maybe add to it if possible. Thanks.
Jakub, if you could create a pull request we can work to getting it merged into the main tracker codebase both master and master-AVR.
Thanks, Grant.
Some of my commits were pulled into master a few times and current versions use some of my changes. It is important to note, that I worked on the code in a hurry and not every feature made it into master either due to being unrelated to current pull request or simply not tested enough. All of my changes are in my github: https://github.com/rcairman/ardupilot
I am still new to git (I'm a Subversion guy) so it may be a bit ugly sometimes but most recent commits should work fine, especially branches dedicated to certain people.
Jakub, Thanks for the link. I have a couple of questions about some of the special feature branches you created and what you experience with the features are. Did you find that using the GPS altitude estimates for pitch better and more reliable than the baro pressure calculations? Just thinking about it it would seem to be more accurate but just asking someone who has tried both. Also have you had any adverse issues with setting up your pitch servo for CR and not having any limits on it. Seems to me that potentially you could have an issue with this without any limits. I have my yaw servo CR but my pitch is "position" with 180 limits. I noticed that you built a custom build to be able to choose an option for both but the main fork has one parameter for both. I am not apposed to removing the 180 limits on my pitch servo but just wondering what your experience is.
Thanks again for your input.
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