Strange wobble during flight

[allynbauer]

Hi folks, my copter has been experiencing a strange wobble during flight. This occurs along the axis containing motors 1 and 3. It manifests as a quick oscillation, that flattens out within a second or so. The severity of the oscillation varies, from barely noticeable to bad enough to cause a crash. In one instance, I witnessed the oscillation develop enough to where the copter rotated past vertical. Very amusing, not super ideal.

Any thoughts on the cause for this? The copter itself is fairly balanced. I have sanded the props a bit to get them basically balanced as well. Presumably, if the issue were with the gyro, stable flight would never be possible.

Next, I will try swapping out one or both of the motors. I am thinking one of them is probably a bit weak, which starts the oscillation, and then other forces decide whether it develops into a lolzy face-plant or resumes a semblance of stability.

Has anybody else seen something like this? Any other ideas?

I will attempt to acquire video of this phenomenon this weekend.

[bhuism]

I've experienced this as well, I think the PID(?) motor control loop with the gyro's and accel's can be improved, this guy had it down I think.

[TheFrog4u]

Taking into consideration that other cf are very stable with the same pid parameter this might also be related to the accelerometer. Maybe some have another noise level than others or something like that? In this case the same pid parameteres might not be optimal for all cf, so playing around with the pid parameters might help to improve performance on individual cf. Not sure about that though.

[bhuism]

I think I should try this.

[TheFrog4u]

also make sure that your propellers are balanced! Nore info here