Setup harmonic notch, motors running hot

ArduCopter Copter 4.4
1

500mm frame with landing gear, 2806.5 1300kv motors, 8x4x2 props, 4S.

So after my last round of testing, I changed props to these which seemed to help. VIBE quite a lot, from 40-50+ down to 10-15. Motors did seem to be running warm but it was mid-70s and seemed okay: Relevant Log 1

Today I decided to check some various mounting issues (found screws were loose on landing gear and battery plate, also zip tied sliding battery plate to keep rigid, and added battery pad to plate to keep secure). I also setup the harmonic notch and RPM filtering: Relevant Log 2

With that I was getting much higher current draw at hover and motors were especially toasty.

I rechecked my notes and found I set harmonic notch incorrectly (I had 150hz instead of 127hz for some reason). I corrected this and flew again: Relevant Log 3

It definitely felt much smoother but even higher current draw and seems I am getting some nasty gyro noise in X (IMU → GyroX) as compared to others. I am guessing this is due to landing gear but it’s not something I can change anytime soon unfortunately.

I would really just like to get this flyable until I can rebuild, but it seems to be getting worse.

I’ve also found I’m getting more mag align issues now (I’m guessing because of motors compensating). I haven’t run magfit yet but it was not near as big of an issue a few flights ago, now it very visible rotates to align and I get the mag errors constantly.

I feel like I missed a step somewhere.

The very odd thing is, this is the guys from my 7" build. I initially swapped it over to the new frame and didn’t chance anything and it flew quite well. My USB port broke so I had to replace FC (with same, Matek H743-SLIM), and decided to start from scratch, and nothing seems to work near as well.

2

No wonder the motors are hot.:

Rcout
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Get control of the output oscillation 1st by dropping the Rate Pitch/Roll PID’s by half. And set this:
INS_ACCEL_FILTER,10

You will have to take another look at the Notch filter after the output oscillation is under control.

Did you have the SCHED_LOOP_RATE at 400 and the SERVO_DSHOT_RATE at 3 (triple loop) on the other craft? 800 and 2 works for me with that FC and a few different combinations of motors/esc’s.

3

Yeaaah I saw that, quite horrible. I also noticed the IMU0 GyroX was terribly oscillating as well vs Y and Z.

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I have now set INS_ACCEL_FILTER,10 and for PIDS:

ATC_RAT_PIT_P,0.0675
ATC_RAT_PIT_I,0.0675
ATC_RAT_PIT_D,0.0018
ATC_RAT_RLL_P,0.0675
ATC_RAT_RLL_I,0.0675
ATC_RAT_RLL_D,0.0018

I have always left SCHED_LOOP_RATE,400 as default (I see it says “only changed by developers” and “over 400 highly experimental”)?

It looks like previous build on 7" frame had SERVO_DSHOT_RATE,2, but it has been 3 since first starting this one (even back when it was working better). Recommended to change this?

Thanks!

4

Just did another quick test. Motors reasonably cooler but still warmer than I expected. RCOUT, to my untrained eye, look much better and the IMU Gyro X is much calmer.

It was unfortunately windy, but there were very noticeable twitches and drifting, I gather this is due to lower PIDs and therefore slower response.

Here is the new log

5

Rcouts look like a good starting point for tuning. Notch filter looks OK. There is a peak at 35Hz but that’s borderline too low to use the Notch filter on. I would run Auto Tune from where you are.

6

WONDERFUL! Thank you sir, I very much appreciate it! I am really trying to learn but once I think I have a grasp it turns out I don’t.

I do have a question, do you think using lower Kv motors would help with any of this? I was looking to eventually put some bigger and lower Kv motors on to swing 9-10" props, but I also worry with how the frame is built it may make things worse. Though hopefully would be more efficient.

7

What the Take-off weight now?

8

Right about 1.4kg with a GoPro.

9

Yea, you could use something ~900kV with 10" props for more flight time at the same weight.

10

Thanks Dave, that’s what I was figuring. I imagine a lot less stress on the motors as well.