Help with new filters (3.7)

ArduCopter Copter 3.6
1

I’ve been running 3.7 all year… Recently was running @andyp1per custom firmware when he first introduced some new notch filters for D term, etc…
I decided to update today, and there are a lot of new filter parameters.
Can anyone help me with them?

INS_HNTCH

ATC_RAT_FILTE
ATC_RAT_FILTT

I’m leaving for vacation in the morning, and am hoping to get this sorted before then!!!

Thanks for any help.

2

I see hnotch is harmonic notch…
I guess I’ll leave that one be until I have more time to learn about it… Unless you have a recommendation for a small copter… (My FFT shows a peak at 240hz)

The others I still haven’t found any information about…

3

HNTCH is the harmonic notch. Details can be found here https://github.com/ArduPilot/ardupilot/pull/11795
I’ll add wiki info when the dynamic notch is in. You can see the docs in the code here: https://github.com/ArduPilot/ardupilot/blob/master/libraries/Filter/HarmonicNotchFilter.cpp

FILTE and FILTT (there is FILTD as well) are the error and target (and derivative) frequencies which can be found here https://github.com/ArduPilot/ardupilot/blob/master/libraries/AC_PID/AC_PID.cpp I don’t really understand what they do - @Leonardthall would know - but I believe you can leave FILTE and FILT at their defaults of 0 which is off and then FILTD is what FILT used to be. I’m guessing they allow you to set different filters for these components rather than just only the D term.

4

Thanks a lot!

I guess I’ll leave it as is w/ the traditional filters. FiltD, Gyro, and Notch.
I just had a test flight while you were replying, and it’s flying great! I expected some issues when I first saw the new parameters, but nope… It’s good.

Thanks again for replying, you’ve been a big help. Can’t wait to see the dynamic notch :).

5

What you really want is the dynamic notch driven by a dynamic FFT (https://github.com/ArduPilot/ardupilot/pull/11886), because that works really well - but only I am flying with that for now :wink:

6

That’s awesome… While flying your July version of firmware, I occasionally got oscillations at specific loads… Just sometimes… Changing my throttle level made them go away, and I’d imagine the dynamic notch would take care of that.

How are you finding the base frequency for the harmonic filter? In the thread about it, everyone is setting it quite low… 50-80hz Looking at my FFT’s from July, I don’t really see any noise until around 200hz… But I’m guessing there is some and the 200hz noise is just MUCH greater so the lower frequencies don’t show up.
I guess I need to read up on the FFT again… It’s been months since I used it. Perhaps I can give it a frequency range to look at. I’ll mess w/ that next month after vacation.
Going to be backpacking and flying my copters in the mountains for the next couple weeks :smiley: