Finally, someone has created a PID tunning howto video, from scratch to perfect stabilize flight, that I think will be very useful for the arducopter community, specially for those flying non stock frames.
The concepts are already in the AC2 PID tweaking guide developed by Jason, but a visual howto helps a lot!
The guide has been created by Menno (joebarteam), an active user of the megapirates community in rcgroups. Full credit to him, I'm just spreading his post.
First, acro mode tunning (which I always discard, but I'm realizing it is pretty relevant):
Second, stable mode tunning:
The full post with Menno comments is here.
Note:
If the arducopter developers think it is useful maybe it could be added to the wiki (with Menno permission obviously).
Comments
first of all, make sure that all the motors are running in the correct direction.
Recalibrate the ESCs throttle range one by one.
If this does not help, connect the shield to the Mission Planner and watch the heading. It shouldnt change after it has catched the right heading.
I assume you are using gps and magnetometer and the declination bug is set correct?
Greets
Marc
Just one hint on tuning Rate_P for acro and stab mode. The stab rate_p should be lower than in acro mode, as stabilze mode is two contol loops nested around each other.
Anyway, even if you don't use acro mode for flying, try to find a good setting as this will give you a good setting to start with for tuning the rate_p setting in stab mode. Take care of the rate_i term in acro mode too, as this defines how to copter will try to hold the desired angle - or not.
Greetings
Marc
very interesting. i will try to increase stabilize I to eliminate wobble in fast descents.
PID Tuning has always been tougher for me. The method shown in these videos looked promising (You can read it a 100 times but sometimes it helps to see). Tuning acro mode then on to stabilize.
For myself acro mode was best at around Rate P (Roll/Pitch) of about 0.23 or so, maybe a tad lower, 0.25 had oscillations.
Then on to tuning Stabilize P (Roll/Pitch) I had fast Oscillations... I had to lower Rate P down to below the defaults (0.145) to 0.130 to stop them.
What I ended up with was about the PID's i had originally was using.
Acro mode with 0.130 rate P is not flyable, while rate P of 0.22 is... However that much rate P in stabilize mode created a faster oscillation which only goes away when reducing rate P.
I guess I don't understand that. That basically (for my tri frames) removes acro mode from my choice of modes since it is not flyable. Not that I have ever really used acro mode but it would be nice to know what the problem is.
I have found that I can do PID tuning of the acro mode rates while in stable mode: with too much rate_P the quad will have very rapid short oscillations, or jitters (unlike the oscillations from having too much stab_P) for my taste I just lower Rate P until those rapid oscillations are gone, but not any further. Although my method does not really allow an easy way to find Rate_I, I think you do need to fly in acro mode to find the optimum Rate_I.
Setting Rate_P as high as possible without oscillation contributes to the quad's ability to hold still with disturbances, it is, basically, the "brakes" of the quad, when the target rate is zero, and when the target rate is non zero, it is like having a very high force preventing the rate from deviating from where it should be. In my opinion it is best to set Rate_P in this optimal spot, not so much a matter of taste, but a matter of ability to enforce the desired rate with as much force as possible.
Stabilize control is a controller around another controller: It tells the rate controller what rates to use depending on how far off the target angle is from the actual angle. I find that there is a wider range of "setting to taste" of this, although I still like to set it to just around "Critical" basically just under oscillation. Lowering stab_P from there makes the quad feel more "gentle" but not as quick to respond.
In terms of the quads ability to resist outside disturbances like gusts, the critical settings seem to work best for me.
I am also glad to see on your video a demonstration of using high climb rates to test PID settings, since PID settings have to be a good compromise for the widest range of throttle, even if the delta thrust for delta PWM of a motor / prop is variable in its RPM and loading range.
Dude this is just what Ive been looking for!
Very good find Jose!
Which frame you are using :)