Unsolvable hot motors? [SOLVED]

I’ve been chasing down the cause of hot motors on this new build without success. I’ve tried different ESC settings, cutting PIDs dramatically, and lowering the filters. Nothing is rubbing against the flight controller. It’s a low noise build with dynamic notch filtering set up and doing a beautiful job according to the FFT graphs. Nothing seems to make a difference in motor temperature?

Here’s a log that I did after lowering the PIDs again to see if it would help, and it did not. It only made the quad fly worse.

Here are the vehicle specs
3kg AUW with standard RGB gimbal camera payload
6s Li-Ion 9Ah battery
600kv 2812 motors
35amp BLHeli 32 ESC with telemetry enabled acting as reference for the dynamic notch
APC MR 13x4.5 props
50v 1000uf cap on the ESC
mRo power power zero module
mRo control zero FC on 4.1dev
mRo Location One M9 GPS via CAN
Hereflow optical flow sensor via CAN
Herelink for telem/video
TFmini+ for front rangefinder
LW20 for bottom rangefinder

2812 motors are WAY too small for 3kg AUW lol. You will want something like 3536 910kv turnigy motors (which are pretty damn good) but they do 4s not 6s.

Wrong. You need to go a heck of a lot lower that 900Kv, and a PropDrive motor is the last thing you want to use. Any motor worth using on a multi-rotor aircraft will have a motor data chart, but crap airplane motors just show max current. RUN AWAY… You also need to calibrate the battery monitor, 'cause there is no way you are running 222 volts at 26 amps. That comes out to 5,772 watts.

I have a 680mm quad with an AUW of 3.615 Kilos.

I’m using 5008-325Kv motors swinging 1755 CF props on 6S. ESCs are Hobbywing X-Rotor 40A OPTOs. Each motor pulls 3.75 Amps. Grams of Thrust/Watt of Power = 10.95. Flight time using 80% of a 10000mAh 6S 10C LiPo is a solid 32 minutes.

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Ah yes I should have mentioned that they are 600kv motors.

I’d also like to clarify I’ve had a very similar build that did not suffer from hot motors.

I cannot find ANY 2812-600Kv motors. How about posting a link?

They are custom wound Brother Hobby Avenger V3. If you’d like some feel free to DM me.

I want to see a picture of this aircraft…

Perhaps 12" props would be more appropriate for those motors at that AUW.

That log is not of much value for determining tune. The pitch and roll demand is low (<10deg) but even then it looks poor with overshoot on both. Make another flight with more aggressive action.

Note: If you are done configuring the notch filter running the batch sampler is of no value and just creates large log files. And you are running it on all IMU’s.

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I’ve had success with these motors and props with a previous version of the aircraft that was 300g heavier, so I think they should be ok?

OK, then I suppose it should be OK.You have an interesting set of parameters for the fixed notch and the dynamic notch. The former with a freq of 45Hz and the later at 50Hz. Even with the BW of the dynamic notch as low as you have it there will be some overlap. I wonder how you arrived at those settings.

Andy and I went over those settings together in the big notch tuning thread. The static notch is set to cut out the frame resonance. The 45hz base freq for the dynamic is a left-over parameter from when Andy and I were trying to figure out if the frame noise was from the frame or motors.

Here’s a log with more dynamic flight. I apologize in advance for it’s size. I’ll trim some of the logging options soon.

@vosair are you able to try with the throttle-based notch? (or with master - but you may not want to do that). Leonard and I discovered a problem with the ESC telemetry based notch which is fixed in master. Basically the ESC updates are too abrupt and you get synthetic noise driven into the motors. I just wonder whether for your bigger motors they are unable to cope. If this is the issue then we can look at backporting to 4.0.x.

He’s on Master, how about FFT instead?

The problem is fixed in master. FFT does not currently have the fix so possibly worse. But it sounds like that is not the problem.

Has anyone looked at the motor outputs to see if they appear noisy?

Motor outputs look OK to me. Tuning could use some improvement.

Ok looking at the log a few things to suggest:

  • You are on master, I suggest you set INS_HNTCH_OPTS=2 so that you track each motor individually
  • INS_HNTCH_BW at 5 seems too low - 25 maybe would be better
  • Looks like you are on an F4? Don’t set INS_GYRO_RATE to 1 if that’s the case - too much load at 2Khz
  • There are known issues with OF and the harmonic notch - do you experience the same issues if you fly in stabilize?

The static and dynamic center frequency 5Hz apart seems odd. Perhaps another review of pre-filter data is in order to go over these again?

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Ah I was wondering how to track each motor!

I’ll set BW to 25

I’m on an F7, but I think it’s already set to 1 last I checked? Would it be better on 2 considering I’m on an F7?

Same issues in stabilize and althold as I get in guided modes that utilize the OF. I also started this tune with the OF turned off, and I got the same results.