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Permalink Reply by david.collett on June 18, 2012 at 4:22am

Hi Dirk,

It's probably "Servo Pitch PID" that is too high.

However,

I'd suggest you may wish to reset the arudupilot and start again with the default settings following this page to tune the PID's in:

http://code.google.com/p/ardupilot-mega/wiki/Tuning

I found that the "skywalker" settings were *way* too high for my skywalker, you will notice that they are *much* higher that the default values (which by contrast are very conservative (low) for most airframes I think).

You should find that with stock defaults, it will fly ok, but pitch and roll will be a bit sluggish (not crisp) in FBW_A. Then you can increment them until it flys well (as per that tuning page). That's probably a better process than starting with the skywalker settings and adjusting them downwards.

Good luck,

Dave

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Permalink Reply by david.collett on June 18, 2012 at 5:02am

Actually, it looks like there is a newer skywalker.param than the one I last saw (skywalker062311) with more sensible servo PIDS ( ~1 vs ~3).

So you could start there and just turn them down further (try halving to 0.5 and you should see behaviour change in FBW_A). Starting from defaults is still a good idea though :)

BTW, APM Planner has a nice comparison feature, so you could compare defaults with the skywalker params and note which values are different.

Dave

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Permalink Reply by James masterman on June 18, 2012 at 5:25am

As mentioned, the skywalker params on the download page seem to be way too high.

The other thing to note is in version 2.34 of ardupilot, an i term was added to the default pitch pid params. This caused my bixler to oscilate pitch quite badly with throttle also up and down. After removing that, I got much more stable behaviour.

If you have used the downloaded pids, that is probably your problem, so as suggested, reset to default pids ( easy to do through the commandline in mission planner) and then start from there.

Cheers

James

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Permalink Reply by Dirk on June 21, 2012 at 4:52am

Thanks to all of you. I changed a lot of the parameters and will check them in flight ASAP.

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Permalink Reply by Gábor Zoltán on June 25, 2012 at 4:00am

Also possible that the throws you set on your transmitter are too small. ;)

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