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.
Yes and No. Yes in that it holds the position you have left it at.
No because you now tell it what position to go to by instructing a rate. In Stabilize the stick angle is the angle of the copter, in ACRO the stick angle is the speed your copter rotates.
If you turn the ACRO_BAL_PITCH and ACRO_BAL_ROLL up to 200% you get a flight characteristic that is very similar to Stabilize but smoother.
I turned RAW on this morning so I will be able to supply some log files after my next flight, however I dont see INAV as an option in the Wiki, is this something new/else?
Im pretty sure that my quad hovers close to mid stick and it doesnt drop when I go out of alt_hold.
What exactly does the new Accel section control/do?
I just finished a Tricopter and tuned Rate PIDs. The copter hovers well, but I am not very happy with the tail. It holds well, but when I yaw and let the stick go, it waggles 2 times.
What PID values should I try< to change? I allready tried yaw_rate_p. That did not change anything. What's about yaw_rate_i? The default is 0.0150, but it cannot be set to channel 6 tuning, and so it is guesswork, how to set it.
Could anybody help me tuning the tail of my tri?
I did a quick hover test this afternoon. My quad hovers at between 35-40% throttle. I guess this puts me just outside the 20% deadband range.
I've attached a log file from my short hover test. RAW logging was enabled...
I didn't mean StabP, I meant Rate P!
I'm a plumb.
Help team, My X8 Octo seems dialed in, If I fly from A to B it holds the angle, but when I pull back on my banking angle it lifts or raises a few feet, what do I adjust?
Also mentioned a few posts up is Rate I=1 to 2 times Rate P? is this correct? I dont want to slam my X8 into the ground if I can help it! :)
Your accel data looks good so you shouldn't have a problem getting Alt Hold to work well.
I would suggest dropping the THR_ACCEL_P and THR_ACCEL_I terms back a little. 0.5 and 1 should be a safe start. Just keep that 1:2 ratio between P and I to start with. These parameters adjust how much throttle is applied to accelerate the copter vertically.
A log doing an Alt Hold with INAV tuned on (just try enable INAV in the logs) would help to see what is happening with your Alt_Hold. You also have a Baro so that may be causing you to jump too. Initially I would test Alt Hold without the baro enabled.
It is normal for the copter to increase altitude if you fly forwards quickly then pull back. I am assuming you are talking about Stabilize mode here.
If you are happy with your roll and pitch control you don't need to worry about changing the Rate I term. I personally like to have my Rate I term larger because it builds up and down quicker. Provided the IMAX term is reasonable it is pretty safe.
so If my P is .15 and my D is .008 what would I set my I term to? I dont 'feel' any differance @ .0100 or more, Would i set it to .15 like my P?
I would suggest that you make it equal to P or double P. But just to be safe I would set it on a slider from zero to double P and move it up slowly. If you are right on the edge with your tuning there is a chance that it might push you over the edge but I doubt it.
I have the same motors/problem. Only my shaft is what is spinning, not the prop collet.. Seems I cant get the grub screws tight enough to hold it. Ill be purchasing a set of prop drivers tomorrow. What airframe are you using? Is it STO as well? Im pretty happy with their stuff, other than this motor problem.
I've just installed 2.9.1 on a mini quad. Can I still follow this tuning guide or have things changed too much?