Autotune:0...Ground:0...Winner? It's tuning!

First - apologies for the poor video. I'm running a $30 gimbal on a standard Martinez without tuning, and a TBS with a mysterious vibe problem. I've left prop sound in, so you can hear the motors misbehaving.

Ok, my previous forays into autotuning have not had great results; today was better.

I ran autotune on my testbed, and it was done in about 3 minutes - super quick. Looked pretty tight in the air...until I tried the settings for myself. It was way too floppy, like the APM was loose or there was a drunk driving it (not me!). It was downright dangerous. The PIDs were way soft, so I tweaked them. Was much better after that. A few tiny tweaks to go, then I can start thinking about optimising the gimbal.

The Disco took slightly longer, but was strange - too aggressive on pitch, too soft on roll. Mad oscillations when in fast forward. Pitch P was tuned down, Roll P was tuned up, and D was tuned up on both. Much better. Now I just have to find that damned vibration...it's driving me mad, and the video is unuseable! Using a TBS Loveseat, but might try switching to moongel for a while.

I think I'll continue to use autotune, even after the crashes...it's not perfect (for me! Your mileage may vary), but it's definitely a quick way to get to 80% right, then it's a quick tweak or two to get to optimal. It's also a high risk way of highlighting any deficiencies in your airframe...

Views: 662

Comment by Crady von Pawlak on February 24, 2014 at 9:14am

No place else looks quite like Switzerland. Gorgeous! It's just a hunch but, aside from additional damping, I'm guessing a ruthless and fanatical approach to prop balancing (including hubs) may resolve most if not all you vibration/jell-o issues.

Comment by Crady von Pawlak on February 24, 2014 at 9:19am

Still one of the best tuts on prop and hub balancing out there.

Comment by Euan Ramsay on February 24, 2014 at 9:51am
Unfortunately the props were checked first and have been balanced, rebalanced and balanced again. All four motors have been replaced and all produce about the same level of vibes on the bench. All four arms. All the escs. All mountings checked and checked again. All screws checked and replaced as necessary. Only thing left to do is replace the frame plates!
Comment by Crady von Pawlak on February 24, 2014 at 10:03am

I must have misunderstood -- you commented in your video that the props were "barely balanced". You also mention 'anti-vibration' motor mounts. Not good. Unless your motors are bolted rock-solid to your frame you will definitely get crazy oscillations and vibration.  Motor mounts on multis must be rigid.

Comment by Euan Ramsay on February 24, 2014 at 10:45am

There are two quads in the video - the one with the jello is the TBS.

The testbed quad is the one with worn motors and barely balanced props. The gimbal is even hardmounted to the legs, but it's still vibe free.

Comment by Joe Murphy on February 24, 2014 at 10:52am

So smionK ESC lead to the first autotune crash?

Comment by Euan Ramsay on February 24, 2014 at 10:59am

Yeah, it crashed the TBS. Or rather...the cheap nasty RCtimer ESC's couldn't handle the autotune program. I replaced them with multistars, and it went flawlessly.

Comment by Euan Ramsay on February 24, 2014 at 11:01am

Apart from the PID's it chose in the end. But one set of tweaks, and it was flying great. So I still consider autotune to be useful - I'm just not expecting it to deliver the "on rails" sensation.

Comment by Hugues on February 24, 2014 at 11:43am

So to summarize your experiments for saving our multicopters (thank you), what were your identified root causes for the failed auto tune ?

Comment by Euan Ramsay on February 24, 2014 at 12:44pm

lol Hughes.

Cause 1 (test bed): still unknown. A battery failsafe engaged (outside of the failsafe range I might add), and the land event did nothing of the sort

Cause 2: The RCTimer ESC's freaked out, possibly due to either a simonk issue, or just generally being rubbish.

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