[solved] Quad loses control after a short while

[Andy7]

I';ve been experiencing some odd behaviour from my Quad.
I';ve only just got it working properly, so there might be a few things for me to get right. However I';ve been at it a while and have been through all the usual MultiWii 101 stuff.

It';ll take off nicely and hover really nicely with just the odd stick nudge to keep it in the same place.
But after 30 seconds or so it';ll begin to drift backwards and eventually even almost full forwards pitch control won';t bring it straight.

This is flying in stable mode on a completely still day with no wind whatsoever.

One thing that I seem to find is that if I let it start up on a VERY level surface I get a much better stability from the beginning than if I start up on a slightly uneven surface.... but maybe I';m just imagining it?

Anyone got any clues as to what';s happening to make it lose control.   


HK Talon CF Frame | NanoWii | BMP085 Baro | HMC5883 Mag | Turnigy Plush 30A | Turnigy 2830/1100kv | 3S 5000mAh lipo | 9/47 Props.

[tony]

hi m8 what flight controller are you using i had the same thing on a multi wii flight board it even dose it on winguii when on a flat surface it would stay still shake it about for a min are two then put it flat and it would learn off to 1 side and carry on going until it hit its 45 degree
fired board are chip ive put it down to and replaces the board
i replaced the board  and got naze32 there really good

[Andy7]

Hi tony. I';m running on nanowii (listed out my components in the original post to help any answers).
I was wondering if perhaps it was the fact that there was a huge thunder storm approaching messing with my MAG so I flew again but still the same.
I tried swapping my CCW props around as that';s the axis that it';s drifting in (flying x configuration btw) and that made it loads better.

Now, I';ve got a fairly powerful rig here so I doubt whether such a subtle thing as swapping props about will affect flight, so I think it may be prop vibrations affecting the PID calculations as the errors build up.

I think just taking the props off and on again reset their positions. Might be worth getting some better prop mounts perhaps . A tiny bit of eccentricity would really mess with the ACC I guess.

Anyone recommend a good prop mount? I';m using the little alu ones that came with my turnigy motors.

[tony]

if you had 1 are 2 bad props it would be a yaw issue but  your machine gose backwards and carry s on going backwards until you cart correct it with stick input would mean ive your flight board is a buff are your tx/rx is buff but if its the flight board try connecting to winguii are what ever pc based software your using to programme it and see if it dose the same on there if that gives no evidence of the same are any strange behaver try swapping out the rx are tx (borrow a m8s and bind it to his radio)

but normally if you have a bad motor are esc you get yaw issues if its a bad prop you get vibration issues

swapping over a prop and fixing your machine seams to me like you have a motor are possible all 4 motors working wrong i.e ( spinning in the wrong direction) are flight  board mounted backwards  give them a look over always worth looking at the easy thing first

[Andy7]

Thanks for the checklist Tony.
I';m pretty sure my FC board is okay but I do have a spare as I guessed I might fry it at some point.

The interesting thing is that for a while, the quad will take off and hover perfectly and react to pitch, roll, yaw as you';d expect. It';s just after a time that goes out of true.

I think I detected a little bit of a wobble you';d get if the P is too high, so I might knock that down a little.

The fact that it CAN hover at all in level mode suggests that the motors and ESCs are probably fine too as well as having the props on in the tight order and spinning the right direction. I had marked the spin direction on the motors with a permanent marker so that I don';t forget when I service the props or take them off to calibrate the ESCs

My money is still on vibration at the moment, so I';m going to connect it up to the GUI and see what the trace looks like. My props and motors were all balanced, but I had the props all off recently and I';m betting that';s where picked up some eccentricity. The little plastic adapter rings that came with the HK props are a bit crappy.

[Andy7]

I';ve reduced my vibrations to an absolute minimum now by laser balancing my props and motors. It';s flying really well now, but I figured out what the REAL problem was.
It started drifting back and left really badly and eventually couldn';t take off without it wanting to flip. This happened after a slightly hard landing, nothing more than a bounce.

What had happened was that the back-left prop mount wasn';t tightening properly and so I had started to pick up some slip on that prop hence the underpower and crazy behaviour.

Took the mount apart, fixed it and it';s really reliable now!