Slight wobble in forward flight
« on: July 28, 2017, 08:09:19 pm »
Hi everyone,

I have a 150 size, with cc3d and no matter what I do in the pids I keep getting this slight wobble as I fly forward. I can get it flying perfectly as far as turning and burning in acro+ but when I fly straight you can see this wobble in the video. I have it on all three drones that run cc3d.

Anyone know how to fix this?

My update rate is set to 490
I'm not using attitude mode at all just acro+

Re: Slight wobble in forward flight
« Reply #1 on: July 28, 2017, 08:47:38 pm »
Would you call it a regular timed oscillation or just random twiches?  How fast does it wobble?  Several times a second or less than once a second?

Are you adjusting Stabilization -> Advanced -> InnerLoop PIDs?

For a regular oscillation of several times a second:
First, save your settings (File -> Export UAV...).  For a test I would try multiplying (rate/inner PID) P, I, and D on roll, pitch, and yaw (9 numbers) (Stabilization -> Advanced) all by 0.75 individually.  It will not be as tightly tuned, but if that gets rid of the wobble, the you may find that TPS (also in Stabilization) (it scales PID depending on throttle setting) will help you with your old settings (before you multiplied by 0.75).

ernstock

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Re: Slight wobble in forward flight
« Reply #2 on: July 28, 2017, 09:21:23 pm »
So could this be referring to an effect that is noticeable in recorded image more than whilst flying ? (
"You can see this wobble in the video ")
 - a 'jello' effect ?
- if so , new props sorts it for me or better mounting of the recording camera

Re: Slight wobble in forward flight
« Reply #3 on: July 28, 2017, 09:53:09 pm »
CMOS cameras capture pixels one at a time and if the scene is moving say left to right, the top of a vertical pole will be in the middle of the screen, but the bottom will be to the right a little so the pole is not vertical.  If a vibration causes it to move left right left right (quickly) then the straight pole will curve a little like an S.  This happens to the whole scene and you get what is called a Jello effect.

Slight changes in the vibration frequency (motor RPM) can cause the Jello to move faster. slower or even stop.  Moving Jello stops and becomes a warped image when a small interger multiple of the page painting rate matches a small integer multiple of the vibration rate (say 3 to 1).

Make sure that Jello isn't your problem by watching LOS flight or using a CCD camera for your FPV.  CCD cameras don't have Jello because they are "global shutter" cameras that capture all pixels at the same instant.  I.E. the whole picture jumps left or right instead of e.g. the top part of the picture jumping left, the middle jumping right, and the bottom jumping back left.

Vibration makes Jello with a CMOS camera, but it just makes a blurry image with a CCD camera.

Re: Slight wobble in forward flight
« Reply #4 on: July 28, 2017, 09:59:31 pm »
thanks for the replies, I'm going to try lowering the pids a bit, someone posted a video of what it's like:


but nearly as pronounced, it's like the last 5% I can't seem to get rid of.

Re: Slight wobble in forward flight
« Reply #5 on: July 28, 2017, 10:02:19 pm »
It's not Jello for sure, I've dealt with that before, camera is isolated on vibration mounts.

Re: Slight wobble in forward flight
« Reply #6 on: July 29, 2017, 03:50:14 am »
Camera vibration mounts don't completely cure Jello.  Sometimes they even make it worse.

Mateusz

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Re: Slight wobble in forward flight
« Reply #7 on: July 30, 2017, 09:36:19 pm »
Looks like too high P term ? Check out this video