Help!!! Quad wont stay level when on the ground, fine in the air??????

[adamjames1998]

Hi, ive recently built my quad and i am having some little problems with it, when i set it down on the ground and increase the throttle so its 'idling' one of the motors continually increases and the opposite one will decrease, as if it is trying to level out, however i have calibrated it on numerous occasions and used different firmware all with the same results, when i increase the throttle for take off it rolls to the right, I can correct this using the roll stick but to do this every take off is quite annoying as when the quad is in the air it has no problems leveling and is perfectly balanced when in the air. I was hoping someone could help me resolve this problem thanks

Adam.


Radio:
Turnigy 9XR PRO Radio Transmitter Mode 2 (without module)
Turnigy 9XR Safety Protected 11.1v (3s) 2200mAh 1.5C Transmitter Pack
FrSky XJT 2.4Ghz Combo Pack for JR w/ Telemetry Module

Quadcopter:
S500 Glass Fiber Quadcopter Frame 480mm - Integrated PCB Version
CC3D Atom OpenPilot Flight Control Board Authorized (flashed with LibrePilot)
AX-2810Q-750KV Brushless Quadcopter Motor
HobbyWing X-Rotor ESC 40amp OPTO
HobbyKing Thin E-Prop Propellor 10x5
X8R 8/16Ch S.BUS ACCST Telemetry Receiver
Turnigy Graphene 2200mah 3s 45C Lipo Pack XT60

 

[rockyboy]

I get a similar behavior with my KK2.1 based tri-copter, and was told to simply 'pop-up' on takeoff, don't try to hover up slowly. Some of the real experts might chime in here, but some combination of feedback loops and vibrations are probably the root cause.

 

[makattack]

What rockyboy says... the ground effect from the prop wash will also increase the vibrations that might already be there.

You say you calibrated everything, but the accelerometers and gyros can sometimes be calibrated separately (not sure with librepilot) so, I'm guessing you calibrated them all and the ESC throttle range via the flight controller/software?

If so, you might be able to reduce this effect by taking off in manual/acro mode with accelerometers basically not used to self-level. That probably is why it's also getting confused.

Just be sure to be able to switch it back to self-leveling mode if that's what you're used to, once in the air. Of course, it doesn't hurt to get used to flying in manual/acro mode either!

 

[Bricks]

When you calibrated your accelerometers did you level the quad with a level I use playing cards to get my quads completely level when doing this. Desks house floors quad frames are not always level.

 

[adamjames1998]

Thanks very much everyone for the input, as im fairly new to building my own drones im still tinkering with setup and tuning etc, ill take all the help into account, thanks very much for the help

 

[rockyboy]

Welcome to the forums by the way. Most helpful and friendly place I've found online yet.

 

[PsyBorg]

What is happening is the quad is vibrating and faking the FC out thinking it is moving. The FC tries to correct and level itself but since it is on the ground nothing happens so it "Hunts" trying to find level by changing motor speeds. You see this a lot with race quads sitting on a table or on the ground for more then a few seconds.

You can isolate your FC from vibration better. You could lower the minimum throttle setting to slow the motors down a touch more at idle as they sound a touch fast. You could limit the "Idle time" before take off as much as possible. You can arm the quad and launch immediately. If you don't use a leveling mode and take off in acro you will have to control the quad more manually but it only takes a little practice and you can take off as slow as you desire in a short time. If you find yourself over correcting and the quad rocking back and forth raise your expos on pitch and roll to make it less sensitive near center stick. I was running 65% expos on my first two quads, and now down to 45% on my new one as I am more practiced.

 

[Cereal_Killer]

Electric multirotors don't need to spool up their props like a fuel powered (or large electric) helicopter, no need to run your props on the ground... When you're ready for taking off bring the throttle up quickly and TAKE OFF, get that flying machine of yours into the air where is can fly!