Jeuke26

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Title says it all, it was doing some tests lately and noticed in attitude mode the quad wants to fly forward even when it was calibrated on a perfect level surface and as shown in Librepilot.

There's is zero trim in TX, all motors point straight up. The quad flies perfect flat in rate mode and if it weren't for any wind would hover on the spot.

Again, this is a first timer as it didn't do that before.

Oh yes, CG is spot on and moving the lipo didn't do any  difference. And yes I calibrated everything in Librepilot and still same issue.

Mateusz

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Re: Quad drifts forward in attitude, shows perfect level in Librepilot
« Reply #1 on: May 21, 2016, 09:38:33 am »
Rate mode uses only Gyro. Board level calibration calibrates Accelerometer. Attitude mode uses Gyro+Accel. So it does not matter that it is hovering in Rate.
This means that you didn't have quad-copter or flight-controller perfectly level. You can account for that by tuning Virtual Board Rotation and adding some pitch. I use that to account for my titled motors, and I get perfect hover in attitude mode.

jbarchuk

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Re: Quad drifts forward in attitude, shows perfect level in Librepilot
« Reply #2 on: May 21, 2016, 09:43:38 am »
Perfect is a theory. Reality is a fact. Pixels are a representation of reality and not very accurate at that. Adapt/modify your theory to match reality.

Mateusz

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Re: Quad drifts forward in attitude, shows perfect level in Librepilot
« Reply #3 on: May 21, 2016, 10:28:40 am »
@Jeuke26
You can have a look at Wiki https://librepilot.atlassian.net/wiki/display/LPDOC/Attitude+Setup in the dual loop controller image you can see that Rate mode only uses Gyro to stabilize, so leveling of accelerometers does not affect that. Hope that gives clearer picture and helps :)

anypis

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Re: Quad drifts forward in attitude, shows perfect level in Librepilot
« Reply #4 on: May 21, 2016, 02:03:45 pm »
Check your wiring. You need to put your board away from high current cables. I had the same problem with chinese PDB's. Now i changed thin esc cables with a bit thicker ones and twisted.

Jeuke26

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Re: Quad drifts forward in attitude, shows perfect level in Librepilot
« Reply #5 on: May 21, 2016, 04:18:32 pm »
Rate mode uses only Gyro. Board level calibration calibrates Accelerometer. Attitude mode uses Gyro+Accel. So it does not matter that it is hovering in Rate.
This means that you didn't have quad-copter or flight-controller perfectly level. You can account for that by tuning Virtual Board Rotation and adding some pitch. I use that to account for my titled motors, and I get perfect hover in attitude mode.

Thanks for the tip, could have known that. But the quad really was calibrated on a perfect ( kitchen Floor ) level surface. As done many times before. The FC is a level as it gets on the quad itself. And after calibrating the level attitude in Librepilot the quad still wants to fly forward, we're not even talking drift here. Hands of and it flies away forward and picks up speed. A mentioned, it has to be something else like mentioned here: wires or shielding wires or shielding the FC. The PDB of course is underneath the FC but it has flown perfect for months now. The only thing I changed ( should have mentioned it before ) is I cut all wires to and from the ESC to make them a lot shorter, also the signal cables.

The other problem I have as well since doing that is that the quad stops flying and flips on sudden throttle input or yaw input. Even if I do it gently throttle up the quad flies not straight, it flies up and to the left.

I've attached two slo mo movies of the issue. I changed motors, resoldered all ESC cables. Took another CC3D FC, Changed PDB and nothing really helps.

Then I moved ESC and motors around and the problem still persists.

See for yourself.






« Last Edit: May 21, 2016, 04:21:39 pm by Jeuke26 »

f5soh

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    • LibrePilot
Re: Quad drifts forward in attitude, shows perfect level in Librepilot
« Reply #6 on: May 21, 2016, 04:32:10 pm »
Try testing on ground, maintain firmly the frame and apply Throttle.

You should have one motor issue maybe.

Re: Quad drifts forward in attitude, shows perfect level in Librepilot
« Reply #7 on: June 18, 2016, 06:04:25 pm »
For anyone reading this with the same issue:

There are several reasons that it can drift even if the board is _perfectly_ level to the frame:
- motors are not mounted _perfectly_ vertical
- loose motor or cracked arm can also cause motor to not be perfectly vertical
- accel chip is not perfectly soldered level to the board
- some aircraft simply _do not hover level by design_.  that includes helicopters (one main rotor) and tricopters.

The answer is simple.  Use
   GCS -> Configuration -> Attitude -> Settings -> RotateVirtual
to adjust it.

If it is drifting forward, you subtract from Pitch
If it is drifting backward, you add to Pitch
If it is drifting left, you subtract from Roll
If it is drifting right, you add to Roll