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F-86F Sabre Rocks Side to Side between waypoints on autopilo

Designing a stable autopilot is one of the hardest things. Need help?

Re: F-86F Sabre Rocks Side to Side between waypoints on auto

Postby Octal450 » Sun Jan 01, 2017 12:45 am

That's ALOT. Aren't fighters sensitive? Try something like 0.05kp. make sure you change the PID which outputs to /controls/flight/aileron (My MD-88 which is a sluggish responding aircraft uses 0.06kp...) for the roll PID (target-roll and current roll = aileron)
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Re: F-86F Sabre Rocks Side to Side between waypoints on auto

Postby Turnit » Sun Jan 01, 2017 5:13 am

Okay, ill try that next time I take the F-86 up, which should be with in a few days.
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Re: F-86F Sabre Rocks Side to Side between waypoints on auto

Postby Octal450 » Sun Jan 01, 2017 5:38 am

OK. Good luck.
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Re: F-86F Sabre Rocks Side to Side between waypoints on auto

Postby Thorsten » Sun Jan 01, 2017 7:00 am

I didn't mean you should solve this type of problem with a rate-of-change.


Ah, okay, I misunderstood - it's the equivalent of e.g. a JSBSim <kinematic> tag to make the airfoil moving a time finite.

I actually define these before starting to tune an AP at the stage where I do manual control - I've learned that the hard way when very sharp gimbal movements in the thrust vector controls killed me every time due to over-acceleration in a frame.

I guess if you don't have that large control effects then you can afford to do it afterwards, but my understanding is that it'd be good to put the finite time airfoil movement in before tuning anything.
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Re: F-86F Sabre Rocks Side to Side between waypoints on auto

Postby Octal450 » Sun Jan 01, 2017 4:55 pm

Makes sense. @Thorsten
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Re: F-86F Sabre Rocks Side to Side between waypoints on auto

Postby Turnit » Mon Jan 02, 2017 11:58 pm

It still rocks with the kp at 0.05, should I decrease it more?
Last edited by Turnit on Tue Jan 03, 2017 4:11 am, edited 1 time in total.
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Re: F-86F Sabre Rocks Side to Side between waypoints on auto

Postby Octal450 » Tue Jan 03, 2017 1:42 am

0.05
0.1 is alot for an airliner, so half that.
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Re: F-86F Sabre Rocks Side to Side between waypoints on auto

Postby wkitty42 » Tue Jan 03, 2017 2:13 am

i thought the F86 Sabre was a fighter jet??
"You get more air close to the ground," said Angalo. "I read that in a book. You get lots of air low down, and not much when you go up."
"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
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Re: F-86F Sabre Rocks Side to Side between waypoints on auto

Postby Turnit » Tue Jan 03, 2017 4:10 am

My mistake, i meant 0.05.
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Re: F-86F Sabre Rocks Side to Side between waypoints on auto

Postby Octal450 » Tue Jan 03, 2017 11:44 am

Yes. My point was if a heavy airliner used 0.08, you should have much less. Keep reducing.
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Re: F-86F Sabre Rocks Side to Side between waypoints on auto

Postby wkitty42 » Tue Jan 03, 2017 6:56 pm

ohhhh... ok... that's makes more sense now that i read it again with that in mind ;)
"You get more air close to the ground," said Angalo. "I read that in a book. You get lots of air low down, and not much when you go up."
"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
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Re: F-86F Sabre Rocks Side to Side between waypoints on auto

Postby Octal450 » Tue Jan 03, 2017 8:04 pm

:D
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Re: F-86F Sabre Rocks Side to Side between waypoints on auto

Postby Turnit » Sun Feb 19, 2017 7:15 pm

Sorry for not posting anything here, I didn't fly this bird for a good chuck of January and early this month and haven't got the autopilot fixed yet. I am working on it again though.
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Re: F-86F Sabre Rocks Side to Side between waypoints on auto

Postby Octal450 » Sun Feb 19, 2017 9:39 pm

Is the problem as bad as before?
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Re: F-86F Sabre Rocks Side to Side between waypoints on auto

Postby Turnit » Mon Feb 20, 2017 3:20 pm

Its still rocking, at times it isn't as strong as it was before, but can be as bad with a heavy load it seems.
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