Yaw shaking after good flights

ArduCopter Copter 4.1
1

Hi

I have a quad that was flying reasonably well, even before a fine-tuning, see log 1. (I used parameters that another identical quad)

After the previous log flight, he started to rattle and shake only the yaw. See log 2.

The problem persists even flying only in stabilized mode flight. Looking at the log, I didn’t find any significant vibrations, and YAW vs. DesYAW actually appear pretty different, even without touching the yaw stick after takeoff.

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Any ideas? :slight_smile:

log1 - flying ok: https://drive.google.com/file/d/13nZLtDqFE3bdght32Mux2yrDwjyvLEMO/view?usp=sharing

log2 - shaking flight example: https://drive.google.com/file/d/1NkeIGOJ8AgWrDGgRQ-icTI_jH3MEZcj-/view?usp=sharing

ps: I checked the hardware, and it looks pretty ok.

2

You have a problem with your compass, sometimes it goes crazy although you don’t raise the throttle. So maybe the problem is due to wiring or an electronic device/regulator very close to that compass.

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3

Thank you David! Indeed I will check that.

However, did you see that the flight mode was Stabilize? In stab, the compass should not interfere.

4

I’m wondering why IMU0 Z Gyro is so much noisier than IMU1?

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From my H743-Mini flown in the office just now:

Mini Gyro Z
Mini Gyro Z3310×1033 126 KB

5

Hi Dave, nice catch! Thanks.

Indeed I am checking other quads with the same board, and previous flights, and such discrepancies are not usual:

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Here is yet another test with problems:

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I notice lots of “EKF3 IMUn in-flight yaw alignments” and “yaw inconsistencies by X degrees”:

Do such alignments are connected to the compass, or could they be connected to the IMU discrepancies?

Another question: Do you know if both IMUs are in the same SMD?

ps: Does the EKF uses the both IMU at same time?

6

I typically see those as Compass problems. I have a small quad with an H743-mini and I occasionally see those messages and assume they are compass problems. It’s tight quarters on that craft and I use a Li-ion battery.

They are separate devices.

I believe the data is fused from both IMU’s but not absolutely sure about that.