Flight problem

[zed961]

Hello everyone,

Hope you are doing well!

I completed the construction of my first quadcopter and took it for a test flight. However its behavior is really random. I'm flying in arm (default acro mode) mode, sometimes my quadcopter flies in a stable way and sometimes it just drifts. They both happened during the same flight test and under the same conditions.

Acceptable flight:
https://www.youtube.com/watch?v=4HLmJfm ... e=youtu.be

Bad flight:
https://www.youtube.com/watch?v=7XG9Nxp ... e=youtu.be


Components:
- Multiwii pro
- ESCs 20A Skywalker
- Motors Emax 935 KV
- Props 10 x 4.5
- LiPo 2200 mAh - 3S
- Frame: DJI flame wheel 450

As for my TX i am using an Arduino UNO board that acts as my transmitter by sending PWM signals via Xbee to the FC. Maybe that is the problem? Maybe an arduino cannot replace a real TX?

What i did so far:

- Calibrated ESCs (each one alone and also using Multwii special technique)
- Calibrate ACC and mag
- I tried the ACC trimming by going full throttle and then going the opposite direction of the drift but it didn't work out
- I tried to fly in horizon mode but my quad can't seem to take off properly it just stays close to ground no matter the level of throttle i give and it drifts

-PID tuning:

Roll 3.3/0.03/24
Pitch 3.3/0.03/23
Yaw 10/0.045/0
Altitude 6.4/0.025/24
Pos Hold 0.11/0
Pos Hold Rate 2/0.08/0.045
Nav Rate 1.4/0.2/0.08
Level 9/0.01/100
Mag 4

RC expo 0.65 Roll/Pitch rate 0.9
RC rate 0.9 Yaw rate 0.65

Thr MID 0.5 Throttle PID attenuation 0
Thr EXPO 0


It seems that I am missing an important concept. Any help would be much appreciated !

Take care!

PS: If there is a problem playing the videos please let me know and i will fix it immediately.

[Cereal_Killer]

I will watch your videos and try to address your actual problem a little later today but first please see this thread and read threw it, he was trying to use a arduino / DIY radio setup and we discuss why that's never a good idea. Not to be hard on you either but a DIY radio setup is NOT appropriate for a large quad with 4 super fast, 10" long SPINNING BLADES on it.

viewtopic.php?f=18&t=6345

[Cereal_Killer]

Videos are set to private.

[zed961]

Thank you Cereal_Killer for your reply. The videos are public now you can watch them.

Arduino has PWM pins which is what the FC needs ro drive the motors no? Do other tx send something other than PWM signals?

I will be sure to check the link you provided.

Thank you again

[zed961]

I read the thread in the link you suggested. The primary issue debated was that his quadcopter wasn't able to lift however as you will be seeing in the videos my quad is lifting and it can lift higher also but i am afraid to try that because it is not 100% stable so i am afraid that at high speeds the drift will be so bad that it will crash my quad.

Things that affect stability:

Balanced weight
Calibrated ESCs
Correct speed distrution by Multiwii pro
Tight frame

Any other suggestions?

[FengShuiDrone]

Not to be hard on you either but a DIY radio setup is NOT appropriate for a large quad with 4 super fast, 10" long SPINNING BLADES on it.
viewtopic.php?f=18&t=6345

I think CK was trying to make a safety point.....right CK??? Someone missed the point and it wasn't me.

[zed961]

Hello FengShuiDrone,

I am attaching my quad to a dumble so that it doesnt drift away in a crazy way and cause damages. I just want to know the cause of the drifts that i am getting in those videos and why is there such a random behaviour.

Any tip can hugely help.
Thank you in

[FengShuiDrone]

Hello FengShuiDrone,

I am attaching my quad to a dumble so that it doesnt drift away in a crazy way and cause damages. I just want to know the cause of the drifts that i am getting in those videos and why is there such a random behaviour.

Any tip can hugely help.
Thank you in

It is easier to help people who use a real TX. I would suggest plopping down about $60.00 for a Turnigy 9x with receiver. Then, problem solved. Aside from that I would look at my throttle expo and increase it to .35 or .40. Throttle mid is good at .50 if your craft hovers at mid throttle. If not adjust your throttle mid to reflect how much throttle it takes to get a good hover. Your RC rate looks a little high. Try closer to .35. I would try lowering my roll/pitch rate to 0.00 unless you are looking to do flips while in horizon mode. Your yaw rate is also too high for smooth flying. try starting out at 0.00 on this one too. Some of your setup numbers don't bode well for a new pilot. Also, you said you are flying in rate mote. In this mode you have to manually correct ALL flight characteristics. If you take off pitching forward, the craft will continue in that direction until you, the pilot, reacts and corrects with the correct pitch maneuver. If your TX is not centered up using subtrims and endpoints you will have problems. Also, if your TX has a lot of slop in the sticks you will need to uncomment your //#define DEADBAND 6 option and change the value to 8 or 9 if you need to.

[Cereal_Killer]

My advice pretty much mirrors FSDrones with the exception that I'd recommend a Devo 7E (for pretty much the same price) but a 9x is a fine choice too.

Having said that, are your "sticks" all centered? Are you able to give it stick commands? Does it always happen to drift the same way? Have you tried trimming the ACC before?

Oh one more question, when you connect to the GUI and (WITHOUT PROPS) give it throttle watch the little bar graphs on each motor (just below radio data in 2.3/2.4), are they even?

[zed961]

Thank you FSDrones and CK for your replies.

First, FSDrones I will do the modifications that you proposed and get back to you.

CK what do you mean by stick commands? And in the GUI the motors don't have the same values at all times in horizon mode however for the rate mode they are pretty close and sometimes equal but when i rotate my quad and play with it then get it back to its initial stable position the values dont get back to being equal.


Thank you again!

[zed961]

One more thing CK, it does not drift the same way everytime it is more of a random drifting each time.