KK2 Oscillations! HELP!

[Flyingninja]

Hey,

So I bit the bullet and got all the stuff to build a quadcopter. A H-King KK2, 4 TGY Aerodrive DST 1200s and 4 H-King 20 amp esc's.

When I take off the quad starts to oscillate, sort of like this: https://www.youtube.com/watch?v=W5kI8KhlwTw

But it's all the time, not when I bang the sticks.

I messed with the p gain and nothing changed.

This happens mot in auto level, but it is still a problem when auto level is off.

So, what's wrong?

Thanks,
Flyingninja

 

[razor02097]

Oscillations in a quad is kind of like tracking down an intermittent miss in a car engine... a lot of times it is something simple but sometimes it can be something that will drive you out of your mind.

What props are you using and are they balanced?
What frame are you using?
Are you using any sort of dampening device like a gimbal or vibration isolator?
How did you mount your KK2 board?
Stock firmware or did you flash something else?
What are your P and I gain numbers? The stock numbers in my experience are way WAY too high.

 

[cranialrectosis]

Video of your copter can help.

Razor is asking the proper questions for a full diagnostic but from your description I would suggest P gain too high.

To tune P and I you MUST fly in acro mode. Autolevel hides the impact your settings have. You have to tune in stages. First tune acro then tune autolevel.

If you tweaked P and then flew in autolevel you can't see the impact.

If your copter wobbles on takeoff in acro mode, particularly if it has the tendency to wobble higher and higher without you increasing throttle, your P gain is too high.

 

[Snarls]

Really make sure that you calibrated your ESCs properly. They should be calibrated all at once with the KK2. I thought I calibrated my ESCs correctly on my Disco build, but was getting constant oscillations. Went back, calibrated correctly, and the thing flew way better.

 

[Flyingninja]

Thanks guys! I have partly fixed the problem. The first frame I made was made of some really flimsy plywood and the motor mounts had a lot of slop. I made a new frame from a $7 Ikea desk lamp and there is no oscillation in acro mode. I still have some tuning to do.

When it is in self- leveling mode there is still bad oscillation.

+razor02097: I have apc 9x6 props and they are fairly balanced.

The board is mounted in the middle of the frame with the buttons to the back of the quad.

The frame homemade.

I'll get you the p and i numbers later.

+Snarls: I'll re-calibrate my escs and see if that helps.

 

[razor02097]

Pretty sure on the stock firmware there are different P and I gains for self level mode. If it is flying fine in acro mode your issue is likely not hardware.

 

[Craftydan]

KK2 self level is a P controller. It does have a separate setting on another screen. Dialing it up/down generally affects how quick it snaps back to level, and more often than not, I recommend it be kept modestly low -- let go of the stick and it eases back to level, not snap. It's up to personal taste, but I find if you have it to snappy, you'll spend more time fighting the craft's desire to return to level rather than controlling the craft.

When I've seen the airframe fine in acro, but shake in self level, I'll back down on the pitch/roll P gain 5-10 points and it's usually been enough to cut out the shake in self level, but still hold fairly tight in acro.

 

[cranialrectosis]

I forgot to ask one big KK2 question.

What version of firmware are you using?

If you are still flying stock, that's half the problem.

 

[Flyingninja]

Here's my p and i gians:

P: Aileron, elevator, rudder
65 gain
50 limit

I: Aileron, elevator, rudder
30 gain
20 limit

I was just flying it about 10 minutes ago in 20 mph wind and it was pretty solid, (in acro) but I had to be "flying" it, to keep it in a nice hover.

Here's my p gains in self-level mode:
50 gain
35 limit

 

[Flyingninja]

Its version 1.5

 

[cranialrectosis]

The KK2 always needs to be 'flown'. Even in autolevel you will need to maintain attention and concentration. The KK2 is not an autopilot.

You will learn faster and better if you fly the KK2 in acro mode, but seriously upgrade the firmware.

I think this is Steveis page. I haven't flown a KK2 for a few years now but I think I flashed from 1.5 back in 2013 or so. I think 1.5 is pretty old.

 

[Craftydan]

Agreed.

The kk2.0 (not 2.1.x) stopped at the 1.6x versions, and it was a nice improvement. Flyable, but better after the flash (NOT the case for the 2.1.x). Frankly the 1.6++ version was my favorite, with a mixed-self-level mode which acted like acro on the sticks, but when released returned the craft to level -- similar tot he Horizon mode on more modern control boards.

As far as your gains . . . that depends on your parts. Some ESC/Motor combos can tolerate higher gains happily, some need lower gains. Balance/vibe on your system can also dramatically affect the ideal gain.

That's all to say, I can't see anything wrong with your numbers, by just looking at your numbers . . . but I wouldn't be able to anyways.

Balance your props and motors as best as you can, add some vibration isolation to the board if you haven't, then tune P until it stops jittering on commands, tune I until it stops drifting in acro. Your goal is for as high a P as you can get and not jitter, and as low an I that it will hold the commanded attitude.