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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Five minutes for me. 2-1/2 For roll then 2-1/2 for pitch.
Dear Developers,
I've had a very strange experience with my quad. It is flyable in Stabilize and Altitude hold as recommended but my AutoTune flight resulted in the craft becoming erratic and eventually going ape after only a few seconds. I tried to disengage AutoTune but at that point the copter was flipping and rolling and it was a battle to get it under control. It crashed, ironically in the grave yard. Managed to get it back together again and then yesterday I flew it again and after engaging loiter it just flipped over and crashed. Could anyone take a look at my logs for the Autotune which I have attached and tell me what they think the problem is? The logs and report from yesterdays flight can be found here: http://diydrones.com/group/arducopterusergroup/forum/topics/fw3-1-3...
Copter Specs:
APM 2.6: FW 3.1.3
Frame Type: Quad (X)
Motors: T-motor 4008-18 380kV
Props: APC SlowFly 14x4.7
ESC: Castle Creations Pheonix Edge Lite 50 Amp
LiPo: 6s 6000mAH 30C
2014-04-24 07-37-06.log
2014-04-24 07-37-06.log.gpx
2014-04-24 07-37-06.kmz
Hi Olivier,
Your copter is very unstable with the pids you are flying with. Autotune didn't cause your problem, it just kicked it off. I can see after autotune does each test that the copter overshoots almost as far as autotune goes in the first place. This means your copter is right on the edge of instability. I would drop your Rate P terms by 50% and try again.
Autotune may not be able to set the parameters low enough for your copter though.
I will look at improving this further in the future.
Hi Leonard,
Yes, I'm beginning to see that my copters have some issues. I have 3 builds which are identical to this and each of them have this massive instability issue. I have not had time over the last few weeks to get back to the tuning but will follow your advice on dropping the Rate P terms even further. Here is a question: If I lower the Rate P terms until the copter is "stable" should I then start working on the Stabilize P (Roll and Pitch) terms until the copter gets twitchy and then drop them down a bit?
Another really weird thing happened on my last test flight of the copter mentioned in the above comment, it was flying great for a while in altitude hold and stabilize and when I finally got the courage to switch to loiter, it seemed to fly perfectly then too until I turned and flew into the wind where all of a sudden it seemed to stop moving forward, pitched backward, pitched forward, pitched backward... well, you get the idea, it was doing a pendulum until it looked like it was going to crash at which point I switched out of Loiter. Since most of my flights are in Auto (I use UAVs for Aerial Mapping and 3D modeling), I'm a little concerned about the relationship between very low PIDs and Loiter/Auto functionality. Is it safe to assume that as long as the copter flies nicely in Altitude Hold and Stablize that it will perform properly in loiter/Auto too?
Thank you!
Hi Oliver,
Could you tell me the size and weight of your copters and post a photo or two.
The basic principle is each pid loop stands on the next so if your Rate tune is bad everything is bad. Also it isn't enough that the copter flies well in Stabilize and Alt_Hold. You need to be able to be rough with the sticks to be 100% sure auto and loiter will work well.
If you copter is very slow to respond in stabilize and alt hold then you may have to back off your auto pids to ensure you don't get an oscillation like the one you described.
The general approach is to find some very stable pid parameters for rate and stab pids, then use Autotune to get the best out of your copter. After that the defaults tend to work well.
Hi, I'm reading all this discusion about the autotune. I find it very interesting.
I hope to do some tries on next weekend, meanwhile I'm thinking in the following idea.
As I don't want to wait 7 or 8 minutes to get the first results, perhaps I would change this parameters by the double
#define AUTO_TUNE_RD_STEP // minimum increment when increasing/decreasing Rate D term #define AUTO_TUNE_RP_STEP // minimum increment when increasing/decreasing Rate P term #define AUTO_TUNE_SP_STEP // minimum increment when increasing/decreasing Stab P term
In that way I will get less accuracy PID values, but in the half of time.
Am I Right?
Thank you very much for reading. Best Regards.
Why would you want to reduce the accuracy of the auto-tune?? You don't want to wait 7 minutes for something that you spent this much time and money on?
Thanks both of you for the answers.
I've read the experience of others and I'm start to think that maybe It would be nice to approach quick to a value near perfect and then if you want, you could make another try changing the range of values of P and D to try closer this first pass value, but with a smaller step, getting even more accuracy.
My opinion is that perhaps that is not necesary because i read someone here who ran four the test and got similars values but with a difference of 0.01 in the KP
On the other hand I think it is a good option for those who don't have enough autonomy.
Hi Facundo, that is correct.
That should speed up your tune by a factor of 2. Let us know how you go.
Hello,
After finaly completing my hexacopter build and after some time familiarising myself with apm and general multi
rotor flying, i wanted to give autotune a try. Unfortunalty didnt go well on the first try. i'l attach video to
show the problem more clearly, but in general autotune seems bit too violent on tuning. As seen in video at one point autotune almost manages to crash the hexa, but quick exit from autotune to loiter saved the day. Since i havent managed to succesfully run autotune i am using default pid settings atm and loiter is actualy pretty stable with them. Only when i try to fly bit more higer and with wind it kinda goes crasy. Starts jumping up and down violently, prolly baro problem. But still wanted to be able to complete autotune. :)
Hope someone has bit time to read this wall of text.
Video of problem: http://youtu.be/TMHbSqzX_Vg
Specs:
Frame: X-CAM CF6-Mini Collapsible Hex-Copter Frame (Full Carbon) (780mm)
Controller: APM 2.6 (3.1.2)
Gps: 3DR uBlox GPS with Compass Kit
Esc: Turnigy Multistar 30 Amp
Motors: Turnigy Multistar 4822-570Kv 22Pole
Props: Carbon Fiber Propellers 12x3.8
Battery(x2): Turnigy nano-tech 5000mah 4S 45~90C
Edit: Just incase uploaded logs to different place also.
http://speedy.sh/u8QXp/Autotune-logs.rar
Autotune logs.rar
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