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Permalink Reply by Jonathan Challinger on August 3, 2011 at 1:04pm

This sounds odd, I haven't had the same experience.

Are you hitting "write WPs" when you're done with WPs? Are you hitting "read WPs" after to check that they got written correctly? Are you hitting enter to save your modes before you reset? How are you testing that your modes work? Remember that you must connect in the mission planner after you switch to flight mode.

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Permalink Reply by Jesper Rooth on August 4, 2011 at 11:55am

Thank you for answering Jonathan.

I did do everything you suggested before first flight, but I think a possible cause was found during the later troubleshooting process.

While programming the flight plan I also added the parameters from the Skywalker PID file found here in the download section. It seems some parameters (possibly radio related) was overwritten. So the modes where correct but it did not compensate while tilting the airframe. It is strange because I could not see anything in the Skywalker parameter file that would overwrite my radio end point settings.

I just came back from the field with two scary moments.

 

1) when switching to auto mode from FBW_A the Skywalker throttled up (a lot) and turned the nose down (even more). When switching back to manual just before the crash would happen it took some while before I got control. The Skywalker wings sure flapped like a crazy goose - overspeed.

This happens everytime I switch to auto. It seems to correct itself if I "help" APM by nutching the ailerons and elevator. I did wait for GPS lock (+2 minutes) so home position should been correct.

 

2) When finally flying towards waypoint 1 it steared in a oscillating way. Kind of overcompensating but still ontrack. See picture.

As you can see I gave up since I lost visual contact with the Skywalker. Advice for all other APM rookies is not to place waypoint 1 (or any waypoint for that matter) directly in the sun. :)

 

Does anyone know what could cause these oscillations on the flight plan? Worth mentioning that there was hardly no wind during the flight. I also had the exact same problem when flying in X-Plane.

 

Regards,

Jesper

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Permalink Reply by Jesper Rooth on August 18, 2011 at 1:46pm

About the overcompensation between the waypoints - has anyone seen this before? PID tuning required?

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DeveloperPermalink Reply by Doug Weibel on August 18, 2011 at 8:12pm

Yes, that appears to be a tuning issue. With proper tuning you will get flight right down the course line.

Work on tuning in X-plane first to figure out how everything works. Look at the tuning suggestions in the wiki. With a little effort you can get the tuning in X-plane good enough that it tracks the course line so well that the track directly overlays the course line (except while turning at a turnpoint). I have never gotten a real plane tuned quite that well, but you can get them to fly within a meter or two of the course line.

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Permalink Reply by Jesper Rooth on August 21, 2011 at 12:26pm

OK - logging my findings to share for future APMers.

Increasing PID for Roll and Pitch on the Skywalker helped a lot. Doubled the default values and it now follows the path much cleaner.

Think the values in the Skywalker.param file are a bit too high for my taste.

Also noticed when looking at the flight through Fatsharks that the nose turns left when it rolls to the right. Normally all full scale gliders do this due to the secondary effects (do not know the english term) on the control areas. Added Yaw PIDs and got rid of the unwanted nose drops.

Really cool platform!

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Permalink Reply by Jesper Rooth on August 21, 2011 at 12:33pm

Responding on my own replies.. sorry

 

But I have to share a story that happened today. While running FPV at 500 meters the video cable from my camera broke. No picture. Panic!

But then I just switched to RTL mode and after three long minutes the Skywalker appeared 75 meters over my head :)

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