Y6 with APM2.5 Arducopter 3.1 rc5 Autotune Problem

Hi,

last week I tried autotune with my Y6 copter. With my tricopter it worked so great, that I was expecting a good result with the Y6.

At some point the copter did some strange movements and nearly crashed to the ground. I could recover it by taking over controll and did an emergency landing in a field.

Ii was very foggy that day and after the flight, the copter was pretty wet. So I thought, it could be some issue caused by the wetness.

So I did not pay to much attention to that.

Today I took out my Y6 and tried autotune again as it was dry and no wind today.

I started autotune and it began to do the rocking over roll and then over pitch. Nearly at the end of the pitch session, it became really scary. The back motors nearly stopped for several times what led to very scary movements. I had enough height and good nerves and so I let it happen. It was exactly the same as it was last week when I did autotun in foggy conditoins.

After a few of this movements, it stopped. Then I flew a few rounds, just to give the compass same data to calibrate and then landed, disarmed and switch off autotune to save the values.

Then tried the new settings and was really disappointed. the copter was terribly shaky.

At home I looked at the PID values and saw some really strange values.

I attached the PID settings before the autotune (Defaults with 3.1rc5 Y6) and after the autotune.

I also attached the logfile of that flight.

I mam just uploading the onboard video. Will link to it, when it's all up.

Hopefully someone could find out what's going wrong with this autotune.

preautotune.JPG

postautotune.JPG

2013-11-15 17-49 4.log

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Replies

  • You probably have the answer to this already, but you can search for "autotune esc sync issues" to find a complete explanation of the issue.  Also the Marco Robustini sync problem video at https://www.youtube.com/watch?v=0lRTN5o4UCM

    Best

    Richard

    • Developer

      Hi Richard,

      Thanks for offering help here but this isn't the esc sync issue. This is the large flexible mass issue with autotune.

      • OK thanks Leonard, I saw his initial comments about some motors nearly stopping.  But yes there looks like a lot of compliance between the airframe and the extended mass of LiPo/Camera based on the photos/video.  Thanks again. Richard

  • Developer

    Hi Arbo,

    I don't see new discussion posts but I do reply to any autotune questions on the latest release thread. That is how I found your post from 9 hours ago (about when I went to bed last night). I am also a single father with 2 children under 3 years old and my hobby has to come second. So you will have to forgive me for the delay in answering your question.

    You are correct that Autotune has not worked for on your frame. I have seen this problem before and I believe it is caused by an overly flexible frame or overly soft vibration isolation on your APM. I would suggest that you see if you can move the arms or any of the center plates and check that the APM feels solid in the way it is mounted.

    Other issues that can mess up Autotune is an incorrect CG,  props being too large for the motor and battery combination, and letting the copter build up too much airspeed during the test.

    If you post some photos of your frame here I may be able to make other suggestions.

    Now that I have replied to your post I should get an email when you reply.

  • No idea?

  • Here is the onboard video.

This reply was deleted.

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