Help me fix twitchi alt hold

Hi, i have a bit of a problem with altitude hold. I use latest 2.9.1b on my quad, but in alt hold mode it tends to be twitchy (moving up/down fast 10 cm range) and over longer period moves up/down bout 1,5m. https://www.youtube.com/watch?v=51mG9BLdqts&feature=youtu.be
Here's the log of last flight, first i flew in stable mode then i switched to alt hold. http://speedy.sh/rBppz/2013-04-14-15-29-1.log
Maybe someone can take a look and tell me what causes the problem Azz or baro or smth else.

Also, is it possible to tell from log how my pid's are tuned? It flies good in stable mode but maybe there is room for improvement?
http://img442.imageshack.us/img442/8399/pidsq.jpg

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Replies

  • Check your log, look in RAW - AccelZ, you will see a LOT of Z vibration.

    Strangely there is little vibration in the X-Y directions, but a lot of fluctuating vibration in the Z axis.

    Do you have soft props that are flexing?

    Is a motor loose or some other mechanical problem?

    As the AC2.9.1 used the accelerometers now for Z axis you will need to either 

    a) find the cause of the vibration in the Z axis or 

    b) isolate the APM from the frame to diminish the effect of vibration or

    a) and b)

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