Weird motor imbalance signals I keep seeing in PX4 log

Flight Testing & Log Analysis
1

Hey folks,I’ve been running a bunch of bench tests on heavy-lift multirotor motors lately, and I’ve run into some confusing log trends that don’t fully match my lab data. Just wanna bounce this off everyone who flies custom frames with PX4.A few weird patterns I’ve noticed:

  1. Even after full ESC calibration, my flight logs still show small but steady RPM gaps between four motors during long mapping hovers. Is this mostly down to tiny rotor balance differences, or winding resistance inconsistencies I’m missing?

  2. When running spray rigs at near-max throttle for hours straight, logs show each motor heats up at totally different rates. Does uneven heat throw off PX4’s auto-thrust balancing enough to trigger false EKF vibration alerts?

  3. I’ve tried mixing two slightly different KV motors as a temporary fix once, and waypoint drift got noticeably worse. Can PX4’s built-in motor compensation really smooth out that mismatch, or is swapping matched motors the only real fix?

  4. Long-term wear seems to slowly loosen rotor magnets inside some motors. I’ve watched vibration numbers creep up flight after flight until saturation warnings pop up. Has anyone else caught this early just from log data before physical failure?

I’m trying to put together a simple checklist to spot motor hardware wear straight from flight review files. If you’ve got any similar weird log observations or quick fixes you’ve found, I’d love to hear your real flight experiences!

2

Provide a flight review log and I’ll take a quick look.
but a offset in motor output usually comes from either offset weight on the drone or yaw imbalance (e.g motors tilted)

3

Good point on CG/yaw — I checked motor tilt and COG already. The RPM gap stays consistent across different frames with the same motor batch though, which made me suspect rotor/winding variance.I’ll upload a clean hover log later today. Thanks for taking a look.

4

Here’s a log from one of my mapping flights. Quad around 5.5kg, 900KV motors, 10.5x5x3 props, 6S, position hold at ~40m.There’s a consistent 120-150 RPM gap between motor 1 and 3 during hover. Hover throttle is around 45%. I checked motor tilt and COG already, seems fine. Same gap showed up on another frame with the same batch of motors so I’m thinking it might be winding/rotor variance.Thanks for taking a look!

5

There is no flight log provided…

120rpm gap is not that much expecially for 900KV motor.