Strange Vibration Issue

Hi All,

I have been chasing jello in my video for about seven months now. Somewhere along the line I've introduced a new vibration problem that I don't understand and haven't been able to fix.

In addition to the typical jello that is caused by prop/motor vibration, I am now seeing a kind of jitter in the pitch axis. It is not oscillation, as far as I can tell. It is more random than that. It happens whenever I give the aircraft horizontal stick. It also doesn't seem to be prop/motor vibration, but rather something else.

When I first noticed the issue I was in the middle of a series of gimbal mounting changes. At first I thought that there was some interaction between the airframe, flight controller, and gimbal vibration dampers. However, when I went back to an earlier version of the gimbal mount, that has almost no damping, the problem persisted. It also persists through autotune, and repeated motor/prop balancing efforts. I can't take the aircraft back to a state where it doesn't have this jitter.

The linked video, recorded on my goggle DVR, shows the problem. My FPV cam is hard-mounted to the airframe, so it is actual airframe movement that shows up in the video.

Has anyone ever encountered anything like this?

I've also included a screen shot of the Pixhawk's vibration log. It shows quite a bit of movement around the z-axis.

There is also a pic of the aircraft for reference.

https://www.dropbox.com/s/40s6hfy3pl17elk/Jitter_DVR.avi?dl=0

https://www.dropbox.com/s/i5xk6fxjkk8da7w/27m_s%20z-axis.jpg?dl=0

https://www.dropbox.com/s/3zx3nrp5anb276j/View%20of%20Aircraft.jpg?dl=0

Aircraft info:

ebay TBS Disco knock-off frame

HobbyKing folding arms

Pixhawk, APM3.3

Foxeer HS1177 on homemade mount

Feiyu Tech 2-axis gimbal on homemade mount

KDE 2315 motors

APC 10x4.5 MR props

Dragonlink Micro Receiver

ImmersionRC 600mW VTx

Cheap MinimOSD clone, The reason for the glitchy video in cold weather

Maytech PDB with integrated regulators

Multistar 5200mAh, 4S battery

Some other junk

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