Discussions

Pixhawk cut throttle moving from stabilize to loiter?

Posted by Matt on May 10, 2014 at 1:25pm

Took my F450 quad out for a little flying today, switched from stabilize to loiter and the throttle went to maybe ~10% for 3/4 of a second? It was up high enough that it recovered in loiter mode. GPS in the log says it had a lock.. Any ideas what happened? I'm running 3.1.3.

18.BIN

You need to be a member of diydrones to add comments!

Join diydrones

Email me when people reply –
Follow

Replies

  • Developer
    Randy May 15, 2014 at 3:38am

    Ok, I looked a little deeper and I suspect Matt's altitude drop was larger than 1m.  I think I got that from the github issue raised.

    The vibration levels are throwing off the inertial nav alt.  Below is a graph of the inertial nav alt vs baro alt and you can see they're 30m off.  This would make alt hold performance terrible!  So, best to sort out the vibrations!

    3701735264?profile=original

    • Matt > Randy May 18, 2014 at 6:28am

      Tested out alt hold this morning, got much better results, the quad didn't move at all when I switched over!

      Here is Alt and BarAlt:

      DQmkydH.png

      I suppose we can consider this matter resolved, simple user error, thank you Randy!

    • Matt > Randy May 17, 2014 at 5:52pm

      Thanks for your valuable information. I added some better dampening material below the pixhawk, and switched to some better props (APC), here's before:

      Gawv9BR.pngand after:

      vToQkzY.png

      A little better I'd say? I was using some cheapo props from when I was still learning/crashing a lot. It was time to upgrade to something a bit better quality. I'll be able to test the altitude mode more tomorrow.

    • Matt > Randy May 15, 2014 at 4:41am

      Thank you for looking into what turns out to be operator error :)

      Right now the pixhawk is suspended using some doubled up pieces of double sided foam tape: http://imgur.com/4IYcIbp

      I'm sure jumping to something like a gel sheet would help? http://www.amazon.com/gp/product/B002U2GS2K/ref=oh_details_o00_s00_...

  • Developer
    Randy May 15, 2014 at 3:32am

    I've had a look at the logs and two things jumps out.  The Z-axis vibration levels are very high during the very aggressive climbs.

    3701735126?profile=originalThe 2nd thing is that it looks like Loiter is being engaged while the vehicle is climbing at 4m/s.  That's quite extreme really and it's not too surprising that the altitude controller reacts aggressively (i.e. drops the throttle to minimum) in an attempt to get the climb rate under control.

    3701734851?profile=original

    I'm not saying we can't make it smoother but a drop of a 1m under these circumstances isn't too bad!

  • Andre K. May 13, 2014 at 1:30am

    This is "normal" - the transition from not-altitude controlled modes, to altitude control behaves this way.

    It's how ArduCopter  does it - regardless of hardware it run on.

    • Alan D > Andre K. May 13, 2014 at 2:03am

      I get this, typically when going into loiter, and also if I hit the max height fence.

      Always quite worrying when it suddenly goes silent...

This reply was deleted.

Activity