3D Robotics

Smart RTL comes to PX4

When it's time for a drone to fly itself home, we for years settled for a a straight line back, "as the crow flies". That's obviously inadequate, since there could easily be a tree or large building in the way. So 3DR improved that with Solo, with the "Rewind" feature, which finds the shortest path back through the known-good area that the drone has already flown through. 

Now that same technology is coming to the open source PX4 flight code. A preview is shown above. Smart.

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  • Could this be applied to Ardurover to RTL on the previous path it took to get there? Backtrack?

  • Hi, I am currently using the Android version of Solo for flying my Solo so it must be ver 2.3.0. I believe when I set up the new vehicle with firmware ver 2.4.0 I saw an option about the REWIND feature being on or off, and the distance to use. I believe it was set to 0 and Off. When flying the vehicle I did an out and back arc. When I pressed the button to RTL i saw the word REWIND on the screen and the vehicle flew away from me as if to rewind its flight path. I pressed pause and landed manually. I have seen other reports of not being able to disable this feature. How can this be ??

    I also can't find any rewind setting now on the Android device either. Also confused by this ??

    Hope you can help. Thanks

  • 3D Robotics

    Tom, that is more or less correct: we developed it on the iMX6 companion computer using a variant of Dronekit, not on Ardupilot. In general, most of our "smart shots" and other higher-level navigation functions are implemented above the flight code, either on the companion computer or on the mobile device, for portability. 

  • Developer

    Annoying that it was developed on the Ardupilot platform but kept private (which is fine) but then ported to be "open" to PX4 and never exposed the closed ArduPilot version. I realize that it was probably developed on the companion computer on APM then refined further in PX4, but still annoying life cycle.

    Anyhow, more features the better! Thanks for sharing, ChrisA.

  • 3D Robotics

    Yes, that Total Energy Calculation (including wind) is now standard in calculating the battery-low failsafe trigger. It's less of an issue with copters than planes, since they're less affected by the wind, so it hasn't been as much of a priority until recently.

  • Moderator

    This feature was standard in Attopilot along with RTL based on power left vs winds aloft. So 2009 ;-)

  • Developer

    It's based on distance.  Default is 60 meters of flight path retracing after lost link.  Supposedly this distance is user configurable in parameters.

  • Fascinating use of the recorded data stream to create a logical RTL path. 

    I thought Solo's Rewind feature was only distance based, along the prior flight path, and then "as the crow" flies back to Launch?  I'm on Android, so I'm not fully sure how the feature works...other than what people with iOS have said.

  • Ah, nice that PX4 is doing it Open Source, hopefully this means we can get this in Arducopter since, I believe 3DR did not do theirs open source, it's actually running on the iMX6?

  • In your video, it seems to pass through a flight path intersection (Line WP3-WP4 crosses Line WP1-WP2), then it takes a new route to get to another intersection (Line WP1-H crosses Line WP2-3). Why is that? I would call that "uknown" airspace. Is there some kind of corridor width parameter for the "known good area", or is that a function of WPNAV_RADIUS (or, poor GPS reception/accuracy for part of the flight) in this case? 

    Good feature :-)

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