Hi guys,

I have problem with navigation of my Skywalker x8 in AUTO mode. As you see on the picture below, the plane cant fly straight between waypoints and also makes unnecessary turnings. I am using mission planner ver. 1.3.44.

First I tought the problem is with navigation tuning and tried to change some parameters, Here are the parameters from which I started:

NAVL1_PERIOD 22

NAVL1_DAMPING 0.8

RLL2SRV_P 1

RLL2SRV_D 0.02

RLL2SRV_I 0.04

PTCH2SRV_P 0.65

PTCH2SRV_D 0.02

PTCH2SRV_I 0.04

After that I tried to make some changes in the values but it didnt help. Do you have any idea which parameter can cause this issue? Some other parameter what I didnt change? Or could it be something else like compass error? The plane is flying well in manual and FBWA modes. I will appreciate any help!!

I also uploaded the logs to google drive, here is the link for download: https://drive.google.com/file/d/0Bwtgo0Y55BmmQmQ0TldiNFZsVzA/view

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My guess is that your NAVL1_PERIOD is too high. Try lowering it incrementally. I think you'll end up somewhere between 15 and 18.

Hi,

can you please check this log, too? Have almost same behaviour on one of my flying wings. Weird enough it was flying well before. The only difference is that I have switched off STALL PREVENTION. Just in case, I have replaced the GPS/COMPASS unit and will be testing tomorrow.

NAVL1_PERIOD is default 20

Thanks, 

Anton

https://www.dropbox.com/s/8n9yoae4eabcvlq/34.BIN?dl=0

Hello Anton,


glad to hear that somebody try to solve the same problem. I still believe that it is caused by some wrong navigation parameters. We will be testing new methods tomorrow. If we don't fix it, we will probably try to connect new PixHawk flight controller. Please let me know about your todays testing of a new GPS/comapss unit that we can both figure it out asap. Good luck!

Best Regards,
Mira



iskess said:

My guess is that your NAVL1_PERIOD is too high. Try lowering it incrementally. I think you'll end up somewhere between 15 and 18.
Thank you for your advice, we will try it tomorrow and I will let you know abot our results. Do you also use Skywalker X8 + PixHawk? If so, could you please send me one of your logs? Thank you.

Hi Mira, 

tested another GPS/COMPASS unit, same result. Went lower on NAVL1_PERIOD from 20 to 19 and the effect only got worse. Couldn't continue tests due to strong winds, tomorrow will be testing going higher on NAVL1_PERIOD. My navigation issues started after I have turned off STALL PREVENTION.

Looking forward to your results, too.

Kind regards,

Anton

Here is a direct comparison of same almost square mission with different NAVL1_PERIOD values.

Hello Anton,

thank you for your reply! Do you also have a screen with waypoints? Btw. did you try to turn STALL PREVENTION back ON? You also mentioned that only one of your planes does that. Other planes works fine for you with same navigation parameters? Thank you and good luck for tomorrow.

Mira

This may be a mechanical issue? does the aircraft fly OK in stabilize?  or is it hesitant to turn ?

I have seen a similar example of this with a flying wing where the down going Elevon in a turn was causing the aircraft to Yaw in the wrong direction 

ie. if you want to make a turn to the right your Left Elevon will drop and cause the aircraft to Yaw to the Left instead of making a good banked turn to the right. 

If this is the problem then AUTO will never work right. 

its easy to fix, reduce the maximum downward deflection or the Elevon to 50% of the Up going deflection. now all my aircraft are set up like this .  

Mechanically the plane is just fine. I am not using STALL PREVENTION because it wasn't allowing for good AUTO takeoffs from the catapult. Analyzing today's logs seems like the answer to my issues are indeed STALL PREVENTION algorythms. I have ROLL limited to 35°, while NAVL1 set to 20, these angles were exceeded during navigation up to 45°. While NAVL1 set to 19 these raise to 60° during all those pirouettes seen in the log flight path. So STALL PREVENTION was smoothing out this behaviour, once it is switched off NAVL1_PERIOD has to be tuned precisely.

Just to mention, before turning off STALL PREVENTION the plane was navigating very well.

As for other planes, those have STALL PREVENTION ON and use runway takeoff, navigating fine using stock NAVL1_period - 20.

Hello DwgSparky,

First, thank you for your reply. Your post sounds reasonable because I did some elevon changes in the past. I will definitely try it tomorrow and let you know about our results. Could you please send me some of your logs using fixed wing? Thank you in advance.

Mira

Here is a screenshot with WPs and the worst flight with NAVL1_PERIOD 19



Mira said:

Hello Anton,

thank you for your reply! Do you also have a screen with waypoints? 

I cannot get at any logs until much later today.., 

The easy way to see this issue is in manual control, The X8 flys well under RC control and if Adverse yaw is the problem then when the aircraft is in level flight and you command a medium RIGHT turn the aircraft will Yaw LEFT and then you will see the planes nose drop and it will turn RIGHT.

 

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