Gimble shake error

John235 · Feb 1, 2019

I've been grounded by weather for several days and finally could no longer take it. Took my MP out for a short run. Temp 26F, wind calm. UAV app says calm to 500 ft or so. All equipment warm inside house until takeoff. Took off to 200 ft and flew out across the fields. Started to get wavering in the image in brief waves, much like looking through a moving drop of water on a window (no rain or snow). About 2 minutes into flight, I got a gimble shake warning that stayed on the screen several seconds. Dropped altitude to 150 ft and returned home, hitting RTH after coming half way back. AC landed itself perfectly.
Can a wind gust cause this? I live in the mountains of PA, where wind can gush off the surrounding peaks, so I wonder if that was it, even though the the wind was generally calm.
Checking the flight record, I see a small "jag" in the flight path at about the time of the warning. That was followed by a curve in the flight path while I thought I was flying straight. The return home at 50 ft lower was straight, but does show a couple of very brief "image wavers". Should I worry? A week or so ago, I had a "gimble freakout" that I posted about, so I wonder if the incidents are related.

Mossiback · Feb 1, 2019

Are you using stock props?

John235 · Feb 1, 2019

Using the Platinum pro props. Had to reset my gain to 88,88,88,100. Tried 89, but still got gimble shake. That disappeared at 88.

Mossiback · Feb 1, 2019

You should be okay. I originally had no gimbal shake when I put the MPP props on my MP but then it started happening on windy days. Gain to 90 fixed it for me.

Mossiback · Feb 1, 2019

I found this video that is a bit wordy but explanes it well.

John235 · Feb 1, 2019

Mossiback said:
You should be okay. I originally had no gimbal shake when I put the MPP props on my MP but then it started happening on windy days. Gain to 90 fixed it for me.

I had found that video, and set my gain indoors. The MP was a foot from the floor and shake stopped finally at 89. On my first outdoor flight, I heard a whine as I lifted off. The gimble was shaking so I tweaked it to 88 and it stopped. I figured being indoors so close to the floor may have fooled me. Several flights went fine, until this weather grounded me. That is why my first suspicion was the wind, not the props. Your reply has me thinking that 88 may be an over correction after all, and I am experiencing an "under oscillation". What do you think? I will continue to watch this in varying conditions. I may also try tweaking the gain a point or two to verify my settings. I did not change the height gain from 100 because the video did not, but should I tweaked that too?
Another thought is that I could go back to 100 and put on my DW carbon fiber props and recalibrate gain. My stock props are broken from a minor end table encounter indoors so I cannot use them.

Mossiback · Feb 1, 2019

John235 said:
...has me thinking that 88 may be an over correction after all, and I am experiencing an "under oscillation". What do you think?...

Since according to the video the oscillation was caused by props being too efficient or reactive, I doubt if slowing down the gain too much would cause a vibration. It seems like it just would make it more sluggish to respond.