Please explain Notch Filters web page

ArduCopter
1

I am trying to setup the notch filter as described on this page, but I am stuck a little bit
https://ardupilot.org/copter/docs/common-imu-notch-filtering.html

Lower on the page it says “graph the throttle value”
I found something somewhere saying it is CTUN.ThO.

My throttle value is just under 0.2 if I look at this graph
CTUN.ThO graph

If I look at the parameter MOT_THST_HOVER it is 0.1586141

So my hover_thrust = 0.1586141 it seems

Do I get the frequency from the graph when you press the FFT button?

Frequency?

So if I read the graph right I have spikes at 70 Hz and at 120 Hz so those are my frequencies?

This is my current parameters
These are my parameters

Just a hover log

2

I think you are correct → use the MOT_THST_HOVER, and from the graph it looks like you would use 70Hz (the next big spike up is about 140Hz)
You current params file doesnt have HNOTCH enabled.

You can go to “Phase 2” in my cheat sheet and use these values
INS_HNTCH_REF,0.15
INS_HNTCH_FREQ,70
INS_HNTCH_BW,35

This is my own cheat sheet for setting up the Harmonic Notch filter

=========== Using throttle ============
HNOTCH phase 1
INS_LOG_BAT_MASK,1
INS_LOG_BAT_OPT,0

  • hover test >1 minute, check FFT

HNOTCH phase 2
INS_HNTCH_ENABLE,1 ← set this then refresh params to see the rest
INS_HNTCH_MODE,1
INS_HNTCH_REF, hover_thrust
INS_HNTCH_FREQ, peak freq from FFT
INS_HNTCH_BW, peak_freq / 2
INS_HNTCH_ATT,40
INS_LOG_BAT_MASK,1
INS_LOG_BAT_OPT,2

  • hover & dynamic test >1 minute, check FFT results

HNOTCH phase 3
INS_LOG_BAT_MASK,0
INS_LOG_BAT_OPT,0

  • no extra logging, assumes HNOTCH is working great

BUT forget all that stuff above…

You appear to have DSHOT configured and working on Aux outputs. You just need the ESC telemetry wire connected to a serial (TELEM) port RX pin and set something like this:
SERIAL2_OPTIONS,16
SERIAL2_PROTOCOL,16
then set these and go run Autotune

============= Using ESC Telemtry ============
HNOTCH BLHeli32 telem
INS_HNTCH_ENABLE,1
INS_HNTCH_MODE,3
INS_HNTCH_REF,1
INS_HNTCH_FREQ,70
INS_HNTCH_BW,35
INS_HNTCH_ATT,40

You can set these and view the FFT graph to check if it’s working OK
INS_LOG_BAT_MASK,1
INS_LOG_BAT_OPT,2
and when satisfied, set these:
INS_LOG_BAT_MASK,0
INS_LOG_BAT_OPT,0

3

Thank you. I will try this tomorrow morning. I rebuilt after the last crash. I am using aluminum (U shape) now for the arms and no rubber between motor mounts and arms. I have not looked at the logs yet, but the bar graphs while flying show very little vibration

The one motor that hit the pole had some wires that broke off.
I didn’t have any more 260KV motors spare so I had to replace the one 260KV with a 530KV from my first batch of motors. So I have 3 x 260KV now and a 1 x 530KV just to keep on going while I wait for my upgrade to 360KV. It was very stable today. Well to me it was :slight_smile: I am scared to look at the logs lol