Electrohub Spider (Dead Cat) Quad (KK2.1.5 FC w/ Steveis 1.8) Self-Level Issues

[Xonos]

SOLVED!!!
Replaced cheap ESC's with slow refresh rate with ESC's that came with SimonK firmware. Now the quad pops into place and overall runs amazingly. 0 wobble with gain set to 75. I'm going to try 100 later today and I'll post results at different settings.

Velotech Magic Multirotor Speed Controller 30A with 2A BEC SimonK Program
See: http://www.buddyrc.com/velotech-mag...ontroller-30a-with-2a-bec-simonk-program.html
Note: These esc's do not come with bullet connectors - you'll need to solder your own on and shrinkwrap them. You'll need 5 sets (3.5 MM Bullet Connectors) (or 5 of whatever you need that's already setup on your build - for me it was 3 males and 2 females) per each speed controller.

Alright so first off, first time poster & this is my first multi-rotor build. I've watched & read just-about every tutorial series I could find when I started this project. What I have is an electrohub body using the KK2.1.5 FC which I've flashed with the Steveis 1.8 firmware.

I've got an issue and have continued to struggle with understanding the self-level gain/limit in correlation with PI P-Gain/P-Limit/I-Gain/I-Limit (roll + pitch (linked) & yaw). I have an issue with oscillation (or a slight wobble) which makes me incredibly nervous to test out flying at higher speeds. I am still a novice pilot however, I am lucky to have started flying on a MCPX2 which gave me a 'crash course' (literally, repaired this thing over 20 times) to flying, period. I can fly this quad without self-level with no problems. The wobble doesn't really happen until I turn on self-level (which I have set to a switch on my transmitter). The wobble is very slight but the more aggressive I am, the more prevalent the wobble is. I have recorded a video that kindof gives an idea of the flight experience. I recorded this at night so to avoid irritating my neighbors with a high-pitch whine, I did this in my garage with closed doors so it was a bit turbulent in there. Regardless, you'll see the wobble occur but you don't really see it as much in this video as it does outside with wind. I was wondering if anyone else has built a similar quad with this flight controller and if they had the same issues. If so, how did you resolve it? Were the ESC's the root of the problem? Is this FC just not that good? Should I not be using the 10"x4.5" props in this configuration? I chose the DJI-style Carbon Nylon props which seem almost indestructible. I adjusted the self-level to the point of losing control (when I set the gain to 65). It rolled left and right at 45 degree angles until I did an emergency landing.. the props hit the dirt and stuck in leaving my quad embedded into the ground at a 80 degree angle. lol!

Here's a picture of the body layout that I've got thus far. The flight-controller is hot-glued onto the foam case and the foam case is thoroughly hot-glued onto the top of the electrohub. I used the ACC Bubble tool in the menu to ensure that ACC is 0,0 centered afterwards.

Anyways, this is my build:

Body : ElectroHub Quadcopter Kit
https://store.flitetest.com/electrohub-quadcopter-kit/

Spektrum Receiver : AR610 6-Channel DSMX
http://www.horizonhobby.com/SPMAR61...5&cadevice=c&gclid=CKyqh5_CwMECFcQ-MgodrHUApQ

Flight Controller : Hobbyking KK2.1.5 Multi-rotor LCD Flight Control Board With 6050MPU And Atmel 644PA
https://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=56269

ESC'S : Turnigy Multistar 20 Amp Multi-rotor Brushless ESC 2-4S
https://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=47400

Motors : Multistar 2212 - 920KV Multi-Rotor Motor Set w/CW and CCW Threaded Shafts
https://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=62796

Props : Gemfan Nylon Carbon DJI Style (required with Multistar motors I have) 10x4.5 (Not Slo-Flyer Props)
http://www.helidirect.com/gemfan-ny...ck-props-set-1-cw-and-1-ccw-2-pcs-p-30724.hdx

Battery : Turnigy 2200mAh 3S 30C Lipo Pack
https://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=14962

Battery Alarm : On Board Lipoly Low Voltage Alarm (2s~4s)
https://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=41178

 

[Xonos]

I also forgot to mention this. I found a tutorial on youtube regarding the Spider/Deadcat quad PI Settings, Self-Level Settings & Mixer Editor configuration using the sin of the angle of the front & rear props. This tutorial covers the SK 450 body which assumes that the props are at a 70 degree angle. I haven't pulled out my protractor to verify that the electrohub spider config is set at the same angle which very-well may be my issue.

 

[Balu]

As for the mixing, the Stevie's firmware manual has a nice description on how to calculate those values (Appendix F).

IIRC a slow wobble like this was a too high I gain. I didn't experience that yet though, but you can see the problem in this video (at 1m50s):

You should not use the values of others but try to optimize it yourself because every copter is different. It depends on the frame, the motors, the props, the weight, etc. so you really need to tune it for your machine.

The section on the PI Editor has a nice step-by-step instruction on how to tune your copter.

 

[Xonos]

With a dead-cat configuration, the back is seemingly always heavier than the front due to the positioning of the front left and right motors. Where does center gravity come into play with the positioning of the flight controller? Perhaps this is also another variable? I'll look over this video & the resource you posted and return with my results. I appreciate you reading my novel's worth of a post.

 

[cranialrectosis]

CG should be where the accelerometers are. On a KK2, that is just in front of the LCD.

To tune your copter you need to be able to hover in acro mode (without autolevel). Tune autolevel after you tune PI in acro.

I concur with Balu. I think your I gain is too high but I don't know how the copter flies in acro mode so I can't suggest what to change.

 

[Xonos]

Ok so this is what I've discovered thus far. Because of the dead cat configuration, my front left & right props create some backwash with the rear blades due to them being 10" and being a couple inches away from the rear props. You hear a 'whipping' sound while flying. I helped my brother build the exact same build but in X configuration and he had a slight wobble issue which we failed to tune out entirely. He extended his booms to 12" instead of 10" and found that this has eliminated the wobble completely and it is now flying stable with self-level.

Considering my props are much closer together (front & back), this is creating some of the stabilization problems. On-top of this, many tutorials suggested setting the gain much higher (75 P Gain in Self-Level). Doing this with his x-quad and my spider quad simply caused horrible results resulting in an immediate crash landing from 3-5ft in the air. I've found that these ESC's (Turnigy Multistar 20A) are slow. The instructions being sent from the flight controller do not process (through the ESC) in a timely manner to speed up or slow down the corresponding motor at the exact moment needed thus resulting in the wobble effect. A friend of mine that's mentored me through this process had the 15A version of my esc's (on a batbone tri build) and he upgraded to the Velotech Magic Multirotor Speed Controller 30A with 2A BEC SimonK ESC's noticed a night and day difference. He set his self-level gain to 100 and it literally snapped in place immediately versus the noticeable delay that we experience. So all-in-all, if the ESC's I've ordered do not fix this issue after tuning it as much as possible - I will try extending the booms and work on tuning once more. Also I agree with you on tuning without self-level first... I will definitely do this and post my results once this is done (along with the settings I used). Hopefully I can help someone interested in this build avoid these issues I have experienced. Afterwards, I will post the part list and instructions.

 

[Xonos]

Just incase anyone stumbles upon this thread, I was able to get rid of the wobble completely by replacing these terrible ESC's. As I suspected, the refresh rate was the culprit. I bought these instead:

Velotech Magic Multirotor Speed Controller 30A with 2A BEC SimonK Program
http://www.buddyrc.com/velotech-mag...ontroller-30a-with-2a-bec-simonk-program.html

The quad flies better than I ever imagined.. I will post a video of my results as soon as possible.

 

[Xonos]

I took some test flight footage yesterday using a wide-angle mobius camera that I just mounted to the bottom with velcro so the stabilization isn't so great but the wobble is gone. Sorry for the poor editing and canned youtube music but atleast I caught a DJI Phantom flip and crash in the beginning.

One thing to note though - I had to reset my settings back to factory defaults. The new ESC's are making my motors get real hot in the front. The front left and front right motors seem to be over-compensating too frequently (my assumption) so I think I need to tackle the mixer editor again.

Ignore the timestamp, my mobius needs to be configured - I just got it yesterday.