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HELLLLPPP What is wrong with my tricopter??

CJGFX

Junior Member
#1
After spending several week building my copter and awaiting parts etc. I finally got around to doing the maiden flights today, unfortunately all didn't got too well and I had to stop before I completely wrecked it! I know I'm a noobie at multi rotors and my flying skills are not the greatest, but I'm sure it's a setting that I've not got correct on the board.
I updated the KK2 board to the latest 1.6 firmware and that seems to be OK. On take off all seems OK and I have control of the copter, that is until I go higher and then try to reduce the throttle a little. When I do the copter oscillates and then head straight into the ground. I'm not sure if it is an issue with the self stabilising (that is set to 'STICKS' for now) I really don't know. My son managed to get some film footage of it in action.

I've looked on the internet for some setting for a beginner but everyone seems to have there own ideas. All I want it to be able to mount a GoPro on the front and do some gentle flying around... I hope someone can help....

 
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kah00na

Senior Member
#2
Make sure you have your motors connected to the KK2 board correctly. 1 is the front left, 2 is the front right, 3 is the rear motor, 4 is the servo. It looks like it is trying to auto-correct itself without much luck. Also do your ACC calibration again just to make sure. There is a sensor test where it shows what the KK2 board is receiving. Go through that menu process and make sure when the commands that the KK2 board is receiving is what you are pushing on your transmitter.
 
#3
(Keep in mind I am very new to multirotor flight.) My tricopter did this on fresh 1.6 KK2 firmware. Oscillation during descent seems to be somewhat common, so there might not be anything "wrong" other than your P/I settings. I still tweak my settings after every flight as I get closer to "perfect", but the biggest help by far was looking at the auto-level settings (I've only flown in auto-level mode so far). There, the default P was way higher than the 50 value in the P/I menu; 100 I think. I lowered this by 20, then 10 a couple times, then 5 a couple times. Now the auto-level settings are the same as the P/I menu settings. It still oscillates during descents so I still have some adjusting to do, but it is stable enough to stay under control.

Also when coming out of a descent, you might be surprised at how much throttle you have to apply to slow the copter down. At least I was. Just baby it for a while until you get those gain settings into an acceptable range.
 
#4
If you descend straight down, you get into a condition called "vortex ring state". Basically, the air going through the rotor is drawn around the rotor disc and back through again. So the whole mass of air is descending, which means you get less lift. This is a problem whenever your rotor (or prop) is stationary or moving "backwards" along the line of thrust.

Moving horizontally while descending should give you a more stable flight, as the rotors move sideways out of the vortices they are creating.

This part is guesswork, as I understand the science but don't have much experience flying. I wonder if at hover the motors are running too close to full power. When the rotors got caught in their vortex rings, you lost control authority because the motors couldn't power out of the problem. The copter oscillates because the board can't get the thrust it needs to stay stable, and the faster it falls the worse the situation gets.

Unfortunately, the only way I can think of to test this is to get bigger motors and ESCs, and see if the problem recurs.
 

CJGFX

Junior Member
#5
OK After a little more tweaking, adjusting and balancing things are a little better. I finally got around to adding the GoPro onto the front of the camera plate and from the video I'm really happy with that.
Flight wise there are still a couple of things that are bothering me. The first is that there is still some problem when I drop the throttle to descend and you can see the tricopter wobble a bit in the video. The only thing I've not done is to flash the ESC's, will this stop the problem?
Secondly the Yaw servo do seem to jump around a bit. I'll see how I go but I may get a larger servo than the Turnigy 380 digital I have on at the moment.
I'm still flying in safe mode, if I switch the safe mode off the tricopter does wonder all over the place a lot...

Time and patience I know. I really need to play around more with the settings and see if that make a difference...


 

Cyberdactyl

Misfit Multirotor Monkey
#7
The first is that there is still some problem when I drop the throttle to descend and you can see the tricopter wobble a bit in the video. The only thing I've not done is to flash the ESC's, will this stop the problem?
Even the most rigidly stabilized multirotor will wobble a bit descending fast into its own prop wash. If you want to maintain as steady a video as possible, and are not using using a gimbal, you should descend slowly or put some lateral movement into your descent to avoid the turbulent air.
 

CJGFX

Junior Member
#8
Hi Brettp2004, I wired up a harness just the Same as in Davids build video, I like to keep things as simple as possible. I think that it could be a case of just keep playing with the setting on the KK2 board and trying to make things a little smoother that way.
Thanks for the comment Cyberdactyl, a few other people have made the same comments in respect to the prop wash. Nice to know that it's just pilot error! I'll just have to change the way I fly on decent.
I'll try and get out again this weekend and play around with the P gain etc and see if I can level things out a little more.

Cheers