With Ardupirates and earlier versions of Arducopter I had a problem with gyro drift. I thought this was not a problem with the 2.0.46 version I'm running now, but I have started to notice it again when flying in windy conditions.
When holding quad against the wind in Stabilize mode, after a while the center point drifts. So when I let go of stick the quad banks hard to the opposite direction. I almost lost the quad because I was no longer able to give enough left tilt to get back, I had to turn 180 degrees and tilt the quad right to get back. When I got it back I noticed that the camera gimble was tilted almost all the way to one of the sides, even if the quad was in level flight. So I assume that there is a gyro drift issue. The quad thinks it's tilted to one of the sides even if it's not.
I have been through all the calibration sequences, holding disarm for 20s etc. The quad flies perfect in calm wind. The problem only appears when holding it against wind for some time. Sensor pads on the board is soldered.
Can this be caused by the board not having enoug vibration dampers underneath?
Replies
I think I have the solution!
Man, this is probably too stupid to be correct, but here goes!
Remember I wrote this? : " I noticed that the camera gimble was tilted almost all the way to one of the sides, even if the quad was in level flight"
In fact, this was not a symptom of the accellerators being un-leveled, it's the cause of why the quad drifts!!
I disconnected the camera gimbal so it doesn't swing from side to side, and now everything is ok. It seems that after flying for a while, the level of the camera gimbal roll is drifting, so the camera gimbal with 250gram camera is making the quad unbalanced. And this is causing the quad to drift to the side because of uneven weight distribution.
The only thing I can think of that could prove my teory wrong, is that when connecting the servos to my camera gimbal it causes the IMU to loose the idea of what "level" is. Either because of vibrations or movements from the servos, or because of the extra current drawn. Or something like that...
Can you confirm that the level of the camera roll is not tied to the the leveling of the quad itself in the code? That the camera gimble may drift while the accellerator values used to level the quad does not drift?
Thank you for your answers!
The props are probably not perfectly balanced anymore, and the foam pads under the board may be to stiff. I will do some serious vibration dampening of the board and report the results here.
Everything else is just about perfect now, amazing work, and excellent support!
Fighting wind usually causes you to give more power to the motors. That's when you can get bitten by gyro drift due to aliasing. If it happens in about 20-30 seconds, it is the accels. Balance your props and isolate the IMU as best you can.
I'm wondering if we raise the pitch and roll commands from the radio to say 60° instead of 45° we could get around it.
Jason
I'm not sure. If it was sensor aliasing from vibration, I think you would expect to see it over time even when you are not fighting against the wind. I think it is because the accelerometers alias, and correction to the gyro against their normal drift is thus affected. But I think you should see that all the time, unless there is simply more vibration only while you are fighting the wind...