APM flying a search pattern with a SkyWalker


After yesterdays transmitter failure, we flew the SkyWalker again today with Jacks Spektrum transmitter. This time everything went very well, and we successfully flew a search pattern over the CMAC field.

The flight we did was:

 - takeoff in fly-by-wire-A mode
 - switched to GPS loiter, worked well
 - switched to full auto, and flew a "mow the lawn" 18 waypoint search
   pattern over CMAC

The plane flew beautifully and the APM behaved perfectly. The audio feedback from mavproxy was really useful (it called out the waypoint numbers automatically during the flight for example). The wind was quite strong, and the SkyWalker coped well, although its speed upwind was affected quite a lot. From the GPS log, the upwind speed in auto mode was around 21km/h, whereas the downwind speed was around 48km/h, which means we were fighting a 27km/h wind. The upwind track ended up with a lot of curves in it, whereas the downwind tracks were fairly straight.

Tracks for the fully automatic part of the flight are here:
The planned search pattern is here:

as you can see, the wind really pushed it off course!

There are a few photos here:

and a video of the auto-search here:


We flew with 2x2200mAh 3S LiPos wired in parallel, and after the plane landed we measured the amount of charge the charger would put in as around 900maH per battery. From that, we estimate we'll get around a 1hr flight time if we switch to a 5000mAh 4S battery.

We're now planning on adding the pandaboard and ptgrey camera this week, and we will try a search pattern with the camera in the SkyWalker next weekend. That will give us the image data we need combined with full telemetry (attitude, GPS, altitude etc) to get back to the image processing and 'find Joe' task for the outback challenge.


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  • Thanks, andrew, for your prompt reply and information. Best wishes to see more great results from you!
  • Developer

    Hi Alex,

    I'm always using the latest APM 2.x svn tree - I like living on the bleeding edge! I also have a few minor local patches, which are in my git repo.

    I've just finished the re-build of the SkyWalker to add the pandaboard, camera, USB hub and SSD. I'll post something about that build soon.


  • Hi Andrew, your work is excellent! Congratulations for the successful flight!

    May I know that which software version you are using to realize this waypoint flight? Could you pass me a link? Many thanks.

  • Developer

    Hi Doug, thanks for the tip on change speed! What I'd really like to add at some point in the future is automatic detection of this sort of condition and for it to cope with changing wind conditions by itself, trying to optimise the flight for good photos. We will have a quite powerful onboard computer (a pandaboard), so one possibility is that we detect this sort of condition there, and use mavlink parameter set commands between the pandaboard and the APM to change the APM flight parameters. We'll experiment a bit and see what works.

    Hamish, this isn't our final UAV platform. We tested our bottle drop mechanism quite a while ago and it works very well (see our various drop test photos and videos on our site). We'll combine that with the rest of the components for full mission testing in a future part of the project, using a much larger plane than the SkyWalker.

    SciFly, we're using the current SVN version of APM 2, plus a couple of trivial local mods (see my git repo for the exact code). We used my command line GCS, mavproxy, which is based on pymavlink to control waypoints, mission control etc).

  • Nice job!

    What version of MissionPlanner/APM code did you use for this mission??

  • don't you need to drop joe a water bottle or something?

  • Developer
    Tridge, I have been using the "change speed" command in missions.  That should be very useful in this type of mission to change your airspeed for the up and down wind legs.  Expect a bit of ballooning or diving at speed changes - you might want to move your waypoints out to give the altitude room to recover if altitude hold over the search area is critical.
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