APM 2, Flying Wing - Nav. Problem

I set FX-79 with APM2.0 (APM Mixing) and it worked fine with FW2.78b, both FBW A and Auto modes.
I uploaded FW3.0.1 and try it today. FBW was good. When switched to Auto or RTL it has a problem to keep the direction straight. It oscillates a lot. Decreasing the L1 from 20 to 17 did not solve it. Increasing to 23 results in more oscillations.
Any Idea why?
Did I miss something in the shifting procedure from 2.78b to 3.0.1?
Any help will be appreciated?

p.s. tlog is attached

After several After several attempt to work with FW 3.01 and 3.02 on APM 2, I replaced it with APM 2.6
Here are the results FW3.0.2. Minor Nav . oscillations but it is work
Any suggestions how to get read form those.

You may want to try the autotune function and see how that works. Also, just in case, I wouldn’t enable the EKF until you get things sorted out.
When I get unexpected results I kind of start from scratch again. Cal the compass, the accels, radio and set PID to fairly benign settings.

Thanks Icarus. That what I did without success, so I replaced the APM2 with the 2.6
Starts from scratch and got it working with minor nav oscillations.
To the best of my understanding the EKF works only on Pixhawk, Am I wrong?

[quote=“avi_levy”]Thanks Icarus. That what I did without success, so I replaced the APM2 with the 2.6
Starts from scratch and got it working with minor nav oscillations.
To the best of my understanding the EKF works only on Pixhawk, Am I wrong?
You’re right, EKF only works on PH. My apologies. I’m too used to responding to PH stuff. Did you try the auto tune? Oscillation is usually caused by too high P. Are you 100% sure elevons are set up correctly? Are you seeing pitch and roll oscillations

Yes I am using Elevon output. Works great on manual

Very stable in PBWA so I gauss PID are good. The oscillations are while navigation’ in auto mode or RTL
It does not flies on a straight line (see figures). It is much better with APM2.6 FW302 and APM2 with FW2.78b

I looked at tlog. I suggest you try the autotune. Your P does not appear high enough for roll. Also try making your WP radius larger. It will help with the overshoot and catch up corrections.

Hi, if I remember it correctly, the manual suggest to increase L1 value per 1 or 2 if the plane start sneaking.

This is more for oscillations. His plane is doing slow snaking movement.

Hi again
Many thanks for all the comments
These are the modification made today (previous values in brackets) with FW 3.0.3
MIXING_GAIN 0.65 (0.75)
WP_RADIUS 45 (30)
NAVL1_DAMPING 0.82 (0.75)
RLL2SRV_P 0.9 (0.8)
PTCH2SRV_RLL 1.2 (1.0)
It looks much better, yet it is still doing slow snaking movement but much less. Maybe this is due to the wind speed and direction oscillations. To see the actual flight behavior, an FPV video is posted in YouTube


The first part of the video is the auto mode as in the attached photo and then FBWA flight. As you may see it is much stable
All comments will be appreciated

Additional tuning for airspeed sensor reinforced GPS to the wing. Strong wind with small gust conditions, minor change in wind direction, it flew well

Can I comment on this if it is marked as solved?
I have the same problem with my X8. It flew just great with all firmware versions up until FW 3.0.0. Now we have a heavily snaking plane that flies nowhere near the lines between way points.
I have done an AUTOTUNE on level 6, however the PID’s seam very low. increasing the roll P did not do much for the snaking. L1 Damping up to 0.85 had the biggest effect.
Please help. I will post logs as soon as I get them of the plane.

Please post your tloh file. I will have a look

Here you go:
Thanks for the look.

First I will recommend using elevon output and not elevon mixing
It let you better control in FBW

which apm you are using?
Do you have external compass?
Have you calibrated you air speed sensor?

Hi Avi-levi,

I think that might be my problem. I am using an APM 1.4 still. The airspeed-meter is calibrated and I am not using a compass at all.
I think that the APM 1 is not coping with the newer firmware. I must admit that the day was terrible, with strong and very gusty wind blowing. The X8 that we flew just before this flight also had problems staying on line, but did this allot better than the one running the new firmware. Btw, the two planes are identical except for the firmware.

The problem was solve not only by calibration, but also replacing the APM 2.0 with APM 2.6
With the APM 1.4 and APM 2.0 the latest FW I am working with is 2.78b which works very stale.
Note that APM 1.4 do not support the ELEVON OUTPUT which makes the flying wing flies much better with the APM