Discussions

Problem in pitch shake

Posted by zheng jishi on November 30, 2014 at 10:53am

3691164472?profile=original

Hello,everybody here,there is a problem in my flying wing plane x8:


The plane takes off by the launcher.After the auto tune of the PID,the config file is attached below:

config.param

And the flight plan is include in the wp file:

wp.txt


The log file :2014-09-26%2007-33-58.bin

After the taking off,the shake in the pitch shows as follow.Can anybody help analyze the reason.Thanks!

3691164416?profile=original

2014-09-26 07-33-58.bin

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Replies

  • Stewart Loving-Gibbard June 18, 2015 at 8:27am

    I had this problem and eliminated it by switching to ELEVON_OUTPUT from ELEVON_MIXING. I believe there is a bug related to the behavior of the elevon mixing mode; the developers have clearly marked the elevon mixing feature as deprecated in 3.3, so it is unlikely you'll get help from them about this.

    Now, in fairness, I also switched from APM 2.6 to a Pixhawk at the same time, and I went from Plane 3.2 to 3.3. So this is hardly a controlled experiment I conducted. But everyone else who has complained of this issue is running ELEVON_MIXING, not ELEVON_OUTPUT, including Zheng here. (Has anyone had this problem in ELEVON_OUTPUT? Correct me if so!)

    I hope this helps. If you try switching modes, please reply and tell us how it went. This problem haunted me for weeks.

    • T0nimas > Stewart Loving-Gibbard December 22, 2015 at 10:38pm

      I have the same problem with ELEVON_OUTPUT (the new sytyle) with a X-6 Skywalker. The first time appeared the problem because there was slop in my elevon linkages. But a few days later I have registered the same problem, and now I sure that the linkages are fixed.

      I used V3.4 Plane. 

      Any ideas to improve this behaviour?

      • Moderator
        Graham Dyer > T0nimas December 23, 2015 at 12:00am

        Have you done an autotune?

        There is another phenomenon called "zagi flap" caused by not enough stiffness in a foam wing, this is an oscillation when a wing goes fast appearing as if the wing tips stay stationary and the center flaps up and down. It destroyed a wing of mine some years ago flying too fast. http://www.rcgroups.com/forums/showthread.php?t=20992, not sure if this is the problem in these cases but all my flying wings have flown with APM:Plane with no sign of this happening.

        • T0nimas > Graham Dyer January 19, 2016 at 9:44am

          It was an structural problem (the carbon beam was partialy broken) added to bad connection in the ESC. The solution has been a new frame and new ESC. 

          However, now I have problems with take off (I attach the log). When I do a handing launching the plane "overcompensate" the roll (not the pitch as before), and the plane enter in stall.

           

          Maybe this problems is related with my first problem?

          Thank you!

          2016-01-15 10-05-03.7z

  • Luis Carlos Barrios Fedechen March 10, 2015 at 1:48pm

    Hi...I have same issue...you find the problem???

  • Moderator
    Graham Dyer December 1, 2014 at 10:37am

    Try increase your Pitch_I to 10% of P (so make it at least 0.120). Also make sure there is absolutely no slop in your elevon linkages

    • zheng jishi > Graham Dyer December 1, 2014 at 2:27pm

      hi,Graham,

            Thanks for your reply,I will change the Pitch_i and check the linkages.

             In auto mode,my plane shaked when it climbed to the height(from 0m to 300m).After it reached the height( 300m), it stop shake.

             If  I swith the mode from auto to manual,it will stop the shake.

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