APM 2.5 RTL aileron & rudder random movement

Posted by Marcel on June 16, 2013 at 5:11am

Hi, I am seeking advice on some strange behavior.

After configuring the APM 2.5 Board to my bixler, the manual and stabilize mode seem to be fine.

But when I start RTL mode on the ground for testing purposes, the ailerons start jumping around for about one second, before going into position. This behavior appears to be happening repeatedly after some seconds... Does anyone have a clue what the reason could be?

If needed, I can upload a video

Thanks, Marcel

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Tags: rtl, ailerons, jitter
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Replies

  • 300km
    moglos August 15, 2013 at 2:41am

    I've had the same/similar thing. I posted about it here, video included.

    http://diydrones.com/forum/topics/apm-plane-2-74-released?commentId...

    My plane did it on and off for some time before I finally wrote the post above. I worried about it and reset the APM when it did it. I never had any trouble in the air.

    Someone asked if it was going into RTL because of a failsafe, and that's exactly what was happening. The twitching of ailerons and rudder is just what I'd expect as the plane is trying to RTL. (If the plane is at the home location, then GPS noise will make it think it is moving around the home location, so it will be moving the control surfaces to try and get home).

    I try to avoid it by switching on my GCS telemetry first (I have GCS failsafe set) but it doesn't concern me now (I'm just very careful of the propeller).

  • Richard Barndt August 9, 2013 at 10:45pm

    I have the same problem.  In RTL and Loiter modes (there may be other modes also, but the twitches do not occur on Manual, Stabilize and FBWA modes.  These are the only 5 modes I tested so far.), the aileron and rudder twitches randomly.  Have not flown yet.

    It looks like the aileron is the source of the twitching, and the rudder is twitching only because of the rudder/aileron mix.  The RUDDER MIX (KFF_RDDRMIX) is set to 0.500 (50%) by default.  That is why the rudder is twitching half as much as the aileron.  I set this variable to 0.000 (0% mix) and then only the aileron twitched (and the rudder stood firm).  So finding the source of the aileron twitch should solve the problem.

    I am using a Futaba T6J transmitter (2.4 GHz) in S-FHSS mode.  I tried a FrSky Delta 8 receiver in PWM mode (twitches happened).  I tried the Futaba R2006GS (twitches happened).  I also tried the FrSky Delta 8 in PPM mode (Ch1 input only on APM 2.6), and the twitch on the aileron was still there. So I don't think it is the input signal encoder.  Must be something else going on.

    I am running Arduplane V 2.74b.  Problem seems to be there whether connected to computer via USB or not.

  • Developer
    Bill Bonney June 16, 2013 at 8:31am
    It's impossible to tell. When you enter RTL the plane will try to head to the home location. At the home location it will loiter about that position. You cannot infer much unless its flying.
  • Marcel June 16, 2013 at 5:21am

    Here's the video link:

    http://youtu.be/NPkzZTh6rR0

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