Hello Everybody! I've been stalking this forum for some time as it's helped me immensely get to where I am now. And I very much appreciate all the help that everybody has provided.
Given that I now have a few flights under my belt, I had a couple question regarding PID tuning so that I can really dial in my quad. First, I'll provide some good background as to what I've been up to and how I got here so you understand what I'm looking at.
I've always been infatuated with RC aircraft, just never had the wherewithal to make the jump from land to sky. That is until I saw some of Juz's videos on YouTube that I made it work!
So I went out on a fact gathering quest to find out as much as I could in a relatively short amount of time, and utilized a bunch of different resources. In the end, I pulled the trigger on the build below for the following reasons:
a. Knew that I wanted a fully-capable autopilot with great support so when I run into issues like this I have help (:
b. Saw what Juz and other people were doing with this innovative frame
c. Knew that I want some serious acrobatic ability
d. Knew that I want some really crisp video without any wobbles
e. Thought it was a great place to start - not too big, yet would be stable enough for me to handle as a beginner
Thus, I started amassing components and wound up with the following:
-QAV400 frame from FPVManual.com
-Tiger Motors MT-2212-13
-Tiger Motors 18amp ESC
-ArduCopter APM 2.5 / GPS / Telemetry
-Futaba T8FG Super
-HobbyKing NanoTech 4s 3300mah
-Started with the Graupner 8" props, but after a few incidents I couldn't source them anymore (and probably a good thing b/c I've gone through a few!), so now I'm onto a set of Nylon GemFam 8"
In addition, I just grabbed up some FPV gear but that's for another story. For now I'm sticking to LOS until I've not only honed in the PID tuning, but also my flights kills for obvious reasons.
So, long story shorter, after I got everything together, I soon realized that the standard PID settings in the APM were way overkill for this frame. As soon as it would take off, it would wobble uncontrollably and I was forced to kill power, sending the frame a couple feet to the ground. A few minor components later, we're back in action.
Now, I've verified all the rudimentary items like:
a. That the motors are all square / true
b. That the props are all in good order (yet I'll admit, seem to be somewhat flimsy)
c. That the CG is nearly perfect on both axis
So, that brings me to where I am with PID tuning... I've used DaveC's PID tuning guide, and I'll say that it got me pretty far, but I feel like there's something major that I'm missing here. Aside from tuning in Acro mode with the quad attached to a frame / my hand, I fly 100% in Stabilization mode to try and get this thing buttery
The issue: While the copter is nearly perfectly stable in horizontal flight / just sitting there, once I start to pull some "G's", it gets fairly fluttery with some serious oscillations, but is always fully capable of pulling out of it.
With some in-flight tuning, I was able to get the RATE_P upwards of .1520, but once I landed and took off again, it went right back to that uncontrollable wobbles forcing me to cut throttle or it was going to wind up the next town over.
Here's a video from one of my first Recorded Flights that really exemplifies the issues that I'm having... It's very apparent both on take-off and when I cruise around corners.
Since this IS the home of ArduCopter, is anybody else flying this frame? What PIDs are you guys using? I've tried my darndest and can't find anybody else helping with PID info. All I'm looking for is some guidance on where I should explore next with this issue. Higher RATE_P while lowering STAB_P?
Thanks a ton guys, certainly look forward to posting a ton of videos in the future to help support the community!
Hey Clint, thanks for the comment! I do get the wobble in acro with stab P at zero. In-fact, I get some extremely strange fidgeting in Acro where every couple minutes the quad will seem to be reacting to a strong outside force, then it is always able to calm itself back down. Very strange.
Pitch and Roll are locked. Originally I had it down rate_p down to around .9. I'll go ahead and lower the rate_P back down and raise the Stab_P like Brian says below and see how that responds.
I'll go ahead and try giving a reduced rate_P and raising stab_P back up to the factory standard. Looks like your rate_I is substantially higher than mine too, I'll look into that as well.
Im new to quads but in my opinion your rate P and D for the roll axis is too high, Set it to P = 0.07 and D = 0.004 and I = 0. Work your rate P roll up from there or even leave it if it feels ok, Keep your stab the same because if it wobbles at 0 then its not your issue.
Tuning my QAV500 I start low and work your gains up until it feels nice and not to the extremes where you see wobbles, once it feels nice you can increase Stab P till it gets abit more responsive.
For along time Ive been trying to tune to the absolute edge but at this stage of my skills I enjoy abit of lazyness to my quad.
Also, Due to the unsymmetrical weight distribution of the QAV your gain can be cranked up on the pitch, Im yet to see pitch wobble even at rate P pitch at 0.2!
PS, Juz is using openpilot, mines on its way for my second less lazy build!!
Unfortunately (well kind of, I'll explain in a sec) it looks like I found what the inherent issue with the setup was. For some reason my ESC was on its way out for some time now, what seems to be my last dozen flights. I thought it was one of my motors because of a recent crash / dirty bearings causing it to be harsh to the rotation. I cleaned that motor several times and thought that it would be able to persevere through any issues. But my last flight today has proven that a faulty ESC has finally caused a catastrophic issue and brought the quad down. Luckily it only suffered a couple bent arms (will be easy to fix).
In an effort to prevent this from happening, I'm upping the amps on the ESC to the FPVManuals 30amp SimonK in an effort to prevent this from happening again.
I'm 99% sure that's what my "wobbles" were in Acro mode as there was almost no Stab-P involved when I was running it.
Other than that, Brian's response below has been very helpful. It appears that I was just chasing a ghost this entire time and it led me astray.
My most recent and very stable settings:
Also do as Clint suggested, unlock your roll/rate PIDs and crank up only rate pitch. I'm using stock values on rate pitch while my roll rate P is down to .095