Strange behavior

Posted by Anton Khrapov on February 19, 2015 at 4:59am

Hi,

I have just finished re-building my hexa and on the first flight noticed a very strange behavior (which caused a big crash already).

First, yaw drifts. It happens all the time, and in different directions and with different speed too. I suspect it's something with EM interference, but why does it spin different directions?

Second, hexa does not respond to transmitter immediately after 5-10 seconds of flying. It's just weird, I try to hover and give it a bit of left-right and forward-back movement, but in some time when I try to pitch forward, hexa goes sharp left, then back, then forward. Or right. It looks like it tries to compensate previous movements first before responding to sticks. It's hard to describe, I'll try to make a video tomorrow. Do you think it's PID controller overcompensating?

I'm using standard PIDs, the frame is HK 650x6 with NTM 28-36 700KV motors.

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Replies

  • Luis Escobar February 21, 2015 at 6:59am

    I had an issue with transmitter response times while flying in a park which had a huge radio antenna set up behind me. The lag was probably less than a second delay but that made it really difficult to fly. It may also contribute to your yaw if you think it's caused by interference. Are you flying around some other antenna?

    • Anton Khrapov > Luis Escobar February 23, 2015 at 4:33pm
      I don't think there is any interference in the area I fly...
  • Anton Khrapov February 21, 2015 at 4:36am

    Ok, I think I got rid of some of the problems by moving PDB further away from APM and by straightening motors a bit. Just need to get PIDs right now.

    Here is another thing I found and I'm not sure if that's how it should be. When APM is connected to Mission Planner, the artificial horizon is not responding fast enough. Large changes are fast, but when I, for example, hold my hexa at an angle and then quickly put it flat, horizon moves quick first and slows down just short of level position. It slowly gets to level, but it takes a second or two. It looks like it overshoots a bit even. Here is a video: https://www.youtube.com/watch?v=EcXkoDZ63q0

    Sorry for the shaky and sometimes out-of-focus video, but around 7th second it's good enough to see the response.

  • Spencer Willis February 19, 2015 at 5:35am
    Maybe you are accidentally in Simple Mode?
    • Anton Khrapov > Spencer Willis February 19, 2015 at 11:21am
      I thought that might be the case but no, it's a standard stabilize or alt hold mode.
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