Tuning the Harmonic Notch

Line:

Secondly FFTs have a Schrodinger-like relationship between frequency and time - you can choose high time resolution or high frequency resolution, but you cannot have both at the same time.

Heisenberg-like, not Schroedinger-like.

Caption:
Pick top or bottom, but be consistent. You use bottom caption for the other images, so I think the highlighted section should be moved below the second image.

Thanks. Schrodinger is gone. I think the captions are consistent in that they smply flow with the text. Generally they refer to something below.

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I just did the 4.03 upgrade and no notch filter settings appear.
Me thinks I need to reflash it to something else and then come back…sigh

The only one you will see initially is INS_HNTCH_ENABLE. If that’s not there then you have not done the upgrade correctly.

I wondered if it was something like that.
I will go back and check…Thanks @andyp1per

@andyp1per it seems to me that what I read in FFT docs in the paragraph “Harmonic Notch Throttle Configuration” summarized here:
Stable hover for learning the values, then
INS_HNTCH_FREQ ← FFT_FREQ_HOVER
INS_HNTCH_REF ← FFT_THR_REF

are not in accordance with what you posted earlier:

Thanks - I have fixed this now.

@andyp1per I built a new Tarot 810 Hex and flew it for the first time yesterday.

Running a CUAV nano v5 flight controller on a Carbon Anti Vibration plate.

Using BLHeli_32 ESC rpm telemetry

Seems like most of my large spikes in vibration are around the 55-60Hz range

IMUs:

  • InvenSense ICM20689 accelerometer / gyroscope
  • InvenSense ICM20602 : accelerometer / gyroscope
  • Bosch BMI055 accelerometer / gyroscope

Settings are:

|INS_HNTCH_ENABLE|1|
|INS_HNTCH_FREQ|50|
|INS_HNTCH_BW|30|
|INS_HNTCH_ATT|40|
|INS_HNTCH_HMNCS|3|
|INS_HNTCH_REF|1|
|INS_HNTCH_MODE|3|

And raw data looks like:

And post processing:

CTUN.n:

I think it looks pretty good, but curious what your thoughts are.

Thanks

Yeah, looks nice. This is another aircraft that would benefit from the double notch

For the 100hz area? When is that going to be mainstream?

These are just my play rigs, I can test new software without issue

It needs testing but works well in SITL. So feel free to try, but caveat emptor I have not flown anything larger than a 4" in my office with this yet. I would be very surprised if there were issues however. It’s more about getting data for the optimum notch separation.

The larger copters always have a wider peak that the double notch would help with.

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Hi @andyp1per and other notch filter experts,
This is our first time trying the notch filter and following the instructions for it.
We would appreciate an experienced person checking these log files and see if we did everything correctly.
I’m aware we should probably set INS_HNTCH_ATT to 40, and will do so ASAP.
Also I wish to know if there is any parameters we should disable or change once the notch filter is confirmed set up correctly - for example do we set INS_FAST_SAMPLE,0

Copter is 450mm diagonal, 9 inch props, 1157KV motors, 3 cell LiPo

Link to 3 log files:

Relevant params from the 3 log files:

LOG1 - quick hover test
INS_FAST_SAMPLE,1
INS_NOTCH_ENABLE,0
INS_HNTCH_ENABLE,1
INS_HNTCH_FREQ,80
INS_HNTCH_BW,20
INS_HNTCH_ATT,15
INS_HNTCH_HMNCS,3
INS_HNTCH_REF,0
INS_HNTCH_MODE,1

LOG2 - quick dynamic test
INS_FAST_SAMPLE,1
INS_NOTCH_ENABLE,0
INS_HNTCH_ENABLE,1
INS_HNTCH_FREQ,105
INS_HNTCH_BW,20
INS_HNTCH_ATT,15
INS_HNTCH_HMNCS,3
INS_HNTCH_REF,0.3134342432022095
INS_HNTCH_MODE,1

LOG3 - full flight test
INS_FAST_SAMPLE,1
INS_NOTCH_ENABLE,0
INS_HNTCH_ENABLE,1
INS_HNTCH_FREQ,105
INS_HNTCH_BW,30
INS_HNTCH_ATT,15
INS_HNTCH_HMNCS,3
INS_HNTCH_REF,0.28110483288764954
INS_HNTCH_MODE,1

All advice appreciated.

The second log is the best. Why did you change REF to 0.28 in Log3? Your hover graph shows that 0.313 is much closer to the appropriate setting for a hover freq of 105Hz.
As you say increasing BW and ATT will help, I think the bumps in the full flight test are because you have the wrong ref (unless you want to scale from a lower frequency, but in that case you need to set FREQ as well).
But looks pretty good. I reckon it’s more like 103Hz FWIW

Thanks, we’ve set:
INS_HNTCH_FREQ,103
INS_HNTCH_BW,40
INS_HNTCH_ATT,40
INS_HNTCH_REF,0.3134342
…and will update how it goes.
The quad was flying very well before this, and it’s been hard to tell any difference since enabling the Notch Filter.

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Should we change INS_LOG_BAT_OPT,2 or any other params once we’re happy with the harmonic notch filtering - but obviosuly we want to keep the feature working ?
Just want to minimize unnecessary logging and CPU load.

Depends on your FC and SD card, I use fast SD cards and always have this setting on. The load is not appreciable and actually if there are problems you just won’t get log messages.

I have been working on Tuning my Tarot 810 Frame. I am pretty happy with these results.

CUAV Nano v5 (non internally vibration dampened)

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@andyp1per

Thoughts on this? I just cant seem to knock down the spike at 60hz 3600rpm

My hover is at ~4000rpm

NS_HNTCH_FREQ 50
INS_HNTCH_BW 30
INS_HNTCH_ATT 40
INS_HNTCH_HMNCS 3
INS_HNTCH_REF 1
INS_HNTCH_MODE 3

Are you sure you have your pole count correct?

Yes for sure…
SERVO_BLH_POLES 22

And here are the motors:
Arris 4010pro
KV:380
Configuration:24N22P