Dropping a Rover from Hexacopter - Part II

As a follow up to an indoor test we did a about a month ago (blog post here), Assistant Professor Nagatani-san of Tohoku University, Izu-san of EnRoute (a primarily Japan based RC company) and I tested dropping a 2.5kg rover from a 4kg Hexacopter outfitted with an APM2.5 running ArduCopter 2.9.1.  The test was done on the side of a semi-active volcano, Shinmoe which is in Kyushu, Japan.

The flight was all in Loiter mode with the release of the Rover via a servo controlled by the Camera Shutter function attached to channel 7 on the transmitter.  The pilot (me) was positioned right near where the video was shot from.

Basically it worked but there we hit a number of issues:

  • AC 2.9.1's Loiter has a 5m radius deadband meaning it moves back to it's original target unless you move more than 5m away (from the target).  This meant that repositioning the copter precisely was quite difficult.
  • As it was shot on the side of a Volcano at >1100m elevation, the wind was relatively strong and pushed the copter around at times.
  • the release mechanism for the rover was slightly damaged in transport meaning it took multiple attempts to get it to release.

Next time we will try to do it fully autonomously.

We also took the opportunity to fly a separate large Quad outfitted with a 10000mAh battery up for a view of the crater.  The flight took about 12min but it could have flown at least another 5min.  Problems we hit included:

  • Like the large rover-carrying-hexa this quad had very large propellers which could be caught by the wind at times meaning  the controller had a lot of work to do to keep it upright at times.
  • Arducopter 2.9.1 has a bug in that it proceeds to the next waypoint once it's reached the target lat/lon.  This is fine for mostly horizontal flights but it's serious trouble for a flight like this in which the vertical component takes longer than the horizontal.  The solution was to set the target take-off altitude to 150m and reduce the WP_SPEED to 2m.  We ended up overdoing it so we flew the mission higher and more slowly than necessary.

Still, it did the mission as planned.

All feedback welcome!

Views: 1194

Tags: ArduCopter, DIYDrones, EnRoute, Hexacopter, Rover, Tohoku, University

Comment by Jiro Hattori on March 15, 2013 at 4:25am


Congratulations to open research and educational programs by multicopter autonomous mission.

How is the wind around mountain?

The heavy vibration on the video brought the weakness of such a big Hexa in the wild.

Anyway, you made it:-)

Comment by Randy on March 15, 2013 at 6:26am


    The wind was very gusty, I heard over 10m/s at times.  It was very variable and difficult to predict.

    It's was a bit of a rare chance to get permission to fly that far and high and brought home to me the need to change how we handle the waypoint to deal with it all in a more 3D method.  Currently the horizontal and vertical components are handled quite separately.

Comment by Carl La France on March 15, 2013 at 6:27am

thanks for sharing you could really see the load come off the hex when the rover dropped . Would it have been possible for it to land with the rover release it then take off with out it . you are always trying some thing new 

Have a Great day!

Comment by Randy on March 15, 2013 at 6:43am


     The ground is very sloped so I don't think the copter would have been able to land but getting close, perhaps with the help of a sonar would have been better.   I didn't make any special changes to the ArduCopter code for this test.


Comment by Carl La France on March 15, 2013 at 7:05am

 I thought it was pretty cool the way it was . You would not want to risk dinging a prop in the sloped ground . I was just wondering ?" In the future?" could a hex  land and take off again after picking up or droping off an object or package  like the rover . You are doing Ground breaking stuff! Congratulations 

Comment by Carl La France on March 15, 2013 at 7:06am

On level Ground?

Comment by Randy on March 15, 2013 at 8:07am


     Thanks a lot.  Dropping the rover after landing on level ground wouldn't be too difficult I think.  Picking it up again would be much tougher but mostly because of the accuracy required to ensure that you're right on top of it while also ensuring that you don't step on it....but somehow do-able I think!

Comment by Rob_Lefebvre on March 15, 2013 at 8:44am

Nice work Randy!

I think recovering a machine will be possible in the near future.  Using PX4Flow for precision ground targeting, and OpenGrab to grab it, you wouldn't have too much trouble with the recovery.  As long as you don't "step on it", the OpenGrab would allow more leeway for the grasping operation.

Comment by earthpatrol on March 15, 2013 at 10:18am

Bravo! That's pretty darn cool. Really enjoying watching the technical progression of the project. Upward and onward.


Comment by John Arne Birkeland on March 15, 2013 at 11:00am

Regarding picking up the rover again..Just land the copter, then drive the rover under it and grab..


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