Hi,
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
Kris
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.
Kris
Hi,
This time I performed autotune with sd card to collect the logs.
https://drive.google.com/file/d/1QzmYwFcAlKbKVp0w6bA4iu0HzDdi9gWl/view?usp=sharing
Could you please take a look.
Thank you in advance.
Kris
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
Kris
https://ardupilot.org/plane/docs/new-roll-and-pitch-tuning.html#roll-pitch-and-yaw-controller-tuning
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.
https://www.rcgroups.com/forums/showpost.php?p=47523671&postcount=6715
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 
Kris
Hi,
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.
Kris
Params
2021.09.09-after_next_autotune.zip (5.7 KB)
And the log:
https://drive.google.com/file/d/1agsKnE8uBibfKci8aGc7HeD6Y_tKBFuf/view?usp=sharing
