Pixhawk Vertical Fly Away

I recently completed my hexacopter (Pixhawk, AC 3.2.1). Test flights in Stabilize, AltHold and PosHold were acceptable to me ( a beginner), other than the fact that every once in a while the copter would jump up 1 or 2 meters. These flight were all done in my yard, so I maintained a height of about 3 meters and flew slowly. I check the logs and vibrations etc. seemed OK (to me - anyway).

Today I took the copter to a large field to attempt an AutoTune. Before I started the Tune, I flew around with a little more "vigor" than I had in the past. I was almost immediately rewarded with a vertical jump of about 3-4 meters. I was able to get her back down with no problem. Over the next 6 minutes this happened 3 more times. Looking at the log, these jumps took place a 1+ minutes, 2 min, 3-1/2 min, and 7 min.

The log seems to show that the problem was caused by AccZ vibrations. If I am correct, my question is, what could be causing the vibrations and what steps should I take to eliminate them? I have checked everything. The Pixhawk sits on Kyosho Zeal (sp). It all looks OK and I have followed all the usual instructions.

Thanks

2015-06-04 10-37-02.bin

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Replies

  • here you have lots of information about vibrations http://diydrones.com/forum/topics/vibration-isolation-and-dampening...

    but your problem looks more a hardware problem than only isolation

    3702020723?profile=originalcheck your props motor balance

    check your frame: rigid, symetry, etc. if possible post photos and description of your copter

    • Thank you. I'll definitely study your link.

  • Vibrations are a really issue. I have never been able to get them under control with gel. I use a variety of the rubber ball suspension platforms available and most seem to work. Everyone seems to have different ideas on this subject.  I think it depends on your frame design and how much vibration you have to deal with in the first place.

    Also you did not mention the mode you were in when you were flyng with more "vigor". I think there are a lot of fly-away events that are due to being in modes that require GPS, like loiter etc, and not having an adequate GPS quality. It is not just a matter of 3DLock, the hdop and the number of sats really need to be at or better than recommended or else a short GPS glitch can cause a failsafe which can do surprising things if you are not expecting them.

    Mayehem,

    Shooting up 20-30meters sounds like a RTL failsafe. It will rise to the altitude set in parameters, 150ft and head home. If you are not expecting it, the jump up to safe return height can seem like a fly-away when in fact it is just doing what it is supposed to do after a failsafe.

    • Thanks - I was in PosHold mode. I re-did my FC mount today. I'm using rubber balls - looks very promising.

  • The same thing is happening to me except it is skyrocketing up 20-30m. Very scary. Stabilize mode to get it back under control.

    Going to start back at the basics and check prop balance and everything to frame rigidity. Pixhawk sits on Zeal as well. No problems before.

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