Quad copter started twitching hard

Had some vibrations problem (now seems to be fixed - tightened motor bases), however, while I was hovering, suddenly I noticed the quad was twitching badly (landed immediately).

I am no expert in logs, however, I did noticed some correlation between the battery voltage to the motors “jumping” (I think). I am using a Li-Ion 6S 6C battery.

I am using F55A 4in1 ESC with telemetry.

Attached log file
attached parameters file

Any insight would be much appreciated!

Thanks, Gal.

I have seen this behaviour in Dshot ESC when they have been calibrated as PWM.

When you did your ESC calibration did you select the correct Dshot parameters?

Hi @mboland, thank you for taking a look. I have never did a calibration, DShot doesn’t require it. Besides, this quad is flying for a few month without a problem.

I had a vibration problem, so I tightened my motor bases and did a test flight.

That’s where it twitched heavily. Initially I thought I have a vibration problem again but logs showed zero clipping

Screw shorting a motor winding maybe?

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@xfacta no, all is clean rotation.
I believe it is something to do with either bad configuration, or power problem.
I am no expert on logs, however I think the twitching shows in the log but I am not sure.

Gal, I have reviewed your log file and found where the problem comes from, but not what it is. I saw the twitching near the end of the flight and checked the desired roll/pitch with the actual roll/pitch. They followed each other as if the twitch was commanded by some thing. GPS glitch, accel glitch? First I checked the RC input from your RC receiver. The glitches came from the Transmitter or Receiver or some kind of RF interference affecting the receiver. I know it wasn’t you slamming the stick to the corners and returning to the exact same spot after a glitch of one sample point simultaneously on multiple channels. Some thing is seriously wrong with you transmitter/receiver system. I would not fly this system until this issue is fixed.

Set your loggin parameter to log while disarmed and try out things on the ground. Look at your RC inputs in your log and check for glitches. Try literally shaking things, jiggling wires connected to the receiver. Tap or shake the Tx. Some thing is loose some where. Then look at the log, RC inputs.

Hi @Greg_Fletcher,
Thank you so much for taking the time to review the logs!

Actually, after landing the fc made changing sounds like those made when changing flight modes (radio was set aside after landing) so before anything else I pressed the safety switch.

I open the frame on the workbench today and found that one of my 12V BEC was bad, it created a short when touched with a finger (so it might have something to do with the aforementioned issue), though might not.

So weird, now that I know where to look I shall do exactly what you have suggested and turn the logs on and see what gives.

Thanks a bunch,

@Greg_Fletcher I looked at the logs and when you know where to look its easier :grinning:

This is what I was looking at

and right at the end there is a message FS_RADIO_EVERYTHING_OK, where did it come from.

Tomorrow morning I will dive deep into it, the RX is R9, and TX R9M. will see.

Gal, That’s great news. I once had a glitch in my video system that only happened in flight due to vibration. A tiny short from a broken wire strand causes a voltage glitch. I have found that a wire directly soldered to a board will get fatigue failures right where the solder ends. The outer strands break and can short to the adjacent wire. I always use a pin connector instead of soldering the wire directly on a circuit board thru hole. Check all your connections thoroughly.

Good Luck!