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Unstable when Yaw reaches 90 Degrees

Posted: Sun Nov 01, 2020 2:11 pm
by DimChaik
Hi everyone,

I am flying crazyflies using a Vicon system. I've been using mainly the crazyflie_ros package and send position+yaw setpoints to the crazyflie over ROS.
Everything works fine, until I command the crazyflie to turn to 90 (or 270) degrees. As soon as it does that, it starts to lose its balance and becomes unstable.
I cannot understand why any such thing would happen, since I'm using a vicon system with great pose tracking, but I've tried it with two different crazyflies now and it happens with both of them.
As long as I keep them from assuming a yaw near 90 degrees, everything looks fine and they can fly around seamlessly. But upon turning to 90 degrees, it's immediate instability.
Is this a known issue? Anything I can do about this?
Thank you

Re: Unstable when Yaw reaches 90 Degrees

Posted: Mon Nov 02, 2020 10:54 am
by whoenig
Hi, which controller are you using (onboard PID, onboard Mellinger, or offboard crazyflie_ros controller)?

Re: Unstable when Yaw reaches 90 Degrees

Posted: Wed Nov 04, 2020 1:00 pm
by DimChaik
I used both the PID and the Mellinger and had the same results. But then I decided to try without the crazyflie_ros package, wrote some code to do the same things using only the crazyflie python libs and didn't get instability. I figured the only difference was that in the crazyflie libs examples I saw they were setting a new quaternion standard deviation for the Kalman filter, so I did that in crazyflie_ros too and it worked.

So long story short, I had to set the LocExtQuatStdDev parameter to something like 0.03 to achieve normal flight