Unable to stabilize Crazyflie in air.

[ellenkorsberg]

I am trying to make my Crazyflie hover in a stable position in the air, i.e. giving it enough thrust to raise it to a certain altitude and then let it hold that thrust and have pitch, roll and yaw all zero.

I control the Crazyflie through a program written in C#. So far, I have been able to thrust it up to a certain altitude and letting pitch, roll and yaw be zero. However, even though pitch, roll and yaw are all set to zero, it drifts north east relative the drone. I have tried to trim it manually by adjusting the pitch and roll slightly. Initially, the drone stabilizes with the trimmed values, but after a few seconds it starts to drift north east again.
Might it have something to do with the drones internal stabilizer?

[malintha]

I think it is possible to drift the drone as it is not perfectly balanced (worn rotors, unbalanced frame, motor frictions etc.). One way to stop the drift is providing it some external feedback about its position in the world frame using some position feedback system. An optic flow sensor would even do the job.
https://www.bitcraze.io/2017/11/optical-flow/