This is a discussion re the ArduCopter-3.1 AutoTune feature. A place for people to report successes and failures, ask questions and get answers.
The AutoTune wiki page is here.
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Deal.
Thanks mate.. Can you possibly give us a longer, more thorough explanation? :P
(just kidding please do not elaborate further)
Leonard can say for sure, but I think it was selected as a conservative estimate of a typical flying excercise that gets both the smooth camera ships tuned well and the acro junkies.
I'm curious to you as well: What rate - if different - would you have gone with?
I would need to read up on the tuning method first to fully understand the impact of that rate, but my initial thought was that some very large copters may be physically unable to acheive it. Based on the videos that I have seen of people doing autotune, it looks like it works well for most people.
I'm also curious why Ki is set to Kp at the end.
Is there a white paper on all of this floating around somewhere?
Hi bblatter,
I don't think 90 degrees per second is a problem for even the largest copters. Even the slowest copters I have seen are able to reach 90 degrees per second quite quickly. I have artificially slowed a copter down to a maximum of 90 degrees per second and it was almost unflyable.
Ki is set to equal Kp because that gives a comfortably quick response to external forces. The main one force is when we enter fast forward flight. However, I have heard someone say that dropping Ki to half or a quater Kp helps if you have decent wobbles. I have also seen people set Ki to 4xKp. So it is up to the user.
Sorry, no white paper. I will eventually put something together but writing papers isn't my favorite thing :)
Hi,
I have very bad oscillations on my F450 and i'm beginner with all those PIDs. I use AC 3.1.2 and wondering if i can use this Autotune thing but i read that for auto tune copter have to be able to fly in Alt flight mode but i'm affraid to test ALT mode because of this oscillations. As far i read my log vibrations seems ok. If someone can take a look on my post here:
http://diydrones.com/group/arducopterusergroup/forum/topics/beginne...
I do not know if i have such big osscilation i can performe autotune (so will not fall or flip from the sky). Right now is like flying a "boat on water" feel...
Ps. I attach a log file and link to video: https://www.youtube.com/watch?v=s56UBBxiqgI
Best Regards!
Thomas
2014-03-07 16-16-59.log
2014-03-07 16-26-22.log
Hi Thomas,
From what I can tell, every time you put in a control input the copter overshoots a little and wobbles back and forth.
I would suggest that you drop your Rate P and Rate I terms by 25% and try again. You are looking for something that doesn't feel very responsive but doesn't wobble around in the air if there is not wind.
Then just check that Alt Hold works. If it moves up and down then do the same thing for the Accel P and I terms.
Once you can comfortably hover in Alt Hold. do an Autotune.
Autotune sometimes has trouble with more flexible frames so if Autotune fails then you may have to resort to manual tuning.
Let us know how you go and good luck!!!
Hi leonardthall,
Sorry for delay. I will check what You suggest this week. What about Roll rate and Pitch Rate? I don't have knob onj my Radio dx6i so autotune also will adjust this settings?
PS. If something goes wrong how to exit from autotune to recover the copter?
Best Regards!
Thomas.
Hi Thomas,
Any time you touch the sticks autotune stops and waits for you to let go of the sticks again.
So if you see go somewhere it shouldn't just fly it back, autotune stops, then when you have it back where you want it let go of the sticks and autotune will start again.
Autotune only makes very brief adjustments to pids while doing it's test then returns them to the default. So it is very hard for autotune to crash a quad unless it has a very bad tune to begin with.
Ok, I found your post.
I suspect Autotune isn't coming up with gains that are too high for your copter, I think the problem is you are flying the copter in a different configuration to the one you used to autotune.
If you are flying with a large gimbal that is free to move on the frame you will probably find that auto tune doesn't work. If you do autotune with a load firmly attached to your copter then replace it with a gimbal your parameters will probably be too high and verging on unstable.
The best approach to using autotune in this situation is to remove the gimbal and do autotune with the lightest setup you can (that doesn't cause the battery voltage to sag). This should give more conservative pids that will be safer with your gimbal.
However, the final performance depends on the resonate frequency of the gimbal and suspension system. Autotune is not designed to tune a copter with this extra degree of freedom. In the end you must ensure the copter is stable yourself and make manual adjustments if needed.
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