The arducopter tuning guide.
This guide was written at the time of the release of Arducopter 2.8.1 FW. It is a compilation of everything I have gathered from the experts in the field of flight controller tuning. It will help give you an understanding of how to tune any rotor based flight controller, but its specific to Arducopter and this firmware release.
I will update this as necessary, or if you can convince me any of it is incorrect just post below and I’ll update this text.
There is a summary/quick reference at the bottom, so once you’ve read this rather rambling explanation you won’t have to again, other than to check details :D
Tuning your flight controller is essential for a perfect flight. Even a fully stock frame will fly better if you tune. The default params will be close, but your battery or motors might be performing differently, your air maybe ‘thinner’ compared to the developer that last published the default params, so you should tune.
What we are trying to achieve is control. We start to accomplish this by modifying the amount of P, I and D in our control loops. All three react to our stick inputs and the errors created by measurements from our sensors, and all three will help us fly better. If we do not have enough of any of the params the copter will not feel like it’s under control, it will wander about, not resist wind and be hard to fly. Too much of any of the params and the copter will seem to have a mind of its own. It will over-react. At best you will see it oscillate, very fast, not so fast or somewhere in between, depending on which parameter has been overclocked. At worst it will simple flip over on take-off or be very unpredictable in flight.
We need to find a balance. You can tune each param up individually, but one will have an effect on another. Therefore we must tune one, then another, then go back and see if we can retune the first one again, this is the balance.
And this is where we adjust those parameters – Mission planner config page:
Before you start:
So let’s start tuning
Everything you read below will be demonstrated in the tuning video further down, so you know what to look for, and at the bottom is a summary for quick reference. I think, however, it’s important to include as much information here as possible as anyone starting into this hobby will often find this process to be a bit of a black art.
I’ve found the quickest way to tune the arducopter is to start with rate_D, (but you simply can’t do this unless you can hold your beast in hand or in a jig as the copter won’t fly without any rate_P or I) so a more universal way to start, and actually a more informative way is to start with rate_P.
Since this is about learning for everyone, let’s do it that way. I’ll give a brief low-down on the ‘rate_D’ tune (or Dave C tune, as it’s become known) ‘ later. (BTW, that’s very flattering but I’m only relaying info from the real experts, but hey, if I’m gonna be famous, why not for doing something I love :)) Anyway....
STEP ONE - Tuning rate_P
STEP TWO – Tuning rate_D
NOTE: once you have found your rate_D you can try something interesting - you will have to hold onto your bird for this obviously. Set rate_P to zero, then crank up your rate_D as you just have. You will discover that these fast oscillations occur at pretty much the same level of rate_D, no matter what you have set rate_P to. This is why I think it’s more than possible to start tuning rate_D then move on to P. But that’s a shortcut, and this is not what this guide is all about.
STEP THREE – Tuning rate_P even more
Congratulations, your copter should be flying better than it ever has done before.
STEP FIVE - HEAD OUTSIDE!!!
For now set Stab_P at 3.0 - 3.5, closer to 3.0 if you have a high power machine, just to get you flying in stab mode. Then spend your time tuning rate_I and stab_P.
If you find your set up immediately too harsh, back off on rate_P and rate_D by 10% each, and try a lower i-term, if it's still too harsh do that again!
All that’s left is to watch the video below so you can see what I’m describing and head outside for fine tuning. Oh, and await part two of the guide and amendments from any discussions raised, then we will have a proper tuning guide that will be integrated into the wiki advanced tuning guide :D
Results for tuning in this video were
Oh and as promised, below is Part One of the Summary Guide. I aim this to be on one sheet of A4 and tell you everything you need know ‘in the field’.
Summary of what you are looking for
Too much rate P will oscillate quickly, and cause to copter to sound angry under stick input, bouncing rather than smoothly following your inputs. It will also shake more at full throttle and under hard turning.
Not enough you will not feel like you have full control. It will feel sloppy and be very easy to over correct with your inputs. It will feel delayed.
Perfect is where it feels locked in, stiff in the air, but not shaky. (although if I’m sport flying I turn it up a bit for maximum ‘wang’ and just tolerate the slight oscillations)
Too much rate_I will oscillate if you get high enough (a much slower oscillation than a rate_P shake). But quite a long while before it oscillates it will have other detrimental effects on flight performance, like a sluggish feeling or a tendancy to flip over on take-off. This is why I suggest tuning this in flight rather than in your hand/jig.
Not enough will cause the copter to get pushed by a constant wind, then it will fight back using just P. It will not hold a very firm angle during forward flight and will need more correction. This will not be as smooth as it could be in either case.
The perfect amount will cause the copter to lean gracefully into a constant wind, but also allow you to set a lean angle and stay there as you fly about. As you dial rate_i in pay close attention to the feel of the copter, you are not looking to create oscillations here at all, you should notice a strange ‘feel’ long before this point.
Too much rate_D will oscillate very fast, you will see a twitch forming then a fast buzzing oscillation
Not enough rate_D will simply mean you can’t dial enough rate_P and so you will suffer the effects of having rate_P too low.
A perfect rate_D will help fight the wind and follow your sticks as its fast to react, but will also allow you to reach a maximum rate_P level for you frame, thus giving better control.
Just a big thank you.
BTW, with telemetry, is it possible to change parameter IN flight?
or is it advisable to at least disarm the copter during parameters writing?
Dave, a HUGE thank you for the efforts. I truly believe that this is the way AC, or any OSS project becomes a major success !!!
Just a quick note about tuning Rate_I in the air -- on my last tune, I was doing exactly this - tuning in the air, starting from 0 I gain (after having set P and D to imho good values). I got to a really sweet spot, where I loved the feel and the machine was rock solid. And I'm talking about a 70 cm hexa in a not so large room (read lots of turbulence). The thing is that with the setting that I loved in the air, the copter started flipping violently on takeoff. Maybe it's just 2.8.1, maybe not. I honestly don't know but it happens repeatedly.
Once again, hats off to your guide !
Thank you, this will help many in the community who have struggled in the past to get their quad, tri tuned initially. Well done and such a huge contribution to the arducopter project and the community!
Thanks for this - it is a great resource. I wish I had had it a couple of months ago!
I've been waiting for this since the ardupirate code !
Nice work. I've been following along on the 2.8.1 release forum and you have done a great service putting it all together here. Thanks to your tuning tests and sharing the results, I now have a solid, stable and very snappy ardu-quad. This method actually worked quite well for my MWii as well- both copters are nice and tight now. Until this, the best I got was tolerably flyable.
I ended up with Rate_P at .196, I at .052 and D of .042, Stab_P at 5.945, I at .018, D at .022 and its sweet!! I never thought to take Rate or Stab D up so high and therefore taking the other params up along with, but the solidity of the airframe doesn't lie.
This is a very well balanced machine using strong motors with very stiff and aggressive three blade props and flying /tuning at nearly 2500m ASL. The word is SOLID. No oscillations, and extremely fast reactions to shaking, tilting, or stick inputs.
Yes, I always end up doing the last little tune in the air with telemetry. I often put it in loiter and adjust each parameter up and down around my bench results - obviously make sure you don't set your upper or lower limits too high, or you risk turning something that's flying into something unflyable :)
Thanks for the appreciation and inputs all! I will keep studying and updating, I'm going to update the wiki this week, unless anyone objects.
@Eric, wow! you have ended up very highly tuned! 0.042 is very high for rate_D, i presume your frame must be practically vibe-free! It must be rock solid! Have you tried it outside in wind yet?
One thing i notice is that you are using stab_D and rate_D.
And also you are using stab_I and rate_I.
I simply don't use stab_d, I've always found it to slow things down too much, especially in conjunction with rate_D, but I've not tried it yet in this release, so i think it's about time i did!
And I also don't use stab_I. I find rate_I much more reliable, and using the two together gives me strange results sometimes. But since you are happy with your results I will give all this a try too.
Well done Dave,much appreciated 8>)
Thanks Dave, very informative! Much appreciated.
Question on hexas : are we supposed to tune roll/pitch PIDs seperately ?