Y6 Copter-3.5rc7 Rc_out saturation, logs analysis

Hello everyone,

I flew yesterday a Y6A that had a “crash” at the end of the flight.
Copter went down quite quickly when one motor reached saturation (pwm to 1954 continuous).

What is surprising is :

  • Copter didn’t loose Attitude control,
  • Copter “ThO” reached maximum but motors PWM didn’t change ( average around 1600-1700) while only one motor (M5) went to max and reached saturation.
  • Copter didn’t loose Yaw control, so CW/CCW balance was correct even though the difference between PWM output
  • Frame is Y6A, so coax motors on each arms, then if thrust was needed to keep aLtitude, the bottom motor from the same pair should have increased as well, and if Yaw was needed other CW motors could have increased as well.
  • Pilot tried to recover in Loiter mode with max thrust with no change. RC3_in is max but nothing changed in motors output.
  • After the “crash”, no proprs were damaged, every motors can turn freely so no motor brownout…? Maybe Motor 5 overheated since it was at max too long but then again, copter should have detected the fall and maxed the paired motor?

Copter weight is 4kg while motors thrust are 800g/each (4.8 kg @50%, 11kg@100%) so plenty of room…

I would love any help in analysing this log / this issue since I can’t understand why copter went down.

Thanks !
2017-06-27 18-14-18.log (3.4 MB)

I would revisit the ESC calibration, but:

Set the appropriate values for MOT_PWM_MIN and MOT_PWM_MAX before ESC calibration.

Also set MOT_BAT_VOLT_MAX and specially MOT_BAT_VOLT_MIN to appropriate values for your battery (probably 25.26 and 22.2) and MOT_BAT_CURR_MAX (probably around 60A) to something reasonable for your setup considering the C rating of the batteries

From there if something strange happens we can easily try to pinpoint other issues.

I wouldn’t say that your setup provides plenty of room. The Mid throttle learning also “agrees” with me :slight_smile:

note: check if the propeller is correctly tightened. Just a “seen it already” hunch :slight_smile:

Hello Luis,
Thanks for your reply !

I have now set these params and redo ESC calibration as well.
The Hover Throttle is about 40% but we flew with quite some wind !
It should still be enough to lift the copter with only 4 motors.
I decreased the YAW Headroom from 200 to 50 now so I’ll have even more room to prioritize throttle over Yaw.

The real concern here is CTUN.ThO which goes from a average of 0.4 to a full 1.0 where the “saturation” appeared. I believe that with ThO maxed out, copter didn’t even try to increase others motors output. Can you confirm @rmackay9 ?
A “faulty” / “saturated” output should probably be weighted less and less over time (Intégrator corrector ?) in the ThO if DCrt and Crt differs a lot. What do you think ?

PS : I flew with the copter today and everything was fine. I believe it was a bug, a prop not tightened correctly (probably bot) or an overheating of ESC/motor … So a software related fix for saturation would be a real improvement. Maybe it’s not that simple to fix :slight_smile: