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.
rate I is too high by the sounds of it - put it back to 0.1, this should help alot!
yup, I've had to drop my rate_p to about 0.14 or lower, and rate_d to 0.004, the new interial is much more sensitive.
I would agree with Dave. I would keep the I term to 1 or 2 times the P term.
The start stop effect you are seeing can sometimes be caused by an excessive D term but your D term looks fine to me. So maybe this is the I term as well.
This is an interesting data point! Let us know how you go.
I I humbly understood that was the case, I was simply lazy the second time I referred to it.
The default Stab P for the newest FW is .145 and the last was indeed something like .175 (not that any of these figures mattered where I was at that time since I had no idea that I wasn't calibrating my accels!)
Not had a chance to fly yet, hoping for better weather tomorrow!
I indeed meant Stab P,
Yeah, it would appear the default has changed in the latest FW.
Really sorry, just getting used to the format of the forum and completely missed your post,
As you'll see from next posts I think I have sussed it but want to thank you for your suggestions and helpful advice.
I may still need to follow some or all of it since I've now rebuilt the lot into a TBS disco frame!
I've been trying to use your tuning method with ver 2.9. It's a weird behavior, I can seem to adjust the rate P & I term anymore as my hex is always trying to auto level even in Acro mode! Is it the new self recovery function that is causing it? I previously have good success with 2.8.1.
To use rate only ACRO you need to set AXIS_ENABLE to zero.
The new ACRO mode stabilizes the airframe to keep it where you left it. It also has an auto balance feature that levels the airframe. To stop this you need to set ACRO_BAL_PITCH and ACRO_BAL_ROLL to zero.
I ventured out today to follow up with the testing and tuning. I tried to get video from a hatcam and a video recorder but wasn't too successful, rig was just too far away to make out.
Changing only R_I pretty much anything between .1000 - .5000 induced those wobbles on the bank turns...it wasn't until I turned it down to .0500 -> .1000 that it started to improve, but that came at the expense of denying the calculation sufficient I_Term to fight external forces. In other words, Loiter was pretty solid (20mph winds) with higher I term, but when I dropped it down to .0500'ish there wasn't much that could keep the rig from sliding.
I'm still running a release candidate for 2.8 - I'll be flashing the rig with 2.9 later on tonight - just in time for us to get 2 days of snow and the rest of the week in single digit temps. Talk about a tease today - 45-50 degrees but 25-35mph gusts. So not fair.
I had to call it after 2 batteries when one gust blew my rig across the field. With the failing light and little I_Term to fight, I almost lost the rig.
I need to dig up my flight logs - will post those a little later.
I'm getting to the point where I want to try decoupling pitch and roll. Pitch seems fine, I only see the oscillations on roll inputs and only when I go into steep bank turns.
Is there any tuning that can be done to eliminate the initial drop when engaging alt_hold?
My quad drops about half a meter when I engage alt_hold and then goes back up. Once Im in alt_hold mode its locked on dead at that height, but when I move up and down it kind of "bounces" at the height where I stop it...
Sounds like a tuning issue but the initial drop in altitude shouldn't happen. Similar things have happened to people with high powered copters. When hovering in stabilize they need their throttle stick at say 1/4 to 1/3 so when they switch to alt hold they get a sudden drop until they increase their throttle to 1/2.
The bouncing may be caused by a high Accel_P and I term. Maybe try dropping them back to 0.5 and 1.
Logs with INAV and RAW turned on are always helpful when tuning.