New AQ build - flips after take off

[nikivan]

This is my 3rd AQ build and I am having some issues I have not experienced before. It is heavy lift quad in X configuration. Basically, the quad shows signs of instability as the throttle is advanced and at some point it flips. My initial suspect was the mixing table, but it is the same as another AQ I have with exact the same frame configuration and motor directions and that one works just fine. I am using the latest build downloaded from the wiki - aqv6.6.0-rev2. Static and dynamic calibration where performed, as usual. Speed controllers are ESC32. I am enclosing here a very short log file from the last flight (more like a hop). I'd really appreciate if someone could help solving this issue.

Thanks,
Nick

[chschmid]

Hi Nick

Hard to tell. It looks like a lot of vibrations. Are your props balanced well?
Could you post a some more information. Motors, props, board mount ect., photo.
Did you test with payload or just the "overpowered" platform?

Best
Christof

[nikivan]

Thanks for the reply. Yes, props are Groupner 12.6 and are well balanced (they balance better than APC). Motors are Avroto 770 KV, running smoothly. I've tested with simulated payload 3.5kg AUW (see pictures), as well as without additional weight - the result is always the same.

[Max]

Hi Nick,

The vibrations look to be extremely high once you throttle up. I doubt it could fly like that

Just a thought, but I tried basically the same motors (Tiger 2814-10) on a Y6 with reinforced 10x10mm arms and determined they simply couldn't handle the thrust levels involved even with perfectly balanced 10" props, just too much vibration (--I'm almost done rebuilding it with a new Rusty frame). Granted it would be worse on a Y6 with 2 motors per arm... but I think my arms were also shorter and perhaps stiffer than those Al tubes. Anyway, just saw those arms and motors and that was my first thought...

Cheers,
-Max

[nikivan]

Thanks, Max. Do you mean accelerometers' readings? They show noise in +-1.5G range. I had another AQ that was showing +-4G and it was flying fine. Besides, the motors appear to run smoothly. I've been using a set of Avrotos in my hexacopter for over a year and I am very happy with them. Do you think something else might be going on here? This is a foldable-design frame I was planning to use for travel. It is a lot of work to change the hardware.

[Max]

I was looking at the ACC readings, yes. Was this an actual flight with crash at the end? I was seeing the ACCs going nuts at the end, but perhaps that was the quad hitting the ground... Could be something else then. I did notice MOT_YAW seems to do something funny (avg. drops below zero) towards the end before the crash, even though you're not commanding any yaw. Don't know if it's related.

-Max

[chschmid]

Nick
I would also suspect the frame as to be not stiff enough for thrust and vibes. But its hard to tell where the ACC values are from. Maybe you try to fix the batteries to the frame as "mass dampener" instead of having them hanging in the rubbertube snippets. See what the acc read.

Best
Christof

[nikivan]

[chschmid]

I think it is the wrong way to go. But the P Term is the proportional part of the PID or maybe F to shorten the whole PID.

[LPR]

Nick

Could you post your PIDs and motor mix.
To help rule out that vibration is a problem you could try using a string to connect all the motors together.
I find I can fly very well with poorly balanced motors and props using a string to reduce the vibration the board sees.
I've had my quad fly very poor when I changed the board orientation 45 degrees and did not adjust the parameter for rotation of the board in the IMU.

Larry