Unstable yaw angles in octa frames

ArduCopter Copter 4.1
1

Hello,

  1. While I tested octa frames, I found that yaw angles are swung.
    image
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I also found such strange yaw angles in hexa, hexa-cwx, octa-cwx, octa-dji, deca, dodeca-hexa, octa, octa-quad, and y6.

  1. The deca-cwx, hexa-dji, octa-quad-cwx vehicle could not takeoff and just immediately hit the ground.

Edit: I could not find such unstable yaw angles in Copter 4.0.0 version (49693540bd555a44d30fc33366b1b8a24977e429).

2

Hi @KimHyungSub,

I think you’re only seeing this yaw oscillations in SITL right? This was reported a couple of weeks ago as well and we confirmed that it is just because we modified the SITL model but haven’t updated the tuning parameters (in SITL).

We don’t think you’ll see a problem on a real vehicle.

I’ve added "improve SITL yaw tuning " to our 4.1 issues list.

3

Hi @rmackay9.
Yes, I only saw the yaw oscillations in SITL.
I check the PR to fix this issue. Thanks!

Edit: I tested multiple frames in ArduPlane and noticed that this issue also exists in ArduPlane (using SITL).
I am not sure whether this is known issue or not. Just in case, I would like to describe the issue in here.

  • plane-dspoilers - segmentation fault
  • plane-jet - roll and pitch oscillations
  • plane-soaring - unstable pitch angles
  • plane-tailsitter - Gyros inconsistent / could not take off
  • quadplane-tilthvec - roll and pitch oscillations
  • quadplane-tilttri - roll and pitch oscillations
  • quadplane-tilttrivec - roll and pitch oscillations
  • quadplane-tri - roll and pitch oscillations

The below figure shows pitch angles when I tested plane-jet in Copter 4.1.0-beta3.

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image958×513 23.1 KB

The below figure depicts pitch angles when I tested plane-jet in Copter 4.0.0.

image
image958×511 23.1 KB

Logs: https://drive.google.com/drive/folders/1JujcvBHMsxVf0qvXgDqxJGdSojo6e1Np?usp=sharing

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4

@KimHyungSub,

ok thanks for the report. I think for this some of the ATC_RAT_xxx parameter gains will need to be reduced. Sorry to “pass the buck” but I’ll leave this for the plane guys to fix. Hopefully their beta testing will start in the next couple of weeks.

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