FBWA Little or no control

Posted by Scott Fitzgerald on October 29, 2014 at 12:17pm

I am using 3.03 firmware on a 2.5 board in an elevon x-8.  The plane flies well in manual, stabilize and does a good job following waypoints in auto and rtl.  My issue lies in fbwa.  The plane is super stable and I have no control authority to pitch or roll the aircraft.  I have tried autotune with no success.  I have verified correct control movement on the ground.  I even tried upping the p gain to match the control throw of manual on the ground. When airborne, it behaves as if the "nudge" is working but no real control authority.  I feel that I am missing something simple.  I had this problem a couple years ago on an older 2.0 board.  I never got the problem solved.  I have restored all defaults and ran setup again with no improvement.  What am I doing wrong? Thanks in advance.

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Replies

  • Scott Fitzgerald October 29, 2014 at 3:13pm

    Yes those parameters are defined.  Great graphic.  I think I am using delta wing/elevon tx mix instead of flapperon.  I am not sure the benefit of using flapperon then setting up 2 mixes to accomplish the delta/elevon function.  I do have some of the elevon boxes checked in mp to make everything work right.  Maybe Ill start over using the graphic as a guide.  It seems that it should work either way?? 

     

    One last question.  If I have activated the elevon mixing function in the apm shouldn't I be able to leave the transmitter in a normal wing mode with no mix?  All elevon style mixing would be accomplished in apm?  I am understanding that if the mix is accomplished within the apm then none of those boxes need to be checked.  Is this correct?

  • Flying Buddha October 29, 2014 at 2:25pm

    @Richard Burd 2  Great illustrations, I have never seen those. @ Scott Fitzgerald Here is another place to get parameter files http://plane.ardupilot.com/wiki/flying/tuning/configuration-files-f...

    • Scott Fitzgerald > Flying Buddha October 29, 2014 at 3:06pm

      The parameters listed for the x8 are fairly close to default.  The plane seems to have good stability and response while navigating waypoints, just no override in fbwa.

       

    • Martin > Scott Fitzgerald November 9, 2014 at 11:15pm

      Hi guys, did any of the suggestions above fix the problem ?

      I have been helping a friend get a Talon V-tail APM:Plane working at the flying field, but he also has a situation of good manual mode control, but nothing happening in FBW-A. Auto-tune is not possible with no initial control. In his case the throttle drops to low in FBW-A and stays that way too regardless of TX throttle stick position. 

      Martin

    • Scott Fitzgerald > Martin November 10, 2014 at 4:47am
      Been working too much. No progress from my end. Next step for me is to go with elevon mixing out of the transmitter and into the apm. I still don't have a launcher worked out. When that happens I will be more active with this plane. Also purchased ezuhf the other day.
  • Flying Buddha October 29, 2014 at 12:33pm

    I had similar issues with my fx-61". Have you tried increasing the "MIXING_GAIN"? this worked for me. I know its not recommended to change while flying, but that's how I did it.

    link: http://plane.ardupilot.com/wiki/arduplane-setup/first-time-apm-setu...

    • Scott Fitzgerald > Flying Buddha October 29, 2014 at 12:40pm

      Thanks for the response.  I am using the elevon mixing in the transmitter.  I have also checked the elevon box in the mp setup page and checked all the boxes to make the controls and stabilization work the right way.  Is this correct?  I have never messed with the mixing gain.  How much did you increase it? Also, on the ground I can flip from manual to fbwa and have set the p value so that the controls move the same amount.  Shouldn't this be a good place to start?  It is like I have no stick priority over the stabilization.

       

    • Flying Buddha > Scott Fitzgerald October 29, 2014 at 1:06pm

      it sounds like you have the same issue I had. I ended up doing the mixing on the APM (no elevon mixing on the radio). I increased my to 1.0.  On the ground it looked like i was getting the same amount of throws in STAB and FBWA, but in the air is completely different. 

      I initially had the elevons set on the radio and found that I had more control with the settings when I did everything on the APM via Mission Planner. 

      I know we have different air frames (I have a FX-61), but I can upload (when I get home) my parameter file for you to compare. I still have a few more parameters to correct on the max bank angle, but everything else is rock solid.

    • Scott Fitzgerald > Flying Buddha October 29, 2014 at 1:13pm
      Thanks. The last plane I had same issue with was also elevon in the transmitter mixed. Will try mixing in the apm and see if it works.

      If anyone else has input please chime in.
    • Mossbackfarm > Scott Fitzgerald October 31, 2014 at 9:52pm

      I had a very similar problem with my FX61.  Turned off the transmitter mixing, upped the mixing gain to .8 or .9, and it was pretty much solved.

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