High PTCH_RATE_I afgter autotune AR Wing Pro/pitch oscillation - Beta 4

I’m trying to setup my new AR wing pro, and it’s ok except pitch oscillation which are annoying…
Unfortunately i don’t have log files, but i can see that after autotune PTCH_RATE_I = 0.98 which seems to be higher then advices max value = 0.6.
And it looks like following

This is comparison to initial value…

I wonder if it could be connected to 2mm initial reflex on elevons?
Any idea what should be changed?
Thank you in advance

I cleaned up my pitch oscillations in Beta 3 by increasing the auto tune level by one from the default.

I always use AUTOTUNE_LEVEL,7. Next time i will try with SD card to get the logs.

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This time I performed autotune with sd card to collect the logs.
Could you please take a look.
Thank you in advance.

I can see oscillations early in the flight they seemed to get better with the tuning. There’s only a little bit of flying in FBWA after the tuning so it’s hard to say how successful the tuning was but from what I see it certainly looks flyable, and reasonably tuned.

I’d say fly it around in FBWA for a while and see what you think. If AUTOTUNE_LEVEL, 7 isn’t enough consider bumping that up. If the performance is good but you still find oscillations, consider turning down PTCH_RATE_SMAX (or roll) https://ardupilot.org/plane/docs/parameters.html#ptch-rate-smax-pitch-slew-rate-limit. I dropped mine to 140 and it seemed to help but that adjustment was a total guess. Since everything worked after that I didn’t need to play more with that value so I haven’t really figured out how sensitive the adjustment is. Proceed with caution.

Post a log after a few minutes of FBWA. Straight & level, as well as some turns.

Thank you,
I will try


There’s new tuning instructions for 4.1 and a good explanation of SMAX. Have a look and see if that helps.

Check also these notes from Tridge in regards to small planes < 1.5kg in Beta 4 that are not in the Wiki.

For really small planes there are a few things worth looking at:

  • raise INS_GYRO_FILTER, 30 should be fine, but 40 would be reasonable too, depends on noise
  • if you have digital servos then consider either raising SERVO_RATE above 50Hz, or set ONESHOT_MASK to a mask of the control surface channels with digital servos. Using ONESHOT_MASK means the output to control surfaces is synchronised to the PID calculations, so a bit less lag
  • raise SCHED_LOOP_RATE above the default of 50. I use 200 for my NanoTalon. Note that this does result in much bigger logs though, so you may prefer 100 or so
  • look at using the static or dynamic notch filters to reduce noise to the gyros: https://ardupilot.org/plane/docs/com…filtering.html

we’ve flown planes under 100g successfully. The main issue with planes that small is trying to get the slop in the linkages small enough to be flyable.

Thank you
I will check after short vacation :slight_smile:

I made upgrade to beta6, now after autotune P is lower, but still pitch is oscilating. From a video footage (counting frames) it looks like almost exactly 4Hz oscillation.
I took a look at log files, but not experienced in this area, end it looks fine, except small oscillations in FBWA and no such a oscillation in manual mode…
In manual mode it flights very well, no oscillations…
PTCH_RATE_SMAX seems to be ok because srate is below 100 most of the time…
One more thing, could i be connected to bad health of the compass? It’s reported in the log.

2021.09.09-after_next_autotune.zip (5.7 KB)

And the log: